Analysis of WTC 1 and 2 Collapse Times

[Make7]

Many of you may recall reading the following collapse time analysis by Jim Hoffman.

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 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:

 
 10:28:22 North Tower roof starts to drop (small signal starts)
 10:28:34 Rubble starts to hit the ground (large signal starts)
 10:28:36 The heaviest rubble hits the ground (large signal peaks)
 10:28:40 The Tower is completely down, except for fragments of the core

 
http://911research.wtc7.net/essays/demolition/seismic.html

When I came upon this analysis again recently I noticed that he explains an apparent three second disparity between one possible interpretation of seismic evidence and the video evidence as an error. But what if there wasn't a disparity at all?

Mr. Hoffman states, "Video recordings show that the rubble started to reach the ground about 12 seconds after the start of the destruction." The beginning of the collapse of WTC1 was 10:28:22 as determined by NIST from video evidence. Also found in their report is information regarding a more recent analysis of the seismic data which gives the time for the onset of the seismic event related to the collapse of WTC1 as 10:28:34 - twelve seconds after the start of the collapse.

Duration of the seismic events is available from the LDEO website. The North Tower collapse event lasted about 8 seconds. Adding this to the onset time given above would result in an end time for the seismic event of 10:28:42 am.

Therefore, using this method, the duration of the WTC1 collapse is approximately 20 seconds. (10:28:22 to 10:28:42) The margin of error would likely be ±3 seconds.

Extending this method to the South tower, the beginning of the collapse determined by NIST is 9:58:59, the beginning of the seismic event given in their report is 9:59:07 and the duration as reported by LDEO was 10 seconds.

Therefore, using this method, the duration of the WTC2 collapse is approximately 18 seconds. (9:58:59 to 9:59:17) The margin of error would be the same as for the North Tower.

Does this method of calculating the collapse times give better approximations of the actual times than making an estimate from videos that have the ends of the collapses obscured by clouds of dust?

- Make7

Sources:

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

http://wtc.nist.gov/NISTNCSTAR1-5A_chap_1-8.pdf  (pdf page 118)
DIAL-UP USER WARNING: The link above is to an extremely large file. I have no idea how long it may take to open.
 

[Kingshakabobo]

1. kick

[vincent_vega_lives]

2. All this means is

the laws of physics were suspended and the acceleration due to gravity was much less around Ground Zero.

Proves the use of an anti-gravity beam weapon. :freak:

[LARED]

3. I wonder if an 18 seconds fall time

is within the definition of "nearly freefall?" for CT'ers

Any CT'er care to comment?

[vincent_vega_lives]

5. It IS "nearly free fall"

If you factor in Anti-Gravitons. :crazy:

[Make7]

8. Perhaps I should have used the words "challenge" and "CTers" in the thread title. ( n/t )

[TNOE]

4. What is the "gist" of the WTC.NIST.Gov report?

regarding the fall of the buildings?

[wildbilln864]

6. waiting......

:popcorn:

[Make7]

7. A very brief summary:

The impacts of the planes caused structural damage to the towers and also dislodged some of the spray on fire proofing of steel members. The fires started by the fuel from the impacts of the planes and fed by the contents of the buildings caused weakening of some of the structural elements of the towers. This led to the sagging of portions of some floors which caused the inward bowing of numerous perimeter columns. The subsequent buckling of these perimeter columns initiated the collapse of each respective tower. Global progressive collapse followed due to the inability of the remaining structure to redistribute the loads without also failing.

A more detailed explanation can be found at the following link:

    http://wtc.nist.gov/reports_october05.htm

- Make7

[TNOE]

9. Thank You

Much appreciated - just too much to read right now & no time.