TY - JOUR
T1 - Seismic evidence of fluid migration in northeastern Japan after the 2011 Tohoku-Oki earthquake
AU - Wang, Qing Yu
AU - Campillo, Michel
AU - Brenguier, Florent
AU - Lecointre, Albanne
AU - Takeda, Tetsuya
AU - Yoshida, Keisuke
N1 - Funding Information:
We are grateful to the two anonymous reviewers for their careful reading and valuable comments. The authors want to thank Mariano Supino for the contribution on LFEs catalog, Hisashi Nakahara, Takeshi Nishimura, Kiwamu Nishida, Yosuke Aoki, and Kaoru Sawazaki for fruitful discussions. Q.-Y. Wang specially thanks William Frank and support from NSF-EAR award #1920921 on finishing this paper. This work was supported by the European Research Council (ERC) under the European Union Horizon 2020 Research and Innovation Program (Grant Agreement 742335, F-IMAGE). Most of the computations presented in this paper were performed using the GRICAD infrastructure (https://gricad.univ-grenoble-alpes.fr), which is supported by Grenoble research communities.
Funding Information:
We are grateful to the two anonymous reviewers for their careful reading and valuable comments. The authors want to thank Mariano Supino for the contribution on LFEs catalog, Hisashi Nakahara, Takeshi Nishimura, Kiwamu Nishida, Yosuke Aoki, and Kaoru Sawazaki for fruitful discussions. Q.-Y. Wang specially thanks William Frank and support from NSF -EAR award # 1920921 on finishing this paper. This work was supported by the European Research Council (ERC) under the European Union Horizon 2020 Research and Innovation Program (Grant Agreement 742335 , F-IMAGE). Most of the computations presented in this paper were performed using the GRICAD infrastructure ( https://gricad.univ-grenoble-alpes.fr ), which is supported by Grenoble research communities .
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/6/1
Y1 - 2021/6/1
N2 - We use ambient-noise-based seismic monitoring to detect an anomalous seismic velocity decrease (∼0.01%) widely distributed in Honshu that arose about 1 year after the 2011 Mw 9.0 Tohoku-Oki earthquake. The anomaly is located along the central quaternary volcanic axis, and it suggests that the changes are related to volcanic processes. After correction for possible external environmental forcing-related velocity changes, the anomaly in the seismic velocity remains, which implies that it is associated with some internal physical process. We show a general strong positive correlation between the seismic velocity changes and the intensity of ground motion derived from the daily cumulative seismic moment. However, the lack of correlation during the anomaly itself reveals that this reduction is not directly caused by earthquake shaking. Tiltmeter low-pass observations show temporal variations that are correlated with the velocity changes. These observations strengthen the hypothesis of actual physical deformation. A previously reported decrease in fault strength (∼10%) for the same period as the velocity anomaly further supports a physical property change in the upper crust. We also note a simultaneous increase in activity of low-frequency events in the volcanic area, which suggests an increase in pore pressure in the upper crust. We propose that the observed anomalous seismic velocity decrease in early 2012 is due to an increase in pore pressure induced by an upward fluid migration, which at the same time triggered the increase in fluid-driven swarm seismicity and low-frequency events. We recall the depth-dependent seismic velocity changes in Honshu and derive an average diffusion of 1 m2/s over around 11 months after the Tohoku-Oki earthquake.
AB - We use ambient-noise-based seismic monitoring to detect an anomalous seismic velocity decrease (∼0.01%) widely distributed in Honshu that arose about 1 year after the 2011 Mw 9.0 Tohoku-Oki earthquake. The anomaly is located along the central quaternary volcanic axis, and it suggests that the changes are related to volcanic processes. After correction for possible external environmental forcing-related velocity changes, the anomaly in the seismic velocity remains, which implies that it is associated with some internal physical process. We show a general strong positive correlation between the seismic velocity changes and the intensity of ground motion derived from the daily cumulative seismic moment. However, the lack of correlation during the anomaly itself reveals that this reduction is not directly caused by earthquake shaking. Tiltmeter low-pass observations show temporal variations that are correlated with the velocity changes. These observations strengthen the hypothesis of actual physical deformation. A previously reported decrease in fault strength (∼10%) for the same period as the velocity anomaly further supports a physical property change in the upper crust. We also note a simultaneous increase in activity of low-frequency events in the volcanic area, which suggests an increase in pore pressure in the upper crust. We propose that the observed anomalous seismic velocity decrease in early 2012 is due to an increase in pore pressure induced by an upward fluid migration, which at the same time triggered the increase in fluid-driven swarm seismicity and low-frequency events. We recall the depth-dependent seismic velocity changes in Honshu and derive an average diffusion of 1 m2/s over around 11 months after the Tohoku-Oki earthquake.
KW - fault strength
KW - fluid migration
KW - low frequency earthquakes
KW - pore pressure
KW - seismic velocity drop anomaly
KW - tiltmeter observation
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U2 - 10.1016/j.epsl.2021.116894
DO - 10.1016/j.epsl.2021.116894
M3 - Article
AN - SCOPUS:85103129706
VL - 563
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
M1 - 116894
ER -