Poster #173, SCEC Community Models (CXM)

Joint MCMC Inversion of Rayleigh Wave Phase Velocity, Ellipticity, and Receiver Functions: Southern California Shear Velocity Model Expanding to the Shallower and Deeper Crust

Elizabeth Berg, Fan-Chi Lin, Vera Schulte-Pelkum, Konstantinos Gkogkas, & Hongrui Qiu
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Poster Presentation

2020 SCEC Annual Meeting, Poster #173, SCEC Contribution #10714 VIEW PDF
We provide a new isotropic shear velocity model of Southern California with sensitivity from the near-surface into the upper mantle, including resolving Moho depths. We accomplish this through Bayesian joint inversion of Rayleigh wave phase velocities, ellipticity measurements, and receiver functions at over 300 stations in Southern California from the Anza network and Southern California Seismic Network. We use continuous records from these stations for 2015 to obtain ambient noise cross-correlations that provide both phase velocity measurements, via Eikonal tomography for 2.5s-16s periods, and ellipticity measurements for 2s-26s periods. Additionally, we include phase velocity measurements... through Helmholtz tomography from Rayleigh waves generated by more than 350 regional and teleseismic events (Mw>3) for 15s-80s periods. The combined datasets expand the sensitivity range from previous studies to both shallower and deeper shear-velocity structure. Receiver functions in this area show particularly strong variations with backazimuth due to 3-dimensional heterogeneity and anisotropy. Since teleseismic event coverage used for receiver functions is azimuthally uneven, it will bias estimates of substation structure unless corrections for azimuthal variations are made. We include azimuthally-averaged radial receiver functions recorded across the networks to further constrain near-station subsurface structure, including the Moho. We leverage the complementary sensitivity of these datasets in a Markov Chain Monte Carlo joint inversion to provide quantified model uncertainty and understanding of sensitivity. We observe well-known large-scale features consistent with existing models in the overlapping region, such as prominent sedimentary layers in the Central Valley, Los-Angeles, San Bernardino, and Ventura basins.