Characterizing and imaging sedimentary strata using depth-converted spectral ratios: An example from the Atlantic Coastal Plain of the Eastern U.S.

Bulletin of the Seismological Society of America
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Abstract

Unconsolidated, near-surface sediments can have a profound influence on the amplitudes and frequencies of ground shaking during earthquakes, and these effects should be accounted for when using amplitude observations for 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 the 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 0.2 to 4 Hz frequency range, which 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 the computation 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.  

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Characterizing and imaging sedimentary strata using depth-converted spectral ratios: An example from the Atlantic Coastal Plain of the Eastern U.S.
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120180046
Volume 108
Issue 5A
Year Published 2019
Language English
Publisher Seismological Society of America
Contributing office(s) Geologic Hazards Science Center, Earthquake Science Center
Description 15 p.
First page 2801
Last page 2815
Country United States
Other Geospatial Atlantic Coastal Plain