Mapping of Liquefaction Severity Index

Abstract

A technique is developed for compiling liquefaction hazard maps by mapping a parameter termed liquefaction severity index (LSI). LSI, a measure of ground failure displacement, is based on the displacement of lateral spreads on gently‐sloping late Holocene fluvial deposits such as floodplains and deltas. By selecting a specific geologic environment, LSI is normalized with respect to site conditions. LSIs are evaluated for several earthquakes in the western United States, and an equation is developed between LSI, earthquake magnitude, and distance from the seismic energy source. This equation and a model of seismic energy sources is used with a published seismic risk algorithm to compile probabilistic LSI maps for southern California. The maps show contours of LSI with 90% probability of nonexceedance in periods of 10, 50, and 250 years. LSI maps are useful for determining the relative liquefaction hazard and provide an index of possible maximum ground displacement.