Japan Geoscience Union Meeting 2014

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Poster

Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS34_29PO1] Active faults and paleoseismology

Tue. Apr 29, 2014 6:15 PM - 7:30 PM Poster (3F)

Convener:*AZUMA Takashi(National Institute of Advanced Industrial Science and Technology), Nobuhiko Sugito(Faculty of Humanity and Environment, Hosei University), Satoshi Tonai Satoshi(Department of Applied Science, Faculty of Scienece, Kochi University), Toshikazu Yoshioka(Active Fault and Earthquake Research Center, National Institute of Advanced Industrial Science and Technology)

6:15 PM - 7:30 PM

[SSS34-P08] Seismic reflection survey across the northern part of the Western Boundary Fault Zone of the Yamagata Basin

*Shinsuke OKADA1, Toshifumi IMAIZUMI1, Kyoko KAGOHARA2, Tomoo ECHIGO3, Hiroshi YAGI4, Yoshikazu MATSUBARA5, Atsushi MIWA5, Hideki KOSAKA6 (1.IRIDeS, Tohoku Univ., 2.Yamaguchi Univ., 3.Geo-Reaearch Institute, 4.Yamagata Univ., 5.OYO Corportion, 6.Kankyo Chishitsu Company Limited)

Keywords:active fault, seismic reflection survey, the Western Boundary Fault Zone of the Yamagata Basin, subsurface structure, Murayama City

The Western Boundary Fault Zone of the Yamagata Basin borders the western margin of the Yamagata basin and is traceable for about 60 km. In the northern part of this fault zone (from Sagae to Ooishida area), subpallarel traces of the active fault distribute in the western side of the basin. At the center of the basin, Kawashima-yama located as a tectonic bulge and its western side the Mogami river incise and meander in the fault zone. Along the eastern side of the Kawashima-yama, syncline is indicated as a frontal deformation by Ikeda (2002) and Imaizumi (2001).To reveal the subsurface structure and tectonic evolution of this fault zone, we carried out two lines (Line A and Line B) of seismic reflection survey from September to October 2013. The Line A has a length of 4.11 km and started from Saigo area to Oomaki via. Kyouei bridge. The Line B has about 3.75 km length and started from Taruishi area to Goten along the Taruishi river. The source used in this survey was an Enviro Vib (IVI Inc.). Sweep length was 16 sec and sweep frequency range beginning at 10 Hz up to 120 Hz. The receiver was GS-20DX (natural frequency, 10 Hz; Geospace Inc.). The source and receiver spacing was 10m, with 192 ch geophones used for each recording. We selected the Geode (Geometrics) for the recording system and its sampling rate is 1 msec.We thank to students of Tohoku University and Kanazawa University for their assistance in our survey. This work was supported by project research of the International Research Institute of Disaster Science (IRIDeS), Tohoku University.[References]Ikeda et al., 2002, Atras of Quaternary Thrust Fault in Japan, Univ. of Tokyo Press, 254pp.Imaizumi et al., 2001, Active Fault Map in Urban Area, Geographical Survey Institute.