[ IMAGE ( above ): IBM Stratus and Cirrus supercomputers analyze Global Environmental Intelligence ( click to enlarge ) ]

Earth Event Alerts
by, Concept Activity Research Vault [ E-MAIL: ConceptActivityResearchVault@Gmail.Com ]

August 17, 2012 19:00:42 ( PST ) Updated ( Originally Published: March 23, 2011 )

MARYLAND, Fort George G. Meade - August 17, 2012 – IBM Stratus and IBM Cirrus supercomputers as well as CRAY XK6m and CRAY XT5 ( Jaguar ) massive parallel supercomputers and vector supercomputers are securely controlled via the U.S. National Security Agency ( NSA ) for analyzing Global Environmental Intelligence ( GEI ) data extracted from ground-based ( terrestrial ) monitoring stations and space-based ( extraterrestrial ) spaceborne platforms studying Earth Event ( Space Weather ) effects via High-Performance Computing ( HPC ) as well as, for:

- Weather Forecasting ( including: Space Weather );
- U.S. Government Classified Projects;
- Scientific Research;
- Design Engineering; and,
- Other Research.

[ IMAGE ( above ): CRAY XK6m supercomputers analyze Global Environmental Intelligence ( click to enlarge ) ]

CRAY INC. largest customers are U.S. government agencies, e.g. the U.S. Department of Defense ( DoD ) Defense Advanced Research Projects Agency ( DARPA ) and the U.S. Department of Energy ( DOE ) Oak Ridge National Laboratory ( ORNL ), which accounts for about 3/4 of revenue for CRAY INC. – as well as other supercomputers used worldwide by academic institutions ( universities ) and industrial companies ( private-sector firms ).

CRAY INC. additionally provides maintenance, support services and sells data storage products from partners ( e.g. BlueArc, LSI and Quantum ).

Supercomputer competitors, of CRAY INC., are:

- IBM;
- HEWLETT-PACKARD; and,
- DELL.

On May 24, 2011 CRAY INC. announced its new CRAY XK6 supercomputer, a hybrid supercomputing system combining its Gemini InterConnect, AMD Opteron™ 6200 Series processors ( code-named: InterLagos ) and NVIDIA Tesla 20 Series GPUs into a tightly integrated upgradeable supercomputing system capable of more than 50 petaflops ( i.e. ‘quadrillions of computing operations’ per ‘second’ ), a multi-purpose supercomputer designed for the next-generation of many-core High Performance Computing ( HPC ) applications.

The SWISS NATIONAL SUPERCOMPUTING CENTRE ( CSCS ) – located in Manno, Switzerland - is the CRAY INC. first ( 1st ) customer for the new CRAY XK6 system. CSCS ( Manno, Switzerland ) promotes and develops technical and scientific services in the field of High-Performance Computing ( HPC ) for the Swiss research community, and is upgrading its CRAY XE6m system ( nick-named: Piz Palu ) into a multiple cabinet new CRAY XK6 supercomputer. The SWISS NATIONAL SUPERCOMPUTING CENTRE ( CSCS ) supports scientists working, in:

- Weather Forecasting;
- Physics;
- Climatology;
- Geology;
- Astronomy;
- Mathematics;
- Computer Sciences;
- Material Sciences;
- Chemistry;
- Biology;
- Genetics; and,
- Experimental Medicine.

Data additionally analyzed by these supercomputers, include:

- Ultra-Deep Sea Volcanoes located in continental plate fracture zones several miles beneath ocean basin areas ( e.g. Asia-Pacific Rim also known as the “Pacific Ring of Fire” where a circum-Pacific seismic belt of earthquakes frequently impact areas far across the Pacific Ocean in the Americas ).

Global geoscience realizes Earth ‘ground movement shaking’ earthquakes hide alot, of what people are actually walking on-top-of, large geographic land mass areas known as ‘continental shelves’ or “continental plates” that move ( tectonics ) because of superheated pressurized extrasuperconducting magnetic energy properties released from within molten magma material violently exploding beneath the surface of the Earth down in ultra-deep seas.

[ IMAGE ( above ): Global Tectonic Plate Boundaries & Major Volcano HotSpots ( click to enlarge ) ]

Significant volcanoes are positioned like dots along this global 25,000-mile circular region known as the “Pacific Ring of Fire” extending from south of Australia up the ‘entire eastcoast’ of Japan, China and the Kamchatka Pennisula of Russia to across the Aleutian Islands of Alaska and then south down the ‘entire westcoast’ of North America and Latin America.

[ IMAGE ( above ): Ultra-Deep Sea Pacific Ocean Basin ( click to enlarge ) ]

March 11, 2011 Tohoku-chiho Taiheiyo-oki Japan 9.0 earthquake held several secrets, including U.S. government contractors simultaneously monitoring a significant ”moment of magnitude” ( Mw ) Earth Event occurring parallel to the eastcoast of Japan beneath the Western Pacific Ocean where an entire suboceanic mountain range was being split in-half ( south to north ) 310-miles long and split open 100-feet wide ( east to west ), which the public was unaware of nor were they told details about.

Interestingly, the March 11, 2011 Japan island earthquakes have not yet stopped, as the swarm of 4.0, 5.0, 6.0 and 7.0 Richter scale earthquakes continue as a direct and proximate cause of erupting ‘suboceanic volcanoes‘ moving these large “plates” beginning to force yet others to slam into one another thousands of miles away.

 

Japan’s Western Pacific Ocean ‘eastcoast’ has a ’continental plate’ slamming point meeting the ’westcoast’ of North America near the Cascade mountain range ‘plate’ reacting in one ( 1 ) of two ( 2 ) ways, i.e. ’seaward’ ( plate thrusting toward Japan ) or ‘landward’ ( plate thrusting toward the Pacific Northwest ) of the United States and/or Canada.

What The Public Never Knew

Government leadership, globally, is acutely familiar with these aforementioned types of major Earth Events, including ‘monstrous plate tectonic pushing matches’, which usually collapse one or more ‘national infrastructures’ and typically spells ‘death’ and ‘serious injuries’ for populations in developed areas.

Extremely familiar with mass public panic resulting from Earth Event catastrophes, government ‘contingency actions’ pre-approved by ‘governing bodies’ and/or ‘national leadership’ Executive Order Directives, which although not advertised is a matter of public record, ‘immediately calls’ upon ‘all military forces’ to carry-out “risk reduction” ( ‘minimization of further damages and dangers’ ) through what is referred to as “mitigation” ( ‘disaster management’ ) within “National Disaster Preparedness Planning” ( ‘national contingency measures’ ) details citizens are unaware-of. Government decision-makers know a “national emergency can bring temporary suspension of Constitutional Rights and a loss of freedoms – a volatile subject few care to discuss because ’any significant natural disaster’ will result in government infringment on many civil liberties most populations are accustomed to enjoying.

Before 1-minute and 40-seconds had passed into the March 11, 2011 Tohoku, Japan earthquake ( Richter scale: M 9.0 ), key U.S. government decision-makers discussed the major Earth Event unfolding off Japan’s eastcoast Plate-Boundary subduction zone beneath the ultra-deep sea of the Western Pacific Ocean where Japan’s monstrous volcano mountain range had split at least 100-feet wide open and cracked 310-miles long in a northern direction headed straight for the Aleutian Islands of Alaska in the United States.

U.S. Military Contingent Standby “Red Alert” Notification

U.S. Air Force ( USAF ) ‘subordinate organization’ Air and Space Operations ( ASO ) Communications Directorate ( A6 ) ‘provides support’ over ‘daily operations’, ‘contingency actions’ and ‘general’ Command, Control, Communication and Computer Intelligence ( C4I ) for the U.S. Air Force Weather Agency ( USAFWA ) saw its 1st Weather Group ( 1ST WXG ) Directorate ready its USAFWAWXGOWS 25th Operational Weather Squadron ( OWS ) at Davis-Monthan Air Force Base ( Tucson, Arizona ) responsibile for conjuntive communication notification issuance of an Earth Event “Red Alert” immediately issued directly to U.S. Army Western Command ( WESTCOM ) with a “Standby-Ready” clause pausing Western Region ( CONUS ) mobilization of Active, Reserve and National Guard military forces at specific installations based on the Japan Earth Event “moment of magnitude” ( Mw ) Plate-Boundary consequential rebound expected to strike against the North America westcoast Plate-Boundary of the Cascadia Range reactionarily triggering its subduction zone into a Cascadia ‘great earthquake’.

CALTECH Public News Suppression Of Major Earth Event

Officials, attempting to diminish any clear public understanding of the facts only knowing a Richter scale level earthquake ‘magnitude’ ( never knowing or hearing about what a major Earth Event “moment of magnitude” ( Mw ) entailed ), only served-up ‘officially-designed double-speak psycho-babble terms’ unfamiliar to the public as ‘creative attention distraction’ announcing the “Japan earthquake experienced,” a:

- “Bilateral Rupture;” and,

- “Slip Distribution.”

The facts are that, the Japan ‘earthquake’ would ‘never have occurred’, ‘unless’:

1ST – “Bilateral Rupture” ( ‘suboceanic subterranean tectonic plate split wide open  ) occurred; followed by,

2ND – “Slip Distribution” ( ‘tectonic plate movement’ ); then finally,

3RD – “Ground Shaking” ( ‘earthquake’ ) response.
 
Officials failed the public without any notification a major Earth Event “moment of magnitude” ( Mw ) on the “Pacific Ring of Fire” ( circum-Pacific seismic belt ) in the Western Pacific Ocean had a, huge:

1. Continental Plate Break Off;

3. Undersea Plate Mountain Range Crack Wide Open; plus,

2. Mountain Range Split Open 310-Miles Long.

There are some, laying at rest, that might ‘not consider’ the aforementioned three ( 3 ) major Earth Event occurences significant, except those ‘still living’ on Earth.

 

Asia-Pacific Rim

This western Pacific Ocean huge ‘undersea mountain range’ moved ‘east’, crushing into the smaller portion of its tectonic plate’ toward the continent of Asia, which commenced continous streams of day and night significant earthquakes still registering 5.0 + and 6.0 + according to Richter scale levels of magnitude now and for over 12-days throughout the area surrounding Japan, the point nearest where the tectonic plate meets the continent of Asia within the western Pacific Ocean from where this ‘monstorous undersea mountain range’ suddenly split, sending the ‘eastern half’ – with the ‘tectonic plate’ broken beneath it – slamming into the continent of Asia.

Simultaneously pushed, even greater with more force outward ( note: explosives – like from out-of a cannon or from a force-shaped explosive – project blasts outward from the ‘initial explosive blast’ is blunted by a back-stop ) away-from the Asia continent, was this ‘monstorous undersea mountain range’ split-off ( 310-miles / 500-kilometers long ) ‘western half’ slammed west up against the Americas ‘western tectonic plates’ .

This ‘is’ the ‘major’ “Earth Event” that will have consequential global impact repurcussions, ‘officially minimized’ by ‘focusing public attention’ on a ‘surface’ Earth Event earthquake 9.0 Richter scale magnitude ( once ), while even further diminishing the hundreds of significant earthquakes that are still occuring 12-days after the initial earthquake.

 Asia-Pacific Rim “Ring Of Fire”

Many are unaware the “Asia-Pacific Rim” is ( also known as ) the “Ring of Fire” whereunder the ”ultra-deep sea Pacific Ocean’ exists ‘numerous gigantic volatile volcanoes’ positioned in an ‘incredibly large circle’ ( “ring” ) around a ‘huge geographic land mass area’ comprised of ‘tectonic plates’ that ‘connect’ the ‘Eastern Asias’ to the ‘Western Americas’.

Yellowstone National Park Super Volcano

Many people are still wondering ‘why’ the Japan earthquakes have not yet stopped, and why they are being plagued by such a long swarm of siginificant earthquakes still to this very day nearly 60-days later. The multiple color video clips viewed ( below ) provides information on unusual earthquake swarm patterns and reversals while studying the World’s largest supervolcano in Wyoming ( USA ) located at Yellowstone National Park, a global public attraction viewing natural underground volcano steam vents known as geyser eruptions:

[ PHOTO ( above ): Major HotSpot at Yellowstone displays Half Dome cap of granite rock above unerupted volcano magma. ]

Ultra-Deep Sea Volcanoes

When huge undersea volcanoes erupt they dynamically force incredibly large geographic land mass plates to move whereupon simultaneously and consequentially movement is experienced on ‘surface land areas’ people know as ’earthquakes’ with their ’aftermath measurements’ provided in “Richter scale level” measurements that most do not understand. These Richter scale measurements are only ‘officially provided estimates’, as ’officials are never presented with totally accurate measurements’ because many of which are ‘not obtained with any great precision for up-to 2-years after the initial earthquake’.

Rarely are ‘precise measurements’ publicly provided, and at anytime during that 2-year interim the public may hear their previously reported earthquake Richter scale level measurement was either “officially upgraded” or “officially downgraded.” Often, this is apparently dependent when one sees ’many other countries contradicting U.S. public news announcements’ about the magnitude of a particularly controversial earthquake. An example of this was seen surrounding the March 12, 2011 earthquake in Japan:

- Japan 1st public announcement: 9.2 Richter scale;

- United States 1st public announcement: 8.9 Richter scale;

- United States 2nd public announcement: 9.0 Richter scale; and,

- United States 3rd public announcement: 9.1 Richter scale.

What will the March 12, 2011 Japan earthquake be officially reported as in 2-years? Who knows?

Never publicly announced, however are measurements of an earthquake ‘force strength pressure accumulation’ transmitted through suboceanic tectonic plates grinding against one another, a major Earth Event ‘geographic pushing process’, having been seen by U.S. NSA supercomputers from global ground and space-based monitoring analysis surrounding the “Asia-Pacific Rim Ring of Fire” – stretching from the ‘Eastern Asias’ to the ‘Western Americas’ and beyond.

This ‘domino plate tectonic principle’ results from combined amounts of ‘volcanic magmatic eruptive force strength’ and ‘tectonic plate accumulative pressure build-up’ against ‘adjacent tectonic plates’ causing ‘suboceanic, subterranean and surface land to move’ whereupon ‘how significant such amounts occur determines strength’ of both consequential ‘earthquakes’ and resultant ‘tsunamis’.

Waterway Tsunamis

When most of the public ‘hears about’ a “tsunami”, they ‘think’ ‘high waves’ near “ocean” coastal regions presented with significant floods over residents of cities nearby. Few realize the ‘vast majority of Earth’s population predominantly live all along ocean coastal regions. Few realize one ( 1 ) ‘gigantic tsunami’ could ‘kill vast populations living near oceans in the wake of popular beaches, a tough trade-off for some while logical others choose ‘living further inland’ – away from large bodies of water like ‘large lakes’ where ‘tide levels are also effected by the gravitational pull of the moon’ that can also can a ‘vast deep lake body’ bring a tsunami dependent on which direction tectonic plates move a ‘force directionalized earthquake’ creating a ‘tsunami’ with significant innundating floods over residents living in cities near those ‘large shoreline’ areas too.

What most of the public does not yet fully realize is that ‘large river bodies of water’, like the Mississippi River that is a ‘north’ to ‘south’ directional river’ could easily see ‘east to ‘west’ directional ‘tectonic plates’ move adjacent states – along the New Madrid Fault subduction zone – with significant ‘earthquakes’ – from tectonic plate movement easily capable of squeezing the side banks of even the Missippi River forcing huge amounts of water hurled out onto both ‘east’ and ‘west’ sides resulting in ‘seriously significant inland flooding’ over residents living in ‘low lying’ states of the Central Plains of the United States.

Japan “Pacific Ring Of Fire” Earthquakes To Americas Cascadia Fault Zone

Japan accounts, of a co-relative tsunami, suggest the Cascadia Fault rupture occurred from one ( 1 ) single earthquake triggering a 9-Mw Earth Event on January 26, 1700 where geological evidence obtained from a large number of coastal northern California ( USA ) up to southern Vancouver Island ( Canada ), plus historical records from Japan show the 1,100 kilometer length of the Cascadia Fault subduction zone ruptured ( split cauding that earthquake ) major Earth Event at that time. While the sizes of earlier Cascadia Fault earthquakes are unknown, some “ruptured adjacent segments” ( ‘adjacent tectonic plates’ ) within the Cascadia Fault subduction zone were created over periods of time – ranging from as little as ‘hours’ to ‘years’ – that has historically happened in Japan.

Over the past 20-years, scientific progress in understanding Cascadia Fault subduction zone behavior has been made, however only 15-years ago scientists were still debating whether ‘great earthquakes’ occured at ‘fault subduction zones’. Today, however most scientists realize ‘great earthquakes’ actually ‘do occur in fault subduction zone regions’.

Now, scientific discussions focus on subjects, of:

- Earth crust ‘structural changes’ when a “Plate Boundary” ruptures ( splits )
- Related tsunamis;
- Seismogenic zone ( tectonic plate ‘locations’ and ‘width sizes’ ).

Japan America Earthquakes And Tsunamis Exchange

Great Cascadia earthquakes generate tsunamis, which most recently was at-least a ’32-foot high tidal wave’ onto the Pacific Ocean westcoast of Washington, Oregon, and California ( northern portion of state ), and that Cascadia earthquake tsunami sent a consequential 16-foot high todal wave onto Japan.

These Cascadia Fault subduction zone earthquake tsunamis threaten coastal communities all around the Pacific Ocean “Ring of Fire” but have their greatest impact on the United States westcoast and Canada being struck within ’15-minutes’ to ’40-minutes’ shortly ‘after’ a Cascadia Fault subduction zone earthquake occurs.

Deposits, from past Cascadia Fault earthquake tsunamis, have been identified at ‘numerous coastal sites’ in California, Oregon, Washington, and even as far ‘north’ as British Columbia ( Canada ) where distribution of these deposits – based on sophisticated computer software simulations for tsunamis – indicate many coastal communities in California, Oregon, Washington, and even as far ‘north’ as British Columbia ( Canada ) are well within flooding inundation zones of past Cascadia Fault earthquake tsunamis.

California, Oregon, Washington, and even as far ‘north’ as British Columbia ( Canada ) westcoast communities are indeed threatened by future tsunamis from Cascadia great earthquake event ‘tsunami arrival times’ are dependent on measuring the distance from the ‘point of rupture’ ( tectonic plate split, causing earthquake ) – within the Cascadia Fault subduction zone – to the westcoast “landward” side.

Cascadia Earthquake Stricken Damage Zone Data

Strong ground shaking from a “moment of magnitude” ( Mw ) “9″ Plate-Boundary earthquake will last 3-minutes or ‘more’, dominated by ‘long-periods of further earthquakes’ where ‘ground shaking movement damage’ will occur as far inland as the cities of Portland, Oregon; Seattle, Washington; and Vancouver, British Columbia ( Canada ).

Tsunami Optional Wave Patterns “Following Sea”

Large cities within 62-miles to 93-miles of the nearest point of the Cascadia Plate-Boundary zone inferred rupture, will not only experience ‘significant ground shaking’ but also experience ‘extreme duration ground shaking’ lasting far longer, in-addition to far more powerful tsunamis carrying far more seawater because of their consequential “lengthened  wave periods” ( ‘lengthier distances’ between ‘wave crests’ or ‘wave curls’ ) bringing inland akin to what fisherman describe as a deadly “following sea” ( swallowing everything within an ‘even more-so powerful waterpath’ ), the result of which inland causes ‘far more significant damage’ on many ‘tall buildings’ and ‘lengthy structures’ where ‘earthquake magnitude strength’ will be felt ‘strongest’ – all along the United States of America Pacific Ocean westcoast regional areas – experiencing ‘far more significant damage’.Data Assessments Of Reoccuring Cascadia Earthquakes

cascadia ‘great earthquakes’ “mean recurrence interval” ( ‘time period occuring between one earthquake with the next earthquake ) – specific ‘at the point’ of the Cascadia Plate-Boundary – time is between 500-years up-to 600-years, however Cascadia Fault earthquakes in the past have occurred well within the 300-year interval of even less time since the Cascadia ‘great earthquake’ of the 1700s. Time intervals, however between ‘successive great earthquakes’ only a few centuries up-to 1,000 years has little ‘well-measured data’ as to ‘reoccurance interval’ because the numbers of recorded Cascadia earthquakes have rarely measured over ‘five’ ( 5 ). Data additionally indicates Cascadia earthquake intermittancy with irregular intervals when they did occur, plus data lacks ‘random distribution’ ( ‘tectonic plate shift’ or ‘earth movement’ ) or ‘cluster’ of these Cascadia earthquakes over a lengthier period of time so ‘more accurate assessments are unavailable’ for knowning anything more about them. Hence, because Cascadia earthquake ‘recurrence pattern’ is so ‘poorly known’, knowing probabilities of the next Cascadia earthquake occurrence is unfortunately unclear with extremely sparse ‘interval information’ details.

Cascadia Plate-Boundary “Locked” And “Not Locked”

Cascadia Plate-Boundary zone is ‘currently locked’ off the U.S. westcoast shoreline where it has accumulating plate tectonic pressure build-up – from other tectonic plates crashing into it for over 300-years.

The Cascadia Fault subduction zone, at its widest point, is located northwest just off the coast of the State of Washington where the maximum area of seismogenic rupture is approximately 1,100 kilometers long and 50 kilometers up-to 150 kilometers wide. Cascadia Plate-Boundary seismogenic portion location and size data is key-critical for determining earthquake magnitude, tsunami size, and the strength of ground shaking.

Cascadia Plate-Boundary “landward limit” – of only its “locked” portion – where ‘no tectonic plate shift has yet to occur’ is located between the Juan de Fuca tectonic plate and North America tectonic plate were it came to be “locked” between Cascadia earthquakes, however this “ocked” notion has only been delineated from ‘geodetic measurements’ of ‘surface land deformation’ observations. Unfortunately, its “seaward limit” has ‘very few constraints’ up-to ‘no constraints’ for travelling – on its so-called “locked zone” portion – that could certainly move at any time.

Cascadia Plate Continues Sliding

Cascadia transition zone, separating its “locked zone” from its “continuous sliding zone” headed east into the continent of North America, is constrained ( held-back ) poorly so, Cascadia rupture may extend an unknown distance – from its now “locked zone” to its “continously sliding transition zone.”

On some Earth crust faults, near coastal regions, earthquakes may also experience ‘additional Plate-Boundary earthquakes’, ‘increased tsunami tidal wave size’ plus ‘intensification of local area ground shaking’.

Earth Event Mitigation Forces Global Money Flow

Primary ‘government purpose’ to ‘establishing international’ “risk reduction” is solely to ‘minimize global costs from damages’ associated with major magnitude Earth Events similar-to but even-greater than the what happend on March 11, 2011 all over Japan.

Historical earthquake damages assist in predictive projections of damage loss studies suggesting disastrous future losses will occur in the Pacific Northwest from a Cascadia Fault subduction ‘great earthquake’. National ‘loss mitigation efforts’ – studying ‘other seismically active regions’ plus ‘national cost-benefit studies’ indicate that ‘earthquake damage loss mitigation’ may effectively ‘reduce losses’ and ‘assist recovery’ efforts in the future. Accurate data acquired, geological and geophysical research and immediate ‘technological information transfer’ to ‘national key decision-makers’ was to reduce Pacific Northwest Cascadia Fault subduction zone additional risks to those of the Western North America coastal region.

Damage, injuries, and loss of life from the next great earthquake from the Cascadia Fault subduction zone will indeed be ‘great’, ‘widespread’ and ‘significantly ‘impact national economies’ ( Canada and United States ) for years to decades in the future, which has seen a global concerted increase, in:

- International Cooperative Research;
- International Information Exchanges;
- International Disaster Prepardeness;
- International Damage Loss Mitigation Planning;
- International Technology Applications; and,
- More.

Tectonics Observatory

CALTECH Advanced Rapid Imaging and Analysis ( ARIA ) Project collaborative members of the NASA Jet Propulsion Laboratory ( JPL ), University of California Institute of Technology ( Pasadena ) Tectonics Observatory ARIA Project members, CALTECH scientists, Shengji Wei and Anthony Sladen ( of GEOAZUR ) modelled the Japan Tohoku earthquake fault zone sub-surface ( below surface ) ‘tectonic plate movement’, dervived from:

- TeleSeismic Body Waves ( long-distance observations ); and,

- Global Positioning Satellites ( GPS ) ( near-source observations ).

A 3D image of the fault moving, can be viewed in Google Earth ( internet website webpage link to that KML file is found in the “References” at the bottom of this report ) projects that fault rupture in three dimensional images, which can be viewed from any point of reference, with ‘that analysis’ depicting the rupture ( ground splitting open 100-feet ) resulting in the earthquake ( itself ) ‘triggered from 15-miles ( 24-kilometers ) beneath the ultra-deep sea of the Western Pacific Ocean, with the ‘entire island of Japan being moved east’ by 16-feet ( 5 meters ) from its ‘before earthquake location’.

[ IMAGE ( above ): NASA JPL Project ARIA Tectonic Plate Seismic Wave Direction Map ( click image to enlarge and read ) ]

National Aeronautics and Space Administration ( NASA ) Jet Propulsion Laboratory ( JPL ) at the University of California ( Pasadena ) Institute of Technology ( also known as ) CALTECH Project Advanced Rapid Imaging and Analysis ( ARIA ) used GEONET RINEX data with JPL GIPSY-OASIS software to obtain kinematic “precise point positioning solutions” from a bias fixing method of a ‘single station’ matched-up to JPL orbit and clock products to produce their seismic displacement projection map details that have an inherent ’95% error-rating’ that is even an ‘estimate’, which ‘proves’ these U.S. government organization claims that ‘all they supposedly know’ ( after spending billions of dollars ) are what they are ‘only willing to publicly provide may be ‘only 5% accurate’. So much for what these U.S. government organizations ‘publicly announce’ as their “precise point positioning solutions.”

Pay Any Price?

More ‘double-speak’ and ‘psycho-babble’ serves to ‘only distract the public away from the ‘truth’ as to ‘precisely what’ U.S. taxpayer dollars are ‘actually producing’, and ‘now knowing this’ if ‘those same officials’ ever ‘worked for a small business’ they would either be ‘arrested’ for ‘fraud’ or ‘fired’ because of ‘incompetence’, however since ‘none of them’ will ever ‘admit to their own incometence’ their ‘leadership’ needs to see ‘those responsible’ virtually ‘swing from’ the end of an ‘incredibly long U.S. Department of Justice rope’.

Unfortunately, the facts surrounding all this only get worse.

[ IMAGE ( above ): Tectonic Plates ( brown color ) Sinking and Sunk On Earth Core. ]

Earthquake Prediction Falacy

Earthquake prediction will ‘never be an accomplished finite science for people to ever rely upon’, even though huge amounts of money are being wasted on ‘technology’ for ‘detection sensors’ reading “Seismic Waveforms” ( also known as ) “S Waves” that ‘can be detected and stored in computer databases’, because of a significant fact that will never be learned no matter how much money or time may be devoted to trying to solve the unsolvable problem of the Earth’s sub-crustal regions that consist primarily of ‘molten lake regions’ filled with ‘floating tectonic plates’ that are ‘moving while sinking’ that ‘cannot be tested’ for ‘rock density’ or ‘accumulated pressures’ existing ‘far beneath’ the ‘land surface tectonic plates’.

The very best, and all, that technology can ever perform for the public is to record ‘surface tectonic plates grinding aganist one another’ where ‘only that action’ ( alone ) does in-fact emit the generation of upward ‘accoustic wave form patterns’ named as being ‘seismic waves’ or ‘s-waves’ that ‘do occur’ but ‘only when tectonic plates are moving’.

While a ‘public early warning’ might be helpful for curtailing ‘vehicular traffic’ crossing an ‘interstate bridge’ that might collapse or ‘train traffic’ travel being stopped, thousands of people’s lives could be saved but it would fail to serve millions more living in buildings that collapse.

Early Warning Exclusivity

Knowing governments, using publicly unfamiliar terms, have ‘statisticly analyzed’ “international economics” related to “national infrastructure preparedness” ( ‘early warning systems’ ) – both “public” ( i.e. ‘utility companies’ via ‘government’ with ‘industrial leadership’ meetings ) and “private” ( i.e. ‘residents’ via ‘television’, ‘radio’, ‘newspaper’ and ‘internet’ only ‘commercial advertisements’ ) between which two ( 2 ) sees “national disaster mitigation” ‘primary designated provisions’ for “high density population centers” near “coastal or low-lying regions” ( ‘large bodies of ocean, lake and river water’ ) “early warning” but for only one ( 1 ) being “public” ( i.e. ‘utility companies’ via ‘government’ with ‘industrial leadership’ meetings ) “in the interest of national security” limiting ‘national economic burdens’ from any significant Earth Event impact ‘aftermath’.

In short, and without all the governmentese ‘psycho-babble’ and double-speak’, costs continue being spent on ‘high technology’ efforts to ‘perfect’ a “seismic early warning” for the “exclusive use” ( ‘national government control’ ) that “provides” ( ‘control over’ ) “all major utility company distribution points” ( facilities from where ‘electrical power is only generated’ ) able to “interrupt power” ( ‘stop the flow of electricity nationwide’ from ‘distribution stations’ ), thus “saving additional lives” from “disasterous other problems” ( ‘aftermath loss of lives and injuries’ caused by ‘nuclear fallout radiation’, ‘exploding electrical transformers’, and ‘fires associated with overloaded electrical circuits’ ).

Logically, ‘much’ – but ‘not all’ – of the aforementioned ‘makes perfect sense’, except for “John Doe” or “Jane Doe” ‘exemplified anonomously’ ( herein ) as individuals whom if ‘earlier warned’ could have ‘stopped their vehicle ‘before crossing the bridge that collapsed’ or simply ‘stepped out of the way of a huge sign falling on them’ being ‘killed’ or ‘maimed’, however one might additionally consider ‘how many more would ‘otherwise be killed or maimed’ after an ‘ensuing mass public mob panics’ by ‘receiving’ an “early warning.” Tough call for many, but few.

Earth Data Publicly Minimized

Tohoku-oki earthquake ‘seismic wave form data’ showing the Japan eastcoast tectonic plate “bilaterally ruptured” ( split in-half for a distance of over 310-miles ) was obtained from the USArray seismic stations ( United States ) was analyzed and later modelled by Caltech scientists Lingsen Meng and Jean-Paul Ampuero whom created preliminary data animation demonstrating a ‘super major’ Earth Event simultaneously occurring when the ‘major’ earthquake struck Japan.

U.S. National Security Stations Technology Systems Projects

United States Seismic Array ( USArray ) Data Management Plan Earthscope is composed of three ( 3 ) Projects:

1. Incorporated Research Institutions for Seismology ( IRIS ), a National Science Foundation ( NSF ) consortium of universities, Data Management Center ( DMC ) is ‘managed’ by the “United States Seismic Array ( USArray )” Project;

2. UNAVCO INC. ‘implemented’ “Plate-Boundary Observatory ( PBO )” Project; and,

3. U.S. Geological Service ( USGS ) ‘operated’ “San Andreas Fault Observatory at Depth ( SAFOD )” Project at Stanford University ( California ).

Simultaneous Earth Data Management

USArray component “Earthscope” data management plan is held by USArray IRIS DMC.

USArray consists of four ( 4 ) data generating components:

Permanent Network

Advanced National Seismic System ( ANSS ) BackBone ( BB ) is a joint effort – between IRIS, USArray and USGS – to establish a ‘Permanent Network’ of approximately one-hundred ( 100 ) Earth monitoring ‘receiving stations’ ( alone ) located in the Continental United States ( CONUS ) or lowere 48 states of America, in-addition to ‘other stations’ located in the State of Alaska ( alone ).

Earth Data Multiple Other Monitors

USArray data contribution to the Advanced National Seismic System ( ANSS ) BackBone ( BB ) consists, of:

Nine ( 9 ) new ‘international Earth data accumulation receiving stations’ akin to the Global Seismic Network ( GSN );

Four ( 4 ) “cooperative other stations” from “Southern Methodist University” and “AFTAC”;

Twenty-six ( 26 ) ‘other receiving stations’ from the Advanced National Seismic System ( ANSS ) with ‘upgrade funding’ taken out-of the USArray Project “EarthScope;” plus,

Sixty ( 60 ) additional stations of the Advanced National Seismic System ( ANSS ) BackBone ( BB ) network that ‘currently exist’, ‘will be installed’ or ‘will be upgraded so that ‘data channel stream feeds’ can and ‘will be made seamlessly available’ through IRIS DMC where ‘data can be continuously recorded’ at forty ( 40 ) samples per second and where 1 sample per second can and ‘will be continously transmitted in real-time back into IRIS DMC where quality assurance is held at facilities located in ‘both’ Albuquerque, New Mexico and Golden, Colorado with ‘some’ U.S. Geological Survey ( USGS ) handling ‘some operational responsiblities’ thereof.

Albuquerque Seismological Laboratory ( ASL ) -

Albuquerque Seismological Laboratory ( ASL ) supports operation and maintenance of seismic networks for the U.S. Geological Survey ( USGS ) portion of the Global Seismographic Network ( GSN ) and Advanced National Seismic System ( ANSS ) Backbone network.

ASL runs the Advanced National Seismic System ( ANSS ) depot facility supporting the Advanced National Seismic System ( ANSS ) networks.

ASL also maintains the PASSCAL Instrument Center ( PIC ) facility at the University of New Mexico Tech ( Socorro, New Mexico ) developing, testing, and evaluating seismology monitoring and recording equipment.

Albuquerque Seismological Laboratory ( ASL ) staff are based in ‘both’ Albuquerque, New Mexico and Golden, Colorado.

Top-Down Bottom-Up Data Building Slows Earthquake Notifications

Seismic waveform ( ‘seismic Wave form frequency’ ) data is received by the Global Seismic Network ( GSN ) and Advanced National Seismic System ( ANSS ) BackBone ( BB ) network by electronic transmissions sent ‘slower than real-time’ by sending only ‘near-time data’ ( e.g. tape and compact disc recordings ) to the National Earthquake Information Center ( NEIC ) ‘station’ of the U.S. Geological Survey ( USGS ) ‘officially heralded’ for so-called “rapid earthquake response,”

Unbelieveably is the fact that in-addition to the aforementioned ‘slow Earth Event data delivery process’, an additional number of ‘data receiving stations’ have absolutely ‘no data streaming telemetry’ transmission capabilities whatsoever so, those station data recordings – on ‘tapes’ and ‘compact discs’ – are delivered by ‘other even more time consuming routes’ before that data can even reach the U.S. Geological Survey ( USGS ). In short, all the huge amounts of money being spent goes to ‘increasing computer technologies, sensors, satellites, ‘data stream channel networks’ and ‘secure facility building stations’ from the ‘top, down’ instead of building ‘monitoring stations’ and ‘recording stations’ from the ‘bottom, up’ until the entire earthquake monitoring and notification system is finally built properly. As it curreently stands, the ‘apple cart stations continue being built more and more’ while ‘apple tree stations are not receiving the proper technological nutrients’ to ‘delivery apples ( ‘data’ ) and ‘fed into notification markets’ ( ‘public’ ) where all this could do some good.

U.S. National Security Reviews Delay Already Slow Earthquake Notifications

IRIS Data Management Center ( DMC ) – after processing all incoming data streams from reporting stations around the world – then distributes seismic waveform data ‘back to’ both the Global Seismic Network ( GSN ) and Advanced National Seismic System ( ANSS ) BackBone ( BB ) network operations, but only ‘after seismic waveform data has been ‘thoroughly screened’ by what U.S. national security government Project leadership has deemed its ‘need to control all data’ by “limiting requirements” ( ‘red tape’ ) because ‘all data must undergo’ a long ardous ‘secure data clearing process’ before any data can be released’. Amusingly to some, the U.S. government – in its race to create another ‘official acronym’ of ‘double-speak’ – that national security requirement clearing process’ was ever so aptly named:

“Quality Assurance Framework” ( QUACK )

Enough said.

Let the public decide what to do with ‘those irresponsible officials’, afterall ‘only mass public lives’ are ‘swinging in the breeze’ at the very end-of a now-currently endless ‘dissinformation service rope’ being paid for by the tax-paying public.

In the meantime, while we are all ‘waiting for another Earth Event to take place far beyond, what ( besides this report ) might ‘slap the official horse’, spurring it to move quickly?

How about us? What shhould we do? Perhaps, brushing-up on a little basic knowledge might help.

Inner Earth Deeper Structure Deep Focus Earthquakes Rays And Related Anomalies

There is no substitute for knowledge, seeing information technology ( IT ) at the focal point of many new discoveries aided by supercomputing, modelling and analytics, but common sense does pretty good.

The following information, although an incredibily brief overview on such a wide variety of information topics surrounding a great deal of the in’s and out’s surrounding planet Earth, scratches more than just the surface but deep structure and deep focus impacting a multitude of generations from as far back as 700 years before the birth of Christ ( B.C. ).

Clearly referenced “Encyclopaedia Britannica” general public access information is all second-hand observations of records from other worldwide information collection sources, such as:

- Archives ( e.g. governments, institutions, public and private );

- Symposiums ( e.g. white papers );

- Journals ( professional and technical publications );

- Other information collection sources; and,

- Other information publications.

Encyclopaedias, available in a wide variety of styles and formats, are ’portable catalogs containing a large amount of basic information on a wide variety of topics’ available worldwide to billions of people for increasing their knowledge.

Encyclopedia information formats vary, and through ’volume reading’, within:

- Paper ‘books’ with either ’printed ink’ ( sighted ) or ’embossed dots’ ( Braille );

- Plastic ‘tape cartridges’ ( ‘electromagnetic’ media ) or ‘compact discs’ ( ‘optical’ media ) with ‘electronic device display’; or,

- Electron ‘internet’ ( ‘signal computing’ via ‘satellite’ or ‘telecomputing’ via ’landline’ or ‘node’ networking ) with ‘electronic device display’.

After thoroughly reviewing the Encyclopedia Britannica ‘specific compilation’, independent review found reasonable a facsimile of the original reformatted for easier public comprehension ( reproduced further below ).

Suprisingly, after that Encyclopedia Britannica ‘specific compilation’ information was reformatted for clearer reading comprehension, otherwise inner Earth ‘deep-structure’ geophysical studies formed an amazing correlation with additional factual activities within an equally amazing date chronology of man-made nuclear fracturing reformations of Earth geology geophysical – activities documented worldwide more than 1/2 century ago but somehow forgotten; either by chance or secret circumstance.

How could the Encyclopedia Britannica, or for that matter anyone else, missed something on such a grand scale that is now so obvious?

… [ TEMPORARILY EDITED-OUT FOR REVISION PURPOSES ONLY -  ] …

For more details, about the aforementioned, Click: Here!

Or,

To understand how all this relates, ‘begin with a better basic understanding’ by continuing to read the researched information ( below ):

====

Circa: March 21, 2012

Source:  Encyclopaedia Britannica

Earthquakes

Definition, Earthquake: Sudden shaking of Earth ground caused by passage of seismic waves through Earth rocks.

Seismic waves are produced when some form of energy stored in the Earth’s crust is suddenly released, usually when masses of rock straining against one another suddenly fracture and “slip.” Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another. Major fault lines of the world are located at the fringes of the huge tectonic plates that make up the Earth’s crust. ( see table of major earthquakes further below )

By the early 20th Century ( 1900s ), little was understood about earthquakes until the emergence of seismology, involving scientific study of all aspects of earthquakes, now yielding answers to long-standing questions as to why and how earthquakes occur.

About 50,000 earthquakes, large enough to be noticed without the aid of instruments, occur every year over the entire Earth, and of these approximately one-hundred ( 100 ) are of sufficient size to produce substantial damage if their centers are near human habitation.

Very great earthquakes, occur on average about once a year, however over centuries these earthquakes have been responsible for millions of human life deaths and an incalculable amount of property damage.

Earthquakes A -Z

Earth’s major earthquakes occur primarily in belts coinciding with tectonic plate margins, apparent since early ( 700 B.C. ) experienced earthquake catalogs, and now more readily discernible by modern seismicity maps instrumentally depicting determined earthquake epicentres.

Most important, is the earthquake Circum-Pacific Belt affecting many populated coastal regions around the Pacific Ocean, namely:

- South America;

- North America & Alaska;

- Aleutian Islands;

- Japan;

- New Zealand; and,

- New Guinea.

80% of the energy, estimated presently released in earthquakes, comes from those whose epicentres are in the Circum-Pacific Belt belt.

Seismic activity is by no means uniform throughout the belt, and there are a number of branches at various points. Because at many places the Circum-Pacific Belt is associated with volcanic activity, it has been popularly dubbed the “Pacific Ring of Fire.”

A second ( 2nd ) belt, known as the Alpide Belt, passes through the Mediterranean region eastward through Asia and joining the Circum-Pacific Belt in the East Indies where energy released in earthquakes from the Alpide Belt is about 15%of the world total.

There are also seismic activity ‘striking connected belts’, primarily along oceanic ridges including, those in the:

- Arctic Ocean;

- Atlantic Ocean;

- Indian Ocean ( western ); and along,

- East Africa rift valleys.

This global seismicity distribution is best understood in terms of its plate tectonic setting.

Forces

Earthquakes are caused by sudden releases of energy within a limited region of Earth rocks, and apparent pressure energy can be released, by:

- Elastic strain;

- Gravity;

- Chemical Reactions; and / or,

- Massive rock body motion.

Of all these, release of elastic rock strain is most important because this form of energy is the only kind that can be stored in sufficient quantities within the Earth to produce major ground disturbances.

Earthquakes, associated with this type of energy release, are called: Tectonic Earthquakes.

Tectonics

Tectonic plate earthquakes are explained by the so-called elastic rebound theory, formulated by the American geologist Harry Fielding Reid after the San Andreas Fault ruptured in 1906, generating the great San Francisco earthquake.

According to Reid theory of elastic rebound, a tectonic earthquake occurs when energy strains in rock masses have accumulated ( built-up ) to a point where resulting stresses exceed the strength of the rocks where then sudden fracturing results.

Fractures propagate ( travel ) rapidly ( see speeds further below ) through the rock, usually tending in the same direction and sometimes extending many kilometres along a local zone of weakness.

In 1906, for instance, the San Andreas Fault slipped along a plane 270-miles ( 430 kilometers) long, a line alongwhich ground was displaced horizontally as much as 20-feet ( 6 meters ).

As a fault rupture progresses along or up the fault, rock masses are flung in opposite directions, and thus spring back to a position where there is less strain.

At any one point this movement may take place not at-once but rather in irregular steps where these sudden slowings and restartings give rise to vibrations that propagate as seismic waves.

Such irregular properties of fault rupture are now included in ‘physical modeling” and ‘mathematical modeling’ earthquake sources.

Earthquake Focus ( Foci )

Roughnesses along the fault are referred to as asperities, and places where the rupture slows or stops are said to be fault barriers. Fault rupture starts at the earthquake focus ( foci ), a spot that ( in many cases ) is close to being from 5 kilometers to 15 kilometers ‘under the surface where the rupture propagates ( travels )’ in one ( 1 ) or both directions over the fault plane until stopped ( or slowed ) at a barrier ( boundary ).

Sometimes, instead of being stopped at the barrier, the fault rupture recommences on the far side; at other times the stresses in the rocks break the barrier, and the rupture continues.

 Earthquakes have different properties depending on the type of fault slip that causes them.

The usual ‘fault model’ has a “strike” ( i.e., direction, from north, taken by a horizontal line in the fault plane ) and a “dip” ( i.e. angle from the horizontal shown by the steepest slope in the fault ).

Movement parallel to the dip is called dip-slip faulting.

In dip-slip faults, if the hanging-wall block moves downward relative to the footwall block, it is called “normal” faulting; the opposite motion, with the hanging wall moving upward relative to the footwall, produces reverse or thrust faulting. The lower wall ( of an inclined fault ) is the ‘footwall’, and laying over the footwall is the hanging wall.

When rock masses slip past each other ( parallel to the strike area ) movement is known as strike-slip faulting.

Strike-slip faults are right lateral or left lateral, depending on whether the block on the opposite side of the fault from an observer has moved to the right or left.

All known faults are assumed to have been the seat of one or more earthquakes in the past, though tectonic movements along faults are often slow, and most geologically ancient faults are now a-seismic ( i.e., they no longer cause earthquakes ).

Actual faulting, associated with an earthquake, may be complex and often unclear whether in one ( 1 ) particular earthquake, where total energy, is being issued from a single ( 1 ) fault plane.

Observed geologic faults sometimes show relative displacements on the order of hundreds of kilometres over geologic time, whereas the sudden slip offsets that produce seismic waves may range from only several centimetres to tens of metres.

During the 1976 Tangshan earthquake ( for example ), a surface strike-slip of about 1 meter was observed along the causative fault east of Beijing, China, and later ( as another example ) during the 1999 Taiwan earthquake the Chelung-pu fault slipped vertically up to 8 meters.

Volcanism & Earthquake Movement

A separate type of earthquake is associated with volcano activity known as a volcanic earthquake.

Although likely, even in such cases, disturbance is officially believed resultant from sudden slip of rock masses adjacent a volcano being consequential release of elastic rock strain energy, however stored energy may be partially of hydrodynamic origin due heat provided by magma flowing movements ( tidal ) throughout underground reservoirs beneath volcanoes or releasing under pressure gas, but then there certainly is a clear corresponding distinction between geographic distribution of volcanoes and major earthquakes particularly within the Circum-Pacific Belt traversing ocean ridges.

Volcano vents, however, are generally several hundred kilometres from epicentres of most ‘major shallow earthquakes’, and it is believed ’many earthquake sources’ occur ‘nowhere near active volcanoes’.

Even in cases where earthquake focus occurs where structures are marked ’directly below volcanic vents’, officially there is probably no immediate causal connection between the two ( 2 ) activities where likely both may be resultant on same tectonic processes.

Earth Fracturing

Artificially Created Inductions

Earthquakes are sometimes caused by human activities, including:

- Nuclear Explosion ( large megaton yield ) detonations underground;

- Oil & Gas wells ( deep Earth fluid injections )

- Mining ( deep Earth excavations );

- Reservoirs ( deep Earth voids filled with incredibly heavy large bodies of water ).

 In the case of deep mining, the removal of rock produces changes in the strain around the tunnels.

Slip on adjacent, preexisting faults or outward shattering of rock into where new cavities may occur.

In fluid injection, the slip is thought to be induced by premature release of elastic rock strain, as in the case of tectonic earthquakes after fault surfaces are lubricated by the liquid.

Large underground nuclear explosions have been known to produce slip on already strained faults in the vicinity of test devices.

Reservoir Induction

Of the various earthquake causing activities cited above, the filling of large reservoirs ( see China ) being most prominent.

More than 20 significant cases have been documented in which local seismicity has increased following the impounding of water behind high dams. Often, causality cannot be substantiated, because no data exists to allow comparison of earthquake occurrence before and after the reservoir was filled.

Reservoir-induction effects are most marked for reservoirs exceeding 100 metres ( 330 feet ) in depth and 1 cubic km ( 0.24 cubic mile ) in volume. Three ( 3 ) sites where such connections have very probably occurred, are the:

- Hoover Dam in the United States;

- Aswan High Dam in Egypt; and.

- Kariba Dam on the border between Zimbabwe and Zambia in Africa.

The most generally accepted explanation for earthquake occurrence in such cases assumes that rocks near the reservoir are already strained from regional tectonic forces to a point where nearby faults are almost ready to slip. Water in the reservoir adds a pressure perturbation that triggers the fault rupture. The pressure effect is perhaps enhanced by the fact that the rocks along the fault have lower strength because of increased water-pore pressure. These factors notwithstanding, the filling of most large reservoirs has not produced earthquakes large enough to be a hazard.

Specific seismic source mechanisms associated with reservoir induction have been established in a few cases. For the main shock at the Koyna Dam and Reservoir in India ( 1967 ), the evidence favours strike-slip faulting motion. At both the Kremasta Dam in Greece ( 1965 ) and the Kariba Dam in Zimbabwe-Zambia ( 1961 ), the generating mechanism was dip-slip on normal faults.

By contrast, thrust mechanisms have been determined for sources of earthquakes at the lake behind Nurek Dam in Tajikistan. More than 1,800 earthquakes occurred during the first 9-years after water was impounded in this 317 meter deep reservoir in 1972, a rate amounting to four ( 4 ) times the average number of shocks in the region prior to filling.

Nuclear Explosion Measurement Seismology Instruments

By 1958 representatives from several countries, including the United States and the Russia Soviet Union government, met to discuss the technical basis for a nuclear test-ban treaty where amongst matters considered was feasibility of developing effective means to detect underground nuclear explosions and to distinguish them seismically from earthquakes.

After that conference, much special research was directed to seismology, leading to major advances in seismic signal detection and analysis.

Recent seismological work on treaty verification has involved using high-resolution seismographs in a worldwide network, estimating the yield of explosions, studying wave attenuation in the Earth, determining wave amplitude and frequency spectra discriminants, and applying seismic arrays. The findings of such research have shown that underground nuclear explosions, compared with natural earthquakes, usually generate seismic waves through the body of the Earth that are of much larger amplitude than the surface waves. This telltale difference along with other types of seismic evidence suggest that an international monitoring network of two-hundred and seventy ( 270 ) seismographic stations could detect and locate all seismic events over the globe of magnitude 4.0 and above ( corresponding to an explosive yield of about 100 tons of TNT ).

Earthquake Effects

Earthquakes have varied effects, including changes in geologic features, damage to man-made structures, and impact on human and animal life. Most of these effects occur on solid ground, but, since most earthquake foci are actually located under the ocean bottom, severe effects are often observed along the margins of oceans.

Surface Phenomena

Earthquakes often cause dramatic geomorphological changes, including ground movements – either vertical or horizontal – along geologic fault traces; rising, dropping, and tilting of the ground surface; changes in the flow of groundwater; liquefaction of sandy ground; landslides; and mudflows. The investigation of topographic changes is aided by geodetic measurements, which are made systematically in a number of countries seriously affected by earthquakes.

Earthquakes can do significant damage to buildings, bridges, pipelines, railways, embankments, and other structures. The type and extent of damage inflicted are related to the strength of the ground motions and to the behaviour of the foundation soils. In the most intensely damaged region, called the meizoseismal area, the effects of a severe earthquake are usually complicated and depend on the topography and the nature of the surface materials. They are often more severe on soft alluvium and unconsolidated sediments than on hard rock. At distances of more than 100 km (60 miles) from the source, the main damage is caused by seismic waves traveling along the surface. In mines there is frequently little damage below depths of a few hundred metres even though the ground surface immediately above is considerably affected.

Earthquakes are frequently associated with reports of distinctive sounds and lights. The sounds are generally low-pitched and have been likened to the noise of an underground train passing through a station. The occurrence of such sounds is consistent with the passage of high-frequency seismic waves through the ground. Occasionally, luminous flashes, streamers, and bright balls have been reported in the night sky during earthquakes. These lights have been attributed to electric induction in the air along the earthquake source.

Tsunamis

Following certain earthquakes, very long-wavelength water waves in oceans or seas sweep inshore. More properly called seismic sea waves or tsunamis ( tsunami is a Japanese word for “harbour wave” ), they are commonly referred to as tidal waves, although the attractions of the Moon and Sun play no role in their formation. They sometimes come ashore to great heights—tens of metres above mean tide level—and may be extremely destructive.

The usual immediate cause of a tsunami is sudden displacement in a seabed sufficient to cause the sudden raising or lowering of a large body of water. This deformation may be the fault source of an earthquake, or it may be a submarine landslide arising from an earthquake.

Large volcanic eruptions along shorelines, such as those of Thera (c. 1580 bc) and Krakatoa (ad 1883), have also produced notable tsunamis. The most destructive tsunami ever recorded occurred on December 26, 2004, after an earthquake displaced the seabed off the coast of Sumatra, Indonesia. More than 200,000 people were killed by a series of waves that flooded coasts from Indonesia to Sri Lanka and even washed ashore on the Horn of Africa.

Following the initial disturbance to the sea surface, water waves spread in all directions. Their speed of travel in deep water is given by the formula (√gh), where h is the sea depth and g is the acceleration of gravity.

This speed may be considerable—100 metres per second ( 225 miles per hour ) when h is 1,000 metres ( 3,300 feet ). However, the amplitude ( i.e., the height of disturbance ) at the water surface does not exceed a few metres in deep water, and the principal wavelength may be on the order of hundreds of kilometres; correspondingly, the principal wave period—that is, the time interval between arrival of successive crests—may be on the order of tens of minutes. Because of these features, tsunami waves are not noticed by ships far out at sea.

When tsunamis approach shallow water, however, the wave amplitude increases. The waves may occasionally reach a height of 20 to 30 metres above mean sea level in U- and V-shaped harbours and inlets. They characteristically do a great deal of damage in low-lying ground around such inlets. Frequently, the wave front in the inlet is nearly vertical, as in a tidal bore, and the speed of onrush may be on the order of 10 metres per second. In some cases there are several great waves separated by intervals of several minutes or more. The first of these waves is often preceded by an extraordinary recession of water from the shore, which may commence several minutes or even half an hour beforehand.

Organizations, notably inJapan,Siberia,Alaska, andHawaii, have been set up to provide tsunami warnings. A key development is the Seismic Sea Wave Warning System, an internationally supported system designed to reduce loss of life in thePacific Ocean. Centred inHonolulu, it issues alerts based on reports of earthquakes from circum-Pacific seismographic stations.

Seiches

Seiches are rhythmic motions of water in nearly landlocked bays or lakes that are sometimes induced by earthquakes and tsunamis. Oscillations of this sort may last for hours or even for 1-day or 2-days.

The great Lisbon earthquake of 1755 caused the waters of canals and lakes in regions as far away as Scotland and Sweden to go into observable oscillations. Seiche surges in lakes in Texas, in the southwestern United States, commenced between 30 and 40 minutes after the 1964 Alaska earthquake, produced by seismic surface waves passing through the area.

A related effect is the result of seismic waves from an earthquake passing through the seawater following their refraction through the seafloor. The speed of these waves is about 1.5 km (0.9 mile) per second, the speed of sound in water. If such waves meet a ship with sufficient intensity, they give the impression that the ship has struck a submerged object. This phenomenon is called a seaquake.

Earthquake Intensity and Magnitude Scales

 The violence of seismic shaking varies considerably over a single affected area. Because the entire range of observed effects is not capable of simple quantitative definition, the strength of the shaking is commonly estimated by reference to intensity scales that describe the effects in qualitative terms. Intensity scales date from the late 19th and early 20th centuries, before seismographs capable of accurate measurement of ground motion were developed. Since that time, the divisions in these scales have been associated with measurable accelerations of the local ground shaking. Intensity depends, however, in a complicated way not only on ground accelerations but also on the periods and other features of seismic waves, the distance of the measuring point from the source, and the local geologic structure. Furthermore, earthquake intensity, or strength, is distinct from earthquake magnitude, which is a measure of the amplitude, or size, of seismic waves as specified by a seismograph reading ( see below Earthquake magnitude )

A number of different intensity scales have been set up during the past century and applied to both current and ancient destructive earthquakes. For many years the most widely used was a 10-point scale devised in 1878 by Michele Stefano de Rossi and Franƈois-Alphonse Forel. The scale now generally employed in North America is the Mercalli scale, as modified by Harry O. Wood and Frank Neumann in 1931, in which intensity is considered to be more suitably graded.

A 12-point abridged form of the modified Mercalli scale is provided below. Modified Mercalli intensity VIII is roughly correlated with peak accelerations of about one-quarter that of gravity ( g = 9.8 metres, or 32.2 feet, per second squared ) and ground velocities of 20 cm (8 inches) per second. Alternative scales have been developed in bothJapan andEurope for local conditions.

The European ( MSK ) scale of 12 grades is similar to the abridged version of the Mercalli.

Modified Mercalli scale of earthquake intensity

  I. Not felt. Marginal and long-period effects of large earthquakes.

  II. Felt by persons at rest, on upper floors, or otherwise favourably placed to sense tremors.

  III. Felt indoors. Hanging objects swing. Vibrations are similar to those caused by the passing of light trucks. Duration can be estimated.

  IV. Vibrations are similar to those caused by the passing of heavy trucks (or a jolt similar to that caused by a heavy ball striking the walls). Standing automobiles rock. Windows, dishes, doors rattle. Glasses clink, crockery clashes. In the upper range of grade IV, wooden walls and frames creak.

  V. Felt outdoors; direction may be estimated. Sleepers awaken. Liquids are disturbed, some spilled. Small objects are displaced or upset. Doors swing, open, close. Pendulum clocks stop, start, change rate.

  VI. Felt by all; many are frightened and run outdoors. Persons walk unsteadily. Pictures fall off walls. Furniture moves or overturns. Weak plaster and masonry cracks. Small bells ring (church, school). Trees, bushes shake.

  VII. Difficult to stand. Noticed by drivers of automobiles. Hanging objects quivering. Furniture broken. Damage to weak masonry. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles, cornices. Waves on ponds; water turbid with mud. Small slides and caving along sand or gravel banks. Large bells ringing. Concrete irrigation ditches damaged.

  VIII. Steering of automobiles affected. Damage to masonry; partial collapse. Some damage to reinforced masonry; none to reinforced masonry designed to resist lateral forces. Fall of stucco and some masonry walls. Twisting, fall of chimneys, factory stacks, monuments, towers, elevated tanks. Frame houses moved on foundations if not bolted down; loose panel walls thrown out. Decayed pilings broken off. Branches broken from trees. Changes in flow or temperature of springs and wells. Cracks in wet ground and on steep slopes.

  IX. General panic. Weak masonry destroyed; ordinary masonry heavily damaged, sometimes with complete collapse; reinforced masonry seriously damaged. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluvial areas, sand and mud ejected; earthquake fountains, sand craters.

  X. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, and so on. Sand and mud shifted horizontally on beaches and flat land. Railway rails bent slightly.

  XI. Rails bent greatly. Underground pipelines completely out of service.

  XII. Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into air.

With the use of an intensity scale, it is possible to summarize such data for an earthquake by constructing isoseismal curves, which are lines that connect points of equal intensity. If there were complete symmetry about the vertical through the earthquake’s focus, isoseismals would be circles with the epicentre (the point at the surface of the Earth immediately above where the earthquake originated) as the centre. However, because of the many unsymmetrical geologic factors influencing intensity, the curves are often far from circular. The most probable position of the epicentre is often assumed to be at a point inside the area of highest intensity. In some cases, instrumental data verify this calculation, but not infrequently the true epicentre lies outside the area of greatest intensity.

Earthquake Magnitude

Earthquake magnitude is a measure of the “size” or amplitude of the seismic waves generated by an earthquake source and recorded by seismographs.

Types and nature of these waves are described in Seismic waves ( further below ).

Because the size of earthquakes varies enormously, it is necessary for purposes of comparison to compress the range of wave amplitudes measured on seismograms by means of a mathematical device.

In 1935, American seismologist Charles F. Richter set up a magnitude scale of earthquakes as the logarithm to base 10 of the maximum seismic wave amplitude ( in thousandths of a millimetre ) recorded on a standard seismograph ( the Wood-Anderson torsion pendulum seismograph ) at a distance of 60-miles ( 100 kilometers ) from the earthquake epicentre.

Reduction of amplitudes observed at various distances to the amplitudes expected at the standard distance of 100 kilometers ( 50-miles ) is made on the basis of empirical tables.

Richter magnitudes M_L are computed on the assumption the ratio of the maximum wave amplitudes at two ( 2 ) given distances is the same for all earthquakes and is independent of azimuth.

Richter first applied his magnitude scale to shallow-focus earthquakes recorded within 600 km of the epicentre in the southern California region. Later, additional empirical tables were set up, whereby observations made at distant stations and on seismographs other than the standard type could be used. Empirical tables were extended to cover earthquakes of all significant focal depths and to enable independent magnitude estimates to be made from body- and surface-wave observations.

A current form of the Richter scale is shown in the table. 

At the present time a number of different magnitude scales are used by scientists and engineers as a measure of the relative size of an earthquake. The P-wave magnitude (M_b), for one, is defined in terms of the amplitude of the P wave recorded on a standard seismograph. Similarly, the surface-wave magnitude (M_s) is defined in terms of the logarithm of the maximum amplitude of ground motion for surface waves with a wave period of 20 seconds.

As defined, an earthquake magnitude scale has no lower or upper limit. Sensitive seismographs can record earthquakes with magnitudes of negative value and have ‘recorded magnitudes up to’ about ‘9.0’ ( 1906 San Francisco earthquake, for example, had a Richter magnitude of 8.25 ).

A scientific weakness is that there is no direct mechanical basis for magnitude as defined above. Rather, it is an empirical parameter analogous to stellar magnitude assessed by astronomers. In modern practice a more soundly based mechanical measure of earthquake size is used—namely, the seismic moment (M₀). Such a parameter is related to the angular leverage of the forces that produce the slip on the causative fault. It can be calculated both from recorded seismic waves and from field measurements of the size of the fault rupture. Consequently, seismic moment provides a more uniform scale of earthquake size based on classical mechanics. This measure allows a more scientific magnitude to be used called moment magnitude (M_w). It is proportional to the logarithm of the seismic moment; values do not differ greatly from M_s values for moderate earthquakes. Given the above definitions, the great Alaska earthquake of 1964, with a Richter magnitude (M_L) of 8.3, also had the values M_s = 8.4, M₀ = 820 × 10²⁷ dyne centimetres, and M_w = 9.2

Earthquake Energy

Energy in an earthquake passing a particular surface site can be calculated directly from the recordings of seismic ground motion, given, for example, as ground velocity. Such recordings indicate an energy rate of 10⁵ watts per square metre (9,300 watts per square foot) near a moderate-size earthquake source. The total power output of a rupturing fault in a shallow earthquake is on the order of 10¹⁴ watts, compared with the 10⁵ watts generated in rocket motors.

The surface-wave magnitude M_s has also been connected with the surface energy E_s of an earthquake by empirical formulas. These give E_s = 6.3 × 10¹¹ and 1.4 × 10²⁵ ergs for earthquakes of M_s = 0 and 8.9, respectively. A unit increase in M_s corresponds to approximately a 32-fold increase in energy. Negative magnitudes M_s correspond to the smallest instrumentally recorded earthquakes, a magnitude of 1.5 to the smallest felt earthquakes, and one of 3.0 to any shock felt at a distance of up to 20 km ( 12 miles ). Earthquakes of magnitude 5.0 cause light damage near the epicentre; those of 6.0 are destructive over a restricted area; and those of 7.5 are at the lower limit of major earthquakes.

The total annual energy released in all earthquakes is about 10²⁵ ergs, corresponding to a rate of work between 10,000,000 million and 100,000,000 million kilowatts. This is approximately one ( 1 ) 1,000th the ‘annual amount of heat escaping from the Earth interior’.

90% of the total seismic energy comes from earthquakes of ‘magnitude 7.0 and higher’ – that is, those whose energy is on the order of 10²³ ergs or more.

Frequency

There also are empirical relations for the frequencies of earthquakes of various magnitudes. Suppose N to be the average number of shocks per year for which the magnitude lies in a range about M_s. Then log₁₀ N = a − bM_s fits the data well both globally and for particular regions; for example, for shallow earthquakes worldwide, a = 6.7 and b = 0.9 when M_s > 6.0. The frequency for larger earthquakes therefore increases by a factor of about 10 when the magnitude is diminished by one unit. The increase in frequency with reduction in M_s falls short, however, of matching the decrease in the energy E. Thus, larger earthquakes are overwhelmingly responsible for most of the total seismic energy release. The number of earthquakes per year with M_b > 4.0 reaches 50,000.

Earthquake Occurrences & Plate Tectonic associations

Global seismicity patterns had no strong theoretical explanation until the dynamic model called plate tectonics was developed during the late 1960s. This theory holds that the Earth’s upper shell, or lithosphere, consists of nearly a dozen large, quasi-stable slabs called plates. The thickness of each of these plates is roughly 50-miles ( 80 km ). Plates move horizontally relative to neighbouring plates at a rate of 0.4 to 4 inches ( 1-cm to 10-cm ) per year over a shell of lesser strength called the asthenosphere. At the plate edges where there is contact between adjoining plates, boundary tectonic forces operate on the rocks, causing physical and chemical changes in them. New lithosphere is created at oceanic ridges by the upwelling and cooling of magma from the Earth’s mantle. The horizontally moving plates are believed to be absorbed at the ocean trenches, where a subduction process carries the lithosphere downward into the Earth’s interior. The total amount of lithospheric material destroyed at these subduction zones equals that generated at the ridges. Seismological evidence ( e.g. location of major earthquake belts ) is everywhere in agreement with this tectonic model.

Earthquake Types:

- Shallow Earthquakes;

- Intermediate Earthquakes;

- Deep Focus ( Deep-Foci ) Earthquakes; and

- Deeper Focus ( Deeper-Foci ) Earthquakes.

Earthquake sources, are concentrated along oceanic ridges, corresponding to divergent plate boundaries.

At subduction zones, associated with convergent plate boundaries, deep-focus earthquakes and intermediate focus earthquakes mark locations of the upper part of a dipping lithosphere slab.

Focal ( Foci ) mechanisms indicate stresses aligned with dip of the lithosphere underneath the adjacent continent or island arc.

IntraPlate Seismic Event Anomalies

Some earthquakes associated with oceanic ridges are confined to strike-slip faults, called transform faults offset ridge crests. The majority of earthquakes occurring along such horizontal shear faults are characterized by slip motions.

Also in agreement with plate tectonics theory is high seismicity encountered along edges of plates where they slide past each other. Plate boundaries of this kind, sometimes called fracture zones include, the:

- San Andreas Fault system in California; and,

- North Anatolian fault system in Turkey.

Such plate boundaries are the site of interplate earthquakes of shallow focus.

Low seismicity within plates is consistent with plate tectonic description. Small to large earthquakes do occur in limited regions well within the boundaries of plates, however such ‘intraplate seismic events’ can be explained by tectonic mechanisms other than plate boundary motions and their associated phenomena.

Most parts of the world experience at least occasional shallow earthquakes – those that originate within 60 km ( 40 miles ) of the Earth’s outer surface. In fact, the great ‘majority of earthquake foci ( focus ) are shallow’. It should be noted, however, that the geographic distribution of smaller earthquakes is less completely determined than more severe quakes, partly because the ‘availability of relevant data dependent on distribution of observatories’.

Of the total energy released in earthquakes, 12% comes from intermediate earthquakes—that is, quakes with a focal depth ranging from about 60 to 300 km. About 3 percent of total energy comes from deeper earthquakes. The frequency of occurrence falls off rapidly with increasing focal depth in the intermediate range. Below intermediate depth the distribution is fairly uniform until the greatest focal depths, of about 700 km (430 miles), are approached.

Deeper-Focus Earthquakes

Deeper-focus earthquakes commonly occur in patterns called Benioff zones dipping into the Earth, indicating presence of a subducting slab where dip angles of these slabs average about 45° – with some shallower – and others nearly vertical.

Benioff zones coincide with tectonically active island arcs, such as:

- Aleutian islands;

- Japan islands;

- Vanuatu islands; and

- Tonga.

Island arcs are, normally ( but not always ) associated, with:

Ultra-Deep Sea Ocean Trenches, such as the:

South America ( Andes mountain system ).

Exceptions to this rule, include:

- Romania ( East Europe ) mountain system; and

- Hindu Kush mountain system.

Most Benioff zones,  deep-earthquake foci and intermediate-earthquake foci are usually found within a narrow layer, however recent more precise hypocentral locations - in Japan and elsewhere - indicate two ( 2 ) distinct parallel bands of foci only 12 miles ( 20 kilometers ) apart.

Aftershocks, Swarms and Foreshocks

Major or even moderate earthquake of shallow focus is followed by many lesser-size earthquakes close to the original source region. This is to be expected if the fault rupture producing a major earthquake does not relieve all the accumulated strain energy at once. In fact, this dislocation is liable to cause an increase in the stress and strain at a number of places in the vicinity of the focal region, bringing crustal rocks at certain points close to the stress at which fracture occurs. In some cases an earthquake may be followed by 1,000 or more aftershocks a day.

Sometimes a large earthquake is followed by a similar one along the same fault source within an hour or perhaps a day. An extreme case of this is multiple earthquakes. In most instances, however, the first principal earthquake of a series is much more severe than the aftershocks. In general, the number of aftershocks per day decreases with time.

Aftershock frequency, is ( roughly ):

Inversely proportional to time since occurrence of largest earthquake in series.

Most major earthquakes occur without detectable warning, but some principal earthquakes are preceded by foreshocks.

Japan 2-Years of Hundreds of Thousands Of Earthquakes

In another common pattern, large numbers of small earthquakes may occur in a region for months without a major earthquake.

In the Matsushiro region of Japan, for instance, there occurred ( between August 1965 and August 1967 ) a ‘series of earthquakes’ numbering in the hundreds of thousands – some sufficiently strong ( up to Richter magnitude 5.0 ) causing property damage but no casualties.

Maximum frequency? 6,780 small earthquakes on just April 17, 1966.

Such series of earthquakes are called earthquake swarms.

Earthquakes, associated with volcanic activity often occur in swarms - though swarms also have been observed in many nonvolcanic regions.

Study of Earthquakes

Seismic waves

Principal types of seismic waves

Seismic Waves ( S Waves ), generated by an earthquake source, are commonly classified into three ( 3 ) ‘leading types’.

The first two ( 2 ) leading types, propagate ( travel ) within the body of the Earth, are known as:

P ( Primary ) Seismic Waves; and,

S ( Secondary ) Seismic Waves ( S / S Waves ).

The third ( 3^rd ) leading types, propagate ( travel ) along surface of the Earth, are known as:

L ( Love ) Seismic Waves; and,

R ( Rayleigh ) Seismic Waves.

During the 19^th Century, existence of these types of seismic waves were mathematically predicted, and modern comparisons show close correspondence between such ‘theoretical calculations‘ and ‘actual measurements’ of seismic waves.

P seismic waves travel as elastic motions at the highest speeds, and are longitudinal waves transmitted by both solid and liquid materials within inner Earth.

P waves ( particles of the medium) vibrate in a manner ‘similar to sound waves’ transmitting media ( alternately compressed and expanded ).

The slower type of body wave, the S wave, travels only through solid material. With S waves, the particle motion is transverse to the direction of travel and involves a shearing of the transmitting rock.

Focus ( Foci )

Because of their greater speed, P waves are the first ( 1^st ) to reach any point on the Earth’s surface. The first ( 1^st ) P-wave onset ‘starts from the spot where an earthquake originates’. This point, usually at some depth within the Earth, is called the focus (also known as ) hypocentre.

Epicenter

Point ‘at the surface’ ( immediately ‘above the Focus / Foci’ ) is known as the ‘epicenter’.

Love waves and Rayleigh waves, guided by the free surface of the Earth, trail after P and S waves have passed through the body of planet Earth.

Rayleigh waves ( R Waves ) and Love waves ( L Waves ) involve ‘horizontal particle motion’, however ‘only Rayleigh waves exhibit ‘vertical ground displacements’.

Rayleigh waves ( R waves ) and Love ( L waves ) travel ( propagate ) and disperse into long wave trains, when occurring away-from ‘alluvial basin sources’, at substantial distances cause much of the Earth surface ground shaking felt during earthquakes.

Seismic Wave Focus ( Foci ) Properties

At all distances from the focus ( foci ), mechanical properties of rocks, such as incompressibility, rigidity and density play roles, in:

- Speed of ‘wave travel’;

- Duration of ‘wave trains’; and,

- Shape of ‘wave trains’.

Layering of the rocks and the physical properties of surface soil also affect wave characteristics.

In most cases, ‘elastic behaviors occur in earthquakes, however strong shaking ( of surface soils from the incident seismic waves ) sometimes result in ‘nonelastic behavior’, including slumping ( i.e., downward and outward movement of unconsolidated material ) and liquefaction of sandy soil.

Seismic wave that encounters a boundary separating ‘rocks of different elastic properties’ undergo reflection and refraction where a special complication exists because conversion between wave types usually also occur at such a boundary where an incident P or S wave can yield reflected P and S waves and refracted P and S waves.

Between Earth structural layers, boundaries give rise to diffracted and scattered waves, and these additional waves are partially responsible for complications observed in ground motion during earthquakes.

Modern research is concerned with ‘computing, synthetic records of ground motion realistic comparisons with observed actual ground shaking’, using wave theory in complex structures.

Grave Duration Long-Periods, Audible Earthquake Frequencies, and Other Earth Anomalies

Frequency range of seismic waves is widely varied, from being ‘High Frequency’ ( HF ) as an ‘audible range’ ( i.e. greater than > 20 hertz ) to, as Low Frequency ( LF ) as subtle as ‘free oscillations of planet Earth’ – with grave Long-Periods being 54-minutes ( see below Long-Period oscillations of the globe ).

Seismic wave attenuations in rock imposes High-Frequency ( HF ) limits, and in small to moderate earthquakes the dominant frequencies extend in Surface Waves from about 1.0 Hz to 0.1 Hertz.

Seismic wave amplitude range is also great in most earthquakes.

Displacement of ground ranges, from: 10⁻¹⁰ to 10⁻¹ metre ( 4⁻¹² to 4-inches ).

Great Earthquake Speed

Great Earthquake Ground Speed Moves Faster Than 32-Feet Per Second, Squared ( 9.8 Metres Per Second, Squared ) -

In the greatest earthquakes, ground amplitude of predominant P waves may be several centimetres at periods of 2-seconds to 5-seconds, however very close to seismic sources of ‘great earthquakes’, investigators measured ‘large wave amplitudes’ with ‘accelerations of the ground exceeding ( speed of gravity ) 32.2 feet per second squared ( 9.8 meters per second, squared ) at High Frequencies ( HF ) and ground displacements of 1 metre at Low Frequencies ( LF ).

Seismic Wave Measurement

Seismographs and Accelerometers

Seismographs ‘measure ground motion’ in both ‘earthquakes’ and ‘microseisms’ ( small oscillations described below ).

Most of these instruments are of the pendulum type. Early mechanical seismographs had a pendulum of large mass ( up to several tons ) and produced seismograms by scratching a line on smoked paper on a rotating drum.

In later instruments, seismograms ( also known as seismometers ) recorded via ‘rays of light bounced off a mirror’ within a galvanometer using electric current from electromagnetic induction ‘when the pendulum of the seismograph moved’.

Technological developments in electronics have given rise to ‘higher-precision pendulum seismometers’ and ‘sensors of ground motion’.

In these instruments electric voltages produced by motions of the pendulum or the equivalent are passed through electronic circuitry to ‘amplify ground motion digitized for more exactness’ readings.

Seismometer Nomenclature Meanings

Seismographs are divided into three ( 3 ) types of instruments knowingly confused by the public because of their varied names, as:

- Short-Period;

- Intermediate-Period ( also known as Long-Period );

- Long-Period ( also known as Intermediate-Period );

- Ultra-Long-Period ( also known as Broadband or Broad-Band ); or,

- Broadband ( also known as Ultra Long-Period or UltraLong-Period ).

Short-Period instruments are used to record P and S body waves with high magnification of the ground motion. For this purpose, the seismograph response is shaped to peak at a period of about 1-second or less.

Intermediate-period instruments, the type used by the World-Wide Standardized Seismographic Network ( WWSSN ) – described in the section Earthquake observatories – had about a 20-second ( maximum ) response.

Recently, in order to provide as much flexibility as possible for research work, the trend has been toward the operation of ‘very broadband seismographs’ digitizing representation of signals. This is usually accomplished with ‘very long-period pendulums’ and ‘electronic amplifiers’ passing signals in the band between 0.005 Hz and 50 Hertz.

When seismic waves close to their source are to be recorded, special design criteria are needed. Instrument sensitivity must ensure that the largest ground movements can be recorded without exceeding the upper scale limit of the device. For most seismological and engineering purposes the wave frequencies that must be recorded are higher than 1 hertz, and so the pendulum or its equivalent can be small. For this reason accelerometers that measure the rate at which the ground velocity is changing have an advantage for strong-motion recording. Integration is then performed to estimate ground velocity and displacement. The ground accelerations to be registered range up to two times that of gravity. Recording such accelerations can be accomplished mechanically with short torsion suspensions or force-balance mass-spring systems.

Because many strong-motion instruments need to be placed at unattended sites in ordinary buildings for periods of months or years before a strong earthquake occurs, they usually record only when a trigger mechanism is actuated with the onset of ground motion. Solid-state memories are now used, particularly with digital recording instruments, making it possible to preserve the first few seconds before the trigger starts the permanent recording and to store digitized signals on magnetic cassette tape or on a memory chip. In past design absolute timing was not provided on strong-motion records but only accurate relative time marks; the present trend, however, is to provide Universal Time ( the local mean time of the prime meridian ) by means of special radio receivers, small crystal clocks, or GPS ( Global Positioning System ) receivers from satellite clocks.

Prediction of strong ground motion and response of engineered structures in earthquakes depends critically on measurements of the spatial variability of earthquake intensities near the seismic wave source. In an effort to secure such measurements, special arrays of strong-motion seismographs have been installed in areas of high seismicity around the world.

Large-aperture seismic arrays (linear dimensions on the order of about 1/2 mile ( 0.6 mile ) to about 6 miles ( 1 kilometer to 10 kilometers ) of strong-motion accelerometers now used to improve estimations of speed, direction of propagation and types of seismic wave components.

Particularly important for full understanding of seismic wave patterns at the ground surface is measurement of the variation of wave motion with depth where to aid in this effort special digitally recording seismometers have been ‘installed in deep boreholes’.

Ocean-Bottom Measurements

70% of the Earth’s surface is covered by water so, ocean-bottom seismometers augment ( add to ) global land-based system of recording stations.

Field tests have established the feasibility of extensive long-term recording by instruments on the seafloor.

Japan has a ‘semi-permanent seismograph’ system of this type placed on the seafloor off the Pacific Ocean eastcoast of centralHonshu,Japan in 1978 by means of a ‘cable’.

Because of mechanical difficulties maintaining ‘permanent ocean-bottom instrumentation’, different systems have been considered.

They ‘all involve placement of instruments on the ocean bottom’, though they employ various mechanisms for data transmission.

Signals may be transmitted to the ocean surface for retransmission by auxiliary apparatus or transmitted via cable to a shore-based station. Another system is designed to release its recording device automatically, allowing it to float to the surface for later recovery.

Ocean bottom seismograph use should yield much-improved global coverage of seismic waves and provide new information on the seismicity of oceanic regions.

Ocean-bottom seismographs will enable investigators to determine the details of the crustal structure of the seafloor and, because of the relative ‘thinness of the oceanic crust‘, should make possible collection of clear seismic information about Earth’s upper mantle.

Ocean bottom seismograph systems are also expected to provide new data, on Earth:

- Continental Shelf Plate Boundaries;

- MicroSeisms ( origins and propagations ); and,

- Ocean to Continent behavior margins.

MicroSeisms Measurements

MicroSeisms ( also known as ) ‘small ground motions’ are commonly recorded by seismographs. Small weak seismic wave motions ( also known as ) MicroSeisms are ‘not generated by earthquakes’ but in some instances can complicate accurate earthquake measurement recording. MicroSeisms are of scientific interest because their form relates to Earth surface structure.

Microseisms ( some ) have ‘local cause’, for example:

Microseisms due to traffic ( or machinery ) or local wind effects, storms and rough surf against an extended steep coastline.

Another class of microseisms exhibits features that are very similar on records traced at earthquake observatories that are widely separated, including approximately simultaneous occurrence of maximum amplitudes and similar wave frequencies. These microseisms may persist for many hours and have more or less regular periods of about five to eight seconds.

The largest amplitudes of such microseisms are on the order of 10⁻³ cm ( 0.0004 inch ) and ‘occur in coastal regions’. Amplitudes also depend to some extent on local geologic structure.

Some microseisms are produced when ‘large standing water waves are formed far out at sea’. The period of this type of microseism is ‘half’ of the Standing Wave.

Observations of Earthquakes

Earthquake Observatories

During the late 1950s, there were only about seven-hundred ( 700 ) seismographic stations worldwide, equipped with seismographs of various types and frequency responses – few instruments of which were calibrated; actual ground motions could not be measured, and ‘timing errors of several seconds’ were common.

The World-Wide Standardized Seismographic Network ( WWSSN ), became the first modern worldwide standardized system established to remedy that situation.

Each of the WWSSN had six ( 6 ) seismograph stations with three ( 3 ) short-period and three ( 3 ) long-period seismographs with timing and accuracy maintained by quartz crystal clocks, and a calibration pulse placed daily on each record.

By 1967, the WWSSN consisted of about one-hundred twenty ( 120 ) stations throughout sixty ( 60 ) countries, resulting in data to provide the basis for significant advances in research, on:

- Earthquakes ( mechanisms );

- Plate Tectonics ( global ); and,

- Deep-Structure Earth ( interior ).

By the 1980s a further upgrading of permanent seismographic stations began with the installation of digital equipment by a number of organizations.

Global digital seismograph station networks, now in operation, consist of:

- Seismic Research Observatories ( SRO ) within boreholes drilled 330 feet ( 100 metres ) deep in Earth ground; and,

- Modified high-gain long-period earthquake observatories located on Earth ground surfaces.

The Global Digital Seismographic Network in particular has remarkable capability, recording all motions from Earth ocean tides to microscopic ground motions at the level of local ground noise.

At present there are about 128 sites. With this system the long-term seismological goal will have been accomplished to equip global observatories with seismographs that can record every small earthquake anywhere over a broad band of frequencies.

 Epicentre Earthquakes Located

Many observatories make provisional estimates of the epicentres of important earthquakes. These estimates provide preliminary information locally about particular earthquakes and serve as first approximations for the calculations subsequently made by large coordinating centres.

If an earthquake’s epicentre is less than 105° away from an earthquake observatory, the epicentre position can often be estimated from the readings of three ( 3 ) seismograms recording perpendicular components of the ground motion.

For a shallow earthquake the epicentral distance is indicated by the interval between the arrival times of P and S waves; the azimuth and angle of wave emergence at the surface indicated by somparing sizes and directions of the first ( 1st ) movements indicated by seismograms and relative sizes of later waves - particularly surface waves.

Anomaly

It should be noted, however, that in certain regions the first ( 1st ) wave movement at a station arrives from a direction differing from the azimuth toward the epicentre. This ‘anomaly is usually explained’ by ‘strong variations in geologic structures’.

When data from more than one observatory are available, an earthquake’s epicentre may be estimated from the times of travel of the P and S waves from source to recorder. In many seismically active regions, networks of seismographs with telemetry transmission and centralized timing and recording are common. Whether analog or digital recording is used, such integrated systems greatly simplify observatory work: multichannel signal displays make identification and timing of phase onsets easier and more reliable. Moreover, online microprocessors can be programmed to pick automatically, with some degree of confidence, the onset of a significant common phase, such as P, by correlation of waveforms from parallel network channels. With the aid of specially designed computer programs, seismologists can then locate distant earthquakes to within about 10 km (6 miles) and the epicentre of a local earthquake to within a few kilometres.

Catalogs of earthquakes felt by humans and of earthquake observations have appeared intermittently for many centuries. The earliest known list of instrumentally recorded earthquakes with computed times of origin and epicentres is for the period 1899 – 1903, afterwhich cataloging of earthquakes became more uniform and complete.

Especially valuable is the service provided by the International Seismological Centre ( ISC ) in Newbury, UK that monthly receives more than 1,000,000 seismic readings from more than 2,000 seismic monitoring stations worldwide and preliminary estimates locations of approximately 1,600 earthquakes from national and regional agencies and observatories.

The ISC publishes a monthly bulletin about once ( 1 ) every 2-years. The bulletin, when published, provides ‘all available information that was’ on each of more than 5,000 earthquakes.

Various national and regional centres control networks of stations and act as intermediaries between individual stations and the international organizations.

Examples of long-standing national centers include, the:

Japan Meteorological Agency; and,

U.S. National Earthquake Information Center ( NEIC ), a subdivision of the U.S. Geological Survey ( USGS ).

Centers, such as the aforementioned, normally make ‘local earthquake estimates’, of:

- Magnitude;

- Epicentre;

- Time origin; and,

- Focal depth.

Global seismicity data is continually accessible via Incorporated Research Institutions for Seismology ( IRIS ) website.

An important research technique infers the character of faulting ( in an earthquake ) from recorded seismograms.

For example, observed distributions ( of the directions of the first onsets in waves arriving at the Earth’s surface ) have been effectively used.

Onsets are called “compressional” or “dilatational,” according to whether the direction is ‘away from’ or ‘toward’ the focus, respectively.

A polarity pattern becomes recognizable when the directions of the P-wave onsets are plotted on a map – there are broad areas in which the first onsets are predominantly compressions, separated from predominantly dilatational areas by nodal curves near which the P-wave amplitudes are abnormally small.

In 1926 the American geophysicist Perry E. Byerly used patterns of P onsets over the entire globe to infer the orientation of the fault plane in a large earthquake. The polarity method yields two P-nodal curves at the Earth’s surface; one curve is in the plane containing the assumed fault, and the other is in the plane ( called the auxiliary plane ) that passes through the focus and is perpendicular to the forces of the plane.

The recent availability of worldwide broad-based digital recording enabled computer programs written estimating the fault mechanism and seismic moment based on complete pattern of seismic wave arrivals.

Given a well-determined pattern at a number of earthquake observatories, it is possible to locate two ( 2 ) planes, one ( 1 ) of which is the plane containing the fault.

Earthquake Prediction

Earthquake Observations & Interpretations

Statistical earthquake occurrences are believed theorized, not widely accepted nor detecting periodic cycles, records of which old periodicities in time and space for major / great earthquakes cataloged are as old as 700 B.C. with China holding the ‘world’s most extensive catalog’ of approximately one ( 1 ) one-thousand ( 1,000 ) destructive earthquakes where ‘magnitude ( size )’ measurements were assessed based on ‘damage reports’ and experienced periods of ‘shaking’ and ‘other observations’ determining ‘intensity’ of those earthquakes.

Earthquake Attributions to Postulation

Precursor predictability approaches involve what some believe is sheer postulating what the initial trigger mechanisms are that force Earth ruptures, however where this becomes bizarre is where such forces have been attributed, to:

- Weather Severity;

- Volcano Activity; and,

- Ocean Tide Force ( Moon ).

EXAMPLE: Correlations between physical phenomena assumed providing trigger mechanisms for earthquake repetition.

Professionals believe such must always be made to discover whether a causative link is actually present, and they further believe that to-date: ‘no cases possess any trigger mechanism’ – insofaras ‘moderate earthquakes’ to ‘large earthquakes’ unequivocally finding satisfaction with various necessary criteria.

Statistical methods also have been tried with populations of regional earthquakes with such suggested, but never established generally, that the slope b of the regression line between the logarithm of the number of earthquakes and the magnitude for a region may change characteristically with time.

Specifically, the claim is that the b value for the population of ‘foreshocks of a major earthquake’ may be ‘significantly smaller’ than the mean b value for the region averaged ‘over a long interval of time’.

Elastic rebound theory, of earthquake sources, allows rough prediction of the occurrence of large shallow earthquakes – for example – Harry F. Reid gave a crude forecast of the next great earthquake near San Francisco ( theory also predicted, of-course, the place would be along the San Andreas Fault or associated fault ). Geodetic data indicated that during an interval of 50 years relative displacements of 3.2 metres ( 10-1/2 feet ) had occurred at distant points across the fault. Elastic-rebound maximum offset ( along the fault in the 1906 earthquake ) was 6.5 metres. Therefore, ( 6.5 ÷ 3.2 ) × 50 or about 100-years would again elapse before sufficient strain accumulated for the occurrence of an earthquake comparable to that of 1906; premises being regional strain will grow uniformly and various constraints have not been altered by the great 1906 rupture itself ( such as by the onset of slow fault slip ).

Such ‘strain rates’ are now, however being more adequately measured ( along a number of active faults, e.g.San Andreas Fault) using networks of GPS sensors.

Earthquake Prediction Research

For many years prediction research has been influenced by the basic argument that ‘strain accumulates in rock masses in the vicinity of a fault, resulting in crustal deformation.

Deformations have been measured in ‘horizontal directions’ along active faults via ‘trilateration’ and ‘triangulation’ and in ‘vertical directions’ via ‘precise leveling and tiltmeters’.

Investigators ( some ) believe ‘ground-water level changes occur prior to earthquakes’ with variations of such reports from China.

Ground water levels respond to an array of complex factors ( e.g. ‘rainfall’ ) where such would have to be removed if changes in water level changes were studied in relation to earthquakes.

Phenomena Precursor Premonitories

Dilatancy theory ( i.e., volume increase of rock prior to rupture ) once occupied a central position in discussions of premonitory phenomena of earthquakes, but now receives less support based on observations that many solids exhibit dilatancy during deformation. For earthquake prediction, significance of dilatancy, if real, effects various measurable quantities of crustal Earth, i.e. seismic velocity, electric resistivity and ground and water levels. Consequences of dilatancy for earthquake prediction are summarized in the table ( below ):

The best-studied consequence is the effect on seismic velocities. The influence of internal cracks and pores on the elastic properties of rocks can be clearly demonstrated in laboratory measurements of those properties as a function of hydrostatic pressure. In the case of saturated rocks, experiments predict – for shallow earthquakes – that dilatancy occurs as a portion of the crust is stressed to failure, causing a decrease in the velocities of seismic waves. Recovery of velocity is brought about by subsequent rise of the pore pressure of water, which also has the effect of weakening the rock and enhancing fault slip.

Strain buildup in the focal region may have measurable effects on other observable properties, including electrical conductivity and gas concentration. Because the electrical conductivity of rocks depends largely on interconnected water channels within the rocks, resistivity may increase before the cracks become saturated. As pore fluid is expelled from the closing cracks, the local water table would rise and concentrations of gases such as radioactive radon would increase. No unequivocal confirming measurements have yet been published.

Geologic methods of extending the seismicity record back from the present also are being explored. Field studies indicate that the sequence of surface ruptures along major active faults associated with large earthquakes can sometimes be constructed.

An example is the series of large earthquakes inTurkeyin the 20th Century, which were caused mainly by successive westward ruptures of the North Anatolian Fault.

Liquefaction effects preserved in beds of sand and peat have provided evidence ( using radiometric dating methods ) for large paleoearthquakes back more than 1,000 years in many seismically active zones, including the U.S. Northwest Pacific Ocean Coastal Region.

Less well-grounded precursory phenomena, particularly earthquake lights and animal behaviour, sometimes draw more public attention than the precursors discussed above.

Unusual lights in the sky reported, and abnormal animal behaviour, preceding earthquakes are known to seismologists – mostly in anecdotal form.

Both phenomena, are usually explained away in terms of ( prior to earthquakes ) there being:

- Gaseous emmissions from Earth ground;

- Electric stimuli ( various ), e.g. HAARP, etcetera, from Earth ground; and,

- Acoustic stimuli ( various ), e.g. Seismic Wave subsonic emmissions from Earth ground.

At the present time, there is no definitive experimental evidence supporting reported claims of animals sometimes sensing an approaching earthquake.

… [ CENSORED-OUT ] …

Earthquake Hazard Reduction Methods

Considerable work has been done in seismology to explain the characteristics of the recorded ground motions in earthquakes. Such knowledge is needed to predict ground motions in future earthquakes so that earthquake-resistant structures can be designed.

Although earthquakes cause death and destruction via such secondary effects ( i.e. landslides, tsunamis, fires and fault rupture ), the greatest losses ( human lives and property ) result from ‘collapsing man-made structures’ amidst violent ground shaking.

The most effective way to mitigate ( minimize ) damage from earthquakes – from an engineering standpoint – is to design and construct structures capable of withstanding ‘strong ground motions’.

Interpreting recorded ground motions

Most ‘elastic waves’ recorded ( close to an extended fault source ) are complicated and difficult to interpret uniquely.

Understanding such, near-source motion, can be viewed as a 3 part problem.

The first ( 1st ) part stems from ‘elastic wave generations’ radiating ( from the slipping fault ) as the ‘moving rupture sweeps-out an area of slip’ ( along the fault plane ) – within a given time.

Wave pattern production dependencies on several parameters, such as:

Fault dimension and rupture velocity.

Elastic waves ( various types ) radiate, from the vicinity of the moving rupture, in all directions.

Geometric and frictional properties of the fault, critically affect wave pattern radiation from it.

The second ( 2nd ) part of the problem concerns the passage of the waves through the intervening rocks to the site and the effect of geologic conditions.

The third ( 3rd ) part involves the conditions at the recording site itself, such as topography and highly attenuating soils. All these questions must be considered when estimating likely earthquake effects at a site of any proposed structure.

Experience has shown that the ground strong-motion recordings have a variable pattern in detail but predictable regular shapes in general ( except in the case of strong multiple earthquakes ).

EXAMPLE: Actual ground shaking ( acceleration, velocity and displacement ) recorded during an earthquake ( see figure below ).

 In a strong horizontal shaking of the ground near the fault source, there is an initial segment of motion made up mainly of P waves, which frequently manifest themselves strongly in the vertical motion. This is followed by the onset of S waves, often associated with a longer-period pulse of ground velocity and displacement related to the near-site fault slip or fling. This pulse is often enhanced in the direction of the fault rupture and normal to it. After the S onset there is shaking that consists of a mixture of S and P waves, but the S motions become dominant as the duration increases. Later, in the horizontal component, surface waves dominate, mixed with some S body waves. Depending on the distance of the site from the fault and the structure of the intervening rocks and soils, surface waves are spread out into long trains.

Expectant Seismic Hazard Maps Constructed

In many regions, seismic expectancy maps or hazard maps are now available for planning purposes. The anticipated intensity of ground shaking is represented by a number called the peak acceleration or the peak velocity.

To avoid weaknesses found in earlier earthquake hazard maps, the following general principles are usually adopted today:

The map should take into account not only the size but also the frequency of earthquakes.

The broad regionalization pattern should use historical seismicity as a database, including the following factors: major tectonic trends, acceleration attenuation curves, and intensity reports.

Regionalization should be defined by means of contour lines with design parameters referred to ordered numbers on neighbouring contour lines ( this procedure minimizes sensitivity concerning the exact location of boundary lines between separate zones ).

The map should be simple and not attempt to microzone the region.

The mapped contoured surface should not contain discontinuities, so that the level of hazard progresses gradually and in order across any profile drawn on the map.

Developing resistant structures

Developing engineered structural designs that are able to resist the forces generated by seismic waves can be achieved either by following building codes based on hazard maps or by appropriate methods of analysis. Many countries reserve theoretical structural analyses for the larger, more costly, or critical buildings to be constructed in the most seismically active regions, while simply requiring that ordinary structures conform to local building codes. Economic realities usually determine the goal, not of preventing all damage in all earthquakes but of minimizing damage in moderate, more common earthquakes and ensuring no major collapse at the strongest intensities. An essential part of what goes into engineering decisions on design and into the development and revision of earthquake-resistant design codes is therefore seismological, involving measurement of strong seismic waves, field studies of intensity and damage, and the probability of earthquake occurrence.

Earthquake risk can also be reduced by rapid post-earthquake response. Strong-motion accelerographs have been connected in some urban areas, such as Los Angeles, Tokyo, and Mexico City, to interactive computers.

Recorded waves are correlated with seismic intensity scales and rapidly displayed graphically on regional maps via the World Wide Web.

Exploration of the Earth’s interior with seismic waves

Seismological Tomography

Deep Structure Earth seismological data from several sources, including:

- Nuclear explosions containing P-Waves and S-Waves;

- Earthquakes containing P-Waves and S-Waves;

- Earth ‘surface wave dispersions’ from ‘distant earthquakes’; and,

- Earth ‘planetary vibration’ from ‘Great Earthquakes’

One of the major aims of seismology was to infer a minimum set of properties surrounding the planet interior of Earth that might explain recorded seismic ‘wave trains’ in detail.

Deep Structure Earth exploration made ‘tremendous progress during the first half of the 20th Century ( 1900s – 1950s ), realizing goals was severely limited until the 1960s because of laborious effort required just to evaluate theoretical models and process large amounts of recorded earthquake data.

Today’s application of supercomputer high-speed data processing enormous quantities of stored data and information retrieval capabilities opened information technology ( IT ) passageways leading to major advancements in the way data is manipulated ( data handling ) for advanced theoretical modeling, research analytics and developmental prototyping.

Earth structure realistic modeling studies by researchers since the middle 1970s include continental and oceanic boundaries, mountains and river valleys rather than simple structures such as those involving variation only with depth, and various technical developments have benefited observational seismology.

EXAMPLE: Deep Structure Earth significant exploration using 3D ( three dimensional ) imaging with equally impressive display ( monitor ) equipment possible from advanced microprocessor architecture redesign, new discoveries of materials and new concepts making seismic exploratory techniques developed by petroleum industry adaptations ( e.g. seismic reflection ) highly recognized as adopted procedures.

Deep Structure Earth major methods for determining planet interior is detailed analysis of seismograms of seismic waves; noting earthquake readings additionally provide estimates of, Earth internal:

- Wave velocities;

- Density; and,

- Parameters of ‘elasticity’ ( stretchable ) and ‘inelasticity’ ( fixed ).

Earthquake Travel Time

Primary procedure is to measure the travel times of various wave types, such as P and S, from their source to the recording seismograph. First, however, identification of each wave type with its ray path through the Earth must be made.

Seismic rays for many paths of P and S waves leaving the earthquake focus F are shown in the figure.

Deep-Focus Deep-Structure Earth Coremetrics

Rays corresponding to waves that have been reflected at the Earth’s outer surface (or possibly at one of the interior discontinuity surfaces) are denoted as PP, PS, SP, PSS, and so on. For example, PS corresponds to a wave that is of P type before surface reflection and of S type afterward. In addition, there are rays such as pPP, sPP, and sPS, the symbols p and s corresponding to an initial ascent to the outer surface as P or S waves, respectively, from a deep focus.

An especially important class of rays is associated with a discontinuity surface separating the central core of the Earth from the mantle at a depth of about 2,900 km (1,800 miles) below the outer surface. The symbol c is used to indicate an upward reflection at this discontinuity. Thus, if a P wave travels down from a focus to the discontinuity surface in question, the upward reflection into an S wave is recorded at an observing station as the ray PcS and similarly with PcP, ScS, and ScP. The symbol K is used to denote the part (of P type) of the path of a wave that passes through the liquid central core. Thus, the ray SKS corresponds to a wave that starts as an S wave, is refracted into the central core as a P wave, and is refracted back into the mantle, wherein it finally emerges as an S wave. Such rays as SKKS correspond to waves that have suffered an internal reflection at the boundary of the central core.

The discovery of the existence of an inner core in 1936 by the Danish seismologist Inge Lehmann made it necessary to introduce additional basic symbols. For paths of waves inside the central core, the symbols i and I are used analogously to c and K for the whole Earth; therefore, i indicates reflection upward at the boundary between the outer and inner portions of the central core, and I corresponds to the part (of P type) of the path of a wave that lies inside the inner portion. Thus, for instance, discrimination needs to be made between the rays PKP, PKiKP, and PKIKP. The first of these corresponds to a wave that has entered the outer part of the central core but has not reached the inner core, the second to one that has been reflected upward at the inner core boundary, and the third to one that has penetrated into the inner portion.

By combining the symbols p, s, P, S, c, K, i, and I in various ways, notation is developed for all the main rays associated with body earthquake waves.

Hidden Inner Earth Deep Structure Anomalies

The symbol J, introduced to correspond with S waves located within Earth’s inner core, is only evidence if such ( if ever ) be found for such waves. Use of times of travel along rays to infer a hidden structure is analogous to the use of X-rays in medical tomography. The method involves reconstructing an image of internal anomalies from measurements made at the outer surface. Nowadays, hundreds of thousands of travel times of P and S waves are available in earthquake catalogs for the tomographic imaging of the Earth’s interior and the mapping of internal structure.

Inner Earth Deep Structure

Thinest & Thickest Part of Earth’s Crust

Inner Earth, based on earthquake records and imaging studies, are officially represented, as:

A solid layer flowing patterns of a mantle, at its ’thickest point’ being about 1,800-miles ( 2,900 kilometers ) thick, although at its ‘thinest point’ less than 6-miles ( 10 kilometers ) beneath the ocean seafloor bed beneath the surface of the ultra-deep sea.

The thin surface rock layer surrounding the mantle is the crust, whose lower boundary is called the Mohorovičić discontinuity. In normal continental regions the crust is about 30 kilometers to 40 km thick; there is usually a superficial low-velocity sedimentary layer underlain by a zone in which seismic velocity increases with depth. Beneath this zone there is a layer in which P-wave velocities in some places fall from 6 to 5.6 km per second. The middle part of the crust is characterized by a heterogeneous zone with P velocities of nearly 6 to 6.3 km per second. The lowest layer of the crust ( about 10 km thick ) has significantly higher P velocities, ranging up to nearly 7 km per second.

In the deep ocean there is a sedimentary layer that is about 1 km thick. Underneath is the lower layer of the oceanic crust, which is about 4 km thick. This layer is inferred to consist of basalt that formed where extrusions of basaltic magma at oceanic ridges have been added to the upper part of lithospheric plates as they spread away from the ridge crests. This crustal layer cools as it moves away from the ridge crest, and its seismic velocities increase correspondingly.

Below Earth’s mantle at its ‘thickest point’ exists a shell depth of 1,800 miles ( 2,255 km ), which seismic waves indicate, has liquid property form, and at Earth’s ‘shallowest point’ only 6-miles ( 10 kilometers ) located beneath the ultra-deep seafloor of the planet ocean.

At the very centre of the planet is a separate solid core with a radius of 1,216 km. Recent work with observed seismic waves has revealed three-dimensional structural details inside the Earth, especially in the crust and lithosphere, under the subduction zones, at the base of the mantle, and in the inner core. These regional variations are important in explaining the dynamic history of the planet.

Long-Period Global Oscillations

Sometimes earthquakes can be so great, the entire planet Earth will vibrate like a ringing bell’s echo, with the deepest tone of vibration recorded by modern man on planet Earth is a period of measurement where the length of time between the arrival of successive crests in a wave train has been 54-minutes considered by human beings as ‘grave’ ( an extremely significant danger ).

Knowledge of these vibrations has come from a remarkable extension in the ‘range of periods of ground movements’ now able to be recorded by modern ‘digital long-period seismographs’ spanning the entire allowable spectrum of earthquake wave periods, from: ordinary P waves ( with periods of tenths of seconds ) to vibrations ( with periods on the order of 12-hours and 24-hours ), i.e. those movements occuring within Earth ocean tides.

The measurements of vibrations of the whole Earth provide important information on the properties of the interior of the planet. It should be emphasized that these free vibrations are set up by the energy release of the earthquake source but continue for many hours and sometimes even days. For an elastic sphere such as the Earth, two types of vibrations are known to be possible. In one type, called S modes, or spheroidal vibrations, the motions of the elements of the sphere have components along the radius as well as along the tangent. In the second [ 2^nd ] type, which are designated as T modes or torsional vibrations, there is shear but no radial displacements. The nomenclature is _nS_l and _nT_l, where the letters n and l are related to the surfaces in the vibration at which there is zero motion. Four ( 4 ) examples are illustrated in the figure. The subscript n gives a count of the number of internal zero-motion ( nodal ) surfaces, and l indicates the number of surface nodal lines.

Several hundred types of S and T vibrations have been identified and the associated periods measured. The amplitudes of the ground motion in the vibrations have been determined for particular earthquakes, and, more important, the attenuation of each component vibration has been measured. The dimensionless measure of this decay constant is called the quality factor Q. The greater the value of Q, the less the wave or vibration damping. Typically, for _oS₁₀ and _oT₁₀, the Q values are about 250.

The rate of decay of the vibrations of the whole Earth with the passage of time can be seen in the figure, where they appear superimposed for 20 hours of the 12-hour tidal deformations of the Earth. At the bottom of the figure these vibrations have been split up into a series of peaks, each with a definite frequency, similar to that of the spectrum of light.

Such a spectrum indicates the relative amplitude of each harmonic present in the free oscillations. If the physical properties of the Earth’s interior were known, all these individual peaks could be calculated directly. Instead, the internal structure must be estimated from the observed peaks.

Recent research has shown that observations of long-period oscillations of the Earth discriminate fairly finely between different Earth models. In applying the observations to improve the resolution and precision of such representations of the planet’s internal structure, a considerable number of Earth models are set up, and all the periods of their free oscillations are computed and checked against the observations. Models can then be successively eliminated until only a small range remains. In practice, the work starts with existing models; efforts are made to amend them by sequential steps until full compatibility with the observations is achieved, within the uncertainties of the observations. Even so, the resulting computed Earth structure is not a unique solution to the problem.

Extraterrestrial Seismic Phenomena

Space vehicles have carried equipment onto the our Moon and Mars surface recording seismic waves from where seismologists on Earth receive telemetry signals from seismic events from both.

By 1969, seismographs had been placed at six sites on the Moon during the U.S. Apollo missions. Recording of seismic data ceased in September 1977. The instruments detected between 600 and 3,000 moonquakes during each year of their operation, though most of these seismic events were very small. The ground noise on the lunar surface is low compared with that of the Earth, so that the seismographs could be operated at very high magnifications. Because there was more than one station on the Moon, it was possible to use the arrival times of P and S waves at the lunar stations from the moonquakes to determine foci in the same way as is done on the Earth.

Moonquakes are of three types. First, there are the events caused by the impact of lunar modules, booster rockets, and meteorites. The lunar seismograph stations were able to detect meteorites hitting the Moon’s surface more than 1,000 km (600 miles) away. The two other types of moonquakes had natural sources in the Moon’s interior: they presumably resulted from rock fracturing, as on Earth. The most common type of natural moonquake had deep foci, at depths of 600 to 1,000 km; the less common variety had shallow focal depths.

Seismological research on Mars has been less successful. Only one of the seismometers carried to the Martian surface by the U.S. Viking landers during the mid-1970s remained operational, and only one potential marsquake was detected in 546 Martian days.

Historical Major Earthquakes

Major historical earthquakes chronological listing in table ( below ).

 

ARTICLE

AdditionalReading

Earthquakes are covered mainly in books on seismology.

Recommended introductory texts, are:

Bruce A. Bolt, Earthquakes, 4th ed. (1999), and Earthquakes and Geological Discovery (1993); and,

Jack Oliver, Shocks and Rocks: Seismology and the Plate Tectonics Revolution (1996).

Comprehensive books on key aspects of seismic hazards, are:

Leon Reiter, Earthquake Hazard Analysis – Issues and Insights (1990); and,

Robert S. Yeats, Kerry Sieh, and Clarence R. Allen, The Geology of Earthquakes (1997).

A history of discrimination, between:

Underground nuclear explosions and natural earthquakes, is given by:

Bruce A. Bolt, “Nuclear Explosions and Earthquakes: The Parted Veil” ( 1976 ).

More advanced texts that treat the theory of earthquake waves in detail, are:

Agustín Udías, Principles of Seismology (1999);

Thorne Lay and Terry C. Wallace, Modern Global Seismology (1995);

Peter M. Shearer, Introduction to Seismology (1999); and,

K.E. Bullen and Bruce A. Bolt, An Introduction to the Theory of Seismology, 4th ed. (1985).

LINKS

Year in Review

Britannica provides coverage of “earthquake” in the following Year in Review articles.

Bhutan  ( in  Bhutan )

geophysics  ( in  geophysics )

Japan

Kyrgyzstan  (in  Kyrgyzstan)

Nepal  (in  Nepal)

New Zealand  (in  New Zealand )

Chile  (in  Chile: Year In Review 2010)

China  (in  China: Year In Review 2010)

“Engineering for Earthquakes”  ( in  Engineering for Earthquakes: Year In Review 2010 (earthquake) )

geophysics  (in  Earth Sciences: Year In Review 2010)

Haiti  (in  Haiti: Year In Review 2010; in  Haiti earthquake of 2010 )

Mauritius  (in  Mauritius: Year In Review 2010)

New Zealand  (in  New Zealand: Year In Review 2010 )

Bhutan  (in  Bhutan: Year In Review 2009)

Costa Rica  (in  Costa Rica: Year In Review 2009 )

geophysics  (in  Earth Sciences: Year In Review 2009)

Indonesia  (in  Indonesia: Year In Review 2009)

Italy  (in  Italy: Year In Review 2009; in  Vatican City State: Year In Review 2009 )

Samoa  (in  Samoa: Year In Review 2009)

“Major Earthquake Shakes China’s Sichuan Province, A”  ( in  A Major Earthquake Shakes China’s Sichuan Province: Year In Review 2008 (earthquake) )

China  (in  China: Year In Review 2008; in  United Nations: Year In Review 2008 )

Congo, Democratic Republic of the  (in  Democratic Republic of the Congo: Year In Review 2008)

geology  (in  Earth Sciences: Year In Review 2008)

geophysics  (in  Earth Sciences: Year In Review 2008 )

geophysics  (in  Earth Sciences: Year In Review 2007)

paleontology  (in  Life Sciences: Year In Review 2007)

Peru  (in  Peru: Year In Review 2007 )

geophysics  (in  Earth Sciences: Year In Review 2006)

glaciers  (in  Earth Sciences: Year In Review 2006)

Mozambique  (in  Mozambique: Year In Review 2006)

archaeology  ( in  Anthropology and Archaeology: Year In Review 2005 )

geophysics  (in  Earth Sciences: Year In Review 2005)

India  (in  India: Year In Review 2005 )

Pakistan(in  Pakistan: Year In Review 2005 )

“Cataclysm in Kashmir”  (in  Cataclysm in Kashmir: Year In Review 2005 (Jammu and Kashmir))

geophysics  (in  Earth Sciences: Year In Review 2004)

Japan  (in  Japan: Year In Review 2004)

tsunami  (in  The Deadliest Tsunami: Year In Review 2004 (tsunami))

geophysics  (in  Earth Sciences: Year In Review 1996)

geophysics  (in  Earth and Space Sciences: Year In Review 1995)

LINKS

Other Britannica Sites

Get involved Share

Articles from Britannica encyclopedias for elementary and high school students.

Earthquake – Children’s Encyclopedia ( Ages 8-11 ) - During an earthquake, huge masses of rock move beneath the Earth’s surface and cause the ground to shake. Earthquakes occur constantly around the world. Often they are too small for people to feel at all. Sometimes, however, earthquakes cause great losses of life and property.

Earthquake – Student Encyclopedia ( Ages 11 and up ) - Sudden shaking of the ground that occurs when masses of rock change position below Earth’s surface is called an earthquake. The shifting masses send out shock waves that may be powerful enough to alter the surface, thrusting up cliffs and opening great cracks in the ground.

The topic earthquake is discussed at the following external Web sites.

Citations

To cite this page: MLAAPAHarvardChicago Manual of Style

MLA Style: “earthquake.” Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 21 Mar. 2012. http://www.britannica.com/EBchecked/topic/176199/earthquake

Reference

http://www.britannica.com/EBchecked/topic/176199/earthquake/247989/Shallow-intermediate-and-deep-foci?anchor=ref105456

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Feeling ‘educated’? Think you’re out-of the earthquake and tsunami water subject?

March 23, 2012 news, however contradicts decades of professional scientific knowledge and studies so, if you were just feeling ‘overly educated’ about earthquakes and tsunamis – don’t be. You’re now lost at sea, in the same proverbial ‘boat’, with all those global government scientific and technical ( S&T ) professionals who thought they understood previous information surrounding earthquakes and tsunamis.

After comparing Japan 9.0 ‘earthquake directional arrows’, depicted on the charts ( further above ), with ocean currents, tidal charts and trade winds from the global jet stream there’s a problem that cannot be explained when on March 23, 2012 British Columbia, Canada reported its northwest Pacific Ocean coastal sea waters held a 100-foot fishing boat ‘still afloat’ – more than 1-year after the Japan tsunami from its 9.0 earthquake on March 11, 2011.

[ IMAGE ( above ): 11MAR11 Japan 9.0 earthquake tsunami vistim fishing boat ( 50-metre ) found more than 1-year later still adrift in the Pacific Ocean - but thousands of miles away - off North America Pacific Ocean west coastal territory of Haida Gwaii, British Columbia, Canada ( Click on image to enlarge ) ]

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Source: CBS News – British Columbia ( Canada )

Tsunami Linked Fishing Boat Adrift Off B.C.

Nobody Believed Aboard 50-Meter Vessel Swept Away In 2011 Japanese Disaster CBC News

March 23, 2012 21:35 ( PST ) Updated from: 23MAR12 18:59 ( PST )

A Japanese fishing boat that was washed out to sea in the March 2011 Japanese tsunami has been located adrift off the coast of British Columbia ( B.C. ), according to the federal Transport Ministry.

The 50-metre vessel was spotted by the crew of an aircraft on routine patrol about 275 kilometres off Haida Gwaii, formerly known as the Queen Charlotte Islands, ministry spokeswoman Sau Sau Liu said Friday.

“Close visual aerial inspection and hails to the ship indicate there is no one on board,” Liu said. “The owner of the vessel has been contacted and made aware of its location.”

U.S. Senator Maria Cantwell, ofWashington, said in a release that the boat was expected to drift slowly southeast.

“On its current trajectory and speed, the vessel would not [ yet ] make landfall for approximately 50-days,” Cantwell said. Cantwell did not specify where landfall was expected to be.

First large debris

The boat is the first large piece of debris found following the earthquake and tsunami that struckJapanone year ago.

Scientists, at the University of Hawaii say a field of about 18,000,000 million tonnes of debris is slowly being carried by ocean currents toward North America. The field is estimated to be about 3,200 kilometres long and 1,600 kilometres wide.

Scientists have estimated some of the debris would hit B.C. shores by 2014.

Some people on the west coast of Vancouver Island believe ‘smaller pieces of debris have already washed ashore there’.

The March 11, 2011, tsunami was generated after a magnitude 9.0 earthquake struck off the coast of northern Japan. The huge waves and swells of the tsunami moved inland and then retreated back into the Pacific Ocean, carrying human beings, wreckage of buildings, cars and boats.

Nearly 19,000 people were killed.

Reference

http://www.cbc.ca/news/canada/british-columbia/story/2012/03/23/bc-fishing-boat-tsunami-debris.html?cmp=rss

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Submitted for review and commentary by,

Concept Activity Research Vault
E-MAIL: ConceptActivityResearchVault@Gmail.com
WWW: http://ConceptActivityResearchVault.WordPress.Com

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