Morphological characteristics of the surface ruptures on the ends of the Nojima Earthquake Fault

概要

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The surface ruptures appeared on the ends of main trace of the Nojima Earthquake Fault which occurred on the northwestern side of Awaji Island accompanying the 1995 Southern Hyogo Prefecture Earthquake in Japan. The northern end part of the earthquake fault is composed of two surface rupture zones of striking N50°-80°W and branching obliquely from the main trace of the earthquake fault. The southern end part of the earthquake fault consists of discontinuous surface ruptures, progressive flexures and some slope failures, which are concentrated in a narrow zone at most a few tens of meters wide and several kilometers long. The displacements along these surface ruptures are generally less than 20cm both in horizontal and vertical, and don't depend on geologic and geomorphologic boundary. The geodetic data show that there were some coseismic displacements both in horizontal and vertical along the surface ruptures in the southern part of the earthquake fault. The aftershock distributions in January 17,1995 show a tendency to be concentrated on the area around the southern end (Ichinomiya Town) of the earthquake fault. The harmonious characteristics of the deformational topographies, geodetic and aftershock distributions suggest that the surface ruptures were formed on the ends of main trace of the Nojima Earthquake Fault by tectonic movement accompanying the earthquake.