Earthquake duration magnitude - is referred to as "earthquake duration". It is this concept that Bisztricsany first used to develop his Earthquake Duration Magnitude Scale employing surface wave durations. In 1965, Solovev proposed the use of total duration instead of the duration of surface waves. In 1972, Lee et al. used coda duration for the first time to estimate Richter magnitude of local Californian earthquakes. Based on their study, they suggested that it is appropriate to estimate the magnitude of local earthquakes using signal duration. More recently, the development in instrumentation led to the use of signal duration to estimate the coda magnitude
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