大延伸非均匀介质中地震波全弹性散射理论Ⅱ——弹性波多次散射理论

THEORY OF FULL ELASTIC SCATTERING OF SEISMIC WAVES FOR HETEROGENEOUS MEDIA OF LARGE EXTENT——Ⅱ THEORY OF ELASTIC WAVES OF MULTIPLE SCATTERING

推出大延伸非均匀连续介质的弹性波能量传输表达式,并以此为基础建立并发展了相应的弹性动力学能量传递理论.构造了一个基于非均匀薄层或非均匀相屏单次散射迭代法的多次散射模型.该模型既适用于弱散射,也适用于强散驰 既适用于普通散射,也适用于转换散射;尽管高频情况下只考虑普通散射及前向散射.应用该模型计算了弹性多次散射的能通量,处理了散射衰减问题。数值实验的结果表明,短周期地震图上的尾波主要来源于S波散射。

In this paper, an elastodynamic energy transport theory to form expressions for energy transmission through a heterogeneous continuum of large extent is developed. A model of multiple scattering for a random elastic continuum is constructed by an iterative method based on single scattering by a thin heterogeneous layer or screen. This model is available both for strong scattering and for weak scattering, and both for common-type scattering (P-P and S-S) and converted scattering (P-S and S-P), although here we assume high frequencies so that only forward scattering and common-type scattering are considered. Using this model, the energy flux of multiple scattering is calculated and the scattering attenuation is treated. Some numerical results have been obtained. These results show that coda waves in seismograms mainly come from the scattering of S waves.