http://911stories.googlepages.com/comparisonofwitnessaccountstorodriguezst2"A powerful shock wave quickly radiated up and down from the impact zone. The wave bounced from the top to the bottom of the tower, three or four seconds one way and then back, rocking the building like a huge boat in a storm.
"We got to get the hell out of here," yelled Greg Shark, an American Bureau of Shipping engineer and architect, who was bracing himself in the swaying while he stood outside Mr. McIntyre's office."
Another:
"The explosion sends the tower shaking furiously, lurching back and forth with sickening vengeance for maybe five or ten seconds. I think we may die. The building may topple over, or crumble. Finally it stops. The building is still standing. Everybody stares at each other, no idea of what happened or what to say. Speculations about an explosion, a bomb. No, it was a plane, our boss says. A commercial jet."
Another:
"After the plane collided with Tower One, it then exploded. The explosion seemed to have come about 10 seconds after impact. However, things were in slow motion and my mind was now in overdrive. I’m sure the explosion happened right after impact. The explosion was massive it only magnified the rumbling, swaying and shaking of the Tower, things began falling off my desk."
Another:
"On September 11, 2001, at about 8:48 A.M., I had just signed on to my computer at the office of the Inspector, suite 7767 at One World Trade Center. At the moment that the plane crashed into Building One, there were two rapid explosions, most likely the plane slamming into the building and the subsequent fuel explosion. The concussive shock knocked me from my seat onto the floor. When I rose to my feet, the building was rocking like a boat at sea."
Another:
I was nearly knocked to the floor by the impact of the first plane, which slammed into the north side of Tower One more than 20 floors above me. I heard a loud thud, followed by an explosion. The building felt like it swayed about 10 feet to the south. It shuddered back to the north, then shimmied back and forth.
Another:
"At 08:48, as I was sitting in my chair, I felt a tremendous jolt. My office chair rolled in one direction and then the opposite direction. During the sway, I could hear the grinding of concrete and steel.
A second jolt hit as I was standing on the ramp leading down to the reception area. Again, the building leaned one way and sprang back the next. This was also accompanied by the sound of an explosion."
Another:
"The whole building began to sway about six of seven feet each way. It was like being rocked around in a boat."
Another:
"I remember this so clearly. It started as a rumble in our seats, and then grew into vibrations from the ceiling to the floor. It moved the building so much that our desk drawers popped open. We all stood up immediately, but couldn't move. The building was shaking from side to side, and we froze just to keep our balance."
And that was just accounts from people in the North Tower.
Maybe you should get more specific in your factfinding missions.