No seismic recordings: By its very nature, an explosive device powerful enough to cut through the structural steel of a 110-story building is also going to create powerful ground vibrations. The demolitions company, Protec, had several portable field seismographs in the vicinity at the time of the collapses. Protec notes that these seismographs did not detect any spikes consistent with explosive blasts. A true demolition would have produced several such spikes; therefore, there was no demolition.
Take a look at the seismic record from the Lamont Doherty Earth Observatory. LDEO says that the first seismic event, which they assumed was the first plane hitting WTC1, happened at 08:46:26, and the second, which they assumed was the second plane hitting WTC2, happened at 9:02:54.
ldeo dot columbia dot edu/LCSN/Eq/20010911_wtc dot html (sorry, but they won't let me post URLs yet, as I'm still a newbie)
Now consider what the 9/11 commission said: the first plane hit WTC1 at 8:46:40, while the second hit WTC2 at 9:03:11.
9/11 Commission Report, at 32.
A couple of things to point out. First, the Commission got its times from FAA ATC radar, while LDEO’s data was self-generated, but in both cases, the time stamps represent UTC synchronization through the world atomic clock. Now, compare: LDEO says the first seismic event occurred at 8:46:26, which was fourteen seconds before the time the FAA, per the Commission, said it happened. The second seismic event, according to LDEO, occurred at 9:02:54, while FAA and the 9/11 Commission say no, it happened seventeen seconds later, at 9:03:11. Unless you think that the Commission or LDEO somehow made a typo--not that you would--don't LDEO's times indicate a pretty noisy event occurring much earlier than the planes striking WTC1 and WTC2?