最小静校正误差浮动基准面方法

基准面是静校正计算中的一个最重要参数。静校正计算时一般假设射线在近地表附近为垂直传播，这种假设往往与射线实际传播的路径不符。如果选择不同的基准面，相应的速度分析和叠加结果也会不同。本文分析了静校正误差与基准面位置、低速带结构的关系，并通过理论和模型计算，分析了不同浮动基准面对速度分析结果和静校正计算误差的影响，提出了最小静校正误差浮动基准面的确定方法。在此浮动基准面上求取的叠加速度仅取决于低速带底板下伏介质的速度，而与地形、低速带无关。利用此法做静校正，所获得的叠加速度可以直接用于时深转换；动校正后的时间均方差较小，有利于实现同相叠加。

A new method for determination of floating datum in static corrections.

The datum is an important parameter in staties calculation. The general assumption in calculat-ing static correction is that the near-surface ray-paths travel vertically, which does not conform with the actual travelling path of ray. If selecting different datum,the corresponding results of veloc-ity analysis and stack are different too. So the errors of static corrections resulted from the assumption brings a bad results. The paper analyzed the relation between the errors of static corrections and the position of datum as well as the structure of low velocity layer, analyzed the results of velocity analysis for different floating datum and influence of the errors of calculating static corrections and presented the determination method for floating datum having minimum errors of calculating static corrections. The stack velocity calculated on the floating datum depends on the velocity of medium underlying the low velocity layer and is indepen-dent of topography and low velocity layer. The stack velocity resulted from using the method for static correction can be directly used for time-depth transformation; the root-mean-square deviation of time after NMO is smaller, which is suitable to realize in-phase stack.