Earthquake duration magnitude (Md) for earthquakes recorded on short-period vertical seismographs. Numerous studies determined the relation between coda duration and magnitude for different regions of the World. According to a recent study by Mandal et al. (2004), previous studies showed that duration magnitude estimation is quite stable for local earthquakes ranging from magnitude Md 0.0 to 5.0. In two most recent investigations using statistically stable samples for Italian earthquakes [approximately 100,000 events over the period 1981-2002 in the Richter local [ML] magnitude range of 3.5-5.8] and for Indian earthquakes exemplified by an aftershock sequence of 121 events with (surface wave magnitude) > 4.0
Richter magnitude scale distance of the station, formula_23. In practice, readings from all observing stations are averaged after adjustment with station-specific corrections to obtain the formula_2 value. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released, and each increase of 0.2 corresponds to approximately a doubling of the energy released. Events with magnitudes greater than 4.5 are strong enough to be recorded by a seismograph anywhere in the world, so