Los mayores sismos en Argelia en la época moderna: las fallas de El Asnam y Zemmouri-Boumerdès

M. Bezzeghoud,B. Caldeira,J. F. Borges,A. Ayadi,J. Fontiela

doi:10.5209/fite.57618

Abstract

Algeria has experienced many destructive earthquakes during the last few centuries (e.g., Ayadi and Bezzeghoud, 2015). The city of El Asnam (formerly Orleanville, today Chlef) was severely damaged in 1954 and 1980 by magnitude 6.7 and 7.3 earthquakes, respectively. On October 10, 1989, a magnitude 5.9 earthquake struck the Mont Chenoua-Tipasa coastal area approximately 150 km west of Zemmouri, which is where the May 21, 2003 earthquake occurred (Mw6.8). Many other large historical and instrumental earthquakes have severely damaged the coastal cities of Algeria over the last few centuries (i.e., around Algiers, Oran, Mascara, Djidjelli, Constantine and Bejaia). These earthquakes suggest active deformation of the margin in conjunction with the clear offshore extent of active coastal faults. According to several studies, the main active geological structures around El Asnam, Algiers, Zemmouri and Boumerdes have experienced several disastrous earthquakes. Many other earthquakes have occurred in and around the Chlef and Mitidja Basins, underlining the seismic activity in the area. In this chapter, we highlight the main characteristics of the two largest earthquakes that have occurred in Algeria in the modern period: the El Asnam earthquakes of September 9 (Mw6.7) and October 10 1980 (Mw7.3), and the Zemmouri-Boumerdes earthquake of May 21, 2003, (Mw6.8).

Highlights

Since the beginning of the 21st century, changes in Algeria’s seismicity have been monitored by a telemetered seismic network
In 1990, a set of 32 stations were installed along the Tellian Atlas region, which is the most active seismic zone in northern Algeria
Upon reading the Algerian earthquake catalogue and looking at a map of the maximum observed intensities, we can see that all of northern Algeria is characterized by zones of high seismic risk

Summary

Introduction

Since the beginning of the 21st century, changes in Algeria’s seismicity have been monitored by a telemetered seismic network. The entire pattern of seismicity shows that there is a concentration of seismic activity along the northern Algeria border, especially in the zone near the coast, that is defined along the plate boundary zone between Africa and Eurasia and ranges from the Azores to the Aegean Sea. The epicentres are clearly located along the Tellian Atlas where numerous earthquakes have occurred over the last few decades, and the largest shocks include the following: El-Asnam (October 10, 1980; Mw=7.3), Constantine (October 27, 1985; Mw=5.9), Tipasa-Chenoua (October 29, 1998; Mw=6.0), Mascara (August 18, 1994; Mw=5.7) and Algiers (September 4, 1996; Mw=5.5). A map of the maximum observed seismic intensities (see figure 7 of Ayadi and Bezzeghoud, 2015) of Algeria clearly shows that the seismogenic zones are concentrated along the Tellian Atlas of Algeria These zones (i.e., Oran, Mascara, El Asnam, Tipasa-Blida, Jijel, and Constantine) are concentrated linearly from the west to the east and define a boundary between the African and Eurasian plates.

Seismicity and tectonic setting

The El Asnam earthquakes

Modelling and dislocation models for the 1954 and 1980 earthquakes

Damage and casualties

Source location and parameters

Findings

Final remarks