Graph-Space Optimal Transport Concept for Time-Domain Full-Waveform Inversion of Ocean-Bottom Seismometer Data: Nankai Trough Velocity Structure Reconstructed From a 1D Model
Graph-Space Optimal Transport Concept for Time-Domain Full-Waveform Inversion of Ocean-Bottom Seismometer Data: Nankai Trough Velocity Structure Reconstructed From a 1D Model
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DOI：
10.1029/2020jb021504
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发表时间：
2021-05-01
影响因子：
3.9
通讯作者：
Metivier, Ludovic
中科院分区：
文献类型：
--
作者：
Gorszczyk, Andrzej;Brossier, Romain;Metivier, Ludovic
利用广角海底地震仪（OBS）数据的全波形反演（FWI）来详细重建深部结构仍然是一项具有挑战性的非常规工作。长偏移距波形的复杂性增加了逆问题的非线性，而OBS部署的稀疏性导致模型重构约束较差。因此，对于这样的FWI设置，难以导出满足循环跳过标准的初始模型。为了解决这个问题，我们研究了图空间最优传输（GSOT）技术，该技术可以潜在地克服初始FWI阶段的循环跳跃问题。GSOT成本函数的关键特征是相对于两个地震图中的模式的凸性，这允许在时间上移动超过一半的子波的到达的正确匹配。这反过来将允许FWI处理起始模型的大运动学误差。我们测试这一假设，应用时域声波FWI的合成和现场数据从俯冲带环境。我们表明，尽管地质结构的复杂性，GSOT失配函数是能够引导FWI对精确的速度模型重建和数据拟合从一个简单的一维模型。GSOT失配函数的改进的凸性允许FWI收敛，即使当观测信号和合成信号之间的失配达到几个周期时。这种能力减少了对初始模型的运动精度的约束，并使从OBS数据的FWI更可行。
Detailed reconstruction of deep structures with full-waveform inversion (FWI) of wide-angle ocean-bottom seismometer (OBS) data remains challenging and unconventional. The complexity of the long-offset waveforms increases the nonlinearity of the inverse problem, while the sparsity of the OBS deployments leads to a poorly constrained model reconstruction. Consequently, for such a FWI setting it is difficult to derive an initial model that satisfies the cycle-skipping criterion. Searching for a remedy to this issue, we investigate the graph-space optimal transport (GSOT) technique, which can potentially overcome the cycle-skipping problem at the initial FWI stage. The key feature of the GSOT cost function is the convexity with respect to the patterns in the two seismograms, which allows for correct matching of the arrivals shifted in time for more than half of the wavelet. This in turn shall allow FWI to handle the large kinematic errors of the starting model. We test this hypothesis by applying the time-domain acoustic FWI to the synthetic and field data from the subduction zone environment. We show that despite the complexity of the geological structure, the GSOT misfit function is able to guide the FWI toward the precise velocity model reconstruction and data fitting starting from a simple 1D model. The improved convexity of the GSOT misfit function allows FWI to converge even when mismatches between the observed and synthetic signals reach a few cycles. This ability reduces the constraint on the kinematic accuracy of the initial model and makes the FWI from the OBS data more feasible.