[S-SS11] Active faults and paleoseismology

[SSS11-03] Deep seismic reflection profiling across the the Morimoto-Togashi fault zone, central Japan

*Tatsuya Ishiyama¹, Hiroshi Sato^1,5, Tomotaka Iwata², Yoshihiro Hiramatsu³, Naoko Kato¹, Hideo Saito⁴, Hirokazu Ishige⁴, Susumu Abe⁴ (1.Earthquake Research Institute, University of Tokyo, 2.Disaster Prevention Research Institute, Kyoto University, 3.School of Geosciences and Civil Engineering, College of Science and Engineering, Kanazawa University, 4.JGI, Inc., 5.Center for Integrated Research and Education of Natural Hazards, Shizuoka University)

Keywords:Active fault, Morimoto-Togashi Fault Zone, Deep seismic reflection profiling, Fault structure

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.