Seismic event indicating explosion at WTC

[R.Mackey]

Look, I'll make it really, really easy for you.

You just reproduced Figure 3 from that paper, annotated slightly. What you should have done is included the caption:

Figure 3: Record section of vertical-component seismograms from stations in Fig. 2 following collapse of north Tower of WTC. Zero corresponds to computed origin time of 10:28:31 EDT. Data filtered for passband 0.5 to 10 Hz. Three velocities indicated by dotted lines.

Source (Bolding added for clarity)

The researchers at LDEO have already done the time calculation -- that's what the "origin time" refers to. If you run those dotted lines back to zero, where zero is the distance to the WTC Towers, you get the origin time. And that origin time is exactly the same as in the 9/11 Commission Report and in NIST (once you add nine seconds vs. NIST, or six seconds vs. 9/11 Report, from start of collapse to the first impacts on the ground). There is no discrepancy.

They even show it holds for multiple seismographs at various distances, and that the result is consistent with a plausible Rayleigh wave speed of about 2.0 km/s.

Your calculation is wrong.

 

[beachnut]

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

NO BOOM; did someone hit the tripod? BOOM? You have never seen real explosives work have you?


Then tell us how big of a charge was it? 10 tons of TNT, 2000 pounds of TNT? Size please. Funny zero blast effects at the WTC, none in the steel, no body died from blast effects, no BOOM, nothing.

Wow, you will earn a Pulitzer for this work! Why did it take 9 years? Oops, it is a delusion, based on nothing. Sorry, no Pulitzer for made up fantasy junk. Sorry again. 9 years?

 

[T.A.M.]

are you serious...that 1-2 second bit of shaking of the camera? I have done it for longer, and worse with my own video camera by striking the tripod (even a glancing blow). Talk about grasping at straws.

This is ridiculous. You are not even trying, are you Anders?

TAM

 

[carlitos]

. 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.

(Hint: Explosives make noise)

 

[Macgyver1968]

Welcome to the board Anders....Guess the DI forum was getting boring?

 

[Horatius]

In this paper

Interesting quote from page 4:

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.

So how much bigger must this "bomb" have been, to be detected?

 

[femr2]

that 1-2 second bit of shaking of the camera?

http://www.internationalskeptics.com/forums/showpost.php?p=6343867&postcount=309

Movement of WTC 1 begins in close correlation to the shake, along with numerous other visible tower events.

Suggest any discussion is performed on the referenced thread, rather than here.

 

[BigAl]

Interesting quote from page 4:





So how much bigger must this "bomb" have been, to be detected?

Maybe LDEO didn't have the right equipment in 1993. I dunno.

 

[R.Mackey]

Interesting quote from page 4:


So how much bigger must this "bomb" have been, to be detected?

I was going to get to that, if our newcomer was interested.

From other large, non-mining style explosions, such as the Port Chicago disaster, we find that about 1/1000th of the energy of explosion shows up as seismic activity. This is rough and probably varies by a factor of 10 at least, but let's go with it. That's also why the 1993 bomb was not detected. Too small.

We also know the magnitude of seismicity from the collapses, and the total energy of each from calculations of the Tower mass and height. These reveal that in the Tower collapses, about 2% and 5% of the energy, respectively, shows up as ground motion. This larger coupling should be intuitive, given that it's caused by things actually hitting the ground, not exploded away from the ground.

So we conclude that explosives used for demolition are roughly 20 to 50 times less efficient at creating ground shaking. Hence, to get a comparable signal on a seismograph, we'd need 20 to 50 times as much of them.

The Tower collapses each were about 100 tons TNT equivalent. This means to get the same shaking, i.e. to cause the seismographic traces that our newcomer insists were explosives and not from the collapses, our "Demolition Explosives" would be about 2 to 5 kilotons.

That's not a demolition explosive. That's a tac nuke.

Didn't happen.

 

[T.A.M.]

Interesting quote from page 4:





So how much bigger must this "bomb" have been, to be detected?

A mini nuke of course...were you not paying attention at the last truther indoctrination class?

TAM

 

[Anders Lindman]

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

Judging by the camera angle, the camera is positioned fairly close to the building, so a huge explosion should perhaps have been heard. Or, if the explosion was deep in the basement then maybe only low-frequency vibrations, like the shaking of the camera, were registered at that position.

 

[R.Mackey]

Judging by the camera angle, the camera is positioned fairly close to the building, so a huge explosion should perhaps have been heard. Or, if the explosion was deep in the basement then maybe only low-frequency vibrations, like the shaking of the camera, were registered at that position.

There is no explosive. It's been proven to you four separate ways now:

1. Type of ground motion (Rayleigh wave) is inconsistent with explosives
2. Timing of ground motion does not precede the collapse
3. Absence of sound caused by explosives
4. Improbable size of explosives required to match your idea

We're done here.

However, in explaining your mistake I corrected one of my own -- I had forgotten the collapse traces were Rayleigh waves. So I guess it wasn't a total loss. I learned something. Thanks.

 

[Macgyver1968]

If the explosion was deep in the basement, then why did collapse begin at the impact zone? You can hear people crying out in horror as the collapse starts...but yet we can't hear any sounds of explosions?

 

[Anders Lindman]

Welcome to the board Anders....Guess the DI forum was getting boring?

How do you know I'm the same Anders as over there?

 

[Anders Lindman]

If the explosion was deep in the basement, then why did collapse begin at the impact zone? You can hear people crying out in horror as the collapse starts...but yet we can't hear any sounds of explosions?

Because the collapse started where the steel infrastructure had been weakened by fire.

 

[grandmastershek]

Because the collapse started where the steel infrastructure had been weakened by fire.

So what purpose would explosives in the basement serve?

 

[leftysergeant]

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.

To indicate explosives, you would need a bloody HUGE spike ten seconds prior to the spike that indicates the first impact of debris from the top of the south tower. The seismic signal from the first impact of debris on the ground looks rather like what you are looking for, but continues for some 22 seconds, diminishing in strength as it goes. The diminuition of intensity is an obvious result of the debris' not having as much kinetic energy, having fallen from far lower locations.

So, no, there is no explosive spike.

 

[Macgyver1968]

Because the collapse started where the steel infrastructure had been weakened by fire.

Correct...now how does a bomb in the basement cause this?

 

[Anders Lindman]

So what purpose would explosives in the basement serve?

To bring down the core columns.

 

[Anders Lindman]

To indicate explosives, you would need a bloody HUGE spike ten seconds prior to the spike that indicates the first impact of debris from the top of the south tower. The seismic signal from the first impact of debris on the ground looks rather like what you are looking for, but continues for some 22 seconds, diminishing in strength as it goes. The diminuition of intensity is an obvious result of the debris' not having as much kinetic energy, having fallen from far lower locations.

So, no, there is no explosive spike.

The huge seismic event from the explosion in the basement is what we see in the seismogram.