The decorrelation and Gaussian smoothing method is implemented in GRACE monthly gravity field products to obtain annual and seasonal gravity changes in Japan and its vicinity,as well as time series gravity changes of several points.Results show regional gravity fields in Japan and its vicinity varied from positively to negatively and from area to area in five years before the Japan MW 9.0 earthquake,obviously positive to negative gravity changes were formed in 1~2 years.Time series gravity changes of several points indicate the Japan earthquake displayed the similar time variation gravity phenomenon with the 1976 Tangshan earthquake in China.These results reflect mass migration,mass movement and energy accumulation in Japan and its vicinity before the earthquake occurred.%利用GRACE重力卫星月重力场数据,通过去相关与高斯滤波等方法获取日本大地震震前震源区周缘年度、季度和年度差分重力变化,以及若干点位时间序列重力变化。分析结果表明：日本大地震前5年内在震源区周边出现了比较明显的卫星重力异常正负交替和迁移现象,至震前1～2年,震区周边形成了明显正负异常区,正重力异常区重力增加现象明显。点位重力时间序列分布指出日本MW9.0级地震前存在与1976年唐山地震类似的重力变化现象。反映出日本大地震震前震源区周边地下物质运动、质量迁移和能量积累等问题。
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