[1] A strong earthquake (Mw 6.8) struck the coastal region east of Algiers and the Tell Atlas of Algeria on 21 May, 2003 and was responsible of severe damage and about 2400 casualties. The coastal mainshock was followed by a large number of aftershocks, the largest reaching Mw 5.8 on 27 May 2003. We study the mainshock, first major aftershocks and about 900 events recorded by temporary seismic stations using master-event approach and doubledifference (DD) methods. Although the seismic station array has a large gap coverage, the DD algorithm provides with an accurate aftershocks location. The mainshock hypocenter relocation is determined using three major aftershocks (5.0 Mw 5.8) chosen as master events. The new mainshock location shifted on the coastline (36.83N, 3.65E) at 8 -10 km depth. Seismic events extend to about 16-km-depth and form a N 55°-60°E trending and 45°-55°SE dipping fault geometry. Up to now, it is the unique among the recently studied seismic events of the Tell Atlas of Algeria. Mainshock and aftershocks relocation, the thrust focal mechanism (Harvard CMT: N 57°, 44°SE dip, 71 rake) and the seismic moment 2.86 10 19 Nm, infer a 50-km-long fault rupture that may appear at the sea bottom at 6 to 12 km offshore north of the coastline. The Zemmouri earthquake occurred along the complex thrust-and-fold system of the Tell Atlas and provides with new constraints on the earthquake hazard evaluation in northern Algeria.
The 21 May 2003 Zemmouri earthquake ( Mw=6.8), which killed 2,278 people, injured 11,450, made 250,000 homeless, and destroyed or seriously damaged 6,000 buildings and 20,800 housing units, is the most significant earthquake to affect Algeria since the 1980 El Asnam earthquake ( Ms=7.3). This paper presents the report of the macroseismic survey conducted by the Centre of Research in Astronomy, Astrophysics, and Geophysics (CRAAG, Algeria) immediately after the earthquake. The collected data set has led to a comprehensive evaluation of damage and estimation of intensity at about 600 sites, a number never reached in previous earthquake damage surveys. The produced isoseismal map portrays the spatial distribution of intensities from III to X EMS. A map highlighting the damage distribution, where various geological and hydrological phenomena are reported, is also presented. The extent of the socioeconomic impact of this event confirmed that Algerian buildings are highly vulnerable to the recurrence of destructive earthquakes.
On March 20, 2006, a moderate-magnitude earthquake of M w 5.2 hit the region of the Babors mountains, a region located two hundred km east of Algiers (capital of Algeria). More precisely, the epicentre occurred 40 km south-east of Béjaïa, the second most important city in the Kabylian region. The earthquake impacted an area with a radius of about 70 km and caused the death of four persons and injured 68. Damage was mainly observed in Lâalam village (district of Kherrata) where some buildings and old houses were affected. Damage was mainly due to a moderate landslide triggered by the earthquake. Rock falls were also observed near the main cliffs. The maximum observed intensity I 0 was estimated to VII (EMS-98 scale). According to the main shock focal mechanism solution and the spatial distribution of aftershocks, the main shock was reliably found to have been generated by an NS sinistral strike-slip fault. The compressive stress axis r 1 , oriented N325, is in agreement with the direction of convergence between Eurasia and Africa.
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