HR: 0800h
AN: S51A-0225    [Abstracts]
TI: LiqueMap: A Real-Time Postearthquake map of Liquefaction Probability
AU: * Noce, T E
EM: tnoce@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road MS 977, Menlo Park, CA 94025, United States
AU: Holzer, T L
EM: tholzer@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road MS 977, Menlo Park, CA 94025, United States
AU: Bennett, M J
EM: mjbennett@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road MS 977, Menlo Park, CA 94025, United States
AB: LiqueMap is a proposed map for real-time distribution over the internet after a large earthquake. It predicts the spatial distribution of the probability of liquefaction in the area subjected to strong ground motion. It relies on peak ground accelerations (PGA) produced by ShakeMap and the methodology for probabilistic liquefaction hazard mapping that was developed by Holzer and others (USGS OFR 02-296, 2006). This methodology relies on field- based plots of cumulative frequency distributions of the liquefaction potential index (LPI) of surficial geologic units. LPI is a scalar parameter that integrates the liquefaction potential of the whole soil column as a function of PGA and earthquake magnitude. LiqueMap is produced with ArcGIS\copyright Model Builder. Three requirements must be met to produce a LiqueMap. First, digitized maps of surficial geology must be accessible with sufficient resolution to distinguish between geologic units with different liquefaction susceptibility. Second, adequate subsurface information or knowledge must be on hand for each surficial geologic unit in the ShakeMap area to produce plots of cumulative frequency of LPI for the range of earthquake magnitudes and PGA that are expected. These plots of cumulative frequency are used to establish liquefaction probability distribution functions for each surficial geologic unit. If LPI data for local geologic units are not available, generic probability distribution functions based on the type of geologic unit can be substituted. The third requirement is the spatial distribution of PGA. PGA values from ShakeMap are gridded and are used as input to the liquefaction probability distribution function at each node to the compute the spatial pattern of liquefaction probability. Because position of the water table is a critical parameter for evaluating liquefaction potential, liquefaction probability distribution functions are computed for either idealized or actual conditions depending on the hydrologic information that is available. LiqueMap should be useful to utility and transportation agencies for identifying areas of potential damage to lifelines from liquefaction-induced permanent ground deformation. When overlain on maps of vulnerable pipelines and other lifelines, LiqueMap can help these entities set priorities for post-earthquake inspections.
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: 2007 Fall Meeting