Abstract

A map depicting the susceptibility of near-surface cohesionless soil deposits within the downtown area of San Francisco to earthquake induced liquefaction is developed. The map is composed of six zones, each of which comprise materials of similar susceptibility. Susceptibility is defined on the basis of grain size characteristics and equivalent Standard Penetration Test blow count. Typical profiles containing information on soil type, blow count, and water table depth are presented for each map zone to facilitate the evaluation of liquefaction potential within the downtown area.

Five of the six map zones consist of artificially placed fill material. Most geologic maps identify fill materials as such with no further detail. Zone boundaries within the fills had to be determined primarily from historical accounts of fill source and method of placement. These historical accounts were supplemented with over 350 bore logs collected from the public record and the files of three private geotechnical consulting firms. Information on soil characteristics and results of dynamic penetration tests were obtained from the bore logs.

A wave-equation model of dynamic penetration tests was used to convert non-standard dynamic penetration test results to equivalent standard blow counts for characterization of the seismic resistance of the cohesionless soil deposits.

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