Abstract
At the offshore of Mid-Niigata Prefecture, a big earthquake of M6.8 occurred at 10: 13 on July 16th in 2007. The hypocenter of the main shock was 17km deep, and the maximum JMA seismic intensity 6+ was recorded over a wide coastal area. It gave serious damage to Kashiwazaki City, Kariwa Village, Izumozaki Town, Nagaoka City in Niigata Prefecture, and lizuna Town in Nagano Prefecture.
Japan Society of Engineering Geology (JSEG) started the urgent investigation from the next morning on July 17th headed by Dr. Nozaki, T. (vice president of Hokuriku Branch), and the preliminary report was uploaded to the web site of JSEG in a few days. Following this pre-investigation, JSEG organized investigative mission leaded by Prof. Yamagishi, H. (president of Hokuriku Branch) and supported by Debris Disaster Committee (Chairman: Prof. Chigira, M.) of the JSEG headquarters, and 13 volunteer members from Tokyo, Sapporo and Niigata were dispatched to the stricken area on August 3rd, when the maximum temperature had reached to 36°C. The temporary report by this mission was also uploaded to the web site of JESG.
On the basis of these field survey, particularly on the liquefaction and landslides both of which are typical seismic disasters, their situation and mechanisms are discussed in this paper.
