Elsevier

Earth and Planetary Science Letters

Volume 56, December 1981, Pages 287-304
Earth and Planetary Science Letters

Relations between surface deformation, fault geometry, seismicity, and rupture characteristics during the El Asnam (Algeria) earthquake of 10 October 1980

https://doi.org/10.1016/0012-821X(81)90135-7Get rights and content

Abstract

The El Asnam earthquake of October 10, 1980 (Ms=7.3) produced surface faulting on a northeast-trending thrust fault of 30 km length with displacements of up to 6.5 m, though average displacements were about 3 m. In addition, widespread tensional features were formed, some in clear association with folding above the thrust, and others, in an area beyond the exposure of the thrust at the surface, which may be related to buried reverse faults.

The observed thrust fault is split into southern, central and northern segments. Local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault, and propagated 12 km northeast where a second rupture of approximately equal moment occurred, continuing the faulting a further 12 km northeast along the central segment. Both ruptures nucleated at about 8–10 km depth. Displacements were largest on the central segment, where they were probably enlarged by aftershocks, including one of mb=6.1 three hours after the main shock. The northern segment was much shorter than the other two, and showed smaller displacement.

The junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting, as well as a sudden drop in the observed displacement. It appears that the rupture development is influenced by the changes in fault geometry between segments, and that such junctions or barriers have persisted through much of the late Quaternary.

References (32)

  • AmbraseysN.N.

    The El Asnam (Algeria) earthquake of 10 October 1980: conclusions drawn from a field study

    Q. J. Eng. Geol.

    (1981)
  • PerrodonA.

    Etude géologique des Bassins Néogenes sublittoraux de l'Algerie Occidentale

    Bull. Serv. Carte Géol. Algerie N. Ser.

    (1957)
  • SouflerisC.

    The Thessaloniki (N. Greece) 1978 earthquake sequence

  • KingG.C.P. et al.

    Active folding in the Algerian earthquake of 10 October 1980

    Nature

    (1981)
  • RothéJ.P.

    Le tremblement de terre d'Orléansville et la seismicitéde l'Algerie

    La Nature

    (1955)
  • McKenzieD.P.

    Active tectonics of the Mediterranean region

    Geophys. J.R. Astron. Soc.

    (1972)
  • JacksonJ. et al.

    Seismotectonic implications of relocated aftershock sequences in Iran and Turkey

    Geophys. J. R. Astron. Soc.

    (1979)
  • FlinnE.A.

    Confidence regions and error determinations for seismic event location

    Rev. Geophys.

    (1965)
  • BulandR.

    The mechanics of locating earthquakes

    Bull. Seismol. Soc. Am.

    (1976)
  • C. Soufleris, J.A. Jackson, G.C.P. King, B.C. Papazachos, C.H. Scholz and C.P. Spencer, The 1978 earthquake sequence...
  • W.L. Ellsworth and S.W. Roecker, Sensitivity of the earthquake location problem to network geometry, Geophys. J. R....
  • SharpA.D.L. et al.

    A low velocity zone beneath Etna and magma storage

    Nature

    (1980)
  • BockelM.

    Structure de la croute terrestre en Algerie d'après les ondes sismiques

    Ann. Geofis.

    (1972)
  • LeeW.H.K. et al.

    HYPO71 (revised): a computer program for determining hypocenter, magnitude, and first motion pattern of local earthquakes

    U.S. Geol. Surv. Open-file Rep. 75-311

    (1975)
  • LangstonC.A. et al.

    A procedure for modelling shallow dislocation sources

    Geophys. J. R. Astron. Soc.

    (1975)
  • JacksonJ. et al.

    Basement faulting and the focal depths of the larger earthquakes in the Zagros mountains (Iran)

    Geophys. J. R. Astron. Soc.

    (1981)
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