Richter magnitude scale Richter magnitude scale The so-called Richter magnitude scale – more accurately, "Richter's magnitude scale", or just "Richter magnitude" – for measuring the strength ("size") of earthquakes refers to the original "magnitude scale" developed by Charles F. Richter and presented in his landmark 1935 paper, and later revised and renamed the Local magnitude scale, denoted as "ML" or "M". Because of various shortcomings of the ML scale most seismological authorities now use other scales, such as the moment magnitude scale (), to report earthquake magnitudes, but much of the news media still refers to these as "Richter" magnitudes. All magnitude scales
Richter magnitude scale used by astronomers. Second, he wanted a magnitude of zero to be around the limit of human perceptibility. Third, he specified the Wood-Anderson seismograph as the standard instrument for producing seismograms. Magnitude was then defined as "the logarithm of the maximum trace amplitude, expressed in microns", measured at a distance of 100 km. The scale was calibrated by defining a magnitude 3 shock as one that produces (at a distance of 100 km) a maximum amplitude of 1 micron (1 µm, or 0.001 millimeters) on a seismogram recorded by a Wood-Anderson torsion seismograph. Finally, Richter calculated a table of distance