[Lowfer] Earthquake.

Sat, 20 Apr 2002 21:20:52 EDT

In a message dated 04/20/2002 1:43:15 PM Eastern Daylight Time, 
[email protected] writes:

> 
>  Guys,
>  
>  Isn't trying to draw a connection between earthquakes, Northern Lights, 
and 
>  80M activity a bit of a stretch?
>  
If someone were looking at just the right time, some low frequency signals 
may have been detected.

A quick Google Groups serach found the fololowing, along with muxh else on 
the topic.
........................................
In <4pigsd$[email protected]> [email protected] writes:
>From: Wayne Coulson <[email protected]> 
>   Because of plate tectonics the solid portion of the crust is
>   squeezed at some places and stretched at others.  The slow movement
>   will not cause an electromagnetic pulse, but a quick movement will.
>   Sudden movements in either compression or tension, maybe even
>breaking,
>   will thus cause a pulse.

Piezoelectricity is a fairly linear phenomenon. More stress makes
more voltage. A pulse is produced if the mechanical input is a 
pulse. Stress a piezoelectric crystal at a constantly increasing
rate and the voltage will be constant. 

Common quartz is not very piezoelectrically active, particularly in
fractured crystals as usually found in rocks. Otherwise we wouldn't
have to import the piezoelectric crystals used for computer clocks
etc. from Brazil and the other places where good piezoelectric
quartz is found.

>   Another example where this piezoelectric phenomenon occurs is above
>   erupting volcanoes.  This occurrance is called clear air lightning.
>   Clear air lightning occurs above dusty, not lava, volcanoes.

This has nothing to do with piezoelectricity, but is a function of
rapidly rising dust particles stripping charges off gas molecules
in the air and from each other as the eruption forces them higher.
Same as a Van de Graff generator but using rising gas as a carrier
instead of a rubber belt.

>   I'll bet, there will even be evidence found somewhere, to show that
>the 
>   Mount St. Helens event (preceeded, or at least concurrently)
>released
>   a rather large electromagnetic pulse.

Probably. But what does this show? We're interested in precursors,
not so much the artifacts from the eruption itself.

>   Electromagnetic waves/pulses travel at the speed of light, but
>crustal 
>   earthquake waves travel much slower. However, this does not explain
>the 
>   large time lags between the events.   

It doesn't? 186,000 miles/sec vs 2-8,000 feet/sec? 

>   I am now familiar with four such occurrences whereby gigantic
>pulses
>   have been released and detected:

I think you might want to check your sources a little more carefully,
and reconsider whether you mean to say "gigantic pulses". I am not
familiar with your first two examples but there can be all sorts of
physical pheonomena associated with an earthquake or volcano.

>         3. Loma Prieta in California: picked up by Anthony
>Frazier-Smith.

These signals are by no means gigantic. Extremely sensitive coil
sensors were used to pick up variations in the earth's magnetic
field on the order of 0.1 to 100 nanoTesla, with the earth's field
itself around 50 microTesla here. Fraser-Smith has published 
at least two comprehensive papers on this, as has Jack Dea of the
Navy lab in San Diego that is working on a similar system.

>         4. Kobe Japan 1/17/95 (in Scientific American 6/96 page 98)

Likewise this refers to very weak electromagnetic signals whose
origin is still unknown. 