日本9.0级地震区重力梯度的时空分布

TEMPORAL AND SPACE CONTRIBUTION OF GRAVITY GRADIENTS IN JAPAN M_W 9. 0 EARTHQUAKE AREA

基于重力梯度的球函数表式关系,采用2003年1月至2012年11月的112期月GRACE观测数据,计算了2011年日本9.0级地震区域的6个重力梯度分量的空间分布和地震区一些特征点在地震前重力梯度随时间的变化过程。结果表明:Tλλ、T rr、Tθλ与当地地质构造的分布有较好的对应关系。在日本9.0级地震前一年左右,重力梯度的6个分量不同程度上都存在震前异常变化,同震重力梯度变化明显。

Gravity gradient is the main physical parameters in gravity measurements,6 components of the gravi- ty gradient contain more information about the earth than usual gravity measurement. The co-seismic space distribu- tion and temporal variation of the gravity gradient are analized acooeding to the results computed with 112 periods GRACE observed during Jan. ,2003 and Jan. ,2012 for the area of Japan 9.0 earthquake, based on the spherical function formulas of the 6 components of the gravity gradient in earth fixed coordinate. The theory and methods to e- liminate singularity of the spherical function formulas of the 6 components of the gravity gradient are discussed. The results show that the component Tλλ, Trr, Tθλ of gravity gradients are consistent with the tectonics in the area. Tem- poral variation of the 6 components of the gravity gradient in about 1 year before the earthquake appeared anomaly, and the co-seismic variation of the 6 components of the gravity gradient are also obvious.