stationary seismic hazard analysis scripts added

src/StationarySeismicHazardAnalysis/Ret_periodGRU.m

@@ -0,0 +1,55 @@
+%   [m,T]=Ret_periodGRU(Md,Mu,dM,Mmin,lamb,eps,b)
+%
+% EVALUATES THE MEAN RETURN PERIOD VALUES USING THE UNLIMITED G-R LED 
+%   MAGNITUDE DISTRIBUTION MODEL.
+%
+% AUTHOR: Stanislaw. Lasocki, Institute of Geophysics Polish Academy of
+% Sciences, Warsaw, Poland
+%
+% DESCRIPTION: The assumption on the unlimited Gutenberg-Richter relation 
+% leads to the exponential distribution model of magnitude distribution 
+% from and above the catalog completness level Mmin. The shape parameter of 
+% this distribution and consequently the G-R b-value are calculated at 
+% start-up of the stationary hazard assessment services in the
+% unlimited Gutenberg-Richter estimation mode.
+%
+% The mean return period of magnitude M is the average elapsed time between
+% the consecutive earthquakes of magnitude M.   
+% The mean return periods are calculated for magnitude starting from Md up
+% to Mu with step dM.
+% 
+%INPUT:
+%   Md - starting magnitude for return period calculations
+%   Mu - ending magnitude for return period calculations
+%   dM - magnitude step for return period calculations 
+%   Mmin - lower bound of the distribution - catalog completeness level
+%   lamb - mean activity rate for events M>=Mmin
+%   eps - length of the round-off interval of magnitudes.
+%   b - Gutenberg-Richter b-value
+%
+%OUTPUT:
+%   m - vector of independent variable (magnitude) m=(Md:dM:Mu)
+%   T - vector od mean return periods of the same length as m
+%
+% LICENSE
+%     This file is a part of the IS-EPOS e-PLATFORM.
+%
+%     This is free software: you can redistribute it and/or modify it under 
+%     the terms of the GNU General Public License as published by the Free 
+%     Software Foundation, either version 3 of the License, or 
+%     (at your option) any later version.
+% 
+%     This program is distributed in the hope that it will be useful,
+%     but WITHOUT ANY WARRANTY; without even the implied warranty of
+%     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+%     GNU General Public License for more details, <http://www.gnu.org/licenses/>.
+% 
+
+function [m,T]=Ret_periodGRU(Md,Mu,dM,Mmin,lamb,eps,b)
+if Md<Mmin; Md=Mmin;end
+m=(Md:dM:Mu)';
+beta=b*log(10);
+T=1/lamb./exp(-beta*(m-Mmin+eps/2));
+end
+
+