Mapping Liquefiable Layer Thickness for Seismic Hazard Assessment

Abstract

Investigations of liquefaction sites, combining subsurface mapping and evaluation of liquefaction damage, are summarized for four areas in San Francisco affected by 1906 and 1989 earthquakes, where more than 950 borehole and sounding records were collected and analyzed. The maps developed from this database provide a comprehensive picture of subsurface conditions with substantial practical value. Postliquefaction settlement, horizontal displacement caused by lateral spread, and earthquake damage to buried pipelines are shown to be related closely with the thickness of underlying liquefiable soil. The influence of surface and liquefiable layer thicknesses on liquefaction damage is evaluated. Mapping liquefiable layer thickness is shown to be an excellent means of locating areas of potentially severe liquefaction, which is adapted easily to geographic information systems (GIS) for planning and design purposes.