Probabilistic analysis of seismic hazard in Portugal

In this paper probabilistic models to be applied to seismic hazard analysis in Portugal are evaluated. To characterize the seismic process of occurrence, data on instrumental and historical earthquake catalogue, for the Portuguese region, were considered. The geographical area of analysis was subdivided into seismic source zones, taking into consideration the earthquake history, and the knowledge about tectonic processes causing seismic activity. In each zone the instrumental earthquake time sequence, without aftershocks, was modelled as a Poisson process. The Gutenberg–Richter law was the magnitude–recurrence relationship used to describe the frequency of earthquakes within a range of different sizes or magnitudes over a period of time. To characterize the strong ground motion process the Data Base on Macroseismic Information of Continental Portugal was used. The macroseismic intensity was selected as the ground motion parameter to be used as dependent variable in attenuation relationships. The segmentation of data considering source mechanisms and site soil conditions was attempted. The attenuation models were estimated applying multiple regression techniques. Finally the evaluated models were applied to assess the seismic hazard in Portugal and the results were presented as seismic hazard curves and maps.