基于逐元和轴对称谱元的混合方法及远震波场模拟

Hybrid method based on element-by-element and axisymmetric spectral element method for teleseismic wavefield simulation

远震波形成像是研究地球内部结构和动力学过程的重要手段.然而,由于巨大的计算需求,当前在全球尺度(包含震源-台站)数值模拟高频(频率到2 Hz)地震波传播并不现实.谱元法是一种高有效性的数值模拟算法,具有高精度和网格剖分灵活的优点,并且已经成功应用于弹性波方程求解中.但缺点是求解远震问题时计算量和存储量较大.为了克服上述难题,本文发展了一种基于逐元并行谱元法与轴对称谱元法相结合的混合方法:即在全球尺度层状模型下使用具有快速计算效率的轴对称谱元法模拟远震背景波场,而在研究区域内使用逐元并行谱元法精确计算非均匀介质中远震波场传播.该方法减少了非均匀介质中远震波场模拟的计算量与存储量,并保持了逐元并行谱元法高精度、低存储量、易并行的优点.数值实验验证了该混合方法的可行性和精确性,并有望进一步应用于实际地震数据远震波形成像研究中.

Teleseismic full-waveform tomography is an important tool for studying the internal structure and dynamical processes of the earth.However,the current numerical simulation of high frequency(frequency up to 2 Hz)seismic waves at the global scale is not practical due to its huge amount of calculation.The spectral element method(SEM)is a highly efficient numerical algorithm with high accuracy and flexible grid dissection and has been successfully applied to the solution of elastic wave equation.However,it has large computational and storage requirements for teleseismic wavefield modeling.To overcome these difficulties,we develop a hybrid method based on the element-by-element parallel spectral-element method(EBE-SEM)and the axisymmetric spectral element method(AxiSEM)to simulate the teleseismic background wavefield.For layered media,AxiSEM is used to compute the long-distance propagation of teleseismic waves,and EBE-SEM is applied to accurately simulate the wavefield in heterogeneous medium.This method keeps the advantages of high precision,low storage capacity,and high parallelism,while its computational time and memory of teleseismic wavefield simulation can be reduced significantly.Numerical experiments verify the feasibility and accuracy of our hybrid algorithm,and it can be further applied to teleseismic waveform tomography using real seismic data.