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STN-01 General contributions to neotectonics
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Changing tectonic styles of recent and active structures in the Rif Cordillera and asymmetry in respect to the Betic Cordillera (Western Mediterranean)
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Jesus Galindo-Zaldivar, Universidad de Granada (Spain)
Ahmed Chalouan, Faculté des Sciences, Université Mohammed V- Agdal (Morocco)
Patricia Ruano, Universidad de Granada (Spain)
Omar Azzouz, Université Mohammed premier- Oujda (Morocco)
Carlos Marin-Lechado, Instituto Geologico y Minero de España (Spain)
Antonio Pedrera, Universidad de Granada (Spain)
Ana Ruiz-Constán, Universidad de Granada (Spain)
Farida Anahnah, Universidad de Granada (Spain)
Mohamed Benmakhlouf, Faculté des Sciences, Université Abdelmalek Esaadi (Morocco)
Carlos Sanz de Galdeano, IACT, CSIC-Universidad de Granada (Spain)
Mfedal Ahmamou, Faculté des Sciences, Université Mohammed V- Agdal (Morocco)
Angel Carlos Lopez-Garrido, IACT, CSIC-Universidad de Granada (Spain)
Latifa Ameza, Faculté des Sciences, Université Mohammed V- Agdal (Morocco)
Roldán García Francisco Javier, Instituto Geologico y Minero de España (Spain)
Ahmed Chabli, Faculté des Sciences, Université Mohammed V- Agdal (Morocco)
Mostapha Akil, Faculté des Sciences, Université Mohammed V- Agdal (Morocco)
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The Betic and Rif Cordilleras, separated by the Alboran Sea, constitute the alpine orogen that formed the Gibraltar Arc at the western Mediterranean Sea. The westwards migration up to early Miocene of the Alboran Domain, the most internal domain, determined the roughly symmetrical structure of the cordilleras between Variscan African and Iberian margins. The NW-SE convergence between Eurasian and African plates since the Tortonian is responsible for the development of the main relieves. The area is affected by a broad band of seismicity that evidences the dispersion of the present-day tectonic activity.
The distribution of the recent and present-day active structures in a S -N cross-section of the Rif Cordilleras shows a typical transition from thin skinned to thick skinned tectonics. From the foreland (Moroccan Meseta), the southern Saïss foreland basin is deformed by extensional faults, while in its northern part, reverse faults formed by the Rif propagation are observed. The frontal part of the Rif is formed by the Prerif Ridges, an active fold and thrust belt with very shallow associated seismicity and of Quaternary compression evidences. In constrast, the Rifian Internal Zones in Al Hoceima area constitute a region with probably active crustal detachments. Transcurrent basement faults produce catastrophic seismicity (M=6.4, February 24, 2004), but does not extends to surface, where transtensional and normal faults determine the geometry of the main recent basins. Northwards is located the Alboran Sea, an area of thinned continental crust, that has undergone shortening at its boundaries since the late Miocene. In the Betic Cordillera, most of the recent and active deformation is located at the Internal Zones where the hanging walls of crustal detachments are deformed by kilometer-size late folds that determines the main features of the present-day relief. Normal and transtensional faults are the most abundant in the surface in central Betic Cordilleras, while strike-slip faults are mainly developed in their eastern part. The frontal part of the Betic Cordillera is practically inactive.
These cordilleras have undergone a stage of symmetrical deformation followed by asymmetrical tectonic activity due to the interaction of present oblique convergence and inherited arched geometry. While Rif show a typical distribution of active deformations, the Betic Cordilleras constitutes the backstop of the deformation area with concentration of compressive structures in the Internal Zones where the highest relieves are reached. In addition in the internal zones, geophysical data shows the presence of detachment levels determining that seismogenic deep faults not reach the surface and cannot be studies by classical geological and paleoseismological techniques, that only allow to characterize the shallow outcropping faults. In these regions 3D crustal models, integrating geophysical and geological data, are needed to assess the seismic hazard.
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