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10/25/1996 07:00:00

Caltech Seismo Lab Gets Location Data on October 3 Meteor

PASADENA— Caltech seismologist Kate Hutton has some data that shows where the October 3 meteor may have landed. She's providing the information publicly to help anyone and everyone who wants to try for the $5,000 reward UCLA is offering.

According to Hutton, any larger chunks from the meteor that lit up the Western skies on the night of October 3 may have landed in the Rose Valley area near Little Lake. Hutton figured this out by analyzing data from 31 of the seismic stations belonging to the Southern California Seismographic Network (operated by Caltech and the U.S. Geological Survey).

"As it fell, the atmospheric drag caused the meteoroid to explode in midair at least twice," Hutton says. "The explosions generated sound waves in the air similar to a sonic boom, which were detected by the seismographs.

"Using a procedure that is very similar to the one used to locate earthquakes underground, I used the arrival times of the sound waves at the various seismic stations to estimate where the explosions occurred."

Two of the explosions were well located, Hutton adds. Both were 20 to 30 miles above the Fivemile Canyon area in the eastern Sierra foothills. The explosions were separated by about 25 seconds, and the second was about five miles lower and about a mile further eastward than the first one.

Based on this data and on eyewitness accounts provided by John Wasson of UCLA and Caltech alumnus Mark Boslough of Sandia National Laboratory in New Mexico, Hutton thinks that any larger fragments that survived the fiery entry into Earth's atmosphere would have landed to the east-northeast of the explosions, perhaps in the Rose Valley area near Little Lake. Smaller fragments may have fallen more or less straight down from where the explosions occurred.

The Little Lake area would probably be the more seductive area to search, and for a very good reason. UCLA has offered a $5,000 reward for the first fragment that weighs at least four ounces.

Hutton says the seismographic instruments didn't pick up a meteorite impact on Earth, but this is not surprising, since a single fragment would probably have to weigh several tons in order for its impact to be detected.

The term "meteorite," by the way, refers to chunks of extraterrestrial debris that survive the entry into the atmosphere and end up on the ground. "Meteoroids" are chunks that travel through space, while "meteor" is the proper designation for the light show produced by a rock from outer space slowing down in Earth's atmosphere.

Any surviving meteorite fragments would probably have a fresh black matte crust. If the meteorite struck something on the ground, part of the crust might have chipped off to reveal a lighter interior. If anyone finds a meteorite fragment weighing at least four ounces, he or she should get in touch with Dr. John Wasson at UCLA. Wasson's e-mail address is wasson@igpp.ucla.edu.

Written by Robert Tindol