Seismicity, seismic input and site effects in the Sahel—Algiers region (North Algeria)

Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this Capital city, a realistic modelling of the seismic ground motion (SGM) is conducted by using the hybrid method that combines the finite differences method and the modal summation. For this purpose, a complete database of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone [2.25°E–3.50°E, 36.50°N–37.00°N] is performed and an earthquake list, for the period 1359–2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross sections have been built up to model the SGM in the city, caused by the 1989 Mont-Chenoua and the 1924 Douéra earthquakes. Synthetic seismograms and response spectral ratio is produced for Algiers, and they show that the soft sediments in Algiers centre are responsible of the noticed amplification of the SGM.     

Seismic hazard evaluation at Algiers using Benouar's earthquake catalogue

This paper presents the evaluation of seismic hazard at the site of Algiers (capital of Algeria). In order to implement earthquake-resistant design codes, it is usually necessary to know the maximum dynamic load which a particular structure might experience during its economic life, or alternatively, the most probable return period of a specified design load. The evaluation of the seismic hazard at the site, based on peak ground motion acceleration and using Cornell's method and Benouar's earthquake Maghreb catalogue, in terms of return period, probability of exceedance of PGA, design ground motion and a response spectrum, is carried out for the City of Algiers and its surroundings. The response spectrum for Algiers presented in this paper is the first one realized in Algeria using revised Algerian data.     

Seismicity and Tectonic Structures in the Site of Algiers and its Surroundings: A Step Towards Microzonation

— We intend to reappraise the seismogenic potential of the geologic structures in the site of Algiers and its surroundings. A compilation of a working earthquake catalogue is first made using all events reported in all previous documentation available. However for the sake of homogeneity and a certain degree of reliability of the data, only revised seismic events with epicenter coordinates, magnitude and/or intensity are included. A tectonic setting of the zone under investigation and available fault plane solutions are presented. The results obtained in previous seismological studies of the most recent earthquakes of the area are also discussed. The findings highlight the great interest to be taken in the detailed and timely assessment of the seismic hazard of Algiers and its surroundings which is made possible by the realistic modelling of the scenario seismic input.