用神经场测试时学习提升地质反演精度,减少观测敏感性带来的伪影。
Towards Understanding the Benefits of Neural Network Parameterizations in Geophysical Inversions: A Study With Neural Fields
- 通过测试时学习动态调整网络权重,无需预训练数据集。
- 在地震层析与直流电阻率反演中,显著改善断层面角和目标边界恢复效果。
- 发现神经网络存在隐式偏差,可帮助提升反演模型质量,适合地质建模研究者。
本文采用神经场(Neural Fields)以坐标映射至对应物理属性值的方式,在测试时学习框架下进行地质反演。该方法在反演过程中动态学习网络权重,区别于传统需依赖训练数据集的模型。针对合成地震层析与直流电阻率反演案例,结果表明:测试时学习能有效消除由观测灵敏度与物理模型引起的不必要伪影。通过雅可比矩阵的奇异值分解(SVD分析),发现左奇异向量模式与计算机视觉中监督生成模型相似,揭示神经网络结构本身存在一种隐式偏差。这种偏差在监督学习与测试时学习中均具价值,有助于提升地质反演中地下物理属性模型的重建质量。
原文摘要 · Abstract (English)
In this work, we employ neural fields, which use neural networks to map a coordinate to the corresponding physical property value at that coordinate, in a test-time learning manner. For a test-time learning method, the weights are learned during the inversion, as compared to traditional approaches which require a network to be trained using a training dataset. Results for synthetic examples in seismic tomography and direct current resistivity inversions are shown first. We then perform a singular value decomposition analysis on the Jacobian of the weights of the neural network (SVD analysis) for both cases to explore the effects of neural networks on the recovered model. The results show that the test-time learning approach can eliminate unwanted artifacts in the recovered subsurface physical property model caused by the sensitivity of the survey and physics. Therefore, NFs-Inv improves the inversion results compared to the conventional inversion in some cases such as the recovery of the dip angle or the prediction of the boundaries of the main target. In the SVD analysis, we observe similar patterns in the left-singular vectors as were observed in some diffusion models, trained in a supervised manner, for generative tasks in computer vision. This observation provides evidence that there is an implicit bias, which is inherent in neural network structures, that is useful in supervised learning and test-time learning models. This implicit bias has the potential to be useful for recovering models in geophysical inversions.
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