Fig. 10.

2D Model and numerical results of the vertical deformation during the Tohoku-oki earthquake cycle. After Sasajima et al. (2019). a Rheological structure (viscosity distribution) in a finite element model. The white line indicates the complete coupled zone, providing the backslip between earthquakes. The plate boundary at the deep extension of the coupled zone comprises a thin (~ 3 km) viscoelastic layer (red zone) with a low viscosity that almost freely creeps during the interseismic period. The viscosity distribution is established based on pressure, water fugacity, assumed strain rate, and mineral flow laws. b Modeling results of the interplate coupling in the megathrust earthquakes. The vertical displacement rates are obtained from the observations and simulations. The black dots indicate the surface vertical displacement rates for approximately 100 years before the Tohoku-oki earthquake based on the level survey observations in the area between the two black lines in Fig. 8. Each colored line illustrates the vertical displacement rates at the elapsed time \(t^{\prime }\) after the asperities of the megathrust earthquakes have been coupled. The location of the volcanic front is indicated by the pink vertical dashed line. The simulation results show that the subsidence rate in the Pacific coastal region increases toward the latter half of the megathrust earthquake cycle, and the results after 500–600 years are roughly in good agreement with the level survey observations. c Cross section of the 2D model with the plate boundary conditions. The green line is the plate boundary. d The slip deficit velocities at the plate boundary and the ductile shear zone obtained by the model are represented by the solid and dashed lines. The horizontal solid line shows the slip deficit velocity (8.35 cm/yr) under complete coupling