Kanamori and American seismologist Thomas C. Hanks developed the moment magnitude scale which replaced the Richter magnitude scale as a measurement of the relative strength of earthquakes.
Because of the limitations of the magnitude scales, a new, more uniformly applicable extension of them, known as moment magnitude (MW) scale for representing the size of earthquakes, was introduced by Thomas C. Hanks and Hiroo Kanamori in 1977.
In 1979 the Japanese-American seismologist Hiroo Kanamori, professor of seismology at the California Institute of Technology and Dr. Hanks (then a graduate student at Caltech) suggested the use of Moment magnitude scale to replace the Richter magnitude scale for measuring the relative strength of earthquakes.