HR: 16:45h
AN: U22C-04    [PDF]
TI: Earthquake Loss Estimation: What Matters?
AU: * Holzer, T L
EM: tholzer@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, MS977, Menlo Park, CA 94025 United States
AB: A simple earthquake loss model was developed and used to evaluate the relative importance of the different types of Earth science information that are required to estimate losses to single-family residences from earthquake shaking. The evaluation indicates that refining the characterization of the magnitude and frequency of future earthquakes and mapping surficial geology to enable predictions of regional variation of local site amplification are the most important contributions that the Earth sciences can make to improve earthquake loss estimates. The loss model that was used for the evaluation predicts damage to masonry and wood-frame single-family residences. Structural damage was predicted with both the ATC-13 and HAZUS methodologies. The loss model incorporated three aspects of Earth science information: (1) the earthquake source, (2) ground-motion attenuation, and (3) soil type. Properly characterizing the earthquake source has the greatest impact on loss estimation. Whereas large earthquakes are the most costly events, cumulative losses from moderate (M$\sim$6.5) earthquakes can easily exceed the loss from a single large (M$\sim$7.5) event. If the damaged properties are covered by typical earthquake insurance policies and deductibility is taken into account, the cumulative impact of moderate earthquakes may be even more severe from the perspective of the insured; much of the cumulative losses may not be covered by insurance because of the high deductible of the typical policy. Geographic variability of local site amplification, which can be inferred from surficial geologic maps, also may have a significant impact. Loss estimates, based on ground-motion amplification factors in the NEHRP site classification, may vary by almost threefold depending on soil type. Future refinements of ground-motion attenuation curves are not likely to substantially improve loss estimation in the western United States. The range of ground motion predicted by published attenuation curves does not produce significantly different estimates of loss. By contrast, the range of ground motion predicted by different attenuations relations proposed for the eastern United States, particularly for one-second spectral accelerations, produces significantly different estimates of loss.
DE: 7212 Earthquake ground motions and engineering
DE: 7223 Seismic hazard assessment and prediction
SC: U
MN: 2003 Fall Meeting