Three-Dimensional Seismic-Velocity Model for the Unconsolidated Mississippi Embayment Sediments from H/V Ambient Noise Measurements

The horizontal-to-vertical (H/V) technique by Nakamura (1989) was applied to data from 30 new field stations and 64 other broadband temporary and permanent seismic stations within the Mississippi Embayment of the central United States to develop a 3D model of unconsolidated sediment shear-wave velocity structure. Using the Dart (1992) map of sediment thickness as a basis, two self-consistent models of average shear-wave velocity versus sediment thickness were developed by utilizing the theoretical linear relationship between the frequency of the H/V peak and shear-wave velocity. One model was based on the observation that the H/V peak period T-p (s) versus sediment thickness h (m) was seen to be approximately linear with the relationship T-p = 0.003266h + 1.084. The second model was developed by considering peak frequency f(p) versus sediment thickness parameterized to follow ln f(p) = 8.325 x 10(-7) h(2) - 0.00232h - 0.01796. Overall, the models show low-average shear-wave velocity near the edge of the Mississippi Embayment with velocities increasing with increasing sediment thickness, consistent with increased sediment compaction. These models will be useful in studies of site resonance and amplification for earthquake-shaking hazards and for wave propagation computations for the region.