high-resolution seismic reflection profiling across the … masami togo+*, takaya iwasaki++,...
TRANSCRIPT
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High-resolution seismic reflection profiling across the
Senya fault at Hanaoka, northern Honshu, Japan: Data
acquisition and processing
Hiroshi Sato+�*, Yasutaka Ikeda,�, Toshifumi Imaizumi-�, Hitoshi Mikada.�, Shigeru Toda/�,
Hiroyuki Tsutsumi0�, Shin Koshiya1�, Ken Noda1�, Tanio Ito2�, Takahiro Miyauchi2�, Hiroshi
Yagi3�, Masami Togo+*�, Takaya Iwasaki++�, Mamoru Saka+�, Naohsi Hirata+�, Nobunao Matsu-
ta++�, Tomonori Kawamura+,�, Kouson Ishimaru+-�, Takeshi Ikawa+.� and Senya 30 Seismic
profiling group
+�Earthquake Research Institute, The University of Tokyo, ,�Graduate School of Science, The Uni-
versity of Tokyo, -�Faculty of Education and Human Sciences, Yamanashi University (Now at Grad-
uate School of Science, Tohoku University), .�Earthquake Research Institute, The University of
Tokyo (Now at Graduate School of Engineering, Kyoto University), /�Aichi University of Education,0�Graduate School of Science, Kyoto University, 1�Department of civil & Environmental Engineer-
ing, Iwate University, 2�Department of Earth Sciences, Chiba University, 3�Faculty of Education,
Yamagata University, +*�Hosei University, ++�Graduate School of Science, The University of Tokyo
(Now at National Taiwan University), +,�Graduate School of Science and Technology, Chiba Univer-
sity (Now at JGI Inc.), +-�Power Reactor and Nuclear Fuel Development Corporation (Now at Japan
Atomic Energy Agency), +.�JGI, Inc.
Abstract
The Senya fault, northern Honshu, Japan, which generated the Rikuu earthquake (Mj 1.,) +230,
is a typical intra-arc active thrust. Subsurface geometry provides essential information for better
understanding strong ground motions and crustal deformation processes. A high-resolution seismic
reflection survey was conducted along the 0-km long seismic line across the toe of the thrust to
reveal the subsurface geometry. The seismic source was a Mini-vibrator truck and the receiver
interval was +* m. The seismic data were processed by the standard common mid-point method.
The Senya fault is clearly identified as a boundary between horizontal reflectors of the basin fill in
the Yokote basin and moderately dipping reflectors beneath the Senya hills. The thrust occurred in
late Miocene mudstone, and shows a flat and ramp geometry. The emergent thrust dips -* degrees
down to /** m, and changes its dip to subhorizontal following the distribution of the mudstone.
* email : [email protected] ]�++-�**-, %La�L��� +�+�+�
D E O P Q � �Bull. Earthq. Res. Inst.
Univ. TokyoVol. 2+ ],**0� pp. 31�+*0
� 97 �
Key words : active fault, seismic reflection profiling, Senya fault, Rikuu earthquake, Northern Japan
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Fig. +. Generalized geological structure of northern Honshu (modified after Yamazaki et al., +32-).
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Fig. ,. Geological map around the Senya hills showing the location of the Senya 30 seismic line. The geological map
is after Usuta et al. (+310) modified by authors based on new geological survey.
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Fig. -. Detailed location of the Senya 30 seismic line. The base map is at a scale of + : ,/,*** issued from
the Geographical Survey Institute.
Table +. Data acquisition parameters for the Senya 30
seismic line.
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30 seismic line.
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Fig. /. Optimum stacking velocities determined by velocity analysis and distribution of number of folds along
a CMP stacking line.
Table ,. Processing parameters for CMP Senya 30
seismic line.
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rv�m��S ^jk��� +/� +**�+*/.
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Koshiya, S., Togo, M., Toda, S., Kawamura, T., Matsuta,
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kura, M., Suzuki, H., Soeda, Y., Noda, K., Yagi, H., Kuma-
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