![]() ![]() ![]() ![]() Studies of older tsunami deposits suggest a recurrence interval for megathrust earthquakes of 500–800 years (Sawai et al. This megathrust rupture reached to the trench with a maximum slip of 50 m (e.g., Yagi and Fukahata 2011) and resulted in a devastating tsunami. It was thought that the maximum magnitude for interplate earthquakes would be M8 based on modern earthquake observation (Yamanaka and Kikuchi 2004), until the M9 2011 Tohoku earthquake occurred. The Northeast (NE) Japan arc is a typical island arc formed by the subduction of the Pacific plate under the Eurasian plate. The rest of the long-term uplift may be attributed to indirect effects of internal deformation in the arc. Tectonic erosion explains up to about half of the long-term uplift by landward movement of arc topography. In contrast, the late-interseismic stage is dominated by the locking effect with the steady slip below the rupture area. In the early interseismic stage, the viscoelastic response to the megathrust earthquake dominates and can compensate for late-interseismic and coseismic subsidence. ![]() It is possible to explain the mismatch in the case where the rupture stops within the lithosphere. The model behaves differently when the rupture stops within the lithosphere and when it cuts through the lithosphere to reach the asthenosphere. To explain this mismatch between different periods, we modeled the entire megathrust earthquake cycle in the Northeast Japan arc using a simple dislocation model with a two-layered lithosphere–asthenosphere structure in which we account for viscoelastic relaxation in the asthenosphere and tectonic erosion. In Northeast Japan, it remains a puzzle to reconcile the mismatch between long-term (geological) uplift and late-interseismic and coseismic subsidence associated with the 2011 Tohoku earthquake. ![]()
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