Forward modeling of pseudo P waves in TTI medium using staggered grid

IF 1.6 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Wang Luchen, Chang Xu, W. Yibo
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引用次数: 4

Abstract

A tilted transversely isotropic (TTI) medium is a good approximation for anisotropic problems. We discuss the property of a 3D tilted transversely isotropic (TTI) medium and use pseudo P waves to simulate the P component of the elastic wave field in the weak elastic anisotropy approximation. We compare forward features of 3 second-order difference equations of pseudo P waves based on Hooke's law, elastic wave projection and dispersion equation, respectively. Now numerical calculation of these equations uses regular grid finite difference method, which is of low efficiency, low accuracy and is unstable in TTI simulation. In order to improve the calculating accuracy, this paper builds the staggered grid finite difference format for each forwarding simulation. Comparing three different numerical expressions of pseudo P wave equation in a 3D TTI medium, we find that the method based on dispersion equation is more convenient to simulate elastic P wave propagation and has lowest numerical noise. By analyzing the frequency dispersion characteristics based on different angles of isotropic symmetry axis, we introduce appropriate SV wave velocity in calculation to keep calculation stable. An example of a 2D simple synthetic model shows that the staggered grid forwarding method allow us to obtain a smooth and stable pseudo P wave field. With this strategy, 2D BP TTI reverse time migration can also achieve basically stable migration results.
TTI介质中伪纵波的交错网格正演模拟
倾斜的横向各向同性(TTI)介质是各向异性问题的一个很好的近似。讨论了三维倾斜横各向同性(TTI)介质的性质,利用伪P波模拟了弱弹性各向异性近似下弹性波场的P分量。分别比较了基于胡克定律的3种伪纵波二阶差分方程、弹性波投影方程和频散方程的正演特征。目前这些方程的数值计算采用正则网格有限差分法,效率低、精度低,在TTI仿真中不稳定。为了提高计算精度,本文为每个转发仿真构建了交错网格有限差分格式。通过对三维TTI介质中伪纵波方程的三种不同数值表达式的比较,发现基于色散方程的方法更便于模拟弹性纵波传播,并且具有最低的数值噪声。通过分析各向同性对称轴不同角度的频散特性,在计算中引入合适的SV波速,保证计算的稳定性。二维简单综合模型的算例表明,交错网格转发方法可以获得光滑稳定的伪P波场。采用该策略,二维BP TTI逆时偏移也能获得基本稳定的偏移结果。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
地球物理学报
地球物理学报 地学-地球化学与地球物理
CiteScore
3.40
自引率
28.60%
发文量
9449
审稿时长
7.5 months
期刊介绍:
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