[S-CG52] Dynamics in mobile belts

[SCG52-18] Active faults associated with the half-graben structure and its inversion tectonics inferred from the basalment structure around Mikawa Bay, Japan.

*Ayumu Miyakawa¹, Tomoya Abe¹, Tatsuyay Sumita¹, Makoto Otsubo² (1.Institute of Geology and Geoinformation, Geological Survey of Japan, AIST, 2.Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST)

Keywords:Gravity survey, Inversion tectonics, Mikawa Bay Region, Chita Peninsula, Utsumi Fault, Takahama Fault

The Mikawa Bay Region, central Japan, is characterized by many active faults recording Quaternary activities. It is, however, difficult to understand the overall tectonic character of the region due to a thick sedimentary cover. We report the finding of basin inversion by estimating the depth and structure of the basement surface by analyzing gravity data. Our gravity survey revealed a half-graben bounded on the souther edge of Chita Peninsula by the north-dipping Utsumi Fault. The motion of the Utsumi Fault, which inverted from normal faulting during the Miocene to recent reverse faulting, indicated the inversion of the half-graben. The Takahama Fault in the southwestern part of the Nishi–Mikawa Plain is considered to have formed as a result of the backthrust of the Utsumi Fault under inversion tectonics.