Moment magnitude is a number that indicates the strength of an earthquake. It is related to the energy released during the earthquake. A Japanese seismologist (scientist who studies earthquakes) named Hiroo Kanamori designed the moment magnitude scale of numbers in 1977. This scale is an improvement of the Richter magnitude scale, which American seismologist Charles F. Richter invented in 1935. In both scales, the stronger the earthquake is, the higher is the magnitude. The Richter and moment magnitudes are nearly identical for most earthquakes with a magnitude less than 7. However, moment magnitude measures the strongest earthquakes more accurately.