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| Characteristics of subsurface density variations before the 4.20 Lushan MS7.0 earthquake in the Longmenshan area: inversion results |
| Songbai Xuan1 2, Chongyang Shen2, Hui Li2, Hongtao Hao2 |
1 School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China
2 Institute of Seismology, China Earthquake Administration, Wuhan 430071, China |
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Abstract The 4.20 Lushan MS7.0 earthquake occurred on the southwest segment of the Longmenshan fault on 20 April 2013. Some meaningful information on the preparation and occurrence of this earthquake was found based on the dynamic variation of gravity (DVG). To examine the great progress of the Lushan earthquake, we obtained the density variation (DENV) derived from the DVG using the compact gravity inversion method in this article. The inversion results reveal three main findings: (1) the DENV in the crust in the Jinshajiang fault area changed from positive in 2010–2011 to negative in 2011–2012. (2) The DENV in the Xianshuihe fault area decreased continuously from 2010 to 2012. (3) The DENV of the uppermost mantle of South China decreased in 2010–2011 and increased in 2011–2012. We propose that the flow/expansion of the middle-lower crust beneath the Bayan Har block and Moho subsidence on the southwest margin of the Chuan-Dian block may have been the major causes of the Lushan earthquake.
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Received: 24 November 2015
Published: 12 January 2015
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| Fund:National Natural Science Foundation of China (41304060), the National Key Basic Research Program of China (973 Program, 2013CB733305) |
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Corresponding Authors:
Songbai Xuan
E-mail: song_bai_whu@163.com
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