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