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Title: Nucleation process of the 2011 northern Nagano earthquake from nearby seismic observations
Authors: Shimojo, Kengo
Enescu, Bogdan  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0003-2153-0097 (unconfirmed)
Yagi, Yuji
Takeda, Tetsuya
Author's alias: 下條, 賢梧
エネスク, ボグダン
八木, 勇治
武田, 哲也
Keywords: Geophysics
Seismology
Issue Date: 16-Apr-2021
Publisher: Springer Nature
Journal title: Scientific Reports
Volume: 11
Thesis number: 8143
Abstract: The 2011 magnitude (M) 9.0 Tohoku-oki earthquake was followed by seismicity activation in inland areas throughout Japan. An outstanding case is the M6.2 Northern Nagano earthquake, central Japan, occurred 13-h after the megathrust event, approximately 400 km away from its epicenter. The physical processes relating the occurrence of megathrust earthquakes and subsequent activation of relatively large inland earthquakes are not well understood. Here we use waveform data of a dense local seismic network to reveal with an unprecedented resolution the complex mechanisms leading to the occurrence of the M6.2 earthquake. We show that previously undetected small earthquakes initiated along the Nagano earthquake source fault at relatively short times after the Tohoku-oki megathrust earthquake, and the local seismicity continued intermittently until the occurrence of the M6.2 event, being likely ‘modulated’ by the arrival of surface waves from large, remote aftershocks off-shore Tohoku. About 1-h before the Nagano earthquake, there was an acceleration of micro-seismicity migrating towards its hypocenter. Migration speeds indicate potential localized slow-slip, culminating with the occurrence of the large inland earthquake, with fluids playing a seismicity-activation role at a regional scale.
Description: 東北地方太平洋沖地震後に日本全国で発生した誘発地震のメカニズムを解析 --稠密地震観測網で捉えられた長野県北部の地震の前駆過程--. 京都大学プレスリリース. 2021-04-19.
High-density seismic network detected inland earthquake precursors. 京都大学プレスリリース. 2021-05-10.
Rights: © The Author(s) 2021
This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
URI: http://hdl.handle.net/2433/262698
DOI(Published Version): 10.1038/s41598-021-86837-4
Related Link: https://www.kyoto-u.ac.jp/ja/research-news/2021-04-19
https://www.kyoto-u.ac.jp/en/research-news/2021-05-10
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