Community velocity model for the New Madrid region
The USGS has begun the development and construction of a community seismic velocity model to support general research in the New Madrid region as well as numerical simulations of earthquake rupture and seismic wave propagation due to a repeat of the 1811-1812 earthquakes. We have collected existing research regarding the p- and s-wave velocities, impedance contrasts and densities of the lithosphere in the New Madrid region and synthesized these results into a single model that can be used in earthquake simulations. We have identified areas of missing or incomplete information for further study.
The region covers an area of approximately 600,000 km2 from Little Rock, Arkansas across to Nashville Tennessee, up to St Louis, Missouri. The model has currently been gridded at 3 km lateral resolution and from 5-m resolution near the surface to 10-km resolution at 100 km depth. Less but still substantial uncertainty exists for the Mississippi Embayment where a majority of the research has been done. Newer regional models such as those by van der Lee and others and Liang and Langston have improved regional resolution beyond a 1-dimensional model, but for ground motion simulations, greater resolution outside the Embayment is desired.