A 3‐D model of the crust and uppermost mantle beneath the Central and Western US by joint inversion of receiver functions and surface wave dispersion

Abstract

AbstractRayleigh wave phase velocity maps from ambient noise and earthquake data are inverted jointly with receiver functions observed at 828 stations from the USArray Transportable Array west of 100°W longitude for data recorded in the years 2005 through 2010 to produce a 3‐D model of shear wave speeds beneath the central and Western US to a depth of 150 km. Eikonal tomography is applied to ambient noise data to produce about 300,000 Rayleigh wave phase speed curves, and Helmholtz tomography is applied to data following 1550 (Ms > 5.0) earthquakes so that Rayleigh wave dispersion maps are constructed from 8 to 80 s period with associated uncertainties across the region. Harmonic stripping generates back‐azimuth independent receiver functions with uncertainty estimates for each of the stations. A nonlinear Bayesian Monte Carlo method is used to estimate a distribution of shear wave speed (Vs) models beneath each station by jointly interpreting surface wave dispersion and receiver functions and their uncertainties. The assimilation of receiver functions improves the vertical resolution of the model by reducing the range of estimated Moho depths, improving the determination of the shear velocity jump across Moho, and improving the resolution of the depth of anomalies in the uppermost mantle. A great variety of geological and tectonic features are revealed in the 3‐D model that form the basis for future detailed local to regional scale analysis and interpretation.