非均匀介质全局广义R/T递推传播矩阵法二维SH地震波模拟研究

Global generalized R/T recursive propagation matrix method for 2-D heterogeneous media SH seismic wave simulation

地球深部圈层及沉积盆地是一种分区非均匀介质系统,其中不规则地层边界(含起伏地表)对地震波的主要特征有显著影响,而地层的随机非均匀性则主要影响地震波的散射和衰减特征.为了精确刻画不规则地层边界对地震波的反射、透射效应以及非均质体散射引起的地震波衰减效应,全局广义R/T递推传播矩阵法(GGRTM)被提出并逐步发展成为继有限元和有限差分方法之后的另一种复杂介质高精度地震波传播半解析求解方法.在已有的此类方法中,不规则边界均匀地层GGRTM法的优势在于对不规则地层边界的反射和透射效应的准确模拟,而非均质地层薄板化GGRTM法则能准确描述非均质体散射对地震波衰减的影响.本文吸收这两种已有方法的优势,提出了一种考虑非均匀介质、不规则边界的全局广义R/T递推传播矩阵混合方法,并将其用于对边界不规则、层内非均质的复杂模型的二维SH波场模拟.随后在本文方法与边界元法对比研究的基础上讨论了方法的模拟精度.研究结果表明本文提出的混合法是一种解决复杂模型高精度地震模拟的有效方法.

The deep earth spheres and sedimentary basins are partitioned heterogeneous medium systems,in which irregular stratigraphic boundaries(including undulating surface)have a significant influence on the main characteristics of seismic waves,while the random inhomogeneity of the strata mainly affects the scattering and attenuation of seismic waves feature.In order to characterize the seismic wave reflection and transmission affected by irregular stratum boundaries and the seismic wave attenuation caused by heterogeneous body scattering accurately,the global generalized R/T recursive propagation matrix(GGRTM)method was proposed and gradually developed into another semi-analytical solution method for high-precision seismic propagation in complex media after the finite element and finite difference methods.Among the existing methods,the advantage of the GGRTM method for homogeneous medium with irregular boundaries situation lies in the accurate simulation of the reflection and transmission effects of the irregular boundaries,while slicing heterogeneous media into a series of horizontal and heterogeneous slabs and cooperate with GGRTM method can accurately describe the scattering of heterogeneous bodies.Here we absorb the advantages of these two existing methods,and propose a global generalized R/T recursive propagation matrix hybrid method that suits for inhomogeneous media and irregular boundaries,and then use it to simulate the 2-D SH wavefield of a complex model with irregular boundaries and inhomogeneous layers.Subsequently,the simulation accuracy of the method is discussed based on the comparative study of the method in this paper and the boundary element method.The results show that the hybrid method proposed in this paper is an effective way to solve the high-precision seismic simulation of complex models.