Paleoseismology in the San Francisco Bay Area

Steps are dug as part of the trench at Tule Pond.

Tom Fumal, Jim Lienkamper and Tim Dawson of the USGS watch as steps are dug as part of the trench at Tule Pond (Tyson Lagoon), Hayward fault, Fremont, CA. photo by Jennifer Adleman, USGS.

We are currently exhuming several faults in the San Francisco Bay region in search of their ancient earthquake (paleoseismic) histories. The process involves digging a trench across (or along side) the fault in order to map, date and interpret disturbances in the soil layers (geologic strata) seen in the facing walls of the trench.