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Moho structure across the San Jacinto fault zone: insights into strain localization at depth

Meghan S. Miller, Panxu Zhang, David A. Okaya, & James F. Dolan

Published February 2014, SCEC Contribution #1755

Ten years of teleseismic earthquakes recorded by broadband seismic instruments 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 vertical offset of the Moho 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 are 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.

Miller, M. S., Zhang, P., Okaya, D. A., & Dolan, J. F. (2014). Moho structure across the San Jacinto fault zone: insights into strain localization at depth. Lithosphere, 6(1), 43-47. doi: 10.1130/L295.1.