| 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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