The El Asnam earthquake and its eflects on building structures

On Friday 10 October, 1980 at l3h 24min 24s, a destructive earthquake struck El-Asnam and its surrounding villages causing the death of at least 3000 people, injuring more than 8500 and making about 480000 homeless. It damaged about 60000 housing units in the whole affected area, among them, 30000 units were destroyed. Almost all the seismological stations operating at that time recorded the main shock. Its magnitude was re-calculated at M_s = 7.4 (± 0.3). The epicenter was located at Beni Rached, 15Km east of El Asnam, the focal depth of the earthquake was 10 km and the approximate duration 40 seconds. The extent of the socio-economic impacts of these events confirmed that Algerian buildings are highly vulnerable to the recurrence of destructive earthquakes. This earthquake caused considerable economic losses to Algeria, had large socio-economic and psychological impacts on the region. The total cost of the damage has been estimated at around 5 billions U.S. Dollars.

The main reasons of the damages are:

-Use of the “vide sanitaire” (a short crawl space) which is used for water, gas, sewage and ventilation conduits, supported by short columns.

-Use of irregular building configurations with severe discontinuities in mass, stiffness and ductility.

-Use of very heavy roofs.

-Use of long heavy cantilevers.

-Use of thermal, expansion construction gaps without proper separation between adjacent parts of the building.

-Poor inspection and construction techniques.

-Inadequate building maintenance.

-Use of strong beams and weak columns,

Data source (Country report)

1.      Name: KIBBOUA Abderrahmane

2.      Organization: Assistant Researcher, National Center for Applied Research in Earthquake Engineering 

3.      Course: 2000-2001E

4.      Title: SEISMIC VULNERABILITY ASSESSMENT OF STRATEGIC BUILDINGS IN ALGERIA