EVALUATION OF SEISMIC HAZARD USING TECTONIC FAULT DATA: CASE OF BENI-CHOUGRANE MOUNTAINS (WESTERN ALGERIA)

Refas Soria,Safa Aissa,Zaagane Mansour,Hamimed Abderahmane,Souidi Zahera

doi:10.37190/msc192609

Abstract

Abstract: In the world, people are increasingly exposed to natural hazards such as earthquakes. To this end, seismic risk mapping remains an essential topic of study in order to minimize their destructive effects. These maps are needed for both seismic risk management and for the design of infrastructure. The challenge is to take into account local information provided by seismic sources (historical seismicity) as well as information related to active tectonic faults. In this article, we calculated the seismic risk in the Mascara Mountains (western Algeria) using the geo-metric characteristic of known faults. This study is based on an important collection of a tectonic database of these faults (Nature, geometry and geological context). This information is relevant for their seismic potential. Indeed, by including these formations we tried to compute the seismic risk this region characte-rized by weak seismicity. Our results show more or less alarming facts. Indeed, the magnitude values calculated are between 4.85 and 7.25, whereas the magnitudes obtained by experimental seismicity do not exceed 6 on the Richter scale. The values of the maximum ground acceleration (PGA) are between 0.03 and 0.28g. These results were compared with assessments made on the basis of historical seismicity; the maximum values obtained do not exceed 0.2 g. The higher values of magnitude calculated from the active faults is due to: (i) the nature of the faults (inverse, normal and strike slip), (ii) the geometry (length and depth) and (ii) that some of these faults may have an aseismic character.

Highlights

In northern Algeria, natural hazards usually have terrible consequences both physically and in terms of loss of life; their suddenness, their spatio-temporal occurrence, and their magnitude are the interesting characteristics that scientists devote considerable effort to studying to minimize their devastating effects
The seismic risk in the Beni-Chougrane Mountains was calculated on the basis of the geometric characteristics and the nature of the known active faults, using several models to determinate magnitude (Vakov 1996; Stirling et al 1996; Well and Copersmith 1994; Wenousky and Nuttli 1983; Dowrick and Rhoades 2004; Slemmons 1977; 1982; Ambraseys and Jackson 1998; Strasser et al 2010) and other models for evaluating Peak Ground acceleration (PGA) (Cornell 1968; Esteva and Rosenblueth 1964; McGuire 1976; Campbell 1981; 1988; 1997; Idriss 1982; Xiang and Gao 1994; Woodward and Clyde 1983; Ambraseys 1995)
The comparison of magnitudes and PGA calculated using spatially smoothed historical seismicity data and those directly derived from active faults gives significant and different results

Summary

Introduction

In northern Algeria, natural hazards usually have terrible consequences both physically and in terms of loss of life; their suddenness, their spatio-temporal occurrence, and their magnitude are the interesting characteristics that scientists devote considerable effort to studying to minimize their devastating effects. The Pliocene formations are situated locally in 900 m in altitude related to the same formations located in the Habra plain (~50 m), this difference of altitude show the strongest plio-quaternary tectonic very big exhumation (~900 m) in fewer times (~5 my). This ascertainment show the importance of tectonic activity as reverse and strike slip faults (Bezzeghoud et al 1999; Ayadi et al 2002). These folds are materialized by reverse fault directly in contact with the quaternary formation

Methods

Results

Conclusion