Seismic event indicating explosion at WTC

[Anders Lindman]

I have found evidence for an explosion at the South Tower happening several seconds before the start of the collapse that I would like some feedback on.

Quote from the official 9/11 Commission Report: "At 9:58:59, the South Tower collapsed in ten seconds". See Chapter 9.2 SEPTEMBER 11,2001: http://govinfo.library.unt.edu/911/report/911Report_Ch9.htm

Seismograms recorded by LCSN Station PAL:

Removed hotlinked image. Please see Rule 5.

Replying to this modbox in thread will be off topic  Posted By: LashL

See: http://www.ldeo.columbia.edu/LCSN/Eq/20010911_wtc.html

The seismic recording shows the time for a seismic event related to the collapse of the South Tower: 9:59:04. Notice here that this is the time for the recording at the PAL station. It takes about 17 seconds *) for the seismic wave to reach the PAL center from the source at the WTC. Therefore the time for the seismic event at the source was: 9:58:47.

The time difference between the start of the collapse 9:58:59 and the recorded seismic event at the source 9:58:47 for the South Tower is 12 seconds. This indicates that an explosion happened at the WTC about 12 seconds before the start of the collapse of the South Tower.

I have seen claims that the time scale on the x-axis of each seismogram shows the time at the source, not at the PAL station where they were recorded. But the diagram says: "East-West component of motion at PAL". Indicating the time at the source wouldn't make sense for a seismogram, and if the time indicated was at the source then we get an inconsistency between the time stated in the official 9/11 Commission Report and the time recorded at the PAL station. This cannot be blamed on low signal-to-noise errors in time measurement at the PAL station since this was a large seismic event.

*) "This is based on an estimate of 2 km/s travel speed for the S waves, which, given the PAL station's distance of 34 KM from the WTC, gives a travel time of 17 seconds." -- From: http://911research.wtc7.net/wtc/analysis/collapses/freefall.html

 

[R.Mackey]

Discussed and solved here: http://www.internationalskeptics.com/forums/showthread.php?p=3685275#post3685275


ETA: With one additional detail. The propagation from the aircraft impacts are Love waves, at about 1.6 - 2 km/s. But the propagation from the collapses, i.e. of debris hitting the ground, are S-waves, and propagate at about 5 km/s. That's why you're confused.

Welcome to the Forums, and welcome to 2008.

 

[Anders Lindman]

Discussed and solved here: http://www.internationalskeptics.com/forums/showthread.php?p=3685275#post3685275


ETA: With one additional detail. The propagation from the aircraft impacts are Love waves, at about 1.6 - 2 km/s. But the propagation from the collapses, i.e. of debris hitting the ground, are S-waves, and propagate at about 5 km/s. That's why you're confused.

Welcome to the Forums, and welcome to 2008.

I was using this source: http://911research.wtc7.net/wtc/analysis/collapses/freefall.html

There it says that S waves have a travel speed of 2 km/s. You are saying 5 km/s. How would I know which source is true?

 

[R.Mackey]

Because one source is Jim Hoffman, who is provably a lunatic.

If you don't like my sources, feel free to ask a professional geologist. In fact, I strongly recommend it. Be sure to ask him or her the difference between Love waves and S waves, and which is more likely to occur in the different situations.

 

[femr2]

the propagation from the collapses, i.e. of debris hitting the ground, are S-waves, and propagate at about 5 km/s.

S-waves travel at 3 – 4 km/s in typical Earth’s crust; ~ 4.5 km/s in Earth’s mantle; ~ 2.5-3.0 km/s in (solid) inner core.

5 km/s is overdoing it somewhat.

 

[Anders Lindman]

Because one source is Jim Hoffman, who is provably a lunatic.

If you don't like my sources, feel free to ask a professional geologist. In fact, I strongly recommend it. Be sure to ask him or her the difference between Love waves and S waves, and which is more likely to occur in the different situations.

I looked it up now on Wikipedia and it says that the speed of a P wave is about 5000 m/s in granite, and that an S wave has a speed of about 60% of a P wave = 3000 m/s, and since there is not likely pure granite all the way from the WTC to the PAL station I would say that the true speed for that kind of S wave is less than 3 km/s, maybe even as low as 2 km/s as my source claims.

See: http://en.wikipedia.org/wiki/Seismic_wave

 

[R.Mackey]

A P wave is also a possibility. But even using that lowball estimate for S waves, it's almost twice as fast as a Love wave.

You don't have enough precision in your experiment to back up your claim, which by the way is already contradicted by the lack of SOUNDS. You cannot set off explosives of that magnitude, dwarfing the collapse itself on a seismograph, and then try to convince me that people near (and even inside) the structure didn't hear them. So we know without doing any calculation at all that you are wrong. I'm merely identifying the most likely reason why.

 

[Anders Lindman]

A P wave is also a possibility. But even using that lowball estimate for S waves, it's almost twice as fast as a Love wave.

You don't have enough precision in your experiment to back up your claim, which by the way is already contradicted by the lack of SOUNDS. You cannot set off explosives of that magnitude, dwarfing the collapse itself on a seismograph, and then try to convince me that people near (and even inside) the structure didn't hear them. So we know without doing any calculation at all that you are wrong. I'm merely identifying the most likely reason why.

I think it would be important to know the exact travel speed for an S wave from WTC to the PAL station. I will do a web search for this. Surely the official 9/11 commission must have established the true speed in the actual real-life conditions.

 

[R.Mackey]

Fortunately for you, that information is known. The LDEO has a very good idea of the propagation speeds in their own neighborhood.

Now, I suggest you do as I already told you, and consult a professional. Do you need their phone number? It's not hard to find.

 

[Anders Lindman]

Fortunately for you, that information is known. The LDEO has a very good idea of the propagation speeds in their own neighborhood.

Now, I suggest you do as I already told you, and consult a professional. Do you need their phone number? It's not hard to find.

I couldn't find the exact information on the Web. However, I have now sent an email to LDEO about this, and hopefully they will reply.

 

[Mancman]

There's a recorded phone call of Kevin Cosgrove on the phone to the emergency services, from the 105th floor of the South Tower. The call lasts 5 minutes and lasts until collapse begins. No explosions are heard, 12 seconds prior or at any other time. Why is that, Anders?

 

[beachnut]

I think it would be important to know the exact travel speed for an S wave from WTC to the PAL station. I will do a web search for this. Surely the official 9/11 commission must have established the true speed in the actual real-life conditions.

Bombs big enough to make the seismic waves the WTC debrief really made, would have killed any person hit by the shock-wave. The WTC released over 130 TONS of TNT energy in each KE collapsing tower.

Guess you missed the 93 bomb? Have you ever been close to a small charge going off? Do you know the safe distance to be for an explosive going off and why? Any clue what size a bomb would have to be to make an equal seismograph seen from the collapsing WTC towers?

Your Bomb idea by Hoffman may be a meth/drug/ignorance induced conclusion. Hoffman has thermite in the ceiling tiles as his version of what happen to the WTC towers. The only thing Hoffman's web site is good for is following the references which debunk his claims. He is self debunking if you use his sources.

Believing Hoffman's delusional claim is a sign you may be gullible.

 

[R.Mackey]

I couldn't find the exact information on the Web. However, I have now sent an email to LDEO about this, and hopefully they will reply.

Sounds good.

I should correct my statements above a little, however. Understand it's been over two years since I've thought about this.

In this paper from LDEO, they identify the waves from the collapses as neither S nor P waves, but also not Love waves. Instead, the collapses generated Rayleigh waves, which are similar to S-waves in that they are acoustic waves that travel through the surface -- makes sense for collapsing material. They differ, however, in that the waveform is a "roll" (think of the ground being twisted inward in a ring around the collapse, and that ring of twist moving outward at the wave speed) rather than a compression wave.

The LDEO paper distinguishes between waves felt at short and long distances, those in the short distance estimated at about 2.0 km/s, whereas those further out moved at an average of 3.5 km/s. This is computed by comparing waveforms directly.

In the paper, pay particular attention to Figure 4, which shows the waveform of a Tower collapse (in red) versus the actual origin time. Note the length of the delay.

More importantly, however, look at the shape of the waveform. This is one way we know it's a Rayleigh wave (the other is on which particular seismographs the wave was strongest -- they're not all oriented or coupled to ground in the same way, and different detectors pick out different waves). Explosives will not generate Rayleigh waves. They can't. They do not couple to the ground in that fashion.

So my first guess as to why your timing argument is wrong may be oversimplified. There could easily be another, different bug in there. But if all you want to do is ask the question of explosives, you don't have to bother. The waves seen are inconsistent with explosives no matter when they arrived.

Please report back with LDEO's reply. Thanks.

 

[Anders Lindman]

There's a recorded phone call of Kevin Cosgrove on the phone to the emergency services, from the 105th floor of the South Tower. The call lasts 5 minutes and lasts until collapse begins. No explosions are heard, 12 seconds prior or at any other time. Why is that, Anders?

I'm only looking at the seismic data at the moment. I want to establish the correct travel speed for the seismic waves first. I could have used incorrect numbers.

 

[T.A.M.]

There's a recorded phone call of Kevin Cosgrove on the phone to the emergency services, from the 105th floor of the South Tower. The call lasts 5 minutes and lasts until collapse begins. No explosions are heard, 12 seconds prior or at any other time. Why is that, Anders?

Not to mention all the video coverage, some of it taken within a block of the buildings, that never recorded so much as a single significant explosion.

TAM

 

[Anders Lindman]

Sounds good.

I should correct my statements above a little, however. Understand it's been over two years since I've thought about this.

In this paper from LDEO, they identify the waves from the collapses as neither S nor P waves, but also not Love waves. Instead, the collapses generated Rayleigh waves, which are similar to S-waves in that they are acoustic waves that travel through the surface -- makes sense for collapsing material. They differ, however, in that the waveform is a "roll" (think of the ground being twisted inward in a ring around the collapse, and that ring of twist moving outward at the wave speed) rather than a compression wave.

The LDEO paper distinguishes between waves felt at short and long distances, those in the short distance estimated at about 2.0 km/s, whereas those further out moved at an average of 3.5 km/s. This is computed by comparing waveforms directly.

In the paper, pay particular attention to Figure 4, which shows the waveform of a Tower collapse (in red) versus the actual origin time. Note the length of the delay.

More importantly, however, look at the shape of the waveform. This is one way we know it's a Rayleigh wave (the other is on which particular seismographs the wave was strongest -- they're not all oriented or coupled to ground in the same way, and different detectors pick out different waves). Explosives will not generate Rayleigh waves. They can't. They do not couple to the ground in that fashion.

So my first guess as to why your timing argument is wrong may be oversimplified. There could easily be another, different bug in there. But if all you want to do is ask the question of explosives, you don't have to bother. The waves seen are inconsistent with explosives no matter when they arrived.

Please report back with LDEO's reply. Thanks.

Ah! thanks. Awesome. It looks like my original time of 17 seconds is accurate. Check out:

This means that my initial post still stands.

 

[R.Mackey]

Uh, no it doesn't.

Those waves CANNOT BE CREATED BY EXPLOSIVES.

It means there's a different timing error in your calculation. I suggest you look for it.

 

[Anders Lindman]

Uh, no it doesn't.

Those waves CANNOT BE CREATED BY EXPLOSIVES.

It means there's a different timing error in your calculation. I suggest you look for it.

Maybe margins of errors of plus minus one second or so, but not much more than that. If we do the same calculations for the North Tower we get a time according to the seismic records of an explosion about 10 seconds before the start of the collapse. Compare with this video which shows an explosion (shaking of the camera around 0:20 in the video) about 10 seconds before the start of the collapse. That's two independent sources of evidence, one from seismic records and the other from direct video recording, both consistent with each other showing an explosion happening around 10 seconds before the collapse of the North Tower:

http://www.youtube.com/watch?v=xGAofwkAOlo

 

[Hokulele]

... If we do the same calculations for the North Tower we get a time according to the seismic records of an explosion about 10 seconds before the start of the collapse. ...

No. As has been explained to you, aside from the timing issue, there is a record of a seismic event. There is no evidence that it was a record of an explosion, and in fact, the wave form of that event is evidence that it could not be an explosion.

 

[DGM]

Maybe margins of errors of plus minus one second or so, but not much more than that. If we do the same calculations for the North Tower we get a time according to the seismic records of an explosion about 10 seconds before the start of the collapse. Compare with this video which shows an explosion (shaking of the camera around 0:20 in the video) about 10 seconds before the start of the collapse. That's two independent sources of evidence, one from seismic records and the other from direct video recording, both consistent with each other showing an explosion happening around 10 seconds before the collapse of the North Tower:

http://www.youtube.com/watch?v=xGAofwkAOlo

Why do you think you couldn't hear it in that video? You could clearly hear other background noise.