# What is the exact and official formula for Richter Scale Logarithm Formula?

Jun 29, 2010
in
Earthquake Questions

because there are so many formulas, i dont know which one is the known official one.

is it MAGNITUDE=log(intensity/intensity of standard earthquake)?

if it is, what is a standard earthquake?

thx pls help! math pw P

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One comment

J on June 29, 2010 at 11:13 pm

The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs: M_L = log(A) – log(Ao(δ))

where A is the maximum excursion of the Wood-Anderson seismograph, the empirical function Ao depends only on the epicentral distance of the station, δ.

However, the moment magnitude scale (abbreviated as MMS; denoted as Mw) is now used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of the area that slipped. The scale was developed in the 1970s to succeed the 1930s-era Richter magnitude scale (ML). Even though the formulae are different, the new scale retains the familiar continuum of magnitude values defined by the older one. The MMS is now the scale used to estimate magnitudes for all modern large earthquakes: Mw = (2/3)log(Mo) – 10.7

where Mo is the magnitude of the seismic moment in dyne centimeters (10−7 Nm).