Current seismic velocity models of the contiguous U.S and surrounding region are large-scale coherent but have discrepanies in small-scale structures. We (MSU computational seismology team) evaluate 9 models by comparing waveforms of data and synthetics (computed with SPECFEM3D). The waveform fitting result shows there is large gap for short period body and surface waves for improvement.

Contiguous U.S model evaluation

We started from an optimized hybrid model (INITCUS-2020, combined with US.2016 and CRUST1.0 in crust and S40RTS in mantle), with 160 events distributed in the study region. Source parameters are re-inverted for every 5 iterations with adjoint method. Travel time misfit function is applied in iterations 1-20 and waveform similarity misfit function is applied in iterations 21-25. The period range starts from 20-50 s/50 - 120 s and finally ends at 9-20 s.

We are currently at iteration 10. Cross-section shows clear Juan-de Fuca slab and reasonable lithospheric structure in the North American Craton.