Determining Structure and Velocity in the Los Angeles Region with Dense Seismic Arrays.

Abstract:

In the past four years there have been four 3D oil-company surveys in the Los Angeles region where the data has been recorded continuously for time periods of 3 weeks to 6 months. Ambient noise correlation with these data can be used to extract surface waves and body waves, which in turn allows us to determine the near-surface structure and velocities in the vicinity of these surveys. The results show a surprisingly short scale-length in the lateral variations of velocity, which is important for determining seismic hazard. To extend this analysis beyond the areas covered by the dense surveys themselves, we use the 16 stations of the Southern California Seismic Network (SCSN) broadband network that are located in the Los Angeles region, and which span the time-periods of the dense surveys to do C2 ambient noise correlations (correlations of correlations). This will extend the area covered to include most of the central Los Angeles Basin.