一种新的高精度广角反射动校正方法

A new method for wide-angle reflection normal moveout correction with high precision

从水平多层介质的时距方程出发,采用参数方程求导的方法,求取时间t关于炮检距x在炮点附近的各阶导数,从而获得在炮点附近展开的六阶多项式方程;再通过对方程性态的分析,经过数学变换,给出大炮检距情况下的广角动校正量估算公式,并从理论上分析了六阶多项式和广角动校正公式的适用区间。数值计算和模拟结果表明:在炮检距与目的层深度之比大于4的情况下,本文提出的新动校正方程仍可以将旅行时相对误差控制在1%的范围内,并能把不同层位近、远炮检距处的同相轴校正平直,是一种精度较高的广角反射动校正新方法。

First based on traveltime-to-distance equation of horizontal multilayered media,we differentiate all-order derivatives of travel time t with respect to offset xnear the shot point,and substitute the result into truncated Taylor's expansion for travel time t.A six order polynomial equation near the shot point is obtained.Then,we get the approximate formula of wide-angle reflection normal moveout correction under long-offset conditions by analyzing characteristics of relational equations.Finally,we discuss theoretically application conditions of the six order polynomial and the approximate formula.Based on our numerical simulations,the proposed normal moveout correction method can control the relative error rate of traveltime within 1% when offset is more than 4 times of depth,and it can stretch seismic events at near and far offsets.Therefore,this method may be used as a high precision method for wide-angle reflection normal moveout correction.