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地球物理CT技术又称为ST(Seismic tomography)技术。它是近年来以医学CT技术为基础而发展起来的一种以数字化地震波观测台网、地震波传播理论、图象重建理论和现代化计算机技术相结合,以重现地球内部三维结构的一门新技术。 本文简述了ST的研究历史和近年来的主要成就以及国际上进行该项研究的几个庞大计划,美国的IRIS计划和欧州的ORFEUS计划。概述了我国至1985年以来开展这方面工作的情况以及所取得的主要进展。文中给出了目前ST的几种主要常用方法,卷积反投影方法和代数重建方法,讨论了它们的适用性,各自离散化公式的优点和存在的问题,分析了可能的改进途径。针对地震学研究的复杂性,对大量的近震、地方震资料,详述了应用发散束CT方法的可能性、重要性。给出了二维情况下的扇性束CT重建方法。
Geophysical CT technology is also known as ST (Seismic tomography) technology. It is a new technology based on medical CT technology which is developed in recent years with the combination of digital seismic wave observation network, seismic wave propagation theory, image reconstruction theory and modern computer technology to reproduce the internal three-dimensional structure of the Earth . This article gives a brief account of ST’s history of research and major achievements in recent years, as well as several major international studies on the program, the IRIS program in the United States and the ORFEUS program in Europe. Summarized the situation of our country’s work in this field since 1985 and the major progress made. In this paper, several common methods of ST, convolution backprojection and algebraic reconstruction are given. Their applicability, the advantages and problems of their respective discretization formulas are discussed, and the possible ways of improvement are analyzed. According to the complexity of seismological research, the possibility and importance of using the method of divergent beam CT are described in detail for a large number of near-earthquakes and local seismic data. A two-dimensional fan beam CT reconstruction method is given.