Aseismic crustal movement in southern Ryukyu Trench, southwest Japan

Anomalous crustal deformation following the Mw = 7.1, March 31, 2002, Hualien earthquake was observed over 5 years using the global positioning system (GPS) network in the south Ryukyu Islands. The analysis showed an afterslip event at a depth of 30 km on the subducting Philippine Sea plate. The magnitude of the cumulative moment reached 7.4. The released moment of the afterslip exceeded the mainshock itself. The afterslip promoted Coulomb failure stress on the fault of the repeating slow slip events (SSEs) in the vicinity of the afterslip. The increase in the slip rate of the SSEs predicted through the change in the Coulomb failure stress is 13%. This is close to the observed increase in slip rate (19%) after the earthquake. This suggests that the afterslip had accelerated the slip rate of the SSEs after the earthquake. Citation: Nakamura, M. (2009), Aseismic crustal movement in southern Ryukyu Trench, southwest Japan, Geophys. Res. Lett., 36, L20312, doi: 10.1029/2009GL040357.