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

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

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 inelastic 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 a rate of 0.3 ± 0.1 μrad/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 μstrain/yr (engineering) with direction N47°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.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Geodetic measurement of crustal deformation on the San Andreas, Hayward, and Calaveras faults near San Francisco, California
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/JB086iB11p10853
Volume 86
Issue B11
Year Published 1981
Language English
Publisher American Geophysical Union
Contributing office(s) Earthquake Science Center, Volcano Science Center
Description 17 p.
First page 10853
Last page 10869
Country United States
State California
Other Geospatial San Francisco Bay Area
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