Variable-coordinate forward modeling of irregular surface based on dual-variable grid  

基于时空双变网格的起伏地表变坐标系正演模拟方法（英文）

作　　者：黄建平[1] 曲英铭 李庆洋 李振春[1] 李国磊[2] 步长城[2] 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]胜利油田分公司物探研究院,山东东营257000

出　　处：《Applied Geophysics》2015年第1期101-110,123,共11页应用地球物理（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.41104069 and 41274124);the National 973 Project(Nos.2014CB239006 and 2011CB202402);the Shandong Natural Science Foundation of China(No.ZR2011DQ016);Fundamental Research Funds for Central Universities(No.R1401005A)

摘　　要：The mapping method is a forward-modeling method that transforms the irregular surface to horizontal by mapping the rectangular grid as curved; moreover, the wave field calculations move from the physical domain to the calculation domain. The mapping method deals with the irregular surface and the low-velocity layer underneath it using a fine grid. For the deeper high-velocity layers, the use of a fine grid causes local oversampling. In addition, when the irregular surface is transformed to horizontal, the flattened interface below the surface is transformed to curved, which produces inaccurate modeling results because of the presence of ladder-like burrs in the simulated seismic wave. Thus, we propose the mapping method based on the dual-variable finite-difference staggered grid. The proposed method uses different size grid spacings in different regions and locally variable time steps to match the size variability of grid spacings. Numerical examples suggest that the proposed method requires less memory storage capacity and improves the computational efficiency compared with forward modeling methods based on the conventional grid.坐标变换法通过将物理空间的曲网格映射为计算空间的矩形网格,将起伏地表转化为水平地表,同时将物理空间的波动方程转化为计算空间的波动方程,在计算空间完成数值模拟,坐标变换的方法对处理起伏自由边界具有较好的适应性和应用效果。本文在传统坐标变换方法的基础上,根据计算区域速度差异采用不同的网格大小和采样时间步长,提出了一种基于时空双变网格的起伏地表坐标变换正演模拟方法。在编程实现算法的基础上,通过典型模型波场模拟试算结果分析可知:(1)变网格方法与常规方法波场模拟误差在0.5%左右;(2)变网格方法计算效率视不同的变网格区域面积及变网格大小可提高几倍量级,在本文模型和计算参数下提高约5倍。(3)在满足模拟精度及频散条件要求下,变网格方法较全局细网格算法能显著节约计算内存。为此,针对起伏地表数值模拟,本文方法具有较高的模拟计算精度和一定的适应性。

关 键 词：MAPPING irregular surface BOUNDARY GRID forward modeling 

分 类 号：P631.4[天文地球—地质矿产勘探]