Demolition 1

Ground shaking

Oral reports of ground shaking before collapse

Brian Becker — Lieutenant (F.D.N.Y.) [Engine 28] We felt — our whole building that we were in, when World Trade Center 2 collapsed, that was the first one to collapse. We were in World Trade Center 1. It was a tremendous explosion and tremendous shaking of our building. We thought it was our building maybe collapsed, there was a collapse above us occurring. It was tremendous shaking and like everybody dove into this stairwell and waited for, I guess, 20, 30 seconds until it settled, and that was our experience of the other building collapsing.

Interview, 10/09/01, New York Times

Michael Beehler — Firefighter (F.D.N.Y.) [Ladder 110] I was by I guess the outer part of the building and I just remember feeling the building starting to shake and this tremendous tremendous like roar and I just — I kind of didn’t even notice it, but like out of the corner of my eye, I saw out of the building, I saw a shadow coming down. At that point I thought it was the upper part of the north tower that had just basically like toppled over, fell off. I didn’t actually see the building part go by me, because I think I was on the opposite side. But I just remember feeling this tremendous tremendous shake and hearing this, like, noise. Again I can’t describe. What I did was I ended up running out.

Interview, 12/17/01, New York Times

Jody Bell — E.M.T. (E.M.S.) I lost track of time. You start to hear this rumble. You hear this rumble. Everything is shaking. Now I’m like, what the hell could that be. I’m thinking we’re going to get bombed. This is an air raid. You hear this thunder, this rumbling. Then you see the building start to come down. Everybody’s like, “Run for your lives! The building is coming down!” At that moment when that building was coming down, I was strapping a patient onto a stair chair.

Interview, 12/15/01, New York Times

David Blacksberg — E.M.T. (E.M.S.) I lost track of time of when the second building was coming down. It sounded like one big rumble, and then it just sounded like it just continued, and I was — I wasn’t really paying attention. I was looking at the sound.

Interview, 11/23/01, New York Times

Nicholas Borrillo — Firefighter (F.D.N.Y.)on 23rd floor of North Tower:
Then we heard a rumble. We heard it and we felt the whole building shake. It was like being on a train, being in an earthquake. A train is more like it, because with the train you hear the rumbling, and it kind of like moved you around in the hall. Then it just stopped after eight or ten seconds, about the time it took for the building to come down.

Interview, 01/09/02, New York Times

Peter Cachia — (E.M.S.) [Battalion 4] I was like a little too close to the tower when it started coming down, because when I started running, I knew I was too close and I really didn’t think I was going to get out of there. So about halfway up Liberty Street I saw a truck, I guess an SUV. It wasn’t a police or a fire vehicle. It was just a car that was parked there. I went under the truck while the tower came down and the ground was shaking and the truck was shaking and I thought that was it for me. I thought I was done. I stayed under there until I guess everything was over.

Interview, 10/15/01, New York Times

Paul Curran — Fire Patrolman (F.D.N.Y.)North Tower:
I went back and stood right in front of Eight World Trade Center right by the customs house, and the north tower was set right next to it. Not that much time went by, and 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.

Interview, 12/18/01, New York Times

Timothy Julian — Firefighter (F.D.N.Y.) [Ladder 118] You know, and I just heard like an explosion and then cracking type of noise, and then it sounded like a freight train, rumbling and picking up speed, and I remember I looked up, and I saw it coming down.
I made it right to the corner, and there’s a column right there, and I was with my guys. We all made it to like the column, and I remember it was plate glass behind me, and I’m thinking I’m going to get hit by this glass and like a porcupine. I’m going to get it, you know, but nonetheless, it rumbled.
It was the loudest rumbling I ever heard. The ground shook, and I got thrown down, and I remember it just got black, and I got knocked down. I remember geing buried.

Interview, 12/26/01, New York Times

Bradley Mann — Lieutenant (E.M.S.) 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. People started running.

Interview, 11/07/01, New York Times

Keith Murphy — (F.D.N.Y.) [Engine 47] At the time, I would have said they sounded like bombs, but it was boom boom boom and then the lights all go out. I hear someone say oh, s___, that was just for the lights out. I would say about 3, 4 seconds, all of a sudden this tremendous roar. It sounded like being in a tunnel with the train coming at you. It sounded like nothing I had ever heard in my life, but it didn’t sound good. All of a sudden I could feel the floor started to shake and sway. We were being thrown like literally off our feet, side to side, getting banged around and then a tremendous wind starting to happen. It probably lasted maybe 15 seconds, 10 to 15 seconds. It seemed like a hurricane force wind. It would blow you off your feet and smoke and debris and more things started falling.

Interview, 12/05/01, New York Times

Project Plowshare

Figure 6. Project Plowshare sought to use peaceful nuclear explosions for civil engineering purposes. One proposal envisioned the nuclear excavation of a new Atlantic–Pacific canal in Central America. Some of the routes considered are shown in this map.

Plowshare and the quest for peaceful nuclear explosions became one of Livermore’s major programs in the 1960s. Initially, the program focused on large-scale earth-moving, or nuclear excavation, with the long-term goal of using nuclear explosions to excavate a new Atlantic-Pacific canal through Central America (Figure 6).




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AVIRIS image from September 16, 2001. Hot spots show as orange and yellow areas. Yellow is hotter than red (because of color mixing in the way the 3-color image was produced).

Thermal hot spots (below) detected by satellite on September 16, 2001. Red and orange indicate the hottest locations. The World Trade Center Twin Towers footprint is in the lower center and the center of World Trade Center Building 7 is in the upper right. [Source: USGS]


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Index for the locations of some of the hot spots observed on September 16, 2001.

Initial analysis of these data revealed a number of thermal hot spots on September 16 in the region where the buildings collapsed 5 days earlier. Analysis of the data indicates temperatures greater than 800oF. Over 3 dozen hot spots appear in the core zone.


ABOVE: Thermal map of the WTC

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Geometrically rectified image of the WTC core region showing hot spot locations.


Avoiding the Voids

RICH GARLOCK: Some craters had been located; others were not. If you were on top of debris, it could be compact 70 feet down, or it could be a shallow shelf masking a crater beneath. Here, I’m standing three levels down on intact structure, near the area of the Secret Service parking lot. To the right, you can see light shining through an open crater. However, looking to the left, the hole is hidden by intact structure overhead. When we saw voids like these, we would go straight to the foreman and say, you have got to yellow off this area, you can’t send machines in here.”

Crater – Bathtub


Ground level explosion

“We start walking back there and then I heard a ground level explosion and I’m like holy shit, and then you heard that twisting metal wreckage again.”

James McKinley — E.M.T. (E.M.S.)

Giant fireball explodes in street

When the rescue team reached an area directly in front of Tower Two, Antonio said he’d take over the equipment cart Will had pushed from Building 5. … The team moved ahead. … Suddenly the hallway began to shudder as a terrible deafening roar swept over them. That’s when Will saw the giant fireball explode in the street.

Fireball and loud noise

As Ron DiFrancesco ran away [from WTC 2] he was hit by a fireball … he was probably the last person out alive. “I saw the fireball and heard a loud noise. That’s all I remember…”

VIDEO: Wtc2_fireball Dailymotion

“It exploded up, a giant rolling ball of flame”

“All of a sudden I heard a roar and I saw one of the towers blow … I saw from street level as though it exploded up, a giant rolling ball of flame…”

VIDEO: Dailymotion

Gigantic fireball

Same reporter: “I hear simultaneously this roar and see what appears to be a gigantic fireball rising up at ground level . . . I remember seeing this giant ball of fire come out of the earth as I heard this roar”

Running Toward Danger: Stories Behind the Breaking News of 9/11 – P 239

Smoke shooting up stairway

Survivor in WTC 1 stairwell during WTC 2 collapse: “…and all of a sudden this huge cloud of dark grey smoke comes shooting up the stairway … and it was hot – very, very hot.”

VIDEO: Wtc1_stairway_hot Dailymotion

White smoke

White smoke emerging from the dust cloud of the collapsing WTC 2.

VIDEO: Wtc2_smoke Dailymotion

Glass missiles

“I was standing next to 1 World Trade Center and then all of a sudden I heard rumbling and we all started running away from it. The glass like blew out and threw me onto the sidewalk … and I couldn’t see for like twenty seconds…”

VIDEO: Dailymotion

Smoke rising from WTC wreckage

Video of smoke rising from the World Trade Center wreckage.

VIDEO: Wtc_smoke Dailymotion

Comment: The smoke rising from the wreckage should have been black, not white.

Secondary explosion

White smoke at the base of WTC 1 seconds before its collapse

Video with zoom:

VIDEO: Wtc1_street_level_smoke  Dailymotion

Video without zoom:

VIDEO: 911.wtc1.demolition.nj.1  Dailymotion

Map of damage to buildings

1. 3 World Financial Center/American Express Building (Overpressure 5 psi)

Structural damage from flying missiles from WTC.

2. Winter Garden Atrium (Overpressure 5 psi)

Structural damage from flying missile damage. East end was completely destroyed.

3. 2 World Financial Center (Overpressure 5 psi)

Flying missile damage – chipped stone, broken glass.

4. 90 West Street (Overpressure 5 psi)

Structural damage on north face

5. 130 Liberty Street/Bankers Trust (Overpressure 5 psi)

Structural damage by flying missiles

6. One Liberty Plaza (Overpressure 2 psi)

54-story building was undamaged structurally. Extensive glass damage.

7. Century 21 (Overpressure 2 psi)

Undamaged structurally. Extensive glass damage.

8. Millennium Hilton (Overpressure 2 psi)

Undamaged structurally. Extensive glass damage.

9. World Trade Center 4 (Overpressure 10 psi)

Partial collapse.

10. World Trade Center 3 (Overpressure 20 psi)

Building destroyed.

11. World Trade Center 5 (Overpressure 5 – 10 psi) and World Trade Center 6 (Overpressure 5 – 10 psi)

World Trade Center 5 (Overpressure 5 – 10 psi)
– Almost complete collapse.

World Trade Center 6 (Overpressure 5 – 10 psi)
– Partial (almost complete) collapse.

13. 140 West Street/Verizon Building (Overpressure 5 psi)

Structural damage.

14. Fiterman Hall (Overpressure 5 psi)

Structural damage.

15. Federal Office Building and Post Office (Overpressure 2 psi)

Window damage. (Structural damage unrelated to collapses of WTC 1 and 2 – sustained when plane’s landing gear landed on roof.)

16. World Trade Center 7 (Overpressure 2 – 5 psi)

Damage to parapet wall after collapse of WTC 2. WTC 7 collapsed from causes unrelated to WTC 1 or 2 collapse; from its own preplanted explosives.

17. Saint Nicholas Church (Overpressure 10 – 20 psi)

Complete collapse.

18. The South Tower, World Trade Center 2, hypocenter (Overpressure > 30 psi) 

Complete destruction.

19. The North Tower, World Trade Center 1, hypocenter. (Overpressure > 30 psi)

Complete destruction.

Overpressure and blast damage


  • 17 psi – didn’t destroy building, 170 feet from GZ
  • 15 psi – factory building destroyed except two smokestacks, only rebars remain (1/4 mile from GZ)
  • 6.1 psi – telephone pole snapped though trolley car nearby is intact except windows are all blown out (2.27 miles)
  • 5 psi – home totally destroyed (2.65 miles)
  • 1.7 psi – identical house as the home above still standing though some damage including windows blown out
  • 4.3 psi – wood-framed house destroyed (2.84 miles)

Glaser Map of Overpressure Effects

Map of streets

Radshelters chart

Failure of overpressure-sensitive structural elements

Atomic Archive – Overpressures Damage chart

Overpressure Physical Effects
20 psi Heavily built concrete buildings are severerly damaged or demolished.
10 psi Reinforced concrete buildings are severely damaged or demolished.
Most people are killed.
3 psi Residential structures collapse.
Serious injuries are common, fatalities may occur.
3 psi Residential structures collapse.
Serious injuries are common, fatalities may occur.
1 psi Window glass shatters.
Light injuries from fragments occur.

Overpressures and injury

Overpressures and corresponding damage

1 – 2 psi
Glaser* 2 psi = Glass damage/light damage
Injuries chart 1 psi = Glass fragments causing skin lacerations
Radshelters chart 2 psi = Light damage to commercial buildings
Atomic Archive 1 psi = Window glass shatters; light injuries from fragments occur
5 psi
Glaser* 5 psi = Light housing destroyed
Injuries chart 5 psi = Eardrum failure threshold
Radshelters chart 5 psi = Moderate damage to commercial-type buildings
Atomic Archive 5 psi = Most buildings collapse; injuries are universal
Nukefix 5 psi = Home totally destroyed
10 psi
Glaser* 10 psi = Brick housing/commercial buildings destroyed
Radshelters chart 10 psi = Heavy damage to commercial-type building and equipment
Atomic Archive 10 psi = Reinforced concrete buildings are severely damaged or demolished. (Most people are killed.)
Nukefix 15 psi = Total destruction of a factory except 2 smokestacks
20 psi
Glaser* 20 psi = Reinforced concrete structures destroyed
Injuries chart 15 -20 psi = 50% eardrum failure15 psi = Lung damage threshold

30 psi = Overpressure lethality threshold

Radshelters chart 20 psi = Destruction of all except hardened facilities
Atomic Archive 20 psi = Heavily built concrete buildings are severely damaged or demolished

Patricia Ondrovic Interview with Killtown

The relevant points of her story are:

She parked in a street in front of WTC 6, she was told to park in Vesey Street. The street in front of WTC 6 is Vesey Street. Vesey was blocked between Church and West St.

She was running near West St when the black cloud hit her reducing her visibility to almost zero.

As she was running on the south side of Vesey St heading west, she passed cars on fire.

There were burning cars between her ambulance and the middle of the WTC 6 where the lobby doors were at.

Doesn’t recall feeling extreme heat.

As WTC 2 (the first tower to fall) fell down, there were explosions in WTC 6.

She got hit by a cloud shortly after being turned away from WTC 6. She was probably at the corner of West St and Vesey St.

She ran to West St Highway where there is a park area.

She remembers running across grass.

She reached the water’s edge (and only then was free of the black cloud). She then started to run north alongside West St Highway. When she was 9-10 blocks north of Vesey St on West St Highway, she found the first FDNY EMS vehicle.

She couldn’t breathe well by that point, she felt as if someone was standing on her chest.

The back door of her ambulance was facing WTC 6 (vehicles were parked back to curb).

She thinks either WTC 5 or 6 blew up. [Story is confused at this point about which building blew up.]

It was the building behind her that blew up.

One second she is trying to put the stretcher into the ambulance and the next thing she is thrown onto the ground and breaks a couple of ribs (PO: I broke a couple of ribs, but didn’t realize it till 3 days later.)[1.8 psi overpressure is the minimum for impact; most likely she experienced an overpressure of 5 psi]; she notes the ground was shaking.

“Debris was flying at me from the building I was parked in front of. Continual loud rumbling. Debris flying from every direction, everything then became covered in black and gray smoke.”

[…] She got back up and started running west up the sidewalk on Vesey Street towards West St Highway. Cars were blowing up[thermal effects] as she ran beside them.

Ron Di Francesco

His story: He escapes from the South Tower and while he is running away, he is hit by a fireball. He is probably the last person out alive. He says he saw a fireball and heard a loud noise, and that’s all he remembers. He woke up 6 days later in St Vincents.

[Overpressure he experienced is probably around 10 psi; had an impact injury and highly likely to have had a skull fracture or similar (minimum overpressure for skull fracture is 2.3 psi) – was unconscious for 6 days. At overpressures of 10 psi, there is a 50% fatality rate.]

VIDEO: Wtc2_fireball


Carol Marin



“All of a sudden I heard a roar and I saw one of the towers blow … I saw from street level as though it exploded up, a giant rolling ball of flame…” Firefighters screamed, “Run!”. She turned to run but fell [did wind blast forces knock her down – if they did then overpressure of 5 psi]. She was scooped by someone and they ran. The man slammed her into a wall and covered her with his body. She thought she was going to die. After the fireball there was a storm of debris. The smoke was so thick she couldn’t see her hand held up in front of her. She was struck by the fact that there were not many wounded people by the time she made it to safety ; she believes the reason is that the people behind her perished.

Percentages of Population Killed

(as a function of peak overpressure) [name of chart]

Source: NRDC, The US Nuclear Plan: A Time for Change, 2001.

Original source: OTA, The Effects of Nuclear War, 1979.

[Glaser PDF]

This chart explains why there were so few injured people witnessed by Carol Marin once she made it to safety. She was at the border zone between overpressures. At this point, overpressures suddenly jump. It seems she was standing in front of WTC 2 when it exploded, outside of the building. The walls of the tower contained the explosion and reduced the overpressure that would be experienced outside its walls. Most of the people behind her were inside the WTC 2 building or standing at the perimeter close to the entrance. They would have experienced overpressures greater than 12. 98% of people who are in this category die. Outside the walls, the overpressures drop significantly, and also a person scooped her up when she fell and took her away from the tower and then shielded her with his body with her pressed up against a wall. These actions all reduced her chances of injury. Furthermore, other tall buildings in the vicinity also acted to shield the blast effects of the explosion.

Lacerations from flying glass with WTC 2 collapse

“I was standing next to 1 World Trade Center and then all of a sudden I heard rumbling and we all started running away from it [talking about WTC 2 collapse]. The glass like blew out and threw me onto the sidewalk [Impact injury – minumum overpressure of at least 1.8 psi, probably experienced overpressure of 5 psi] … and I couldn’t see for like twenty seconds…” [possibly concussion as loss of vision for 20 seconds – impact head injury].



Adapted map from:

Please click on image to view large file.


Overpressures of the two maps, one derived from assessing building damage and the other from assessing injuries, accord very well with each other.