 Location of the pentagon and the USGS seismic station CBN. |
At approximately 9:38 am EDT (13:38 GMT) American Airlines
flight 77 from Dulles to Los Angeles struck west side
of the Pentagon. The jet, which was a Boeing 757, penetrated
through several of the rings in the Pentagon and started
a tremendous fire. A search for seismic records from the impact
proved difficult. This is likely due to the nearly
horizontal approach to the building; prelimary analysis indicated
that the impact might have produced a seismic
signal that was recorded at the USGS station CBN, but later
work showed this not to be the case. The best work on the forensic
seismology of the impact is by Dr. Kim, and can be found at
this link.
Location of the pentagon and the USGS seismic station CBN.
A satellite image of the damage at the pentagon from the IKONOS satellite and Space Imaging is available here
Seismogram 1: Recording of energy orignally thought to be from the
collision of Flight 77 with the Pentagon at USGS seismic station
CBN. The energy is dominately surface wave energy, and gives a back azimuth
roughly consistent with the pentagon, later work showed that this is
an unrelated event.
