Title: | Focal mechanisms and the stress field in the aftershock area of the 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7) |
Authors: | Susukida, Yuki Browse this author |
Katsumata, Kei Browse this author →KAKEN DB |
Ichiyanagi, Masayoshi Browse this author |
Ohzono, Mako Browse this author |
Aoyama, Hiroshi Browse this author |
Tanaka, Ryo Browse this author |
Takada, Masamitsu Browse this author |
Yamaguchi, Teruhiro Browse this author |
Okada, Kazumi Browse this author |
Takahashi, Hiroaki Browse this author |
Sakai, Shin'ichi Browse this author |
Matsumoto, Satoshi Browse this author |
Okada, Tomomi Browse this author |
Matsuzawa, Toru Browse this author |
Miyamachi, Hiroki Browse this author |
Hirano, Shuichiro Browse this author |
Yamanaka, Yoshiko Browse this author |
Horikawa, Shinichiro Browse this author |
Kosuga, Masahiro Browse this author |
Katao, Hiroshi Browse this author |
Iio, Yoshihisa Browse this author |
Nagaoka, Airi Browse this author |
Tsumura, Noriko Browse this author |
Ueno, Tomotake Browse this author |
Miyakawa, Koji Browse this author |
Tanaka, Shin'ichi Browse this author |
Ando, Miwako Browse this author |
Uchida, Naoki Browse this author |
Azuma, Ryosuke Browse this author |
Takagi, Ryota Browse this author |
Yoshida, Keisuke Browse this author |
Nakayama, Takashi Browse this author |
Hirahara, Satoshi Browse this author |
Terakawa, Toshiko Browse this author |
Maeda, Yuta Browse this author |
Miyamachi, Hiroki Browse this author |
Yakiwara, Hiroshi Browse this author |
Keywords: | The Hokkaido Eastern Iburi earthquake |
Reverse fault |
Aftershock distribution |
Focal mechanism solution |
Temporary seismic network |
Stress inversion |
Issue Date: | 1-Dec-2021 |
Publisher: | Springer |
Journal Title: | Earth planets and space |
Volume: | 73 |
Issue: | 1 |
Start Page: | 1 |
Publisher DOI: | 10.1186/s40623-020-01323-x |
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) - sigma(2))/(sigma(1) - sigma(3)) is 0.61 +/- 0.13 in the whole aftershock area. Although not statistically significant, we suggest that R decreases systematically as the depth is getting deep, which is modeled by a quadratic polynomial of depth. |
Rights: | https://creativecommons.org/licenses/by/4.0/ |
Type: | article |
URI: | http://hdl.handle.net/2115/80415 |
Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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