Journal of Natural Disaster Science

SOURCE COMPLEXITY OF THE JANUARY 17, 1995 HYOGOKEN-NAMBU EARTHQUAKE DETERMINED BY NEAR-FIELD STRONG MOTION MODELING: PRELIMINARY RESULTS

Arben PITARKA*, Kojiro IRIKURA* and Takao KAGAWA**
*Disaster Prevention Research Institute, Kyoto University
**Geo-Research Institute, Osaka Soil Test Laboratory, Osaka

(Received 28 February, 1995 and in revised form 14 April, 1995)

Abstract

Six near-field strong motion velocity records from the January 17, 1995 Hyogoken-nambu earthquake were modeled to determine the locations and focal mechanisms of the main subevents. The results of forward modeling, for which point source responses are calculated by a reflectivity method, suggest that a four-source model fits the data. All four subevents were located in almost the same direction from the epicenter with an azimuth of 55 degrees NE indicating that they were all triggered by the Rokko fault or its secondary associated subfaults. The depths of these subevents were 17, 8, 6 and 6 km and the respective epicentral distances 0, 10, 18 and 25 km. Their focal mechanisms were the same strike slip type. The strike, dip and slip angles of the first subevent, which had the biggest seismic moment, were 230, 75 and 170 degrees.

Key words

1995 Hyogoken-nambu earthquake, strong motion modeling, source process, focal mechanism