SKS Splitting offshore California from ALBACORE

The development and evolution of the Pacific-North America plate boundary offshore Southern California is of great geodynamical interest. For better understanding, the Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) was initiated. ALBACORE is a network of 24 broadband and 10 short-period ocean bottom seismometers (OBSs) deployed across the southwestern region of the Pacific-North American plate boundary. Other than at scattered island stations present seismic array data ends at the coastline due to the difficulty of measurements further to sea. The experiment is intended to study many aspects of the Pacific-North American plate boundary. In this study we calculate SKS splitting parameters in an effort to measure the anisotropy of the region. The first step involved determining the orientations of each seismometer due to twisting during deployment. P wave arrivals are used and waveforms of each OBS are compared to nearby island stations of the California Seismic Network. The horizontal waveforms from the OBS's are rotated until the rotated components achieved maximum correlation with North and East components at a nearby station. The rotation angle is further constrained by particle motion. Once orientations are established, we calculate SKS splitting parameters by minimizing energy in the transverse component.