It helps to visualize the various seismic waves that propagate in
the body and on the surface of the earth. To this end, I refer you to
web site

http://www.daleh.id.au/seismic_theory.html.

There,  you will find instructive animations of P, S, Love, and
Rayleigh waves. These animations are borrowed from Lawrence W. Braile,
Professor, Department of Earth and AtmosphericSciences, Purdue
University, West Lafayette, Indiana. No doubt they appear on his
website as well.

 http://web.ics.purdue.edu/~braile/

  You will see that the particle motions of the surface waves (Love
and Rayleigh, do indeed decrease with depth. The shorter the period
the greater the rate of attenuation. Borehole seismometers take
advantage of this decrease with depth to reduce the sensed amplitude
of microseisms and cultural noise.

Bob
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