**1. n. []**

In geophysics, the velocity of a wavefront in a certain direction, typically measured along a line of receivers and symbolized by *v _{a}*. Apparent velocity and velocity are related by the cosine of the angle at which the wavefront approaches the receivers:

*v _{a}* =

where

*v _{a}* = apparent velocity

θ = angle at which a wavefront approaches the geophone array.