- © 2006 by the Seismological Society of America
To evaluate the occurrence of large earthquakes and associated damaging ground motions, probabilistic ground-motion maps have been published for the United States, Japan, and other countries (Frankel et al., 1996; Headquarters for Earthquake Research Promotion, 2005; Global Seismic Hazard Assessment Program, 1999). These maps are constructed by combining large amounts of data and model estimates of seismicity, distance attenuation, and local site response. A complementary map of maximum ground motion (intensity) also can be constructed empirically from a good record of historical intensity, for example, the compiled reports in Japan. Some past studies have used seismic intensities from historical earthquakes to quantify the expected level of strong shaking for Japan. Kawasumi (1951) used relations among intensity, magnitude, and acceleration to estimate expected maximum acceleration levels across Japan for periods of 75, 100, and 200 years. Kanai and Suzuki (1968), following a similar method, estimated peak velocity distributions. In another study of probabilistic hazards for Japan related to seismic intensities, Wesnousky et al. (1984) investigated the relationship among repeat times of earthquakes, seismic moment, and associated seismic intensity distribution using geologic-fault data and showed the probabilistic occurrence of earthquakes with intensity equal to or larger than JMA 5.
However, the published probabilistic maps all depend largely on the models and inferences about the magnitudes and locations of historical earthquakes, which are diffi cult to verify fully. In this study we take the simple approach of directly mapping the maximum historical intensity distribution across Japan. We use the Japan Meteorological Agency (JMA) intensity, as observed by JMA and interpreted by Usami (2003). Historical records of earthquake damage in Japan extend back more than 1,000 years and provide a valuable resource for studying historical seismicity. We make no assumptions about earthquake location, magnitude-intensity relations, or earthquake occurrence models. This approach …