Abstract. The Alboran system reflects the interplay of slow Nubia–Iberia convergence, inherited structures, and ongoing lithospheric attenuation. Earthquake occurrence mainly tracks active crustal fault networks that partition the oblique plate motion into strike-slip and extension. The 2021–2022 seismic swarm in the western Alboran Sea represents an exceptional episode characterized by complex temporal-spatial evolution, primarily influenced by fluid-driven processes interacting with inherited fault systems. We analyzed arrivals of approximately 7,000 seismic events recorded by Spanish (IGN) and Moroccan (CNRST) seismic networks. Both bulletins have been individually and jointly processed using the double-difference algorithm (HypoDD) and a regionally optimized velocity model. This approach significantly improved hypocentral precision, reducing event scatter and delineating a clearly defined, near-vertical seismic conduit-oriented NW–SE. Spatiotemporal analyses revealed distinct episodes of seismic migration, consistent with episodic fluid overpressure pulses, confirmed by diffusivity values (1.2–13.9 m2/s) characteristic of fluid-controlled swarms. Focal mechanisms predominantly indicated strike-slip motion, aligning with the regional transtensional tectonics and pinpointing the unrecognized Ras Tarf Fault as the primary seismogenic structure likely linked to the Al-Idrissi Fault System (AIFS). Integration with vertical and horizontal shear-wave velocity models (VSH and VSV) highlighted velocity anomalies at depths of 30–70 km, suggesting the presence of partially serpentinized mantle wedges above a delaminating slab segment, further supporting fluid involvement. Our results emphasize the critical interplay between deep lithospheric fluids, inherited fault structures, and regional tectonic stress, providing a comprehensive framework for understanding the 2021–2022 swarm dynamics which could improve the seismic hazard assessment in the region.

In this study, we apply the small baseline interferometric synthetic aperture radar (InSAR) time series analysis over two years spanning the M6.8 2023 Al Haouz earthquake to explore ground deformation in Morocco's High Atlas region. Our investigation successfully mapped the expected co-seismic deformation patterns associated with the earthquake. In addition, we identified a significant localized subsidence signal of approximately 21 km2 near Oulad Berhil agricultural area beside the epicentral, exhibiting high rates up to approximately 10 cm/yr, which is attributed to anthropogenic groundwater extraction, shows some disturbances by the earthquake mechanism. We suggest that the mainshock probably induced large poroelastic perturbations.

The High Atlas (HA) forms a major intracontinental belt along the northern margin of the West African craton, stretching from the Atlantic coast of Morocco to the Tunisian Mediterranean across the Saharan Atlas. Global Positioning System data record surface deformation rates below 1 mm/yr, underscoring limited present-day tectonic activity in the framework of the convergence of the Nubian and Eurasian tectonic plates. This study investigates the coseismic deformation following the Mw 6.8 Al Haouz earthquake, combining Interferometric Synthetic Aperture Radar modeling, Coulomb stress change analysis, and the examination of aftershock distribution. We investigate the Earth’s structure to understand the earthquake sequence in relation to its regional geodynamics, using ambient noise seismic tomography and P-wave coda autocorrelation. Our findings show a west-southwest–east-northeast high-angle blind reverse fault dipping to the northwest that is located beneath a flower structure, with its surface manifestation directly correlating to the documented Tizi n’Test fault. Coulomb failure stress change calculations revealed that the mainshock loaded nearby major faults by ∼5 bars, a change that aligns spatially with subsequent aftershock clusters. The resolved Moho and lithosphere–asthenosphere boundary (LAB) depths beneath the western High Atlas revealed a significant increase in Moho depth, which reached 45–50 km in the epicentral region. In contrast, the Moho remains relatively shallow (averaging ∼35 km) in the surrounding low-topography areas. Notably, a clear inverse correlation was observed between Moho and LAB depth, with a shallower LAB corresponding to a thicker crust, and vice versa. The Al Haouz earthquake ruptured at least two-thirds of the thick crust that likely compensates the HA topography in a region characterized by a 30 km thin lithospheric mantle at the edge of the western African craton. This suggests that the slow deformation is likely governed by an oblique crustal convergence and a localized asthenospheric uplift caused by a lateral flow of the Canary Plume in interaction with the western African craton.

The Moroccan High Atlas is a slowly deforming intracontinental orogenic belt, characterized by moderate and diffuse seismic activity. The 8 September 2023 Mw 6.8 El-Haouz earthquake, one of the most powerful quakes recorded in North Africa, has intensified investigations into the seismotectonics of the High Atlas. This study examines seismotectonic patterns in the High Atlas using seismological and geodetic data to better understand the mechanisms driving such seismic events. Seismological data indicate active shortening in the region, contributing to ongoing mountain building. Present-day deformation is partitioned between thrust and strike-slip faulting, with NW-SE compression, consistent with the broader stress field in North Africa. Frequency-magnitude distribution analysis indicates that the Western High Atlas exhibited low b-values, slightly lower than 1, in the eight years preceding the El-Haouz earthquake, with an low b-value (similar to 0.8 +/- 0.1) near the epicenter, suggesting high stress accumulation in the region. GNSS observations reveal that the High Atlas experiences low geodetic velocities compared with the Rif collision belt, with displacements below 1 mm/year. Notably, the axial zone of the Western High Atlas exhibits an uplift of 1.1 mm/yr. The combination of moderate shortening and relatively higher uplift prior to the El-Haouz earthquake suggests that present-day deformation in the Western High Atlas is predominantly accommodated by the reactivation of inherited faults in the axial zone. This is further corroborated by the distribution of aftershocks, which supports a steeply dipping seismogenic fault manifested by the Tizi n'Test Fault.

Morocco's High Atlas is an intracontinental orogenic belt located at the northern edge of the West African Craton (WAC). This major belt extends from what is now the Atlantic margin of Morocco to the Mediterranean coast of Tunisia, spanning the Sahara Atlas in Algeria. Within the context of the convergence of Nubian and Eurasian, GPS measurements across the High Atlas in Morocco indicate a very low surface deformation rate (

The Global Navigation Satellite System (GNSS) has emerged as a practical and effective technique for studying slow and steady geodynamic movements, enabling continuous monitoring and precise quantification of deformation over different timescales. In Morocco, a network of GNSS stations has been established, offering valuable insights into tectonic processes. This paper focuses on investigating the geodynamic motion of the northwest Moroccan Atlantic Margin. By utilizing GNSS data, subsidence rates and horizontal velocity fields were determined for the first time, providing valuable information for oil and gas exploration activities. The study reveals an active uplift rate of 1 mm/year and a westward horizontal motion of 2.04 mm/year in the Essaouira segment. The paper presents a case study of the Essaouira–Agadir basin (EAB) onshore segment and investigates the anomalous displacement observed in this region compared to other coastal GNSS stations. Possible explanations for the observed movements include local processes such as salt tectonics and regional northwest–southeast compression related to Africa–Eurasia convergence. We suggest that the anomalous movement detected in this work is due to the regional northwest–southeast compression related to Africa–Eurasia convergence imparting an extrusion of the EAB to the west. This research contributes to a better understanding of the geodynamics in the northwest Moroccan Atlantic margin, thereby providing valuable insights for ongoing efforts in oil and gas exploration. Furthermore, it indicates the continued activity of the Agadir fault, which would exhibit a sinistral wrench movement, thus posing a threat to the city of Agadir and its inhabitants.

This paper uses high-resolution seismic profiles of the complex active zone of Al Hoceima (Morocco) to illuminate the active fault system, acquired along a main, 10 km long transect cutting across the strands of an active fault system in Al Hoceima bay area. The investigation approached was to tackle and follow faults vertical offset. The final seismic sections led to identify faults on the profiles and to distinguish the likely-active ones, with visible wide deformation features, where normal strike-slip faults trend N–S and NW–SE, principally related to the major Al Idrissi strike-slip fault system. To aid interpretation of this complex setting, we complemented seismic images with seismicity catalogs and focal mechanism solutions to investigate the active tectonics. These faults are accommodating an important part of the complex seismotectonic movements. Seismicity catalog in the Al Hoceima area exhibits a moderate seismic release (Mw < 6), with shallow depths mostly ≤ 20 km, focal mechanisms suggest mainly a strike-slip regime with a subvertical σ3 and subhorizontal σ1 implying a transtensional regime in the area. The seismicity seems to be confined between two major faults: Trougout in the east and Rouadi in the west. However, this trend is no longer respected in the last 2 years as seismic activity is shifting toward the eastern side of the Trougout fault. Moreover, a seismic gap zone around this fault is evident considering the instrumental seismicity catalog of last 100 years. This fault system and related seismicity could represent a potential hazard for neighbor cities.

The process of topographic maps updating in the Moroccan Agency for Land Registration, Cadaster and Cartography (ANCFCC) is essentially performed by manual 2D or 3D plotting based on aerial or satellite images. In this chapter, we use data from airborne LiDAR to automatically extract some map features for the purpose of speeding up the map updating process. We processed LiDAR data with both ArcGIS and QGIS Grass software to automatically generate some map data layers like contour lines and hydrography streams. The obtained features were compared by overlapping other data such as orthoimages, manually stereoplot map and contour lines generated after automatic photogrammetric correlation in the same area. The comparison of all datasets showed that LiDAR can bring a significant advantage in some areas like shaded areas of aerial images or areas of complex topographic structures like cliffs as well as in dense forest zones or even relatively urban areas where classic stereoplotting often presents difficulties. However, automatic processing of LiDAR data requires adapted parameters to avoid poorly or over detailed maps, particularly with hydrographic features even if the automatically obtained hydrographic streams present the advantage of being ordered following the stream size. We conclude that automated LiDAR data processing is of high value in terms of accelerating map updating and the extracted features like contours and hydrographic streams are of better quality than traditional methods.

Previous workers have used stratigraphic studies to identify three potential marine gateways that connected the Atlantic and Mediterranean during the Messinian salinity crisis (MSC): the Strait of Gibraltar that remains a 300-900-m-deep channel to the present-day and the Betic and Rifian corridors now exposed on-land in southern Spain and northern Morocco, respectively. Comparison of deepsea cores from the Atlantic and Mediterranean have shown that there was no significant or sea-level rise during the Messinian leaving a tectonic or climate control as the most likely cause for Messinian drying of the Mediterranean and that was followed in the early Pliocene by the re-flooding of Atlantic waters in the dessicated and evaporite-filled Mediterranean basin. In this study, we integrate bathymetric, GPS data from the Tangier Peninsula and its offshore areas with paleostress measurements at 25 sites ranging in age from Jurassic to Miocene. Offshore data from the Strait of Gibraltar indicates that the main ENE-lineament on the seafloor is a major right-lateral strike-slip fault whose sense is consistent with: 1) WNW-trending GPS vectors; 2) the arrangement of positive restraining and negative releasing bends; 3) formation of a 15-20-km-wide syncline within the Strait that deepened with continued compression; and 5) the right-lateral offset of the Mesozoic Calcaire Dorsale Ridge by ~7 km. Paleostress sites on-land in rocks of Oligocene to early Pliocene age indicate three events: 1) east-west compression of Miocene age inferred to record the formation and eastward motion of the Gibraltar arc; 2) NW-SE compression inferred to record the closure of Nubia and Iberia with compression of the Gibraltar arc; and 3) NE-SW compression inferred to represent continued compression of the Gibraltar arc that accompanied continued formation of the large syncline within the strait. We postulate that the offset of the highly resistant and 1-km-thick Calcaire Dorsale allowed the initial deep channels to open between the Atlantic and Mediterranean. We see no evidence for north-south-striking normal faults as postulated in strait-opening models based on roll-back of the Gibraltar slab.

Al Hoceima region, located in northern Morocco, is frequently stroked by earthquakes associated with tectonic faults in and around the Nekor Basin. In particular, the Al Hoceima area is crossed by a network of active faults, indicating the undergoing of this region under active deformation associated with the convergence between Africa and Eurasia. Here, we attempt to highlight a set of faults from 2D seismic data acquired over the Nekor Basin using artificial neural networks (ANNs) combined with seismic attributes. We condition the seismic data to remove random noise and expose the geological structures, and then we use it to define a group of attributes sensitive to the presence of faults. The selected attributes were trained through a fully connected multi-layer perceptron (MLP) on fault, and non-fault locations picked manually over seismic data to generate a single attribute referred to as fault meta-attribute probability. The generated fault meta-attribute probability has successfully illuminated geological discontinuities with efficiency. It is observed that in the western part of the study area, the fault probability has brought out thinned and sharpened fault images from seismic data, whereas the efficiency of this meta-attribute decreases towards the east due to the presence of noise around the fault’s positions. Based on these results, the interpretative approach followed in this work demonstrates the effectiveness of using machine learning and automatic methods on imaging geological structures from seismic data. We expect that these results can be used directly as input data in seismic hazard studies in this region.

The Maghrebian tectonic domain in North Africa is here examined in the light of the recent GPS and seismotectonic results. The region includes the plate boundary in the western Mediterranean previously characterized by transpression and block rotation. The crustal deformation is documented along the Atlas Mountains in terms of the displacement field, with strain partitioning largely controlled by plate motions. The tectonic and seismotectonic analysis is based on our published data on shortening directions of Quaternary faulting and folding compared with present-day seismotectonic characteristics (earthquake moment tensors) of significant seismic events that allow an estimate of local and regional deformation rates in North Africa. Shortening directions oriented NE-SW to NW-SE for the Pliocene and Quaternary, respectively, and the S shape of the Quaternary anticline axes are in agreement with the 2°/Myr to 4°/Myr clockwise rotation obtained from paleomagnetic results on small tectonic blocks in the Tell Atlas. The continuous GPS data and results are obtained from the network in Morocco operative 1999 to 2006, the REGAT network in Algeria since 2007, and the network in Tunisia with data collected from 2014 to 2018. In addition, we add the most recent GPS results in southern Spain and southern Italy. The NW-SE to NNW-SSE 5 ±1.5 mm/yr convergence velocity and strain distribution of the Maghrebian tectonic domain is controlled by crustal block tectonics driven by E-W trending right-lateral faulting and NE-SW thrust-related folding. The correlation between the active transpression tectonic structures and velocity field shows a geodynamic framework consistent with the oblique plate convergence of Africa towards Eurasia.

The geodynamic processes in the western Mediterranean are driven by both deep (mantle) processes such as slab-rollback or delamination, oblique plate convergence and inherited structures. The present-day deformation of the Alboran Sea and in particular the Nekor basin area is linked to these coeval effects. The seismically active Nekor basin is an extensional basin formed in a convergent setting at the eastern part of the Rif Chain whose boundaries extend both onshore and offshore Morocco. We propose a new structural model of the Nekor basin based on high-resolution offshore data compiled from recent seismic reflection profiles, swath bathymetry acquisitions and industrial seismic reflection profiles. The new data set shows that the northern limit of the basin is oriented N49 degrees with right-stepping faults from the Bousekkour-Aghbal fault to the sinistral Bokkoya fault zone. This pattern indicates the presence of an inherited left-lateral basement fault parallel to the major inherited Nekor fault. This fault has been interpreted as a Quaternary active left-lateral transfer fault localized on weak structural discontinuities inherited from the orogenic period. Onshore and offshore active faults enclose a rhombohedral tectonic Nekor Basin. Normal faults oriented N155 degrees offset the most recent Quaternary deposits in the Nekor basin, and indicate the transtensional behaviour of this basin. The geometry of these faults suggests a likely rollover structure and the presence at depth of a crustal detachment. Inactive Plio-Quaternary normal faults to the east of the Ras Tarf promontory and geometries of depocentres seem to indicate the migration of deformation from east to west. The local orientations of horizontal stress directions deduced from normal fault orientations are compatible with the extrusion of the Rifian units and coherent with the westward rollback of the Tethyan slab and the localization of the present-day slab detachment or delamination.

In Western Mediterranean, the Betic-Alboran-Rif orocline accommodates the WNW–ESE convergence between the Nubia and Eurasia plates. Recent geodetic data show that present-day tectonics in northern Morocco and southernmost Spain are not compatible with this simple two-plate-convergence model: GPS observations indicate significant (2-4 mm/a) deviations from the expected plate motion, and gravity data define two major negative Bouguer anomalies beneath the Betic and south of the Rif, interpreted as a thickened crust in a state of non-isostatic equilibrium.

In this paper, we present the first estimate of the Holocene deformation along the southern front of Gibraltar arc (Morocco) and the first field constraints on the local 1755CE Fes-Meknes surface rupturing earthquake which could be associated to the “Great Lisbon Earthquake” (M>8.5) in November 1st, 1755. Using satellite imagery, aerial photographs and field investigations, we carried out a morphotectonic study along the ~150km-long Southern Rif Front (SRF) to identify the most recent evidences of tectonic activity. Analyzed offset alluvial deposits confirm that (i) the last ~5ka cumulative deformation leading to a slip rate of ~3.5±1mm/yr for this segment of the SRF is consistent with the GPS derived horizontal shortening rate of 2–4mm/yr and (ii) a recent major earthquake ruptured a~30km-long segment along the SRF. Based on deposits dating and historical seismicity we propose that this seismic event occurred in 1755 as a local earthquake. Even though this 1755 local event cannot be considered as a strong aftershock of the main Lisbon seismic event (M>8.5), their temporal closeness, their occurrence under the same convergent stress regime (~NNW-SSE-oriented compression) and the fact that Fes-Meknes area was strongly shaken during the Lisbon earthquake, raises the question of the possible triggering of the Fes earthquake. Anyway, our new results suggest that most of the Nubia-Rif belt convergence is accommodated by the SRF, making it potentially the most destructive structure of the Rif.

The Betic-Rif orocline surrounding the Alboran Sea, the westernmost tip of the Mediterranean Sea, accommodates the NW–SE convergence between the Nubia and Eurasia plates. Recent GPS observations indicate a ∼4 mm/yr SW motion of the Rif Mountains, relative to stable Nubia, incompatible with a simple two-plate model. New gravity data acquired in this study define a pronounced negative Bouguer anomaly south of the Rif, interpreted as a ∼40 km-thick crust in a state of non-isostatic equilibrium. We study the correlation between these present-day kinematic and geodynamic processes using a finite-element code to model in 2-D the first-order behavior of a lithosphere affected by a downward normal traction (representing the pull of a high-density body in the upper mantle). We show that intermediate viscosities for the lower crust and uppermost mantle (1021–1022Pas) allow an efficient coupling between the mantle and the base of the brittle crust, thus enabling (1) the conversion of vertical movement, resulting from the downward traction, to horizontal movement and (2) shortening in the brittle upper crust. Our results show that incipient delamination of the Nubian continental lithosphere, linked to slab pull, can explain the present-day abnormal tectonics, contribute to the gravity anomaly observed in northern Morocco, and give insight into recent tectonics in the Western Mediterranean region.

We present results of a geomorphological and morphotectonic analysis of the northeastern part of the Rif. We show that the present day kinematics of the Rif is characterized by active deformation along the Trougout and Nekor faults in the North-East. Digital Elevation Models of offset drainage features (streams, fluvial terraces) allow determining a normal-left-lateral motion along the Trougout fault and a left-lateral strike-slip motion along the Nekor fault. Preliminary 3He cosmogenic dates of tectonic markers yield vertical and horizontal slip rates of ∼0.9mm/yr and ∼0.5mm/yr, respectively along the Trougout fault. The present-day localized transtension seen in the north-eastern Rif morphology (Ras Tarf) is coeval with uplifted marine terraces near the Al Hoceima Bay. U/Th dating of shells yield an average uplift rate of ∼0.2mm/yr during the past 500ka. These data show that active transtension in the northeastern Rif is also associated with uplift. These new morphotectonic constraints are consistent with the GPS measurements showing southwestward overall motion of most of the Rif belt with respect to stable Africa.