The occurrence of an M8-class, megathrust earthquake in the Tokai region, Japan, has been for decades of great seismic hazard concern. On August 11, 2009, the Suruga Bay earthquake, Mw6.4, occurred within the Philippine Sea plate, close to the source region of the anticipated Tokai earthquake.
In a study published in the "Nature Geoscience" journal, a team of researchers led by Dr. Shin Aoi (NIED) analyzed in detail the stress transfer on the Tokai plane due to the Suruga Bay event. Based on the precise relocation of aftershocks and waveform inversion, the authors construct the source model of the Suruga Bay earthquake, which enables them to calculate more precisely the associated co-seismic stress changes. The paper reports short-term triggering of seismicity at the plate interface by the static Coulomb stress changes induced by the Mw6.4 event. Moreover, the study finds that most of the presumed strongly-locked patches on the Tokai plane, known as asperities, are in areas of increased stress.
S. Aoi, B. Enescu, W. Suzuki, Y. Asano, K. Obara, T. Kunugi and K. Shiomi (2010), Stress transfer in the Tokai subduction zone from the 2009 Suruga Bay earthquake in Japan, Nature Geoscience, 3, doi:10.1038/ngeo885.