Seismotectonics and seismic quietness of the Oranie region (Western Algeria): The Mascara earthquake of August 18th 1994, Mw = 5.7, Ms = 6.0 |
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| Authors: | A Ayadi F Ousadou-Ayadi S Bourouis H Benhallou |
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| Institution: | (1) Département Etudes et Surveillance Sismique, Centre de Recherche en Astronomie Astrophysique et Géophysique, BP63 Bouzaréah, Algiers, Algeria;(2) Centre de Recherche en Astronomie Astrophysique et Géophysique, BP63 Bouzaréah, Algiers, Algeria;(3) Département de sismologie, Institut de Physique du Globe de Paris, Université, Paris 6, France;(4) Département de Géophysique, Institut des Sciences de la Terre, Université des Sciences et de la Technologie Houari Boumédienne, BP32 El Alia, Bab Ezzouar, Algiers, Algeria |
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| Abstract: | The plate dynamics in the central western Mediterranean region is characterised by a collision between the Eurasian and African plates. In response to this dynamics, many systems of faults and folds having a NE-SW and E-W trending have been generated along the Tellian Atlas of Algeria. The Oranie region (north western Algeria) has experienced some significant earthquakes in the last centuries, the most important one is that of Oran city on February 9th 1790, Io = XI which destroyed the town completely and caused the loss of many lives. Since 1790 no other event was so disastrous except that of August 18th 1994, Mw = 5.7, which struck Mascara province (Algeria) at 01 h 13 mn GMT. Since the beginning of this century the region has been dominated by a seismic quietness. Thus, no event with magnitude larger than 5.5 have occurred in this area. In relation with this recent event, a seismotectonic framework summarising the tectonic, seismicity and focal solution results is presented. The Maximum Observed Intensities Map (MOI) made for Algeria (Bezzeghoud et al., 1996) is also used to show that the Mascara region is located in an VIII-X intensity zone, which explain partially the casualties caused by the 18/08/1994 (Mw = 5.7) earthquake. This earthquake is not anomalous compared to historical records but is unusual compared to recorded seismicity of this century. The seismotectonic map made in this study and also the review of the focal solutions given by the EMSC, Harvard, and other authors shows that our event is probably associated with a source belonging to a system of faults located in the vicinity of the village of Hacine where the maximum damage was observed. |
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| Keywords: | Algeria focal solution Mascara earthquake seismic quietness seismicity seismotectonics |
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