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

Abstract

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.

Site characterisation in Barreiro urban area (Portugal) using H/V and ReMi techniques

“…According to some authors, V S30 values correlate well with local amplifications (e.g., Mucciarelli and Gallipoli 2006;Odum et al 2013). The V S30 and the H/V amplitudes correlation in Barreiro (V S30 = 39.0 H/V + 253.9) is similar to the results obtained by Mucciarelli and Gallipoli (2006) for average amplitudes: Soil Type B (EC8 classification) in Barreiro presented, except for one situation, amplitudes larger than 3 (Figure 12b) and Mucciarelli and Gallipoli (2006) obtained average amplitudes between 3.41 and 3.65; Soil Type C in Barreiro presented amplitudes below 3, and Mucciarelli and Gallipoli (2006) obtained amplitudes between 2.67 and 2.92.…”

“…These variations may be responsible for Type B inversions observed in the Holocene and Plio-Pleistocene units. Santisteban et al (2012) and Odum et al (2013) obtained similar inversions associated to alternations of sand, clay, and landfills in Spain and Puerto Rico, respectively.…”

Investigation of Attenuation of theLg‐Wave Amplitude in the Caribbean Region

“…The PRSMP operates both structural array and free-field stations whereas the PRSN maintains vault stations (Clinton et al, 2006). Odum et al (2013) selected 27 sites as the representative of the near-surface material to study the site parameters in Puerto Rico. They compared their results with the observed data for the 16 May 2010 M w 5.8 Puerto Rico earthquake recorded in eight specific PRSMP stations.…”

“…They compared their results with the observed data for the 16 May 2010 M w 5.8 Puerto Rico earthquake recorded in eight specific PRSMP stations. The stations are located at distances from 0.5 to approximately 12 km from the surveyed sites (Odum et al, 2013). A general geologic description of PRSMP stations and their National Earthquake Hazards Reduction Program site classifications can be found in Odum et al (2013).…”

“…A general geologic description of PRSMP stations and their National Earthquake Hazards Reduction Program site classifications can be found in Odum et al (2013). Also, Odum et al (2013) provide V S30 obtained by reflection/refraction (body wave) and refraction microtremor (surface wave) surveys at sites near PRSMP stations.…”