摘要
利用经过去相关滤波处理的GRACE时变重力场模型获得了青藏高原东缘2003—2012年的卫星年重力变化图像,并针对该区域近年发生的三次特大地震,结合震前及震后月重力场变化图像,分析与强震有关的卫星重力场变化特征。从区域年重力变化图像可以看出,三次大震均发生在年重力变化较低的时段内,震前小幅值变化可能是地震发生的中短期前兆;从汶川地震和玉树地震发生前后的月重力场变化图像可以发现,发震前后断层附近的重力变化模式发生变化,这可能印证了震后位场变化恢复理论;从汶川地震前后的龙门山断层附近点上的周重力变化趋势可以明显发现,汶川地震发生(第20周)后近9周的时间,断层东西侧呈现了相反的重力变化特征,这可能是对震后壳幔物质调整过程的反映。
In this paper,we calculate annual satellite gravity changes in the eastern margin of the Tibetan Plateau from 2003 to 2012 by using the Gravity Recovery and Climate Experiment （GRACE） time-variable gravity field models with decorrelated filtering. By contraposing the three strong earthquakes that occurred recently in this region,including the Wenchuan Ms8.0,Yushu MsT. 1 ,and Ya＇ an MsT. 0 earthquakes,we analyze the changes in satellite gravity field features related to the strong earthquakes with the annual gravity changes before and after each earthquake. For analyzing the relationship between these earthquakes and the gravity change mode in detail, we also caculate the monthly gravity change for the Wenchuan MsS. 0 and Yushu MsT. 1 earthquakes. Moreover, we use the recently relesed weekly GRACE gravity models to caculate the point-wise gravity change near Longmenshan fault for the Wenchuan Ms8.0 earthquake. The regional annual differentiated dynamic gravity changes image indicates that all three earthquakes occurred in a period of small gravity change, which means a small migration of crust-mantle material occurred according to the mantle convection theory. The same feature is indicated in the regional annual cumulative dynamic gravity changes image. These gravity changes likely indicate a medium-short term earthquake precursor. In the monthly differentiated dynamic gravity changes image,the gravity change mode shows significant changes in both the Wenchuan Ms8.0 earthquake and the Yushu Ms7. 1 earthquake,which indicates that the gravity gradient change direction al- tered from perpendicular to the plane of a fault to parallel. These change in the gravity change mode may confirm the theory of post-earthquake potential field restoration. The nine points of the weekly gravity change sequences in Longmenshan fault area that occurred during 2008 indicate that a nearly nine-week contrary gravity change trend occurred between the eastern and western areas of the fault after the occurrence of the Wenchuan MsS. 0 earthquake. These gravity mode changes may be the reflection of an adjustment procedure of the crust-mantle material after the earthquake. Gravity measurement is an important subject in earthquake prediction research. Satel- lite temporal gravity analysis greatly enriches and complements the deficiency of the ground gravity network in time and space scales and can be quickly used for the study of crustal movement and earthquake prediction.
出处
《地震工程学报》
CSCD
北大核心
2014年第2期353-359,共7页
China Earthquake Engineering Journal
基金
国家自然科学基金(41374028
41274083)
地震行业科研专项(2013008009)
关键词
青藏高原东缘
地震
GRACE
滤波
重力变化
the eastern margin of the Tibetan Plateau
earthquake
（
RACE
filtering
gravity change
