The Constantine (northeast Algeria) earthquake of October 27, 1985: surface ruptures and aftershock study

Abstract An earthquake of magnitude M s = 6.0 (CSEM, Strasbourg) occurred at Constantine (Algeria) on 27 October 1985. This seismic event is the strongest felt in the Tellian Atlas since the El Asnam seismic crisis of October 10, 1980. A team from the Centre de Recherche d'Astronomie, d'Astrophysique et de Geophysique (CRAAG, Algeria), utilising 8 portable stations, registered the activity a few days after the main shock. The aftershocks follow a N045° direction, and show the existence of three ruptured segments. Cross sections display a remarkable vertical fault plane and suggest asperities in the rupture process. Surface breaks were found affecting Quaternary deposits. The principal segment is about 3.8 km long showing “enechelon” cracks with left-lateral displacement while the main direction of the rupture is N055°. Although the vertical motion is small, the northwestern block shows a normal component of the main surface faulting, while the left-lateral displacement is about 10 cm. The strike-slip focal mechanism solution determined from the global seismic network and field observations are in good agreement.

[1]  H. Philip,et al.  Structural analysis and interpretation of the surface deformations of the El Asnam Earthquake of October 10, 1980 , 1983 .

[2]  J. Mercier,et al.  Intra-plate deformation: a quantitative study of the faults activated by the 1978 Thessaloniki earthquakes , 1979, Nature.

[3]  John H. Woodhouse,et al.  Determination of earthquake source parameters from waveform data for studies of global and regional seismicity , 1981 .

[4]  J. Virieux,et al.  The evolution of the Gulf of Corinth (Greece): an aftershock study of the 1981 earthquakes , 1985 .

[5]  Robert K. Mark,et al.  Statistical relations among earthquake magnitude, surface rupture length, and surface fault displacement , 1984 .

[6]  James Jackson,et al.  Surface faulting in the southern Italian Campania-Basilicata earthquake of 23 November 1980 , 1984, Nature.

[7]  A. Hirn,et al.  Aftershock sequence of the January 1st, 1980, earthquake and present‐day tectonics in the Azores , 1980 .

[8]  Gaussian beam modelling of upper mantle phases , 1985 .

[9]  James Jackson,et al.  The 1978 earthquake sequence near Thessaloniki (northern Greece) , 1982 .

[10]  La crise sismique de Remiremont (Vosges) de décembre 1984: implications tectoniques régionales , 1985 .

[11]  H. Philip,et al.  Seismotectonics of the El Asnam earthquake , 1981, Nature.

[12]  H. Philip,et al.  Seismotectonics of the Lower Cheliff Basin: Structural background of the El Asnam (Algeria) Earthquake , 1986 .

[13]  C. Vita-Finzi,et al.  Active folding in the Algerian earthquake of 10 October 1980 , 1981, Nature.