WUS324: Full Waveform Inversion Approaching Convergence Improves
Waveform Fits While Imaging Seismic Structure of the Western United
States
Abstract
We report a new model of radially anisotropic crustal and upper mantle
structure of the western United States (WUS324) obtained from full
waveform inversion of earthquake data. We ran three multiscale inversion
stages beyond model WUS256 (Rodgers et al., 2022) allowing them to
approach convergence to fit a larger data set to a minimum period of 16
s. WUS324 is based on 324 total iterations from its starting model,
significantly more (16 times) than previous studies. Waveform misfit
reductions are 66-70% for both the inversion data and an independent
validation data set providing confidence in the predictive power of the
model. WUS324 provides much better fits and reveals shear wavespeed, vS,
structure of this large region with more detail than previous waveform
tomography models. It images high vS associated with oceanic lithosphere
and subducting slabs and low vS associated with magmatism in the crust
connecting to the mantle.