EVALUATION PROBABILISTE DE L’ALEA SISMIQUE DANS LA PARTIE NORD EST DE L’ALGERIE

Abstract

The objective of this thesis is the application a probabilistic model in order to infer a maximum acceleration of ground motion in a given site, then the different parameters such as the probability of exceedance as well as the mean annual rate of exceedance and consequently the different return periods. The idea consists in evaluating for a given earthquake, the maximum credible magnitude (Mmax) and distance r from the source. The estimation of the maximum acceleration depends on attenuation model adapted to the seismotectonic context of the region of study and a poissonian catalog of events. This latter is established in order to characterize, since a zoning model, the seismic activity by a Gutenberg –Richter law which gives the number of earthquakes for each source area by integrating the historical and instrumental data. The possible maximum magnitude is also regarded as a parameter of seismicity. However to estimate it according to the probabilistic approach, we suppose thet the analytical from and the parameters of the model of occurrence of the earthquakes are known. The application of methodology, on some zones in the northeastern of Algeria, made in it possible derives the curves for the probabilities of exceedance of acceleration and estimate the returns period. This latter enabled us to make a hierarchical classification of the zone according to their seismic activity.