御母衣断層系の完新世断層活動と1586年天正地震

トレンチ掘削調査による検討

抄録

The Miboro Fault System extends about 65km from NNW to SSE along the upper course of the Shokawa River in the western Hida Mountains, central Japan. The fault system is one of the longest left-lateral strike-slip faults in cenral Japan, and is composed of three fault segments showing a left-handed en echelon arrangement; the Kazura, Shirakawa and Miogo Faults from the north. The Tensho earthquake of 1586 A. D. is inferred to have been generated by the faulting of the Miboro Fault System because severe damage including large-scale slope failures was caused by the earthquake along the Shirakawa and Miogo Faults.
We excavated two trenches across the Shirakawa Fault at Kidani in Shirakawa Village, and three trenches across the Miogo Fault at Terakodo in Shokawa Village, in order to verify the relationship between the latest faulting of the Miboro Fault System and the 1586 Tensho earthquake.
Our excavation has revealed that the latest faulting events on the Shirakawa and Miogo Faults occurred after 2, 500y. B. P., and after 840y. B. P., respectively. The result suggests that the 1586 Tensho earthquake was generated by the latest faulting of the Shirakawa and Miogo Faults, although the participation of the Kazura Fault in this event remains uncertain to be verified.