長者ヶ原断層・芳井断層の断層変位地形と最新活動時期の検討 [in Japanese] Geomorphic evidence for Chojagahara and Yoshii faults and the timing of their latest seismic event [in Japanese]
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<BR>Chojagahara fault in southeast of Hiroshima prefecture and Yoshii fault in southwest of Okayama prefecture are both NE-SW extending right lateral strike slip faults being separated with 10km gap in Kannabe plain. Distinctive geomorphic evidence along the Chojagahara fault suggests that the fault has moved during the recent geological period. We identified young sharp lineaments forming left echelon stepping in the plain, cutting and disturbing the rectangular field pattern originated from“ Jon-lot system” on alluvial lowland, indicating their activity during the historical period.<BR>A trench was dug across one of the lineaments to confirm the latest event of the fault, and a fault outcrop that cuts up to the base of cultivated soil appeared on the trench walls. The fault strikes N530E, and dips 700N and the northern block has been pushed up. The radiocarbon ages agrees that the latest event took place after the“ Jorilot system”.<BR>The pattern of dip-slip distribution along these strike-slip faults, i. e. the northern side up in the east and southern side up in the west, also suggests that they continue to each other to form a long active fault system.
- Active Fault Research
Active Fault Research 2004(24), 175-184, 2004
Japanese Society for Active Fault Studies