PSN-L Email List Message

Subject: Re: Geophone layout
From: Doug Crice dcrice@............
Date: Thu, 20 Jan 2000 06:39:49 -0800


The standard method of measuring ice thickness is ground-penetrating
radar.  Not only does it work well, you can even do it from a

You can also do it with geophones using standard seismic reflection
methods, though it would be harder.  A second problem is that the
velocity of sound waves in glacier ice may be less well defined than
that of microwaves.  The name of the technique is a seismic reflection

The University of Toronto has a perfectly good Department of Geophysics,
where you will find the equipment and expertise to use either method. 
Start by visiting your library and opening up any book with "Geophysics"
in the title.  There is no doubt information on the Internet as well,
but some problems are better solved at the library because it's harder
to find tutorial information on the internet.

I am not familiar with any work on ice thickness with seismic, but visit
the web site of the Society of Exploration Geophysicists and
look into their data base of articles.  If the full article isn't there,
they will be in your library.

A geophone is a vibration transducer with a moving coil and magnet that
senses velocity (as opposed to acceleration).  They are more sensitive
than accelerometers at the low frequencies encountered in seismic.

Good luck.

Thomas wrote:
> Hi everyone,
> I am 4th year student working a project using geophones to measure ice
> thicknes. Is there a special method to layout the geophones to get an
> accurate profile an induced vibration? The purposal is to generate an
> acoustic pulse through possibly several kilometers of ice and have the
> geophones detect this pulse and derive the ice thickness. Would anyone have
> suggestions on a detonation mechanism? I've heard people use 1 kg of
> dynamite for 1 km of ice.
> As you can see, I am not too familiar with geophones but I do know they work
> like an accelerator. If anyone knows of a good book, please suggest it
> because none of our group members are geology people.
> Thanks alot for your time.
> Thomas Looi
> Aerospace Engineering
> University of Toronto
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Doug Crice
19623 Via Escuela Drive		      phone 408-867-3792
Saratoga, California  95070  USA	fax 408-867-4900


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