The Sargent-Berrocal Fault Zone and its relation to the San Andreas Fault system in the southern San Francisco Bay region and Santa Clara Valley, California

The Sargent-Berrocal fault zone is a belt of thrust faults extending for about 58 mi (94 km) southeastward from the vicinity of Los Altos to San Juan Bautista, Calif. The fault zone generally dips southwestward toward the adjacent San Andreas fault at low to steep angles, and the southwest block has moved upward and northeastward. Thrusting across the fault zone has produced large-scale offset, which may increase to the southeast. If strike-slip movement has occurred, it has probably been minor. Offset Quaternary strata, physiographic features, and recent seismic activity all indicate that the Sargent-Berrocal fault zone has been active in the last one million years and that some clastic strain is currently being released along the northwest and southeast parts of the fault zone.