Geodetic measurement of crustal deformation on the San Andreas, Hayward, and Calaveras faults near San Francisco, California

Journal Article · Tue Nov 10 04:00:00 EST 1981 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB086iB11p10853· OSTI ID:5671834

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

Analysis of a geodetic network of 115 lines crossing the San Andreas, Hayward, and Calaveras faults in the vicinity of San Francisco Bay and measured repeatedly between 1970 and 1980 has revealed details about the accommodation of relative plate motion in this area. The most striking result is that the deformation is not uniformly distributed across the area. In the east bay, along the Hayward and Calaveras faults, all motion appears to take place as slip directly on the fault, with no accumulation of strain in the adjacent crust. On both the Calaveras and the Hayward faults the rate obtained for the 1970 to 1980 period agrees with geologic rates spanning a few million years and with creep rates spanning a few decades. The Hayward fault slip rate is 7 +- 1 mm/yr. The Calaveras fault slip rate is 7 +- 1 mm/yr, with perhaps half of this slip distributed across a zone a few kilometers wide, probably as inelatic deformation of weak near-surface material. The absence of strain accumulation in the east bay is surprising since the Hayward and Calaveras faults have been the site of large earthquakes in the past. A block located east of the Calaveras fault and south of the Las Positas fault has been rotating clockwise at the rate of 0.3 +- 0.1 ..mu..rad/yr with very little internal deformation. Along the San Francisco peninsula no detectable slip occurs (less than 1.5 mm/yr) at the surface, but appreciable strain is accumulating. Near fault shear strain rates are 0.6 +- 0.1 ..mu..strain/yr (engineering) with direction N47/sup 0/W +- 9. The slip rate near the San Andreas fault is 12.2 +- 3.9 mm/yr distributed across a broad zone. The relative motion across the whole region during the period 1970--1980 is 32.1 +- 7.4 mm/yr.

• Research Organization: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025; Rock Physics Project, Department of Geophysics, Stanford University, Stanford, CA 94305
• OSTI ID: 5671834
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 86:B11; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
CONTINENTAL CRUST
CREEP
DEFORMATION
EARTH CRUST
GEODETIC SURVEYS
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GROUND MOTION
MECHANICAL PROPERTIES
MOTION
NORTH AMERICA
PLATE TECTONICS
SLIP
STRAIN RATE
SURVEYS
TECTONICS
USA
WESTERN REGION