The Richter Scale is designed to measure natural earth tremors at very great distance. In a mine you want to know more accurately where a vibration has happened, a more precise scale is therefore required.
The Richter Scale is used to measure natural earth tremors. These are normally measured over great distances and the incidents have a large magnitude and low frequencies. When measuring seismic activity in a mine the magnitude is lower, the frequencies higher and you want great precision at short distances. This is why a local magnitude scale is produced for the conditions that apply at the specific mine. By preparing a formula for the local magnitude calculation you may choose an individual scale or arrive close to an "earth tremor scale". LKAB has chosen the latter but does not express itself in the Richter Scale. LKAB and other mining companies the world over that monitors mining seismics express themselves in special local scales.