A numeric evaluation of attenuation from ambient noise correlation functions
A numeric evaluation of attenuation from ambient noise correlation functions
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DOI：
10.1002/2012jb009513
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
J. Lawrence;M. Denolle;K. Seats;G. Prieto
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文献类型：
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作者：
J. Lawrence;M. Denolle;K. Seats;G. Prieto
地震台站间计算的环境噪声相关函数（NCF）在适当条件下包含准确的走时信息。然而，由于噪声源强度和分布、地震固有衰减、散射以及聚焦和散焦等弹性路径效应，NCF振幅备受争议。我们通过各种数值模拟证明了用相干法计算均匀色散介质的非相干系数保持了精确的几何扩展和衰减衰减。研究表明，对于广泛的噪声源分布，噪声相关函数的相干性与贝塞尔函数的衰减系数呈指数衰减相匹配。获得这些结果所需的条件包括在足够长的时间间隔内进行平均，均匀分布的地震网，以及远场噪声源的良好分布。我们还表明，估计的衰减系数对应于站间，而不是噪声源到接收机的结构。
The ambient noise correlation function (NCF) calculated between seismic stations contains, under appropriate conditions, accurate travel time information. However, NCF amplitudes are highly debated due to noise source intensity and distribution, seismic intrinsic attenuation, scattering, and elastic path effects such as focusing and defocusing. We prove with various numerical simulations that the NCFs calculated for a uniformly dispersive medium using the coherency method preserve accurate geometrical spreading and attenuation decay. We show that for a wide range of noise source distributions, the coherency of the noise correlation functions matches a Bessel function decaying exponentially with a specific attenuation coefficient. Conditions needed to obtain these results include averaging over long enough time intervals, a uniformly distributed seismic network, and a good distribution of far‐field noise sources. We also show that the estimated attenuation coefficient corresponds to the interstation and not the noise‐source‐to‐receiver structure.