Crustal Structure of the Western U.S. From Rayleigh and Love Wave Amplification Data

Surface wave amplification measurements have narrower depth sensitivity when compared to more traditional seismic observables such as surface wave dispersion measurements. In particular, Love wave amplification measurements have the advantage of strong sensitivity to the crust. For the first time, we explore the potential of Love wave amplification measurements to image crustal velocity in the western U.S. The effects of overtone interference, radial anisotropy and Moho depth are all explored. Consequently, we present SWUS-crust, a three-dimensional shear-wave velocity model of crustal structure in the western U.S. We use Rayleigh wave amplification measurements in the period range of 38–114 s, along with Love wave amplification measurements in the period range of 38–62 s. We jointly invert over 6,400 multi-frequency measurements using the Monte-Carlo based Neighborhood Algorithm, which allows for uncertainty quantification. SWUS-crust confirms several features observed in previous models, such as high-velocity anomalies beneath the Columbia basin and low-velocity anomalies beneath the Basin and Range province. Certain features are sharpened in our model, such as the northern border of the High-Lava Plains in southern Oregon in the middle crust.