Timing of latest two faulting events at the southern part of the Hanaore fault - Trenching study at Shugakuin, northeast Kyoto City, central Japan

概要

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The Hanaore fault is a right-lateral strike-slip active fault trending NNE-SSW in Shiga and Kyoto Prefectures. The northern part of this fault might move during the 1662 Kambun earthquake. However, paleoseismic activity in the southern part still has been unclear. We excavated a trench at Shugakuin area in Kyoto City to evaluate the seismic risk of the southern part of this fault. Some high-angle fault planes cutting fan deposits were observed on the trench walls. We divided the sediments on the trench walls into seven stratigraphic units named as unit A to F. As a result of our precise observation, the latest faulting event occurred after the deposition of the unit B2 and before the deposition of unit A. And the penultimate event occurred after the deposition of unit D and before the deposition of unit C. The radiocarbon ages from the trench walls and the results of previous trench studies indicate that the timing of the latest faulting event was about 2,500 to 1,500 years B. P., and the timing of the penultimate event was about 7,800 to 7,000 years B. P. The interval between the last two events is estimated to be about 4,500to 6,300 years.
Japanese Society for Active Fault Studiesの論文