Systematic receiver function analysis of the Moho geometry in the southern California plate-boundary region

Tuesday, 16 December 2014
Yaman Ozakin and Yehuda Ben-Zion, University of Southern California, Los Angeles, CA, United States
We investigate the geometry of the Moho interface in the southern California region including the San Andreas fault (SAF), San Jacinto fault zone (SJFZ) and Elsinore fault(EF) with systematic analysis of receiver functions. The used data set consists of 145 teleseismic events recorded at 188 broadband stations throughout the region. The analysis utilizes a 3D velocity model associated with detailed double-difference tomographic results for the seismogenic depth section around the three major faults combined with a larger scale community model. A 3D ray tracing algorithm is used to produce effective 1D velocity models along each source-receiver teleseismic ray. Common Conversion Point (CCP) stacks are calculated using the set of velocity models extracted for each ray. The CCP stacks are analyzed with volumetric plots, maps of maximum CCP stack values, and projections along profiles that cross the major faults and other features of interest. The results indicate that the Moho geometry in the study area is very complex and characterized by large prominent undulations along the NE-SW direction. A zone of relatively deep Moho (~35-40 km) with overall N-S direction crosses the three major faults. A section of very thin Moho (~10 km) below and to the SE of the Salton Trough, likely associated with young oceanic crust, produces large Moho offsets at its margins. The observations also show vertical Moho offsets of ~8 km across the SAF and the SJFZ close to Cajon pass, and sections with no clear Moho phase underneath Cajon pass and adjacent to the SJFZ likely produced by complex local velocity structures in the brittle upper crust. We test and confirm the robustness of these features with respect to various parameters of the analysis procedure.