Christchurch Canterbury and New Zealand Earthquakes.
Energy release by an earthquake in Joules is given by
P = 10 
((magnitude * 1.5) + 4.8) 
Earthquake Magnitude that can be produced by a specific amount of energy in Joules
is given by
magnitude = 
(log10(P)  4.8 ) 


1.5 
M = 4.33 + 1.49 Log( L )
M = Magnitude on Richter scaleI = 1.41 Ms  1.18 ln R  0.0044 R + 2.18
I = Intensity of the Modified Mercalli scaleModified Mercalli scale to G force
A close fit for Modified Mercalli scale to G force can be achieved with
G = 

+ 
I 




100000 
1000 