两种不同求和路径的叠前时间偏移方法

介绍了等效偏移距偏移和非成像炮集偏移的基本原理，二者都是用一个新的偏移距变量代替常规的偏移距，然后对以新的偏移距变量定义的旅行时双曲线进行动校正和叠加，从而实现叠前时间偏移。叠前时间偏移是对双平方根方程定义的旅行时曲面的绕射求和，而这两种方法的区别就在于其在该曲面上定义的求和路径不同。在金属矿勘探中，金属矿脉由于其成因受构造剧烈运动等因素的影响，往往倾角陡，规模小，大多呈非水平层分布，而这两种方法可以为金属矿成像提供较好的成像方法。

TWO PRESTACK TIME MIGRATION METHODS OF DIFFERENT SUMMATION PATHS

This paper describes the basic principle of Equivalent Offset Migration and Non-imaging Shot-record Migration.They both replace the usual offset coordinate with a new offset variable.The result of prestack time migration is followed by NMO and stack over the hyperbolic traveltime curve defined by the new offset variable.It is realized that prestack time migration is diffraction summation over the traveltime surface described by the double square root equation.The difference between the two methods is that they define different summation paths over the traveltime surface.The two methods can used to seismic imaging in the metal ores exploration.