| Forensic Seismology -- New
Mexico Pipeline Accident
Seismographs are sensitive to general disturbances
in the Earth and often record sonic or subsonic signals in the atmosphere
as well. The study of seismograms from crime scenes or tragic accidents
is called forensic seismology. (click images to view at full size)
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| During a deployment of IRIS PASSCAL (www.passcal.nmt.edu)
seismographs in 2000 (www.ees.nmt.edu/Geop/Ristra/ristra.html),
a natural gas pipeline explosion was recorded at distances as
close as 19 km and as far as 136 km. This tragic incident was
the deadliest pipeline explosion in the U.S. in 25 years, resulting
in 12 deaths. The photo shows the crater created by the pipeline
explosion. The seismic data from the explosion are a complex
record of the coupled seismic and acoustic signals generated
by the rupture, ignition, and ensuing fireball. These seismograms
constrain the precise timing of the rupture to within several
seconds, show that the initial rupture/ignition proceeded in
three steps, and record the progressive shutting down of the
pipeline after approximately 1 hour. The prolonged fireball
produced an unusual protracted signal through the turbulent
excitation of sound waves that were trapped near the ground
by an early morning temperature inversion. These sound waves
coupled with the Earth to produce strong seismic signals picked
up by the seismometers. For another illustration of forensic
seismology, see the October
2002 Image of the Week. |
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After: Koper, Wallace, and Aster, Seismic Recordings
of the Carlsbad, new Mexico Pipeline Explosion of 19 August, 2000,
Bulletin of the Seismological Society of America, in press, 2003.
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