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Geodetic network data and deformation surveys as a preliminary warning system

Farida Ousadou-Ayadi
CRAAG, BP 63, Bouzaréah 16430 Algiers, Algeria.
Tel. /Fax: +213-2 90 32 67,
E-mail: ess1@ist.cerist.dz

Abstract:
The El Asnam region is the most active zone in Algeria. This region has been struck by many seismic events according to the Algerian seismological catalogue. The biggest event known in the region is that of October 10th 1980 (M=7.3). The thrust fault which generated the events presented a surface rupture of about 43 km in length, in a NW-SE direction, with a maximum uplift of about 6 m.

The post-deformation of the crust is surveyed by means of a geodetic network. A databank spanning about 12 years has been used to show the deformation in the vicinity of the fault and enable us to show the behaviour of the two blocks of the thrust fault. We think that such studies, which consist of the surveying of the local variations in the stress field, could be considered as a preliminary warning system.