基于改进NAD方法的频率域声波逆时偏移

逆时偏移成像具有高分辨率的特点,在频率域实施能提升偏移成像效率.数值求解波动方程是逆时偏移成像的关键环节,数值算法的优劣直接决定着偏移过程的计算效率与成像结果的质量.本文在频率域近似解析离散化(NAD)方法的基础上通过优化网格差分模板系数构造改进NAD方法,保证数值离散精度的同时可缓解阻抗矩阵的病态程度,以此提高频率域...

Frequency-domain acoustic reverse time migration based on improved NAD method

Reverse time migration imaging has the characteristics of high resolution,and it can improve the efficiency of migration imaging when performed in the frequency domain.Numerically solving the wave equation is a key point of reverse time migration imaging.The pros and cons of numerical algorithm directly determine the computing efficiency of migration processes and the quality of imaging results.In this paper,based on frequency-domain nearly analytic discrete(NAD)method,an improved NAD method is constructed by optimizing the grid stencil coefficients to relieve the ill-posed condition of impedance matrix as well as ensuring the accuracy of numerical discretion.To improve the computing efficiency of frequency-domain forward modeling,this method is used in the frequency-domain reverse time migration.By respectively performing migration imaging of sunken model,Sigsbee2 B model,and Marmousi model,and comparing the corresponding results with fourth-order standard NAD method and fourth-order ordinary finite difference method,the advantages of improved NAD method in suppressing numerical dispersion and improving imaging efficiency have been fully reflected.