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Re: The Hector Mine Earthquake, 10/16/1999

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I have a question that maybe someone could help me with.  I work at a plant
in Louisiana.  Approx. 2 hours after the Hector earthquake, we registered
sloshing in two of our larger water tanks.  None of our seismic
instrumentation registered anything at that time, and it was properly
working.  We have checked in our area (heavily industrialized), and there
were no reports to the sheriff of any explosions, etc.

Is it possible that these large tanks of water could have "registered" some
of the vibrations from the Hector earthquake?

It does not seem likely, but I am being pestered with questions from our
operators, and I really don't know what to tell them.


Greg Ferguson

-----Original Message-----
From: sasquake [mailto:sasquake(--nospam--at)]
Sent: Monday, October 18, 1999 8:22 PM
To: seaint(--nospam--at)
Subject: The Hector Mine Earthquake, 10/16/1999 Greg,

It's quite possible it was related to the Hector Mine Earthquake.  During the 1992 7.3 Landers earthquake, we experienced sloshing of water in water tanks here in Portland.  Those Landers quakes triggered other earthquakes at very large distances and also excited the Geysers north of San Francisco.  In these large and very large magnitude earthquakes, the earth literally rings like a "bell".  The motion is very long period, of course; because the higher frequencies are damped out and attenuated with distance.  Your instrumentation is probably set to trip at 0.1 g or something like that, if it is accelerometer driven.  But if you check with the nearest university where they have a seismology department, or your state geological survey; they can probably give you the rest of the story.  The thing to look for is the local seismogram at the time of the sloshing, if it exists.

Hope this helps,

James Bela
Oregon Earthquake Awareness TM        /        The Quake NorthwestTM
"We Have Nothing To Fear But Shear Itself        /        "We're All Subducting In This Together"