引言 只要有精确的侧向速度变化规律,叠前深度偏移就能给出地下反射层图像。然而,若要用叠前深度偏移给出精确的构造图像,必须要建立精确的速度模型。建立的这种速度模型应该是一个数据库,并且各偏移距要保持一致,也就是说,如果速度模型是正确的话,来自不同偏移距的图像必须保持一致。建立速度模型是一个典型的迭代过程,并且需要掌握大量的有关叠前深度偏移的计算技术。 将积分射线偏移技术用于叠前深度偏移,我们就能有效地建立一个速度模型,它可以产生各偏移一致的图像。射线偏移确定速度界面,共中心点道集深度偏移确定速度的精度。这种联合要比单独用叠前深度偏移更有效地逼进迭代模型。 当地下介质横向速度变化非常大时,用时间偏移会使地下图像失真,这是因为它没有考虑 INTRODUCTION Prestack depth migration gives an image of the subsurface reflector as long as there is an accurate law of lateral velocity variation. However, to give a precise constructional image with pre-stack depth migration, an accurate velocity model has to be established. The speed model that is created should be a database with the same offset, which means the images from different offsets must be consistent if the speed model is correct. The establishment of speed model is a typical iterative process, and need to master a large number of pre-stack depth migration calculation techniques. Using the integral ray migration technique for prestack depth migration, we can effectively create a velocity model that produces images with uniform offsets. The ray offset determines the velocity interface, and the center point gathers the depth offset of the gathers to determine the accuracy of the velocity. This combination is more efficient than iterative modeling of the iterative model with prestack depth migration alone. When the local media lateral velocity changes very large, using the time offset will distort the underground image, because it does not consider