3-DIMENSIONAL SIMULATION OF THE NEAR-FAULT GROUND MOTION FOR THE 1995HYOGO-KEN-NANBU (KOBE), JAPAN, EARTHQUAKE

The 17 January 1995 Hyogo-ken Nanbu earthquake is a typical example sh owing that the ground motions along basin-edge faults can be very dest ructive. In this study, we simulate the near-fault ground motion from this earthquake based on a kinematic fault model and a simplified 3D v elocity structure of the Kobe area. The kinematic earthquake rupture a nd the wave propagation are modeled using a 3D finite-difference metho d (FDM). Our simulation identifies the basin-edge effect as an importa nt factor that influenced the ground-motion amplification pattern in t he Kobe area. We found that the coupling of the source directivity and basin-edge effects causes impulsive ground motions with extremely hig h amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge. The combination of these effects a cted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin-edge boundary. In some areas, localized site effects might have been as important as the above-mentioned effects, but they cannot explain the continuity of the extended east-west zone of damage.