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Permalink Reply by TM on January 18, 2014 at 2:35pm

Essentially, thumper trucks come equipped with a large metal foot, which stomps on the ground. The action creates seismic waves that bounce off the rocks below and are then recorded and measured by instruments on the ground. This information is then sold to drilling companies to help determine the best place to drill for gas or oil.

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Permalink Reply by MJ on January 18, 2014 at 3:25pm

The instruments are called geophones and are usually strung up and down the roadsides when they siesmic the roads.  I believe these same geophones are used across land when they do explosive siesmic work as well.  They are usually strung together with long fiberoptic cables.  Orange in color is what I have seen mostly and taped across road intersections.  I have read that this service can cost upwards of $75,000 per mile!  Just adding my 2cents...

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Permalink Reply by Mary on January 19, 2014 at 12:31am

Here is Westmoreland County, we are already (Marcellus horizontals) HBP and McDonald Land Services is contacting us as they 'need on our property to perform seismic testing' for Chevron. First off, it doesn't make sense that they want to come on our property after the fact. Second, they are offering $1 per acre. About 95% of my property are heavily wooded. How in the world do they expect to be able to drive these Thumper Trucks through my woods? Any thoughts greatly appreciated.

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Permalink Reply by Ragnars Repo on January 19, 2014 at 4:11am

Not all seismic testing is done this way. In my area they used helicopters to drop in all the testing equipment across the area they are testing. Ground crews walk into the fields and woods setting up the receiving equipment. Small charges are placed at specifies distances, once detonated they create the sound waves required to provide the information. The crews bag up the equipment and the choppers take it to the next location.

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Permalink Reply by Jim Litwinowicz on January 19, 2014 at 12:05pm

Mary; they may be doing more seismic to look at other strata. Or maybe they will be drilling more in to the same strata. Also, could be doing a study of fracking results so they know more for the next job.

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Permalink Reply by john p halloran on January 21, 2014 at 6:50am

They drill holes in the ground and drop dynamite in them and detonate it which causes the sound waves they need!!!

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Permalink Reply by The Hiker on January 19, 2014 at 2:21am

r2d2:  Ultrasonic?  In one closeup, you could just barely see the dust being raised at the edge of the "foot".  Thanks for the video.

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Permalink Reply by Steven A Joliat on January 19, 2014 at 4:37am

The signal transmitted into the bedrock is variable low frequency generally below 300 Hertz.  Higher frequencies are absorbed by the layers of rock and are not reflected back to the surface to be measured by the geophone arrays.  Technically the trucks pictured are referred to as vibroseis trucks, not thumpers which use a different technique for generating the signal.  Vibroseis technology was first deployed for commercial use by Conoco in the 1950s.  www.aapg.org/explorer/2007/02feb/vibroseis.cfm provides some more information on the technology.

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Permalink Reply by The Hiker on January 19, 2014 at 6:18am

Interesting article.  Thanks.   They downplay any potential damage to surrounding structures with the light bulb and egg trick, but do say a homeowner may experience vibrations similar to the kids rough-housing on the carpet...

300 Hz is about the frequency of the high E on a guitar...just for reference.....rough-housing would seem to indicate a much lower frequency.

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Permalink Reply by Steven A Joliat on January 19, 2014 at 8:22am

Yes, 300 HZ would be the maximum of the frequency range that is in the signal.  Much more of the signal is composed of lower frequencies which can be as far down as  10 HZ or less.

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