【摘要】 根据GRACE重力场月均值结果,结合300 km平滑半径的扇形滤波器,计算了地面0.5°网格点上的重力扰动的时间变化,并利用经验正交函数方法对重力扰动值进行分析,获得与地震相关的同震重力扰动变化。结果显示,对于苏门答腊、智利和日本三次大地震,采用经验正交函数方法能够很好地获得地震同震重力扰动的变化;而对于汶川地震,由于震级相对较小,同震信号完全湮没在其他信号及误差中,因而无法获得其同震重力变化。为了检验多大的地震引起的同震重力信号能够从GRACE重力场结果中提取出来,以汶川地震为例,将理论计算的地震重力扰动加入到由GRACE重力场观测结果计算的重力扰动中,然后用经验正交函数方法对其进行分析。模拟结果表明,当震级大于Mw8.8时,地震的同震信号能够被分析出来;而当震级小于Mw8.6时,则不能分离出同震信号;震级介于Mw8.6～8.8时,有可能分离出同震信号。更多还原

【Abstract】 The EOF method was used to extract coseismic gravity signals from GRACE monthly gravity field data.Because the GRACE satellites can’t sensor the gravity changes due to vertical displacement of the Earth’s surface,the gravity disturbance is used as the target signal.First,the temporal gravity disturbances at the grid points,with 0.5° resolution,on the Earth’s surface were calculated according to the GRACE monthly gravity field results,in which the 300 km fan-filter was used.And then the EOF method was applied to these temporal gravity disturbances to obtain the coseismic signals.The results show that the coseismic signals due to the recent 3 huge earthquakes,i.e.occurred in Sumatra,Chile and Japan,were successfully extracted,whereas the coseismic signals due to the Wenchuan earthquake,with relatively smaller magnitude,was not extracted because the signals are inundated by other signals and the error of GRACE data.In order to obtain the knowledge of how large an earthquake whose coseismic signal can be extracted from GRACE data should be,a simulation study was carried out by adding a known signal which was calculated in terms of the focal parameters of the Wenchuan earthquake according to dislocation theory,but with different magnitude.The simulation shows that the coseismic signal can be extracted when the magnitude reaches to Mw8.8 or larger;it is difficult to be extracted when the magnitude is smaller than Mw8.6;and it is possible to be extracted when the magnitude is between Mw8.6 and Mw8.8.更多还原