Slowness (s) is a quantity introduced in Seismology which is the reciprocal of velocity. Thus travel time of a wave is the distance that the wave travels times the slowness of the medium (in seismology, it refers to different layers of Earth exhibiting different densities)Thus,
Slowness = 1/Velocity
If we divide the path followed by the ray into N segments numbered i = 1, 2 .. N the total travel time of the wave is
\Gamma=
N | |
\sum | |
i=1 |
si\Deltaxi
Therefore, the residual travel time is due to departures in slowness experienced by the wave along the raypath.
See main article: Sonic logging. Measurements of interval transit time, designated
{\Delta}t