LARGE SCALE EARTHQUAKE GROUND MOTION SIMULATIONS IN THE CENTRAL UNITED STATES

The Central United States (CUS), while distant from tectonic plate boundaries, hosts two of the major seismic zones east of the Rockies: the New Madrid and Wabash Valley Seismic Zones. Over the past 4500 years, the New Madrid Seismic Zone (NMSZ) has repeatedly produced sequences of major earthquakes, including several with magnitudes exceeding 7. The 1811-1812 winter events were the largest intraplate sequence historically recorded in United States. They produced great devastation in the region, which at that time was scarcely populated. Even though the seismicity in the eighteen hundreds was dominated by the NMSZ activity, large earthquakes in the last century have occurred in the Wabash Valley Seismic Zone (Bakun and Hopper, 2004). The population density and development of this area has drastically changed from that of the early nineteenth century, and a large earthquake would threaten the population and infrastructure of several states within the country’s heartland. In this study we present two sets of large scale numerical simulation scenarios of earthquakes in the CUS. These hypothetical scenarios are ruptures taking place in the axial arm of the NMSZ and the WVSZ. Our numerical realizations, valid up to 1.0 Hz, account for the heterogeneity of the region using a recently developed velocity model (CUSVM1) and use a minimum shear wave velocity of 300 m/s. We show that some combinations of hypocentral location and slip distributions have the potential to induce large ground motions in densely populated areas within the Mississippi Embayment and other areas within the CUS. In addition, we discuss the basin effects produced by the Mississippi embayment within the frequency band in which our simulations are performed, and compare with other sites where basin effects are prominent.