What is the range of the richter scale?
The moment magnitude scale that seismologists use now for medium-to-large quakes is sometimes miscalled the Richter scale (for quakes in the 4-6 range moment magnitude and Richter magnitude values are about the same). As far as I know it doesn’t have a theoretical upper limit, though the largest earthquake ever measured had a moment magnitude of 9.5. It’s not used for quakes smaller than 3.5 or so, because it doesn’t distinguish well between SMALL quakes.
