seismic reccurency parameters

huangyhg

seismic reccurency parameters
i have to find the recurrency parameters used in the gumbel type iii (maximum likelihood-weibull) methodology for a catalog of earthquakes (needed for a seismic hazard analysis).
now, from what i understand the parameters are: w,m,u and lambda. and i have to find p(m)=exp[-((w-m)/(w-u))^1/lamda].
w-maximum magnitude;
u-the extreme value associated to the unit of time (????)
lambda-is giving the asimptotic curve to the superior part of the anual probability;
p-the probility of not obtaining bigger magnitudes than m.
who is u? how do i find lambda?
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