Advanced Real Time Monitoring System and Simulation Researches for Earthquakes and Tsunamis in Japan - Post-Tsunami Hazard: Reconstruction and Restoration - page 179

Fig. 12.6 Estimated phenomena for improvement of prediction researches. At the stations of
DONET2 ( green and blue colored), subsidence is expected fi rst because the afterslip occurs away
from the stations. Then, the afterslip propagates below the blue stations and uplift is observed
there. On the other hand, the slip does not reach below the green stations, subsidence continues
there. Finally, slip is accelerated to become Nankai earthquake

12.3 Off East Japan Seismogenic Zone

12.3.1 Mechanism of the East Japan Earthquake in 2011

A M9 great earthquake occurred around East Japan in March 11 2011. This earth-
quake generated the large tsunami and damaged many coastal cities along the
Pacifi c. According to the observations around the east Japan seismogenic zone,
average seismic coupling is less than 30 % (e.g. Peterson and Seno 1984 ). The sta-
ble slip was expected for the remaining 70 % of the relative plate motion. It gener-
ally defi ned that the stable slip zone doesn't accumulate the stress around the plate
boundary. Therefore, we speculated that the Off East Japan seismogenic zone was
composed of small and medium size asperities (Yamanaka and Kikuchi 2004 ). The
severe stress accumulation that causes the great earthquake was not expected in the
region before the 2011 Great East Japan earthquake. However, the estimated slip
zone of the 2011 East Japan Earthquake was overlapped with the assumed stable
slip zones. Figure 12.7 shows the difference of bathymetry around off Miyagi near
the epicenter of 2011 East Japan Earthquake (Fujiwara et al. 2011 ; Kodaira et al. 2012 ).