DQ地区地震噪声的判别分析

Analysis of seismic noises in the DQ area

在 DQ 地区,存在许多规则噪声。不识别这些噪声,在一些情况下,就会使地震解释工作误入歧途。这些地震噪声有:面波、初至折射波、多次反射—折射波、次生回头折射波、次生回头反射波、共反射点叠加中的“网状”噪声等。通过对这些地震噪声的判别分析,得到一些新的启示,即:①地震记录中的面波同相轴或时距曲线是一条曲线,并不是一条直线;②在多次波中,除多次反射波外,还存在多次折射波;③在地震记录中,除了与震源激发有关的波外,还出现一些与激发震源无关的次生折射波和次生反射波;④在共反射点叠加中,折射波当作反射波进行动校正和叠加,会导致叠加剖面中出现一些近似线性条带噪声;⑤浅层多次反射—折射波与次生回头折射波交叉干涉,且在叠加剖面中形成“网状”噪声。本文最后简要地介绍了地震噪声的特殊处理。

There are many regular noises in the DQ area.In some cases,seismic interpretation may be misguided by noise events,noises in the area are surface wave,first-break refraction,multiply-reflected refraction, secondary back refraction,secondary back reflection,“net noise”caus- ed in CDP stack and so on.The analysis of these noises leads to the following new knowledges. ·The event(or time distance curve)of surface wave in seismic record is a curve,not a straight line. ·There are multiple refractions in the record besides multiple reflections. ·There are not only the seismic waves associated with seismic source but also the secondary refractions and secondary reflections which are independent of the seismic source. ·Misusing refraction in both NMO correction and CDP stacking may cause some pseudo-linear strip noises in stacked seismic section. ·Cross-interference between shallow multiply-reflected refraction and secondary back refraction causes“net noise”in stacked seismic section. The special methods for removing the above noises are briefly re- commended finally.