FAST CALCULATION OF CONVERTED WAVE TRAVELTIME IN 3-D COMPLEX MEDIA
三维复杂介质中转换波走时快速计算

It is one of important subjects of multiwave exploration seismology to calculate traveltimes of converted waves in complex media.This paper puts forward an improved minimum traveltime tree algorithm for fast calculation of traveltimes of converted waves in 3-D complex media, which is based on Huygens' principle and Fermat's principle.First,we improve the basic minimum traveltime tree algorithm for first-break waves in order to speed calculation of 3-D converted wave traveltimes.Second,we extend the improved algorithm for first-break waves to converted waves by separating converted waves into downward and upward traveling waves and tracing them, respectively.The numerical example shows that the method preseated in this paper for calculating converted wave traveltimes is fast and robust,and can be applied to practical multiwave seismic exploration.