转换波变速抽道速度分析方法

Converted-wave velocity analysis by velocity-variable trace gathering

转换波反射点不在炮点-检波点的中心点正下方，其偏离中心点的距离随转换横渡速度Vs和反射点深度h的变化而变化。地面接收到的来自地下某点的转换波反射信号到达时间也不遵循（纵波反射的）双曲线规律，因此不能用纵波速度分析法对转换波进行分析。本文提出的在纵向上接深度变化、而在横向上作变速抽道的转换波叠加速度谱分析方法，避开了转换波反射的不对称性和信号到达时间的非双曲线特征所带来的困难，使转换波的速度精确分析成为现实。应用本文方法对92LYS501测线实际转换渡地震数据进行处理，获得了比较理想的效果。

The reflecting point of converted wave is not beneath the center of the line between source point and corresponding receiving point, and its deviation to the center depends on both velocity Vs of converted shear wave and reflecting point depth h. Reflection times of converted waves which are reflected at a subsurface point and received on surface do not follow hyperbolic law of reflected compressional wave,so that velocity analysis method for compressional wave does not apply to converted waves.Stack velocity analysis method for converted wave , which considers depth variation in vertical direction and does velocity-variable trace gathering in lateral direction, avoids troubles resulting from both the asymmetry of converted-wave line-ups and the non-hyperbolic characteristic of reflection time values to achieve accurate velocity analysis of converted wave. This method has been used to process converted-wave data of 92LYS5Ol seismic line, bringing desirable result.