L.A. Basin Geotechnical Update

(Provided by Steven T. Maher and Dr. Kenneth W. Campbell)

        The January 1994 Northridge Earthquake, a recent study by the Southern California Earthquake Center (SCER), to be published in the April issue of The Bulletin of the Seismological Society of America, as well as a recent study by Jim Dolan and others published in the January 13, 1995 issue of Science Magazine, provided a new understanding of potentially important geotechnical issues for the Los Angeles Basin. One of the key issues is the increased importance of "Blind Thrust Faults" which underlay much of the L.A. Basin. As an example, the Compton Thrust Fault, the central part of the Torrance-Wilmington. Thrust and Fold Belt which underlies the Newport Inglewood Fault, in concert with an increased slip rate on the Palos Verdes Fault could result in an increase by a factor of 5 the likelihood of a high intensity event for that area.

        Although much of the geotechnical information is still being studied, the understanding of these faults will likely prompt an increase in the seismic hazard used as the basis for seismic evaluations of facilities in the L.A. Basin.

Published in SCSRA Risk Resources, February 1995