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| | Abstract | | In recent years local earthquakes with the magnitude of around 6.8 have frequently occurred in Japan. Since the earthquakes with such magnitude do not so often create surface ruptures, it is not so easy to identify the source fault causing the earthquake. Seismic reflection can detect concealed active faults. There are, however, few research works on discussing the detectability of concealed faults with the seismic reflection method based on actual field examples. We, therefore, have studied seismic detection of concealed faults using the reflection survey data and fault parameters obtained in investigations of active faults conducted for earthquake disaster prevention and safety evaluation of nuclear power plants after 1995 Hyogoken-Nanbu earthquake. This study reveals that seismic reflection can detect most of concealed active faults with the length of more than 10km, which generate more than 20m vertical displacement of the Pliocene and older formation due to faulting. |
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