What scale replaced the Richter scale for measuring large earthquakes?

The scale that replaced the Richter scale for measuring large earthquakes is the moment magnitude scale. Written as Mw, it calculates an earthquake's size from seismic moment, which reflects the fault area that ruptured, how far the rocks slipped, and the rocks' rigidity.

Charles F. Richter and Beno Gutenberg developed the local magnitude scale in the 1930s for particular instruments and earthquakes in Southern California. That scale works well for smaller, nearby events, but it saturates for very large earthquakes: its readings stop increasing proportionally even when the earthquake releases much more energy.

The moment magnitude scale, developed through work by Hiroo Kanamori and Thomas Hanks in the late 1970s, does not have that same upper-limit problem and is now the standard for comparing major earthquakes worldwide. News reports still often say “Richter scale,” but modern scientific reports generally mean moment magnitude.