平面声波在粗糙界面上的反射特征研究

基于有关粗糙界面的Rayleigh假设，讨论了平面声波按余弦规律快速变化的小尺度粗糙界面上的反射特征.研究表明：这类界面与位于该位置的一个过渡地层的作用相当.该过渡层的厚度为粗糙界面的起伏幅度，速度和密度为上下两层介质相应量的平均值.研究了埋藏很深的微粗糙界面所引起的地震反射（绕射）波的频散特性和走时的构成，即包含零炮检距反射时间、正常时差和界面粗糙时差三部分内容.该粗糙时差与空间坐标和时间坐标无关，与绕射波的阶次有关，绕射波尾随在反射波之后以某一固定的时差出现.且只有当界面的粗糙波长与地震波的波长相当时，才能观测到这类绕射波.该结论为粗糙界面地震反射资料的处理方法提供了理论依据.

Reflection features of planar acoustic waves from rough interfaces

Based on Rayleigh's hypothesis of rough interface,reflection features of planar acoustic waves from a rough interface with rapid-jumped cosine style are studied.The study indicates that such a interface has a response similar to that of an appropriately chosen transient layer at the same position.The thickness of the transient layer is equal to the fluctuant amplitude of the rough interface,and the velocity and density are the average of corresponding parameters of upper and lower media.For a small-scale rough interface imbed deeply,the dispersion characteristics of seismic reflections/diffractions are analyzed.It is deduced that the travel-time of reflections/diffractions consists of three parts: zero-offset reflection time(t-0),normal moveout and rough moveout.The rough moveout is related to the order of diffractions,while it is independent of receiver's location and t-0 time.Diffractions appear after reflection by a fixed moveout.And only when the rough wavelength of the interface is similar to the wavelength of seismic wave,diffraction can be observed clearly in the seismic record.This result offers a basis for seismic data processing of rough interfaces.