I guess it makes sense that a geologist would draw maps in the dirt, huh? Below is the U.S. Geological Survey geologist Michael Rymer explaining the layout of the sensors for this experiment (which looks amazingly similar to the graphic a couple of web pages back ) to Yong Gang Li.
Below is a photograph of the drilling rig that was used to drill the two shot holes. The holes were 24 meters deep and 20 centimeters in diameter. They were lined with a metal tube the full diameter, and the full length of the hole. About 135 kilograms of explosives were lowered into each hole. The casings were then filled back up with dirt.
Below is a photograph of the South Shot Hole. The tube is the top of the casing and the yellow wire is the detonation cord leading down to the explosive. The white object is a GPS antenna for the DAS that was placed next to the hole to record the shock waves from the explosion. Since this DAS was 'right there' the data recorded by it would be used for accurate timing of the explosions.
Below is the sensor that was connected to the DAS and buried to record the explosion. The top of the casing is in the extreme upper right hand corner.
Below is the shot box. It generates the electrical signal that sets off the blasting cap that activates the detonation cord that sets off the explosive. It has a timer that is synchronized to a GPS clock so that the shots are fired at just the right time.
Boom! The black object about to be covered by dirt is the DAS in a plastic bag.
Below is Tom Burdette of the U.S. Geological Survey examining the casing. The force of the explosion lifted the casing that high out of the ground. This was a good shot. Sometimes the explosion can launch the whole casing (yes, all 25 meters of it) out of the ground! Before the explosion I was told to find a hiding place and to keep my eyes on the casing in case I had to use the hiding place. There have been other experiments where the explosion created a cavity that caused the ground around the hole to sink. After the shots Tom used a welding torch to cut off the casings at ground level.
The last five meters or so of the South Shot Hole were drilled through wet ground. This generated a lot of out gassing (mostly of carbon dioxide and steam) both from the area around the casing and from cracks in the ground formed near the hole. Below is a photograph of two areas about 10 centimeters in diameter where very fine dust 'bubbled' up out of the cracks. The explosions that we set off were recorded by the Global Seismic Array as earthquakes with magnitudes of 2.0.
DIRECT LINKS TO PAGES:
ON THE ROAD AGAIN
THE WORK BEGINS
THE GREAT OUTDOORS
VALLEY OF THE TEXANS
BOMBS AT THE BOMBING RANGE