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The Case for Controlled Demolition - Seismographic Evidence

Seismic Information

Seismology Group
Lamont-Doherty Earth Observatory, Columbia University
Palisades NY 10964
Version of 9/14/01

          Seismograph stations in southern New York, northern New Jersey, western Connecticut, and Pennsylvania, operated by the Lamont-Doherty Earth Observatory of Columbia University, recorded the collapse of each of the towers of the World Trade Center on Tuesday morning September 11 and the subsequent collapse of 7 World Trade Center later that afternoon. The closest station, at Palisades, New York, is located 21 miles (34 km) north of lower Manhattan in Rockland County. This station also registered the impacts of the two airliners that crashed into the towers. 
          The signals generated by the collapsing North and South towers were much larger than those from the two airliner impacts.  The signals generated by the collapse of Building 7, however, were smaller than those of the impacts.  In addition, many smaller signals were registered at Palisades throughout the rest of the day that may have originated from the further collapse of the Twin Towers and the fall of walls and other debris in the surrounding area.
The Palisades recordings of the Twin Tower collapses were comparable in size to the signals from a small earthquake of seismic magnitude 2.4 that was felt in the east side of Manhattan and in the western parts of Queens earlier this year, on January 17.
          The seismic signals from the five events on 11 September differed from a small earthquake in that they were richer in low-frequency energy and poorer in high-frequency energy.  These differences can be attributed to the short time duration of the fault rupture responsible for the earthquake as compared to the long and complex collapse of the buildings. The seismic waves from the five World Trade Center events resemble those produced by the collapse of a salt mine south of Rochester, in 1994.
The catastrophic events at the World Trade Center, as might be expected, producedmuch larger seismic effects than the bombing of the World Trade Center in 1993. The seismic effects of the collapses are comparable to the explosions at a gasoline tank farm near Newark on January 7, 1983, which were detected up to 130 miles away.
 The seismographic stations are part of the Lamont-Doherty Cooperative Seismographic Network, which is operated in conjunction with several other institutions and is supported by the U.S. Geological Survey under the National Earthquake Hazard Reduction Program.  As part of its agreement with the USGS, Lamont-Doherty makes this data available upon request without restriction.
Preliminary measurements made by Lamont-Doherty analysts are summarized in the Table below:

Data from Columbia University Seismology Group
Date Origin
Time (UTC)
(Richter scale)
09/11/2001 12:46:26±1
0.8 sec
12 seconds
first impact
09/11/2001 13:02:54±2
0.6 sec
6 seconds
second impact
09/11/2001 13:59:04±1
0.8 sec
10 seconds
first collapse
09/11/2001 14:28:31±1
0.9 sec
8 seconds
second collapse
09/11/2001 21:20:33±2
0.7 sec
18 seconds
Building 7 collapse

Location of the World Trade Center is 40.71°N and 74.01°W. 

Other seismic information:
Seismograms recorded by LCSN Station PAL (Palisades, NY)
New York Earthquake, 10/27/2001 
Seismograms recorded by LCSN Station PAL, 10/27/2001
How long did the ground rumble?
Vibration of the ground following the plane impact of WTC1.


Vibration of the ground at the time of the WTC1 "collapse."
So, if it takes at least 9.22 seconds for the roof to hit the ground,  how could the ground quit rumbling after 8 seconds?
==>>  Consider the picture below.
I don't think this part of the building made a thud when it hit the ground.
Perhaps here, the only use of gravity was to get the dust out of the air.
There should be pulverizing or pancaking;  not both.
From Earthquake in Pakistan
Source of photo:  Rolling Stone, Issue 988, December 1, 2005  Page 80.
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