SCEC Award Number 12235 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Steps in lithospheric thickness: Investigating strain localization at major strike slip faults in southern California
Investigator(s)
Name Organization
Meghan Miller University of Southern California Thorsten Becker University of Southern California James Dolan University of Southern California
Other Participants Panxu Zhang, USC
Louis Moresi, Monash University
SCEC Priorities 1b, 2d, 6a SCEC Groups Seismology, SDOT, CME
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 Ten years of teleseismic earthquakes recorded by broadband seismic data from the Anza network/USArray stations around the San Jacinto Fault were used to create P receiver function images of the lithospheric structure at this major strike-slip fault. Analysis of back azimuthal variation and location of the conversion points near the fault suggest an ~8 km Moho offset structure directly beneath the San Jacinto Fault. This implies that the fault extends through the entire crust and into the mantle lithosphere, supporting the idea that the strain in the lower crust is localized within a narrow zone. The Moho offset and surface trace of the San Jacinto fault zone is coincident with a compositional boundary in the Peninsular Ranges batholith previously identified in potential field geophysical data and Sr isotope analyses. The position of the offset with respect to this relict geologic feature, which predates the pluton emplacement that formed the batholith, may be a controlling factor in strain location and plate boundary fault initiation.
Intellectual Merit We have suggested that the San Jacinto Fault Zone developed along a near vertical crustal discontinuity within the Peninsular Ranges batholith, which extends through the entire crust. This relict, pre-pluton emplacement structure, which is defined by both geophysical and geochemical data, may have influenced the localization of strain and development of the relatively young SJFZ into its presence location.
Broader Impacts Graduate student Panxu Zhang worked on this project as her masters thesis. She graduated in September 2012. Graduate student Rachel Lippoldt has begun initial modeling (1D) to test the observations we have found seismologically.
Exemplary Figure Figure 2.
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