兵庫県南部地震時に刻まれた野島断層の湾曲した断層条線について

抄録

The January 17, 1995 Hyogoken-Nambu earthquake (Japan Meteorological Agency magnitude of 7.2) produced surface rupture with a maximum right-lateral displacement of 2.1m and a maximum SE-up displacement of 1.4m on the Nojima fault, which runs along the northwest shore of Awaji Island. All the fault striations observed at 10 localities are horizontal, or more or less inclined northeastward. It is noteworthy that the fault striations on the up-thrown plane at 2 localities (Hirabayashi and Ogura) are convex downward, suggesting that the instantaneous slip vector changed from high to low angle through the rupture process. This curious phenomenon is reasonably explained by the temporal splitting of anti-plane mode of shear dislocation from in-plane mode which is realized for the dynamic growth of a mixed-mode shear crack at a trans-Rayleigh rupture speed and hence at a low shear stress [ANDREWS (1994)].