Lateral P-Velocity Gradients near Major Strike-Slip Faults in California

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Science  10 Jul 1981:
Vol. 213, Issue 4504, pp. 207-209
DOI: 10.1126/science.213.4504.207


The P-wave velocity in shallow crystalline rock decreases systematically from a normal value of about 5.5 kilometers per second 20 kilometers or more from the Garlock and San Andreas faults to less than 3 kilometers per second at distances of less than 2 kilometers from these faults. This lateral velocity gradient closely resembles the shear stress profile. It is proposed that the velocity gradient results from increased fracturing nearer these major strike-slip faults and that this fracturing dominates the response of the shallow crust to tectonic stress.