Slowness (seismology)

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

${\displaystyle \Gamma =\sum _{i=1}^{N}s_{i}\Delta x_{i}}$

Therefore, the residual travel time is due to departures in slowness experienced by the wave along the raypath.