Chain reaction activated separate fault zone in 2nd huge quake


Seismic experts believe a magnitude 7.3 quake that rocked southwestern Japan in the early hours of Saturday occurred on a separate fault zone from a massive temblor that struck barely a day earlier, and was triggered by a chain reaction involving a series of tremors.

The 1:25 a.m. earthquake, with the same intensity as the 1995 Great Hanshin Earthquake, was about 16 times as large as a magnitude 6.5 temblor that hit Kumamoto Prefecture Thursday night, the Japan Meteorological Agency said, describing the latest jolt as the main quake and the initial one as a foreshock.

The governmental Earthquake Research Committee concluded Friday that the magnitude 6.5 quake happened on the 81-kilometer-long Hinagu fault zone running along the central part of the island of Kyushu.

Shinji Toda, professor of earthquake geology at Tohoku University, said the 64-kilometer-long Futagawa fault zone located north of the Hinagu zone could have moved to cause the fresh quake.

The village of Minamiaso, where a major landslide occurred, and the city of Uto in Kumamoto, where the city hall was half destroyed, are located at either end of the Futagawa fault zone.

In the Kumamoto town of Mashiki, Takashi Nakata, professor emeritus of geomorphology at Hiroshima University, spotted a part of a fault exposed at the land surface. He said it is believed to have been caused by a slip on the Futagawa fault zone.

The agency also said there had been 252 quakes by 11 a.m. Saturday since the magnitude 6.5 temblor that occurred at 9:26 p.m. Thursday, with the number of such temblors hitting the second-highest since 1995.

Gen Aoki, head of the agency’s quake and tsunami monitoring department, said seismic activity has also been observed on the Beppu-Haneyama fault zone in Oita Prefecture, located east-northeast of the Futagawa zone, adding it may be related to a series of strong earthquakes in Kumamoto.

However, Takashi Azuma, a researcher of geomorphology at the National Institute of Advanced Industrial Science and Technology, warned monitoring of volcanic activity should be tightened.


  • 4


    The 01:25 a.m. earthquake, with the same intensity as the 1995 Great Hanshin Earthquake, was about SIXTEEN TIMES AS LARGE as a magnitude 6.5 temblor that hit Kumamoto Prefecture Thursday night

    That's big!!

  • 3

    Danny Bloom

    This is unprecedented. Prayers for the dead and the injured and the survivors.

  • -9


    The term in the headline " chain reaction", isn' t it rather used in a nuclear contents?

  • -12


    Numbers are skewed here. A magnitude 7 is double the strength of a magnitude 6.

  • 0

    Brian Wheway

    Ive been trying to find out on the internet how to work out how or what is 16 x the 6.5 on the richter scale, there is loads of complicated math's formula's but nothing for mr thick like me. either way 6.5 is going to shake a lot of dust from the top of the cupboards!!

  • 7


    Numbers are skewed here. A magnitude 7 is double the strength of a magnitude 6.

    No its not. Not even close. It's ten times bigger

  • 0


    Been watching the news from Kyushu on TV off and on all day today (Saturday). That place sure is rocking ... and more such action is predicted by the earthquake experts. Those people down there sure are braving it out. It seems that all major TV channels are almost constantly showing what's happening in central Kyushu.

    Just hope those tremors don't start moving up this way (toward Tokyo). We got enough shaking from the Iwate-Fukushima earthquakes five years ago.

  • 5


    pretty scary stuff down there, due to building codes and quick response from the authorities thankfully there isnt as many deaths. Unfortunately those old heavy roofs that are made to withstand typhoons are not so great at surviving earthquakes.

    Numbers are skewed here. A magnitude 7 is double the strength of a magnitude 6.

    actually no, the Richter scale is logrithmic scale of the amplitude, 1 hole number is ten times the previous in scale but actual energy released is a lot more.

  • 2


    The term in the headline " chain reaction", isn' t it rather used in a nuclear contents?

    No. It is proving to be rather appropriate in this case due to the number of known active faults running north-south and intersecting east-west in this area (what is known as the Beppu-Shimabara rift valley). That is why there have been some magnitude 5 quakes occurring in neighboring Oita as these jolts have triggered a chain reaction of quakes on some of these other active faults.

    That is why the experts have been coming onto many broadcasts and trying to explain how their conventional thinking may not apply in these series of quakes and why it may be active for awhile in terms of the possibility of more larger quakes happening over a wider area in this region (where some quakes may indeed be aftershocks related to the main temblor while others may be new ones on other faults in this zone), and why people need to take precaution.

    There was a time not very long ago when seismic experts would say that it would be a remote possibility of one earthquake triggering another in this manner. But that thinking has long gone out the window as they learned more about the different type of faults including all the smaller undiscovered ones that ended up being discovered as technology and surveying techniques improved (before, the thought process was that such faults were mostly visible but that was proven to be only partially correct).

    It's why they continue to find there are indeed active geologic faults actually running under some nuclear power plants in the country. What I mean is while they did perform extensive research before many of these plants were built, what was thought to be accurate before is constantly being proven to be only partially accurate based on our science, technology, and knowledge of those times.

    And this isn't unique to Japan as some of the NPP's in California are also in the same situation. Also, they are also finding that previous inactive faults can become active again due to large seismic activity. As I mentioned in the other article regarding the M7.3, our science is pretty good but we keep learning how much we don't know when nature does what it does.

    The Japan archipelago just happens to sit on several junction points (as well as a subduction zone) which just adds to the complexity when it comes to how seismically active it is compared to other locales on the ring of fire.

  • 0


    Moving goalposts a bit?

    Yesterday they said that the jolt on Thursday evening had been the big one, so we might get aftershocks for the next week or so, with a 20% chance of Shindo 6, and a 40% chance of Shindo 5, etc.

    Today we get a 7.3, and suddenly none of the previous statements make any sense, so they announce that no, the previous one was only a precursor, and today's was the big one, oh, and these aftershocks will go on for another month or so.

    Poor people of Kyushu. Be brave, we are with you!

  • 0

    Ron Barnes

    This terrible but Nature is stronger than any thing man can make pressures build up then take Innocent lives So sad for those that lost their lives and their next of kin To those that were injured i wish a speedy recovery .and a very safe and better future in a safer area.

  • 0


    Moving goalposts a bit?

    This isn't about moving goalposts. This is the reality of the unpredictable nature of earthquakes when it comes to what can be considered a foreshock versus aftershock. Back on March 9, 2011, there was an offshore M7.3 that struck off Miyagi and did cause a small tsunami.

    By all logic, a major earthquake like that would have been considered the primary since the historical data didn't show this particular subduction zone being one to generate great (M8+) quakes. Then 2 days later, the M9 happened with its epicenter in the same general area which unleashed that major tsunami (which happened to end up being larger than expected due to several previously unknown mechanics that were caused by how portions of Honshu ended up moving to the east and subsiding). And even that one, the initial magnitude was first pegged at an M7.9 before being revised upwards several times (M8.4, M8.8, and then M9) as the data was analyzed.

    The point is our science in this area is an ongoing learning process. I mean there was one seismic expert who was on NHK today stressing this point by cautiously stating that while this M7.3 is normally considered the upper end for this particular inland area, that this does not mean there could be another one (elsewhere) in this region that is larger. And this has nothing to do about trying to have an excuse to be correct either way.

    The science in this entire area is relatively new and while the experts have learned a lot in the past 50 years, when nature does its thing, it often times reveals that prior our prior knowledge did not get the complete picture. The fact that a modern society can even exist on this geologically active piece of land is a testament to how little modern historical data exists to how these geologic processes really do work in terms of the human timescale and our current day understanding of all the mechanics involved.

    It's also this increased knowledge that has allowed this geologically active place to be considered relatively safe and why there has been this general feeling that the Kyushu area is one of the safer places to live in Japan. Generally speaking, it is on a human timescale. But nature is going to do what it always does whenever it wants to and will often times reveal details that was missed earlier due to the lack of scientific evidence to confirm previous hypothesis and theories.

    The actual current activity in this region is disastrous yes and it is sad the amount of destruction and loss of life it has inflicted. But in the long run, it is going to end up proving to be valuable in terms of furthering our understanding of the dynamics involved in this seismically active area (and also more specifically this particular area).

  • -3


    somebody must hv said this somewhere but i'll say it again here... keep the nuclear power plants off and stay that way indefinitely.

  • -2

    Kobe White Bar Owner

    Im confused how some1 thumbed down SYEINNYVES comment, is it not just logical with japan being the hub of global seismic activity, just look at Fukashima..... Also japan is a sun rich nation even in winter and solar panels are so affordable these days. Reminds me of the oil boys killing the first electric car. In the the east and the west profit is most important im sad to say, the people dont matter just the profits do in a fiat currency based on nothing. Weeping for the future and hoping for the best but i now have 3 prep kits ready. And like some1 said if you have camping gear have it on hand as it could save you ochili. Best to all.

  • 0

    Ambarish Pokhrel

    Solidarity with Japan. Japanese people are really strong. I know you'll able to face this disaster. You are amazing. Hugs from Nepal and Nepalese People.

  • 1

    Ganga B. Karmacharya

    My family and I my self have heartily Love and Respects to Japanese people and The nation JAPAN. Feel so sorry and sad of what happened, a big hugs from your always well wisher country Nepal.

  • 0

    Jordan Tanaka

    I'm in Kumamoto and I'd really appreciate some help finding any predictions about any more earthquakes to come. that one Thursday night shook us up quite a bit, but then it was supposed to be done. Then Saturday morning happened. My kids were crying before bed last night, because they were scared the 'scary music' (the incredibly unnerving early warning alarm broadcasted on the city wide speaker system) was going to start again.

    Some say its done, though we drove all the way down to Kagoshima-shi and there still wasn't any bread or bottled water of any kind left, which tells me people are freakin' terrified of more to come. Earthquakes weren't supposed to happen here!

    I know earthquakes can't be predicted, but aren't there seismic sensors or something placed all over? Can't they tell if the plates are still slipping or something?

    oh yay, another earthquake just now, as I write this. good gravy, when will there be peace?!

  • -2


    Numbers are skewed here. A magnitude 7 is double the strength of a magnitude 6.

    Typo- Meant ten times, not double.

  • -1


    Check the link I posted 6.5 and 7.3 releases nearly 16 times the energy

  • 0

    Tony W.

    ".....with the number of such temblors hitting the second-highest since 1995."

    "Temblors"? Would that be "Tremors"?

    "The term in the headline " chain reaction", isn' t it rather used in a nuclear contents"

    Jandworld, the term might have originated in nuclear physics, but like many other expressions originating in a special circumstance, it has passed into common usage, in this case wherever one event sets of a sequence of others, so here one earthquake triggered a second one.

  • 0



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