This is consistent with extremely low estimates of shortening rates within the Coast Ranges and offshore.

The 3-5 mm/yr slip rate estimate suggests that the CRCV accommodates most of the total plate convergence between the North American and Pacific Plates at this latitude. The largest historical event attributed to the CRCV is the mainshock of the 1892 Vacaville-Winters earthquake sequence that may have been Mw 6.8. Given 21 to 23 segments, the historical record corresponds to recurrence intervals of about 400 to 700 years, for segments yielding Coalinga-size characteristic events, and slip rates of 3-5 mm/yr. Four of the characteristic events were comparable in size to the Coalinga earthquake, one was larger, and three were smaller. During the approximately 150 year period of historical record, 11 earthquakes of Mw 5.8-6.8, of which 8 may be characteristic events, have taken place on the CRCV. Based on this apparent segmentation, the average characteristic earthquake should be similar to the Mw 6.5 Coalinga event, with characteristic more » earthquakes of Mw 7 for the longest segments. The thrust system appears to be broken into 21-23 segments up to 80 km in length, with an average segment length of 20 km, based on geomorphology and seismicity. Estimates of CRCV slip rate derived from published studies range from 1-10 mm/yr, and recurrence intervals of Coalinga-type events range from 200-2,000 years. Recent studies have shown that the Coast Range-Central Valley geomorphic boundary, CA is underlain by a seismically active, blind fold and thrust belt, herein abbreviated as the CRCV. A major phase of basin formation appears to have been synchronous with a change in azimuth of relative shear between the Pacific and North American plates to a more westerly direction, resulting in extensional strain.

The Neogene basins in southern California began to develop during the interval in which the boundary between the Pacific and North American plates shifted from the continental edge to the San Andreas fault, apparently because the step-by-step switch to different surfaces of weakness caused local extension and compression within a broad zone of right-lateral shear. About 300 km of right slip has occurred along the San Andreas fault during the past 10 to 15 My), and at least several hundred additional kilometers along associated right-slip faults of the San Andreas system.

This shift seems to be documented by relations in the southern California area. Right slip between the Pacific and North American plates gradually shifted eastward to right-slip faults, such as the San Andreas, located farther inland. The initial position of the common boundary between the Pacific and North American plates was along the continental margin. The sliding margin developed more » in western California about 29 My ago, when the Pacific plate contacted North America after subduction of the intervening Farallon plate. The evolution of each of the Neogene basins is complex, but all can be considered products of an overall right-lateral shear system associated with a sliding margin between the Pacific and North American lithospheric plates. These deep, localized Neogene basins replaced broad, regionally persistent Paleogene depositional aprons, although some of the Neogene basins in northern and central California had Paleogene precursors. More than 90% of the known petroleum accumulations west of the San Andreas fault in California are in strata deposited in areally restricted Neogene basins that formed during a major tectonic reorganization of western California.

1990 california earth quake