Quaternary Map Introduction

This section of the Web site shows the distribution of Quaternary-active faults in the San Francisco Bay region and explains what they are, why they are important, and how geologists study them.

Quaternary-active faults are those that have slipped in Quaternary time (the last 1.8 million years). Geologists think that these faults are the most likely source of future great earthquakes, so it is important to know what they are, where they are, and how they work.

The map at the center of this part of the website shows Quaternary-active faults as differently colored lines on a computer-generated image of the region. This image combines LANDSAT satellite photography, digital elevation data, and digital water-depth data.

This fault map is derived from the ongoing work of the Northern California Quaternary Fault Map Database Task, which is a group of geologists from the U.S. Geological Survey, California Geological Survey, and consulting firms. Their work is to make and compile a modern map database of Quaternary fault information. They are largely funded by the USGS National Earthquake Hazards Program.

Note: The map on this Web site should not be used to evaluate potential earthquake hazards. It is intended for educational and general-interest purposes only.

This section of the website includes:

Maps - An on-line version of the Quaternary-active fault map with zoom and pan capabilities, along with photos and more information about the faults and earthquake history of 12 locations around the region.

About Quaternary Faults - Photos and more information faults, Quaternary time, and fault hazards.

Downloads - Downloadable versions of the Quaternary-active fault map poster for printing, on-screen viewing, and viewing the map in Google Earth.

Links - Links to other sites related to faults, earthquakes, and other geologic hazards of the region.