On Friday, April 18, at approximately 4:37 a.m., a 5.2-magnitude earthquake shook southern Illinois. It was the second strongest quake in the area in 40 years. Its vibrations were felt across the state, including at Fermilab.
Seismometers at the laboratory recorded the pre-dawn vibrations. Although there were no reports of damage, scientists said they likely would have lost the particle beam inside the Tevatron accelerator if it had been running.
The plot at left shows the reading from a tilt meter that recorded the slight back-and-forth motion of a single Tevatron magnet during the earthquake.
The one at right shows ground motion recorded by the on-site seismometer.
Read more about the quake in Friday's Chicago Tribune article.
