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Seismic Pseudo Reﬂection Proﬁling in Shirane Pyrocrastic Cone, Kusatsu-Shirane Volcano
Tomoki TSUTSUI+ῌ, Shin’ya ONIZAWA,ῌ, 3ῌ, Takehiko MORI-ῌ, 3ῌ, Kenji NOGAMI,ῌ,Jun’ichi HIRABAYASHI,ῌ, Yasuo OGAWA,ῌ, Noriaki TAKAGI,ῌ, Atsuo SUZUKI.ῌ,Jun OIKAWA/ῌ, Haruhisa NAKAMICHI0ῌ, +*ῌ, Shin YOSHIKAWA1ῌ
and Takeshi MATSUSHIMA2ῌ
Shallow subsurface structure of Shirane pyrocrastic cone, Kusatsu-Shirane Volcano is discussed with Pseudo
Reﬂection Proﬁling. Pseudo Reﬂection Proﬁles are obtained from a controlled source seismic experiment in
September-October ,**- as a part of the Fourth Joint Observation of Kusatsu-Shirane Volcano. A signiﬁcanthorizon is deﬁned through correlation of the proﬁle with borehole logging data. The horizon is compatible with+*+*ῌ2/*,
 +ῌ+Akita University, +ῌ+, Tegata-gakuen-cho, Akita
city, Akita, *+*ῌ*2/,, Japan.
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Volcanic Fluid Research Center, Tokyo Institute ofTechnology, 0.+ῌ-0, Takijirihara, Kusatsu, Kusatsucho, Agatsuma-gun, Gunma, -11ῌ+1++, Japan.
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34
Sakurajima Volcano Research Center, Disastaer
Prevention Research Institute, Kyoto University,+1,,ῌ+3, Sakurajima-Yokoyama, Kagoshima, 23+ῌ+.+3, Japan.
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Usu Volcano Observatory, Hokkaido University, +.0,Tatsuga, Sobetsu-cho, Usu-gun, Hokkaido, */,ῌ*+*0,Japan.
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Earthquake Research Institute, University of Tokyo,+ῌ+ῌ+, Yayoi, Bunkyo-ku, Tokyo, ++-ῌ**-,, Japan.
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National Institute of Earth Science and Disasterprevention, -ῌ+, Tennodai, tsukuba-city, Ibaraki, -*/ῌ***0, Japan.
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Aso Volcanological Laboratory, Kyoto University,Kawayo, Minami-Aso-son, Aso-gun, 203ῌ+.*., Japan.
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Institute of Seismology and Volcanology, Graduate
school of Kyushu University, ,ῌ/0.-ῌ,3, Shinzan,
Shimabara-city, Nagasaki, 2//ῌ*2.-, Japan.
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 1 Z6[\]^/0NH_`a/0bPresent address. Geological Survey of Japan, AIST,Tsukuba Central 1, +ῌ+ῌ+, Higashi, Tsukuba-city,Ibaraki, -*/ῌ2/01, Japan.
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Present address. Research center for Seismology,Volcanology, and Disaster Mitigation, Graduate
school of Nagoya University, Furo-cho, Chikusa-ku,Nagoya, Aichi, .0.ῌ20*,, Japan.
Corresponding author : Tomoki Tsutsui
e-mail : tom@geophys.mine.akita-u.ac.jp      2

a top face of Tertiary volcanic rocks as a substratum of Kusatsu-Shirane Volcano and is estimated at +1** m a. s.
l. in the craters. The horizon strikes NNE-SSW direction and dips eastward. Its dipping is not uniform andthere is a bench zone beneath the craters which strikes NNE-SSW direction. Seismicity beneath Mizugama crateris concentrated and the active magnetization region locates beneath the horizon. Other clear reﬂection events
within the substratum are also observed in the proﬁles but their geological correlation is not deﬁned. One ofdeeper horizon at +***m a. s. l. may correlate a sort of density contrast in Tertiary volcanics layer. Seismicity
along the traverse line tends to concentrate under the deeper horizon beneath Yugama crater. The density
contrast may constrain seismicity beneath the crater.
Key words : Kusatsu-Shirane volcano, Pseudo Reﬂection Proﬁling, Auto-correlation seismology, Logging, Controlled source seismology, Structure of volcano+ῌ ῏ ῍ ῐ ῎/  ,**.

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