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| Semiannual velocity variations around the 2008 Mw 7.9 Wenchuan Earthquake fault zone revealed by ambient noise and ACROSS active source data |
| Haichao Chen1,2, Hongkui Ge2, Fenglin Niu2,3 |
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
3 Department of Earth Science, Rice University, 6100 Main Street, Houston, TX 77005, USA |
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Abstract We continuously monitor the long-term seismic velocity variation of one of the major ruptured faults of the devastating 2008 Mw 7.9 Wenchuan earthquake in China from July 2009 to January 2012, jointly using accurately controlled routinely operated signal system active source and seismic noise-based monitoring technique. Our measurements show that the temporal velocity change is not homogeneous and highly localized in the damaged fault zone and the adjacent areas. Velocity variations from the active and passive methods are quite consistent, which both are characterized by ±0.2 % seasonal variation, with peak and trough at winter and summer, respectively. The periodic velocity variation within fault zone exhibits remarkably positive correlation with barometric pressure with stress sensitivity in the order of 10-6 Pa-1, suggesting that the plausible mechanism might be the crack density variation of the shallow subsurface medium of the damaged fault zone in response to the cyclic barometric pressure loading.
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Received: 30 April 2014
Published: 26 June 2014
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| Fund:the National Natural Science Foundation of China with Grant No. 41174040 and the Wenchuan earthquake Fault Scientific Drilling project |
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Corresponding Authors:
Haichao Chen
E-mail: seismichc@163.com
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