Near‐surface expression of the eastern part of the San Cayetano Fault: A potentially active thrust fault in the California Transverse Ranges

Examined in this study are the near‐surface geometry, late Cenozoic geologic history, and seismic potential of the eastern part of the San Cayetano fault, a major north dipping thrust fault of the Transverse Ranges, California. The fault generally dips with a low angle close to the surface, but the dip increases up to 40° at about 5 km below sea level. The fault may become nearly horizontal at depth and root into a midcrustal detachment surface of the Transverse Ranges. The late Cenozoic reverse movement along the San Cayetano fault may have begun during the deposition of the lower part of the Saugus Formation. The fault has also moved after the deposition of the Saugus Formation within the last 0.2 m.y. The San Cayetano fault should be considered, at least, potentially active and may be capable of producing damaging earthquakes. This conclusion is based collectively on (1) the presence of several surficial geological features suggestive of recent movement along the fault, (2) the presence of microearthquakes on the fault plane, and (3) the structural similarity of the fault to seismically active north dipping thrust faults of the region.