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et al. (2004) reconsidered the epicentre location and magnitude using the accelero-
grams and the accelerometric records, respectively, with the empirical formula of
Betbeder-Matibet (1995); they also give details on the recorded acceleration at
12 stations. Harbi et al. (2007b) provided the results of the macroseismic survey
conducted immediately after the earthquake and produced maps of damage and in-
tensity of the Zemmouri earthquake. The NE-SW elongation of isoseismals well
correlates with the fault direction identified from seismotectonic studies (Ayadi
et al. 2003).
3 Soil Conditions
The geological and tectonic setting of the Mitidja basin was presented and discussed
at length in previous works (Meghraoui 1988, 1991, Harbi et al. 2004, Maouche
et al. 2004). In the 2003 earthquake area, the local geology shows that, the base-
ment outcrops east of Boumerdes, North Thenia and west in the Blida Mountain.
It is mainly composed of bedrock formed by schist, micaschist, gneiss and the
Mesozoic calcareous units which constitute the eastern mountain chain of Djurd-
jura. To the west, the basement outcrops at Cap Matifou and Bouzareah (Algiers).
The epicentral zone is covered essentially by Plio-Quaternary deposits. The recent
Quaternary includes the alluvial deposits made of clay, silt and gravel within the
basin area and marine terraces along the coast (Fig. 2). From Boumerdes to Algiers,
crossing the Mitidja basin, the local geology is made of soft sediment such as sandy
dunes with alluvial and marine deposits, mixed sandstone and clay (fill) and the
Algiers
Bejaia
Tenes
D e llys
Oran
Cap Matifou
Bouzareah
Algiers
Zemmouri
Boumerdes
H o d n a
B a s i n
Dar Beida
Km
40
Thenia
Isser
Basement
Flysh
Fault
T ipaza
Lar b aa
Boufarik
Reverse fault
Miocene
Bli d a
Anticline
Volcanism
Pliocene
Quaternary
Main choc
Localities
25 km
Marine terraces
Active basins
Fig. 2 Structural geological map of the Algiers region including the area affected by the 21 May
2003 Zemmouri earthquake
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