Source-structure trade-offs in ambient noise correlations
Source-structure trade-offs in ambient noise correlations
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DOI：
10.1093/gji/ggv182
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发表时间：
2015-07-01
影响因子：
2.8
通讯作者：
Fichtner, Andreas
中科院分区：
文献类型：
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作者：
Fichtner, Andreas
我们分析了站间噪声相关性中地球结构和噪声源之间的权衡的物理和几何。我们的方法是基于非对角Hessian元素的计算，描述在何种程度上，噪声源的变化可以补偿地球结构的变化，而不改变超出测量不确定性的失配。尽管所有环境噪声逆问题在其接收器配置和数据方面都是特殊的，但可以做出关于源-结构权衡的一些一般性陈述：（i）虽然通过巧妙的测量设计可以在一定程度上减少源-结构权衡，但通常无法避免固有的权衡。当噪声源分布未知时，这些固有的权衡可能导致结构异质性的错位。(ii)当衰减较弱时，环境噪声相关性中的源-结构权衡是一种全球现象，这意味着没有噪声源扰动不与某些地球结构进行权衡，反之亦然。(iii)最重要的源结构的权衡发生在两个椭圆形的区域连接一个潜在的噪声源扰动的每个接收器。(iv)远离这些椭圆形区域，只有小尺度的结构可以与噪声源的变化进行权衡。(v)虽然源-结构权衡主要随着衰减的增加而衰减，但当噪声源扰动位于接收器-接收器线附近时，它们几乎不受衰减的影响。这项工作的目的是促进联合源结构反演的环境噪声相关性的发展，特别是了解源结构的权衡可能会减少的程度。它还建立了未来的分辨率分析，适当量化噪声源和地球结构之间的权衡的基础。
We analyse the physics and geometry of trade-offs between Earth structure and noise sources in interstation noise correlations. Our approach is based on the computation of off-diagonal Hessian elements that describe the extent to which variations in noise sources can compensate for variations in Earth structure without changing the misfit beyond the measurement uncertainty. Despite the fact that all ambient noise inverse problems are special in terms of their receiver configuration and data, some general statements concerning source-structure trade-offs can be made: (i) While source-structure trade-offs may be reduced to some extent by clever measurement design, there are inherent trade-offs that can generally not be avoided. These inherent trade-offs may lead to a mispositioning of structural heterogeneities when the noise source distribution is unknown. (ii) When attenuation is weak, source-structure trade-offs in ambient noise correlations are a global phenomenon, meaning that there is no noise source perturbation that does not trade-off with some Earth structure, and vice versa. (iii) The most significant source-structure trade-offs occur within two elliptically shaped regions connecting a potential noise source perturbation to each one of the receivers. (iv) Far from these elliptical regions, only small-scale structure can trade off against changes in the noise source. (v) While source-structure trade-offs mostly decay with increasing attenuation, they are nearly unaffected by attenuation when the noise source perturbation is located near the receiver-receiver line. This work is intended to contribute to the development of joint source-structure inversions of ambient noise correlations, and in particular to an understanding of the extent to which source-structure trade-offs may be reduced. It furthermore establishes the foundation of future resolution analyses that properly quantify trade-offs between noise sources and Earth structure.