一种分离纵横波的方法

A method for separating P wave from S wave

分离纵横波有多种方法,比较常用的是τ-p变换法。一般认为纵波和转换横波在τ-p域彼此是近于分离的,无大的重叠区, 因而可采用一刀切的办法分离这两种波。实践说明,这两种波的斜率值在一个很大的范围内是难以分离的,不好一刀切。我们认为按纵波或横波的轨迹进行切除,可以较好地解决这个问题。文中给出了轨迹跟踪切除法分离纵横波的原理,以及记录道距、变换间隔和随机噪声对分离效果的影响。理论模型和实际资料试验结果说明,当变换间隔dp=5.4×10^(-6)不变时,对同样排列长度,道距dx缩小一倍(道数增加一倍),假频明显减少,分离效果好;当道距dx不变时,变换间隔dp减小一倍,假频消失;分离效果更好。可见,减小dx和dp,都会改善分离的效果;随机噪音不影响分离效果。

There are many methods for separating P wave from S wave, τ-p transform method is often used. It is generally thought that P wave and converted S wave in τ-p domain are almost separate or little overlapped, therefore they can be parted from each other by simple muting. As a matter of fact, simple mating can not separate P wave from converted S wave because their corresponding slope values are hardly distinguishable within a big extent.We deem that the separation of P wave from S wave can be well done by muting along P wave trace or S wave trace. We demonstrate the principle of this trace muting method for separat- ing P wave from S wave, and detail how separation effect is influenced by group interval, transform spacing or random noise. Theoretical modeling and real data experimental result led to the following conclusive points: ·If transform spacing is cons ant (dp=5.4×10^(- )), halving the group interval in the case of fixed spread length(doubling the channels) greatly reduces aliasing, thus bringing good separation effect. ·If group interval (dx) is constant, halving the transform spacing removes aliasing to bring better separation effect. It is thus clear that reducing dx or dp can improve separation effect. Random noise does not damage separation effect.