Researches of fault activity and faulting process for the Major Active Faults

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The precise seismic profilings have carried out at the Seto Inland Sea, Ariake-kai, Yatsushiro-kai and Mikawa Bay etc., where detailed characteristics of submarine active faults have been clarified. Sediments were sampled at the some parts of these seas using sea bottom drilling and piston corerer, and their fault activity and character were analysed by the sedimentological and dating methods.The distribution of active faults beneath the deep seas such as Nankai Trough and Japan Trench has been mapped and compiled in the book entitled with -Active fault in Japan : revised edition" published from the University of Tokyo Press in 1991. This comprehensive book was edited by almost all researchers of this project, and aims to display many data of active faults in the form of sheet maps on the scale of 1 : 200, 000.The excavation study for the Median Tectonic Line active fault system has been aimed principally at revealing ages of faulting event and recurrence intervals at three localities … More in the eastern part of Shikoku. Especially, the latest event were extensively investigated and a probable candidate like ly seems to be 1596 Keicho earthquake (M=7.5).Many drilling surveys were carried out along the Umehara fault belonging to the Nobi fault system and the Kitatake fault. The activity and behaviors of faulting for these active faults were clarified by investigating the lithology and dating for the core samples obtained. The displacements during the Nobi earthquake has reexamined along the Neodani fault, and its activity during the late Quaternary has been clarified with relation to the terrace choronology.Detailed traces and classification of active fault along the major active faults were drawn on the large scale maps (scale /1 : 25, 000-1 : 10, 000) by photo-interpretation and field survey at the southern foot area of the Rokko Mountains and the western marginal area of the Kitakami River.The ^<14>C dating method by accelerator mass spectrometry has been improved for evaluating the fault activity and past events of faulting. Less