从单源VSP数据中提取横波分裂参数的算法

An algorithm for extracting shear-wave splitting parameters from single source VSP data

1. 国防科技大学应用物理系,长沙410073;2. 湖南湘西教育学院,吉首416000

Dept.Of Appl. Physics, Natinal University of Defense Tech, ChangSha 410073

在横波地震勘探中,一个常见的应用就是利用多分量数据确定快横波 (qS₁)的极化方向以及它与分裂出的慢横波 (qS₂)之间的时间差。为确定这 2个参数,通常采用 2个正交震源,这已得到了较为系统的研究。但当只有单源数据时,通常必须假设介质是均匀各向异性介质。本文基于矢量褶积模型,导出了一个从单源多分量数据中获取横波各向异性参数的算法。此算法可以应用于均匀各向异性介质,也可以用于复杂地表及各向异性特性随深度变化的情况。我们用合成地震数据以及实际数据对该算法进行了验证,并与多源算法的应用结果进行了比较。

In the shear wave exploration, a common application is to extract fast shear wave polarization direction and time delay between fast and slow shear waves from multi component data. To obtain these two parameters, it is usual to using four component data, that is two horizontal receivers with two orthogonal sources. Systematic researches have been carried out since the data acquisition using this configuration was adopted. However, in many cases, only two (or three) component data from one source is available. Thus to obtain anisotropic parameters from the data, one should assume that the medium is uniform anisotropic. In the paper, based on vector convolutional model, we derived an algorithm to extract the polarization direction of the fast shear wave and the time delay between fast and slow shear waves from single source two component data. The algorithm could be applied to media with complex near surface whose anisotropic properties vary with depth as well as uniform anisotropic media. Both synthetic seismic data and field data have then been used to test the algorithm. A comparison with four component data (field data) was also given.