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Focal mechanisms and the stress field in the aftershock area of the 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7)

Focal mechanisms and the stress field in the aftershock area of the 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7)

Authors :
Susukida, Yuki
1000010261281
Katsumata, Kei
Ichiyanagi, Masayoshi
Ohzono, Mako
Aoyama, Hiroshi
Tanaka, Ryo
Takada, Masamitsu
Yamaguchi, Teruhiro
Okada, Kazumi
Takahashi, Hiroaki
Sakai, Shin'ichi
Matsumoto, Satoshi
Okada, Tomomi
Matsuzawa, Toru
Miyamachi, Hiroki
Hirano, Shuichiro
Yamanaka, Yoshiko
Horikawa, Shinichiro
Kosuga, Masahiro
Katao, Hiroshi
Iio, Yoshihisa
Nagaoka, Airi
Tsumura, Noriko
Ueno, Tomotake
Miyakawa, Koji
Tanaka, Shin'ichi
Ando, Miwako
Uchida, Naoki
Azuma, Ryosuke
Takagi, Ryota
Yoshida, Keisuke
Nakayama, Takashi
Hirahara, Satoshi
Terakawa, Toshiko
Maeda, Yuta
Yakiwara, Hiroshi
Susukida, Yuki
1000010261281
Katsumata, Kei
Ichiyanagi, Masayoshi
Ohzono, Mako
Aoyama, Hiroshi
Tanaka, Ryo
Takada, Masamitsu
Yamaguchi, Teruhiro
Okada, Kazumi
Takahashi, Hiroaki
Sakai, Shin'ichi
Matsumoto, Satoshi
Okada, Tomomi
Matsuzawa, Toru
Miyamachi, Hiroki
Hirano, Shuichiro
Yamanaka, Yoshiko
Horikawa, Shinichiro
Kosuga, Masahiro
Katao, Hiroshi
Iio, Yoshihisa
Nagaoka, Airi
Tsumura, Noriko
Ueno, Tomotake
Miyakawa, Koji
Tanaka, Shin'ichi
Ando, Miwako
Uchida, Naoki
Azuma, Ryosuke
Takagi, Ryota
Yoshida, Keisuke
Nakayama, Takashi
Hirahara, Satoshi
Terakawa, Toshiko
Maeda, Yuta
Yakiwara, Hiroshi
Publication Year :
2021

Abstract

The tectonic stress field was investigated in and around the aftershock area of the Hokkaido Eastern Iburi earthquake (M-JMA = 6.7) occurred on 6 September 2018. We deployed 26 temporary seismic stations in the aftershock area for approximately 2 months and located 1785 aftershocks precisely. Among these aftershocks, 894 focal mechanism solutions were determined using the first-motion polarity of P wave from the temporary observation and the permanent seismic networks of Hokkaido University, Japan Meteorological Agency (JMA), and High Sensitivity Seismograph Network Japan (Hi-net). We found that (1) the reverse faulting and the strike-slip faulting are dominant in the aftershock area, (2) the average trend of P- and T-axes is 78 degrees +/- 33 degrees and 352 degrees +/- 51 degrees, respectively, and (3) the average plunge of P- and T-axes is 25 degrees +/- 16 degrees and 44 degrees +/- 20 degrees, respectively: the P-axis is close to be horizontal and the T-axis is more vertical than the average of the P-axes. We applied a stress inversion method to the focal mechanism solutions to estimate a stress field in the aftershock area. As a result, we found that the reverse fault type stress field is dominant in the aftershock area. An axis of the maximum principal stress (sigma(1)) has the trend of 72 degrees +/- 7 degrees and the dipping eastward of 19 degrees +/- 4 degrees and an axis of the intermediate principal stress (sigma(2)) has the trend of 131 degrees +/- 73 degrees and the dipping southward of 10 degrees +/- 9 degrees, indicating that both of sigma(1)- and sigma(2)-axes are close to be horizontal. An axis of the minimum principal stress (sigma(3)) has the dipping westward of 67 degrees +/- 6 degrees that is close to be vertical. The results strongly suggest that the reverse-fault-type stress field is predominant as an average over the aftershock area which is in the western boundary of the Hidaka Collision Zone. The average of the stress ratio R = (sigma(1)

Details

Database :
OAIster
Notes :
English
Publication Type :
Electronic Resource
Accession number :
edsoai.on1375209239
Document Type :
Electronic Resource