CUSRA2021: A Radially Anisotropic Model of the Contiguous US and
surrounding regions by full-waveform inversion
Abstract
The lithospheric structure of the contiguous US and surrounding regions
is significant in revealing the historical tectonic deformations and
interactions between subducting slabs and cratons. In this paper, we
present a new radially anisotropic shear wave speed model of this
region, constrained by seismic full-waveform inversion. The new model
(named CUSRA2021) utilizes frequency dependent travel time measured from
waveforms of 160 earthquake events recorded by 5,280 stations. More
earthquakes located in contiguous US are incorporated to improve the
data coverage in eastern US. The final model exhibits clear and detailed
shear wave speed anomalies that correlate very well with tectonic units
such as North America Craton (high-Vs), Cascadia subduction zones
(high-Vs), Columbia Plateau (low-Vs), Basin and Range (low-Vs), etc. In
particular, the detail of the North America Craton beneath Illinois is
revealed, and the depth of high-Vs anomaly beneath the North America
Craton correlates well with S-to-P receiver function and SH reflection
studies. The radial anisotropy also shows a layering of Craton
lithosphere.