Abstract

The Mississippi Embayment overlies the New Madrid seismic zone in the central United States and consists of a thick succession of unconsolidated sediments that covers the Paleozoic basement rock. The high‐velocity contrast at the basement–sediment interface and the near‐vertical ray paths of teleseismic P‐waves generate very large P to S conversions on the radial component and large P reverberations on the vertical component. This characteristic of P‐wave propagation is used to study P‐ and S‐wave resonance in the sedimentary layer. Horizontal‐to‐vertical (H/V) and vertical‐to‐horizontal (V/H) power spectral ratios are calculated for a time window around the teleseismic P‐wave arrivals at broadband stations of the USArray Transportable Array, Northern Embayment Lithosphere Experiment, and the New Madrid Cooperative Seismic Network in the embayment. Using a map of sediment thickness, we developed models for average P‐ and S‐wave velocity‐versus‐sediment thickness. The resulting shear‐wave velocity model matches very well with the model obtained from an H/V ambient noise study in the region. The shear‐wave velocity model shows low velocity near the edges of the embayment with average velocities increasing with increasing sediment thickness, consistent with increased sediment compaction. Fundamental resonance frequency for S waves ranges from 0.2 to 0.4 Hz for the embayment sediments.

Electronic Supplement:Two figures showing the synthetic test results and a table that includes peak resonance frequency and average VP and VS.

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