Yep Cptbil, you are correct . . . . it's been around many a year. First time I saw it in use was early 70's in East Africa, in the desert. They used a LARGE truck with a BIG metal plate in back and they did indeed call it "Thumper" because that baby could thump the ground REAL good. That and dynamite were the two common ways to make the sound wave necessary to penetrate the earth's surface to the depths they wanted.
On this subject and at sea, I used to work in that field (oil exploration) and they used a similar system there (dynamite in the old days and later "Air Guns" that blast a sudden air charge under water to penetrate the sea bottom). It was often amazing to walk into the "Recording Room" and see the image of a sunken ship moving across the strip chart recorder. I often wondered if it was new sinking or an ancient one. We would glance at it and then go on with our work because we had no interest in anything other than oil and gas deposit structures, usually thousands of feet deep.
With todays technology, 3D images and color, it must really be amazing!!
Hobo
To All Concerned: 
