Michigan Meteor Helping Researchers Understand Near-Earth Object Threats

When the Michigan bolide traveled through and exploded in Earth’s lower atmosphere, it produced large shock waves and a variety of soundwaves, including waves in the low-frequency or infrasound range below 20 hertz. These waves were detected by infrasound microphones at seismic stations in the Central and Eastern US Network (CEUSN), deployed through the eastern half of the continental United States. The researchers were also able to detect the burst in seismic wave data collected by seven stations in Michigan, Ohio and Ontario.

Hedlin and colleagues made calculations from these data to determine the location, height, timing and yield of the bolide’s disintegration. They were able to compare these values with the “ground truth” for these characteristics as calculated by optical observations of the bolide taken from numerous cameras on the ground and from recordings by the Geostationary Lightning Mapper instrument on a National Oceanic and Atmospheric Administration (NOAA) satellite.

The infrasound and seismic calculations were consistent with the optical observations, the researchers concluded, although some of the calculations–such as the location and yield provided by infrasound data–contained a large amount of statistical uncertainty. The seismic data, however, were able to pinpoint the location and height of the burst within kilometers, in agreement with the optical data.

If the Michigan bolide is the smallest detectable event that can be measured using CEUSN data, researchers should be able to detect about 15 events of this size or larger each year in eastern North America, Hedlin and his colleagues write.

The Michigan analysis could also help researchers who study clandestine nuclear tests “make some inferences about how detectable similar-sized anthropogenic events would be–how far away from the explosion source we’d be able to detect signals, for example,” said Hedlin.

Contacts and sources:
Becky Ham
Seismological Society of America