The scale now used to measure earthquakes after the Richter scale is the Moment Magnitude Scale (Mw). The Moment Magnitude Scale has largely replaced the Richter scale because it provides more accurate measurements for medium to large earthquakes globally. Unlike the Richter scale, which is based on amplitude measurements from a specific type of seismograph, the Moment Magnitude Scale is based on the seismic moment, a physical measure that combines the area of the fault rupture, the average slip on the fault, and the force required to move the fault. This scale does not saturate during very large earthquakes, making it more reliable for strong seismic events. The Moment Magnitude Scale values correspond closely to Richter values for smaller earthquakes, but it is the preferred scale for significant events of magnitude 4 and above. The numerical values on the Moment Magnitude Scale are logarithmic, as with the Richter scale, with each whole number increase representing about a 32-fold increase in energy release.

In summary, the Moment Magnitude Scale (Mw) is the modern standard scale used to measure earthquakes after the Richter scale, offering greater accuracy and applicability for large earthquakes worldwide.