HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Wills, C. J. Articles by Clahan, K. B. Search for Related Content GeoRef GeoRef Citation

Developing a Map of Geologically Defined Site-Condition Categories for California

¹ California Geological Survey
801 K Street, MS 12-32
Sacramento, California 95814-3531
cwills{at}conservation.ca.gov
 (C.J.W.)
² California Geological Survey
345 Middlefield Road, MS 520
Menlo Park, California 94025
kclahan{at}conservation.ca.gov
 (K.B.C.)

^* Present address: William Lettis and Associates, 1777 Botelho Drive, Suite 262, Walnut Creek, California 94596.

Consideration of site conditions is a vital step in analyzing and predicting earthquake ground motion. The importance of amplification by soil conditions has long been recognized, but though many seismic-instrument sites have been characterized by their geologic conditions, there has been no consistent, simple classification applied to all sites. As classification of sites by shear-wave velocity has become more common, the need to go back and provide a simple uniform classification for all stations has become apparent. Within the Pacific Earthquake Engineering Research Center’s Next Generation Attenuation equation project, developers of attenuation equations recognized the need to consider site conditions and asked that the California Geological Survey provide site conditions information for all stations that have recorded earthquake ground motion in California. To provide these estimates, we sorted the available shear-wave velocity data by geologic unit, generalized the geologic units, and prepared a map so that we could use the extent of the map units to transfer the velocity characteristics from the sites where they were measured to sites on the same or similar materials. This new map is different from the California Geological Survey "preliminary site-conditions map of California" in that 19 geologically defined categories are used, rather than National Earthquake Hazards Reduction Program categories. Although this map does not yet cover all of California, when completed it may provide a basis for more precise consideration of site conditions in ground-motion calculations.

This article has been cited by other articles:

				A. Pancha, J. G. Anderson, and J. N. Louie Characterization of Near-Surface Geology at Strong-Motion Stations in the Vicinity of Reno, Nevada Bulletin of the Seismological Society of America, December 1, 2007; 97(6): 2096 - 2117. [Abstract] [Full Text] [PDF]

				D. J. Wald and T. I. Allen Topographic Slope as a Proxy for Seismic Site Conditions and Amplification Bulletin of the Seismological Society of America, October 1, 2007; 97(5): 1379 - 1395. [Abstract] [Full Text] [PDF]