Late Quaternary activity of active faults in the Udo Hill, Shizuoka Prefecture

概要

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Interpretations of aerial photos and large-scale topographic maps, field investigation and analysis of drilling data reveal the presence of previously unknown active faults inside and along the northwestern margin of the Udo Hill, Shizuoka Prefecture. Several parallel-oriented fault scarps trending NNE-SSW to NE-SW are developed along the northwestern margin of the hill, which form a∼1km wide active fault zone extending for 7 km. On the basis of the morphology and geometry of the fault traces, it is inferred that the fault zone consists of southeastdipping reverse faults. There are some active faults developed inside of the Udo Hill. The tectonic landform and drilling data show that the topographic surfaces formed from 70-90 ka to late Holocene are displaced by 1-8 m in vertical. The average vertical slip rate is estimated to be 0.1-0.2 mm/yr for the fault zone in the late Pleistocene.