Living With Rock Bursts
On January 10th 2015 at approximately 5:37pm and 5:49pm many people in Sudbury felt the ground shake. Initially this shaking was reported as two earthquakes both with a magnitude of 3.2 on the richter scale. It was later found that the shaking was actually caused by what are known as rock bursts.
So, what is the difference between an earthquake and a rock burst?
Earthquakes are naturally occurring geological events caused by movement in the earth’s crust along faults or as a result of volcanic activity. Rock bursts are releases of pressure causing shaking as a result of mining activity. The rock in the earth’s crust is constantly under pressure from all sides the deeper you go the higher the pressure on the rock, this is what is known as confining pressure. By mining underground, we open up spaces, creating zones of low pressure surrounded by rock under high pressure. If the rock near the walls of the low pressure zone is not strong enough, it can fail.
Rock bursts are not uncommon in areas where lots of mining occurs and are usually very mild, however stronger rock bursts like the ones felt on January 10th can happen. Modern mining practices are safer than ever, and there is a lot of research going on around the world to predict and even prevent rockbursts in mines.