Essential Maintenance: All Authorea-powered sites will be offline 9am-10am EDT Tuesday 28 May
and 11pm-1am EDT Tuesday 28-Wednesday 29 May. We apologise for any inconvenience.

loading page

Stress release process along an intraplate fault analogous to the plate boundary: a case study of the 2017 M5.2 Akita-Daisen earthquake, NE Japan
  • +3
  • Keisuke Yoshida,
  • Taka'aki Taira,
  • Yoshiaki Matsumoto,
  • Tatsuhiko Saito,
  • Kentaro Emoto,
  • Toru Matsuzawa
Keisuke Yoshida
Tohoku University, Tohoku University

Corresponding Author:[email protected]

Author Profile
Taka'aki Taira
University of California, Berkeley, University of California, Berkeley
Author Profile
Yoshiaki Matsumoto
Tohoku University, Tohoku University
Author Profile
Tatsuhiko Saito
National Research Institute for Earth Science and Disaster Resilience, National Research Institute for Earth Science and Disaster Resilience
Author Profile
Kentaro Emoto
Tohoku University, Tohoku University
Author Profile
Toru Matsuzawa
Tohoku University, Tohoku University
Author Profile

Abstract

Stress accumulation and release in the crust 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 in the crust. 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 towards the mainshock rupture area, suggesting that foreshocks were triggered by aseismic phenomena preceding the mainshock. 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 is attributed to the post-seismic aseismic slip of the mainshock. The postseismic slip possibly triggered repeating earthquakes with M ~3. We find that the foreshocks, mainshock, aftershocks, and post-seismic 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 crustal faults are fundamentally the same.
May 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 5. 10.1029/2020JB019527