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Rapid finite-frequency microseismic noise source inversion at regional to global scales
Geophysical Journal International ( IF 2.8 ) Pub Date : 2021-05-26 , DOI: 10.1093/gji/ggab210
Jonas K H Igel 1 , Laura A Ermert 2 , Andreas Fichtner 1
Affiliation  

SUMMARY Ambient noise cross-correlations can be used as self-consistent observables, opening novel possibilities for investigating ambient noise sources. To optimize the forward-modelling of global ambient noise cross-correlations for any given distribution of noise sources in the microseismic frequency range up to 0.2 Hz, we implement (i) pre-computed wavefields and (ii) spatially variable grids. This enables rapid inversions for microseismic noise sources based on finite-frequency source sensitivity kernels. We use this advancement to perform regional and global gradient-based iterative inversions of the logarithmic energy ratio in the causal and acausal branches of microseismic noise cross-correlations. Synthetic inversions show promising results, with good recovery of the main dominant noise sources of the target model. Data inversions for several consecutive days at the beginning of October 2019 demonstrate the capability of inverting for the spatio-temporal variations of the sources of secondary microseisms in the ocean. This paves the way for daily ambient noise source inversions which could help improve full-waveform ambient noise tomography and subsurface monitoring methods.

中文翻译:

区域到全球尺度的快速有限频率微震噪声源反演

总结 环境噪声互相关可以用作自洽的可观察量,为研究环境噪声源开辟了新的可能性。为了优化在高达 0.2 Hz 的微震频率范围内的任何给定噪声源分布的全局环境噪声互相关的正向建模,我们实现了 (i) 预先计算的波场和 (ii) 空间可变网格。这使得基于有限频率源灵敏度内核的微震噪声源能够快速反演。我们利用这一进步对微震噪声互相关的因果分支和非因果分支中的对数能量比进行基于区域和全局梯度的迭代反演。合成反演显示出可喜的结果,目标模型的主要主要噪声源得到了良好的恢复。2019年10月上旬连续数日数据反演证明具有反演海洋次生微震源时空变化的能力。这为日常环境噪声源反演铺平了道路,有助于改进全波形环境噪声断层扫描和地下监测方法。
更新日期:2021-05-26
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