VSP资料求层速度的射线追踪折线法

对于大偏移距ＶＳＰ（垂直地震剖面）测量，以直达波直射线传播路径为假设条件计算的层速度会产生较大的误差（特别是中浅层）．本文给出一种求层速度的射线追踪折线法，对３个理论模型试算了层速度，其结果与相应直线法计算的层速度比较表明：当偏移距较小时，直线法和折线法求的层速度均与真层速度吻合；但当偏移距较大时，直线法求出的层速度不再适用，而折线祛所求出的层速度仍然比较精确．

Ray - Tracking Method of Computing Interval Velocities for VSP

When far offset VSP measurement is made, the error for interval velocities which are calculated by using the straight line method is larger, assumed that the first arrivals propagate along the ray - paths through a homogeneous medium. In this paper, the interval velocities for VSP measurement are computed by the ray-tracking straight-line segment method, assumed that the first arrivals propagate along the raypaths through a horizonally stratified medium. The interval velocities for three data models are calculated by using the straight line method and the straight-line segment method respectively. The comparisons between their velocities show that for zero offset VSP measurement both the interval velocities calculated by using the two methods are agreed with real interval velocities and for far offset VSP measurement the interval velocities that are computed by the straight line method are not acceptable. But the interval velocities that are calculated by the straight-line segment method are correct.