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Politics : Bush-The Mastermind behind 9/11? -- Ignore unavailable to you. Want to Upgrade?

To: GUSTAVE JAEGER who wrote (6069)	4/21/2004 11:33:41 PM
From: Lazarus_Long	Read Replies (1) \| Respond to of 20039

pulling-down of the WTC towers "Pulling down"? So what's your theory now? They attached cables to the towers, had a plane slam into each one, then had tractors pull the towers down? It's rather odd that none of them has had anything to say about it... Uh, well, actually, they did. On September 11, seismographs operated by Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, recorded seismic signals produced by the impacts of the two aircraft hitting the Twin Towers of the World Trade Center and the Towers' subsequent collapse. While the ground shaking was consistent with the energy released by small earthquakes, it was not sufficient to cause the collapse of or damage to the surrounding buildings, as some have thought. Rather, the buildings around the Twin Towers were impacted both by the kinetic energy of falling debris and by the pressure exerted on the buildings by a dust- and particle-laden blast produced by the collapse. Writing in the November 20 issue of Eos, published by the American Geophysical Union, seismologists from Columbia's Lamont-Doherty Earth Observatory outline the sequence of seismographic recordings on that tragic day, and argue that vibrations recorded on September 11 were of a magnitude thought to be too low to cause structural damage to buildings, especially in the northeast region of the United States. columbia.edu volcanolive.com SEISMOLOGICAL INFORMATION RECORDED AND ANALYZED Similar to the Oklahoma bombing, seismological devices recorded the explosions and the collapse of the WTC. In this article, you will find links that will provide visual reference and related data about seismological information during the WTC attacks. Magnified waveforms of the WTC attacks can be found Here. A REPORT: SEISMOLOGICAL OBSERVATION OF IMPACTS AND COLLAPSES AT WORLD TRADE CENTER Prepared by: Seismology Group Lamont-Doherty Earth Observatory, Columbia University Palisades NY 10964 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, produced much 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: Information Based on Seismic Waves recorded at Palisades New York Event Duration origin time (EDT) Magnitude (hours:minutes:seconds) (equivalent seismic) Impact 1 at North Tower 12 seconds 08:46:26±1 0.9 Impact 2 at South Tower 6 seconds 09:02:54±2 0.7 Collapse 1, South Tower 10 seconds 09:59:04±1 2.1 Collapse 2, North Tower 8 seconds 10:28:31±1 2.3 Collapse 3, Building 7 18 seconds 17:20:33±1 0.6 firehouse.com THose seismograph tracings: ldeo.columbia.edu