My cohort in crime, the Principal Investigator (PI), for this experiment was Susan Hough from the U.S. Geological Survey office in Pasadena, California. Our first morning in Indio we loaded up our field vehicle -- the family Taurus station wagon -- and headed for the desert.
About 30 miles south of Indio, which for some reason seemed like about 300 miles when you were driving it, were several instruments designed to measure the movement of the ground. One of the larger instruments of the desert was a laser strain meter operated by Caltech which stretched across the ground for what looked to be about 500 meters.
This was, technically, a portable instrument that had been turned a couple of different directions during its life. It was used to measure the deformation of the earth caused by the tides. The air is removed from the tube and a laser is turned on. The beam is split in two. One beam travels down the length of the instrument to a mirror where it is bounced back to the end where it originated and fed to a sensor. The other beam of light does not travel down the tube, but is sent to the same sensor as the other beam where they recombine. If the two beams recombine "in phase" then we have the original laser beam back, but if the distance between the source of the laser and the mirror at the far end of the tube changes by just millionths of an inch the light waves of the two beams recombine "out of phase". The amount that the beams are out of phase can be directly measured by a change in the intensity of the recombined light beam. Simple. This strain meter is operated by Frank K. Wyatt of Caltech. Below is one of the guys doing some work on the instrument when we made it to the location of our first station.
Running beneath and perpendicular to the instrument above is, well, another one. This one is buried.
Along the tube, seemingly in the middle of the desert, there was a hatch.
Down the hatch was an equipment room. It looked to me like a buried shipping container to me. A large vault protected from the heat, animals, and people with electricity made it the perfect place to set up our equipment.
The vacuum pump used to evacuate the air from the tube.
2018-03-05