Complicated rupture process of the M_w 7.0 intraslab strike-slip earthquake in the Tohoku region on 10 July 2011 revealed by near-field pressure records

We examined fault models of the Tohoku strike-slip intraslab earthquake (M_w 7.0) on 10 July 2011 using near-field tsunami data. After constraining the strike and location of the fault from tsunami source distribution, we investigated fault models assuming simple rupture of one fault, and simultaneous rupture of two conjugate faults. The estimated single fault reached >30 km down into the slab from the plate interface, suggesting bending stress enhancement after the 2011 Tohoku-Oki earthquake, but the depth extent was inconsistent with the aftershock activity. The model involving conjugate faults extended ~20 km below the slab surface and was more consistent with the aftershocks. We concluded that it is more plausible that this earthquake involved two conjugate strike-slip faults, and the enhancement of the downdip extensional stress after Tohoku-Oki earthquake was not large enough to allow rupture to propagate deeply into the slab beneath the landward slope of the Japan Trench. Key Points An intraslab Tohoku strike-slip earthquake on July 2011 was studied with near-field pressure data Two orthogonal faults related to the downdip extensional stress were involved during the rupture Estimated stress change around the rupture area was smaller than that in the outer rise region.