A feasibility study on research techniques for subsurface active faults

概要

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Results of numerical analyses and field studies in the epicenter area of the 2000 Tottoriken-seibu earthquake suggest that several research techniques are effective for identifying subsurface active faults unaccompanied with remarkable surface earthquake faults. Field observation of the lineaments found in the area by detailed air-photo interpretation revealed that most of them are accompanied by faults and/or dikes, and some of them show minor slips at the time of the earthquake.<BR>Crustal deformation caused by the activity of the subsurface seismogenic faults is deduced by numerical analyses based on seismic and geodetic data. The vertical deformation assumed from the height changes of the terraces along the river across the epicenter area suggests that cumulative uplift and subsidence associated with left-lateral strike-slip has been continuing. Offsets rate of the streams and uplift rate of the river terraces surfaces show good agreement with the estimate from the parameter of the earthquake faults model.<BR>Identification of active faults without clear surface evidence before occurrence of earthquakes is a difficult issue, and the techniques adopted in this study will probably provide relevant information effective to locate subsurface active faults.