'Sensitive' Seismometer Recorded Airwaves From Columbia Disaster

by Judy Long

Beginning in 1990, Baylor University geologists used a seismometer located north of China Spring to pick up readings from earthquakes and other significant earth movements from all over the world.
As the station's computer and telemetry equipment became obsolete, operation was gradually phased out. Recently, however, the geology department has installed a broad-band, three-component seismometer so sensitive that it recorded ground motions generated by pressure airwaves from the space shuttle Columbia disaster on Feb. 1. This was before the machine was even fully operational.
"The seismic equipment was temporarily sitting on the floor of the instrument shed but still managed to pick up seismic readings as the shuttle broke apart and debris fell to the ground," said Dr. Thomas Goforth, chair of the geology department. "Apparently, the pieces hurtling toward earth caused a complicated sonic boom which caused ground motions."
Although Baylor's seismometer records the waves from distant earthquakes, the site does not pinpoint the location of the epicenters.
"That's done by the U.S. Geological Survey. They use real-time data from many stations to make locations of epicenters and put the information on the Internet in a matter of minutes after the event," Goforth said.
The academic purpose of Baylor's station is to study seismic waves as they emerge in central Texas to determine the detailed structure of the crust and the upper mantle.
"This information has a number of uses," Goforth said. "One of these is to provide support data to help discriminate between nuclear tests and earthquakes. The results may be useful in determining whether the U.S. will sign the comprehensive test-ban treaty currently being considered."
Renovation of the Baylor site, which will be entirely solar-powered, is nearing completion. The project involved installing a cement vault, replacing all up-hole electronics, adding a digital converter and a new radio transmitter and antenna, and adding power circuitry to connect solar panels to storage batteries.
The new broad-band seismometer will enable the sensor to respond equally to movements over the frequency range of 0.01 to 25 hertz. The three-component aspect of the seismometer senses motion from three directions: vertical, east-west horizontal and north-south horizontal.
"This provides a complete three-dimensional description of the motion of the earth," Goforth said.
A similar site will be installed in the under-construction Baylor Sciences Building, a $103 million, 500,000-square-foot facility that will be open in fall 2004. One of the foundation piers has been sunk to the bedrock but decoupled from the sciences building. The seismometer will be attached to the pier, which will come up into the building.