Crustal Velocity Changes Associated with the Wenchuan M8.0 Earthquake by Auto-Correlation Function Analysis of Seismic Ambient Noise
详细信息
- 责任者：Zhao Panpan (State Key Laboratory of Earthquake Dynamics ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Chen Jiuhui
- 刊名：Chinese Journal of Geophysics
- 出版年：2012
- 卷期：55(1)
- 关键词：汶川地震2008 ; Wenchuan earthquake 2008 ; 速度分析 ; velocity analysis ; 四川 ; Sichuan Province
- 页码：p.137-145
- 图表：6 illus., 38 refs.
- 分类号：0500
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
A temporal seismic array consisted of 297 broadband seismographs was deployed in Western Sichuan(100°～105°E,26°～32°N) in 2006,and the observation covered the great 2008 Wenchuan earthquake.We used the continuous three-component ambient noise data from January,2007 to October,2008,recorded at the 137 stations north of 29°N,to study the crust seismic velocity changes before and after the earthquake.For every single station,three autocorrelation functions(ACF) and three cross correlation functions(CCF) are calculated and stacked in 10 days for three components of noise data respectively.Then we estimated the relative velocity changes by measuring travel time shifts between the 50-day-moving-average stacks and the reference empirical correlation functions.We obtained the characteristic of spatial distribution of relative velocity changes caused by Wenchuan earthquake.Our results indicate that ACF analysis can get similar coseismic velocity changes pattern with the CCF method,and the distribution of coseismic velocity changes is closely correlated with the volumetric strain changes during the Wenchuan earthquake.We also found an area of velocity increase in the region where the Longmenshan Fault zone adjoins the Xianshuihe Fault zone.This area is consistent with the faults that the Coulomb stress increased by the occurrence of the Wenchuan earthquake as predicted by the source mechanism and surface deformation.We also found that the crustal velocity increase lasted for about 2 months and then decreased with ubiquitous stress release in the studying region.