Abstract: Energy Characteristics of Ground Motion Recorded at Sites of Historic Soil Liquefaction Along the East-Side of San Francisco Bay, California, During the Loma Prieta Earthquake, 17 October 1989

Robert E. Kayen, John A. Egan

The characteristics of ground motion, recorded at strong motion instrument sites on the east side of San Francisco Bay, during the Loma Prieta Earthquake of 17 October 1989 are compared with the observed liquefaction field performance of native sediment and artificial fill sites. These sites extend from Treasure Island and the Port of Oakland Facilities near the San Francisco-Oakland Bay Bridge, to Coyote Creek at the southern end of the Bay. During the Loma Prieta Earthquake, soil liquefaction was observed in some portion of the soil column at all of these sites, with the exception of Coyote Creek which showed no evidence of liquefaction. The Coyote Creek site is enigmatic as it is closer to the fault rupture, has only a modest resistance to soil liquefaction, and suffer d extensive damage during the San Francisco Earthquake of 1906. Furthermore, using conventional stress-based analysis techniques it was expected that the Coyote Creek site should have liquefied during the Loma Prieta event. We use a ground motion energy-based approach to assess the severity of ground shaking within the investigated soil deposits. Our investigation found that a correlation between the energy content of the recorded ground motion (measured as Arias Intensity), and the density state of the soil (e.g. penetration resistance), successfully segregates the sites that liquefied during the Loma Prieta earthquake, from those that did not.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California