(past 1.6 m.y.) because this period of geologic 

time is most relevant for studies of active 

earthquake faults.

Earthquakes occur when faults move 

beneath the Earthʼs surface. When the earthquake is large enough, movement will continue up to the surface and produce scarps, 

folds, or other geologic evidence of ground 

deformation. Although not all future earthquakes will occur on known faults, virtually 

all occur on preexisting faults. Thus, the 

faults included in this database have the most 

potential for future large earthquakes and 

provide a fairly accurate picture of earthquake 

hazards in the United States.

Quaternary Faults

The Quaternary Fault and Fold 

Database includes information such as geologic setting, fault orientation, fault type, 

sense of movement, slip rate, recurrence 

(repeat) interval, and the time of the most 

recent surface-faulting event. Much of the 

information in the database is based on paleoseismology, which is the geologic study of 

prehistoric earthquakes. Paleoseismology 

combines geologic tools such as trenching 

with archeological-style analysis to determine 

the times and sizes of ancient earthquakes in 

the Quaternary Period. These studies extend 

the historic record of earthquakes and are 

extremely useful in assessing the potential 

hazard posed by the thousands of Quaternary 

faults in the United States. 

Interfaces

Three distinct but highly powerful interfaces can access the Quaternary Fault and 

Fold Database; each is tailored to different 

groups of users. There are two map interfaces. The U.S. Map interface (see below) 

is based on States or regions. Clicking on 

a State brings up the State map (Nevada is 

shown here), with all the 1°x 2° sheets for 

the State. Each sheet covers an area about 

120 miles wide (E.-W.) and 60 miles high 

(N.-S.). Clicking one of the sheets brings up 

a shaded relief map of the area showing all 

the Quaternary faults. Each of these faults is 

numbered and linked to text descriptions in 

a table that is below the map. The static map 

images are small (typically 30 kb), so they 

load quickly using a standard dial-up modem.

The second map interface is a dynamic 

one, which utilitizes ArcInfoʼs Interactive 

Map Service (IMS). This map is linked to 

digital fault-and-fold files in a GIS (geographic information system). The interface loads a 

base map of the United States and a series of 

user-controlled layers, such as streams, roads, 

and towns, as well as the Quaternary faults 

and folds. Special tools allow users to zoom, 

pan, query, and link to the database (see next 

page). This powerful interface requires highspeed Internet access.

Users can also query the database. Queries 

can be simple, such as fault name, or as complicated as user-defined combinations of location, 

fault activity, and geologic characteristics.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004-3033

March 2004

UNDERSTANDING EARTHQUAKE HAZARDS THROUGHOUT THE UNITED STATES

Printed on recycled paper

What are the faults in my area and where are they? 

When did they last have a large 

earthquake? Now you can find 

the answers to these questions 

online at http://Qfaults.cr.usgs.gov/ 

through a user-friendly interface 

developed by the U.S. Geological 

Survey (USGS). This is the first 

nationwide compilation to provide 

up-to-date and comprehensive 

geologically based information on 

known or suspected active faults.

The Database

The USGS has released a new 

Quaternary Fault and Fold Database that 

summarizes geologic, geomorphic, and 

geographic information for about 2,000 

Quaternary faults in the United States. This 

online database at http://Qfaults.cr.usgs.gov/

contains information on faults and associated folds that are believed to be sources of 

earthquakes greater than magnitude 6 (M>6). 

The database is limited to structures with 

documented activity during the Quaternary 

U.S. Map Interface

This series of windows shows the graphical 

map interface for the U.S. faults. Each page 

is relatively small (30 kb) and loads quickly 

in a Web browser. Faults are organized in 

1°x 2° map sheets by State or region.

Quaternary Fault and Fold Database for the Nation
Purpose and Uses

The database is designed to fulfill the 

needs of a broad group of users, ranging 

from the science community to the general 

public. Scientific and technical professionals engaged in seismological and paleoseismological research will find this Web site 

a powerful tool. The Web site facilitates 

making 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 review summaries of the 

results of those studies. Other geological 

specialists, such as hydrologists, can use it to 

address issues of ground-water availability 

and hydrothermal potential.

The seismic-hazard-assessment community will benefit from public access to all 

data available on potential earthquake sources 

in one location. The database will allow these 

users to identify faults that have likely produced strong ground motion in the geologically recent past and that may contribute to 

future seismic hazards. The database will continue to be the primary source for USGS seismic-hazards information on faults and faultrelated folds in the United States, providing 

geologic information on the probable sources 

of past, current, and future earthquakes.

Other potential users include the earthquake-engineering community, the insurance 

industry, and companies managing large 

infrastructures, such as pipelines or powertransmission networks. In addition, local 

and State planners can use the database to 

locate potential earthquake sources on maps. 

Similarly, emergency-response officials can 

use the database to plan earthquake drills and 

to identify and fortify critical infrastructure 

near active faults.

Finally, the general public is becoming 

increasingly aware of potential hazards in 

their environment. The USGS as well as State 

geological surveys frequently are called upon 

to respond to questions regarding the location 

of hazardous faults that may impact the lives 

of the population at large. Now individuals 

can find the answers to their questions directly in a user-friendly online interface.

Acknowledgments

Ten years in the making, this massive 

collection of data, which is estimated to 

contain about 10,000 pages of content on 

about 2,000 faults and folds (see below), 

was accomplished with the cooperation and 

assistance of State geological surveys as well 

as individuals in the academic and private 

sectors (see Web site for a complete list). 

Future additions to the database will include 

information for Alaska and Hawaii, as well as 

updates to information in the lower 48 States.

The work of the USGS and its cooperators in developing this database is only one 

part of the ongoing USGS efforts to protect 

lives and property from future earthquakes 

throughout the United States.

For More Information Contact:

Earthquake Hazards Program

U.S. Geological Survey

DFC PO Box 25046 MS-966

Denver, CO 80225

Quaternary Fault & Fold Database is at:

http://Qfaults.cr.usgs.gov/

Earthquake Hazards Program

http://earthquake.usgs.gov/

Written by Michael Machette, Kathleen Haller, 

and Lisa Wald

Graphics and layout design by Lisa Wald

This Fact Sheet is available online at 

 http://pubs.usgs.gov/fs/2004/3033

This window shows the GIS interface. Although powerful and having a variety of navigational 

tools, it is relatively large (>250 kb) and designed for users with high-speed Internet access.

GIS Map Interface

Example of a complete report for a Quaternary fault. These descriptions are typically 

2–5 pages long with references.

Database Information