ABSTRACT
The Mid-Niigata Prefecture Earthquake was an inland earthquake of magnitude 6.8 that occurred in the Niigata prefecture, Japan on October 23, 2004. Hillslope disasters characteristic to the Mid-Niigata Prefecture Earthquake were reactivated landslide. The numerous reactivated landslides during the Mid-Niigata Prefecture Earthquake likely occurred because strong seismic motions were applied not only once but several times and the soil was almost saturated by the heavy rainfall of Typhoon 23 on October 20 and 21. Landslide displacement and hydrological and weather parameters have been automatically monitored at 10-minute intervals since 2001. Thus, the instruments precisely monitored the landslide movement and fluctuation of pore water pressure during the Mid-Niigata Prefecture Earthquake. The relationship between landslide movement and pore water pressure was investigated by K. Fujisawa & R. Tsunaki, who reported that changes in underground water level were recorded at the head and toe of a reactivated landslide mass during an earthquake.
