Map showing evidence for recent fault activity in the vicinity of Antioch, Contra Costa County, California

The U.S. Geological Survey, in cooperation with other federal, state, and local agencies, is studying active and potentially active faults in the counties surrounding San Francisco Bay as past of a program to define and clarify geologic hazards in the region.  Much more detailed information about known faults has been collected; in addition, poorly known or previously unknown zones of demonstrable or suspected active faulting have been delineated.  Documentation of these zones is of immediate importance because of both their scientific and social impacts.