Abstract

Maximum seismic intensity maps for Japan are constructed using the recorded intensity data from 1498 to 2007 and are used to test the probabilistic seismic hazard map (PSHM) by the Headquarters for Earthquake Research Promotion, Japan. The historical intensity maps are compared with the hazard maps of probable maximum seismic intensity for a 475-yr return period, assuming a Poisson distribution (10% in 50 yrs). We look at cases that include all events, only subduction zone earthquakes, and all events excluding subduction zone earthquakes. The megathrust earthquakes in the subduction zones produce large bands of high intensities along the Pacific coast side, while onshore crustal earthquakes create a patchy distribution of large intensities over all of Japan. The maximum recorded intensity map for the past 500 yrs and the maximum predicted intensity map for the forumla return period from the PSHM are very similar for the cases including all events and the subduction zone earthquakes, while there is poor correlation for the third category that includes mostly onshore crustal earthquakes. If we consider only the amount of area, not the specific locations, the recorded intensity map and the PSHM (using the maximum case) have a high degree of correlation for Japanese Meteorological Agency (JMA) intensity higher than 4 for all of the cases. Statistically, the present hazard maps for Japan seem to agree with the past intensity distributions and can be regarded as appropriate hazard maps, even though there may be strong dependencies on uncertain model parameters for the PSHMs.

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