World Trade Center Seismic Signal

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World Trade Center Disaster Raw Seismic Data

World Trade Center Jet Impacts

World Trade Center Jet Impact Seismic Signals

Explosions Occurred In Each Tower Almost Simultaneously With Each Jet Impact

World Trade Center Towers Demolition Seismic Signal

World Trade Center 7 Demolition Seismic Signal

Did the Earth Shake Before The South Tower Hit the Ground?:

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.

Editors note: The 1993 World Trade Center Truck Bomb was 1500lbs which is 0.75 tons of explosive.

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.

The timeline of the major events is summarized in Table 1.1. The times and seismic data were recorded at the Lamont-Doherty Earth Observatory (LDEO) of Columbia University. The signal duration and Richter Scale magnitudes were included to indicate the relative magnitudes of energy transmitted through the ground between the events. Figure 1-8 shows the accelograms recorded by the observatory during the events.

These times are based on seismographs operated by Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y., 21 miles north of the city. The calculations account for the 17 seconds it takes a seismic wave to travel to Palisades, said Dr. Won-Young Kim, a seismological researcher at Lamont-Doherty. The first time is about two minutes earlier than has been widely and incorrectly reported by The New York Times and others. Because that had to be estimated, the impact time could be off by two to three seconds, but no more, Dr. Kim said.

Event Times As Recorded At Lamont-Doherty Earth Observatory:

WTC1 Impact: 8:46:26 a.m. (31,586s) American Airlines Flight 11 The kinetic energy of Flight 11 when it hit the North Tower (WTC1) was about 2358 MJ. source

WTC2 Impact: 9:02:54 a.m. (32,574s) United Airlines Flight 175 The kinetic energy of Flight 175 when it hit the South Tower (WTC2) was about 3585 MJ. source

WTC2 (South Tower) Demolition: 9:59:04 a.m. (35,944s - 32,574s = 3370s = 56min 10s after impact)

WTC1 (North Tower) Demolition: 10:28:31 a.m. (37,711s - 31,586s = 6125s = 102min 5s after impact)

World Trade Center Roof Line Downward Motion Start Times From Video Analysis





Seismograms recorded by LCSN Station PAL (Palisades, NY) (34km from the WTC Towers):


Four seismogram traces showing the two hours of seismogram recorded at Palisades (PAL), New York. Each trace is 30 minutes long. The first trace starts at 08:40 (EDT), second trace starts at 09:10 (EDT), third at 09:40 and the last trace starts at 10:10 (EDT; 14:10 UTC). Notice the seismic signals from the first impact at 08:46 EDT, second impact at 09:03 (very small), two large signals due to collapse of the World Trade Center buildings at 09:59 and 10:28 (EDT). We understand from news reports, that the first impact (0846 EDT) resulted in the second collapse (1028 EDT), and the second impact (0903 EDT) resulted in the first collapse (0959 EDT). Source:


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 first impact and first 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 coefficient of about 0.9 as are those for two impacts.

Broadband channels BHZ, BHN, and BHE: These three channels are sampled 20 times per second and record higher frequencies, which is useful for viewing local or regional earthquakes. Each of the bands has three components, Z for vertical motion, E for east-west motion, and N for north-south motion. Source:

EHE: Short Period 100 sps (

09/11/01 Seismic Activity Overview:





On 9/11 Protec field technicians were utilizing portable field seismographs to continuously record ground vibrations on several construction sites in Manhattan and Brooklyn for liability purposes. STUDY 8-06 w clarif as of 9-8-06 .pdf implosionworld.com_p5 [Article-WTC_STUDY_8-06_w_clarif_as_of_9-8-06_unlocked.pdf unlocked]

Protec was operating portable field seismographs at construction sites in Manhattan and Brooklyn on 9/11, and these seismographs were recording ground vibration throughout the timeframe of events at Ground Zero. These measurements, when combined with more specific and detailed seismic data recorded by Columbia University’s Lamont-Doherty Earth Observatory, help to provide an unfiltered, purely scientific view of each event. STUDY 8-06 w clarif as of 9-8-06 .pdf implosionworld.com_p2 [Article-WTC_STUDY_8-06_w_clarif_as_of_9-8-06_unlocked.pdf unlocked]

As our report states, Protec was engaged in vibration monitoring activities on private construction sites in Manhattan and Brooklyn on 9/11. Because these portable field seismographs were not physically installed and manned on the Ground Zero site, we do not feel it is appropriate, nor scientifically possible, to categorically state that data from these monitors alone can specifically prove or disprove the existence of an explosive catalyst. In general, portable field seismographs are far less technologically advanced than permanently installed instrumentation such as the monitors at Columbia University’s Lamont-Doherty Earth Observatory, which is why we chose to comment in detail on the Columbia University data before commenting on the Protec data. For example, the Columbia seismographs can pinpoint a relatively accurate geographic location for a vibration event, (i.e., “this event likely occurred at or near Ground Zero”), whereas portable field seismographs do not possess this capability. However, that said, the fact that the Protec monitors were activated and recording does appear to have some value in that they did not record vibration spikes that could be even remotely associated with explosive events during the timeframe in question. STUDY 8-06 w clarif as of 9-8-06 .pdf implosionworld.com_p12 [Article-WTC_STUDY_8-06_w_clarif_as_of_9-8-06_unlocked.pdf unlocked]

"Firstly the buildings were subject to violent impact as each aircraft hit with a force that would have collapsed most buildings. Some idea of the magnitude of the impacts is gained from the earth tremors they caused – measured at 0.7 and 0.9 on the Richter scale for earthquake intensity at a seismic station 34 kilometres from Manhattan. The significance of these values is that, unlike an earthquake that occurs at considerable depth in the earth’s crust causing wide–spread seismic forces, these impacts were very localized, occurring several hundred metres above ground, before being transmitted through the structures to their foundations and into the subgrade. The fact that such large disturbances were measured at such a distance is testimony to the force of the impact." -Leigh Wilson

Construct In STEEL Australian Institute for Steel Construction 2001-09-30 - The collapse of the World Trade Center Towers, New York (link)

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