Figure 17

Concept of earthquake faulting in subduction zones shown in schematic profile of the Nankai accretionary prism. (a) Previous view of seismogenic zone. Seismogenic zone shows velocity-weakening frictional behavior, whereas aseismic zone exhibits velocity-strengthening frictional behavior. (b) Improved view of earthquake faulting in subduction zones after fault rock studies in the NanTroSEIZE and the Shimanto accretionary complex. Fault segments showing velocity-strengthening behavior at low slip rates could be weakened as a result of dynamic weakening. This could occur at various depths in the subduction zone, in some cases resulting in shallow slip. In this conceptual model, the updip limit of the earthquake rupture zone corresponds to the location where dynamic weakening is no longer effective. Possible causes of earthquake rupture termination include viscous braking due to an increase in melt viscosity and ineffective thermal pressurization/fluidization due to increased effective normal stress associated with decreased fluid pressure.