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Active source monitoring at the Wenchuan fault zone: coseismic velocity change associated with aftershock event and its implication |
Wei Yang1, Hongkui Ge2, Baoshan Wang1, Jiupeng Hu1, Songyong Yuan1, Sen Qiao1 |
1 Key Laboratory of Seismic Observation and Geophysical Imaging, Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
2 Unconventional Natural Gas Institute, China University of Petroleum, Beijing 102249, China |
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Abstract With the improvement of seismic observation system, more and more observations indicate that earthquakes may cause seismic velocity change. However, the amplitude and spatial distribution of the velocity variation remains a controversial issue. Recent active source monitoring carried out adjacent to Wenchuan Fault Scientific Drilling (WFSD) revealed unambiguous coseismic velocity change associated with a local Ms5.5 earthquake. Here, we carry out forward modeling using two-dimensional spectral element method to further investigate the amplitude and spatial distribution of observed velocity change. The model is well constrained by results from seismic reflection and WFSD coring. Our model strongly suggests that the observed coseismic velocity change is localized within the fault zone with width of ~120 m rather than dynamic strong ground shaking. And a velocity decrease of ~2.0 % within the fault zone is required to fit the observed travel time delay distribution, which coincides with rock mechanical experiment and theoretical modeling.
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Received: 19 September 2014
Published: 29 November 2014
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Fund:China Natural Scientific and Technological Support Projects (Wenchuan Fault Scientific Drilling) and National Natural Scientific Foundation of China (Grant No. 41204047) |
Corresponding Authors:
Wei Yang
E-mail: weiyang05@163.com
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