INFLUENCE OF VELOCITY STRUCTURE AROUND THE PHILIPPINE SEA PLATE ON LONG-PERIOD GROUND MOTION EVALUATION IN OSAKA PLAIN

Abstract

The sedimentary structure of the accretionary wedge adjacent to Nankai Trough influences on generation of the long-period ground motions. This study investigates effects of the accretionary wedge on amplification of the long-period ground motion in Osaka Plain by using the finite difference simulation for the 2004 South-east Off Kii Peninsula foreshock (Mj7.1). Amplification characteristics are discussed for plural locations of hypocenter and existence of sedimentary layers. Ground motion amplification depends on predominant periods of ground motions in rock sites, rather than simply whether accretionary wedge exists or not. This paper also shows effects of the thin soft layer along the Philippine Sea Plate on trapped waves from seismic fault, leading to large amplitude of ground motions.