 Complete the following phrase:  Earthquakes, even if they were thousands of miles away, did cause strong enough movements in the magnets to negatively affect the beam quality and even disrupt it. Therefore, tiltmeters were installed on Tevatrons magnets to monitor minute movements and to help identify the cause of problems quickly. The first known earthquake to disrupt the beam was the 2002 Denali earthquake, with another collider shutdown caused by a moderate local quake on June 28, 2004. Since then, the minute seismic vibrations emanating from over 20 earthquakes were detected at the Tevatron without a shutdown, like the 