The distribution of noise source both in space and time and its influence on Noise Cross-correlation Functions

被引：0
|
作者：
Zhao L. [1 ,3 ]
Wang W. [1 ,2 ]
Wang F. [1 ,4 ]
Li N. [1 ,3 ]
机构：
[1] Institute of Geophysics, China Earthquake Administration, Beijing
[2] Key Laboratory of Earthquake Source Physics, Institute of Geophysics, China Earthquake Administration, Beijing
[3] Yunnan Earthquake Agency, Kunming
[4] State Key Laboratory of Geodesy and Earth's Dynamics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan
来源：
Wang, Weitao (wangwt@cea-igp.ac.cn); Wang, Weitao (wangwt@cea-igp.ac.cn) | 1600年 / Science Press卷 / 64期
关键词：
Ambient noise source distribution; Noise Cross-correlation Function; Normalized background energy flux;
D O I：
10.6038/cjg2021O0054
中图分类号：
学科分类号：
摘要：
The reconstruction of Green's function by long time ambient noise cross-correlation has been widely used in seismology. The distribution of noise sources doesn't meet the theoretical assumption that they are uniformly distributed in both space and time, which can affect signals retrieved from Noise Cross-correlation Functions (NCFs). To further address this issue, using the continuous vertical records of 322 broadband seismic stations which are evenly distributed in a square in southern part of ChinArray Phase II, we calculate the NCFs from September 2013 to June 2016. The seasonal variation and azimuthal anisotropy are analyzed using the normalized background energy flux (NBEF) method for the period bands 4~8 s, 8~12 s and 12~20 s, respectively. Clear seasonal variation and directional anisotropy are observed for all periods and the characteristics of different periods are variable. Overall, the ambient noise energy is stronger in winter and weaker in summer. This is consistent with global oceanic activities which are stronger in winter and become weaker in summer in each local hemisphere. Moreover, strong precursors are observed in NCFs for period 10~20 s, showing clear azimuthal dependency in the NCFs having similar inter-station distance and different azimuths. The precursors are stronger in winter and weaker in summer. Analyzing their seasonality and arrival time suggests that they should be caused by one local noise source located in the northern Atlantic Ocean. The precursors may generate strong signals just before the Rayleigh waves and distort the dispersion measurement. This study suggests that the characteristics of the noise source, such as uneven distribution and seasonal variation, will affect the detail of the signals in NCFs and further the convergence of the Green's function. This phenomenon should be to be considered in noise cross-correlation studies. © 2021, Science Press. All right reserved.
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页码：4327 / 4340
页数：13
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