Imaging of Inhomogeneous Structure Based on Seismic Array Observations

Abstract

Seismic array analysis is one of the most effective techniques in order to estimate inhomogeneous structure of the Earth. Especially, inhomogeneities with shorter wavelength than typical wavelength of seismic waves behave as scatterers for propagating seismic wave. There are two categories for the analysis method of array observation data. One is the determination of location and strength of scatterer by beam forming the array data. FK and semblance analysis are adopted to estimate ray directions coming to the array. Slant stack method is a technique for back projecting scattered wave field to the Earth's interior. Scatterer distribution obtained by these methods relates to seismic activity and existing fracture zone. Another category is estimation of statistical parameters of inhomogeneity. Inhomogeneous structure is characterized by correlation function of fluctuation of velocity and density. The function can relate to variation of amplitude and phase observed by a seismic array. Thickness of inhomogeneous layer and both of strength and correlation distance of the structure have been estimated in continental crust and upper mantle, . Many regional studies have been carried out and suggested an image of randomly inhomogeneous structure in the Earth. In order to construct more realistic model of the Earth's interior, we need to estimate short wavelength structure in more detail. Therefore, it is necessary to develop new techniques by merging the methods of both categories.