Stress before and after the 2011 great Tohoku-oki earthquake and induced earthquakes in inland areas of eastern Japan

• Published in: Geophysical research letters Vol. 39; no. 3
• Main Authors: Yoshida, Keisuke, Hasegawa, Akira, Okada, Tomomi, Iinuma, Takeshi, Ito, Yoshihiro, Asano, Youichi
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-02-2012; American Geophysical Union; John Wiley & Sons, Inc
• Subjects: 2011 great Tohoku-oki earthquake; deviatoric stress magnitude; Earth sciences; Earth, ocean, space; Earthquakes; Exact sciences and technology; induced earthquakes; Nuclear power plants; Seismic activity; Spacetime; stress tensor inversion; Asia; Honshu; Japan; Aomori Japan; Tohoku; Far East; Iwaki; orientation; stress fields; urban areas; Principal stress; induced earthquakes; focal mechanism; seismicity
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2011GL049729

Stress fields in inland areas of eastern Japan before and after the Tohoku‐oki earthquake were estimated by inverting focal mechanism data. Before the earthquake,σ1axis was oriented EW in Tohoku but NW‐SE in Kanto‐Chubu. The stress fields changed after the earthquake in northern Tohoku and in southeastern Tohoku near Iwaki city, where the orientations of the principal stresses became approximately the same as the orientations of the static stress change associated with the earthquake. This indicates that differential stress magnitudes in these areas before the earthquake were smaller than 1 MPa. The stress field did not change in central Tohoku, even though the stresses loaded after the earthquake had nearly reversed orientations, which indicates that the differential stress magnitudes there were significantly larger than 1 MPa. In Kanto‐Chubu, stresses having nearly the same orientations as the background stresses were loaded after the earthquake, and the stress fields did not change as expected. This may have caused very high induced seismicities in Kanto‐Chubu.
Key Points
Stress change in N and SE Tohoku suggesting small differential stress magnitudes
No stress change in C Tohoku suggesting stress magnitudes greater than a few MPa
Remarkable induced seismicity in Kanto‐Chubu caused by simple stress increase