Pacific Coastal and Marine Science Center
Coastal and Marine Earthquake Studies
Central California/San Francisco Bay Earthquake Hazards Project, 1998
Fence in Bolinas offset by the San Andreas Fault during the 1906 earthquake.
The San Francisco Bay area is located in a broad zone of active crustal deformation driven by the motions of the North American and Pacific plates. Each year, about 5-6 cm (~2 inches) of relative plate motion must be accommodated in the Bay Area. During most years, at a given location only a small fraction of this motion occurs, and the rest is saved up, causing stress build-up. Geologic, geodetic, and geophysical studies show that plate motion is eventually released as slip along the San Andreas fault system, a complex group of sub-parallel faults (e.g., the San Gregorio-Hosgri, San Andreas, Hayward, Rodgers Creek, Concord, Green Valley, Calaveras, and numerous unnamed faults). Periodic seismic slip occurs when the stress build-up exceeds frictional resistance on these faults. Such slip can be dangerous and damaging as evidenced by the 1906 San Francisco and 1989 Loma Prieta earthquakes. The central California earthquake hazards project applies remote sensing techniques to study the subsurface and underwater geology of the San Francisco Bay area, where conventional geologic methods are impossible to apply.
Damage caused by the 1989 Loma Prieta Earthquake in San Francisco
Key to determining future earthquake hazards in the San Francisco region is understanding the physical processes that control the evolution of the San Andreas fault system. We are studying the structure of the Earth's crust in the San Francisco Bay area to:
This information is intended to aid earthquake preparedness in the San Francisco Bay area
New 3-D image of the crust beneath the San Francisco Bay area developed from monitoring the paths that earthquake waves pass through it. Colors correspond with different chunks of the Earth's crust that have been pushed together along the San Andreas and Hayward faults. Earthquakes are shown as yellow dots (see task 1 below for more description about how this model was developed).See full-size image (75 kb)
From: Parsons, T., and Zoback, M. L., Three-dimensional upper crustal velocity structure beneath San Francisco Peninsula, California, J. Geophys. Res. v. 102, p. 5473-5490.
We conducted four types of field studies:
Earthquakes in the San Francisco Bay area
Here is a list of related products.
Project Coordinator: Tom Parsons