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

  • K. AbbesEmail author
  • C. Dorbath
  • L. Dorbath
  • Y. Bouhadad
  • F. Ousadou
  • M. Bezzeghoud


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 Md 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 Mw 5.1, M0 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.


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



We would like to thank the editor and the anonymous reviewer for their thoughtful and constructive comments which helped to improve the manuscript. The authors are very grateful to Prof. Y. Yagi who provided us the moment tensor package. The figures were generated by Generic Mapping Tool (GMT) code developed by Paul and Smith (1998).


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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.National Center of Applied Research in Earthquake Engineering (CGS)AlgiersAlgeria
  2. 2.EOSTStrasbourgFrance
  3. 3.Research Center for Astronomy Astrophysics and Geophysics (CRAAG)BouzaréahAlgeria
  4. 4.Department of Physics, ECT and ICTUniversity of ÉvoraÉvoraPortugal

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