Rayleigh波ZH幅度比(椭率)研究综述

Review on Rayleigh wave ZH amplitude ratio (ellipticity)

Rayleigh波ZH幅度比,又称为Rayleigh波椭率(Ellipticity),是指Rayleigh波垂直分量和水平分量的比值.椭率是随频率变化的函数,最早由Boore和Toks9z(1969)提出将其用于反演地壳结构.对于3D介质结构,ZH幅度比不仅受到台站下方的结构控制,同时也受台站附近半波长范围内结构相对于其下方结构扰动的影响.对于水平层状的1D介质,Rayleigh波ZH幅度比只和台站下方的结构有关,与震源机制和方位无关.相对于Rayleigh波相速度,作为独立的量,ZH幅度比对浅层速度结构更为敏感,因此可以用来约束浅层,尤其是沉积层的速度结构.近年来,大规模地震台阵的出现为研究面波成像方法提供了高质量的三分量数据,也为Rayleigh波ZH幅度比的应用提供了基础数据,因此,Rayleigh波ZH幅度比和相(群)速度的联合反演成为研究者关注的课题,并广泛用于弥补单独相(群)速度反演对浅层结构约束不够的缺点.本文从横向均匀介质的面波理论出发,结合三维面波的散射理论及变分原理,对Rayleigh波ZH幅度比的理论基础,灵敏度核的计算,ZH幅度比的提取方法及其在地壳结构反演中的应用进行评述.

The Rayleigh wave ZH amplitude ratio, also known as the Rayleigh wave ellipticity, refers to the ratio of the vertical and horizontal components of the Rayleigh wave. The ellipticity is a function that varies with frequency and its application in referring the earth crustal structure was first proposed by Boore and Toks9 z(1969). For 3 D structures, the ZH amplitude ratio is controlled by the structure below the station and the disturbance in the half wavelength range. For horizontal layered 1 D media, the Rayleigh wave ZH amplitude ratio is only related to the structure below the station, and independent on the source mechanism and orientation. The ZH amplitude ratio is more sensitive to shallow structures than the phase velocity of the Rayleigh wave, and as an independent parameter which can therefore be used for the constraint of shallow structure, especially the sedimentary basin. In recent years, the development of seismic array has provided high-quality three-component data for the study of surface wave imaging methods and the application of Rayleigh wave ZH amplitude ratio. Therefore, the joint inversion of the Rayleigh wave ZH amplitude ratio and phase(group) velocity has been paid more attention by researchers. As a complementary data, Rayleigh wave ZH magnitude ratio is widely used to constraint the shallow structure, which cannot be resolved well only by the phase(group) velocity inversion. The theoretical basis, sensitivity kernel calculation, measurement and application in crust structure inversion of Rayleigh wave ZH amplitude ratio are reviewed in this paper.