Publication Date:
2003-01-01
Description:
A shallow moderate (Ms = 5.7) but damaging earthquake shook the region of Beni-Ourtilane located about 50 km NW of Setif and 390 km NE of Algiers (Central Eastern Algeria). The main shock caused the death of 2 peoples, injured 50 and caused sustainable damage to about 3000 housing units. The main shock was preceded by 2 foreshocks and followed by many aftershocks which lasted for many days. Analysis of historical seismicity including the localisation of epicenters, the trend of isoseismal maps of some historical events, the localisation of the November 10, 2000 main shock (Ms = 5.7) and the November 16, 2000 aftershock (Ms = 4.5) as well as the shape of the area of maximum intensity of the November 10, 2000 earthquake suggest that the Tachaouaft fault of 20 km of lenght is the activated geological structure. Although, there is no clear surface breaks associated with this earthquake, the localisation of geological disorders, such as ground fissures, during the Beni-Ourtilane earthquake, which are remarkably located near the fault, may have a tectonic meaning. Geomorphological analysis through Digital Elevation Models (DEMS) allowed us to identify a clear fault scarp related likely to strong earthquakes occurred in the past. Among geomorphological evidences of this active fault there are the uplift and tilt of alluvial terraces on the hanging wall and the diversion of the drainage pattern. Based on the quality of constructions and field observations an intensity Io = VII (MSK scale) is attributed to the epicentral area, which is striking NE-SW in agreement with the focal mechanism solution and the seismotectonic observations. In the other hand the amount of damage is due rather to the bad quality of constructions than to the severity of ground motion. The Tachaouaft fault with the Kherrata fault is the main source of seismic hazard in the Babors region.
Print ISSN:
1383-4649
Electronic ISSN:
1573-157X
Topics:
Geosciences
,
Physics
Permalink