Elsevier

Journal of Geodynamics

Volume 36, Issues 1–2, August–September 2003, Pages 305-322
Journal of Geodynamics

The 1755 “Meknes” earthquake (Morocco): field data and geodynamic implications

https://doi.org/10.1016/S0264-3707(03)00052-8Get rights and content

Abstract

The source of the famous 1 November, 1755 “Lisbon” earthquake has been constrained to be an up to 200 km long structure in the offshore west of Cabo de S. Vincente. The magnitude of this earthquake was estimated in the range of 8.5–9.4. The stress regime argued for this shock would have been characterised by an around NNW–SSE-oriented compression. Less well studied is the successive “Meknes” earthquake, which occurred a few days later in Morocco (27 November), and was erroneously confused by the European contemporary reports with a strong aftershock, occurred on 18 November, of the main seismic sequence of the 1 November earthquake. The Meknes earthquake had destructive effects in the region of Meknes and Fes and along the E–W trending Rides Prérifaines, the main frontal thrust of the Rif. Historical data indicate a macroseismic field closed around the towns of Meknes and Fes.

Our structural–geological fieldwork and remote sensing analysis in the epicentral area of the Meknes earthquake, along the local major recent faults, indicate that the E–W-oriented thrusts of the Rides Prérifaines are active. Through a re-examination of historical sources compared with field work and air photo interpretation, we could individuate the traces of coseismic surface faulting of the 1755 Meknes earthquake in two areas of the Rides Prérifaines, both part of the local thrust front: the Jebel Zerhoun area and the Jebel Zalagh area. Tectonic data on the Quaternary stress fields derived from our fieldwork and from literature, consistently with the revised focal mechanisms in the region, indicate active shortening oriented NNW–SSE to N–S in northern Morocco. The data collected seem therefore to indicate the thrusts of the Rides Prérifaines, located within the macroseismic area of the Meknes earthquake, as the most probable seismic source of that event. As such, the activation of the thrusts of the Rides Prérifaines would be consistent with this stress regime, which in turn would be similar to the stress field maintained as responsible for the 1 November, 1755 Lisbon earthquake. We also attempted an estimate of the change due to the Lisbon earthquake of the Coulomb Failure Function (CFF) on the Meknes structure, as identified in this paper, in order to evaluate if the Meknes earthquake could have been induced by the 1 November, 1755 Lisbon earthquake, or a local distinct earthquake. Our modelling suggests that the latter hypothesis is the more likely one.

Introduction

The 1 November, 1755 “Lisbon” earthquake, accompanied by a large tsunami wave over a large part of the Atlantic coast, has been the most devastating event affecting the Atlantic and Mediterranean area and one of the strongest in history. Its magnitude has been estimated in the range of 8.5–9.4 (Machado, 1966, Lopez Arroya & Udias, 1972, Abe, 1979, Sousa Moreira, 1983, Martins & Mendes Victor, 1990, Baptista et al., 1998a, Baptista et al., 1998b). Its source has been constrained to be a structure, up to 200 km long, in the offshore west of Cabo de S. Vincente (Fig. 1), and two main hypotheses have been put forward to localise the epicentral area of the 1 November earthquake: (1) the area of Marques de Pombal (MP in Fig. 1), where active reverse faults have been identified by seismic investigation (Zitellini et al., 1999, Zitellini et al., 2001, Gracia et al., 2001); (2) the area of Gorringe Bank (GB in Fig. 1), where compressive deformations distributed over a 200-330 Km wide zone have been recognised (Hayward et al., 1999). This latter was also the epicentre of the 28 February 1969 earthquake (Mw=7.5–8.1). The shock of 1969, for the similarities of the two macroseismic fields (Fig. 1), has been assumed as an analogue of the 1 November 1755 earthquake (Levret, 1991 and references therein).

A few days after the main Lisbon earthquake a strong shock affected Morocco. Historical data indicate a macroseismic field closed around the towns of Meknes and Fes (Levret, 1991; Fig. 1). The most destructive effects were in the town of Meknes, from where it is referred to as the “Meknes” earthquake. European and Arab sources disagree about the date of the occurrence of this latter event. While contemporaneous Arab sources report unanimously 27 November for this occurrence (SFERN, 1985, Levret, 1991 and references therein; El Mrabet Azaroula, 1991), European historical sources report only about damages in Morocco due to an aftershock, which occurred on 18 November for which the same epicentre of the 1 November main shock was estimated (Pereira de Sousa, 1919–1928).

In this paper, we analyse the active faults of the Meknes area aiming at the identification of the possible seismogenic structure of that earthquake and discussing its relationships with the tectonics of the area. We also perform a computation of the stress field change induced by the Lisbon earthquake, in order to evaluate its possible influences in the Meknes area. This paper should also provide a better characterisation of the seismotectonic and geodynamic behaviour of the area in relation with the western Eurasia–Africa plate boundary.

Section snippets

Seismotectonics of the Alboran Sea and Gibraltar Arc

The western sector of the Eurasia–Africa plate boundary, running along the transform dextral Gloria Fault System, which relies the Azores triple junction to the Gibraltar Arc, is clearly defined by both bathymetry and clustering of seismicity (e.g. Udias et al., 1976, Grimison & Chen, 1986, Grimison & Chen, 1988, Buforn et al., 1988a, Hayward et al., 1999). In the Gibraltar Arc and Alboran Sea area, the plate boundary is less well defined and seismicity spreads over a larger area (McKenzie, 1972

The Rif-Atlas System

The Rif-Atlas System of Morocco consists of three Alpine chains delineating a big Z-shaped structure. The NE–SW-trending Middle Atlas relies the E–W-oriented Rif and High Atlas chains, respectively developed to the north and to the south of it (Fig. 3a and b).

The E–W-trending High Atlas bounds to the south the Moroccan Meseta, the Middle Atlas and the Oran Meseta. Its central and eastern sectors constituted the southern branch of the Triassic/Early Jurassic Atlasic basin, aborted and inverted

The 1755 Meknes earthquake and effects

The 1755 Meknes earthquake macroseimic area is located in correspondence of the Rides Prérifaines and of the northern part of the Meknes Basin (Levret, 1991) (Fig. 1, Fig. 3).

We performed a field survey in the Rif-Atlas system aimed at the identification of the major active faults. The main thrust fronts of the Rides Prérifaines and of the High Atlas show clear evidence of activity and tend to thrust onto the NE–SW-oriented Middle Atlas (Piccardi et al., 2001) (Fig. 3a and b).

Stress field variation of the 1755 Lisbon earthquake

The European historical sources report only a destructive earthquake after the Lisbon main shock. According to Levret (1991) this event was “an aftershock…on November 18 at 10 p.m.” that “was felt in both Portugal and Morocco”. We localised the Meknes source in Morocco so that we cannot regard it as an aftershock of the Lisbon earthquake in a classical sense. However the same Meknes earthquake could be considered as an after-effect of the Lisbon earthquake in the sense that it could be a

Discussion and conclusion

On 27 November 1755 a strong earthquake stroke the area of Meknes, in front of the E–W-trending Rides Prérifaines, the local external frontal thrust of the Rif, the southern branch of the Gibraltar Arc.

European historical sources confused the 1755 Meknes earthquake with an aftershock, occurred on November 18, of the main Lisbon event, while the Arab sources clearly date it to 27 November. Through a re-evaluation of the historical documents, compared with field analysis and air photo

Acknowledgments

Authors wish to thank Carlos Sanz de Galdeano, Ahmed Chalouan and an anonymous referee for critical review of the manuscript. The work was supported by CNR (Italy) and CNRST (Morocco) funds in the framework of the bilateral project “Structural analysis, active tectonics and fluid geochemistry along the Middle Atlas Shear Zone” (Italian responsible Giovanna Moratti, Moroccan responsible Mohammed Dahmani).

References (103)

  • D. Hatzfeld et al.

    Microearthquake seismicity and fault plane solutions around the Nékor strike-slip fault, Morocco

    Earth Planet. Sci. Lett.

    (1993)
  • I. Jiménez-Munt et al.

    The transition from linear to diffuse plate boundary in the Azores-Gibraltar regionresults from a thin-sheet model

    Earth Planet. Sci. Lett.

    (2001)
  • D. Leblanc et al.

    Role of strike-slip faults in the Betic-Rifean orogeny

    Tectonophysics

    (1984)
  • A. Levret

    The effects of the November 1, 1755 “Lisbon” earthquake in Morocco

    Tectonophysics

    (1991)
  • F. Medina

    Present-day state of stress in Northern Morocco from focal mechanism analysis

    J. Struct. Geol.

    (1995)
  • C.K. Morley

    Notes on Neogene basin history of the Western Alboran Sea and its implications for the tectonic evolution of the Rif-Betic orogenic belt

    Journal of African Earth Sciences

    (1992)
  • S. Pondrelli et al.

    European-Mediterranean regional centroid-moment tensors1997–2000

    Phys. Earth Planet. Int.

    (2002)
  • J. Tejera de Leon

    Signification de la limite Jebha-Arbaoua (Maroc nord-occidental)une rampe latérale au-dessus d'une discontinuité crustale héritée de la période de “rifting”

    Journal of African Earth Sciences

    (1997)
  • L. Aı̈t Brahim et al.

    Mise en évidence d'un changement de direction de compression dans l'avant-pays rifain (Maroc) au cours du Tertiaire et du Quaternaire

    Bull. Soc. Géol. France, sér. VII

    (1984)
  • K. Abe

    Size of great earthquakes of 1837–1974 inferred from tsunami data

    J. Geophys. Res.

    (1979)
  • Belardinelli M.E., Bizzarri A., Cocco, M., 2003. Earthquake triggering by static and dynamic stress changes. J....
  • Bendkik, A., 2002. Carte géologique “Sidi Kacem” au 1/50.000. Notes et Mém. Serv. Geol. Maroc. n. 431, S.El.Ca.,...
  • Ben Sari, D. 1978. Connaissance géophysique du Maroc. Thèse Docteur es Sciences, Université de Grenoble...
  • Bernini, M., Boccaletti, M., El Mokhtari, J., Gelati R., Moratti, G., Papani, G. 1994. Geologic–structural map of the...
  • M. Bernini et al.

    Neogene sedimentary and tectonic evolution of the Taza-Guercif Basin

    Its significance in the Rif-Middle Atlas orogenic system. Notes et Mém. Serv. Géol. Maroc.

    (1996)
  • M. Bernini et al.

    Tectonics and sedimentation in the Taza-Guercif Basin, northern Morocco: implications for the Neogene evolution of the Rif-Middle Atlas orogenic system. In: Boccaletti, M., Dahmani, M., Moratti, G., (Eds.), Neogene sedimentation and tectonics in the Western Mediterranean

    J. Petroleum Geology

    (1999)
  • M. Boccaletti et al.

    The Gibraltar Arc:an example of neoalpine arcuate deformation connected with ensialic shear zones

    Mem. Soc. Geol. It.

    (1990)
  • Braunmiller, J., Kradolfer, U., Giardini, D., 2002. Regional moment tensor determination in the European–Mediterranean...
  • E.E. Brodsky et al.

    A new observation of dynamically triggered regional seismicityEarthquakes in Greece following the August, 1999 Izmit, Turkey earthquake

    Geophys. Res. Lett.

    (2000)
  • E. Buforn et al.

    Seismicity and focal mechanisms in South Spain

    Bull. Seismol. Soc. Am.

    (1988)
  • Carte Géologique du Maroc, Echelle 1/1.000.000, 1985. Royaume du Maroc, Ministère de l'Energie et des Mines, Direction...
  • A. Chalouan et al.

    Neogene tectonic evolution of the southwestern Alboran Basin as inferred from seismic data off Morocco

    AAPG. Bull.

    (1997)
  • A. Chalouan et al.

    The Rif mountain building (Morocco)a new tectonic scenario

    Bull. Soc. Géol. Fr.

    (2001)
  • L. Chatelain

    Le Maroc Romain

    (1968)
  • G. Choubert et al.

    Evolution du domaine atlasique marocain depuis les temps paléozoiques

    Livre Mém. P. Fallot, Paris

    (1962)
  • J.F. Dewey

    Extensional collapse of orogens

    Tectonics

    (1988)
  • M. Doblas et al.

    Neogene extensional collapse in the western Mediterranean (Betic-Rif Alpine orogenic belt)implications for the genesis of the Gibraltar Arc and magmatic activity

    Geology

    (1989)
  • R. du Dresnay

    Recent data on the geology of the Middle Atlas (Morocco)

  • A. Dutour et al.

    Nouvelles observations néotectoniques dans le Haut Atlas de Marrakech et le Haouz central (Maroc)

    Apports sur l'évolution récente d'un segment du bâti atlasique. Revue de Géologie Dynamique et de Géographie Physique

    (1985)
  • A.M. Dziewonski et al.

    Determination of Earthquake Source Parameters From Waveform Data for Studies of Global and Regional Seismicity

    J. Geophys. Res.

    (1981)
  • El Mrabet Azaroula, T., 1991. Tarikh Azzalazil Bi Almaghrib, min 846 ila 1960 (History of Moroccan earthquakes, from...
  • EHT (Eidgenössische Technische Hochschule), 2002, Catalog of Swiss Moment Tensor Solutions. Zürich....
  • J.-C. Faugères et al.

    Traits généraux de l'histoire tectono-sédimentaire du domaine des Rides prérifaines (Maroc septentrionale)

    C.R. Acad. Sc. Paris 278, Sér. D

    (1974)
  • Faure-Muret, A., Morel, J.L., (Coord.), 1994: Carte Néotectonique du Maroc, echelle 1:1.000.000, feuille 1. Notes et...
  • B. Fedan et al.

    Le bassin jurassique du Moyen Atlas (Maroc)exemple de bassin sur relais de décrochements

    Bull. Soc. Géol France, Sér. VIII

    (1989)
  • H. Feinberg

    Les séries tertiares des zones externes du Rif (Maroc)

    Notes Mém. Serv. Géol. Maroc

    (1986)
  • D. Frizon de Lamotte et al.

    Cinématique des Chevauchement néogènes dans l'Arc bético-rifaindiscussion sur les modèles géodynamiques

    Bull. Soc. géol. France

    (1991)
  • N. Froitzheim et al.

    Aspects of Western High Atlas Tectonics

  • J. Galindo-Zaldı́var et al.

    Stress and Paleostress in the Betic-Rif Cordilleras (Miocene to Present)

    Tectonophysics

    (1993)
  • Gasperini, P., Vannucci, G., FPSPACK: a package of simple fortran subroutines to manage earthquake focal mechanism...
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