Revisiting the Laalam (Eastern Algeria) March 20, 2006 ( M _w 5.1) Earthquake and its Seismotectonic Implication

K. Abbes , C. Dorbath (1) , L. Dorbath (1) , Y. Bouhadad , F. Ousadou , M. Bezzeghoud

1 EOST - Ecole et Observatoire des Sciences de la Terre

Hypocenters of main shock and aftershocks of the March 20, 2006 Laalam earthquake are relocated using HypoDD double-difference technique. We combined accelerogram and seismogram data of the National Center of Applied Research in Earthquake Engineering (CGS). Among about 191 aftershocks, recorded at least by 4 stations, 141 aftershocks of M _d 1.2-2.7 were relocated using HypoDD. The obtained swarm of epicenters occupying a crustal volume of 5 km × 3 km × 5 km and the focal mechanism corresponds to an unknown pure left lateral strike slip, trending N174°E. We were able to calculate focal mechanisms for only seven aftershocks with more than seven polarity readings, which give a P axis oriented NNW-SSE. The waveform inversion also provided values of M _w 5.1, M ₀ 5.9 10^-16 Nm and the depth 4.9 km. The dislocation and the stress drop were estimated to 90 cm and 16.5 bars, respectively.

Keywords: Earthquake; main shock; aftershocks; waveform inversion; focal mechanisms; lateral strike slip; Algeria

Domains: Sciences of the Universe [physics]

K. Abbes, C. Dorbath, L. Dorbath, Y. Bouhadad, F. Ousadou, et al.. Revisiting the Laalam (Eastern Algeria) March 20, 2006 ( M _w 5.1) Earthquake and its Seismotectonic Implication. Pure and Applied Geophysics, 2019, 176, pp.4213-4222. ⟨10.1007/s00024-019-02206-3⟩. ⟨insu-03708174⟩