CUSRA2021: A Radially Anisotropic Model of the Contiguous US and Surrounding Regions by Full-Waveform Inversion

The lithospheric structure of the contiguous US and surrounding regions offers clues into the tectonic history, including interactions between subducting slabs and cratons. In this paper, we present a new radially anisotropic shear wave speed model of the upper mantle (70-410 km) of the contiguous US and surrounding regions, constrained by seismic full-waveform inversion. The new model (named CUSRA2021) utilizes frequency-dependent travel time measurements, from 160 earthquake events recorded by 5,280 stations. The data coverage in eastern US is improved by incorporating more intraplate earthquakes. The final model exhibits clear and detailed shear wave speed anomalies correlating 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 detailed structure of the North America Craton beneath Illinois basin is revealed. The depth of high-Vs anomaly beneath the North America Craton correlates well with S-to-P receiver function and SH reflection results. Besides, the radial anisotropy in the Craton lithosphere shows a layering structure, which may relate to the process of lithospheric accretion and the origin of mid-lithosphere discontinuities.

Automated summary

This study presents a new shear wave speed model of the upper mantle in the contiguous US and surrounding regions, revealing the tectonic history and interactions between subducting slabs and cratons. The model exhibits clear shear wave speed anomalies correlating with tectonic units, including the North America Craton.