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2019-10-01 Seismic campaign in Showa-Shinzan lava dome in Usu Volcano, Northern Japan
1. Seismic campaign in Showa-
Shinzan lava dome in Usu
Volcano, Northern Japan
1 October, 2019
ISTerre, France
A. Takeo1, K. Nishida1, Y. Aoki1, H. Aoyama2, M. Ishise1,
T. Maeda3, Y. Mizutani1, T. Kai1, Y. Nakashima1, S. Nagahara1,
R. Kurihara1, L. Ye4, X. Wang5, T. Akuhara1
1ERI, Univ. Tokyo, 2Hokkaido Univ., 3Hirosaki Univ.
4Sun Yat-sen Univ., 5Southwest Jiaotong Univ.
2. Internal structure of lava domes
Goto & McPhie (JVGR, 1998)
In-situ observation of exposures can view only the shallowest
part of the intruded lava.
3. Usu Volcano and Showa-Shinzan lava dome
1910
Activity time
Eruptive
Interval (yr)
Location Eruption type
Upheaval
height (m)
July ̶ Nov. 1910 57 North flank Phreatic 170
Dec. 1943 ̶ Sep.
1945
33 East flank Phreatomagmatic 280
Aug. 1977 ̶ Mar.
1982
32 Summit Phreatomagmatic 180
Mar. ̶ Aug. 2000 18 West flank Phreatomagmatic 80
5. Muon radiography + Gravity
1910
図2. 三松ダイ アグラ ムと
隆起中の火口写真(三松2004; 加筆)
山頂
図4. 密度構造(Nishiyama et al. 2017より )
High density at the core of
the lava dome.
Seismic velocity combined
with density gives elastic
constants, thus material
properties.
6. Seismic campaign
1910
22 1-Hz seismometers
(7 on the summit, 10
on the flank, and 5 on
the foot)
Instrumental response
pre-calibrated.
Recorded ambient
noise to infer the
velocity structure
て暫定1次元速度構造を推定し た。
の順にS波速度が速いこ と がわかっ た。