The 2018 Hokkaido Eastern Iburi earthquake (M JMA = 6.7) was triggered by a strike-slip faulting in a stepover segment: insights from the aftershock distribution and the focal mechanism solution of the main shock

the Group for the Aftershock Observations of the 2018 Hokkaido Eastern Iburi Earthquake

Research output: Contribution to journalArticle

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Abstract

The Hokkaido Eastern Iburi earthquake (MJMA = 6.7) occurred on September 6, 2018, in the Hokkaido corner region where the Kurile and northeastern Japan island arcs meet. We relocated aftershocks of this intraplate earthquake immediately after the main shock by using data from a permanent local seismic network and found that aftershock depths were concentrated from 20 to 40 km, which is extraordinarily deep compared with other shallow intraplate earthquakes in the inland area of Honshu and Kyushu, Japan. Further, we found that the aftershock area consists of three segments. The first segment is located in the northern part of the aftershock area, the second segment lies in the southern part, and the third segment forms a stepover between the other two segments. The hypocenter of the main shock, from which the rupture initiated, is located on the stepover segment. The centroid moment tensor solution for the main shock indicates a reverse faulting, whereas the focal mechanism solution determined by using the first-motion polarity of the P wave indicates strike-slip faulting. To explain this discrepancy qualitatively, we present a model in which the rupture started as a small strike-slip fault in the stepover segment of the aftershock area, followed by two large reverse faulting ruptures in the northern and southern segments.[Figure not available: see fulltext.].

Original languageEnglish
Article number53
Journalearth, planets and space
Volume71
Issue number1
DOIs
Publication statusPublished - Dec 1 2019

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focal mechanism
aftershock
faulting
slip
earthquakes
shock
earthquake
rupture
centroid moment tensor
Japan
strike-slip fault
P-wave
island arc
island arcs
distribution
P waves
centroids
polarity
tensors
moments

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

Cite this

The 2018 Hokkaido Eastern Iburi earthquake (M JMA = 6.7) was triggered by a strike-slip faulting in a stepover segment : insights from the aftershock distribution and the focal mechanism solution of the main shock. / the Group for the Aftershock Observations of the 2018 Hokkaido Eastern Iburi Earthquake.

In: earth, planets and space, Vol. 71, No. 1, 53, 01.12.2019.

Research output: Contribution to journalArticle

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abstract = "The Hokkaido Eastern Iburi earthquake (MJMA = 6.7) occurred on September 6, 2018, in the Hokkaido corner region where the Kurile and northeastern Japan island arcs meet. We relocated aftershocks of this intraplate earthquake immediately after the main shock by using data from a permanent local seismic network and found that aftershock depths were concentrated from 20 to 40 km, which is extraordinarily deep compared with other shallow intraplate earthquakes in the inland area of Honshu and Kyushu, Japan. Further, we found that the aftershock area consists of three segments. The first segment is located in the northern part of the aftershock area, the second segment lies in the southern part, and the third segment forms a stepover between the other two segments. The hypocenter of the main shock, from which the rupture initiated, is located on the stepover segment. The centroid moment tensor solution for the main shock indicates a reverse faulting, whereas the focal mechanism solution determined by using the first-motion polarity of the P wave indicates strike-slip faulting. To explain this discrepancy qualitatively, we present a model in which the rupture started as a small strike-slip fault in the stepover segment of the aftershock area, followed by two large reverse faulting ruptures in the northern and southern segments.[Figure not available: see fulltext.].",
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AU - Katsumata, Kei

AU - Ichiyanagi, Masayoshi

AU - Ohzono, Mako

AU - Aoyama, Hiroshi

AU - Tanaka, Ryo

AU - Takada, Masamitsu

AU - Yamaguchi, Teruhiro

AU - Okada, Kazumi

AU - Takahashi, Hiroaki

AU - Sakai, Shin’ichi

AU - Matsumoto, Satoshi

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AU - Matsumoto, Satoshi

AU - Hirano, Shuichiro

AU - Terakawa, Toshiko

AU - Horikawa, Shinichiro

AU - Kosuga, Masahiro

AU - Katao, Hiroshi

AU - Iio, Yoshihisa

AU - Nagaoka, Airi

AU - Tsumura, Noriko

AU - Ueno, Tomotake

AU - Katsumata, Kei

AU - Miyakawa, Koji

AU - Tanaka, Shin’ichi

AU - Ando, Miwako

AU - Uchida, Naoki

AU - Azuma, Ryosuke

AU - Takagi, Ryota

AU - Yoshida, Keisuke

AU - Nakayama, Takashi

AU - Hirahara, Satoshi

AU - Yamanaka, Yoshiko

AU - Maeda, Yuta

AU - Miyamachi, Hiroki

AU - Yakiwara, Hiroshi

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AU - Shimazaki, Masahiro

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