Search

The Northern part of Algeria is considered to be the most active seismogenic area in the Western Mediterranean region. This area has a rich history of seismicity and had experienced many destructive earthquakes such as the Chlef (1954), El-Asnam (1980), Beni-Chograne (1994), Aïn-Temouchent (1999) and recently Boumerdes (2003) earthquakes. The earthquake of Aïn-Temouchent on December 22, 1999, was of magnitude 5.7, killed at least 28 people and made thousands of families homeless. Consequent damage was seen in all the structures located in a radius of 30 km. In the city of El-Maleh, located 12 km northeast of Aïn-Temouchent, the 'The National Bank Branch' of El-Maleh suffered moderate damage, but enough to justify questions about its safety. The project of rehabilitating this building required a broad analysis of its static and dynamic, past and present behaviors. The study reported in this paper was a necessary preliminary step toward the development of an optimal retrofit solution. [ABSTRACT FROM AUTHOR]

Seismic hazard in terms of spectral acceleration ( SA) has been estimated for the first time in northern Algeria. For this purpose, we have used the spatially-smoothed seismicity approach. The present paper is intended to be a continuation of previous work in which we have evaluated the seismic hazard in terms of peak ground acceleration ( PGA) using the same methodology. To perform these evaluations, four complete and Poissonian seismic models have been used. One of them considers earthquakes with magnitudes above M S 6.5 in the last 300 years, that is, the most energetic seismicity in the region. Firstly, seismic hazard maps in terms of SA, at periods of 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5 and 2.0 sec, with 39.3% and 10% probability of exceedance in 50 years, have been obtained. Therefore, uniform hazard spectra ( UHS) are computed and examined in detail for twelve of the most industrial and populated cities in northern Algeria. All the reported results in this study are for rock soil and 5% of damping. It is noteworthy that, in the seismic hazard maps as well as in the UHS plots, we observe maximum SA values in the central area of the Tell. The higher values are reached in the Chleff region (previously El Asnam), specifically around the location of the destructive earthquakes of September 9, 1954 ( M S 6.8), and October 10, 1980 ( M S 7.3). These maximum values, 0.4 g and 1.0 g, are associated with periods of about 0.2 and 0.3 sec for return periods of 100 and 475 years, respectively. [ABSTRACT FROM AUTHOR]