A simple and efficient method is proposed for calculating first arrival traveltime based on Huygens' principle,and applied to seismic traveltime tomography.The result shows the new method is faster than Dijkstra's algorithm.

The reconstruction of seismic wave-speed distribution is nonlinear. Seismic ray path is calculated by using a model of the square of slowness. A parameterization of the model based on first order B-splines provides nonnegative matrix of the linear systems. In order to improve the solution stability, a damped, and weighted least-square procedure is proposed for considering the priori information of ray distribution. It gives numerical modelling examples as well.