面波压制的TT变换法

TT Transform Method of Surface Wave Suppression

在地震勘探中,面波的频率比其他有效地震波的频率低,往往被视作干扰波而需要压制,以突出有效波。TT(time-time)变换具有很好的频率聚集能力,它将高频信号聚集在TT变换域的对角线位置,通过提取TT变换域的对角线附近的元素,就可以压制低频面波,突出反射波。对物理模型和实际数据进行处理,并与传统的高通滤波方法进行对比,结果表明:TT变换实际上是S变换的延伸,与S变换有着密切的联系,有无损可逆性,而且具有很好的频率聚集能力。TT变换在压制面波方面有较好的效果,但在提取高频、压制低频的同时,漏掉了一些低频的有效信号,同时也保留了部分高频干扰,这是TT变换在信号分析中的不足之处。因此,在实际应用中应将TT变换和S变换结合起来,避免一些解释上的假象。

In seismic exploration,surface waves have lower frequency than effective signals,and often needs to be suppressed to enhance effective seismic waves.TT transform（time-time transform） has very good frequency gathering property and can concentrate higher frequencies more strongly around diagonal positions in TT field.The surface wave can be suppressed by extracting the diagonal elements of TT spectrum.Compared with the traditional high-pass filter method,processing results by TT method about physical model and real seismic data shows that TT transform is the extending of S transform and has a close relation with S transform.It is invertible and has good frequency gathered ability.TT transform shows good effect in the suppression of surface wave,however,it loses some low frequency effective signals and retains parts of the high frequency interference waves during extracting high-frequency,and suppressing low-frequency,which is the shortage of TT transform in signal analysis.Therefore,TT transform and S transform should be combined in practical applications to avoid some mistakes of interpretation.