Here's another link to an article re seismic waves produced by nuclear and natural causes. Looks like you guys are right on.
http://www.llnl.gov/str/Walter.html
There are literally hundreds of monitoring stations around the world that pick up seismic waves from all sources. One of the primary purposes of the monitoring is keep track of nuclear explosions, which produce a wave pattern that is easily distinguishable from the waves produced by earthquakes and other non-nuclear sources. If we detonated a hostile nuke underwater off the east coast on or about July 15, 2004 as NEIN claims, then literally hundreds, if not thousands of people around the world are keeping mum, even though this would be one of the biggest news events in the history of mankind, which makes no sense whatsoever given that many of these people "in the know" would be associated with leftest colleges and universities and foreign governments over which we have no control.
these are the real smart guys, not me. However, the article's comparison between the two doubles my certainity that the PAL seismograph was that of an earthquake and not an explosion. Good find.