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Surface seismic measurements of near-surface P-and S-wave seismic velocities at earthquake recording stations, Seattle, Washington

Earthquake Spectra

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Abstract

We measured P-and S-wave seismic velocities to about 40-m depth using seismic-refraction/reflection data on the ground surface at 13 sites in the Seattle, Washington, urban area, where portable digital seismographs recently recorded earthquakes. Sites with the lowest measured Vs correlate with highest ground motion amplification. These sites, such as at Harbor Island and in the Duwamish River industrial area (DRIA) south of the Kingdome, have an average Vs in the upper 30 m (V??s30) of 150 to 170 m/s. These values of V??s30 place these sites in soil profile type E (V??s30 < 180 m/s). A "rock" site, located at Seward Park on Tertiary sedimentary deposits, has a V??S30 of 433 m/s, which is soil type C (V??s30: 360 to 760 m/s). The Seward Park site V??s30 is about equal to, or up to 200 m/s slower than sites that were located on till or glacial outwash. High-amplitude P-and S-wave seismic reflections at several locations appear to correspond to strong resonances observed in earthquake spectra. An S-wave reflector at the Kingdome at about 17 to 22 m depth probably causes strong 2-Hz resonance that is observed in the earthquake data near the Kingdome.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Surface seismic measurements of near-surface P-and S-wave seismic velocities at earthquake recording stations, Seattle, Washington
Series title:
Earthquake Spectra
Volume
15
Issue:
3
Year Published:
1999
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Earthquake Spectra
First page:
565
Last page:
584
Number of Pages:
20