[S-SS11] 活断層と古地震

[SSS11-03] 森本・富樫断層帯の深部構造探査

*石山 達也¹、佐藤 比呂志^1,5、岩田 知孝²、平松 良浩³、加藤 直子¹、斉藤 秀雄⁴、石毛 宏和⁴、阿部 進⁴ (1.東京大学地震研究所、2.京都大学防災研究所、3.金沢大学理工研究域地球社会基盤学系、4.株式会社地球科学総合研究所、5.静岡大学防災総合センター)

キーワード：活断層、森本・富樫断層帯、深部構造探査、断層構造

To define subsurface fault geometry, structural characters of fault-related folds and their structural growth during Quaternary, we collected two multi-channel deep seismic reflection profiles across the Morimoto-Togashi Fault Zone (MTFZ), an active reverse fault system located in the southwest extension of the Toyama trough. We used vibroseis trucks (Enviro-vib and UNIVib2) as seismic sources and deployed more than 900 seismic channels for data acquisition. Standard seismic reflection processing reveals the detailed subsurface structure in accordance with P-wave velocity structures obtained by refraction tomography. The depth-converted sections that were correlated with the Neogene strata successfully show a moderately east-dipping reverse fault plane that is overlain by a monocline of Miocene to Pleistocene sedimentary units. Based on structural interpretations of the seismic profile, we will also explore the recent growth of the fault-related folds, structural relationships of the MTFZ to adjacent subparallel reverse faults, and kinematic significance of folded middle-late Pleistocene fluvial terraces above the fault.