Episodic slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake

Yoshihiro Ito, Ryota Hino, Motoyuki Kido, Hiromi Fujimoto, Yukihito Osada, Daisuke Inazu, Yusaku Ohta, Takeshi Iinuma, Mako Ohzono, Satoshi Miura, Masaaki Mishina, Kensuke Suzuki, Takeshi Tsuji, Juichiro Ashi

Research output: Contribution to journalArticlepeer-review

277 Citations (Scopus)


We describe two transient slow slip events that occurred before the 2011 Tohoku-Oki earthquake. The first transient crustal deformation, which occurred over a period of a week in November 2008, was recorded simultaneously using ocean-bottom pressure gauges and an on-shore volumetric strainmeter; this deformation has been interpreted as being an M6.8 episodic slow slip event. The second had a duration exceeding 1. month and was observed in February 2011, just before the 2011 Tohoku-Oki earthquake; the moment magnitude of this event reached 7.0. The two events preceded interplate earthquakes of magnitudes M6.1 (December 2008) and M7.3 (March 9, 2011), respectively; the latter is the largest foreshock of the 2011 Tohoku-Oki earthquake. Our findings indicate that these slow slip events induced increases in shear stress, which in turn triggered the interplate earthquakes. The slow slip event source area on the fault is also located within the downdip portion of the huge-coseismic-slip area of the 2011 earthquake. This demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault, suggesting that the faults undergo slip in slow slip events can also rupture seismically.

Original languageEnglish
Pages (from-to)14-26
Number of pages13
Publication statusPublished - 2013 Jul 17


  • Earthquake triggering
  • Ocean-bottom pressure
  • Slow slip event
  • Subduction zone
  • The 2011 Tohoku-Oki earthquake
  • Volumetric strain


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