Spatiotemporal evolution of the slip velocities. Spatiotemporal evolution of the slip velocities at ξ = 60 and 175 km along the dip direction (see Figure 2b), where lie, respectively, shallow (a , c , e , g) and deep (b , d , f , h) belts of small asperity. (a-d) Overview for one cycle of a megathrust earthquake with the WCM (a, b) and the SCM (c, d). (e-h) Close-up of the SCM for the interseismic (e, f) and preseismic (g, h) stages. The initial time is taken as the onset of a megathrust earthquake. The time scale ratio is the same for both the WCM and the SCM. The scale colors are the same as in Figure 4. Green ellipses indicate isolated VLFEs.