Abstract��The dynamic environment of the Ms9.0 earthquake off the east coast of Honshu,Japan preliminarily discussed by using Japanese lacal geological structure,plate tectonics,post and co��smemic displacement at GPS stations in Japan area,focal mechanisms and so on.It can be compresses judged that the earthquake might happen in this way that the Pacific plate dives and compresses to below Eurasian plate, the stress between Pacific plate and Eurasian plate accumulates along with time, when the stress/strain intensity exceeds friction intensity or stress intensity of rock,thus the fault which at the depth of 10-20 km in the Eurasian plate became a thrust fault whose dip angle less than Wadati��Benioff belt��s, and the earthquake occared.This earthquake makes a fault zone with about 600 km length and nearly the same strike as Wadati��Benioff��s.The fault zone located at the boundary between Pacific plate and Eurasian plate close to south��north strike.
