Seismicity of the Livermore Valley, California region 1969-1979

Seismicity of the Livermore Valley, California, region for the 11-year period from 1969 through 1979 reveals a complex pattern of seismic strain energy release. Earthquake epicenters and focal mechanism solutions confirm the presence of numerous active faults in the region, all of which move in response to the regional stress field. A systematic evaluation of the relationship between the seismicity for this period and candidate faults leads to the classification of the Calaveras-Sunol, Concord, Greenville and Hayward faults as active faults. The Las Positas, Pleasanton and Verona faults are identified as probably active faults. The Livermore fault and the segment of the Williams fault located to the south of the Las Positas and Verona faults are classified as possibly active. However, a northern prolongation of the Williams fault said to exist to the north of the Las Positas and Verona faults is unsupported by seismological evidence. Additionally, the connection between the Livermore fault and northwest trending fault said to exist to the south of the Las Positas fault is also unsupported by seismological evidence.