GRACE detection of the medium- to far-field coseismic gravity changes caused by the 2004 MW9.3 Sumatra-Andaman earthquake
Jin Li1, 2, 3, Wenbin Shen1, 3, 4
1 Department of Geophysics, School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China 2 Key Laboratory of Geodynamic Geodesy of Chinese Academy, Wuhan 430077, China 3 Key Laboratory of Geospace Environment and Geodesy (Ministry of Education), Wuhan University, Wuhan 430079, China 4 State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan 430079, China
GRACE detection of the medium- to far-field coseismic gravity changes caused by the 2004 MW9.3 Sumatra-Andaman earthquake
Jin Li1, 2, 3, Wenbin Shen1, 3, 4
1 Department of Geophysics, School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China 2 Key Laboratory of Geodynamic Geodesy of Chinese Academy, Wuhan 430077, China 3 Key Laboratory of Geospace Environment and Geodesy (Ministry of Education), Wuhan University, Wuhan 430079, China 4 State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan 430079, China
摘要Large earthquakes cause observable changes in the Earth’s gravity field, which have been detected by the Gravity Recovery and Climate Experiment (GRACE). Since most previous studies focus on the detection of near-field gravity effects, this study provides the results from the medium- to far-field gravity changes caused by the 2004 Sumatra-Andaman earthquake that are recorded within GRACE monthly solutions. Utilizing a spherical-earth dislocation model we documented that large-scale signals predominate in the global field of the coseismic gravity changes caused by the earthquake. After removing the near-field effects, the coseismic gravity changes show a negative anomaly feature with an average magnitude of -0.18×10-8 m·s-2 in the region ranging ～40° from the epicenter, which is considered as the “medium field” in this study. From the GRACE data released by Center for Space Research from August 2002 to December 2008, we retrieved the large-scale gravity changes smoothed with 3 000 km Gaussian filter. The results show that the coseismic gravity changes detected by GRACE in the medium field have an average of (-0.20±0.06)×10-8 m·s-2, which agrees with the model prediction. The detection confirms that GRACE is sensitive to large-scale medium-field coseismic gravitational effects of mega earthquakes, and also validates the spherical-earth dislocation model in the medium field from the perspective of satellite gravimetry.
Abstract：Large earthquakes cause observable changes in the Earth’s gravity field, which have been detected by the Gravity Recovery and Climate Experiment (GRACE). Since most previous studies focus on the detection of near-field gravity effects, this study provides the results from the medium- to far-field gravity changes caused by the 2004 Sumatra-Andaman earthquake that are recorded within GRACE monthly solutions. Utilizing a spherical-earth dislocation model we documented that large-scale signals predominate in the global field of the coseismic gravity changes caused by the earthquake. After removing the near-field effects, the coseismic gravity changes show a negative anomaly feature with an average magnitude of -0.18×10-8 m·s-2 in the region ranging ～40° from the epicenter, which is considered as the “medium field” in this study. From the GRACE data released by Center for Space Research from August 2002 to December 2008, we retrieved the large-scale gravity changes smoothed with 3 000 km Gaussian filter. The results show that the coseismic gravity changes detected by GRACE in the medium field have an average of (-0.20±0.06)×10-8 m·s-2, which agrees with the model prediction. The detection confirms that GRACE is sensitive to large-scale medium-field coseismic gravitational effects of mega earthquakes, and also validates the spherical-earth dislocation model in the medium field from the perspective of satellite gravimetry.
基金资助:the Natural Science Foundation of China (grant Nos. 40974015, 41128003, 41174011 and 41021061), the Open Fund of Key Laboratory of Geodynamic Geodesy of Chinese Academy (No. 09-18), and the Open Fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, China (No. 07-12)
通讯作者:
Wenbin Shen
E-mail: wbshen@sgg.whu.edu.cn
引用本文:
Jin Li, Wenbin Shen. GRACE detection of the medium- to far-field coseismic gravity changes caused by the 2004 MW9.3 Sumatra-Andaman earthquake[J]. 《地震学报》英文版, 2012, 25(3): 235-240.
Jin Li, Wenbin Shen. GRACE detection of the medium- to far-field coseismic gravity changes caused by the 2004 MW9.3 Sumatra-Andaman earthquake. Earthquake Science, 2012, 25(3): 235-240.
