Re-appraisal of seismicity and seismotectonics in the north-eastern Algeria. I. Review of historical seismicity

As large destructive seismic events are not frequent in Algeria, an exhaustive knowledge of the historical seismicity is required to have a realistic view of seismic hazard in this part of the world. This research work presents a critical reappraisal of seismicity in the north-eastern Algeria for seismotectonic and seismic hazard purposes. This part of work focuses on the seismicity of pre-1900 period for the area under consideration [33DGN-38DGN, 4DGE-9.5DGE]. By going back to the available documentary sources and evaluating and analysing the events in geographical, cultural and historical context, it has been possible to identify 111 events, from 1850-1899, which are not reported in the recent Algerian catalogue. Several spurious events, reported in standard listings, have been deleted and nine unknown events have been discovered. It is quite clear that macroseismic information derived from press reports and published documents in Algeria, under certain conditions, is very incomplete, even for destructive earthquakes, located in the countryside away from communication centres. One of the reasons for this is censorship, noticeable during the colonisation period. Critical analysis of newly collected information has allowed the determination and/or the improvement of the macroseismic parameters of each event, such as location, maximum epicentral intensity and magnitude to produce an earthquake catalogue as homogeneous and complete as the available data, for the zone under study. The criteria used in this research are explained and eight historical earthquakes have been the subject of retrospective macroseismic field construction. The investigation of historical earthquakes is one of the most important task in studying seismotectonic for seismic hazard evaluation purposes.