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Re: (meteorobs) Fwd Query: Impact from New Zealand fireball?
In a message dated 99-07-09 19:26:23 EDT, you write:
Rob<<
With large fireballs that penetrate low in the atmosphere, the sonic booms
are so intense that ground coupling of the sound causes seismometers to
shake. It is a common fallacy that a seismometer recording means an
impact. It would only be a large body relatively close to a seismometer
that would be recorded as an impact, not a run of the mill football sized
object at many kilometer distance.
>>
This reminds me of when my brother who was also a fireman here in California
for many years. He is now medically retired from an incident. Anyhow, one of
his assigned stations (either at Pinyon Flats or Anza..dot can't remember which
now?), had a seismograph operated by CalTech secured there. Every once in
awhile they come along to check it out in a very insulated vault. While
there, my brother told me that you can see the seismograph record trucks
driving along a road. I believe they have a way of adjusting truck movements
out of the recorders? Once I contacted Caltech in an attempt to find a
seismograph track of the fireball that made a very loud sonic boom over
Descanso in 1992. They told me then that they couldn't find any signature of
the sonic boom from three of the closest seismograph stations in this area.
They also told me that they had a problem with re entering space shuttles in
the mojave when they make their sonic booms of re entry. They somehow
adjusted their monitors so that these seismographs won't record space shuttle
sonics. I don't know if this is only for certain seismograph stations near
mojave or all of them?
GeoZay
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