Bldg 7 came down about 7 hours after the towers. There was no visible evidence of damage from the towers falling and the owner, Silverstein, said just before it came down, "Let's pull it."

I cannot have it both ways, can I? If I look at all the reasons people have proposed for bringing down the Two Towers and feel confident that there is only one reasonable cause, why can't I do that for #7?

Is there an engineering analysis of #7's failure?

What is the official name of the building?

WTC 7 I think.

I believe NIST did an engineering analysis. The hypothesis was similar to the towers. Fire from diesel fuel stored in the building for emergency generators weakened the steel and caused the collapse. I believe I paraphrase their conclusion correctly "Our hypothesis has a very low probability of occurence."

If I find the link to that study, I'll post it.

This is another one of the points that leads to doubts. There are supposedly seismographic recordings of the buildings as they fall. The peak disturbances are not from when the buildings hit the ground but from when they begin to freefall.

Here’s a couple of references I scrounged.

http://www.pbs.org/newshour/science/earthquake/buildings.html

http://www.shimz.co.jp/english/support/taishin09.html

When the Transamerica Title building was built in SF there was much ado about the anti-seismic technology that was employed in the building’s design and construction. The devices were several large layered plates of steel rubber and Teflon, used to absorb vertical shock and allow the building’s foundation to move side to side while the building avoided having a lot of the energy transmitted into it. The construction dated to around the same time as the WTC. But Google doesn’t get me a reference to it.

One of the companies I work for does anti-seismic retrofitting. I’ll send em a note to see where industry journals or references can be found.

Also found this

http://www.pbs.org/wgbh/nova/wtc/letters.html

Ever since analyses of the collapse of the twin towers began to appear, I have been troubled by the omission of a most relevant piece of evidence. Dr. Eagar alludes to it in his first sentence but never follows up. My problem is: If the towers came down as a result of the crash-related structural damage, obliteration of fireproofing, and burning fuel, then why did the 47-story Building 7, which was not hit, also fall some hours later? It apparently failed as the result of a common fire. Now that is scary, because it suggests that all tall buildings are likewise vulnerable. Will someone please explain that?

Bill Denton
Mempis, Tennessee


Dr. Eagar responds:

I was also curious about Building 7 when it was described to me. I told the person who described it that there must have been another source of fuel in that building. It turns out there was. Building 7 contained the New York City Emergency Management Control Station, and as a result, it had three tanks of diesel fuel holding tens of thousands of gallons to run their emergency electric generators. What we learn from this is not to store tens of thousands of gallons of fuel in high-rise buildings. Fortunately, most high-rises do not have such huge fuel storage facilities.

Now that is interesting. But for seismic work, timing and location are everything. Sound travels through consolidated earth at over 6,000 fps so if you're off a millisecond, that's a meter. And if you have the finest grade geophones and seismometers, you're still not going to get positional accuracy greater than about a half meter. Likewise, if you use GPS or a theodolite for your location your error ellipse can easily be decimeters off unless you do some fancy triangulation.

So you can easily start your seismic analysis with a meter variance, or about two milliseconds.

Now recall the calculation I made with the speed of sound through steel. From the top of the tower to the ground was less than a millisecond. So if you're seismograph is no more accurate than a milliseconds then your estimate on the building collapse could easily be the height of the Tower.

Don't look now but a squadren of Black helicopters are heading your way now.................... :eek:

Can you explain this some more. The anomoly that I have read about in the seismic readings is that the readings just prior to or at the start of the fall of the towers are higher than the readings when the buildings finally hit the ground. Why would there be evidence of a seismic event just before the buildings come down? Are you saying that it is impossible to tell whether there is a second seismic event after the building fell or before?
It would be quite interesting to compare the seismic readings of the fall of the towers with the seismic readings of buildings deliberately demolished and seismic readings of buildings that just fell (if there are any). This would be particularly useful with Bldg 7. In fact, now that I think about it, this comparison might be a definitive test of whether the buildings were imploded.

Congratulations, you are today's winner of the TwitchKitty award for brainless comments. Hold it near and dear to your heart, though I suspect you will be a repeat recipient.

BTW, that is s-q-u-a-d-r-o-n, squadron. Better luck on the spelling award, maybe another day.

Keeping an open mind is useful to some people, you may want to try it sometime.

Far less brainless than a bunch of left wing conspirocy theories............

Left wing? Where in the hell do you get that?


Wherever it was, get your spell checker somewhere else. You missed on conspiracy this time.

Once again, the term "conspiracy theory" is a product of the media and is a mass media attack against the thinking population. For people in forums to parrot such garbage is just proof of brainwashing. When the people quit questioning the media and the governments we will all be sheep.

The term "Conspiracy Theory" roughly translates into "BAA, BAA". Let me hear you say it again, you do it so well.

You are hardley conservative......its not Fox news that is dreaming this up..its the Liberal media and Liberals who can't come to terms with the fact people are not falling for their line of crap anymore in growing numbers.

I think there is a mass affliction of the left with Obsessive-complusive disorder.

A geophone is a magnet inside of a coil. Shaking the coil induces an EMF. The EMF is transmitted to a recorder. The recorder has a very precise time signal so that every wiggle of the signal is divided into millisecond power readings proportional to the wave train to the geophone. The geophone is placed either on a rigid spike and driven into the ground or it may be placed in a hole and back-filled or rested on the surface. It depends an awful lot on the sensitivity of the device and the records one is looking for. Sometimes an array of geophones are linked in parallel and placed some set distance apart so that the signal is effectively enhanced or and averaged to the must dominant wave train. IT all depends on what type of data the geophycist is interested in studying.

As sound travels through the earth at each transition of medium (say, clay to rock) the sound is both reflected and refracted differently. If the medium is homogeneous then a homogeneous wave train will be recorded.

This system is very good for locating earthquakes. Knowing the speed of sound through the earth, there is a well understood method of deriving the location and epicenter of an earthquake if you have several stations with similar timing signals and good geographical coordinates relating the various positions with each other.

As you can imagine, oil companies like seismic information, too. They set giant 3 dimensional surveyed arrays covering miles of area with geophones. They introduce an energy source of known quantity and location (say, 40# of TNT at 50 ft subsurface at some northing and easting) and then watch the patterns of sound transmission for each of the 3 dimensionally located geophone arrays. They then move to another location and set another charge. As you can imagine, the signal gets offset by each energy source change. They get several terabyte of data and send it to a supercomputer that may spend several weeks reducing all of those various shot points of explosives to a common center and adjusting all of the geophone records in proportion. It is a huge problem of numeric integral calculus. The surveying portion is the type of stuff that Mike Tangas and I did back in the Dark Ages.

Now relating what I know of seismic sensors (limited), knowing the exact placement and time is extremely important. This is because of the tremendous speed at which sound travels through solid media, like rock. So if the geophone is accurately located in time and space, then it can accurately (within a couple of meters) accurately report a signal under ideal circumstances. What are ideal circumstances? Well, consolidated substrate and no background vibrations and no extraneous EMF at the frequencies or harmonics of frequencies being recorded.

Get out your foil hats, boys and girls.

So lets assume that three or more seismographs with are accurately located in time and space. And also assume that they are set on bedrock and not unconsolidated debris. Everything is ideal. Then we see a big signal at first and then lesser amplitudes in the wave form over time. We know from the timing and through triangulation with the other seismographs where this energy originated and when. It turns out to be at the WTC. But really, it’s the WTC plus the height of the WTC at which failure occurred.

By looking at the timing signal, we notice that the largest event happens first and then a damped, periodic staccato afterword. Now we relate that to the event. The first think that happened on the towers was that the upper floors dropped one floor down and hit with full-force on the next floor. This massive drop sent a discrete, powerful jolt down the support columns into bedrock. Each subsequent jolt occurred over 3 meter intervals in proportion to the acceleration of gravity minus the retarding effect of each subsequent floor. When the first jolt happened, nearly all of the building was still intact and highly resistant to thrust, especially in the vertical direction. But as the building accelerated downward, the supporting beams began failing farther and farther down the column—the energy wave-front through steel moved faster than the acceleration of gravity moved the burden downward. Since more mass was pressing down on the central column at each instant of the collapse, the load-bearing members would collapse much faster than the descent of the burden.

Now recall that the seismograph is timing-dependent. If the time signature was large in proportion to the collapse, it would be impossible to segregate each floor failure, especially if the initial pressure created a general failure some distance removed from the first jolt.

http://homes.wsj.com/columnists_com/bricks/20020710-bricks.html

Some financial information in the Wall St Journal about building 7. Mentions the $861 Million insurance settlement.