HR: 10:55h
AN: S42A-03 INVITED     [Abstracts]
TI: Three-dimensional Liquefaction Susceptibility Using Geostatistics
AU: * Baise, L G
EM: laurie.baise@tufts.edu
AF: Tufts University, Dept. of Civil and Environmental Engineering 113 Anderson Hall, Medford, MA 02155 United States
AU: Brankman, C M
EM: brankman@fas.harvard.edu
AF: Harvard University, Dept. of Earth & Planetary Sciences 20 Oxford St., Cambridge, MA 02138 United States
AB: We have developed a new three-dimensional (3D) geostatistical analysis method to evaluate liquefaction susceptibility. Using 3D allows us to identify continuous volumes of liquefiable soil at depth that can lead to surface manifestations of liquefaction and is an improvement to more traditional one-dimensional and two-dimensional methods. The geostatistical analysis provides an estimate of spatial variability and estimate uncertainty as well as a method for interpolation beyond known values. The resulting interpolation inherently includes a measure of prediction uncertainty. The 3D geostatistical analysis of liquefaction susceptibility accounts for spatial variability at the site and therefore provides a method for informed extrapolation from known values. In order to map the liquefaction hazard using this 3D method, we need to evaluate how much soil at a site must be classified as liquefiable in order to cause liquefaction-induced ground failure. Knowing the volume of theoretically liquefiable soil at a site is not directly useful unless we understand how much soil is needed to cause ground failure. To determine this threshold value, we studied data from several sites in California that were exposed to the October 17, 1989, Loma Prieta Earthquake or the January 17, 1994, Northridge, California Earthquake. The investigated sites included detailed subsurface investigations as well as post-earthquake surveys. The goal of this study was to determine how much theoretically liquefiable soil is necessary to induce a ground failure. To achieve this goal, indicator values were assigned to soil samples. Using the indicator value data and geostatistical interpolation, we created solid three dimensional models for a given probability of liquefaction at each site. We calculated the volume of soil at each site associated with a range of probability levels. We determined the relationship between the percentage of theoretically liquefiable soil at the site and the probability of liquefaction for each site.
DE: 7223 Seismic hazard assessment and prediction
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2004 AGU Fall Meeting