论文标题
使用物理信息神经网络求解声学VTI波方程
Solving the acoustic VTI wave equation using physics-informed neural networks
论文作者
论文摘要
与各向异性声波方程相对应的频域波场溶液可用于描述地球的各向异性性质。为了求解频域的方程,我们通常需要倒置阻抗矩阵。随着模型大小的增加,这会导致计算成本急剧增加。对于各向异性媒体来说,这甚至是一个更大的挑战,在这种媒体上,阻抗矩阵更为复杂。为了解决这个问题,我们使用物理知识神经网络(PINN)的新兴范例来获取具有垂直对称性轴(VTI)的横向各向同性(TI)介质的声波方程的波场解。 Pinns利用自动分化的概念来计算其部分导数。因此,我们将波方程用作损耗函数来训练神经网络,以提供功能解决方案,以形成声学VTI波方程。我们没有直接预测压力波场,而是求解散射的压力波场,以避免处理点源奇点。我们将空间坐标用作网络的输入数据,该数据输出了散射波场和辅助函数的真实和虚构部分。在训练深神网络(NN)之后,我们可以使用训练有素的NN立即评估空间的任何位置。我们在简单的异常模型和分层模型上演示了这些功能。对修改后的3D推翻模型和具有不规则地形的模型的其他测试也显示了所提出的方法的有效性。
Frequency-domain wavefield solutions corresponding to the anisotropic acoustic wave equations can be used to describe the anisotropic nature of the earth. To solve a frequency-domain wave equation, we often need to invert the impedance matrix. This results in a dramatic increase in computational cost as the model size increases. It is even a bigger challenge for anisotropic media, where the impedance matrix is far more complex. To address this issue, we use the emerging paradigm of physics-informed neural networks (PINNs) to obtain wavefield solutions for an acoustic wave equation for transversely isotropic (TI) media with a vertical axis of symmetry (VTI). PINNs utilize the concept of automatic differentiation to calculate its partial derivatives. Thus, we use the wave equation as a loss function to train a neural network to provide functional solutions to form of the acoustic VTI wave equation. Instead of predicting the pressure wavefields directly, we solve for the scattered pressure wavefields to avoid dealing with the point source singularity. We use the spatial coordinates as input data to the network, which outputs the real and imaginary parts of the scattered wavefields and auxiliary function. After training a deep neural network (NN), we can evaluate the wavefield at any point in space instantly using this trained NN. We demonstrate these features on a simple anomaly model and a layered model. Additional tests on a modified 3D Overthrust model and a model with irregular topography also show the effectiveness of the proposed method.