Poster #046, Seismology

Crustal Architecture of S. California Imaged by A 2-Layer H-K Stacking Method and Its Implications on Crustal Composition

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Poster Presentation

2020 SCEC Annual Meeting, Poster #046, SCEC Contribution #10671
The complex tectonic setting and fault system in California have produced a mosaic of crustal blocks for which their strength varies significantly across the region. To better quantify one of the most important factors that determine the crustal strength, the chemical, we construct a new map of Vp/Vs for the crystalline crust by applying a newly developed data processing scheme that involves a 2-layer H-k stacking of receiver functions. Preliminary results from this effort has allowed us to quantify the thickness and Vp/Vs for both the sedimentary layer and the underlying crystalline crust. In the resulting Moho topography map, high consistency is found when compared with the community veloc...ity model (CVM), showing the reliability of our results. For the crustal Vp/Vs ratio, a more complex pattern across the study region is found, differing from the modest values from the CVM. Particularly, the crust with high Vp/Vs (>1.8) is found beneath the Mojave Desert and the Peninsular Ranges, while a lower than average Vp/Vs (<1.65) is found in the crust of the Santa Maria Basin, Los Angeles Basin, and Salton Trough. In addition to the seismic properties, we further construct a 3-D compositional model for S. California by combining the Vp/Vs with the CVM using empirical relationship revealed by lab-measured seismic properties for crustal lithology. The resulting silica content model provides unique insights into the geological and thermal properties in Southern California, and also helps determine the strength of the crust as it provides an assessment to the existence of quartz, one of the weakest minerals in the crust. Additionally, the new pattern in Vp/Vs should help to calibrate future generations of CVM and to provide valuable constraints in future inversions for the seismic velocity structure of S. California.