LKAB constantly monitors seismic activity. It does this with hundreds of instruments called geophones that detect shock waves in the bedrock.
LKAB constantly monitors seismic activity. It does this with hundreds of instruments called geophones that detect shock waves in the bedrock.
Using their readings, both the strength and exact location of an event can be calculated. This is the reason LKAB does not measure event magnitude on the Richter Scale but uses a local scale. The Richter Scale is designed to measure natural earth tremors at great distance. It was initially created specifically for the San Andreas fault in California and is thus not suitable for the special conditions in mining. In addition to magnitude, LKAB measures vibrations in structures using the unit millimetres per second. Read more about the local scale LKAB uses for measurement.
Seismic activities cannot be predicted precisely; major events that are felt in communities can occur at any time day or night. On the other hand, our instruments show if overall seismic activity is increasing or diminishing at an orebody, and if necessary LKAB may choose to stop production until activity falls off. LKAB is also researching other ways to reduce seismic activity, e.g. by planning blasting and how mining takes place level by level. Statistics show that seismic activity increases somewhat during the spring, which may result from the increase in water flow during the thaw acting as a lubricant that allows bedrock fractures to slide more easily, thus reducing strength.
Seismic events may be clearly felt by residents in the communities close to LKAB's underground mines. However, what is felt are not landslides or falling boulders but shock waves that occur when large bodies of rock grind against one another, twist or break free releasing energy. Nevertheless, such tremors may cause boulders in the mine to come loose, but this is unusual as LKAB has adapted its rock reinforcement to capture rock movements. LKAB never mines ore beneath areas where people live or spend time, so any seismic activity takes place inside a mine's industrial area.
Reporting
LKAB posts information on its website in connection with major seismic events stating the time, location, magnitude and the biggest vibration. It may take an hour or two as the readings from the instruments must first be collected and checked. We also send a report to the civil authorities.
You can read more about the information flow step for step here.