Seismology and Strong Ground Motions in the 2004 Niigata Ken Chuetsu,Japan,Earthquake

The Niigata Ken Chuetsu earthquake was a shallow, moderate-sized event producing strong shaking and considerable land failure damage across a significant region of Niigata Prefecture in central Japan. Moment tensor solutions indicate the main shock as being pure reverse faulting on a fault striking 30° east of north, roughly parallel to the mapped active faults and to the structural trends of the region, with nodal planes that dip down to the west at about 50° and down to the east at about 40°. The main shock was followed by an unusual number of large aftershocks. An extensive field investigation identified only minor surface faulting. Hanging wall effects accompanied by unusually high accelerations were observed, with peak horizontal accelerations of 1.75 g recorded at Tohkamachi and 1.33 g recorded at Ojiya.