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
Logarithmic scale the value of a logarithm function. Here, a given logarithmic unit will be denoted using the notation [log "n"], where "n" is a positive real number, and [log ] here denotes the indefinite logarithm function Log(). Examples of logarithmic units include common units of information and entropy, such as the "bit" [log 2] and the "byte" 8[log 2] = [log 256], also the "nat" [log e] and the "ban" [log 10]; units of relative signal strength magnitude such as the "decibel" 0.1[log 10] and "bel" [log 10], "neper" [log e], and other logarithmic-scale units such as the Richter magnitude scale