Are the frictional properties of creeping faults persistent? Evidence from rapid afterslip following the 2011 Tohoku-oki earthquake

Geophysical observations and numerical studies have shown that creeping portions of faults have persistent rate-strengthening frictional properties and can act as barriers to earthquake rupture propagation. On the basis of GPS data following the 2011 M-W 9.0 Tohoku-oki earthquake in Japan, we find that the evolution of afterslip and postseismic shear stress on the plate interface is inconsistent with persistent rate-strengthening frictional properties but is consistent with slip-rate-dependent frictional properties that exhibit less rate-strengthening with increasing slip rate. Such slip-rate-dependent frictional properties tend to prevent creeping regions from acting as barriers to rupture propagation and therefore could be an important factor in determining the spatial extent of individual earthquakes..