变V₀平均梯度法

AVERAGE GRADIENT METHOD WITH VARIABLE V₀

地质矿产部第五物探大队

在地质情况较为复杂的地区, 地下介质真速度并非按V（z）=V₀（1+βz）的假设线性变化, 而是一条呈非线性变化的高次幂曲线。所以, 仍用常规作图方法绘制剖面, 对深部陡倾产状地震波组的勾绘易产生畸变。同样, 用恒定的V₀、β参数拟合出的平均速度, 也往往与实测平均速度曲线出入较大。采用变V₀平均梯度法能够弥补这一缺陷, 比较客观地反映地下介质的实际情况。本文论述了变V₀平均梯度法的基本原理, 找到了从平均速度曲线或均方根速度曲线上求取V₀（t₀）、β（t₀）和α（t₀）的近似解法, 给出了程序框图及具体计算过程, 最后以实例分析了该方法的应用效果。

In areas of complex geology, the ture velocity of the strata doesn't variate linearly in accordance with the formula V(z) = V₀(1 + βZ) but it variates non-linearly and presents to be a curve of higher degree. Hence, if the seismic section is mapped by conventional method, the distortion would be easily caused in the procedure of constructing the deep reflectors with steep occurrence. Similarly, the average velocity fitted by the constant V₀ and the parameter β do often deviate obviously from the average velocity measured. Fortunately, there is a remedy for such a defect by adopting the technique of average gradient with variable V₀ and the realistic situation about the medium underground could be reflected more objectively. In this paper, the basic theory of the average gradient technique with variable V₀ was described and the approximate resolution for extracting V₀(t₀), β(t₀) and α(t₀) from curves of average velocity or root mean square velocity was found. The program flowchart and the computing procedure were given. At the end of this paper, the effects of the technique recommended were discussed and examined.