基于改进的EAL边界条件的地震波场数值模拟  

Numerical simulation of seismic wavefield based on modified EAL boundary condition

作　　者：张平民 姚刚 ZHANG PingMin;YAO Gang(National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China;Unconventional Petroleum Research Institute,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国石油大学(北京)油气资源与工程全国重点实验室,北京102249 [2]中国石油大学(北京)非常规油气科学与技术研究院,北京102249

出　　处：《地球物理学报》2024年第1期261-276,共16页Chinese Journal of Geophysics

基　　金：中石油集团前瞻性基础性项目“物探岩石物理与前沿储备技术研究”(2022DQ0604-02);国家自然科学基金(41974142,42074129,U23B20159)联合资助。

摘　　要：在地震波场数值模拟过程中,人工截断边界会产生数值反射而影响地震波场模拟的精度.应用PML(Perfectly Matched Layer)吸收边界条件是消除人工边界反射的有效手段,但是该方法计算量较大,实现较为复杂,且在某些各向异性介质中不稳定.EAL(Effective Absorbing Layer)边界条件是通过简化PML吸收边界条件的阻尼项推导出来的一种吸收边界条件.EAL的吸收项作用于波动方程的时间导数项,故EAL边界条件具有计算量小且利于并行实现的特点.应用EAL边界条件能够在保证全波形反演和逆时偏移精度的前提下,提升计算效率并降低内存消耗.本文对EAL边界条件进行两点改进:(1)引入减速阻尼项;(2)采用高斯型空间加权函数构建阻尼项.正演模拟结果表明,改进的EAL边界条件在不增加计算量和内存消耗的同时,有效提升了EAL边界条件的吸收效果且适用于复杂介质和各向异性介质.特别地,相比于PML吸收边界条件,EAL边界条件在各向异性模型中表现出良好的稳定性.In the process of seismic wavefield simulation,artificial truncated boundaries generate spurious reflection,reducing the accuracy of seismic wavefield simulation.The Perfectly Matched Layer(PML) absorbing boundary condition is an effective means of eliminating spurious boundary reflections,but this method is computationally expensive and difficult to implement.In addition,it is instability in some anisotropic media.Effective Absorbing Layer(EAL) boundary condition is an absorbing boundary condition derived by simplifying the damping terms of PML absorbing boundary conditions.The absorption term of EAL is applied only to the time derivative terms of the wave equation.Therefore,the EAL boundary condition costs smaller computation than PML and facilitates parallel implementation.The application of the EAL boundary condition can improve computational efficiency and reduce memory consumption while ensuring the accuracy of full-waveform inversion and reverse-time migration.In this paper,we improve the EAL boundary condition by introducing the velocity damping term and constructing the damping term with the Gaussian spatial weighting function.The forward modeling results show that the improved EAL boundary condition can effectively boost the absorption effect without increasing the computational burden and memory consumption.It is suitable for complex and anisotropic media.In particular,the EAL boundary condition has higher stability in anisotropic models than the PML absorbing boundary condition.

关 键 词：吸收边界条件 时空域有限差分 波动方程 各向异性介质 

分 类 号：P631[天文地球—地质矿产勘探]