Statistical Comparison of National Probabilistic Seismic Hazard Maps and Frequency of Recorded JMA Seismic Intensities from the K-NET Strong-motion Observation Network in Japan during 1997–2006

National seismic hazard maps for Japan with meshes of 1×1 km2 were published by the Earthquake Research Committee of Japan in March 2005. They are updated annually to reflect time passage of event recurrence (NIED 2005). Since the probabilistic seismic hazard maps focus on estimates for 30 and even 50 years, strict validation of the maps requires probabilistic and statistical approaches with future data. Nevertheless, in this study, as the first step in verifying the validity of the maps, we compared the Japan Meteorological Agency (JMA) instrumental intensities from strong-motion records for the 10-year period ending 31 December 2006 with the corresponding values on the probabilistic hazard maps. The JMA instrumental intensity is a cumulative strong motion indicator, which was adjusted to match the scale previously used to measure seismic intensity, which was based on human response and an index of damage. The JMA intensity scale has 10 grades from 0 to 7 (5 and 6 were divided in lower and higher) and is described at http://www.jma.go.jp/jma/kishou/know/shindo/shindokai.html. Explanations of individual intensities can be found at http://www.jma.go.jp/jma/kishou/know/shindo/explane.html. Although corresponding peak ground acceleration could not precisely be adapted to the intensity scale, relative peak ground acceleration is indicated in http://en.wikipedia.org/wiki/Japan\_Meteorological\_Agency\_seismic\_intensity_scale. JMA has promptly reported this intensity since April 1996 (http://www.jma.go.jp/en/quake/). Verification was done using all of K-NET's strong-motion records for the period 1 January 1997 through 31 December 2006. K-NET is an observation network that uniformly covers all of Japan with stations in polygonal configurations that cover areas about 25 kilometers in size. Network operations began in 1997 with 1,000 stations. New observation sites—many of them in the Kanto metropolitan area—have been added since then. The number of observation sites peaked at 1,035, but by the end of 2006 the number had dropped to 1,028 stations, including …