Cycle sismique et aléa sismique d'un réseau de failles actives : le cas du rift de Corinthe (Grèce)

Abstract : The Corinth rift (Greece) is one of the regions with the highest strain rates (16 mm/y extension rate) in the Euro-Mediterranean area and as such it has long been identified as a site of major importance for earthquake studies in Europe (20 years of research by the Corinth Rift Laboratory and 4 years of in-depth studies by the ANR-SISCOR project). This enhanced knowledge, acquired in particular, in the western part of the Gulf of Corinth (CRL region), an area about 50 by 40 km2, between the city of Patras to the west and the city of Aigion to the east, provides an excellent opportunity to compare fault-based (FB) and classical seismotectonic (ST) approaches currently used in seismic hazard assessment studies. An homogeneous earthquake catalogue was thus constructed for the purpose of this study along with a comprehensive database of all relevant geological, geodetical and geophysical information available in the literature and recently collectedwithin the ANR-SISCOR project. The homogenized Mw earthquake catalogue is composed of data from the National Observatory of Athens and from the university of Thessaloniki as well as data acquired through historical and instrumental work performed within the ANR-SISCOR group for the CRL region. A frequencymagnitude analysis confirms that seismicity rates are governed by Gutenberg-Richter (GR) statistic for 1.2=6 earthquakes were computed for the region of study. Timedependent models (Brownian Passage time and Weibull probability distributions) were also explored. The probability (normalized by area) of a M>=6.0 earthquake is found to be greater in the CRL region compared to the eastern part of the Corinth rift. Probability estimates corresponding to the 16th and 84th percentile are also provided, as a means of representing the range of uncertainties in the results. Probability estimates based on the ST-approach are then compared to those based on the FBapproach approach. In general ST tends to overestimate probabilities of occurrence compared to FB estimates along slow slipping faults and underestimate them along faster moving faults (e.g. Psathopyrgos, Aigion). The FB approach in this region is still affected by a high degree of uncertainty, because of the poor constraints on the 3D geometries of the faults and the high uncertainties in their slip rates and maximum magnitude. Thus, for example, the Psathopyrgos fault is the fault that shows the highest probability (12%) of hosting a M>=6.0 event in the next 30 years, however, the associated uncertainty is also the greatest (5%-27%). Finally, the cumulative seismic moment rate of the faults is comparable to the seismic moment rate estimated from the earthquake catalogue. Interestingly, the overall seismic moment rate of the CRL region shows a deficit of 50+/-20 % when compared with an estimate of the equivalent geodetic moment rate. This suggests an important component of aseismic deformation.
Keywords : Corinth Rift Greece
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Aurélien Boiselet. Cycle sismique et aléa sismique d'un réseau de failles actives : le cas du rift de Corinthe (Grèce). Sciences de la Terre. Ecole Normale Superieure de Paris - ENS Paris, 2014. Français. ⟨tel-01456400⟩

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