Active fault segmentation in Northern Tunisia

Gaidi, Seifeddine; Booth‐Rea, Guillermo; Melki, Fetheddine; Marzougui, Wissem; Ruano, Patricia; Pérez-Peña, Jose Vicente; Azañón, José Miguel; Zargouni, Fouad; Chouaieb, Haifa; Galvé, Jorge Pedro

doi:10.1016/j.jsg.2020.104146

Cited by 14 publications

(22 citation statements)

References 84 publications

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“…Blue lines represent the limit between internal and external zones and dark-red lines is the Tell-Rif front. Bright-red lines is a schematic representation of subsurface active faults, redrawn after Yelles-Chaouche et al (2006, Giaconia et al (2015), Rabaute and Chamot-Rooke (2015), Soumaya et al (2018), andGaidi et al (2020). GPS vectors and their associated errors are taken from Bougrine et al (2019).…”

Section: Geodynamic and Seismotectonic Settingsmentioning

confidence: 99%

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

Leffondré¹,

Déverchère²,

Medaouri

et al. 2021

Front. Earth Sci.

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Subduction initiation is an important but still poorly documented process on Earth. Here, we document one of a few cases of ongoing transition between passive and active continental margins by identifying the geometrical and structural signatures that witness the tectonic inversion of the Algerian continental margin and the deep oceanic domain, located at the northern edge of the slow-rate, diffuse plate boundary between Africa and Eurasia. We have analyzed and tied 7900 km of deep seismic reflection post-stacked data over an area of ∼1200 km long and ∼120 km wide. The two-way traveltime lines were converted into depth sections in order to reconstruct and map realistic geometries of seismic horizons and faults from the seafloor down to the acoustic basement. Along the whole length of this young transitional domain, we identify a clear margin segmentation and significant changes in the tectonic signature at the margin toe and in the deep basement. While the central margin depicts a typical thick- and thin-skinned tectonic style with frontal propagation of crustal thrust ramps, the central-eastern margin (Jijel segment) reveals a higher strain focusing at the margin toe together with the largest flexural response of the oceanic lithosphere. Conversely, strain at the margin toe is limited in the western margin but displays a clear buckling of the oceanic crust up to the Spanish margin. We interpret these contrasting, segmented behavior as resulting from inherited heterogeneities in (1) the geometry of the Algerian continental margin from West to East (wrench faulting in the west, stretched margin elsewhere) and (2) the Miocene thermal state related to the diachronous opening of the Algerian basin and to the magmatic imprint of the Tethyan slab tearing at deep crustal levels. The narrow oceanic lithosphere of the Western Algerian basin is assumed to favor buckling against flexure. From the dimension and continuity of the main south-dipping blind thrusts identified at the margin toe, we reassess seismic hazards by defining potential lengths for ruptures zones leading to potential magnitudes up to 8.0 off the central and eastern Algerian margins.

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Section: Geodynamic and Seismotectonic Settingsmentioning

confidence: 99%

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

Leffondré¹,

Déverchère²,

Medaouri

et al. 2021

Front. Earth Sci.

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“…Over this structural landscape, the greatest reliefs coincide with anticlinal ridges or the hanging wall of shortening structures; in turn, the topographic depressions and axial valleys occur in relation to synforms and the footwall of reverse faults [15,27,28]. Large NE-SW oriented axial valleys such as the Mejerda, Tine, Joumine, and Ghezala river valleys run parallel to the main shortening structures, e.g., the Alia-Thibar fault zone [28]. The landscape is furthermore influenced by rheological contrasts between competent and incompetent lithologies-respectively, limestones and pelites.…”

Section: Geological and Geomorphological Settingmentioning

confidence: 99%

Section: Geological and Geomorphological Settingmentioning

confidence: 99%

“…footwall of reverse faults [15,27,28]. Large NE-SW oriented axial valleys such as the Mejerda, Tine, Joumine, and Ghezala river valleys run parallel to the main shortening structures, e.g., the Alia-Thibar fault zone [28]. The landscape is furthermore influenced by rheological contrasts between competent and incompetent lithologies-respectively, limestones and pelites.…”

Section: Geological and Geomorphological Settingmentioning

confidence: 99%

“…Miocene half-grabens subparallel to the fold hinges in the region further stand out against the Eocene limestones in the uplifted footwall of the normal faults [31]. Since the Late Pliocene topographic incision and rejuvenation in Northern Tunisia, the landscape evolution is mostly driven by NW-SE directed tectonic shortening, accommodated along reverse and strike-slip faults and associated folds, which favor the development of incipient transverse drainage through recent fluvial captures [15,28].…”

Section: Geological and Geomorphological Settingmentioning

confidence: 99%

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Analysis of the Geological Controls and Kinematics of the Chgega Landslide (Mateur, Tunisia) Exploiting Photogrammetry and InSAR Technologies

et al. 2021

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Exploration of territories not previously analyzed by landslide experts provides interesting findings. The Chgega landslide, in northern Tunisia, represents a paradigmatic mass movement. It can be classified as a complex landslide, or more specifically as vast rock spreading that evolved into a block slide. It involves a great block of limestone—about 900 m long and 400 m wide—sliding over ductile clays and marls. The viscoplastic creep of the clays drives the landslide and creates, in its crown, a graben ~800 m long and ~120 m wide that breaks the summit of Chgega Mountain. Using Interferometric Synthetic Aperture Radar (InSAR) technologies, we demonstrate that this complex landslide is currently active and moreover shows progressive movement without clear episodic accelerations. The velocity of the limestone block is just above 2 mm/yr. The occurrence of gravity-induced joints indicates that the movement has an orientation towards 333° of azimuth on average, conditioned by the landscape around Chgega. These results were obtained through the analysis of a 3D model and a high-resolution orthoimage created from photographs acquired by an Uncrewed Aerial Vehicle (UAV). We may conclude that the landslide movement is determined by normal faults with directions N060°E and N140–150°E. This characterization of the Chgega landslide can serve as the basis for future studies about the origin of this slope movement. Furthermore, the data provided here may support the recognition of Chgega as a singular geological point that deserves to be declared a geosite.

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Sedimentological and stratigraphic constraints on Oligo–Miocene deposition in the Mogod Mountains, northern Tunisia: new insights for paleogeographic evolution of North Africa passive margin

Riahi

Soussi

Stow

2021

Int J Earth Sci (Geol Rundsch)

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Active fault segmentation in Northern Tunisia

Cited by 14 publications

References 84 publications

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

Analysis of the Geological Controls and Kinematics of the Chgega Landslide (Mateur, Tunisia) Exploiting Photogrammetry and InSAR Technologies

Sedimentological and stratigraphic constraints on Oligo–Miocene deposition in the Mogod Mountains, northern Tunisia: new insights for paleogeographic evolution of North Africa passive margin

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