Some witnesses near the World Trade Center feel the ground shaking just before the South Tower starts to collapse: 
EMT Joseph Fortis is heading across West Street, when, he says, “the ground started shaking like a train was coming.” He then looks up and sees the South Tower starting to collapse. [City of New York, 11/9/2001] Lonnie Penn, another EMT, is outside the Marriott Hotel, which is adjacent to the North Tower. He and his partner “felt the ground shake. You could see the towers sway and then it just came down.” [City of New York, 11/9/2001] Bradley Mann is at the EMS staging area on Vesey Street. He says, “Shortly before the first tower came down I remember feeling the ground shaking. I heard a terrible noise, and then debris just started flying everywhere.” [City of New York, 11/7/2001] Battalion Chief Brian O’Flaherty is walking into the lobby of the Marriott Hotel. He says, “I hear a noise. Right after that noise, you could feel the building start to shudder, tremble, under your feet.” He then hears the “terrible noise” of the South Tower collapsing. [City of New York, 1/9/2002] Witnesses will also notice the ground shaking before the North Tower collapses (see Shortly Before 10:28 a.m. September 11, 2001).
Shortly Before 10:28 a.m. September 11, 2001: Ground Shakes Prior to North Tower Collapse
Some witnesses feel the ground shaking just before the north WTC tower starts collapsing: Fire Patrolman Paul Curran is in front of the US Customs House (WTC 6), next to the North Tower. He says, “all of a sudden the ground just started shaking. It felt like a train was running under my feet.… The next thing we know, we look up and the tower is collapsing.” [City of New York, 12/18/2001] EMS Lieutenant Bradley Mann is heading toward the EMS staging area on Vesey Street. He’d felt the ground shaking prior to the first collapse (see Shortly Before 9:59 a.m. September 11, 2001). He says, “The ground shook again, and we heard another terrible noise and the next thing we knew the second tower was coming down.” [City of New York, 11/7/2001] Jay Jonas is actually inside the North Tower, on its fourth floor. Seconds before the collapse he feels “a tremendous vibration and shaking; the floor began waving.” [Providence Journal, 9/11/2002]
