The Relationship Between Upper Mantle Anisotropic Structures Beneath California, Transpression, and Absolute Plate Motions
نویسندگان
چکیده
We calculated SKS splitting parameters for the California Integrated Seismic Network. In southern California, we also estimated splitting in the upper 100 km using azimuthal anisotropy determined from surface waves. The inferred splitting from surface waves in the mantle lithosphere is small (on average <0.2 sec) compared with SKS splitting (1.5 sec) and obtains a maximum value (0.5 sec) in the transpressive region of the Big Bend, south of, and aligned with, the San Andreas Fault (SAF). In contrast, the SKS splitting is approximately EW and is relatively uniform spatially either side of the Big Bend of the SAF. These differences suggest that most of the SKS splitting is generated much deeper (down to 300400 km) than previously thought, probably in the asthenosphere. Fast directions align with
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