Testing at Lajitas

The Lajitas Lab Trailer.
A small 20x8 foot trailer serves as an onsite laboratory and sleeping quarters. The air conditioner (upper left) is an essential part of the equipment in an environment where temperatures may exceed 120 degrees F. During early testing and installation a full set of workstations and processing equipment was installed in the trailer. At other times, it has functioned as a classroom during training exercises, as dining quarters (when the hail is to heavy to enjoy the outdoors), and office.

Before installing all 9 elements, there were extensive tests performed at Lajitas. At the time a 24-bit 6 channel recording system (developed for the GSETT-2 tests) was delivering continuous seismic data to SMU's lab in Dallas. This system included short period and broadband three component seismometers in a surface vault. It also had the capability to record 7 additional 16 bit channels.

As a first experiment, a small 3 element mini-array was deployed using Spirl-4 cables. Vertical sensors were installed in shallow (2 foot) vaults about 1/4 mile from the existing central site. Data collected during this time confirmed earlier results that under quiet conditions, even at such short distances, the background noise shows little correlation.

The experiment also demonstrated the danger of a cabled system in the Lajitas environment. A nearby summer thunderstorm induced large currents on the cables, blowing components off of the surge protection boards and then fusing components in the power supply, analog preamps, and portions of the digital circuits. Induced currents from lightning would continue to be a problem through much of the testing program.

Closeup of field monitor
A field workstation running a real time data acquistion and viewing system is used to QC the data and perform instrument tests without interrupting the archival flow of data back to the Dallas lab.

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