- ...time
- Fermat's principle is actually the weaker condition that
the traveltime integral is
*stationary*with respect to variations in the ray path. But, for traveltime inversion using measured first arrivals, it follows that the traveltimes must actually be minima.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5/15/2001