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Title: “Preliminary Results of WTC7 Study Show Fire Could Not Have Caused Collapse” Could’ve Brought Down World Trade Center Building 7
Source:
Activist Post
URL Source: http://www.activistpost.com/2016/09 ... -not-have-caused-collapse.html
Published: Sep 17, 2016
Author: Derrick Broze
Post Date: 2016-11-24 10:55:56 by Deckard
Keywords: None
Views: 23123
Comments: 54
Preliminary results of a two-year study looking into the destruction of World Trade Center 7 indicates that fire could not have caused the collapse. To mark the 15th anniversary of the 9/11 attacks, the collective 9/11 Truth movement gathered in New York City for two days of street actions, outreach, and the “Justice In Focus” 9/11 Symposium. At the symposium, organized by the Architects & Engineers for 9/11 Truth, the Lawyers Committee for 9/11 Inquiry, and other co-sponsors, there was a heavy emphasis on the possibility of a civil or criminal trial as a means of exposing the truth about the 9/11 attacks. Many 9/11 researchers now focus on the mysterious collapse of building 7. A number of 9/11 family members point to the collapse of WTC7 as a possible crack in the official story that could spark a new national conversation on the events of that day. WTC7 was not hit by a plane that day; however, it collapsed at 5:20 p.m. according to the National Institute of Standards and Technology (NIST), the official cause for the collapse was office fires. A growing number of family members, activists, architects and engineers question the official theory for collapse and are seeking a new investigation into WTC7. In May 2015, a team of researchers from the University of Alaska Fairbanks began a two-year investigation of the collapse of WTC7. Dr. J. Leroy Hulsey, of the University of Alaska Fairbanks, and two Ph.D. research assistants are partnering with the non-profit Architects and Engineers for 9/11 Truth for a two-year engineering study known as “World Trade Center Building 7 Evaluation.” The researchers are using finite element modeling to evaluate the possible causes of World Trade Center Building 7’s collapse. “We will investigate the collapse. We probably will not be able to tell them what caused it, but I could tell them what did not,” Hulsey told MintPress. I am approaching it like most forensic engineers would. We’re looking at the structure itself, trying to put together all of the details of what was available, and in this case very little was available. Because most of it has been destroyed or it’s locked in vaults somewhere. So I have very little to work with. Hulsey explained that he addresses issues raised by NIST, but will not be reading anything about NIST or other previous studies. “I have to maintain an open scientific mind. I don’t want to be led down a path that others have gone down,” he said. “I will read about it once we reach our final conclusions and then cross-check to make sure we don’t have any issues with respect to the science.” During an interview at the Justice In Focus Symposium, Hulsey said that the team has already investigated the theory that fire caused the building’s collapse. “It is our preliminary conclusions, based upon our work to date, that fire did not produce the failure at this particular building.” When their study concludes in April 2017, Hulsey and his team will allow a panel of experts to analyze the data and submit the study to peer-reviewed journals. The researchers are promising a “completely open and transparent investigation into the cause of World Trade Center Building 7’s collapse,” and will post every step of their scientific process on WTC7Evaluation.org. The WTC7 Evaluation project will also include a review by a committee of technical experts who will vet the research being conducted by Dr. Hulsey and his students. Ted Walter, Director of Strategy and Development for A&E 9/11 Truth, is in charge of working with the professor and raising money to fund the WTC7 Evaluation. Walter told Activist Post that the project began in May 2015 and should should wrap up in April of next year. “They are coming up with different scenarios of how hot the fires could have been in different parts of the building, and then for the next 6 months they will be running tests and scenarios,” Walter told Activist Post. “The last few months, early next year, will be all about putting the findings into a final report.” Stay tuned to Activist Post for updates on Dr. Hulsey’s study. 
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#16. To: Deckard (#0)
The firemen at the scene could see the building was going to collapse because of the damage it received. Shouldn't you paultards be moving on to something original like what trump and Dick Cheney may have been doing at Bohemian Grove?
NIST NCSTAR 1A, WTC Investigation, FINAL REPORT on the Collapse of World Trade Center Building 7 At page xxxvii: Structural damage from debris did not cause the collapse.
http://www.youtube.com/watch?v=cgOGmUo9O2Y The NIST Final Report on World Trade Center Building Seven contains a simulation of the collapse. The simulation differs significantly from the videos of the collapse taken on 9/11/2001. Neither the simulation nor the explanation proposed by the NIST is consistent with the observed facts. After first denying it, NIST now admits that WTC7 dropped at free fall acceleration for 2.3 seconds. Only an unsupported and unobstructed structure can drop at free fall acceleration. Another mystery of WTC7 is that a collapse supposedly caused by fire was simultaneous rather than progressive. NIST proposes that the interior of WTC7 underwent a progressive collapse, leaving only the facade standing. Then, the facade collapsed simultaneously and intact. This explanation is not credible because the collapse videos do not show any damage to the facade at a time when the interior was supposedly completely destroyed. Only a few windows were broken when beams and floors were supposedly ripping loose and plummeting to the ground level. In addition, the explanation begs the question of why the facade collapsed simultaneously instead of progressively, and why it survived the collapse of the interior, only to fall by itself. Nor does NIST explain free fall acceleration of the facade. If the facade was so flimsy and weak as to collapse at free fall acceleration, why was it strong enough to survive the collapse of the interior? If it was strong enough to survive the collapse of the interior, why did it collapse suddenly, intact, and at free fall acceleration for 2.3 seconds? https://www.nist.gov/el/faqs-nist-wtc-7-investigation Questions and Answers about the NIST WTC 7 Investigation Contact: Michael E. Newman, michael.newman@nist.gov (link sends e-mail), 301-975-3025 September 19, 2011 (updated 6/27/12) [...] The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse: Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall). Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall) Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity This analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model, which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below. NIST admitted that 7WTC achieved gravitational acceleration, or free fall, for 2.25 seconds. That is 2.25 seconds with the lower part of the building offering ZERO resistance to the upper part. Any resistance whatever slows the rate of descent. It is the law of conservation of energy. Also, picture the main towers. Huge steel pieces were ejected horizontally and caused to damaged or became impaled in a building across the street. Consider the resistance the lower portion must have exerted in order for the requisite horizontal force to have been achieved. I have no clue what mechanism could have caused what was recorded for all time on 9/11. A building cannot achieve gravitational acceleration (free fall) in collapse unless there is some force, in addition to gravity, applied. The lower portion of the building will not offer ZERO resistance. One can visibly observe, while the two towers fall, huge clouds of whatever (dust, powder, very fine particles) being formed. Assume one floor crushed the next floor to dust. Now calculate the force required to do that. The bottom floor must offer enough resistance to get crushed or pulverized rather than just move out of the way. Any energy expended on anything but accelerating the upper part downward slows the rate of descent. The initial theory of pancaking of floors was abandoned as physically impossible. The NIST theory ends at collapse initiation. No theory explains how the buildings came down in the precisely measured times, or how any achieved free fall, without repealing the laws of physics.
Large chunks of rubble, which were in free fall, were clearly falling faster than the rest of the twin towers.
NIST provided the times and an explanation. When the pancake theory was proven impossible, it was abandoned. With that, the explanation collapsed. NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time-calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A). As documented in Section 6.14.4 of NIST NCSTAR 1, these collapse times show that: "... the structure below the level of collapse initiation offered minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that energy through energy of deformation. Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass." In other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was unable to stop or even to slow the falling mass. The downward momentum felt by each successive lower floor was even larger due to the increasing mass. From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely. That 9-second time is the approximate time it would take to drop a ball from the same height as the tower and for the ball to fall through a vacuum offering no resistance and hit the ground. A billiard ball, falling 1368 feet [1WTC] in a vacuum, would take 9.22 seconds to hit the ground. Going through air would take longer. Going through 110 stories of a building would take considerably longer. With any resistance, it would take longer. To go faster would take an added propulsion force to be applied. 100 floors would take 8.79 seconds in a vacuum. If the stories below the collapse offered little resistance, they could not be destroyed and pulverized on the way down. If it offered little to no resistance, it would just move out of the way. Also, if there was little to no resistance, it would be impossible to create the horizontal force needed to throw huge steel pieces hundreds of feet into another building.
Which exterior panels? Panels from the top of the building? If those panels peeled away, then yes, they'be be in freefall. You can see large chunks of rubble, which ARE in free fall, clearly falling faster than the rest of the building.
You may also see great loads of crap going straight up to land all over the surrounding area. Is this a new form of gravity that forces things horizontally or upward while they purportedly offer no resistance whatever to a downward force? The picture does nothing to explain how the building collapse achieved free fall acceleration. In any case, 7WTC achieved free fall acceleration for 2.25 seconds, and there is no similar picture. What is observed is a solid matter building being transformed into a cloud of crap in midair. In order to pulverize something, it must offer enough resistance to be pulverized. Such resistance must slow the rate of descent. If you drop a marble, a bowling ball, or a steel beam off the roof at 1,368 feet, in a vacuum they should all reach the ground in 9.22 seconds, unless some external force besides gravity is acting upon them. The top of the building does not fall through a vacuum or even thin air.
Huh? The picture demonstrates that the building was NOT in free fall. The debris (which IS in free fall) is 20 stories below the top. As for WTC7, that was in free fall only for 2.25 seconds of its 16+ second collapse, due to the complete failure of floors 7-14.
As for WTC7, that was in free fall only for 2.25 seconds of its 16+ second collapse, due to the complete failure of floors 7-14. Free fall is impossible in a gravitational collapse of a multi-story building. To show that a story in wrong, it is not necessary to show what happened. It is only necessary to show that what is described in the story could not have happened. If the building was not in free fall, how did it get down in 9 seconds? The laws of physics say a ball dropped in a vacuum would fall 1368 feet in 9.22 seconds. NIST and the scientific evidence document that 2WTC went from collapse initiation to seismic shock on impact in 9 seconds. For the physics and calculations behind the 9.22 seconds, see: http://drjudywood.com/articles/BBE/BilliardBalls.html The Billiard Ball Example (BBE) By Judy Wood You cannot slow the rate of fall without declaring all the time stamped video or the time stamped seismic data to have been fudged. If 2WTC came down in 9 seconds, that is approximately the time of free fall. NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time-calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A). The NIST attempted explanation was: "... the structure below the level of collapse initiation offered minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that energy through energy of deformation. Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass." When one floor hit the other, the bottom floor exerts and equal and opposite force to that which is exerted upon it. If the lower floors offer little or no resistance, it is impossible for them to be pulverized before hitting the bottom. They are moving out of the way, offering little or no resistance. If it did offer such resistance that it was pulverized, it offered enough resistance to slow the descent and in other observed collapses, the falling object will not continue straight down along the path of most resistance, but will be shunted off to the side. If you slow the collapse of 2WTC, what caused a seismic shock at 9 seconds, and no similar shock after 9 seconds when the building met the ground? The observed phenomena defy explanation applying purely gravitational force. As for 7WTC: Final Report on the Collapse of World Trade Center Building 7, Federal Building and Fire Safety Investigation of the World Trade Center Disaster (NIST NCSTAR 1A) http://ws680.nist.gov/publication/get_pdf.cfm?pub_id=861610 At page xxxvii: Structural damage from debris did not cause the collapse. NIST identifies specific fire observations and their earliest times. "Other than initiating the fires in WTC 7, the damage from the debris from WTC 1 had little effect on initiating the collapse of WTC 7." [NIST NCSTAR 1-9, p. 194] "A larger area of the west face near the south edge is visible in the photograph shown in Figure 5-1 10, which was taken shortly after Figure 5- 109 at 12:27:30 p.m. At this time flames were not evident in window 22-14A, but light smoke continued to flow from the window. Higher up on the face, smoke was coming from the six adjacent open windows 29-11 to 29-14A on the 29th floor, with heavy flames filling windows 29-11 and 29-12. As discussed in Section 5.5.2, the condition of windows 29-13A to 29-14A immediately following the collapse of WTC 1 could not be determined, while the glass was intact in windows 29-11 and 29-12. This suggests that the fire burning on this floor had opened windows 29-11 and 29-12 by 12:27:30 p.m." [NIST NCSTAR 1-9, p. 196] "Prior to 12:10 p.m., there was no evidence of fire on the upper floors of WTC 7. Between 12:10 p.m. and 2:10 p.m., the only fires directly or indirectly observed were on Floors 19, 22, 29, and 30." [NIST NCSTAR 1-9, p. 194] - - - - - "Between roughly 2:00 p.m. and the collapse of WTC 7 at 5:20:52, fires were observed spreading on the 7th floor through the 13th floor, with the exception of the 10th floor. One short video clip indicated that a small fire was present on the north side of the 14th floor shortly prior to the collapse. In the following descriptions of these fires, approximate times are used. Details are included in the previous subsection." [NIST NCSTAR 1-9, p. 243] "7th Floor. Early indications of a developing fire were observed on the west side of the 7th floor shortly after 2:00 p.m." [NIST NCSTAR 1-9, p. 243] "8th floor. The earliest fires observed on the 8th floor were on the north face in windows near the center of the face. As late as 3:22 p.m., there was no indication of fire in this area, but about 17 min later a substantial fire spreading to the east was visib le between windows 8-47C and 8-53C." [NIST NCSTAR 1-9, p. 243] "9th Floor. There was no indication of fire in the available imagery on this floor until late in the day. Shortly before 4:00 p.m., a small area of fire was observed in windows 9-54A and 9-54B on the west side of the north face. There are no images suggesting how fire reached this location." [NIST NCSTAR 1-9, p. 244] "10th Floor. No fires were observed burning on this floor." [NIST NCSTAR 1-9, p. 244] "11th Floor. A fire was first observed on this floor at 2:08 p.m. on the east face." [NIST NCSTAR 1-9, p. 244] "12th Floor. The first observation of a fire on the 12th floor was on the east face around 2:08 p.m." [NIST NCSTAR 1-9, p. 245] "13th Floor. The first visual evidence for burning on the 13th floor was seen on the east face around 2:30 p.m." [NIST NCSTAR 1-9, p. 245] "14th Floor. A low resolution image recorded around 5:03 p.m. indicated the presence of a fire between Columns 45 and 46 on the north face. Fire at this location or elsewhere on the floor was not evident in similar images recorded roughly ten minutes earlier and six minutes later. This was the only observation of a fire on this floor." [NIST NCSTAR 1-9, p. 246] "Fires on Other Floors. With the exception of the fires on the 19th, 22nd, 29th, and 30th floors discussed at the start of this section, there is no direct visual evidence of fires on other floors of WTC 7. Heavy smoke was observed coming from the opening created on the south face of WTC 7 by debris falling from WTC 1. This smoke suggests that internal burning was taking place, but provides little indication of specific locations. Light smoke was observed at the height of the louvers on the east side of the 5th and 6th floors around 4:10 p.m. It was not possible to identify the source of this smoke. [NIST NCSTAR 1-9, p. 246] SOURCE: NIST NCSTAR 1-9, Volume 1
Because it took longer than 9 seconds.
You cannot extend the time unless the recorded phenomena were incorrectly or falsely reported. If you say the collapse took 20 seconds, it does not match the time on the video, nor the time between observed collapse initiation and the seismic event recorded later. Applying time uncertainty to the maximum you may get 10 seconds. This is the problem. Claiming an extended time solves on dilemma but creates another as it contradicts recorded event times. After that, you blow up the NIST report and the scientifically determined timed sequence of events. NIST NCSTAR 1-5A, pp. 23-24: Many of the news broadcasts on September 11, 2001, had the current time imprinted on the screen. These imprints are known in the industry as "bugs." As these broadcasts were timed, it became apparent that there were small differences between times for the second aircraft impact based on these bugs and the time used as the basis for the database. Checks with several broadcasters indicated that the bugs should be quite close to the actual time because the clocks used as sources for the bugs are regularly updated from highly accurate sources, such as geopositioning satellites or the precise atomic-clock-based timing signals provided by NIST as a public service. Careful checks showed small time differences between different video recordings, but these were generally less than 1 s. These small discrepancies were likely due to variations in transmission times resulting from the different pathways that the video signals took to the sites where they were recorded. Based on four independent video recordings, the actual time of the second aircraft impact was determined to be 9:02:59 a.m., or 5 s later than the time assigned in developing the database. The estimated uncertainty is 1 s. Table 3-1 compares times for the major events taken from the database, adjusted to television time, and reported in the FEMA report (McAllister 2002). The times listed for the major events in the FEMA report (McAllister 2002) were based on seismic signals (and analysis) recorded by the Lamont-Doherty Earth Observatory (LDEO) of Columbia University at a location 21 miles from the WTC site in Palisades, New York. These signals have subsequently been reanalyzed by LDEO, working under a contract from the NIST WTC Investigation. (Kim, 2005) A reinterpretation of the types of seismic signals received resulted in slightly revised times for the major events. The results of this recent analysis are also included in Table 3-1. The uncertainty for the first aircraft impact on WTC 1, the collapse of WTC 2, and the collapse of WTC 1 were reported by LDEO to be 1 s, while that for the aircraft impact on WTC 2 is 2 s. Recalling that uncertainties for times of the major events based on the television broadcasts are estimated to be 1 s, it can be seen from Table 3-1 that the two aircraft impact times derived by NIST and LDEO now agree within the combined uncertainties. Times listed in Table 3-1 for the collapses of the two towers based on the television records and the revised LDEO analysis appear to differ significantly. These differences are likely due to different definitions used for the collapse times. The times based on visual analysis refer to the time when the collapse of a tower first became evident, while the times based on seismic records likely indicate the time when the falling debris first struck the ground. The differences between the two times were estimated to be approximately 9 s for WTC 2 and approximately 11 s for WTC 1 based on videos of the collapses. When the times required for falling debris to reach the ground are subtracted from the LDEO times, the collapse times also agree within the reported uncertainties. Since the times derived from television broadcasts (i.e., those in column 3 of Table 3-1) are believed to be accurate and also agree with the most recent analysis of seismic signals, 5 s were added to times included in the NIST WTC databases when precise times were reported for the Investigation. 3.7 REFERENCES Kim, W.X., 2005 "Analysis of Seismogram Data Recorded on September 11, 2001 during the World Trade Center, New York City Disaster, Final Technical Report to the Building and Fire Research Laboratory," Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, January 31. McAllister, T., ed. 2002. World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations. FEMA 403. Federal Emergency Management Agency. Washington, DC, May.
I agree. "If you say the collapse took 20 seconds, it does not match the time on the video" Oh, please. Because of all the dust, no one knows when the building stopped falling. "nor the time between observed collapse initiation and the seismic event recorded later." Again, the seismic chart is subject to interpretation. Some say the chart shows a collapse in 8.4 seconds. Believe that?
I agree. One knows when the building STARTED falling. There is time stamped video. Lots of it. One knows when the building HIT THE GROUND. There is a known time of the seismic event at the nearest geodetic station. When it hit the ground. One knows when the building HIT THE GROUND. There is a known time of the seismic event recorded by at least 13 seismograph stations. "Some say?" You mean your anonymous, undated source? What I believe is that the guy who said that had no clue what he was looking at or what he was talking about. The seismograph does not show a collapse time of 8.4 seconds. The seismograph shows the pulse duration at the recording station reflecting mainly that the generation of seismic energy from the collapse was delivered over a few seconds. A portion of the pulse duration probably resulted from the dispersion of Rg waves. Anderson and Dorman [1973] observed strong lateral refaction of Rg waves caused by contrast in shalow rock properties at the boundary of the high and low velocity rocks of the Manhattan Prong and Neward Basin. Waves propaged to Palisades followed paths through provinces, resulting i multiple arrivals of Rg. On the basis of polarization analysis, several of those wave packets arrived from quite different directions that those predicted for straight-line propagation. Seismic waves at PAL and MANY also are more complex than those at the other stations, probablyy indicative of arrivals refracted through the two terrains. At MANY 10s separates two arrivals. Moreover, seismic waves are only created by brief impulses, and even if the fall of the debris from the Towers onto the ground could have generated seismic waves, their magnitude was insufficient to be recorded 34 km away. 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. The insertion of clouds of dust and falling debris into the discussion is a meaningless distraction. Your source: http://www.911myths.com/html/seismic_collapse_time.html http://www.911myths.com/html/site_faq.html I'm Mike Williams, a software developer and freelance writer from the UK. So, Mike Williams, a software developer, says some unnamed sites on the net make a claim out of the mainstream that the towers fell faster than freefall speeds. That is an impressive source you have there. Why that seismograph is interpreted by some anonymous soul to indicate an 8.4 second collapse time is not described. Here is the link for seismograms at LDEO/Columbia Seismograms recorded by LCSN Station PAL (Palisades, NY) Scientists say they can calculate the time it took for the shock wave to travel from Ground Zero to the geodetic station. They calculate the exact impact time within a second. Nothing has been offered to doubt the scientific report. All the dust in the air could not have caused a seismic shock. It did not exist at the time of collapse initiation. It had zero effect on recording the time of impact with the ground. Do you have any scientific source whatever that questions the methodology used by LDEO to establish the time of the building hitting the ground? My sources: The investigation by the experts at the Lamond-Doherty Earth Observatory (LDEO) of Columbia University was explained in NIST NCSTAR 1-5A. At page 23, it says, Since the times derived from television broadcasts (i.e., those in column 3 of Table 3-1) are believed to be accurate and also agree with the most recent analysis of seismic signals, 5 s were added to times included in the NIST WTC databases when precise times were reported for the Investigation. 3.7 REFERENCES Kim, W.X., 2005 "Analysis of Seismogram Data Recorded on September 11, 2001 during the World Trade Center, New York City Disaster, Final Technical Report to the Building and Fire Research Laboratory," Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, January 31. McAllister, T., ed. 2002. World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations. FEMA 403. Federal Emergency Management Agency. Washington, DC, May. https://www.ldeo.columbia.edu/LCSN/Eq/20010911_WTC/WTC_LDEO_KIM.pdf Seismologists sometimes do their work of data acquisition and analysis against a tragic background. Usually the context is fieldwork far from home, in an area subjected to the natural but sometimes devastating effects of an earthquake. But in the present case we are in our own New York City area; that is, the Lamont-Doherty Earth Observatory of Columbia University, in Palisades, N.Y.; and the context is inhuman actions against people and the fabric of our society. As the appalling events of September 11 unfolded, we found that we had recorded numerous seismic signals from two plane impacts and building collapses from the two World Trade Center (WTC) towers, often at times different than those being reported elsewhere. Collapses of the two WTC towers generated large seismic waves, observed in five states and up to 428 km away. The North Tower collapse was the largest seismic source and had local magnitude ML 2.3. From this we infer that ground shaking of the WTC towers was not a major contributor to the collapse or damage to surrounding buildings, but unfortunately we also conclude that from the distance at which our own detections were made (the nearest station is 34 km away at Palisades, N.Y.) it is not possible to infer (with detail sufficient to meet the demands of civil engineers in an emergency situation) just what the near-in ground motions must have been. Signals at Palisades from Impacts and Collapses Figure 1 shows seismic signals at Palisades, N.Y. (PAL) for the impacts and collapses, which are labeled by their arrival time order. Note that impact 1 and collapse 2 relate to the north tower, and impact 2 and collapse 1 apply to the south tower. Computed origin times and seismic magnitudes are listed in Figure 1. Origin times with an uncertainty of 2 s were calculated from the arrival times of Rg waves at PAL using a velocity of 2 km/s. The collapse of 7 WTC at 17:20:33 EDT was recorded but is not shown. Three other small signals shown in Figure 1 and ones at 12:07:38 and 12:10:03 EDT may have been generated by additional collapses. Surface waves were the largest seismic waves observed at various stations. The presence of seismic body waves is questionable even at Palisades for the two largest collapses; they are not observed at other stations. Local magnitudes ML, like those defined originally by Richter for southern California but with distance correction factors appropriate for eastern North America [Kim, 1998], were computed for the two impacts and the three largest collapses. For collapses 1 and 2, values of ML determined from E-W components are 2.1 and 2.3. ML is 0.1 to 0.2 units smaller on the vertical, an observation that we associate later with multipath propagation. Amplitude spectra for PAL data are shown at the right of Figure 1 for the impacts and the 1 collapses of the twin towers. The spectra of collapses 1 and 2 are above the noise for frequencies from 0.2 to 10 Hz. The two spectra are similar, but the second shows a more pronounced peak near 1 Hz. Seismic signals from both impacts are characterized by relatively periodic motion and their spectra are above the noise only for frequencies from about 1.3 to 1.6 Hz. Those frequencies are more than 10 times the frequency of the lateral fundamental mode of each tower. Observations in Mid-Atlantic States and New England Lamont-Doherty operates 34 seismograph stations in seven Mid-Atlantic and New England states. The network has been in operation since the early 1970s, but the stations, types of recording, and data transmission have changed with time. Digital data are now sent via the Internet in real time to Palisades. They are supplemented by data from the U.S. National Seismic Network. The modern stations record over a broad frequency band; some like PAL sample three components of ground motion, but others, only the vertical. Information on the stations and WTC recordings is available at www.ldeo.columbia.edu/LCSN. The data were sent to the Data Management Center, Incorporated Research Institutions for Seismology (IRIS), in Seattle, Washington. Seismic waves from Collapse 2 were recorded by at least 13 stations ranging in distance from 34 km to Lisbon, NH at 428 km. The magnitude of the event was only 2.3. The predominant signals at distances greater than 200 km are short-period surface waves, which propagate at wave speeds of about 3.5 km/s, the typical Lg group velocity observed for the largest waves from earthquakes at regional distances in eastern North America. Those observations will be published separately. Seismic Waves in Greater New York City Area Six stations within the greater Metropolitan New York region (Fig. 2) recorded the two tower collapses. Vertical-component records are shown in Figure 3 as a record section of distance as a function of travel time. The dotted lines indicate velocities from 1.5 to 2.5 km/s assuming propagation along straight paths from the WTC to the stations. Unlike signals at distant stations, the predominant waves are surface waves of short period (about 1 s) called Rg with group velocities between 2.3 and 1.5 km/s. GPD only recorded horizontal components. Relatively simple and similar pulses with durations of about 5 to 6 s arrive at stations BRNJ, TBR and ARNY starting at a group velocity of 2.0 km/s. The paths to each of those stations from the WTC are mostly in the low-velocity sedimentary rocks of the Newark Basin (N.B. in Fig. 2), the region of low topography west of the Hudson River and southeast of that of higher topography 2 in the Hudson Highlands (Reading Prong). Since those paths cross the boundaries of the Basin at a high angle, the signals at those stations are relatively simple. The signals (not shown) at LSCT, a station in northwestern Connecticut, are also relatively simple, reflecting propagation over a distance of 125 km entirely within the high-velocity rocks of the Manhattan Prong (M.P. in Fig. 2). Their group velocity of about 3.0 km/s is consistent with Rg propagation in that faster, older terrain. Thus, we conclude that the pulse duration at those four stations relects mainly that the generation of seismic energy from the collapse was delivered over 5-6 s. A portion of the pulse duration probably results from the dispersion of Rg waves. Anderson and Dorman [1973] observed low group velocities from quarry blasts for paths that propagate mainly though the Newark Basin, and higher velocities for paths within the Manhattan Prong. Their largest arrivals also were the short-period Rayleigh wave Rg. Short-period Rg is well excited only for surface or very shallow sources, which is the case for the WTC. Since Rg propagates mainly in the upper several kilometers of the crust, it is affected strongly by rock properties in that depth range. Anderson and Dorman also observed strong lateral refraction of Rg waves caused by the contrast in shallow rock properties at the boundary of the high and low velocity rocks of the Manhattan Prong and Newark Basin. Waves propagated to Palisades followed paths through both provinces, resulting in multiple arrivals of Rg. On the basis of polarization analysis, several of those wave packets arrived from quite different directions than those predicted for straight-line propagation. Seismic waves at PAL and MANY also are more complex than those at the other stations of Figure 3, probably indicative of arrivals refracted through the two terrains. At MANY 10s separates two arrivals. The constructive interference of two Rg phases at PAL may well account for the large arrivals on the E-W component even though the azimuth of the direct path from WTC to PAL is NNE. We do not interpret them necessarily as Love waves; hence, a source with a horizontal component is not required to explain them. (We veriied that the components and polarities of the digital data at PAL were correct using recordings of distant earthquakes close in time to the WTC events.). Comparison with Signals from Earthquakes, Gas Explosion and Mine Collapse The signals at PAL from Collapse 2 and a small felt earthquake beneath the east side of Manhattan on January 17, 2001 are of comparable amplitude and ML (Fig. 4). The character of the two seismograms, however, is quite different. Clear P and S waves are seen only for the earthquake. The 7-km depth of the earthquake suppressed the excitation of short- period Rg, 3 which is so prominent for the collapse. The difference in the excitation of higher frequencies also can be attributed to the short time duration of slip in small earthquakes compared to the combined source time of several seconds of the complex system of the towers and foundations responding to the impacts and collapses. The waves from the WTC events resemble those recorded by regional stations from the collapse of part of a salt mine in western New York on March 12, 1994 (ML 3.6). That source also lasted longer than that of a small earthquake. 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. An explosion at a gasoline tank farm near Newark NJ on January 7, 1983 generated observable P and S waves and short-period Rg waves (ML 3) at PAL. Its Rg is comparable to that for WTC collapse 2. Similar arrivals were seen at station AMNH in Manhattan, which is no longer operating, at a distance of 15 km. AMNH also recorded a prominent seismic arrival at the time expected for an atmospheric acoustic wave. We know of no microbarograph recordings of either that explosion or the events at the WTC. Many people asked us if the arrivals at seismic stations from the WTC events propagated in the atmosphere. We ind no evidence of waves arriving at such slow velocities. Instead the seismic waves excited by impacts and collapses at the WTC are short-period surface waves, i.e. seismic waves traveling within the upper few kilometers of the crust. Significance of Findings for On-Site Conditions Unfortunately, no seismic recordings of ground motion are currently known to exist at or very close to the WTC. Plans are pending for an Advanced National Seismic System (ANSS; see USGS [1999]) that calls for increased urban seismic instrumentation, including New York City, and the September 11 events show that such instrumentation can be valuable to serve a purpose that sometimes transcends strict earthquake applications. Since the main collapses, a major concern has been if strong shaking affected the structural stability of nearby buildings. Earthquakes of ML 2.3 are not known to cause any structural damage in buildings. In the eastern U.S. that threshold is believed to be close to or above ML 4 to 4.5. It is more reasonable that most of the effects of those collapses on adjacent structures and people were related to the kinetic energy of falling debris and the pressure on buildings exerted by dust- and particle- laden air mobilized by falling debris. It had, except for temperature, an effect very similar to pyroclastic ash lows that descend slopes of volcanoes. The seismic shaking associated with the impacts and the main collapses probably was small compared to those other energetic processes. The following order-of-magnitude estimates of energies involved corroborate this interpretation. 4 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. Most of the energy went into deformation of buildings and the formation of rubble and dust. The perception of people in the vicinity of the collapses as reported in the media seems to be in full accord with the notion that ground shaking was not a major contributor to the collapse or damage to surrounding buildings. The seismic energy of a ML 0.7 to 0.9 computed for the impacts is a tiny fraction of the kinetic energy of each aircraft, about 2 x 109 J. That associated with the combustion of 50 to 100 tons of fuel in each aircraft is roughly 1012 J, most of which was expended in the large fireballs (visible in TV images) and in subsequent burning that ignited material in each tower. Less than a millionth of the fuel energy was converted to seismic waves. Acknowledgments We thank critical readers W. Menke and C. Scholz. We appreciate comments by Terry Wallace, Mehmed Celebi and John Goff. Lamont-Doherty Cooperative Seismographic Network (LCSN) is part of the Advanced National Seismic System. We thank the many individuals and institutions that collaborate with us in operating the network. LCSN operation is sponsored by the U.S. Geological Survey under Grant Number 01-HQ-AG-0137. Lamont-Doherty Earth Observatory Contribution 6267. Authors Won-Young Kim, L . R . Sykes1,J . H . Armitage, J . K . Xie, K . H . Jacob, P. G . Richards1,M . West1, F. Waldhauser, J. Armbruster, L. Seeber, W. X. Du1 and A. Lerner-Lam1, Lamont-Doherty Earth Observatory of Columbia University, Palisades, N.Y. 10964, USA; 1also Dept. Earth and Environmental Sciences, Columbia University. References Anderson, J. and J. Dorman, Local geological effects on short-period Rayleigh waves around New York City, Bull. Seism. Soc. Am., 63, 1487-1497, 1973. Kim, Won-Young, The ML scale in eastern North America, Bull. Seism. Soc. Am., 88, 935-951, 1998. U.S. Geological Survey, An Assessment of Seismic Monitoring in the United States: Requirement for an Advanced National Seismic System, U.S. Geological Survey Circular 1188, 55 pages, 1999. 5 [Image at PDF link] Figure 1: Seismic recordings on E-W component at Palisades for events at World Trade Center (WTC) on September 11, distance 34 km. Three hours of continuous data shown starting at 08:40 EDT (12:40 UTC). Data were sampled at 40 times/s and passband filtered from 0.6 to 5 Hz. Two largest signals were generated by collapses of Towers 1 and 2. Eastern Daylight Time (EDT) is UTC minus 4 hours. Expanded views of irst impact and irst collapse shown in red. Displacement amplitude spectra in nm-s from main impacts and collapses shown at right. Sampling is done for 14-second time windows starting about 17 s after origin time. Note broadband nature of spectra for collapses 1 and 2. Their signals are similar with a correlation coeficient of about 0.9 as are those for two impacts. 6 [Image at PDF link] Figure 2: Seismograph stations and topography for greater New York City area. Solid triangles indicate stations that recorded events at WTC (solid red circle); black circle, epicenter of earthquake of January 17, 2001. N.B. denotes Newark basin; H.H., Hudson Highlands; M.P., Manhattan Prong. 7 [Image at PDF link] 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. 8 [Image at PDF link] Figure 4: Comparison of Palisades seismograms for collapse 2 and earthquake of 17 January 2001. Arrows at left indicate computed origin times. 9
What ground? You mean the 20-story pile of rubble?
#52. To: misterwhite (#51)
The bathtub.
1WTC rubble pile with 7WTC in the background. The picture is before the fall of 7WTC. Again, no 20 story rubble pile in sight. As the towers could not be constructed upon an earthen bed of soil, about a 12 acre area was excavated. The result was called The Bathtub. There was a (relatively) shallow bathtub for 5 & 6 WTC, and the deep bathtub contained 1,2,3, and 6. 7WTC was outside the bathtub on the other side of Vesey St. The large towers (1&2) were constructed on bedrock. The excavation went down 70 feet. This included a massively reinforced wall along the west side facing the Hudson River, and the whole thing was a huge reinforced encasement. The collapse of the two towers created no hole in the ground. They were not constructed on the ground but in the bathtub atop bedrock. No significant damage was done to the bathtub. The rubble piles from the towers were relatively insignificant at ground zero and not 20 storys tall (nearly 250 ft). http://www.womanhonorthyself.com/?p=12174 There was a 100-ft piece of latticework that remained standing until brought down on 9/11.
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#19. To: no gnu taxes, Deckard (#16)
The firemen at the scene could see the building was going to collapse because of the damage it received.
"Other than initiating the fires in WTC 7, the damage from the debris from WTC 1 had little effect on initiating the collapse of WTC 7."
#22. To: nolu chan (#19)
#38. To: no gnu taxes (#22)
Skeptic121
FAQs - NIST WTC 7 Investigation
11. In a video, it appears that WTC 7 is descending in free fall, something that would not occur in the structural collapse that you describe. How can NIST ignore basic laws of physics?
#40. To: nolu chan (#38)
"A building cannot achieve gravitational acceleration (free fall) in collapse unless there is some force, in addition to gravity, applied."
#41. To: misterwhite (#40)
Large chunks of rubble, which were in free fall, were clearly falling faster than the rest of the twin towers.
6. How could the WTC towers collapse in only 11 seconds (WTC 1) and 9 seconds (WTC 2)—speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)?
#43. To: nolu chan (#41)
"NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2."
#44. To: misterwhite (#43)
Which exterior panels? Panels from the top of the building? If those panels peeled away, then yes, they'be be in freefall. You can see large chunks of rubble, which ARE in free fall, clearly falling faster than the rest of the building.
#45. To: nolu chan (#44)
"The picture does nothing to explain how the building collapse achieved free fall acceleration."
#46. To: misterwhite (#45)
Huh? The picture demonstrates that the building was NOT in free fall. The debris (which IS in free fall) is 20 stories below the top.
A Refutation of the Official Collapse Theory
B.S., Civil Engineering
M.S., Engineering Mechanics (Applied Physics)
Ph.d., Materials Engineering Science 6. How could the WTC towers collapse in only 11 seconds (WTC 1) and 9 seconds (WTC 2)—speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)?
As documented in Section 6.14.4 of NIST NCSTAR 1, these collapse times show that:
Other than initiating the fires in WTC 7, the damage from the debris from WTC 1 had little effect on initiating the collapse of WTC 7. The building withstood debris impact damage that resulted in seven exterior columns being severed and subsequently withstood fires involving typical office combustibles on several floors for almost seven hours. The debris damaged the spray-applied fire resistive material that was applied to the steel columns, girders, and beams, only in the vicinity of the structural damage from the collapse of WTC 1. This was near the west side of the south face of the building and was far removed from the buckled column that initiated the collapse. Even without the structural damage, WTC 7 would have collapsed from fires having the same characteristics as those experienced on September 11, 2001. The transfer elements such as trusses, girders, and cantilever overhangs that were used to support the office building over the Con Edison substation did not play a significant role in the collapse of WTC 7.
#47. To: nolu chan (#46)
"If the building was not in free fall, how did it get down in 9 seconds?"
#48. To: misterwhite (#47)
Because it took longer than 9 seconds.
3.6 ABSOLUTE TIME ACCURACY
#49. To: nolu chan (#48)
"You cannot extend the time unless the recorded phenomena were incorrectly or falsely reported."
#50. To: misterwhite (#49)
"You cannot extend the time unless the recorded phenomena were incorrectly or falsely reported."
Oh, please. Because of all the dust, no one knows when the building stopped falling.
Again, the seismic chart is subject to interpretation. Some say the chart shows a collapse in 8.4 seconds. Believe that?
It’s not a mainstream view, but some sites do claim that the towers fell in faster than freefall speeds (that’s usually specified as something like 8.4 seconds). They didn’t just make this figure up, either -- it comes from looking at the seismic record of the collapses.
Who are you?
The times listed for the major events in the FEMA report (McAllister 2002) were based on seismic signals (and analysis) recorded by the Lamont-Doherty Earth Observatory (LDEO) of Columbia University at a location 21 miles from the WTC site in Palisades, New York. These signals have subsequently been reanalyzed by LDEO, working under a contract from the NIST WTC Investigation. (Kim, 2005) A reinterpretation of the types of seismic signals received resulted in slightly revised times for the major events. The results of this recent analysis are also included in Table 3-1. The uncertainty for the first aircraft impact on WTC 1, the collapse of WTC 2, and the collapse of WTC 1 were reported by LDEO to be 1 s, while that for the aircraft impact on WTC 2 is 2 s. Recalling that uncertainties for times of the major events based on the television broadcasts are estimated to be 1 s, it can be seen from Table 3-1 that the two aircraft impact times derived by NIST and LDEO now agree within the combined uncertainties.
Seismic Waves Generated by Aircraft Impacts and Building Collapses at World Trade Center, New York City.
#51. To: nolu chan (#50)
"One knows when the building HIT THE GROUND"
Replies to Comment # 51. What ground? You mean the 20-story pile of rubble?
#53. To: misterwhite (#51)
What ground? You mean the 20-story pile of rubble?
End Trace Mode for Comment # 51.
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