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Tuesday, April 20, 2010

911-WTC 7 Collapse Foreknowledge


WTC 7 Collapse Foreknowledge

Reports of Foreknowledge of the Collapse of Building 7 in the Oral Histories

The oral histories released on August 12, 2005 contain many reports of warnings of the collapse of WTC Building 7 at various times during the day. Most of the warnings were from after about 4 PM.

Joseph Cahill -- Paramedic (E.M.S.)
The reason we were given for why we were moving was that 7 World Trade Center was going to collapse or was at risk of collapsing. So we must have been somewhere in this area where we would have had a problem with that. But I honestly don't remember.
...
They wanted us to move the treatment sector because of 7 World Trade Center was imminently to collapse, which, of course, it did.
Interview, 10/15/2001, New York Times

Tiernach Cassidy -- Firefighter (F.D.N.Y.), Engine 3
Then, like I said, building seven was in eminent collapse. They blew the horns. They said everyone clear the area until we got that last civilian out. We tried to give another quick search while we could, but then they wouldn't let us stay anymore. So we cleared the area. ... So yeah, then we just stayed on Vesey until building seven came down.
Interview, 12/30/2001, New York Times

Pete Castellano -- Firefighter (F.D.N.Y.), Ladder 149
We were ordered down from the tower ladder because of a possible collapse at Tower 7.
Interview, 12/28/2001, New York Times

Jason Charles -- E.M.T. (E.M.S.), Battalion 13
So we started heading over to where Building 7 was at and they were like Building 7 is going to collapse, you can't go over there, this and that, and there was another building that they thought was going to collapse that was like right behind the triage center, the building that we were in.
Interview, 1/23/2002, New York Times

Frank Congiusta -- Battalion Fire Chief (F.D.N.Y.)
While we were searching the subbasements, they decided that Seven World Trade Center, which was across the street, was going to collapse. So they called us out.
...
When I came out, they were calling us on the radio to tell us to get out. Then I reported that the search was negative, and then they wouldn't let anybody near the site pretty much, because Seven World Trade Center was going to come down.
Interview, 1/8/2002, New York Times

Louis Cook -- Paramedic (E.M.S.)
We got to Chambers and Greenwich, and the chief turns around and says, 'There's number Seven World Trade. That's the OEM bunker.' We had a snicker about that. We looked over, and it's engulfed in flames and starting to collapse.
...
We hear over the fire portable, 'Everybody evacuate the site. It's going to collapse.' Mark Steffens starts yelling, 'Get out of here! Get out of here! Get out of here! We've got to go! We've got to go! It's going to collapse.'
...
We pulled the car over, turned around and just watched it pancake.
Interview, 10/17/2001, New York Times

Frank Cruthers -- Fire Chief (F.D.N.Y.)
Early on, there was concern that 7 World Trade Center might have been both impacted by the collapsing tower and had several fires in it and there was a concern that it might collapse. So we instructed that a collapse area --
...
-- be set up and maintained so that when the expected collapse of 7 happened, we wouldn't have people working in it. Thre was considerable discussion with Con Ed regarding the substation in that building and the feeders and the oil coolands and so on. And their concern was of the type of fire we might have when it collapsed.
Interview, 10/31/2001, New York Times

Roy David -- Fire Lieutenant (F.D.N.Y.), Battalion 8
At Pace University we had -- we set up -- I'm sorry, we set up in that lobby of that building, the lobby and the actual whole first floor. There was a threat of collapse of building number seven, so 225, we had to evacuate it.
Interview, 10/12/2001, New York Times

Frank Fellini -- Fire Chief (F.D.N.Y.)
The major concern at that time at that particular location was number Seven, building number seven, which had taken a big hit from the north tower. When it fell, it ripped steel out from between the third and sixth floors across the facade on Vesey Street. We were concerned that the fires on several floors and the missing steel would result in the building collapsing.
So for the next five or six hours we kept firefighters from working anywhere near that building, which included the whole north side of the World Trade Center complex. Eventually around 5:00 or a little after, building number seven came down.
Interview, 12/3/2001, New York Times

Brian Fitzpatrick -- Firefighter (F.D.N.Y.), Ladder 22
We were then positioned on Vesey Street between North End and the West Side Highway because there was an imminent collapse on 7 World Trade, and it did collapse.
Interview, 12/6/2001, New York Times

Joseph Fortis -- E.M.T (E.M.S.), Battalion 13
When the third building came down, we were on that corner in front of the school, and everybody just stood back. They pulled us all back at the time, almost about an hour before it, because they were sure -- they knew it was going to come down, but they weren't sure. So they pulled everyone back, and everybody stood there and we actually just waited and just waited and waited until it went down, because it was unsafe.
Interview, 11/9/2001, New York Times

Ray Goldbach -- Fire Captain (F.D.N.Y.), Executive Assistant to the Fire Commissioner
There was a big discussion going on at that point about pulling all of our units out of 7 World Trade Center. Chief Nigro didn't feel it was worth taking the slightest chance of somebody else getting injured. So at that point we made a decision to take all of our units out of 7 World Trade Center because there was a potential for collapse.
...
Made the decision to back everybody away, took all the units and moved them all the way back toward North End Avenue, which is as far I guess west as you could get on Vesey Street, to keep them out of the way.
Interview, 10/24/2001, New York Times

George Holzman -- Firefighter (F.D.N.Y.), Ladder 47
We stayed there for quite sometime when I don't even know who, I think it was someone, Lieutenant Lowney spoke to, asked us to leave the area, they were concerned about 7 World Trade Center collapsing.
Interview, 1/17/2002, New York Times

Edward Kennedy -- Firefighter (F.D.N.Y.), Engine 44
That was the only Mayday that I remember, and to tell you the truth, the only guy that really stands out in my mind that I remember being on the radio was Chief Visconti.
...
I remember him screaming about 7, No. 7, that they wanted everybody away from 7 because 7 was definitely going to collapse, they don't know when, but it's definitely going to come down, just get the hell out of the way, everybody get away from it, make sure you're away from it, that's an order, you know, stuff like that.
Interview, 1/17/2002, New York Times

Matthew Long -- Firefighter (F.D.N.Y.), Ladder 43
And at that point they were worried that 7 was coming down so they were calling for everyone to back out.
So I waited for -- we waied for the boss, Lieutenant Rohan, in the middle of the rubble and we all walked out together back to the West Side Highway and pretty much hung out by the marina when 7 came down.
...
Because they were just adamant about 7 coming down immediately. I think we probably got out of that rubble and 18 minutes later is when 7 came down.
Interview, 10/9/2001, New York Times

Thomas McCarthy -- Fire Chief (F.D.N.Y.)
So when I get to the command post, they just had a flood of guys standing there. They were just waiting for 7 to come down.
...
I made it down Vesey Street to just in front of the overpass of 7 World Trade. People were saying don't stand under there, it's going to come down.
...
So at that point we were a little leery about how the bridge was tied in, so no one was really going onto it, and then they were also saying 7 was going to come down. They chased everyone off the block.
Interview, 10/11/2001, New York Times

Kevin McGovern -- Firefighter (F.D.N.Y.), Engine 53
At that time Seven World Trade Center was burning and was in danger of collapsing. After a while the lieutentant said, "Let's move, let's get out of here, let's take a break."
Actually I think at that point just as we were leaving, guys -- I don't know who it was. I guess it was a chief was saying clear the area, because they were worried about number Seven World Trade Center coming down and burying guys who were digging.
So we basically went back to the rig, because they were clearing that area out. It took about three hours for Seven World Trade Center to actually come down. So we were off to the side.
Interview, 12/11/2001, New York Times

Vincent Massa -- Firefighter (F.D.N.Y.), Engine 64
At this point Seven World Trade Center was going heavy, and they weren't letting anybody get too close. Everybody was expecting that to come down.
...
I remember later on in the day as we were waiting for seven to come down, they kept backing us up Vesey, almost like a full block. They were concerned about seven coming down, and they kept changing us, establishing a collapse zone and backing us up.
Interview, 12/4/2001, New York Times

Daniel Nigro -- Department Cheif (F.D.N.Y.)
The most important operational decision to be made that afternoon was the collapse had damaged 7 World Trade Center, which is about a 50 story building, at Vesey between West Broadway and Washington Street. It had very heavy fire on many floors and I ordered the evacuation of an area sufficient around to protect our members, so we had to give up some rescue operations that were going on at the time and back the people away far enough so that if 7 World Trade did collapse, we wouldn't lose any more people.
We continued to operate on what we could from that distance and approximately an hour and a half after that order was given, at 5:30 in the afternoon, 7 World Trade Center collapsed completely.
Interview, 10/24/2001, New York Times

Christopher Patrick Murray -- Firefighter (F.D.N.Y.), Engine 205
Probably about 4:00 o'clock, 5:00 o'clock, our radios went dead, because we heard reports all day long of 7 World Trade possibly coming down and I think at 5:30 that came down.
Interview, 12/12/2001, New York Times

William Ryan -- Fire Lieutenant (F.D.N.Y.)
Then we found out, I guess around 3:00 o'clock, that they thought 7 was going to collapse. So, of course, we've got guys all in this pile over here and the main concern was get everybody out, and I guess it took us over an hour and a half, two hours to get everybody out of there.
...
So it took us a while and we ended up backing everybody out, and that's when 7 collapsed.
Interview, 10/18/2001, New York Times

Thomas Smith -- Firefighter (F.D.N.Y.)
They backed me off the rig because seven was in dead jeopardy, so they backed everybody off and moved us to the rear end of Vesey Street. We just stood there for a half hour, 40 minutes, because seven was in imminent collapse and finally did come down.
Interview, 12/6/2001, New York Times

Robert Sohmer -- Fire Captain (F.D.N.Y.)
As the day went on they started worrying about 7 World Trade Center collapsing and they ordered an evacuation from that area so at that time, we left the area with the other companies, went back to the command post on Broadway
...
We were about to proceed our operation there and this was in the afternoon, I would say approximately maybe 2:00 roughly, where we started to operate and then they asked us to fall back again due to the potential of 7 World Trade Center collapsing.
Interview, 1/17/2002, New York Times

James Wallace -- Firefighter (F.D.N.Y.)
They were saying building seven was going to collapse, so we regrouped and went back to our rig. We went to building four or three; I don't know. We were going to set up our tower ladder there. They said no good because building seven is coming down.
Interview, 12/29/2001, New York Times

Rudolf Weindler -- Fire Lieutenant (F.D.N.Y.)
I ran into Chief Coloe from the 1st Division, Captain Varriale, Engine 24, and Captain Varriale told Chief Coloe and myself that 7 World Trade Center was badly damaged on the south side and definitely in danger of collapse. Chief Coloe said we were going to evacuate the collapse zone around 7 World Trade Center, which we did.
Interview, 1/15/2002, New York Times

Decosta Wright -- E.M.T. (E.M.S.)
They said -- we were like, are you guys going to put that fire out? I was like, you know, they are going to wait for it to burn down and it collapsed.
...
Yes, so basically they measured out how far the building was going to come, so we knew exactly where we could stand.
...
5 blocks. 5 blocks away. We still could see. Exactly right on point, the cloud just stopped right there. Then when that building was coming down, the same thing, that same rumbling.
Interview, 10/11/2001, New York Times
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911-Explosions


Explosions

Reports of Sights and Sounds of Explosions in the Oral Histories

The oral histories released on August 12, 2005 contain many recollections of the sights and sounds of explosions. The excerpts on this page describe perceptions of the South Tower collapse, except where noted otherwise.

Rich Banaciski -- Firefighter (F.D.N.Y.) [Ladder 22]
We were there I don't know, maybe 10, 15 minutes and then I just remember there was just an explosion. It seemed like on television they blow up these buildings. It seemed like it was going all the way around like a belt, all these explosions.
Interview, 12/06/01, New York Times

Brian Becker -- Firefighter (F.D.N.Y.) [Engine 28]
So I think that the building was really kind of starting to melt. We were -- like, the melt down was beginning. The collapse hadn't begun, but it was not a fire any more up there. It was like -- it was like that -- like smoke explosion on a tremendous scale going on up there.
Interview, 10/09/01, New York Times

Greg Brady -- E.M.T. (E.M.S.) [Battalion 6]
We were standing underneath and Captain Stone was speaking again. We heard -- I heard 3 loud explosions. I look up and the north tower is coming down now, 1 World Trade Center.
...
We were standing in a circle in the middle of West Street. They were talking about what was going on. At that time, when I heard the 3 loud explosions, I started running west on Vesey Street towards the water. At that time, I couldn't run fast enough. The debris caught up with me, knocked my helmet off.
Interview, , New York Times

Timothy Burke -- Firefigter (F.D.N.Y.) [Engine 202]
Then the building popped, lower than the fire, which I learned was I guess, the aviation fuel fell into the pit, and whatever floor it fell on heated up really bad and that's why it popped at that floor. That's the rumor I heard. But it seemed like I was going oh, my god, there is a secondary device because the way the building popped. I thought it was an explosion.
Interview, 01/22/02, New York Times

Ed Cachia -- Firefighter (F.D.N.Y.) [Engine 53]
It actually gave at a lower floor, not the floor where the plane hit, because we originally had thought there was like an internal detonation explosives because it went in succession, boom, boom, boom, boom, and then the tower came down. With that everybody was just stunned for a second or two, looking at the tower coming down.
Interview, 12/06/05, New York Times

Frank Campagna -- Firefighter (F.D.N.Y.) [Ladder 11]
There was nobody in the intersection, nobody in the streets in general, everyone just saying come on, keeping coming, keep coming. That's when [the North Tower] went. I looked back. You see three explosions and then the whole thing coming down. I turned my head and everybody was scattering. From there I don't know who was who. I don't even know where my guys went. None of us knew where each other were at at that point in time.
Interview, 12/04/01, New York Times

Craig Carlsen -- Firefighter (F.D.N.Y.) [Ladder 8]
I guess about three minutes later you just heard explosions coming from building two, the south tower. It seemed like it took forever, but there were about ten explosions. At the time I didn't realize what it was. We realized later after talking and finding out that it was the floors collapsing to where the plane had hit.
...
You did hear the explosions [when the North Tower came down]. Of course after the first one -- the first one was pretty much looking at in like in awe. You didn't realize that this was really happening because you kind of just stood there and you didn't react as fast as you thought you were going to. The second one coming down, you knew the explosions. Now you're very familiar with it.
Interview, 01/25/02, New York Times

Jason Charles -- E.M.T. (E.M.S.)
I grabbed her and the Lieutenant picked her up by the legs and we start walking over slowly to the curb, and then I heard an explosion from up, from up above, and I froze and I was like, oh, s___, I'm dead because I thought the debris was going to hit me in the head and that was it.
Then everybody stops and looks at the building and they they take off. The Lieutenant dropped her legs and ran. The triage center, everybody who was sitting there hurt and, oh, you know, help me, they got up and and everybody together got up and ran. I looked at them like why are they running? I look over my shoulder and I says, oh, s___, and then I turned around and looked up and that's when I saw the tower coming down.
...
North Tower:
We start walking back there and then I heard a ground level explosion and I'm like holy s___, and then you heard that twisting metal wreckage again. Then I said s___ and everybody started running and I started running behind them, and we get to the door.
Interview, 01/23/02, New York Times

Frank Cruthers -- Chief (F.D.N.Y.) [Citywide Tour Commander]
And while I was still in that immediate area, the south tower, 2 World Trade Center, there was what appeared to be at first an explosion. It appeared at the very top, simultaneously from all four sides, materials shot out horizontally. And then there seemed to be a momentary delay before you could see the beginning of the collapse.
Interview, 10/31/01, New York Times

James Curran -- Firefighter (F.D.N.Y.)
A guy started scremaing to run. When I got underneath the north bridge I looked back and you heard it, I heard like every floor went chu-chu-chu. Looked back and from the pressure everything was getting blown out of the floors before it actually collapsed.
Interview, 12/30/01, New York Times

Kevin Darnowski -- Paramedic (E.M.S.)
I started walking back up towards Vesey Street. I heard three explosions, and then we heard like groaning and grinding, and tower two started to come down.
Interview, 11/09/01, New York Times

Dominick Derubbio -- Battalion Chief (F.D.N.Y.) [Division 8]
After a while we were looking up at the tower, and all of a sudden someone said it's starting to come down.
...
This would be the first one.
...
This one here. It was weird how it started to come down. It looked like it was a timed explosion, but I guess it was just the floors starting to pancake one on top of the other.
Interview, 10/12/01, New York Times

Karin Deshore -- Captain (E.M.S.)
Somewhere around the middle of the World Trade Center, there was this orange and red flash coming out. Initially it was just one flash. Then this flash just kept popping all the way around the building and that building had started to explode. The popping sound, and with each popping sound it was initially an orange and then a red flash came out of the building and then it would just go all around the building on both sides as far as I could see. These popping sounds and the explosions were getting bigger, going both up and down and then all around the building.
Interview, 11/07/01, New York Times

Brian Dixon -- Battalion Chief (F.D.N.Y.)
I was watching the fire, watching the people jump and hearing a noise and looking up and seeing -- it actually looked -- the lowest floor of fire in the south tower actually looked like someone had planted explosives around it because the whole bottom I could see -- I could see two sides of it and the other side -- it just looked like that floor blew out. I looked up and you could actually see everything blew out on the one floor. I thought, geez, this looks like an explosion up there, it blew out. Then I guess in some sense of time we looked at it and realized, no, actually it just collapsed. That's what blew out the windows, not that there was an explosion there but that windows blew out. The realization hit that it's going to fall down, the top's coming off. I was still thinking -- there was never a thought that this whole thing is coming down. I thought that that blew out and stuff is starting to fly down. The top is going to topple off there.
Interview, 10/25/01, New York Times

Michael Donovan -- Captain (F.D.N.Y.)
Anyway, with that I was listening, and there was an incredibly loud rumbling. I never got to look up. People started running for the entrances to the parking garages. They started running for the entrances. I started running without ever looking up. The roar became tremendous. I fell on the way to the parking garages. Debris was starting to fall all around me. I got up, I got into the parking garages, was knocked down by the percussion. I thought there had been an explosion or a bomb that they had blown up there. The Vista International Hotel was my first impression, that they had blown it up. I never got to see the World Trade Center coming down.
Interview, 11/09/01, New York Times

James Drury -- Assistant Commissioner (F.D.N.Y.)
We were in the process of getting some rigs moved when I turned, as I heard a tremendous roar, explosion, and saw that the first of the two towers was starting to come down.
...
When the dust started to settle, I headed back down towards the World Trade Center and I guess I came close to arriving at the corner of Vesey and West again where we started to hear the second roar. That was the north tower now coming down. I should say that people in the street and myself included thought that the roar was so loud that the explosive - bombs were going off inside the building. Obviously we were later proved wrong.
...
The sight of the jumpers was horrible and the turning around and seeing that first tower come down was unbelieveable. The sound it made. As I said I thought the terrorists planted explosives somewhere in the building. That's how loud it was, crackling explosive, a wall. That's about it. Any questions?
Interview, 10/16/01, New York Times

Thomas Fitzpatrick -- Deputy Commissioner for Administration (F.D.N.Y.)
We looked up at the building straight up, we were that close. All we saw was a puff of smoke coming from about 2 thirds of the way up. Some people thought it was an explosion. I don't think I remember that. I remember seeing it, it looked like sparkling around one specific layer of the building. I assume now that that was either windows starting to collapse like tinsel or something. Then the building started to come down. My initial reaction was that this was exactly the way it looks when they show you those implosions on TV. I would have to say for three or four seconds anyway, maybe longer. I was just watching. It was interesting to watch, but the thing that woke everybody up was the cloud of black material. It reminded me of the 10 commandments when the green clouds come down on the street. The black cloud was coming down faster than the building, so whatever was coming down was going to hit the street and it was pretty far out. You knew it wasn't coming right down. Judging from where people were jumping before that, this cloud was much further.
Interview, 10/16/01, New York Times

Gary Gates -- Lieutenant (F.D.N.Y.)
I looked up, and the building exploded, the building that we were very close to, which was one tower. The whole top came off like a volcano.
...
So now both towers have been hit by a plane. The north tower was burning. So the explosion, what I realized later, had to be the start of the collapse. It was the way the building appeared to blowout from both sides. I'm looking at the face of it, and all we see is the two sides of the building just blowing out and coming apart like this, as I said, like the top of a volcano.
Interview, 10/12/01, New York Times

Kevin Gorman -- Firefighter (F.D.N.Y.) [Ladder 22]
North Tower:
John Malley, who was right behind me, I turned around for him, because he was doing something, either putting his coat on or something, and as I was looking at him I heard the explosion, looked up, and saw like three floors explode, saw the antenna coming down, and turned around and ran north.
Interview, 01/09/02, New York Times

Stephen Gregory -- Assistant Commissioner (F.D.N.Y.)
We both for whatever reason -- again, I don't know how valid this is with everything that was going on at that particular point in time, but for some reason I thought that when I looked in the direction of the Trade Center before it came down, before No. 2 came down, that I saw low-level flashes. In my conversation with Lieutenant Evangelista, never mentioning this to him, he questioned me and asked me if I saw low-level flashes in front of the building, and I agreed with him because I thought -- at that time I didn't know what it was. I mean, it could have been as a result of the building collapsing, things exploding, but I saw a flash flash flash and then it looked like the building came down.
...
[It was at] the lower level of the building. You know like when they demolish a building, how when they blow up a building, when it falls down? That's what I thought I saw.
...
He said did you see anything by the building? And I said what do you mean by see anything? He said did you see flashes? I said, yes, well, I thought it was just me. He said no, I saw them too.
...
I know about the explosion on the upper floors. This was like at eye level. I didn't have to go like this. Because I was looking this way. I'm not going to say it was on the first floor or the second floor, but somewhere in that area I saw to me what appeared to be flashes.
Interview, 10/03/01, New York Times

Gregg Hansson -- Lieutenant (F.D.N.Y.)
That's basically where we were. Then a large explosion took place. In my estimation that was the tower coming down, but at that time I did not know what that was. I thought some type of bomb had gone off. I was, I believe, ahead of the rest of the firefighters and officers there. I made it to the corner, and I took about four running steps this way when you could feel the rush of the wind coming at you. I believed that that was a huge fireball coming at the time.
Interview, 10/09/01, New York Times

Timothy Julian -- Firefighter (F.D.N.Y.) [Ladder 118]
We came out from 90 West, made a left, headed east, and right when we got to the corner of Washington and Albany, that's when I heard the building collapse.
First I thought it was an explosion. I thought maybe there was bomb on the plane, but delayed type of thing, you know secondary device.
...
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.
Interview, 12/26/01, New York Times

Art Lakiotes -- Chief (F.D.N.Y.) [Safety Command]
Tower one now comes down. Same thing but this time some of us take off straight down West Street, because we realized later on, subconsciously we wanted to be near buildings. We all thought it was secondary explosives or more planes or whatever.
Interview, 12/03/01, New York Times

John Malley -- Firefighter (F.D.N.Y.) [Ladder 22]
We were walking into darkness. As we walked through those revolving doors, that's when we felt the rumble. I felt the rumbling, and then I felt the force coming at me. I was like, what the hell is that? In my mind it was a bomb going off. The pressure got so great, I stepped back behind the columns separating the revolving doors. Then the force just blew past me. It blew past me it seemed for a long time. In my mind I was saying what the hell is this and when is it going to stop? Then it finally stopped, that pressure which I thought was a concussion of an explosion. It turns out it was the down pressure wind of the floors collapsing on top of each other. At that point everything went black, and then the collapse came. It just rained on top of us. Everything came. It rained debris forever.
Interview, 12/12/01, New York Times

Julio Marrero -- E.M.T. (F.D.N.Y.)
I was screaming from the top of my lungs, and I must have been about ten feet away from her and she couldn't even hear me, because the building was so loud, the explosion, that she couldn't even hear me. I just saw everybody running; and she saw us running, and she took off behind us.
Interview, 10/25/01, New York Times

Orlando Martinez -- E.M.T. (E.M.S.)
There was an explosion and after we started running, I was able to make it to Chambers and West, where I only saw one EMT, EMT Vega. She is new here. She was the only EMT I saw from the station and with all the cops and everybody else running, rescue workers. I grabbed her and I said just stay with me. We will try to get out of here.
Interview, 11/01/01, New York Times

Linda McCarthy -- E.M.T. (E.M.S.)
So when that one went down. I thought the plane was exploding, or another plane hit. I had no idea it was coming down. But I couldn't see it gone, because I couldn't see it really in the first place with all the smoke.
Interview, 11/28/01, New York Times

James McKinley -- E.M.T. (E.M.S.)
After that I heard this huge explosion, I thought it was a boiler exploding or something. Next thing you know this huge cloud of smoke is coming at us, so we're running. Everyone is, firemen, PD, everyone is running away from the World Trade Center, up Vessey Street. This is North End, we was running around Vessey and around North end to get away from the first smoke.
Interview, 10/12/01, New York Times

Joseph Meola -- Firefighter (F.D.N.Y.) [Engine 91]
As we are looking up at the building, what I saw was, it looked like the building was blowing out on all four sides. We actually heard the pops. Didn't realize it was the falling -- you know, you heard the pops of the building. You thought it was just blowing out.
Interview, 12/11/01, New York Times

Keith Murphy -- (F.D.N.Y.) []
I was standing kind of on the edge of where our elevator bank met the big elevator bank. That was when the - I determined that's when the north tower collapses. We are standing there and the first thing that happened, which I still think is strange to me, the lights went out. Completely pitch black. Since we are in that core little area of the building, there is no natural light. No nothing, I didn't see a thing.
I had heard right before the lights went out, I had heard a distant boom boom boom, sounded like three explosions. I don't know what it was. 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.
Interview, 12/05/01, New York Times

Kevin Murray -- Firefighter (F.D.N.Y.) [Ladder 18]
When the tower started -- there was a big explosion that I heard and someone screamed that it was coming down and I looked away and I saw all the windows domino -- you know, dominoeing up and then come down. We were right in front of 6, so we started running and how are you going to outrun the World Trade Center? So we threw our tools and I dove under a rig.
Interview, 10/09/01, New York Times

Janice Olszewski -- Captain (E.M.S.)
I thought more could be happening down there. I didn't know if it was an explosion. I didn't know it was a collapse at that point. I thought it was an explosion or a secondary device, a bomb, the jet -- plane exploding, whatever.
Interview, 11/07/01, New York Times

Juan Rios -- E.M.T. (E.M.S.)
I was in the back waiting, you know, so we could wait for patients and I was hooking up the regulator to the O-2, when I hear people screaming and a loud explosion, and I heard like "sssssssss..." the dust like "sssssssss..." So I come out of the bus, and I look and I see a big cloud of dust and debris coming from the glass...
Interview, 10/10/01, New York Times

Michael Ober -- E.M.T. (E.M.S.)
Then we heard a rumble, some twisting metal, we looked up in the air, and to be totally honest, at first, I don't know exactly -- but it looked to me just like an explosion. It didn't look like the building was coming down, it looked like just one floor had blown completely outside of it. I was sitting there looking at it. I just never thought they would ever come down, so I didn't think they were coming down. I just froze and stood there looking at it.
Interview, 10/16/01, New York Times

Angel Rivera -- Firefighter (F.D.N.Y.)
Mike Mullan walked one flight up, and then the most horrendous thing happened. That's when hell came down. It was like a huge, enormous explosion. I still can hear it. Everything shook. Everything went black. The wind rushed, very slowly [sound], all the dust, all the -- and everything went dark.
Interview, 01/22/02, New York Times

Daniel Rivera -- Paramedic (E.M.S.) [Battalion 31]
Then that's when -- I kept on walking close to the south tower, and that's when that building collapsed.
...
It was a frigging noise. At first I thought it was -- do you ever see professional demolition where they set the charges on certain floors and then you hear "Pop, pop, pop, pop, pop"? That's exactly what -- because I thought it was that. When I heard that frigging noise, that's when I saw the building coming down.
Interview, 10/10/01, New York Times

Kennith Rogers -- Firefighter (F.D.N.Y.)
Meanwhile we were standing there with about five companies and we were just waiting for our assignment and then there was an explosion in the south tower, which, according to this map, this exposure just blew out the flames. A lot of guys left at that point. I kept watching. Floor after floor after floor. One floor under another after another and when it hit about the fifth floor, I figured it was a bomb, because it looked like a synchronized deliberate kind of thing. I was there in '93.
Interview, 12/10/01, New York Times

Patrick Scaringello -- Lieutenant (E.M.S.)
I started to treat patients on my own when I heard the explosion from up above. I looked up, I saw smoke and flame and then I saw the top tower tilt, start to twist and lean.
...
I was assisting in pulling more people out from debris, when I heard the second tower explode. When I tried to evacuate the area, by running up Fulton, got halfway up.
Interview, 10/10/01, New York Times

Mark Steffens -- Division Chief (E.M.S.)
Then there was another it sounded like an explosion and heavy white powder, papers, flying everywhere. We sat put there for a few minutes. It kind of dissipated.
...
That's when we heard this massive explosion and I saw this thing rolling towards us. It looked like a fireball and then thick, thick black smoke.
Interview, 10/03/01, New York Times

John Sudnik -- Battalion Chief (F.D.N.Y.)
The best I can remember, we were just operating there, trying to help out and do the best we could. Then we heard a loud explosion or what sounded like a loud explosion and looked up and I saw tower two start coming down. Crazy.
Interview, 11/07/01, New York Times

Neil Sweeting -- Paramedic (E.M.S.)
You heard a big boom, it was quiet for about ten seconds. Then you could hear another one. Now I realize it was the floors starting to stack on top of each other as they were falling. It was spaced apart in the beginning, but then it got to just a tremendous roar and a rumble that I will never forget.
Interview, 11/01/01, New York Times

Jay Swithers -- Captain (E.M.S.)
At that point I looked back and most of the people who were triaged in that area with the triage tags on them got up and ran. I took a quick glance at the building and while I didn't see it falling, I saw a large section of it blasting out, which led me to believe it was just an explosion. I thought it was a secondary device, but I knew that we had to go.
...
Within a few moments, I regrouped with Bruce Medjuck and I asked him to tell them on the radio to send us MTA buses to get people out. That didn't happen. But one thing that did happen was an ambulance pulled up which was very clean. So I assumed that the vehicle had not been in the - what I thought was an explosion at the time, but was the first collapse.
Interview, 10/30/01, New York Times

David Timothy -- E.M.T. (E.M.S.)
The next thing I knew, you started hearing more explosions. I guess this is when the second tower started coming down.
Interview, 10/25/01, New York Times

Albert Turi -- Deputy Assistant Chief (F.D.N.Y.)
The next thing I heard was Pete say what the f___ is this? And as my eyes traveled up the building, and I was looking at the south tower, somewhere about halfway up, my initial reaction was there was a secondary explosion, and the entire floor area, a ring right around the building blew out. I later realized that the building had started to collapse already and this was the air being compressed and that is the floor that let go.
Interview, 10/23/01, New York Times

Thomas Turilli -- Firefighter (F.D.N.Y.)
The door closed, they went up, and it just seemed a couple of seconds and all of a sudden you just heard it, it almost actually that day sounded like bombs going off, like boom, boom, boom, like seven or eight, and then just a huge wind gust just came and my officer just actually took all of us and just threw us down on the ground and kind of just jumped on top of us, laid on top of us.
...
At that point were were kind of standing on the street and I looked to my left and actually I noticed the tower was down. I didn't even know that it was when we were in there. It just seemed like a huge explosion.
Interview, 01/17/02, New York Times

Stephen Viola -- Firefighter (F.D.N.Y.)
Our guy went in with 13 truck, and he was coming down with the guy from 13 truck to bring the elevator to us, and when he was either going up or coming down the elevator, that's when the south tower collapsed, and it sounded like a bunch of explosions. You heard like loud booms, but I guess it was all just stuff coming down, and then we got covered with rubble and dust, and I thought we'd actually fallen through the floor into like the PATH tubes, because it was so dark you couldn't see anything, and from there it was a little hazy from there on.
Interview, 01/10/02, New York Times

William Wall -- Lieutenant (F.D.N.Y.) [Engine 47]
At that time, we heard an explosion. We looked up and the building was coming down right on top of us, so we ran up West Street. We ran a little bit and then we were overtaken by the cloud and we hid behind a white Suburban.
...
Oh, when we came out of the building and we were walking across West Street when we first got out of the building, we're walking across the street and all you heard was like bombs going off above your head. You couldn't see it. It was just cloudy. And we found out later it was the military jets. That was an eerie sound. You couldn't see it and all you heard was like a "boom" and it just kept going. We couldn't see 50 feet above our head because of the dust. So we didn't know if it was bombs going off or whatever, but we didn't want to stay there.
Interview, 12/10/01, New York Times
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911-Seismic Records


Seismic Records of the Twin Towers' Destruction:

Clarifying the Relationship Between Seismic Evidence and Controlled Demolition Theories

by
Jim Hoffman 
Version 0.9, Oct. 31, 2006

Introduction

The total destruction of each of the Twin Towers produced seismic signals that were recorded by at least 5 seismic observatories within 60 miles of lower Manhattan. The published charts from the Lamont-Doherty Earth Observatory in Palisades, New York, have been cited as evidence supporting the following two claims:
  • Each Tower fell completely in 10 seconds or less
  • The largest seismic spikes preceded the fall of each Tower
Both of these claims can be found in a large cross-section of literature challenging the official story. The first claim is also accepted by many defenders of official collapse theories, and is even found in the 9/11 Commission Report . In this essay I will examine these widely-repeated claims and show that, despite their popularity, they both lack supporting evidence and are contradicted by verifiable evidence. I will, however, also show that the seismic records do support the case for controlled demolition, but in a way that has been overlooked.
I have previously addressed both claims on these pages:
In this essay I will provide a more focused and complete exposition of these issues.

Contents

Do Seismic Records Really Show that the Towers Fell in Ten Seconds?

Because the claim that the Towers fell in ten seconds has historically been uncritically repeated by defenders and detractors of the official story alike, most newer researchers have not taken the time to closely examine its validity.
The idea that seismic records from distant recording stations could be used to establish the duration of a building collapse or demolition is highly questionable on its face given the complexities inherent in interpreting seismic data, such as the indirect relationship between ground movement at a source and and at an observatory miles away. Nonetheless, the assertion that seismic records from observatories such as that in Palisades establish that each Tower collapsed within ten seconds is widespread.

Origin of Claim that Towers Fell in Ten Seconds or Less

The assertion that both Towers fell in ten seconds or less apparently originated with proponents of the collapse theory less than a month after the attack. An article in the Journal of the The Minerals, Metals & Materials Society contains the following:
This started the domino effect that caused the buildings to collapse within ten seconds, hitting bottom with an estimated speed of 200 km per hour. If it had been free fall, with no restraint, the collapse would have only taken eight seconds and would have impacted at 300 km/h. 1
-- Why Did the World Trade Center Collapse? Science, Engineering, and Speculation
Figure 1: Table 1.1 from Chapter 1 of FEMA's WTC Building Performance Study.
The statement cites reference 1, which is listed as "1. Presentation on WTC Collapse, Civil Engineering Department, MIT, Cambridge, MA (October 3, 2001)."
Most of the more contemporary references to the ten-second collapse times appear to have originated with FEMA's Building Performance Study. Although the Report makes no claim about how long it took the Towers to "collapse", it includes the chart on the right describing the duration of seismic signals. That chart gives 10 and 8 seconds for the durations of the signals corresponding to the South and North Tower "collapses", respectively.
Apparently, the only official report that gives a duration for either of the "collapses" is the 9/11 Commission Report, which states that the South Tower collapsed in ten seconds in Chapter 9, Section 2:
At 9:58:59, the South Tower collapsed in ten seconds, killing all civilians and emergency personnel inside, as well a number of individuals-both first responders and civilians -- in the concourse, in the Marriott, and on neighboring streets. The building collapsed into itself, causing a ferocious windstorm and creating a massive debris cloud. 156
-- -- 9/11 Commission Report
This passage cites reference 156, which is listed as "NIST report, 'Progress Report on the Federal Building and Fire Safety Investigation of the WTC,' June 18, 2004, appendix H, p. 40." However, wtc.nist.gov lists no publication dated June 18, 2004, and NIST-SP 1000-5 June 2004 Progress Report on the Federal Building and Fire Safety Investigation of the World Trade Center , [PDF] does not appear to provide any estimate of either Tower's collapse duration.

Video Records Show 15-Second+ Durations

Unlike seismic records, video recordings of the Towers' destruction allow the conclusive determination of lower bounds for the durations of each event, and those are much greater than ten seconds. Several live television broadcasts showed these events from their precipitous onsets to their explosive dust-shrouded conclusions. In each case, portions of the Tower below the exploding rubble clouds are visible up to at least the 12 second mark.
Figure 2: The North Tower at about 10 seconds into its destruction. About two-thirds of the Tower is still standing.
Lacking access to the uncut original broadcasts, I assembled timelines for each Tower using multiple video clips. These timelines clearly show that, in the case of each Tower, the process of destruction lasted a minimum of 15 seconds, not counting the persistence of fragments of core structures. This is true even accounting for uncertainties in precise times of onsets, greater uncertainties in the times of completions, and margins of error in the compositing of the timelines.
The onsets of the events are different in the two Towers. The South Tower's top leans for about two seconds before the roof starts to plunge downwards, whereas the North Tower's roof begins its plunge about a half second after its radio antenna begins to drop. In both cases I used the first evident motion -- the rotation of the South Tower's top, and the drop of the North Tower's antenna -- to set the timeline origin. Using these timelines, it is clear that large portions of each Tower below the descending debris clouds remained intact at the 10-second mark. Reasonable estimates for the duration of these events are around 17 seconds.

Did Seismic Spikes Really Precede Collapses?

The claim that seismic "spikes" preceded the collapse of each Tower has been uncritically reported by numerous websites, books, and videos challenging the official collapse story, including: WhatReallyHappened.com, Serendipity.li, Synthetic Terror,9/11 Revealed, Loose Change, and 9/11 Mysteries. The claim is that the greatest ground shaking, whose estimated local magnitude was 2.1 and 2.3 on the Richter scale, occurred before or at the beginning of the destruction of each Tower, not at the end as the falling rubble was impacting the ground.

Origin of Claim that Spikes Preceded Collapses

Seismographs at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, 21 miles north of the WTC, recorded strange seismic activity on September 11 that has still not been explained.

While the aircraft crashes caused minimal earth shaking, significant earthquakes with unusual spikes occurred at the beginning of each collapse. The Palisades seismic data recorded a 2.1 magnitude earthquake during the 10-second collapse of the South Tower at 9:59:04 and a 2.3 quake during the 8-second collapse of the North Tower at 10:28:31.

The Palisades seismic record shows that -- as the collapses began -- a huge seismic "spike" marked the moment the greatest energy went into the ground. The strongest jolts were all registered at the beginning of the collapses, well before the falling debris struck the earth. These unexplained "spikes" in the seismic data lend credence to the theory that massive explosions at the base of the towers caused the collapses.
-- Christopher Bollyn, American Free Press
The article mixes facts about the Lamont-Doherty Earth Observatory's charts with unfounded assertions. While it's true that the station recorded 2.1 and 2.3 magnitude quakes, Bollyn provides no evidence that the spikes occurred at the beginning of each "collapse".
This story was reproduced by numerous websites, and continues to be cited even by scholars who apparently have failed to check the validity of its claims. After first providing some background on seismology, I will provide three lines of analysis showing that the largest seismic signals correspond to the times that the rubble was reaching the ground, not to times at or before the onsets of the Tower's destruction:

Interpreting Seismograms

Interpreting the data from seismographs is not as straightforward as implied by the article "Seismic Evidence Points to Underground Explosions Causing WTC Collapse". Seismology is a science typically practiced by scientists with graduate degrees in seismology or geophysics. Correctly interpreting the data from seismometers includes considering such factors as:
  1. Different response characteristics of different seismometers
  2. The various types of seismic waves and their propagation characteristics
  3. Different rates of propagation of a given type of seismic wave through different types of soil and rock
The first factor is typically dealt with by processing the instrument data with various functions such as convolution filters. The graphs presented on this page have already been massaged in some way.
The second factor arises from there being four distinct types of seismic waves, which belong to two categories: body waves, which can propagate deep underground, and surface waves, which propagate near the surface. Body waves come in two types: P or pressure waves, which oscillate in the direction of propagation, and S or shear waves, which oscillate perpendicular to the direction of propagation. Surface waves also come in two types: Rayleigh waves, which cause the ground to move laterally, and Love waves, which cause it to undulate vertically. Each of these waves has different propagation rates, which are similar for the two types of surface waves.
Figure 3: Vertical components of the North Tower event recorded by seismometers at five different observatories
According to the article Seismic Waves Generated by Aircraft Impacts and Building Collapses at World Trade Center, New York City by scientists at the Lamont-Doherty Earth Observatory of Colombia University, seismometers at the various observatories recorded only surface waves arising from events in lower Manhattan on 9/11/01.
The third factor can result in different observatories producing very different seismograms for the same event, because of the differing ground structure between the source and the different observatories.
Consider Figure 3, which shows recordings of the North Tower destruction made at five different observatories. The graphs are arranged in order of the distance of their respective observatories from the World Trade Center, with the Palisades chart being the first. The length of the high-amplitude signal varies from about six seconds for the observatories labeled TBR and ARNY to about 18 seconds for the one labeled MANY. The signal recorded by the observatory at Palisades (labeled PAL) has an intermediate length of about 10 seconds. According to the Colombia University scientists, the differing durations of the signals recorded by the different stations was a function of paths the wave packets took from their source to the various stations. Whereas waves followed relatively simple paths to the TBR, ARNY, and BRNJ stations, their traversal to the MANY and PAL stations up the Hudson was complicated by different strata of rock with different traversal speeds. The scientists concluded that the source event was about 5-6 seconds in duration, meaning that the signal at PAL was spread out by about 4 seconds.

The 'Large Spikes' Were Preceded by Smaller Signals

With the benefit of this background information let's look at a PAL seismogram in Figure 4, below. which represents horizontal ground displacement produced by the North Tower's destruction. At about 5 seconds into the graph we see a transition from background noise to a distinct signal with a period of about 0.8 seconds. That signal continues up until the onset of the large signal at about 17 seconds, becoming slightly stronger at about 9 seconds. The first signal thus starts about 12 seconds before the large signal. Since the spread of about 4 seconds would affect the small and large signals alike, the arrival of the first signal about 12 seconds before the large signal at PAL indicates the onset of an event generating a smaller disturbance about 12 seconds before an event generating the large disturbance at the source. A similar pattern is evident in the seismic records from the other observatories.
Figure 4: East-West component of the North Tower event recorded at PAL
If we now review the video timeline of the North Tower, we see that the rubble begins to reach the ground about 12 seconds after the roof begins to drop. Thus, the PAL chart, and those of the other observatories, show a pattern of seismic activity that fits the following interpretation of the North Tower's destruction. As the Tower breaks up from top to bottom, it generates a seismic disturbance of relatively consistent magnitude lasting as long as it takes the destruction to reach the ground -- about 17 seconds. At about 12 seconds into this event, this signal is eclipsed by the much larger disturbance of thousands of tons of material impacting the ground.

Correlating Seismic and Video Records of the North Tower

Figure 5: Frames from CNN's live broadcast at 2 second intervals
In my earlier analysis of the Towers' speed of fall I attempted to establish a correspondence between the CNN live broadcast of the North Tower's destruction and a seismogram from PAL showing that event. Correlating the timelines of these two pieces of evidence is possible because the CNN broadcast shows a real-time clock, the seismic records include precise time coordinates, and the travel time of seismic waves between the source and seismic observatory can be estimated.
The CNN live broadcast of the North Tower destruction, which is excerpted by this video clip, has a real-time clock on its banner which displays hours and minutes. The minute counter flips from 28 to 29 about 37 seconds after the roof starts to drop. On that basis, I estimated, in 2003, that the North Tower's destruction started at 10:28:23. That is one second from the time NIST assigned to the event in its 2004 Draft Report on the Twin Towers: 10:28:22.
Reports published on colombia.edu estimate that the start of the large signal originated at 10:28:31. The large spikes began to reach the PAL seismometers starting at around 10:28:48. Since Colombia scientists estimated that the surface waves traveled at about 2 km/s, and the station is 24 km from the World Trade Center, they placed the time of the onset of the large signal at the source at 17 seconds before the signal arrived at the observatory.
10:28:31 -- the estimated start of the large signal -- is 9 seconds after 10:28:22 -- the estimated start of the North Tower's destruction. Video recordings show that the rubble started to reach the ground about 12 seconds after the start of the destruction. These times fit the interpretation that the large signal corresponded to rubble hitting the ground, modulo an error of about 3 seconds. That error can be explained by the spread in arrival of wave packets described above.
To summarize, the video and seismic data support the following approximate timeline for the North Tower's destruction:
10:28:22North Tower roof starts to drop (small signal starts)
10:28:34Rubble starts to hit the ground (large signal starts)
10:28:36The heaviest rubble hits the ground (large signal peaks)
10:28:40The Tower is completely down, except for fragments of the core

Rubble Ground Impact Energy Explains Large Signal

In the article that first claimed that a "huge seismic 'spike'" marked the beginning of each "collapse", Bollyn also asserted that the signals were "strange", "unusual", "unexplained", and support a theory that "massive explosions at the base of the towers caused the collapses." However, none of these assertions are supported by the scientists at Lamont-Doherty Earth Observatory that Bollyn interviewed. Those scientists reported that the seismic energy represented only a fraction of the gravitational potential energy released when the Towers came down:
The gravitational potential energy associated with the collapse of each tower is at least 1011 J. The energy propagated as seismic waves for ML 2.3 is about 106 to 107 J. Hence, only a very small portion of the potential energy was converted into seismic waves.
-- Seismic Waves Generated by Aircraft Impacts and Building Collapses at World Trade Center, New York City
Visual records of the events themselves and their aftermath clearly show that most of the mass of the Towers fell outside their footprints. Tens of thousands of tons of steel assemblies fell through the air -- some of it from a height of more than a thousand feet -- before hitting the ground. It is difficult to imagine that any events prior to the rubble hitting the ground could have produced anywhere near as much ground shaking. Even the detonation of large bombs in the building would have been dwarfed by comparison. According to the same scientists, the 1993 basement bombing did not produce detectable seismic signals:
A truck bomb at the WTC in 1993, in which approximately 0.5 tons of explosive were detonated, was not detected seismically, even at a station only 16 km away.
-- Seismic Waves Generated by Aircraft Impacts and Building Collapses at World Trade Center, New York City
The 1993 explosion was so intense it blew a cavity about 5 stories high in the parking garage, constructed of steel-reinforced-concrete. Being in the basement, it was presumably well-coupled to the ground. Cutter charges needed to sever the Towers' core columns would be tiny by comparison.
The claim of "massive explosions at the base of the towers" at the onsets of the Towers' destruction is echoed by the 2005 film 9/11 Eyewitness, and other productions. None of these produce credible evidence to support this idea, which is contradicted by the visual records including photographs and videos, and the most credible and extensive body of eyewitness accounts.

The Seismic Records as Evidence of Controlled Demolition

The term controlled demolition has a broader meaning than many people appreciate. It does not require that a building be destroyed from the ground up, as NIST's Answers to Frequently Asked Questions or Protec's Critical Analysis imply. It simply means the destruction of a building in a controlled, or engineered, manner. In the case of the Twin Towers' top-down destruction, it is the only alternative to the premise of the official story that the Towers collapsed due to impact and fire damage. Hence a disproof of this premise would constitute a proof of controlled demolition. A disproof of a particular theory satisfying that premise would not prove controlled demolition since another theory, perhaps yet undiscovered, might explain the collapses. However, it is clear that a substantial number of experts have put a great deal of effort in coming up with the most plausible collapse mechanism that money can buy. To disprove the explanation endorsed by NIST -- the agency that has put more than $20 million into researching the issue -- would be strong evidence for controlled demolition.
A number of different theories of the Towers' collapse have been advanced by proponents of the official story, with the two most extensive government reports endorsing mutually contradictory theories. NIST's theory of "column instability" leading to "global collapse" has replaced FEMA's theory of floor pancaking leading to the buckling of "unsupported columns" as the explanation favored by most informed supporters of the official story. NIST's theory is essentially a pile-driver theory, in which the top of the Tower smashes the intact portion of the building to oblivion, from the crash zones downward. NIST hides the fact that it depends on this theory by failing to acknowledge the progressive nature of the event.
Once the upper building section began to move downwards, the weakened structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building section and global collapse ensued.
-- Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers
The pile-driver, AKA sledgehammer, theory explains the destruction of the intact portion of the Tower by the smashing action of the falling block. NIST hasn't described the scenario, but Professor Bazant did in a paper published in the Journal of Engineering Mechanics ASCE:
At that moment, the upper part has acquired an enormous kinetic energy and a significant downward velocity.
...
The part of building lying beneath is then impacted again by an even larger mass falling with a greater velocity, and the series of impacts and failures then proceeds all the way down.
Why Did the World Trade Center Collapse?-Simple Analysis,
It seems intuitively obvious that a smashing action sufficient to destroy the building would generate intense shaking. Figure 4 shows that the large signal is about 24 times the magnitude of the small signal that precedes it for about 12 seconds. Assuming that displacement magnitude is proportional to power, it follows that there was about 24 times as much energy being released at the peak of rubble hitting the ground than was being released at any one time in the 12 seconds before the rubble started to reach the ground. Since the Tower was mostly destroyed by the time the large signal started, the small signal has to account for the vibrational energy transferred through the columns to the ground from all of the smashing and crushing that was required to destroy the 95 floors of intact steel and concrete below the impact zone. Yet that energy was dwarfed by the energy released by the rubble hitting the ground.
Most expositions of collapse theories invoke the "tremendous energy" of falling mass impacting the floors below to explain the thorough destruction of the Towers. Yet the seismic records clearly show that the vast majority of this mass did not participate in the destruction of the Towers since it evidently did not encounter substantial resistance to its descent until it reached the ground.
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