Geodolite measurements of deformation near Hollister, California, 1971--1978

Journal Article · Mon Dec 10 04:00:00 EST 1979 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB084iB13p07599· OSTI ID:5704387

Savage, J C; Prescott, W H; Lisowski, M; King, N

A 24-station trilateration network spanning the San Andreas and Calaveras faults near Hollister, California, has been surveyed each year between 1971 and 1978, inclusive. Two moderate (M/sub L/=5) earthquakes have occurred within the network during the interval. No convincing preseismic or coseismic anomalies associated with those earthquakes have been identified. The deformation of the network can be described roughly by rigid body motion of the three blocks bounded by the two faults with accommodation occurring by right-lateral strike slip on the San Andreas (13 +- 2 mm/a) and Calaveras (17 +- 2 mm/a) faults. The required slip rates are within the range of the observed fault creep on those faults. A more detailed analysis of the deformation indicates appreciable strain accumulation (0.4 ..-->..strain/a tensor shear) within the block lying between the San Andreas and Calaveras faults. Many of the featurs of the observed deformation can be produced by an elementary dislocation model, indicating that most of the deformation is associated directly with slip on the major faults. The network is not extensive enough to define uniquely the relative motion across the San Andreas fault system, but the data are consistent with a value of about 38 mm/a. The rate of deformation in 1971--1978 was not uniform but rather appears to have been higher than normal in 1973--1974 and lower than normal in 1975--1976.

• Research Organization: U.S. Geological Survey, Menlo Park, California 94025
• OSTI ID: 5704387
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 84:B13; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
DEFORMATION
EARTHQUAKES
GEOLOGIC FAULTS
GEOLOGIC FISSURES
GEOLOGIC STRUCTURES
GROUND MOTION
MOTION
NORTH AMERICA
SEISMIC EVENTS
SLIP
STRAIN RATE
USA
WESTERN REGION