CENTRAL COLUMNS SEVERED
Videos of the North Tower collapse show its communication mast falling first,
indicating that the central support columns must have failed at the very
beginning of the collapse. Loizeaux told AFP,
"Everything went simultaneously."
"At 10:29 the entire top section of the North Tower
had been severed from the base and began falling down,"
Hufschmid writes. "If the first event was the falling of a floor,
how did that progress to the severing of hundreds of columns?"
Asked if the vertical support columns gave way before the connections
between the floors and the columns, Ron Hamburger, a structural engineer
with the FEMA assessment team said, "That's the $64,000 question."
Loizeaux said, "If I were to bring the towers down,
I would put explosives in the basement to get the weight of the building
to help collapse the structure."
Seismographs at Columbia University's Lamont-Doherty Earth Observatory
in Palisades, New York, 21 miles north of the WTC, recorded strange
seismic activity on September 11 that has still not been explained.
While the aircraft crashes caused minimal earth shaking, significant
earthquakes with unusual spikes occurred at the beginning of each collapse.
The Palisades seismic data recorded a 2.1 magnitude earthquake during the
10-second collapse of the South Tower at 9:59:04 and a 2.3 quake during
the 8-second collapse of the North Tower at 10:28:31.
The Palisades seismic record shows that -- as the collapses began --
a huge seismic "spike"
marked the moment the greatest energy went into the ground.
The strongest jolts were all registered at the beginning of the collapses,
well before the falling debris struck the earth.
These unexplained "spikes" in the seismic data lend credence
to the theory that massive explosions at the base of the towers
caused the collapses.
A "sharp spike of short duration" is how seismologist
Thorne Lay of Univ. of California at Santa Cruz told AFP
an underground nuclear explosion appears on a seismograph.
The two unexplained spikes are more than twenty times the amplitude
of the other seismic waves associated with the collapses and occurred
in the East-West seismic recording as the buildings began to fall.
Lerner-Lam told AFP that a 10-fold increase in wave amplitude
indicates a 100-fold increase in energy released.
These "short-period surface waves,"
reflect "the interaction between the ground
and the building foundation,"
according to a report from Columbia Earth Institute.
"The seismic effects of the collapses are comparable
to the explosions at a gasoline tank farm near Newark on January 7,
1983," the Palisades Seismology Group reported on Sept. 14, 2001.
One of the seismologists, Won-Young Kim, told AFP that the Palisades
seismographs register daily underground explosions from a quarry 20
miles away. These blasts are caused by 80,000 lbs.
of ammonium nitrate and cause local earthquakes between
Magnitude 1 and 2. Kim said the 1993 truck-bomb at the WTC
did not register on the seismographs because it was "not coupled"
to the ground.
Experts cannot explain why the seismic waves peaked before the towers hit
the ground. Asked about these spikes seismologist Arthur Lerner-Lam,
director of Columbia University's Center for Hazards and Risk Research
told AFP, "This is an element of current research and discussion.
It is still being investigated."
"Only a small fraction of the energy from the collapsing towers
was converted into ground motion," Lerner-Lam said.
"The ground shaking that resulted from the collapse
of the towers was extremely small."
Last November, Lerner-Lam said, "During the collapse,
most of the energy of the falling debris was absorbed by the towers
and the neighboring structures, converting them into rubble and dust
or causing other damage --
but not causing significant ground shaking,"
Evidently, the energy source that shook the ground beneath the towers
was many times more powerful than the total potential energy released
by the falling mass of the huge towers.