摘要：The largest aftershock ( M w 7.8) of the giant M 9.0 Tohoku-oki earthquake occurred near the coast of Ibaraki Prefecture about thirty minutes after the main shock.We have imaged the rupture process of the M w 7.8 earthquake by back-projection of waveform data from the Metropolitan Seismic Observation network (MeSO-net).Original acceleration seismograms were integrated.They were then band-pass filtered in the frequency range of 0.1–1.0 Hz.We assumed a fault plane on the plate boundary with a dimension of 115 km ×175 km, and this was divided into 112 subfaults.Travel times from each of the subfaults to observation sites were calculated by using a 3-D velocity structure model.Applying the restrictions that the rupture velocity is smaller than 4 km/s and the rupture duration on each subfault is less than 25 s, we obtained a rupture propagation image by projecting the power of the stacked waveforms.Propagation of the rupture toward north and east was suppressed by the existence of those areas that had radiated a large seismic energy at the main shock occurrence, or at the occurrence of the M 7.0 earthquake in 2008.The westward propagation of the rupture stopped at the area where the Philippine Sea plate lies over the Pacific plate.
关键词：Rupture process ;back projection ;2011 Ibaraki-oki ;MeSO-net
