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Ground motion in the presence of complex topography

Bulletin of the Seismological Society of America

By:
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DOI: 10.1785/0120130088

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Abstract

To study the influence of topography on ground motion, eight seismic recorders were deployed for a period of one year over Poverty Ridge on the east side of the San Francisco Bay Area, California. This location is desirable because of its proximity to local earthquake sources and the significant topographic relief of the array (439 m). Topographic amplification is evaluated as a function of frequency using a variety of methods, including reference‐site‐based spectral ratios and single‐station horizontal‐to‐vertical spectral ratios using both shear waves from earthquakes and ambient noise. Field observations are compared with the predicted ground motion from an accurate digital model of the topography and a 3D local velocity model. Amplification factors from the theoretical calculations are consistent with observations. The fundamental resonance of the ridge is prominently observed in the spectra of data and synthetics; however, higher‐frequency peaks are also seen primarily for sources in line with the major axis of the ridge, perhaps indicating higher resonant modes. Excitations of lateral ribs off of the main ridge are also seen at frequencies consistent with their dimensions. The favored directions of resonance are shown to be transverse to the major axes of the topographic features.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Ground motion in the presence of complex topography
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/0120130088
Volume
104
Issue:
1
Year Published:
2014
Language:
English
Publisher:
Seismological Society of America
Contributing office(s):
Denver Federal Center
Description:
16 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of the Seismological Society of America
Number of Pages:
16
Country:
United States
State:
California
City:
Santa Clara Valley
Other Geospatial:
Diablo Mountains;Poverty Ridge