Hi Chris. The following is a study done by

Gary D. Simpson
William R. Lettis
William Lettis & Associates
Suite 262
1777 Botelho Dr
Walnut Creek CA 94596

Stephen C. Thompson
Department of Geological Sciences
University of Washington
Seattle WA 98195

J. Stratton Noller
Vanderbilt University
Dept of Geology
PO Box 56 Station B
Nashville TN 37235

Hope you enjoy. Take Care…Don in creepy town

The San Gregorio fault is the principal fault west of the San Andreas fault in central coastal California, yet it remains the largest known active fault in the region whose seismogenic potential is not known. In this study, we integrate traditional paleoseismic and archaeologic investigations to define the location, style, and timing of slip events on the northern San Gregorio fault at a site near Seal Cove in Moss Beach, CA. Our findings show that the on-land portion of the San Gregioio fault at Seal Cove is a late-Holocene active dextral slip fault. Trench excavations revealed a broad zone of faulting, at least 22-m-wide, consisting of five Holocene-active strands. These include a single mid-Holocene east-vergent reverse fault and four late-Holocene near-vertical strike-slip faults. The most recent event occurred after the deposition of a native California cooking hearth dated AD 1270 to AD 1400, bur prior to the arrival of Spanish missionaries ca. 1775. The penultimate event at the stie is less well contrained, but appears to have occurred between AD 630 and AD 1300. The penultimate event was associated with horizontal displacement on the order of 3 m, based on reconstruction of a thrust wedge within the fault zone. The geometry of midden deposits shows a 5 m (+6, -2) deflection along the projection of faults associated witht he most recent event (MRE). All or part of this deflection may be associated with the MRE. These displacements are consistent with Mw 7 to 7 1/4 earthquakes and show that the San Gregorio fault is an active seimogenic source that should be considered in seismic hazard assessments in the San Francisco Bay area

• San Gregorio Fault