基于转换波旅行时计算倾斜界面转换点位置的搜索法

提出了在深度未知的条件下依据转换波旅行时计算倾斜反射界面转换点的方法。首先证明了在给定已知条件下唯一转换波旅行时对应唯一的转换点;然后根据地震波Snell定律和射线几何关系,建立起一元二次方程并求解得出转换点坐标的表达式,再利用搜索法计算转换点的坐标,依据最小旅行时误差确定最佳转换点位置;并与其它倾斜界面转换点计算方法进行了比较。应用上述方法对均匀介质单个倾斜界面模型进行了转换点位置计算,根据计算结果分析了P-SV波旅行时、界面倾角和转换横波速度等参数变化时,转换波转换点位置的变化规律。

A solution for the P-SV wave conversion point with traveltime and without reflector depth is proposed for the first time.First of all,the unique conversion point corresponding to unique P-SV wave traveltime is proved in given condition.Secondly,according to Snell’s law and ray geometric relations of seismic wave,a quadratic equation is deduced and the expression of conversion point is solved.Then the coordinates of conversion point is calculated by searching method and the location of conversion point is determined by the minimum traveltime error.The proposed method is compared with the other conversion point calculation methods and applied to calculate the conversion point location for single dip reflector of homogeneous media.Finally,the distribution regularity of conversion point is analyzed corresponding to the variation of P-SV wave traveltime,reflector dip,P-SV wave velocity and other parameters.