有限差分法射线追踪

Finite-difference ray tracing.

以往使用的求取地震波初至时间的射线追踪法具有不同程度的缺陷,因而在实际应用中存在一定的局限性。本文提出一种将局部算法与扫描算法相结合的、用有限差分解程函方程求取地震波初至时间的方法。方法中考虑了散射波、首波及透射波的存在,因而可以适用于较复杂的速度模型。在求出初至时间后,利用互易性原理,能准确地得到射线路径。理论模型的试算表明,该方法计算精度较高,适宜地震偏移、层析成像以及 Green 函数的计算。

Usual ray tracing methods for obtaining wave arrival times are imperfect in dif ferent degrees ,so they all have limitations in practical use.A new technique is given here,which combines partial algorithm with scanning algorithm and obtains wave arrival times by solving eikonal equation with the use of finite difference method. This technique considers the existence of scattering wave,head wave and transmit- ted wave,so that it is suitable to complicated velocity model.After wave arrival times are obtained,ray paths can be known by applying reciprocal principle.Theo- retical model trial shows that this technique applies to seismic migration,tomogra- phy and the calculation of Green's function,with high accuracy.