U.S. Quaternary Fault and Fold Database Released

Kathleen M. Haller, Michael N. Machette, Richard L. Dart, and B. Susan Rhea, U.S. Geological Survey, Denver, Colo.

The U.S. Quaternary fault and fold database consists of searchable databases with related geospatial data that characterize faults, folds, and earthquake-related structures nationwide. The Web site, now available at http://Qfaults.cr.usgs.gov/, provides users with all pertinent, published information on potential seismogenic sources. Only those known or mapped faults that show geologic evidence of having been the source of large-magnitude, surface-deforming earthquakes (M > 6) during the Quaternary (since 1.6 Ma) are included. This is the first nationwide compilation to communicate current, comprehensive, geologically based information on known or suspected active faults.

Most previous compilations have shown faults in map view, but they have provided little supporting data [Witkind, 1975a, 1975b, 1975c, 1976; Howard et al., 1978; Johns et al., 1982; Nakata et al., 1982]. In contrast to those earlier efforts, this compilation and one by Hecker [1993] contain not only fault maps, but also the supporting geologic interpretations that capture the past behavior of the fault. Most important, the Quaternary fault and fold database of the United States is entirely digital and offers interactive online access.

Pertinent published information is conveyed in a uniform format on nearly 2000 faults nationwide, representing around 10,000 pages of text. An effort has been made to concisely report published information without injecting excessive interpretation beyond that of the original author. This release is possible because of the substantial cooperation from state geological surveys, academia, and the private sector over the past 10 years.

The Quaternary fault and fold database can be accessed via the Web through three distinct but highly powerful interfaces (Figure 1). Users can query the fault descriptions themselves or retrieve fault information through one of two map interfaces. Queries can be as simple as that of a name search or fault ID search, or may be as complicated as user-defined combinations of geographic location, fault activity parameters, and geologic characteristics.

Fig. 1. Views of Web pages in the Quaternary fault and fold database of the U.S. Web site are shown: (a) interactive map page, (b) detailed static map page, and (c) fault description.

The two map interfaces are tailored to address the needs of users having a variety of access speeds. A static-map interface was implemented for users who have low-speed Internet connections. The static map pages consist of small image files that show the location of faults on a digital base map; each page loads quickly in a Web browser. The user is initially presented with a view of the United States but can navigate to more detailed maps with the click of a mouse. Navigation arrows take the user to adjacent maps, and hyperlinks are provided to the fault descriptions.

The second map interface presents the same seismogenic structures shown, in the same detail, on an interactive map page. This interface is primarily intended for users who have high-speed Internet connections, and it provides an array of features not available on the static map pages. Faults depicted on the interactive map page are also linked to the appropriate fault description. Additional features that are offered include the ability to zoom and pan, to perform limited text and numeric searches, and the ability to download data for GIS applications. A great improvement over the static maps is the ability to readily differentiate ages of the faults. This is important because the timing of the most recent large-magnitude earthquake (shown by assigned color on the interactive map) is generally considered to be one of several fault characteristics that are suggestive of fault activity rates. Fault color on the static maps has no significance other than to delineate a group of traces.

The description of each fault is served in three different levels of detail. The least detailed view provides the user with simple, general information from just a few data fields. The most detailed view defines all published sources of important information that characterize fault activity, such as timing of the most recent surface rupturing earthquake, slip rate, recurrence rate, etc. In addition, the locations and findings of hundreds of paleoseismic investigations are documented.

The Quaternary fault and fold database is designed to fulfill the needs of a broad audience, from the general public to the science community. Scientific and technical professionals including those engaged in all aspects of seismological and paleoseismological research will find this a powerful tool. The Web site facilitates comparisons of spatial and temporal patterns of faulting at local, regional, and national scales, and provides critical input for modeling plate motion and regional strain distribution. In addition, paleoseismologists and earthquake geologists will be able to identify where trenching studies have been conducted, and view summaries of the results of those studies, thereby highlighting locations where more work may needed. Other geological specialists such as hydrologists can access the geospatial content to address issues of groundwater availability and hydrothermal potential.

An additional, important audience is the ever-growing seismic hazard assessment community. One pressing need of this community is the ability to identify and characterize faults that have likely produced strong ground motion in the geologically recent past and that may contribute to future seismic hazards. Incorporating fault characteristics into the analysis has become standard practice in contemporary probabilistic seismic-hazard assessments [i.e., Frankel et al., 1996, 2002]. Throughout much of the United States, characteristics of faults are poorly constrained, and it is generally the responsibility of the modeler to determine the values that will be used for slip rate, recurrence rate, and magnitude of the expected earthquake. Thus, having all pertinent published data readily available will improve future assessments by facilitating informed assignment of parameters. For the first time, scientists will have access to all pertinent data available on potential seismic sources, in one location, to characterize the faults modeled in their seismic-hazard assessments.

Many other professional and academic groups may use some parts of the information provided on this Web site. Obvious candidates include the earthquake-engineering community and the insurance industry. Local and state planners' needs are addressed by showing potential seismic sources on maps. Similarly, emergency response planners would benefit by knowing the locations of faults in their community that could disrupt life lines. All of these users can base their decisions on the state-of-the-art information that is offered.

Finally, the general public is becoming increasingly aware of potential hazards in their area. The U.S. Geological Survey as well as state geological surveys frequently are called upon to respond to questions regarding the locations of hazardous faults that may affect the lives of the population at large. Now, private individuals can find the answers to many of their questions directly in a user-friendly online interface.

The data compilation for the first release is complete for the lower 48 states, with the exception of parts of California and Idaho. Ongoing efforts to complete those states, as well as Alaska, Hawaii, and the U.S. territories, will proceed into 2005. The database will be periodically updated so it will remain the latest authoritative tool for fault characterization in seismic-hazard analysis.

We would like to express our deepest gratitude to the numerous individuals and their sponsoring institutions for their contributions to this effort over the past decade. Together, we have assembled a massive collection of data; without their time and dedication, this highly useful tool could not be realized today.

California Geological Survey - William A. Bryant, Sereyna E. Cluett, Earl W. Hart, Matthew J. Lundberg, and Jerome A. Treiman

Colorado Geological Survey - Robert M. Kirkham, Matt Morgan, William P. Rogers, and Beth L. Widmann

Montana Bureau of Mines and Geology - Mervin J. Bartholomew and Michael C. Stickney

Piedmont Geosciences, Inc. - Kenneth D. Adams, John A. Oswald, Janet E. Sawyer, and Thomas L. Sawyer

U.S. Geological Survey - R. Ernest Anderson, Richard J. Blakely, Thomas M. Brocher, Robert C. Bucknam, John Cox, Anthony J. Crone, Richard L. Dart, Peter J. Haeussler, Kathleen M. Haller, Suzanne Hecker, Richard W. Harrison, Margaret Hiza Redsteer, Katherine J. Kendrick, Samuel Y. Johnson, David J. Lidke, Michael N. Machette, Patricia McCrory, Karen Morgan, Alan R. Nelson, Steven F. Obermeier, Sue Perry, Stephen F. Personius, Kenneth L. Pierce, Thomas L. Pratt, Marith C. Reheis, Susan Rhea, Peter C. Rowley, Damon Sather, Eugene S. Schweig, Brian L. Sherrod, Kirk R. Vincent, Ray E. Wells, and Russell L. Wheeler

Utah Geological Survey - Bill D. Black, Gary E. Christenson, Janine Jarva, Michael D. Hylland, William R. Lund, James McBride , Greg N. McDonald, Barry J. Solomon, and Neil Storey

Frankel, A., C. Mueller, T. Barnhard, D. Perkins, E. V. Leyendecker, N. Dickman, S. Hanson, and M. Hopper (1996), National Seismic-Hazard Maps: Documentation, June 1996, U.S. Geol. Surv. Open-File Rep. 96-532, 71 pp., USGS, Reston, Va.

Frankel, A. D., et al. (2002), Documentation for the 2002 update of the national seismic hazard maps, U.S. Geol. Surv. Open-File Rep. 02-420, v 1.0, 36 pp., USGS, Reston, Va.

Hecker, S. (1993), Quaternary tectonics of Utah with emphasis on earthquake-hazard characterization, Utah Geol. Surv. Bull. 127, 157 pp., (6 pls., scale 1:500,000), Utah Geological Survey, Salt Lake City.

Howard, K. A., et al. (1978), Preliminary map of young faults in the United States as a guide to possible fault activity, U.S. Geol. Surv. Misc. Field Stud. Map MF-916, (2 sheets; scale 1:5,000,000), USGS, Reston, Va.

Johns, W. M., W. T. Straw, R. N. Bergantino, H. W. Dresser, T. E. Hendrix, H. G. McClernan, J. C. Palmquist, and C. J. Schmidt (1982), Neotectonic features of southern Montana east of 112E30' west longitude, Montana Bur. Mines Geol. Open-File Rep. 91, 79 pp. (2 sheets) Montana Bureau of Mines, Helena.

Nakata, J. K., C. M. Wentworth, and M. N. Machette (1982), Quaternary fault map of the Basin and Range and Rio Grande rift provinces, Western United States, U.S. Geol. Surv. Open-File Rep. 82-579, (2 sheets; scale 1:2,500,000), USGS, Reston, Va.

Witkind, I. J. (1975a), Preliminary map showing known and suspected active faults in western Montana, U.S. Geol. Surv. Open-File Rep. 75-285, 36 pp. (1 sheet, scale 1:500,000), USGS, Reston, Va.

Witkind, I. J. (1975b), Preliminary map showing known and suspected active faults in Idaho, U.S. Geol. Surv. Open-File Rep. 75-278, 71 pp. (1 sheet; scale 1:500,000) USGS, Reston, Va.

Witkind, I. J. (1975c), Preliminary map showing known and suspected active faults in Wyoming, U.S. Geol. Surv. Open-File Rep. 75-279, 35 pp. (1 sheet; scale 1:500,000), USGS, Reston, Va.

Witkind, I. J. (1976), Preliminary map showing known and suspected active faults in Colorado, U.S. Geol. Surv. Open-File Rep. 76-154, USGS, Reston, Va.