Mapping Earthquake Shaking and Earthquake Damage

Monday, June 10, 2002 - 3:00pm - 3:50pm
Keller 3-180
James Dewey (U.S. Geological Survey)
Earthquake hazard mitigation requires preparation of maps that depict earthquake shaking or damage resulting from earthquake shaking. Usually the variable that is mapped is a representation of the average level of shaking or damage, with no explicit accompanying estimate of dispersion. The maps may extrapolate from a relatively few points of observation to large areas from which there are no observations. My talk will focus on the mapping of macroseismic intensity, which is a single number that represents the level of shaking within an entire community due to an earthquake. A macroseismic intensity is based on the observation of effects of the earthquake on people, familiar objects, buildings, and the natural environment in the community. Problems arising from the stochastic nature of macroseismic intensities, and opportunities for new ways of summarizing macroseismic intensities that would be more useful to specific users of intensity maps, are illustrative of problems and opportunities encountered in the preparation of maps of other earthquake-shaking variables, such as ground acceleration recorded by seismographs. I will review the complex nature of earthquake damage, point out problems the complexity poses for preparers and users of macroseismic intensity maps, and consider new opportunities offered by the collection of macroseismic observations over the Internet, which may yield tens or hundreds of observations per community per earthquake.