Liquefaction Opportunity Mapping via Seismic Wave Energy

Abstract

An empirical, energy-based methodology for liquefaction hazard assessment and microzonation mapping is presented. The approach is probabilistic, considers the uncertainty in the liquefaction criterion, and is applicable to most earthquake-induced liquefaction analyses. The examples illustrated are for water-saturated sands at level ground. The energy of ground shaking is estimated from the Fourier amplitude spectra of the incident waves. The susceptible materials are characterized only by their corrected standard penetration test value N¯ and overburden pressure σ0. Illustrative microzonation maps of liquefaction opportunity are shown for the Los Angeles metropolitan area. Two types of maps are presented, one showing the average return period of liquefaction occurrence (for given N¯ and σ0), and another one showing distribution of N¯ with equal probability to liquefy during 50 years exposure (for given σ0). An advantage of the method is that the result is given directly in terms of in situ albeit simple soil characteristics rather than in terms of laboratory tests and peak acceleration. Possible applications of the computed opportunity maps are discussed.