BogusBlake said:
The last two are some crazy "Seismic Crew" vehicles I saw on the way out.
Those are called thumper trucks. They use them to create seismic waves that are reflected off the layers. Different materials have different reflectivity and impedance. That's how they find oil and gas mostly now, but also water and just generally get a picture of the earth underneath. Yeah, my old man spent some time at Eielson AFB back in the 1960s, I've heard bits and pieces about reflective seismology. Put it this way, you can also create a seismic wave using great big underground nuclear blasts and so sitting a Airman geologist in a little hut in Alaska, you
might say, oh, be able to tell how big that particular blast was and where it originated...