Fig. 7
Simulation model of earthquake cycles and viscoelastic flow in the Japan Trench subduction zone (Barbot 2020). a 2D cross sections of the parameters of the segmental structure of the subduction plate boundary and the viscoelastic structure of the medium. The VW and VS segments at the plate boundary are shown in yellow and gray, respectively; the two plates adhere deep in the brittle-plastic region. The background colors indicate the temperatures in the oceanic and mantle-wedge asthenosphere. The viscoelastic region is divided by a triangular mesh. Steady-state viscosity contours are shown in yellow, green, and blue profiles for 1020 Pa s, 1021 Pa s, and 1022 Pa s, respectively. The small numbers in the corners of the fault segments indicate the starting depths in the model. b and c Slip-velocity changes in the dip direction of the Megaspray and Megathrust faults over 1000 years. The dashed horizontal lines delineate the segment boundaries. The stars indicate the earthquake locations. They are color-coded by the peak slip velocity reached during the earthquake. Partial rupture is restricted to the forearc base. In megathrust earthquakes, the slip propagates to the trench and megasplay faults. All earthquakes are followed by postseismic slips. The event groups before and after the megathrust rupture correspond to foreshocks and aftershocks, respectively. d Change in slip velocity at the center of the VW segment and the peak velocity at all locations along the megathrust/megaspray system