There are few "trusted members" on ATS, and "TrueAmerican" is not one, or at least shouldn't be. Posting lots of b.s. doesn't make it not b.s.
That thread is so full of mindless hysteria, I've just skimmed and don't know where to begin or if I even should.
Is there any truth to what is in this thread?
In short, no.
People are showing graphs of seismo activity near Yellowstone
There's seismic activity in the Yellowstone region all the time, sometimes multiple times per day. You can track everything going on there:
http://www.seis.utah.edu/req2webdir/recenteqs/Maps/Yellowstone.html
http://www.seis.utah.edu/req2webdir/recenteqs/Maps/anss_imw.html
http://www.quake.utah.edu/helicorder/yell_webi.htm
The people posting and commenting on those graphs have no idea what they're talking about. There's nothing unusual to report. I can only chuckle at TrueAmerican's sudden hostility when he is asked to cite the source of his information and back up his hysterical claims.
Edit: I should add that the seismograms are essentially raw data, and just because you see activity doesn't mean there was a quake.
Could the Japan earthquake trigger Yellowstone?
I don't know what you mean by "trigger Yellowstone." Yellowstone erupts and has earthquakes every day, whether there's a big one on the other side of the world or not. If you're asking whether a big one in Japan can trigger a big one in Yellowstone, I'd say that's pretty unlikely. Even if it could, there's no sign that any such thing is happening right now.