基于小波包分解的地层吸收补偿

A METHOD TO COMPENSATE EARTH FILTERING BASED ON WAVELET PACKET

在分析地震反射波勘探信号小波包分解特性的基础上，提出了基于小波包分解的地层吸收补偿方法．如果没有地层吸收，浅层反射波和深层反射波具有相同的振幅谱而相位谱相差一线性相位．如果把地震记录分成不同的频段，不同频段对于时间的能量分布关系具有相似性，即对所有频段的深层反射的能量与同一频段浅层反射能量之比应该相同；只是不同频段的绝对能量大小不一样．由于地层的吸收造成各频段能量对时间的分布不同，如果给这些频段乘以时变权使各频段能量对时间的分布相同，就起到了对地层吸收的补偿作用．该方法首先用小波包对地震勘探信号进行分频，然后根据地层吸收的特点，在每一个频段上分别提取每一个时间点的吸收系数并用其倒数加权每一个小波包系数，再用加权后的小波包系数重构地震反射波记录消除地层吸收．该方法适合Ｑ值未知的情况，对变Ｑ和常Ｑ都能适应．从实际应用效果看，该方法能很好的补偿地层的吸收。

The Earth's filter response to seismic wave can be approximated by variable Q attenuation. A model to compensate earth filtering is developed based on the wavelet packet decomposition. According to the model, a new method to compensate earth filtering is presented. The steps of the method are : Firstly, seismic wave is decomposed into different frequency bands. Then, according to the model of compensate earth filtering, attenuation coefficients are found for each frequency component. Each wavelet packet decomposition coefficient is divided by attenuation coefficient. Finally, seismic wave is reconstructed from modified frequency components to compensate earth filtering.