How far away can the Richter scale be used?

The Richter scale is primarily used to measure the magnitude of earthquakes, and it is most effective for small to medium-sized earthquakes occurring within about 600 kilometers (approximately 373 miles) of the measurement site. For very large earthquakes, the scale's accuracy diminishes at greater distances, making it less reliable beyond this range. In practice, seismologists often use other scales, like the moment magnitude scale (Mw), for more distant and larger seismic events.