Advanced Real Time Monitoring System and Simulation Researches for Earthquakes and Tsunamis in Japan - Post-Tsunami Hazard: Reconstruction and Restoration - page 175

Fig. 12.1 Imaged various structures of the subducting plate and surrounding area along the
Nankai trough
events, the 1944 Tonankai and the 1946 Nankai earthquakes, each hypocenter
was located off the Kii peninsula. We have carried out many seismic sur-
veys to understand structural elements (e.g., Yamamoto et al. 2013 ) concerned
in the recurrence cycle system of mega thrust earthquakes around the
Nankai trough. From the crustal structural researches, we found splay faults in
the Tonankai seismogenic zone (Park et al. 2002 ), the irregular structure off
Cape Shiono located at the boundary between the Tonankai and Nankai seis-
mogenic zones (Kodaira et al. 2004 ). The imaged irregular structures at the
segment boundary between the Tonankai and Nankai earthquake rupture zone,
seem to be controllers of the Nankai Trough mega-thrust seismogenic zone
system (Fig. 12.1 ).
Furthermore, the results of recent simulation study of mega-thrust earthquakes
recurrence cycles indicated that these irregular structures seem to act as a controller
of recurrence cycle and pattern of mega-thrust earthquakes in the Nankai trough
(Fig. 12.2 , Kodaira et al. 2006 ). And in these simulations, the fi rst ruptures were
starting from the Tonankai seismogenic zone ahead of the Nankai seismogenic
zone. These results were consistent with the past two earthquakes in 1854, 1944/1946
(Fig. 12.3 ). These results are very important and signifi cant for the Nankai trough
mega thrust earthquake researches.