Ground Motion Parameters Estimation In Northern Algeria

This study focuses on ground motion parameters. Peak ground acceleration (PGA) and spectral acceleration (SA) for different periods of oscillation and damping at 5%, which are estimated in northern Algeria, using the spatially-smoothed methodology. First, seismic hazard maps in terms of ground motion parameters, as well as in terms of PGA and SA, with 10% probability of exceedance in 50 years, have been obtained, using the spatially-smoothed seismicity. The procedure used allows us to examine in details the contribution within the estimation of seismic hazard of the last major earthquake M6.8, which occurred near the Algiers city on 21 May 2003. A preliminary seismic hazard zonation in northern Algeria, in terms of PGA, has been carried out based on seismic hazard map for a return period of 475 years. All the results reported in this study are for rock soil and 5% damping ztetyui In the second part, uniform hazard spectra (UHS) are computed and examined in detail for twelve of the most industrial and populated cities in northern Algeria. It deserves to be remarked that, in the seismic hazard maps as well as in the UHS plots, we observed maximum PGA and SA values in the central part of the Tellian Atlas. The higher values are in the Chleff region (previously El Asnam), specifically, in the vicinity of the Quaternary Basin, around the location of the destructive earthquake of September 9, 1954 (Ms6.8) and October 10, 1980 (Ms7.3). These maximum values are associated with period of 0.32s for a return period of 475 years. Also, we have obtained in this part of the Tellian Atlas, seismic hazard values about 40% higher than previous one (Pelaez and al., 2003), specifically in the Zemmouri-Boumerdes-Algiers area, corresponding to the contribution of the destructive earthquake of 21 May 2003, (Hamdache and al., 2004b).