用机器学习改进地震源反演,更准估算不确定性。
Full-waveform earthquake source inversion using simulation-based inference
- 用神经密度估计构建数据误差模型,替代传统假设。
- 真实噪声下,传统方法低估不确定性达3倍,新方法更准确。
- 只需少量模拟即可完成反演,适合实际地震数据应用。
本文提出一种基于仿真推断(SBI)的全波形地震源反演新框架。传统概率方法常依赖对数据误差的简化假设,导致不确定性量化不准。SBI通过机器学习模型(神经密度估计器)构建数据误差的实证概率模型,嵌入贝叶斯推断框架。我们将其应用于点源矩张量反演及联合矩张量与震时位置反演。通过一系列合成案例验证,发现真实地震噪声下,标准高斯似然假设会导致后验分布过于自信,矩张量分量不确定性被低估最高达3倍;而SBI生成的后验分布校准良好,结果与真实源参数一致,并将所需模拟次数减少一个数量级。最后,我们在北大西洋两次中等震级地震上应用该方法,利用近期UPFLOW海底地震仪阵列及亚速尔群岛陆地台站记录的波形数据,对比了全矩张量与源时位置后验分布。结果显示,SBI可直接用于真实地震源,高效生成高质量后验分布,显著优于高斯似然方法。
原文摘要 · Abstract (English)
This paper presents a novel framework for full-waveform seismic source inversion using simulation-based inference (SBI). Traditional probabilistic approaches often rely on simplifying assumptions about data errors, which we show can lead to inaccurate uncertainty quantification. SBI addresses this limitation by building an empirical probabilistic model of the data errors using machine learning models, known as neural density estimators, which can then be integrated into the Bayesian inference framework. We apply the SBI framework to point-source moment tensor inversions as well as joint moment tensor and time-location inversions. We construct a range of synthetic examples to explore the quality of the SBI solutions, as well as to compare the SBI results with standard Gaussian likelihood-based Bayesian inversions. We then demonstrate that under real seismic noise, common Gaussian likelihood assumptions for treating full-waveform data yield overconfident posterior distributions that underestimate the moment tensor component uncertainties by up to a factor of 3. We contrast this with SBI, which produces well-calibrated posteriors that generally agree with the true seismic source parameters, and offers an order-of-magnitude reduction in the number of simulations required to perform inference compared to standard Monte Carlo techniques. Finally, we apply our methodology to a pair of moderate magnitude earthquakes in the North Atlantic. We utilise seismic waveforms recorded by the recent UPFLOW ocean bottom seismometer array as well as by regional land stations in the Azores, comparing full moment tensor and source-time location posteriors between SBI and a Gaussian likelihood approach. We find that our adaptation of SBI can be directly applied to real earthquake sources to efficiently produce high quality posterior distributions that significantly improve upon Gaussian likelihood approaches.
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