时频域球面发散和吸收补偿

Compensation for spherical divergence and absorption in time-frequency domain

根据地震波振幅衰减随不同的频率成分有不同的吸收衰减特点，本文基于小波变换理论，提出了时频域球面发散和吸收补偿的处理方法。首先分析了振幅衰减的物理机制，将吸收因子分解为地表一致性吸收项和大地吸收项。然后利用小波分解的特性将地震记录分解成不同的频道（尺度），拟合出各个频道随时间和炮检距变化的低频吸收能量曲线，对相应的频道进行补偿，再将各个频道重构为经过补偿后的地震记录，以消除大地吸收项对振幅的影响。而地表一致性吸收项留待后续处理去解决，如地表一致性及褶积。经过理论试算和实际处理表明，本方法能较好地消除球面发散和大地吸收对振幅的影响。

In view of the fact that seismic amplitude attenuation varies with the absorp-tion of different frequency contents, and based on wavelet transform theory, we put forward a new processing method for compensating spherical divergence and ab-sorption in the time -frequency domain. The method includes the following points:Absorption factor is decomposed into surface-consistent absorption compo-nent and earth absorption component by analysing the geophysical mechanism of amplitude attenuation.Seismic record is decomposed into different frequency traces by using the characteristic of wavelet decomposition.Low-frequency energy absorption curve that varies with time and offset is drawn to compensate its corresponding frequency trace.Each frequency trace is then converted into the selsmic record that has un-dergone compensation, removing the negative influence of earth absorption upon seismic amplitude.Surface-consistent absorption can be eliminated in the late processing steps such as surface-consistent deconvolution.Theoretical and practical results indicate that the method can compensate quite de-sirably the amplitude attenuation due to spherical divergence and earth absorption.