![]() ![]() That distance is about 384 feet (12 feet per story times 32 stories). The South Tower's roof to the level of the 78th floor of five seconds. Visible as a two-story band on the adjacent North Tower.Ī small extrapolation gives a good estimate of the time of fall of Up to the moment it gets swallowed up by the dust cloud.Īt that point the dust cloud rises only slightly above the level Using that marker it is possible to time the fall of the South Tower's top That immediately precedes the first large ejections from the southeast face. The level of the impact zone about three-quarters of the way back The highest point of the roof is the northwest edge.Īt about 2.5 seconds, the top starts to fall.Ī good marker for this is a small white squib that emerges from The fall is preceded by a leaning movement that starts at aboutĪt somewhere between two and three seconds, the top starts to fall. Since the roofline is obscured by smoke when the fall begins. Unfortunately this time is difficult to determine The moment downward movement of the highest point of the roof starts. This NBC video taken from east of the Towers.įor the South Tower we define onset of collapse as Is more difficult, its top is visible for longer and offersĪ longer span through which to time the rate of fall. The case of the South Tower is complicated by the fact that the top leansįor a few seconds before beginning its vertical descent.Īlthough determining the onset of vertical collapse in the South Tower Which initiates its telescoping collapse in an instant. The time of onset of collapse is clear in the North Tower, Was caused by building remains hitting the ground. Is consistent with the theory that the largest movement The fact that only strong S waves were reported Would have generated strong P waves in addition to S waves. ![]() However, bombs, if detonated underground, The fact that the largest movement is followed by smaller movementĭetonated at the starts of the collapses,Ĭontributed to the smaller subsequent movement. The main difference is that for WTC 1 the initial high-amplitude phaseīuilds in intensity to a much higher spike than any seen for WTC 2. Seconds before the onsets of the high-amplitude movement. In addition there is some still weaker movement starting about 12 In both cases there is about five seconds of high-amplitude movement,įollowed by about three seconds of movement at less than half that amplitude,Īnd then by about 15 seconds of much weaker movement. They show a very similar pattern for the leveling of WTC 1 and 2. Of the closest seismic recording station, at Palisades, NY (PAL). However, the signals may correspond to only parts of the collapse events, With the durations of the collapses themselves. The durations of the large signals are widely equated Show a large signal for each collapse lasting just under 10 seconds. Seismic records of the Twin Tower collapses Have been repeated by both proponents and critics of the official explanation. Statements that the Towers fell in eight and ten seconds Treated the durations of the largest seismic signals In-depth analysis of the seismic records, Whose descent can be timed using video records.ĭespite the availability of detailed studies of collapse times based on theĬompositing of video and photographic evidence, Remaining centered around the Tower's axis.Įach cloud had a fairly well-defined top and bottom, Of the waves of destruction that traveled down each Tower.Įxhibiting the behavior of pyroclastic flows associated with volcanoes,Įach cloud consumed its Tower's top in a few seconds, It is also possible to track other features Show that each Tower's top began its fall precipitously,Īnd show the falling tops for a few seconds before they disappeared May not be possible, but there are measurements that can be made. It took close to 15 seconds for the destruction to reach the ground.Įstablishing a precise time of duration for each fall However, video evidence of the North Tower collapse suggests that This estimate appears to be based mainly on seismic data. It is widely accepted that both Towers completely fell (nearlyĮverything but the dust reached the ground) in around ten seconds. The time it took the Towers to fall may be one of the most The Towers' Tops Fell Virtually Unimpeded ![]()
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