Stress- and structure-induced anisotropy in Southern California from two-decades of shear-wave splitting measurements

Zefeng Li, & Zhigang Peng

Submitted August 2, 2017, SCEC Contribution #7388, 2017 SCEC Annual Meeting Poster #027

We measure shear-wave splitting (SWS) parameters (i.e. fast direction and delay time) using 330,000 local earthquakes recorded by more than 400 stations of the Southern California Seismic Network (1995-2014). The resulting 232,000 SWS measurements provide a uniform and complete database of local SWS measurements in Southern California. The fast directions at many stations are consistent with regional maximum compressional stress directions σHmax. However, several regions show clear deviations from the σHmax directions. These include linear sections along the San Andreas Fault and the Santa Ynez Fault, geological blocks NW to the Los Angeles Basin, regions around the San Jacinto Fault, the Peninsular Ranges near San Diego, and the Coso volcanic field. These complex patterns show that regional stresses and active faults cannot adequately explain the upper crustal anisotropy in Southern California. Other types of local structures, such as local rock types or tectonic features, also play significant roles.

Citation
Li, Z., & Peng, Z. (2017, 08). Stress- and structure-induced anisotropy in Southern California from two-decades of shear-wave splitting measurements. Poster Presentation at 2017 SCEC Annual Meeting.


Related Projects & Working Groups
Seismology