Seismic Source Process of the 2011 Tohoku-oki Earthquake

We reported seismic waveform analysis results of the source process of the 2011 mega-thrust Tohoku-oki earthquake. The Tohoku-oki earthquake is the first mega-thrust earthquake in Japan since the initiation of modern and multi-channel seismic observation. Many researchers have performed source inversion using seismic waveforms observed at near-source or/and global seismic networks, and presented their seismic source models. As pointed out by some researchers, however, seismic source models for the 2011 Tohoku-oki earthquake are different from one another. The discrepancy has prevented us to understand the nature of mega-thrust earthquake in Tohoku-oki region, which may be originated from data processing manner, assumption of error structure, strength of constraints, and setting of source model. In this paper, we endeavor to describe detailed analysis procedure for each study. Common feature in slip distributions obtained by all studies is that the huge seismic slip located off the coast of Miyagi (Miyagi-oki) where huge slip deficit was detected by GPS studies. Many studies obtained the large rupture near Japan Trench or hypocenter during 45-70 sec after initial break, which may be a key of understanding this earthquake. At present, it is difficult to discuss the detailed rupture process of the 2011 Tohoku-oki earthquake. The future studies using multi-channel data analysis with proper error structure model will reveal the nature of mega-thrust earthquake.