Fault Activity along the Itoigawa-Shizuika Tectonic Line Active Fault System

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Many active faults are recognized along the Itoigawa-Shizuoka Tectonic Line (ISTL). Both North and south of them have dip-slip fault type trending mainly north to south, except central part having left-lateral slip type, extending northwest-southeast.Based on interpretation of the large scale aerial-photographs, the auther investigated detail features of fault topography along them, with mapping them on the large scale topographic sheets, in order to clarify the Holocene activity and slip-rates of them.Main results are as follows.1. On the foot of the large flexture scarp of the lchinose upland, young scarplets having 1-5m height are paralleled to mian flexture scarp. These scarplets indicate recente repeatedly faulting in Hococene time.2. Frome Chino to Kobuchizawa, in central part of the ISTL,many evidences of leftlateral stike slip were found on the aluvial fans and the cliff of t flow and tectonic mounds, along the sevral fault traces.3. In the Kamishiro basin, northernmost portion the auther estimated average sliprate (net slip) of the Kamishiro fault at 1.5-2.0mm/year in the late Quaternary to Holocene time on the data of boring using by new method named the Geoslicer after Nakata and Shimazaki (1997).