CE3 Science Note: Richter vs. Moment Magnitude Scale
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Richter Scale
– Developed by Charles Richter in 1935 to compare local California
earthquakes.
– Based on the logarithm of the amplitude of waves recorded by single,
band-limited seismographs.
– Values saturate above 6.8, so it cannot distinguish among larger
earthquakes.
– Still used in the popular media.
•
Moment Magnitude Scale
– Developed in the 1960’s and 1970’s by Caltech seismologists Thomas
Hanks and Hiroo Kanamori.
– Has replaced Richter scale for scientific use.
– Has a sounder seismological basis; It estimates the earthquake “moment”the rigidity of the Earth multiplied by the average amount of slip on the
fault and the size of the area that slipped.
– Values compare well with Richter for small and medium sized
earthquakes, but it can differentiate larger earthquakes as well.
References
Wikipedia, Moment magnitude scale
(http://en.wikipedia.org/wiki/Moment_magnitude_scale)
Wikipedia, Richter magnitude scale
(http://en.wikipedia.org/wiki/Richter_magnitude_scale)