速度有严重的横向变化时,叠前深度偏移有能力使地下反射面成像。但是,为了用叠前深度偏移对这样的构造精确成像,关键是需要建立非常精确的速度模型。建立的速度模型是根据炮检距上的一致性由数据导出的,也就是说,如果速度模型正确,不同炮检距上的成像彼此是相同的。速度模型的建立是一个典型的迭代过程,并且需要多次进行大量的叠前深度偏移运算。 Prestack depth migration has the ability to image subsurface reflectors with severe lateral variations in velocity. However, in order to accurately image such a structure with pre-stack depth migration, the key is to create a very accurate velocity model. The established velocity model is derived from the data based on the consistency over the offset, that is, if the velocity model is correct, the images at different offsets are identical to each other. The establishment of speed model is a typical iterative process, and requires a large number of prestack depth migration operations.