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Journal: |
Chinese Journal of Geophysics 2010 No.8
clicks:867 |
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Title:
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Author:
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WANG Wu-Xing, SHI Yao-Lin, GU Guo-Hua, ZHANG Jing, CHEN Shi |
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Adress: |
Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China |
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Abstract:
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Time variable changes in gravity field on and around Chinese Mainland before and after the WenchuanMs8.0 earthquake are obtained from the GRACE satellite gravity data. Time series of gravity changes at typical locations are also obtained. At the same time, time series of displacements at GPS fiducial stations of WUSH, LHAS, KUNM and LUZH are obtained in the regional reference frame. Results from GRACE indicate that after the Sumatra earthquake along the Himalaya arc the satellite gravity showed rapid decrease, particularly during the period of 2006 to 2008 the decrease in gravity was significant; while along the northwestern boundary of the Xiyu block there was also significant post seismic decrease in gravity. And along the northern and eastern boundaries of the Tibetan plateau there appeared an arc along the tectonic boundary with significant gravity increase in 2007. But in 2008 there was also significant increase in gravity in the southern and middle segments of the North-South seismic belt. This trend in gravity variations after the Sumatra earthquake changed only after the Wenchuan earthquake. Displacements at 4 GPS stations recorded coseismic signals of the great Sumatra earthquake, and then the horizontal displacement vectors at WUSH, LHAS and KUNM showed significant changes in their general trend until the occurrence of the Wenchuan Ms8.0 earthquake. The changes in the density of the ground mass in the Tibetan plateau and the surrounding areas as revealed by the GRACE satellites have provided new observation approach and data for the explanation of the dynamic mechanism of the Wenchuan earthquake. A preliminary explanation and discussion on the characteristics of the time variable changes in the gravity field observed by GRACE and the dynamic mechanism of the Wenchuan earthquake are presented in this paper by combining the features of regional tectonic movements and displacements of GPS observations.
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