Did a quarry blast cause a 3.2-magnitude tremor?
Early last week, a large tremor shook home and businesses in and around McCook, Illinois.
The 3.2-magnitude tremor was felt as far away as Wisconsin, according to a Chicago Tribune report.
Initially, reports pointed to a possible link between the tremor and a blast at the McCook-based Federal Quarry, owned by Lehigh Hanson. The quake enraged neighbors, many of whom have objected to the blasting for years.
However, the Chicago Tribune’s report notes that the quarry may not be to blame.
Though geophysicists at the U.S. Geological Survey have said the tremor was not caused by an earthquake, officials from the Illinois Department of Natural Resources have also noted that the shaking was not the result of the blast at the quarry.
The report also notes a 7-second delay between the blast and the tremor, and that the tremor had an earthquake-like force and the vibrations of a quarry blast.
Additionally, Lehigh Hanson and state DNR officials have said that the blast caused a PPV of .35 inches per second, while the second shake posted a PPV of 2.93 inches per second. The state-mandated limit is 1 inch per second.
Lehigh Hanson spokesman Jeff Sieg told the Tribune the quarry is still operating, though blasting has been suspended for this week.
As of Sunday, officials from USGS, the Illinois DNR and Lehigh Hanson were planning to meet to compare data to try to figure out what caused the tremor.