## PSN-L Email List Message

Subject: Re: tornadoes and earthquake detection
From: "Geoff" gmvoeth@...........
Date: Fri, 2 Dec 2005 15:30:45 -0700

```> I will have to pull the data off backup and look at this. How would this
> register on the seismometer?

I would expect any periodic thing to register similar
to a sine wave and be detectable by an FFT program
and if you are able to integrate your data
over time you might be able to see intelligence
that is below the noise level.
The bandwidth of such a signal would probably be quite wide.
The rotation of a tornado is a periodic event.

>> If the tornado was traveling at 60mph
>> then the rotational speed was probably
>>
> The weather "specialists" with government weather station in our area
> estimated the wind speeds of around 300 mph

If the windspeed is 300mph and the forward speed is 60 then
from the center and if the diameter is 0.75 miles then
the rotational period should be about 12441f circum/352fps or
35 seconds per rotation.
I expect the actual scenario in three dimensions to be considerably more
complex then this but this represents the best idea I can visualize
in my crazy brain.

I find it amazing that if a tornado f5 passes over a given
point the wind speeds measured across the center
is in the transonic range I can not imagine any
structure withstanding transonic wind velocities
across itself. Funny things happen in the transonic
ranges because gas compressional effects have their way.
If you look at the edges of a tornado you will see
a heat like shimmer seemingly related to index of refraction
changes and I suspect this is the rotational area you would
be interested in knowing the windspeed of.
Air density is probably most intense at some radius
with a slight vacuum in the center due to centrifugal/centripetal forces.
You want to look at the radius where this air density is compressed
against the inrushing air inorder to guess what rotational rate to see on a seismogram.

I have pondered these ideas over a considerable length
of time but have no use for any of them.
Maybe one of you seismic gurus can invent a tornado detector
using a seismometer and a fft program somehow.

The only thing I can imagine is building a home
uaing aircraft construction techniques
half underground in the shape of a flying saucer
to stand up to these tremendous wind forces.

:-)
gmvoeth

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