Why is moment magnitude used by scientists but not by the media and other non-scientists? What is the difference between moment magnitude and Richter magnitude?
Different magnitude scales were developed to take into account different types of available data (e.g., recordings from different types of instruments and seismic wave types most pronounced at different distances). Different magnitude scales are usually valid only within a certain magnitude range and when based on specific types of recording instruments. Magnitudes estimated using different scales should be equal where the scales overlap, however. Although it technically has a very specific meaning, “Richter magnitude” generally is used incorrectly by the press to mean a generic “magnitude.” “Moment magnitude” best reflects the earthquake’s physical characteristics (like the area of fault surface that broke and amount of movement that occurred across it) The USGS has now decided to use only moment magnitude, but just say “magnitude” when reporting to the press and public.
