Glossary of terms used on map Explanation, within Pop-up Windows, and in Detailed Reports
Glossary terms used in definitions are shown in bold italics.

Age (on map Explanation)
See Structure Age.

Age of Faulted Surficial Deposits (heading in detailed report)
Age of the youngest deformed geologic deposit.

Average Strike (heading in detailed report)
Computed strike (in degrees) of the structure from geographic information system (GIS) data, calculated by averaging strikes along individual parts of the structure. May not correlate with overall trend or bearing of a straight line between structure endpoints. Designated NA (not applicable) where multiple traces have been grouped for purposes of description, and the GIS-calculated strike is not useful as an indication of structure trend. For structures that cross the state border, average strike includes the part in the adjacent state, if mapped.

County(s) and State(s) (heading in detailed report)
Names of county (or counties) and state (or states) in which the structure is located. If a structure is in more than one county/state, the county/state containing the majority of the structure is listed first.

Date and Compiler(s) (heading in detailed report)
Date of compilation or most recent update of the database record, and name and affiliation of individual(s) that contributed to the data compilation or update.

Dip (heading in detailed report)
Maximum angle that a planar geologic surface (such as a fault) is inclined relative to horizontal; measured in degrees. A horizontal surface has a dip of zero degrees, and a vertical surface has a dip of 90 degrees. The dip of a surface is always perpendicular to the strike of that surface.

Dip Direction (heading in detailed report)
General direction of a fault’s dip. If a marble could be released on the fault surface, it would roll along a line indicating the dip direction. In the database, dip direction is given in terms of eight primary compass directions: north (N), northeast (NE), east (E), southeast (SE), south (S), southwest (SW), west (W), northwest (NW).

Displacement
General term for the relative amount of fault movement (slip), and in particular, the specific amount of such movement as measured along a fault plane (for example, in a trench exposure of a fault). In Utah, nearly all active faults are normal faults (characterized by dip slip, where fault slip is dominated by vertical, rather than horizontal, movement), and the displacement reported is typically the amount of vertical displacement.

Faceted Spur
A planar geomorphic surface, resembling an inverted V, that truncates a spur (narrow ridge) as a result of stream, wave, or glacial erosion or, in particular, faulting; also known as a triangular facet or triangular spur.

Fault Name
Names given to faults in the database are subdivided into a four-part hierarchy—Fault Zone Name, Fault Name, Section Name, and Strand Name. A Fault Name is applied to faults that are not subdivided into named sections (equivalent to faults in the database that have an assigned structure number, but no letter).

Fault Zone Name
Names given to faults in the database are subdivided into a four-part hierarchy—Fault Zone Name, Fault Name, Section Name, and Strand Name. A Fault Zone Name is applied to faults comprising two or more named sections.

Glossary of terms used on map Explanation, within Pop-up Windows, and in Detailed Reports
Glossary terms used in definitions are shown in bold italics.

Geologic Setting (heading in detailed report)
General statement about the setting of the structure including regional geology, amount of total fault offset, and age of offset strata, where known.

Geomorphic (Geomorphology)
Pertaining to the form of the Earth or of its surface features.

Geomorphic Expression (heading in detailed report)
General description of geomorphic features associated with deformation, such as fault scarps, grabens, offset stream channels, and faceted spurs.

Graben
An elongate, downdropped block between two normal faults that dip toward each other.

Historic Earthquake (heading in detailed report)
Name and year of historical surface-faulting earthquake.

Holocene
The later of the two epochs that make up the Quaternary Period of geologic time, extending from about 11,700 years ago to the present.

ka
Symbol used to designate a geologic age (for example, the timing of a geologic event, such as an earthquake) in terms of thousands of years before the present; k = kilo (1000), a = annum (years). For example, “The earthquake occurred about 12,500 years ago” could be written as “The earthquake occurred about 12.5 ka.”

kyr
Symbol used to designate an interval of time (such as the recurrence interval of large earthquakes) in terms of thousands of years, without reference to the present; k = kilo (1000), yr = years. For example, “The average recurrence interval is about 1300 years” could be written as “The average recurrence interval is about 1.3 kyr.”

Length (heading in detailed report)
End-to-end length (straight-line distance between endpoints, in kilometers) of the surface trace of a structure from geographic information system (GIS) data. For structures that cross the state border, length includes the part in the adjacent state, if mapped.

Location (on map Explanation)
Mapping constraint that reflects how easily recognized and well located the structure is in the field:

• Well constrained (solid line)—Fault scarp is clearly detectable as a physical feature at the ground surface, or abundant structural geologic data clearly indicate folded surficial deposits; fault or fold-axis location can be mapped with a high degree of accuracy.
• Moderately constrained (dashed line)—Fault scarp is a subdued physical feature at the ground surface or is absent for a short distance, or sparse structural geologic data suggest folded surficial deposits; fault or fold-axis location can only be mapped with a moderate degree of accuracy.
• Inferred (dotted line)—Fault scarp is not evident as a physical feature at the ground surface for a significant distance, or surficial geologic deposits lack evidence of folding (faulted or folded deposits are buried/concealed); fault or fold-axis location can only be approximated.

Ma
Symbol used to designate a geologic age (for example, the timing of a geologic event, such as the crystallization of an igneous mineral) in terms of millions of years before the present; M = mega (1,000,000), a = annum (years). For example, “Faulting has displaced a 4.8 million-year-old lava flow” could be written as “Faulting has displaced a 4.8 Ma lava flow.”

Mapped Scale
Numerical value representing the scale of the original mapping of the structure (that is, in the source document from which information on the structure was compiled for this database). Scale is represented by a ratio that relates one unit of measure on the map (say, one inch) to the equivalent distance that the map unit of measure represents on the ground in real life. For example, a map scale of 1:24,000 indicates that one inch on the map represents an actual distance on the ground of 24,000 inches, or 2,000 feet. The ratio can be thought of as a fraction; larger scales are indicated by larger fractions (for example, 1:500) and smaller scales are represented by smaller fractions (for example, 1:500,000). Large-scale maps typically cover relatively small areas (site specific) at more detail, and small-scale maps typically cover relatively large areas (regional) and are more generalized. Many faults in the database were originally mapped at the relatively small scale of 1:100,000, whereas others were originally mapped at the relatively large scale of 1:24,000. Small-scale mapping has more potential for locational inaccuracy when viewed at high zoom levels on the interactive map.

Most Recent Prehistoric Deformation (heading in detailed report)
See Structure Age.

Glossary of terms used on map Explanation, within Pop-up Windows, and in Detailed Reports
Glossary terms used in definitions are shown in bold italics.

Name Comments (heading in detailed report)
Information on the source of the structure name, and any other names used in the past.

Offset
Informal term for the distance between two once-adjacent points on the ground now disrupted by fault movement. In Utah, where active fault movement is dominated by dip slip, offset typically refers to the vertical distance between the ground surface on the upthrown and downthrown sides of a faulted, formerly continuous geomorphic surface (for example, the ground surface of an alluvial fan).

Paleoseismic
Pertaining to prehistoric earthquakes. The geologic study of prehistoric earthquakes is referred to as paleoseismology.

Paleoseismology Studies (heading in detailed report)
Summary of detailed, site-specific paleoseismic studies (typically involving trenching) conducted on a fault. Study sites are identified by structure number, section letter (where applicable), and site number (e.g., 2351f-4).

Physiographic Province(s) (heading in detailed report)
Name of the physiographic province(s) in which the structure is located. If a structure is in more than one province, the province containing the majority of the structure is listed first.

Pleistocene
The earlier of the two epochs that make up the Quaternary Period of geologic time, extending from 2.6 million years ago (Ma) to 11,700 years ago. In a gross sense, the Pleistocene is characterized by glacial climatic conditions. (Note: In 2009, the International Union of Geological Sciences ratified a recommendation by the International Commission on Stratigraphy to redefine the base of the Quaternary—and by association, the base of the Pleistocene—from 1.8 Ma to 2.6 Ma.)

Quaternary
The most recent period of geologic time, extending from 2.6 million years ago (Ma) to the present. The Quaternary Period comprises the Holocene and Pleistocene Epochs. (Note: In 2009, the International Union of Geological Sciences ratified a recommendation by the International Commission on Stratigraphy to redefine the base of the Quaternary from 1.8 Ma to 2.6 Ma.)

Recurrence Interval (heading in detailed report)
Time interval between individual large earthquakes, based on the timing of fault movement or folding of the ground surface as determined from numerical dating (for example, radiocarbon [14C], optically stimulated luminescence [OSL], etc.). The time interval for which this recurrence is valid is shown in parentheses.

Reliability of Location (heading in detailed report)
Structure-location reliability (good or poor), based on mapped scale and emphasis on Quaternary geology. The particular sources of the digital traces used to compile the Utah Quaternary Fault and Fold Database are listed in the comments section. Source-map scales are given in the reference list.

Glossary of terms used on map Explanation, within Pop-up Windows, and in Detailed Reports
Glossary terms used in definitions are shown in bold italics.

Scarp
Steep slope formed directly from movement along a fault. In a large normal-faulting earthquake (where fault slip is dominated by vertical movement), the ground surface becomes vertically offset across the scarp.

Section
Generic term for a length of fault that is in some way distinct from, but related to, an adjacent length of fault. Typically, section boundaries are defined on the basis of fault geometry or geomorphology, such as a gap in surface faulting or a significant change in strike. Sections may or may not generate earthquakes independent of fault movement on other sections.

Section Name
Names given to faults in the database are subdivided into a four-part hierarchy—Fault Zone Name, Fault Name, Section Name, and Strand Name. A Section Name is applied to subdivisions of a fault zone (equivalent to faults in the database that have a letter appended to the structure number).

Segment
A length of fault characterized by synchronous rupture, for which paleoseismic data show that the timing of surface faulting differs from that of an adjacent length of fault. All fault segments can be generically referred to as sections, but not all sections have the requisite data to show that they rupture as independent segments.

Sense of Movement (heading in detailed report)
See Slip Sense.

Slip Rate
Rate of fault movement obtained when the amount of displacement or offset is divided by time interval; common units of measure are millimeters per year (mm/yr). In Utah, nearly all active faults are normal faults (characterized by dip slip, where fault slip is dominated by vertical, rather than horizontal, movement), and the slip rate reported is typically the vertical slip rate.

Slip-Rate Category (heading in detailed report)
Slip rates in the Utah Quaternary Fault and Fold Database are assigned to one of four categories: (1) >5 mm/yr, (2) 1–5 mm/yr, (3) 0.2–1 mm/yr, and (4) <0.2 mm/yr. Note that whereas the Quaternary Fault and Fold Database of the United States contains faults having slip rates of >5 mm/yr, Utah has no faults in this slip-rate category.

Slip Sense
Relative movement of the ground/rock on one side of a fault with respect to the other side; includes normal, reverse, thrust, right-lateral (dextral) strike slip, and left-lateral (sinistral) strike slip.

Strand Name
Names given to faults in the database are subdivided into a four-part hierarchy—Fault Zone Name, Fault Name, Section Name, and Strand Name. A Strand Name is applied to subdivisions of a fault or fault section.

Strike
Trend or bearing of an imaginary line marking the intersection of a planar geologic feature (such as a fault) with a horizontal surface. Strike is always perpendicular to the dip angle.

Structure Age
One of five time categories within which the most recent surface faulting or folding occurred, based on historical documentation or geologic evidence. The categories are (1) historical (<150 years), (2) latest Quaternary (<15,000 years), (3) late Quaternary (<130,000 years), (4) middle and late Quaternary (<750,000 years), and (5) Quaternary (<2.6 million years). Structure Class
Following the U.S. Geological Survey, faults and folds in the Utah Quaternary Fault and Fold Database are classified as either Class A or Class B.

• Class A structures are those for which geologic evidence indicates Quaternary deformation of tectonic origin. Movement on these structures results from regional crustal stresses, and the movement is typically accompanied by earthquakes.
• Class B structures are those for which geologic evidence indicates Quaternary deformation, but either the structure is likely too shallow to be a source of significant earthquakes, or the evidence for a tectonic origin is not strong enough for the structure to be classified as Class A. Class B structures, which include faults of uncertain earthquake potential, may be related to processes such as salt deformation and dissolution, landsliding, lateral spreading, or subsidence following volcanic activity.

Structure Number
Number assigned to the fault or fold, within the range specified by the U.S. Geological Survey for each state; for example, the Wasatch fault zone is identified as structure number 2351. Numbers given to fault sections (see also Section Name) consist of a structure number and an appended letter (a, b, etc.); for example, the Salt Lake City section of the Wasatch fault zone is identified as structure number 2351f.

Synopsis (heading in detailed report)
Summary of information for the structure, and indication of level of study. For sectioned faults, the synopsis includes a general discussion of the fault as a whole followed by a brief overview of the individual sections.

Tectonic
Relating to, causing, or resulting from structural deformation in the Earth’s crust.

Background

The Utah Quaternary Fault and Fold Database has its origins in the first statewide compilations of Quaternary faults and folds in Utah by Anderson and Miller (1979) and Hecker (1993). Hecker’s comprehensive database was updated and expanded in 2003 (Black and others, 2003) as Utah’s contribution to the development of the Quaternary Fault and Fold Database of the United States by the U.S. Geological Survey. The original organization of the 2003 Utah database followed guidelines set by Haller and others (1993) to be compatible with the national database, and the current Utah database maintains general compatibility with the current national database. The current Utah Quaternary Fault and Fold Database was compiled and attributed using Esri ArcGIS software.

Acknowledgments

The Utah Quaternary Fault and Fold Database was developed under a cooperative agreement between the Utah Geological Survey and U.S. Geological Survey, funded through the National Earthquake Hazards Reduction Program (NEHRP), contract numbers 07HQAG0003, G10AC0058, G13AC00007, and G15AC00017. The 2003 database, from which the current database is derived, was compiled by Bill Black, Gary Christenson, Michael Hylland, and Greg McDonald, from data in Hecker (1993) with few changes, under NEHRP award number 98HQGR1029.

We thank Kathleen Haller (USGS) and Michael Machette (USGS, retired) for assistance and advice in compiling the database, and for providing us with entries from the national database to use in our entries for faults that cross state lines. Richard Dart (USGS) and Susan Olig (Olig Seismic Geology, Inc.) provided digital files for particular faults, and Richard provided GIS database entries for fault length and average strike. Christopher DuRoss (USGS, formerly UGS) contributed updated database information for numerous faults, particularly with respect to consensus values recommended by the Utah Quaternary Fault Parameters Working Group. Steve Bowman (UGS) helped develop the schema used in the current database, and Marshall Robinson, Brian Swaner, and Christine Wilkerson (UGS) did web design and programming for the interactive map. UGS GIS analysts Gordon Douglass, Janine Jarva, James McBride, Lucas Shaw, Neil Storey, and Corey Unger contributed substantially at various stages of development of the database, as did interns Sofia Agopian and Tara Hansen.

References

Anderson, L.W., and Miller, D.G., 1979, Quaternary fault map of Utah: Long Beach, California, Fugro, Inc., 35 p., scale 1:500,000.

Black, B.D., Hecker, S., Hylland, M.D., Christenson, G.E., and McDonald, G.N., 2003, Quaternary fault and fold database and map of Utah: Utah Geological Survey Map 193DM, scale 1:500,000, CD.

Haller, K.M., Machette, M.N., and Dart, R.L., 1993, Maps of major active faults, Western Hemisphere, International Lithosphere Program (ILP), Project II-2—guidelines for U.S. database and map: U.S. Geological Survey Open-File Report 93-338, 45 p.

Hecker, S., 1993, Quaternary tectonics of Utah with emphasis on earthquake-hazard characterization: Utah Geological Survey Bulletin 127, 157 p., scale 1:500,000.

Contacts

GIS spatial data and attribute files: Gordon Douglass, GIS Analyst, 801-538-4810, gordondouglass@utah.gov

Geologic information for specific faults or folds: Michael Hylland, Senior Scientist, 801-537-3382, mikehylland@utah.gov

Role of the UGS in active-fault research and hazard reduction: Steve Bowman, Geologic Hazards Program Manager, 801-537-3304, stevebowman@utah.gov

Although this product represents the work of professional scientists, the Utah Department of Natural Resources, Utah Geological Survey, makes no warranty, expressed or implied, regarding its suitability for a particular use. The Utah Department of Natural Resources, Utah Geological Survey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product. The Utah Geological Survey does not guarantee accuracy or completeness of the data.

The locational accuracy of faults and fold axes shown on the interactive web map varies, and spatial error can be substantial when viewing structures at high zoom levels that were originally mapped at small scales. Therefore, the locations of faults and fold axes on the interactive map should be considered approximate. Depending on the ultimate needs of the user, a site-specific investigation by a qualified Utah-licensed Professional Geologist may be required to accurately locate a fault on a particular site.

The Utah Quaternary Fault and Fold Database contains information for characterizing active faults and folds in Utah for seismic-hazard analysis. The database is periodically updated to incorporate the results of new mapping and/or paleoseismic investigations; however, more-detailed fault traces and paleoseismic information may be available in recently published geologic maps and reports, so the database should not be considered exhaustive.