This research is to use long-period surface waves recorded at the TERRAscope (the very-broadband seismic network recently installed in southern California by the California Institute of Technology) to determine phase velocities in southern California. A well established method will be applied to these modern high-quality data. The period range of the previous measurements was limited to 27 seconds because of the limited quality of data. The new data set will extend the period range to 150 seconds. The increased period is critically important for exploring deep structures, that is, to a depth of 200 km. A better knowledge of these deep structures in the upper mantle will help understand the dynamics that controls the seismic activity and tectonic deformation presently taking place in southern California. This research is a component of the National Earthquake Hazard Reduction Program.
