摘要：We propose a generation mechanism of a giant earthquake of magnitude ( M ) ~9 in subduction zones where only M = 7 ~ 8 earthquakes have been identified and the surroundings of the source areas are sliding aseismically.In an M 9 event, both the M = 7 ~ 8 source areas and the surrounding area rupture seismically and the coseismic slip amount is one order larger than that of M = 7 ~ 8 earthquakes.To reproduce such behavior, we assume that an M 9 earthquake occurrence is the fundamental rupture mode in the subduction zone, and the M 9 source area is modeled as a large fracture energy area whose nucleation size is comparable to the size of the source area.The M = 7 ~ 8 asperities are modeled as smaller fracture energy areas whose nucleation size is smaller than the asperity size.Based on these assumptions, we demonstrate a simple numerical simulation of earthquake generation cycles.The results are qualitatively consistent with the characteristics of the 2011 off the Pacific coast of Tohoku Earthquake and a number of phenomena observed prior to this event. Key words Earthquake generation cycle hierarchical asperity model giant earthquake aseismic sliding subduction zone nucleation size fracture energy numerical simulation.
关键词：Earthquake generation cycle ;hierarchical asperity model ;giant earthquake ;aseismic sliding ;subduction zone ;nucleation size ;fracture energy ;numerical simulation
