Last faulting event of the Senzan fault in the central Awaji Island, southwestern Japan

Abstract

The Senzan fault is an active reverse fault directing N-S to NNE-SSW in the central Awaji Island. During the 1995 Hyogoken-nanbu earthquake, a characteristic surface break appeared along the Nojima fault located at the western side of the Awaji Island, however, no surface break had occurred along the Senzan fault. We excavated an exploratory trench on the Senzan fault to detect the age of the faulting events, and we confirmed a reverse fault making a contact between slope deposits and a granitic rock. The youngest age of the hurried soil deformed by the fault is 1161±67 AD. This means that the last faulting event of the Senzan fault occurred after the 12th Century. This event may correspond to the historical Keicho Fushimi earthquake in 1596 AD.