地震声波数值模拟中人工边界条件的差别与组合

Difference and Combination of Artificial Boundary Conditions in Seismic Acoustic Numerical Simulation

地震数值模拟中选取的有限计算区域产生的边界反射会干扰正常波场模拟结果,因此引入人工边界条件来降低边界反射的影响。本文针对PML(perfectly matched layer)边界条件的解耦与非解耦差分形式,应用不同空间差分阶数进行地震波场数值模拟。空间差分阶数提高后,非解耦PML差分形式在计算效率和实现方式上均更具优势。针对CE(Clayton-Engquist)边界条件受入射波入射角度限制、边界处精度低吸收效果不好等问题,将2阶CE边界条件和PML边界条件组合成一种新的组合边界条件,在保证吸收效果的同时减少衰减带厚度,从而达到提高计算效率的目的。数值模拟结果验证了算法的有效性。

In seismic numerical simulation,the boundary reflection generated by the finite calculation area will interfere with the results of normal wave field simulation.In this paper,the artificial boundary condition is introduced to reduce the influence of boundary reflection.For the decoupled and uncoupled differential forms of PML(perfectly matched layer) boundary conditions,different spatial difference orders are used for seismic wave field numerical simulation.When the order of spatial difference is increased,the non-decoupled PML differential form has more advantages in computational efficiency and implementation mode than those of the decoupled.Aiming at the problems of CE(Clayton-Engquist) boundary condition limited by the incident angle of incident wave,low accuracy at the boundary,and poor absorption effect,the second-order CE boundary condition and PML boundary condition are combined into a new combined boundary condition,which can reduce the thickness of attenuation band while ensuring the absorption effect,so as to improve the calculation efficiency.The effectiveness of this algorithm is verified by the numerical simulation results.