PSN-L Email List Message

Subject: Seismic Energy Source
From: "Doug Crice" dcrice@............
Date: Sat, 23 Jul 2005 07:11:24 -0700

Doug Crice
Wireless Seismic  
12996 Somerset Drive                phone 1-530-274-4445
Grass Valley,  CA  95945  USA    fax 1-530-274-4446
I have greatly enjoyed this discourse on a better exploration seismic
source, and look forward to more ideas.  To kind of remind folks of the
specifications, I would like to repeat and expand them.

1) A person ought to be able to carry it around (and be air mobile by
regular air freight).
2) It needs reasonably high frequency output (ping instead of thunk)
3) Build it for $1000-$2000 (cost, not sales price) in lots of 10 units,
using commercially available and machined parts and normal labor rates.
4) It should be safe, even when used by students
5) There should be no significant regulatory issues (a problem with
dynamite, the perfect source)
6) Operating supplies available in third world countries.
7) It needs to work better than a sledgehammer used with a seismograph =
can stack multiple impacts.
8) Because the source will probably be used in a repetitive fashion, it
needs a reasonably fast cycle time (many seconds, not many minutes).
9) The seismic signature should approximate a zero phase wavelet, which =
as a
practical matter; means the energy prior to impact should be =
10) Good ground coupling is needed. In the case of a sledgehammer, a =
plate is placed on the ground as a target. In the in-hole shotgun, a =
hole is
augured just big enough to hold the device below the soft topsoil and
preferably watered.

The crossbow idea is equivalent to the "elastic wave generator", powered =
the large rubber band. Existing units weigh a couple of hundred pounds, =
it's got me thinking about a portable version.

The variations on exploding bottles don't seem to meet the requirements =
reasonably safe operation. Sure, a careful user would be safe, but we =
talking about students and third-world laborers.

An earlier variation was the "vacuum assisted weight drop". It had a 6 =
ft (2
meter) long tube about 6 inches (15 cm) in diameter with a 100 pound =
bullet inside. The bullet was pushed up with air pressure, then =
When the tube was full of vacuum, it was released and accelerated by its
weight and by atmospheric air pressure. At the bottom was a 100 pound =
and plate combination pressed on the ground by the weight of the whole
mechanism. With equal weights for the piston and anvil, it didn't bounce
(think of that ball bearing toy). The VAWD worked reasonably well, but
weighed 1000 pounds and cost over $10K 20 years ago. Using air pressure =
the accelerant provided a nice signature, since the force was external =
the system, though when you released the piston, it instantly lost 100
pounds of weight, providing the equivalent of a negative sledgehammer =


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