Journal of Natural Disaster Science

SURFACE FAULT CHARACTERISTICS OF THE 1995 HYOGOKEN-NAMBU EARTHQUAKE

Takashi NAKATA
Professor, Department of Geography, Hiroshima University Higashi-Hiroshima 739, Japan
and
Kiyoshi YOMOGIDA
Associate Professor, Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739, Japan

(Received 22 February, 1995 and in revised form 11 May, 1995)

Abstract

Distinctive ruptures in the surface faulting that generated the destructive 1995 Hyogoken-nambu earthquake (Ms=7.2) appeared along the Nojima fault, an active fault on the northwestern coast of Awaji Island, Japan. These surface fault ruptures extend continuously southwestward for 10 km from Ezaki lighthouse, near the epicenter to Toshima Town in Hokudan, and display prominent right-lateral off-sets or roads, paddy dikes and so on of l.9 m maximum with vertical displacement of l.2 m maximum, whereas no large surface faulting has been found in Kobe where major damage and casualties occurred.

Most of the surface ruptures follow the pre-existing active fault traces of the Nojima fault. This paper deals mainly with the areal distribution and nature of the ground ruptures and their lateral and vertical displacements as measured precisely in the field.

The source process of the earthquake deduced from the slip distribution along the earthquake fault in Awaji Island explains well the near-field P-waveform records of the broad-band seismometers for the early part of about 4 seconds. The later part with a much larger amplitude could be attributed to the northeast fault ruptures toward Kobe.

Key words

earthquake fault, source process, Hyogoken-nambu earthquake, Nojima fault