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波前弥合是地震波传播过程中普遍存在的现象.本文利用声波方程高阶有限差分数值模拟技术精细刻画出波在均匀球状异常体中的传播过程.除再现了波前弥合现象外,本文同时在前人工作基础上总结了波在异常体中的传播特征,分析了波前弥合现象与地震波主频、异常体尺度之间的关系.通过对绕射波、透射波波前能量的定量对比,总结了波前弥合现象对地震层析成像的影响规律.文中指出,在强散射条件下,射线层析方法只能反演出高速异常体,有限频层析方法只能反演出大尺度异常体,低速小尺度异常体无法用基于射线理论或有限频理论的透射走时层析成像方法反演出来;最后通过地震层析成像理论模型实验对以上规律的正确性进行了验证.本文同时根据波前弥合对Banana-doughnut现象进行了解释,并对地震波的散射给出了新的理解.
The wavefront bridging is a common phenomenon in the propagation of seismic waves.In this paper, the propagation of waves in anomalous spherical anomalies is finely depicted by using the high-order finite difference numerical simulation of acoustic wave equations.In addition to the wavefront bridging phenomenon, Based on the previous work, the wave propagation characteristics in the anomalous body are summarized, and the relationship between the wavefront interlacing phenomenon and the dominant frequency and the anomaly body size of the seismic wave is analyzed.By the quantitative comparison of the diffracted and transmitted wavefront energies, This paper summarizes the influence of wavefront bridging phenomenon on seismic tomography.The paper points out that under the condition of strong scattering, ray tomography can only retrieve high-speed anomalous body, the finite-frequency tomography method can only retrieve large-scale anomalous body, The low-speed and small-scale anomaly bodies can not be inverted by the transmission time-history tomography method based on the ray theory or the finite-frequency theory. Finally, the correctness of the above law is verified by the seismic tomography theoretical model experiment.In this paper, The Banana-donut phenomenon is explained and a new understanding of the scattering of seismic waves is given.