层析成象技术(由希腊字“tomo”意为切割而来)是一种用数学方法把许多从射线路径得到的信息组合成射线在其中传播的介质的两维图象。医学上的断层疹断技术是用X射线重现身体网各种器官的图象,而我们的地震成象技术则利用若干界面产生的反射波来重现地下地层速度的图象。实际上,地震成家术在以下几个方面比医学疹断术要复杂些:(1)射线在地层内是沿着弯曲路径传播的(这就使问题变为非线性的了);(2)反射层的深度是未知的(因此我们同 Tomography (cut by the Greek word “tomo”) is a two-dimensional image that mathematically combines many information derived from a ray path into a medium through which the ray propagates. The medical rash technique uses X-rays to reproduce images of various organs of the bodily net. Our seismic imaging technique uses reflected waves from several interfaces to reproduce images of subterranean formation velocities. In fact, earthquakes are more complicated than medical rashes in the following ways: (1) radiation travels along curved paths within the formation (which makes the problem nonlinear); (2) The depth of the reflective layer is unknown (so we are the same