Frequently Asked Questions
- What is the citation for these data?
- How do I download fault data? Where is metadata?
- Do the fault colors mean anything?
- Are some California faults are missing?
- What is the relationship between Quaternary faults and earthquakes?
- Why are there earthquakes but so few Quaternary faults east of the Rocky Mountains?
- Why are there so many earthquakes and Quaternary faults in the Western United States?
- Why are there so many faults with the same name?
What is the citation for these data?
When you use this data, please provide proper acknowledgement. Because there are many contibutors to the database, the citation will depend on which data you are using. Please use the following format:
U.S. Geological Survey (and supporting agency if appropriate-see list below), 2006, Quaternary fault and fold database for the United States, accessed DATE, from USGS web site: http//earthquakes.usgs.gov/regional/qfaults/.
List of cooperators:
Alaska............ Alaska Department of Natural Resources
Arizona........... Arizona Geological Survey
California......... California Geological Survey
Colorado.......... Colorado Geological Survey
Idaho............... Idaho Geological Survey
Illinois.............. Illinois State Geological Survey,
Louisiana......... Louisiana Geological Survey
Montana.......... Montana Bureau of Mines and Geology
Nevada............ Nevada Bureau of Mines and Geology
New Mexico..... New Mexico Bureau of Mines and Mineral Resources
Texas.............. Texas Bureau of Economic Geology,
Utah................ Utah Geological SurveyFor example, I want to reference information I got about a fault in New Mexico on Jan 9, 2006.. My reference would look like:
U.S. Geological Survey and New Mexico Bureau of Mines and Mineral Resources, 2006, Quaternary fault and fold database for the United States, accessed Jan 9, 2006, from USGS web site: http//earthquake.usgs.gov/regional/qfaults/.
Recommended browser - Internet Explorer 7 or greater. Mozilla, Safari do not work well.
Using the Interactive Map Service, you can zoom (
) to an area of interest and extract (
) faults and fault areas on the map. Data are in geographic coordinates (lat/lon), in shapefile format, and zipped for download.
Note: Mac users may have problems. The Safari browser does not work well with the interactive maps; please try Firefox instead.
For more help with the interactive map service, please go to IMS Intro
If you want to the whole database, go to ftp://hazards.cr.usgs.gov/maps/qfault/ and download the latest "qfdata" file. The metadata document is also at that location.
Shapefiles are the standard GIS format for the USGS, but if you need lat/lon information in a text file format, you can use a third party software to extract the location coordinates. The third party software, shpdump, can be downloaded from http://dl.maptools.org/dl/shapelib/ .
A user sends this information:
Download the exe file shpdump.ex
Change the name of the attached file from shpdump.ex to shpdump.exeThe PC version is contained within: shapelib129_bin_win.zip .
This is a DOS program that must be run within a DOS window. Here's how it looks when it's run:C:\faults> dir
01/02/2006 05:49 PM 2,667 fltarc.dbf
01/02/2006 05:49 PM 2,156 fltarc.shp
01/02/2006 05:49 PM 204 fltarc.shx
08/30/2001 09:59 AM 57,344 shpdump.exeC:\faults>shpdump fltarc
Shapefile Type: Arc # of Shapes: 13File Bounds: ( -122.118, 37.663,0,0)
to ( -122.073, 37.712,0,0)Shape:0 (Arc) nVertices=7, nParts=1
Bounds:( -122.109, 37.698, 0, 0)
to ( -122.108, 37.700, 0, 0)
( -122.108, 37.698, 0, 0) Ring
( -122.108, 37.699, 0, 0)
( -122.108, 37.699, 0, 0)
( -122.108, 37.699, 0, 0)
( -122.109, 37.700, 0, 0)
( -122.109, 37.700, 0, 0)
( -122.109, 37.700, 0, 0)
etc.
Are some California faults are missing?
The database is incomplete in California, all faults are not shown. Expected completion date is unknown. When new data is added, we will add those names to the FAQ.
What is the relationship between Quaternary faults and earthquakes?
Earthquakes occur as a result of slip on faults in the Earth’s crust. If the earthquake forms (nucleates) deep in the crust or has a magnitude below about 6, the slip on the fault may be unable to reach the surface. Those earthquakes that occur at shallower depths or have greater magnitudes commonly form a rupture at the surface or cause other types of deformation, such as liquefaction features. It is these features that are the subject of our Quaternary fault and fold database. (Quaternary faults are those that have been recognized at the surface and which have moved in the past 1,600,000 years, the duration of the Quaternary epoch).
Why are there earthquakes but so few Quaternary faults east of the Rocky Mountains?
The answer is partly related to recognizing Quaternary faults and partly related to differences in geologic conditions in the areas east of and west of the Rocky Mountains.
First, many faults are present in the central and eastern U.S. (CEUS), but few of these faults have evidence of being active in Quaternary time. For example, if a fault is present only in pre-Quaternary rocks, then there may be no way to demonstrate Quaternary activity on the fault.
Second, the types and ages of strata and deposits at the surface in the CEUS are commonly different from those from the Rocky Mountains west. In late Quaternary time, large parts the CEUS were covered by massive continental glaciers, which buried the landscape with glacial till (coarse glacial debris) and outwash deposits (glacial debris transported by water), or by wind-blown deposits (silty “loess” or eolian sand). Many of these deposits are geologically very young, typically <15,000 years old. These young deposits can bury and conceal evidence of Quaternary fault movement that is older than these deposits.
Third, generally the rate of movement on CEUS faults is significantly less than that on faults in the western U.S. Slower rates of deformation mean that the evidence of Quaternary faulting will be subtler and is therefore, more likely to be missed, destroyed by erosion, or concealed by burial compared to areas having higher deformation rates. All of these factors contribute there being fewer Quaternary faults mapped east of the Rocky Mountains.
Some of the best evidence of strong prehistoric earthquakes in the CEUS is from liquefaction features (sand boils and dikes), which form as poorly consolidated, water-saturated sediment is forced to the surface by ground shaking. Although liquefaction features can tell us when and where strong earthquakes have occurred, they don’t usually provide information about which fault specifically generated the earthquake. Despite these problems and shortcomings, the distribution of historical earthquakes and the geologic evidence of prehistoric earthquakes provide a reasonable guide to the seismic hazard in much of the CEUS. (See also Where are the fault lines in the United States east of the Rocky Mountains?)
Why are there so many earthquakes and Quaternary faults in the Western United States?
This region of the United States has been tectonically active for at least the past 25 million years, in large part because it is close to the western boundary of the North American plate. The juxtaposition of the Pacific and North American plates has formed many faults in California that accommodate lateral motion between the plates.
North and east of California, the Basin and Range province between the Wasatch Mountains in Utah and the Sierra Nevada Mountains in eastern California is actively spreading and stretching westward. In New Mexico and west Texas, similar spreading has opened a north-south rift that starts in central Colorado and extends into northern Mexico.
The geologic conditions and plate tectonic setting in much of the Western U.S. has resulted in the region being underlain by relatively thin crust and having high heat flow, both of which can favor relatively high deformation rates and active faulting. In contrast, in the Central and Eastern U.S. (CEUS) the crust is thicker, colder, older, and more stable. Furthermore, the CEUS is thousands of miles from active plate boundaries, so the rates of deformation are low in this region. Nevertheless, the CEUS has had some rather large earthquakes in historical times, including a series of major earthquakes near New Madrid, Missouri in 1811-1812, a large earthquake near Charleston, S.C. in 1886, and the Cape Ann earthquake northeast of Boston in 1755.
Why are there so many faults with the same name?
Many faults are mapped as segments across an area - in the GIS database, each segment occurs as its own entity. Fault segments having the different value for name, number, code, or dip direction appear in the database as a unique entry. For example, the San Andreas fault has several fault segments, from letters a to h, and fault segment 1h has segments with age of last fault movement from historic (<150 years) to late Quaternary (<13,000 years), with dip direction from vertical to unspecified, and fault type from exposed to concealed.
Do the fault colors mean anything?
The colors used on the image maps ("map-based") represent individual faults. That is, all strands of a fault, of one or many lines in the map view, is drawn with one color in order to see the collection of lines which belong to a fault. On the Interactive Map, fault color represents age of last movement on the fault, from 1.6 million years ago to the present.
Fault area colors indicate unique fault regions on both the image maps and interactive map.
