1.
n. [Geophysics]
The rate at which a
seismic wave travels through a medium, that is, distance divided by
traveltime. Seismic velocity can be determined from vertical seismic profiles or from
velocity analysis of seismic data. It can vary vertically, laterally and azimuthally in
anisotropic media and tends to increase with depth in the Earth because
compaction reduces
porosity. Velocity also varies as a function of how it is derived from the data. For example, the
stacking velocity derived from
normal moveout measurements of common
depth point gathers differs from the
average velocity measured vertically from a check-shot or
vertical seismic profile (
VSP). Velocity would be the same only in a constant-velocity (
homogeneous) medium.