If we put in a time function, we can charactize the wavelength as
it travels through the earth with
where f is the frequency and v is the velocity.
In practical terms, this says that our input is a time function
that travels in a
given interval as a function of the media's velocity, and that
different frequencies will travel at different velocities.
What is important is that we adequately sample the wavelet.
As a result, we can take large depth steps at large velocities
and small frequencies. Our migration cost is then generally concentrated
at higher frequencies and shallower depths.
Stanford Exploration Project