SKS Splitting beneath TriNet Stations in Southern California


Measurements of SKS phase splitting were obtained from about 80 broadband TriNet stations in southern California. The majority of the fast polarization directions are near E-W. The stations that are located a few km away from the San Andreas Fault also show E-W fast directions. The mean splitting time is about 1 second, which is consistent with an anisotropic layer of 120 km thick for 4 percent anisotropy. Stations on the Peninsular Ranges western of the San Andreas Fault show a mean fast direction of 85 ± 2.5 degrees and a mean splitting time of 1.2 ± 0.1 seconds. The Mojave block shows a fast direction of 80 ± 3 degrees and a splitting time of 0.9 ± 0.1 s. Several stations show clear evidence of azimuthal dependence of the splitting parameters. Those measurements are in general agreement with our earlier study using a combination of GSN and SCSN stations (Liu et al., 1995), and with other studies (e.g., Savage and Silver, 1993). The observed E-W fast directions are inconsistent with either the modern shear strain associated with the San Andreas Fault system, or the present-day absolute plate motion direction. The observed E-W fast directions could be either related to flow in the mantle caused by northward motion of the trailing edge of the Farallon plate, or the result of late Cenozoic N-S contraction.

Meeting Name

AGU Fall Meeting (2000: Dec. 15-19, San Francisco, CA)


Geosciences and Geological and Petroleum Engineering

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Article - Conference proceedings

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© 2000 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Dec 2000

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