PROGRAMA DE CALCULO ELECTRONICO PARA LOCALIZACION DE SISMOS PROXIMOS EN LA REGION DE LA PENINSULA IBERICA (THE ELECTRONIC COMPUTER PROGRAM FOR LOCALIZATION OF NEAR SEISMIC IN THE IBERIAN PENISULA REGION),
INSTITUTO GEOGRAFICO Y CATASTRAL MADRID (SPAIN)
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The paper describes the computer program for epicentral determination, EPICO, which has been prepared for a IBM 1620. The program is based on another of the University of Saint Louis U. S. A., presenting several variations especially, the computation for the critical distances corresponding to foci in different layers of the assumed model of the crustal structure. The output shows the standard deviation of the travel time, from data of 19 stations, by means successive approximations following the Geiger method to a preliminary epicentral determination and for each hipocentral depth, till reaching a difference in time lower than that which have been given in the input, or SD lower than 2 sec, and through three trials as a maximum. The program processes the number of hipocentral depths proposed in the input, and uses a crustal structure model with 4 velocities and 3 thicknesses. The program eliminates the stations which error is higher than 1.5 SD, and also those stations exceeding 1000 km, in epicentral distance. This last distance is sufficient, in general, for the earthquakes in the Iberian Peninsula, which are recorded on the local stations. The output lists the epicentral coordinates, origin time, the standard deviation, station names and arrival time, epicentral distance, travel time and its deviation, and also the parameters corresponding to the crustal structure model, focal depth and particular identification of the epicenter.