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Bounif, A.
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- PublicationOpen AccessThree dimensional velocity structure and relocated aftershocks for the 1985 Constantine, Algeria (MS = 5.9) earthquake(1998-04)
; ; ;Bounif, M. ou A.; CRAAG and USTHB, Institut des Sciences de la Terre, Alger, Algérie ;Dorbath, C.; ORSTOM, Paris, France; Local earthquake travel-time data were inverted to obtain a three dimensional tomographic image of the region centered on the 1985 Constantine earthquake. The resulting velocity model was then used to relocate the events. The tomographic data set consisted of P and S waves travel-times from 653 carefully selected aftershocks of this moderate size earthquake, recorded at 10 temporary stations. A three-dimensional P-wave velocity image to a depth of 12 km was obtained by Thurber's method. At shallower depth, the velocity contrasts reflected the differences in tectonic units. Velocities lower than 4 km/s corresponded to recent deposits, velocities higher than 5 km/s to the Constantine Neritic and the Tellian nappes. The relocation of the aftershocks indicates that most of the seismicity occured where the velocity exceeded 5.5 km/s. The aftershock distribution accurately defined the three segments involved in the main shock and led to a better understanding of the rupture process.237 292 - PublicationOpen AccessSeismic source study of the 1989, October 29, Chenoua (Algeria) earthquake from aftershocks, broad-band and strong ground motion records(2003)
; ; ; ; ; ; ; ;Bounif, A.; CRAAG, Département ESS, Bouzaréah, Algiers, Algeria ;Bezzeghoud, M.; CRAAG, Département ESS, Bouzaréah, Algiers, Algeria ;Dorbath, L.; IPGS, UMR 7516, Strasbourg, France ;Legrand, D.; IPGS, UMR 7516, Strasbourg, France ;Deschamps, A.; Geosciences Azur, Sophia Antipolis, Valbonne, France ;Rivera, L.; IPGS, UMR 7516, Strasbourg, France ;Benhallou, H.; CRAAG, Département ESS, Bouzaréah, Algiers, Algeria; ; ; ; ; ; The broad-band teleseismics records of the earthquake of October 29,1989 in Algeria (MW = 6.0) allow a detailed study of the rupture process of this earthquake. The focal mechanism obtained by P and SH modeling corresponds to reverse faulting with a small amount of left-lateral movement along a fault striking 246° and dipping 56°. The rupture is found to be complex with two sub-events separated in time but occurring on the same plane. The lowfrequency records of an accelerometer located some 25 km to the west of the main shock are also better fi tted when the rupture is composed of a double pulse. In the two cases, there is strong evidence for the rupture to propagate from south-west towards north-east.The relocalisation of the main shock by using a master-event technique and the data from Italian and Spanish stations led to the same conclusions. Soon after the main event, a temporary seimic network was installed in the epicentral area. The aftershock clouds defi ne a SW-NE fault dipping to the NW compatible with the results of the modelisations of the teleseismic body-waves and the accelerogram. The focal mechanisms correspond mainly to reverse faulting. The maximum principal direction of the stress tensor obtained from the inversion is about N-S and the minimum is vertical, typical of a compressive regime. The Chenoua earthquake took place on a fault which was not recognized as active. Repeated comparable seismic events on this fault and on the fault that borders the massif to the south explain this intriguing topographic feature.370 1071