振幅谱比法求取吸收参数的误差

AN IMPROVEMENT IN CALCULATING THE ERRORS OF ABSORPTION PARAMETERS WITH AMPLITUDE SPECTRAL RATIO METHOD

本文分析了当吸收系数与频率不成线性关系时,品质因素Q随频率f变化的情况,并考察了用振幅频比法求取吸收参数的误差。分析结果表明,当吸收系数α=Kf而r≠1(即吸收系数与频率不成线性关系)时,用振幅谱比法求取的Q_m随f的变化比较大,因此而引入的误差也比较大。在这方面,作者对振幅谱比法提出了改进,并在合成地震记录上进行了试算,所得Q_m的质量得到明显改善。

It is evident that a linear relationship between absorption coefficient and frequency is a prerequisite for calculating absorption parameters with an amplitude spectral ratio method. In fact, the subsurface lithological conditions are of great difference, which is impossible to satisfy this prerequisite anywhere. In this paper, the variation in quality factor with frequency is investigated when the relationship between absorption coefficient and frequency is unlinear and the errors produced by the amplitude spectral ratio method in this case are analysed. The example analysed in this paper shows that there exist great errors due to using this method. An improvement is made on the basis of the analysis, so that the method is suitable for the case that the absorption coefficlent is not linear with frequency. The calculated results from SVSP(Synthetic Vertical Seismic Profile) show that the improved method has higher accuracy of calculation.