Semiannual velocity variations around the 2008 M_w 7.9 Wenchuan Earthquake fault zone revealed by ambient noise and ACROSS active source data  

作　　者：Haichao Chen Hongkui Ge Fenglin Niu 

机构地区：[1]Key Laboratory of Seismic Observation and Geophysical Imaging,Institute of Geophysics,China Earthquake Administration [2]Unconventional Natural Gas Institute,China University of Petroleum [3]Department of Earth Science,Rice University

出　　处：《Earthquake Science》2014年第5期529-540,共12页地震学报（英文版）

基　　金：supported by the National Natural Science Foundation of China with Grant No.41174040;the Wenchuan earthquake Fault Scientific Drilling project

摘　　要：We continuously monitor the long-term seismic velocity variation of one of the major ruptured faults of the devastating 2008 Mw7.9 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 10-6Pa-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.We continuously monitor the long-term seismic velocity variation of one of the major ruptured faults of the devastating 2008 Mw7.9 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 10-6Pa-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.

关 键 词：Velocity variation - 2008 WenchuanEarthquake ACROSS active source Ambient noise 

分 类 号：P315[天文地球—地震学]