TY - JOUR
T1 - Migration of seismic activity during the 1998 volcanic unrest at Iwate volcano, northeastern Japan, with reference to P and S wave velocity anomaly and crustal deformation
AU - Tanaka, Satoru
AU - Hamaguchi, Hiroyuki
AU - Ueki, Sadato
AU - Sato, Minemori
AU - Nakamichi, Haruhisa
N1 - Funding Information:
We are grateful to the staff of the RCPEV, Tohoku University for the maintenance of the observation network and valuable discussions. D. Zhao kindly provided his tomography code. T. Dixon gave us valuable suggestions for improving the manuscript. All the figures in this paper are plotted with the GMT system ( Wessel and Smith, 1991 ). The field work was partly supported by the special grant in 1998 from the Ministry of Education and Culture and by Grant-in Aid for Scientific Research (C) (2) 09640499 to S.U.
PY - 2002/3/30
Y1 - 2002/3/30
N2 - We describe the seismicity at Iwate volcano, northeastern Japan, during the volcanic unrest of 1998 with reference to a three-dimensional P and S wave velocity model from tomographic analysis. The abnormal seismic activity beneath Iwate volcano started under the caldera in February, 1998 and migrated westward in the period February to August, 1998. Previous geodetic modeling [Sato and Hamaguchi, Chikyu Monthly 21 (1999) 312-317] suggested the growth of a dike in the time of the seismic activity. Comparing the seismicity and dike extension with the tomographic images of the P and S wave velocity structure, we find that the trace of the growing dike coincides with the region of the high Vp and high Vp/Vs ratio beneath the volcano. The seismic and geodetic data are consistent with an intrusion of magma or other fluid under the caldera in 1998. Another pressure source causing the predominant crustal deformation at Iwate volcano was detected from geodetic data, which was located in the region with high Vp/Vs ratio under the western end of the volcano through the period from February to August. It is suggested that the activation of the point pressure source probably associated with the inflation of a hot fluid reservoir relate to a geothermal region adjacent to the western edge of the volcano.
AB - We describe the seismicity at Iwate volcano, northeastern Japan, during the volcanic unrest of 1998 with reference to a three-dimensional P and S wave velocity model from tomographic analysis. The abnormal seismic activity beneath Iwate volcano started under the caldera in February, 1998 and migrated westward in the period February to August, 1998. Previous geodetic modeling [Sato and Hamaguchi, Chikyu Monthly 21 (1999) 312-317] suggested the growth of a dike in the time of the seismic activity. Comparing the seismicity and dike extension with the tomographic images of the P and S wave velocity structure, we find that the trace of the growing dike coincides with the region of the high Vp and high Vp/Vs ratio beneath the volcano. The seismic and geodetic data are consistent with an intrusion of magma or other fluid under the caldera in 1998. Another pressure source causing the predominant crustal deformation at Iwate volcano was detected from geodetic data, which was located in the region with high Vp/Vs ratio under the western end of the volcano through the period from February to August. It is suggested that the activation of the point pressure source probably associated with the inflation of a hot fluid reservoir relate to a geothermal region adjacent to the western edge of the volcano.
KW - Crustal deformation
KW - Seismic tomography
KW - Seismicity
KW - Volcanic unrest
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U2 - 10.1016/S0377-0273(01)00273-6
DO - 10.1016/S0377-0273(01)00273-6
M3 - Article
AN - SCOPUS:0037197158
VL - 113
SP - 399
EP - 414
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
SN - 0377-0273
IS - 3-4
ER -