TY - JOUR
T1 - Stress Release Process Along an Intraplate Fault Analogous to the Plate Boundary
T2 - A Case Study of the 2017 M5.2 Akita-Daisen Earthquake, NE Japan
AU - Yoshida, Keisuke
AU - Taira, Taka'aki
AU - Matsumoto, Yoshiaki
AU - Saito, Tatsuhiko
AU - Emoto, Kentaro
AU - Matsuzawa, Toru
N1 - Funding Information:
We deeply thank the editor (Martha Savage), an associate editor, and three anonymous reviewers for their constructive comments, which helped to improve the manuscript. K. Y. thanks Akira Hasegawa for discussions about repeating earthquakes and postseismic slip and Hisahiko Kubo for discussions about waveform inversion. This study used hypocenters and P- and S-wave arrival time data reported in the unified catalog of the JMA (https://www.data.jma.go.jp/svd/eqev/data/bulletin/index_e.html). The seismograms were collected and stored by JMA, national universities, and National Research Institute for Earth Science and Disaster Resilience (http://www.hinet.bosai.go.jp/?LANG=en). The figures in this paper were created using GMT (Wessel & Smith, 1998). This research was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant JP 17K1437. Obtained results of hypocenters, focal mechanisms, and coseismic slip distribution are available at the website (http://www.aob.gp.tohoku.ac.jp/~yoshida/pub/JGR2020/).
Funding Information:
We deeply thank the editor (Martha Savage), an associate editor, and three anonymous reviewers for their constructive comments, which helped to improve the manuscript. K. Y. thanks Akira Hasegawa for discussions about repeating earthquakes and postseismic slip and Hisahiko Kubo for discussions about waveform inversion. This study used hypocenters and P‐ and S‐wave arrival time data reported in the unified catalog of the JMA ( https://www.data.jma.go.jp/svd/eqev/data/bulletin/index_e.html ). The seismograms were collected and stored by JMA, national universities, and National Research Institute for Earth Science and Disaster Resilience ( http://www.hinet.bosai.go.jp/?LANG=en ). The figures in this paper were created using GMT (Wessel & Smith, 1998 ). This research was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant JP 17K1437. Obtained results of hypocenters, focal mechanisms, and coseismic slip distribution are available at the website ( http://www.aob.gp.tohoku.ac.jp/~yoshida/pub/JGR2020/ ).
Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/5/1
Y1 - 2020/5/1
N2 - Stress accumulation and release inside the plate remains poorly understood compared to that at the plate boundaries. Spatiotemporal variations in foreshock and aftershock activities can provide key constraints on time-dependent stress and deformation processes inside the plate. The 2017 M5.2 Akita-Daisen intraplate earthquake in NE Japan was preceded by intense foreshock activity and triggered a strong sequence of aftershocks. We examine the spatiotemporal distributions of foreshocks and aftershocks and determine the coseismic slip distribution of the mainshock. Our results indicate that seismicity both before and after the mainshock was concentrated on a planar structure with N-S strike that dips steeply eastward. We observe a migration of foreshocks toward the mainshock rupture area, suggesting the possibility that foreshocks were triggered by aseismic phenomena preceding the mainshock rupture. The mainshock rupture propagated toward the north, showing less slip beneath foreshock regions. The stress drop of the mainshock was 1.4 MPa, and the radiation efficiency was 0.72. Aftershocks were intensely triggered near the edge of large coseismic slip regions where shear stress increased. The aftershock region expanded along the fault strike, which can be attributed to the postseismic aseismic slip of the mainshock. We find that the foreshocks, mainshock, aftershocks, and postseismic slip released stress at different segments along the fault, which may reflect differences in frictional properties. Obtained results were similar to those observed for interplate earthquakes, which supports the hypothesis that the deformation processes along plate boundaries and intraplate faults are fundamentally the same.
AB - Stress accumulation and release inside the plate remains poorly understood compared to that at the plate boundaries. Spatiotemporal variations in foreshock and aftershock activities can provide key constraints on time-dependent stress and deformation processes inside the plate. The 2017 M5.2 Akita-Daisen intraplate earthquake in NE Japan was preceded by intense foreshock activity and triggered a strong sequence of aftershocks. We examine the spatiotemporal distributions of foreshocks and aftershocks and determine the coseismic slip distribution of the mainshock. Our results indicate that seismicity both before and after the mainshock was concentrated on a planar structure with N-S strike that dips steeply eastward. We observe a migration of foreshocks toward the mainshock rupture area, suggesting the possibility that foreshocks were triggered by aseismic phenomena preceding the mainshock rupture. The mainshock rupture propagated toward the north, showing less slip beneath foreshock regions. The stress drop of the mainshock was 1.4 MPa, and the radiation efficiency was 0.72. Aftershocks were intensely triggered near the edge of large coseismic slip regions where shear stress increased. The aftershock region expanded along the fault strike, which can be attributed to the postseismic aseismic slip of the mainshock. We find that the foreshocks, mainshock, aftershocks, and postseismic slip released stress at different segments along the fault, which may reflect differences in frictional properties. Obtained results were similar to those observed for interplate earthquakes, which supports the hypothesis that the deformation processes along plate boundaries and intraplate faults are fundamentally the same.
KW - aseismic slip
KW - hypocenter migration
KW - intraplate earthquake
KW - pore pressure
KW - stress release
KW - waveform inversion
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U2 - 10.1029/2020JB019527
DO - 10.1029/2020JB019527
M3 - Article
AN - SCOPUS:85085299552
VL - 125
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
SN - 2169-9313
IS - 5
M1 - e2020JB019527
ER -