Near-surface S-wave and P-wave seismic velocities of primary geological formations on the Piedmont and Atlantic Coastal Plain of South Carolina, USA

Odum, Jack K.; Williams, Robert A.; Stephenson, William J.; Worley, David M.

doi:10.3133/ofr0343

Cited by 6 publications

(1 citation statement)

References 16 publications

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“…The near-surface low-velocity structure at the observation sites is likely 3D. I make this assumption based on the following observations: first, the EC site is located on an erosional surface of the Piedmont plateau, which is known to contain highly deformed metamorphic rocks with strong vertical and horizontal velocity contrasts (Odum et al, 2003). The thickness of the erosional layer is highly variable, because it consists of saprolitic soils that grade to unweathered rock.…”

Section: Discussionmentioning

confidence: 99%

The Effects of the Near‐Surface Geology onP–SStrain Energy Partitioning of Diffusive Seismic Coda: Preliminary Observations and Results

Poppeliers

2015

Bulletin of the Seismological Society of America

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The diffusive approximation predicts that the ratio of S-to-P energy in earthquake coda depends only on the ratio of S and P wavespeeds. However, for seismic applications, the near-surface geologic conditions can introduce complications to the original models of coda diffusion. Specifically, the free-surface and near-surface site effects can conspire to significantly affect the ratio of body-wave energy when observed at the Earth's surface. To address these effects, previous workers developed physics-based models of coda diffusion to account for near-surface effects such as body-to-surface-wave mode conversions and Earth stratification. These models predict that the value of the S-to-P energy in coda will be strongly affected by near-surface effects; however, there have been very few controlled experiments to verify this. In this article, we describe the results of an experiment that was designed to observe the effects of the near surface on the S-to-P strain energy ratio of the coda. Two arrays were deployed simultaneously at two different sites, each of which contained significantly different near-surface geology. We observe that the energy ratio of the coda is significantly affected by the near-surface geology and is highly frequency dependent.

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Section: Discussionmentioning

confidence: 99%

The Effects of the Near‐Surface Geology onP–SStrain Energy Partitioning of Diffusive Seismic Coda: Preliminary Observations and Results

Poppeliers

2015

Bulletin of the Seismological Society of America

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VS30 and Spectral Response from Collocated Shallow, Active-, and Passive-Source VS Data at 27 Sites in Puerto Rico

Odum

Stephenson

Williams

et al. 2013

Bulletin of the Seismological Society of America

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Shear-wave velocity (V S ) and time-averaged shear-wave velocity to 30 m depth (V S30 ) are the key parameters used in seismic site response modeling and earthquake engineering design. Where V S data are limited, available data are often used to develop and refine map-based proxy models of V S30 for predicting ground-motion intensities. In this paper, we present shallow V S data from 27 sites in Puerto Rico. These data were acquired using a multimethod acquisition approach consisting of noninvasive, collocated, active-source body-wave (refraction/reflection), activesource surface wave at nine sites, and passive-source surface-wave refraction microtremor (ReMi) techniques. V S -versus-depth models are constructed and used to calculate spectral response plots for each site. Factors affecting method reliability are analyzed with respect to site-specific differences in bedrock V S and spectral response. At many but not all sites, body-and surface-wave methods generally determine similar depths to bedrock, and it is the difference in bedrock V S that influences site amplification. The predicted resonant frequencies for the majority of the sites are observed to be within a relatively narrow bandwidth of 1-3.5 Hz. For a first-order comparison of peak frequency position, predictive spectral response plots from eight sites are plotted along with seismograph instrument spectra derived from the time series of the 16 May 2010 Puerto Rico earthquake. We show how a multimethod acquisition approach using collocated arrays compliments and corroborates V S results, thus adding confidence that reliable site characterization information has been obtained.

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A New Seismic Site Coefficient Model Based on Conditions in the South Carolina Coastal Plain

Aboye¹,

Andrus²,

Ravichandran³

et al. 2014

Bulletin of the Seismological Society of America

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Near-surface S-wave and P-wave seismic velocities of primary geological formations on the Piedmont and Atlantic Coastal Plain of South Carolina, USA

Cited by 6 publications

References 16 publications

The Effects of the Near‐Surface Geology onP–SStrain Energy Partitioning of Diffusive Seismic Coda: Preliminary Observations and Results

The Effects of the Near‐Surface Geology onP–SStrain Energy Partitioning of Diffusive Seismic Coda: Preliminary Observations and Results

VS30 and Spectral Response from Collocated Shallow, Active-, and Passive-Source VS Data at 27 Sites in Puerto Rico

A New Seismic Site Coefficient Model Based on Conditions in the South Carolina Coastal Plain

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