At 5:56 PM JST on October 23, 2004, J_MA 6.8 earthquakes struck Mid Niigata Prefecture, Central Japan. The hypocenter of the main shock is located at 37.3 N; 138.8E with depth of 13 km. The intensity is registered 7 on the 7-grade Japanese intensity scale. Many aftershocks including some M6 class events have been following. The victims of this earthquake are 40. At peak time, over 100,000 refugee have stayed in schools, tents and cars. Geological Survey of Japan, AIST sent the teams of researchers for surveying the earthquake related fault system and disasters, providing geological maps and data of this area.