PSN-L Email List Message

Subject: RE: Modified sound card and datalogging and geophones
From: "Doug Crice" dcrice@............
Date: Thu, 21 Jul 2005 12:21:30 -0700

> Snip

I am using standard seismic sensors and I will probably use a .22 or .38
fired into the ground or a slide hammer lifted up by a blank cartridge. =
sledge hammer swinging days have been over for 20 years due to multiple

> unsnip

Shooting bullets into the ground is not the best energy source; most of =
energy goes into plastic deformation instead of elastic waves.  There =
was a
source made with an 8-gague kiln gun some years ago that generated a lot =
sound and fury, but barely kept up with a sledgehammer except when fired
into saturated material.=20

The best gun-like source is the buffalo gun aka "in hole shotgun".  You =
a 3/4-inch pipe about 4 feet long and screw a coupling on the end big =
to hold a shotgun shell.  You auger a hole in the ground and stick the =
with the shell down a foot or more.  Then you drop a pointed rod down =
pipe to detonate the shell.  The shell goes off underground and much =
more of
the energy is coupled to the soil.  It works about as well with blanks =
with loaded shells. Search for in-hole shotgun source on the web and you
will find some papers. The most descriptive here

There is a commercial version called the Betsy Seisgun, if you search =
you can see pictures of it, but the pipe version works just as well.=20

Doug Crice
Wireless Seismic  
12996 Somerset Drive                phone 1-530-274-4445
Grass Valley,  CA  95945  USA    fax 1-530-274-4446


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