USGS monitors make it impossible to learn new science about the mechanisms of earthquakes and volcanic activity.
These "new" seismograms of theirs show 220% less detail than the old ones did.

So you can really forget about seeing harmonic tremors on them now.

http://isthisthingon.org/Yellowstone/keep-calm.php
http://quake.utah.edu/monitoring-research/station-map
http://isthisthingon.org/Yellowstone/daythumbs.php