Abstract

Unconsolidated, near‐surface sediments can have a profound influence on the amplitudes and frequencies of ground shaking at a site during earthquakes, and these effects should be taken into account in seismic hazard assessments. This study explores methods to use teleseismic arrivals recorded on linear receiver arrays to characterize widespread shallow sedimentary deposits, including estimation of the velocities, determination of fundamental resonance peaks, and imaging of the major reflectors. The examples used are the extensive Atlantic Coastal Plain (ACP) and associated Mississippi embayment (ME) strata of the central and eastern United States. The large contrast in material properties at the bedrock surface beneath these sediments produces a strong fundamental resonance peak in the 0.1 Hz and above frequency range. The frequency of the fundamental peak is estimated here by computing spectral ratios at each receiver site relative to bedrock sites at the ends of the receiver arrays. Sediment thicknesses derived from published contour maps made from drill‐hole data allow for estimation of average velocities to match the observed frequencies of resonance peaks with theoretical values at each receiver site, with the sloping bedrock surface allowing for computation of an average velocity versus depth function if horizontal layers are assumed. The velocity function is then used to convert the spectral ratios from frequency to depth, resulting in an image of the subsurface similar to that of a seismic reflection profile. The results demonstrate the use of teleseismic signals for characterizing and imaging shallow sedimentary strata on receiver arrays.

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