The Oran January 9th (Mw 4.7) and June 6th, 2008 (Mw 5.4) earthquakes: Seismological study and seismotectonic implication

Abstract

The Oran region (Western Tell Atlas) was hit by two earthquakes on January 9th, 2008 (Mw = 4.7) and on June 6th, 2008 (Mw = 5.4). The two events were recorded by the national accelerographs network maintained by National Center of Applied Research in Earthquakes Engineering (CGS, Algiers). This work aims to characterize these two earthquakes in order to contribute to understand the seismotectonic context of the study region. We located the events using Grid Search Method based on P and S waves arrival time differences. The obtained hypocenter locations are, respectively, (0.457°W, 35.689°N, 11 km) and (0.576°W, 35.689°N, 8 km). We perform waveforms inversion to estimate the moment magnitudes and the seismic moments which are, respectively, Mw=4.7,M0 =0.13E+17NmandMw=5.4,M0 =0.1810E+18Nmforthetwoevents.Concerningthe focal mechanism solutions both earthquakes yield reverse faulting with a compressional axes oriented NW-SE which is consistent with the active fault system trend in the study region. These two events occurred in an area which has been seismically quiet, since the event of December 1959 (Ms 4.7) and the historical major event of October 9th, 1790 (I0= IX-X; likely Ms ≥ 6.0).