匹配追踪保幅地震AVF剖面及同频率剖面的构建

地震信号分频技术是寻找薄层及小尺度地质目标的必备工具。Morlet小波变换由于其优良的时频局部化性能，被广泛应用于地震资料分频处理当中。但是，Morlet小波变换方法得到的振幅随频率变化(AVF)剖面从低频到高频存在同相轴分叉现象，同频率剖面也存在谐波效应。根据匹配追踪算法的特点，提出了一种保幅AVF剖面及同频率剖面构建方法。该方法利用地震匹配追踪分解的时频原子构建AVF剖面，并从中提取给定频率的信号，每个时频原子的贡献由该时频原子在给定频率位置的谱值大小决定，获得的同频率剖面避免了常规滤波分频方法造成的平行同相轴假象，分频效果更理想。另外，该方法得到的AVF剖面上没有出现同相轴发散、漂移现象，可以更方便地进行AVF分析。

Seismic frequency-division technology is an essential tool for identifying thin beds or small-scale geological targets.Morlet wavelet transform is widely used in seismic frequency-division owing to its time-frequency localization property.However,the events are diverged from low to high frequency in the AVF (amplitude variation with frequency) section derived by Morlet wavelet transform.Moreover,there exists tuning effects in its isofrequency section.In this paper,based on the characteristics of matching pursuit algorithm,an amplitude-preserved AVF section construction method is proposed.The time-frequency atoms decomposed from matching pursuit are utilized to construct AVF section and isofrequency signal for given frequency.The weight of each atom is determined by its spectrum value at the given frequency.More satisfactory isofrequency section can be obtained because parallel alias events caused by filtering frequency-division methods do not exist anymore.At the same time,since events divergence and shift phenomena are vanished in the AVF section derived from this method,AVF analysis can be done conveniently.