COMMUNICATION ON EARTHQUAKE HAZARDS AND RISKS IN JAPAN SINCE 1995 KOBE EARTHQUAKE

The Japanese efforts for the evaluation and dissemination on earthquake hazards and risks started after the 1995 Kobe earthquake disasters. The earthquake killed 6434 most of whom nobody had informed of the risks. Geologists had mapped most seismic sources in 1980s, but the information had not been utilized by seismologists and engineers. There was no system to publicize and warn the risks based on geologic data. Following the disasters, the Special Measure Law on Earthquake disaster Prevention was enacted in July 1995 and HERP, the Headquarters for Earthquake Research Promotion was established according to the law. HERP has first took paleoseismological information for earthquake hazard risk evaluation. 2005 Earthquake Ground Shaking Hazard Maps of Japan was a great achievement using time-dependent probabilistic assessment for all plate boundary faults and about 100 most significant on shore faults. However, no clear surface faulting has occurred until 2016, while several minor and mostly blind faults on shore and off shore without HERP evaluation caused some damages. 2004 Niigataken Chuetsu Mw 6.6 earthquake caused very strong ground motion (PGA 1.8 g ) and killed 68. 2007 Niigataken Chuetsu-oki Mw 6.6 earthquake shook the largest nuclear power plant in Japan and shut it down. 2016 Kumamoto Mw 7.0 earthquake ruptured 34 km along the Futagawa fault almost perfectly following the HERP scenario. Though the national and local governments had disseminated risk information on the earthquake, most local people did not take the risks important and imminent and 50 people were killed in many cases under old weak houses. On the other hand, the 2011 Great Tohoku Earthquake (Mw 9.0) and Tsunamis was quite unexpected and killed more than 18000 people. There was no historic and geologic data helped to forecast a Mw 9 class event. 869 C.E. Tsunami data based on tsunami deposits could have saved thousands of lives only if the risks were evaluated and disseminated.