基于P＋S波震源的弹性波叠前逆时偏移方法

基于弹性波动方程，推导了二维非均匀介质条件下纵横波解耦且无转换波的一阶速度一应力弹性波方程，使得弹性波在延拓过程中实现矢量偏移保证偏移质量，且不产生其他类型的转换干扰波。从激发时间成像条件以及反射系数理论出发，并与纵横波解耦且无转换波的一阶速度一应力弹性波方程结合，给出了适用于P＋s波震源模拟数据的成像条件以及偏移方法。文中给出了两个典型模型的理论记录的偏移结果，试验表明，笔者提出的方法能够对P＋s波震源的产生的波场准确归位，提高资料处理精度。

THE REVERSE-TIME MIGRATION METHOD FOR PRE-STACK ELASTIC WAVE BASED ON A COMBINED P+S SOURCE

Based on elastic wave equation, the authors deduced first-order velocity-stress elastic wave-equation with decoupling of com- pressional wave and shear wave and no converted wave under the condition of two-dimensional inhomogeneous media, which could not only make the implementation of vector migration and ensure the quality of migration, but also avoid the production of other kinds of converted interference wave. Starting from theories of exciting time image condition and reflection coefficient, in combination with first- order velocity-stress elastic wave-equation characterized by decoupling of compressional wave and shear wave and no converted wave, the authors put forward the image condition and migration method suitable for simulated data based on a combined P ＋ S source. This paper has provided the theoretic record migration results of two typical models, and tests show that the method proposed in this paper can make the wavefiled produced by a combined P ＋ S source return to the position accurately, and improve the processing precision of information.