Bedrock Accelerations in Memphis Area Due to Large New Madrid Earthquakes

Keywords: Infrastructures, Shelby County, Tennessee, Seismic Risk Assessment, New Madrid Seismic Zone (NMSZ), Lifeline Systems, Bedrock Motions, Seismology, Memphis, Tennessee, and Bedrock Acceleration.

Abstract: Memphis and Shelby County are geographically close to the southern segment of the New Madrid seismic zone (NMSZ). The NMSZ is being regarded by seismologists and earthquake engineers as the most hazardous zone in the eastern United States. In this study, a seismologically-based model is utilized to describe the horizontal bedrock motions at a site primarily due to shear waves generated from a seismic source. This model is centered on a power spectrum which is in turn developed from a seismologically-based Fourier amplitude spectrum. From the power spectrum, earthquake time histories and probability-based response spectra can be generated directly. The power spectrum generated in this study can also be used to estimate the peak value of earthquake acceleration based on the extreme value distribution of a random process. The peak values of horizontal bedrock accelerations for Memphis and Shelby County are computed for two New Madrid earthquakes of M = 7.5 and 6.5. Two different cases of seismic sources are considered: (1) a single source at Marked Tree, Arkansas, and (2) the southern segment of the NMSZ. The results are presented in contour maps.