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The Dead Sea Transform (DST) extends from the Red Sea to the East Anatolian Fault, displaying various structural styles along its ~1100 km length. In this study, we combine previous work with new mapping of fault patterns and displacements, geochronological data, and analogue and numerical modeling to provide new insights on the temporal evolution of the DST. In the southern DST, we mapped a 30 km wide distributed shear belt along the eastern margin of the Gulf of Aqaba (GOA), consisting of a distributed shear faulting, similarly to the western belt in Sinai. Total left lateral offset across the eastern distributed shear belt is ~ 15 km, with offset across individual faults ranging from a few meters up to 5.7 kilometers. Ar-Ar dating of sheared basalt dikes and U-Pb dating of calcite cements in faults indicate that the distributed shear system was activate between 22-16 Ma, overlapping with the rifting of the proto Red Sea and Gulf of Suez. This distributed shear is observed along the GOA and the deformed area narrowed along the Arava Valley. Distributed shearing marks the initial stage of continental break-up along the DST, which was abandoned by faulting concentration within the GOA and propagation of the DST towards the north. The structural analysis of bathymetry data from the GOA and fault mapping along the entire DST highlight various structural styles: rotational transtension within the GOA, narrowing to simple strike-slip faulting of the Wadi Araba and Jordan Valley, and pull-apart basins along the Dead Sea, Sea of Galilee and Hula Basin. These structures are linked at depth to the principal displacement zone, nowadays-active plate boundary. Our analogue model produces similar structural styles and with the seismicity data it confirms that deformed area narrowed in the more recent stage of deformation. We also present an approach based on the boundary element method at the regional scale to test the structural interpretation of a complex transpressional mountain range of Lebanon Restraining Bend. These results are validated by structural evidences and highlight that various structural styles lead to formation of Mt. Lebanon, Anti-Lebanon and Palmyrides structures. This review study of the DST emphasizes the role of structural styles, inherited structures and relative movement between tectonic plates in the transform continental break-up evolution.

The undersea portion of the Northern Apennines is characterized by blind thrust faults running parallel to the Adriatic Sea coastline in northeastern peninsular Italy. These thrusts are buried below a thick cover of syntectonic Quaternary deposits. Their elusive geological signature at shallow depths and the low seismicity associated with them gave rise to diverging interpretations and views concerning the current activity of these thrusts and their earthquake potential.On 9 November 2022, a seismic sequence started with an Mw 5.5 earthquake in the Pesaro Offshore. Hypocentral depth, focal mechanism, and aftershocks location all suggest that the earthquake was generated by one of the outermost thrusts of the Northern Apennines front that was already mapped as a potential seismogenic source in the DISS database (https://diss.ingv.it/diss330/sources.php?ITCS106).We present a 3D reconstruction of the thrust system that caused the Pesaro Offshore seismic sequence obtained through the reinterpretation of publicly available seismic reflection profiles and well logs. The 3D geometry and size of the thrust activated during the seismic sequence suggest that it can also host larger earthquakes. We also present the application of a well-established workflow for calculating the slip rates of this buried thrust already tested in nearby structures. The outcomes of this study represent a step forward for earthquake and tsunami hazard models, the study of the seismic source, the enhancement of earthquake location by mix and match of seismological and geological independent data, and the expected kinematics of future potential earthquake ruptures.These results are particularly relevant in offshore areas, where neither surface co-seismic ruptures nor GPS/InSAR deformation data are available in the aftermath of a significant earthquake. In these cases, multichannel seismic reflection profiles represent the only tool to appraise the subsurface structural setting.

Strain and kinematic indicators are frequently investigated to assess the type, magnitude, and orientation of deformation fields. Typically, their analysis ranges from the outcrop to the thin section scale. The present study characterizes the structural and mineralogical development of a phyllosilicate-rich fault gouge from the core of a major strike-slip fault on the eastern margin of the Gulf of Aqaba. We used transmission electron microscopy and focused ion beam techniques to explore shear deformation structures down to the nanoscale. The fault gouge was differentiated at the micron-submicron scale into chlorite-rich and illite-rich bands. The observed nano-kinematic shear sense indicators were SC/SCC’ fabrics in phyllosilicate bands, inclined axial planes in kink-folded illite and chlorite plates, platy hematite clasts inclined against the shear direction, and a σ-type clast system with recrystallized material in strain shadow wings around the clasts. These indicators provide a consistent set of criteria to determine shear sense in phyllosilicate-rich fault gouges.

The southern Dead Sea Transform (SDST) is an active left-lateral transform plate boundary that extends from the Sinai triple junction to the Lebanon restraining bend, separating the Arabian and Sinai plates. In this study, we analyze structural variations along the SDTS, and reproduce these variations in a 4D analogue model. From south to north, the structural styles along the SDTS indicate (1) rotational transtension within the Gulf of Aqaba, (2) pure strike-slip in Wadi Araba and Jordan River valley, and (3) pull-apart basins in the Dead Sea, Sea of Galilee and Hula basin. These different structural styles were replicated experimentally in an analogue model incorporating transtension with minor rotation along a kinked plate boundary. Our 4D model produced a deep southern depression with en echelon faults corresponding to the Gulf of Aqaba, a simple strike-slip fault system without vertical displacement reflecting the Wadi Araba and Jordan Valley, and a set of pull-apart basins reminiscent of the Dead Sea, Sea of Galilee and Hula basins. The accurate reproduction of the structural styles along this 600km-long plate boundary segment constrains the relative movement between the Arabian and Sinai plates to a simple combination of transtension with minor rotation, thereby negating the earlier hypothesis of Euler pole shift during the tectonic evolution of the SDST.

This presentation describes the structure and morphologies associated with seafloor spreading in the Red Sea inferred from bathymetric, gravity, magnetic and seismic data. We show that the orientation of the structures is consistent with an Arabia-Nubia Euler pole located within the 95% confidence of Ar-Rajehi et al, (2010) Euler pole and with the tectonic model initially proposed by Girdler (1984). At the Red Sea scale, our model shows that a spreading axis extends along its entire length, even though it is mostly covered by allochthonous Middle Miocene salt and Late Miocene minibasins flowing inward from the margins. In the northern Red Sea, oceanic basement is only exposed through small windows within the salt, forming a series of deeps. The seafloor segments symmetrically bisect the new ocean in the south. Right-stepping transform faults that cluster near Jeddah, Zabargad and Ikhwan Islands offset the ridge axis as spreading is getting more oblique towards the Euler Pole. The northern, central and southern Red Sea segments display a well-developed mid-ocean ridge flanked by landward-dipping volcanic basement, typical of slow spreading ridges. In the northern magma poor spreading segment, mantle exhumation is likely at the transition between continental and oceanic crust. Transpression and transtension along transform faults accounts for the exhumation of the mantle on Zabargad Island as well as the collapse of a pull-apart basin in the Conrad deep.We propose a new structural model for the Red Sea constrained by the geodetic rules of tectonic plates movements on a sphere. Finally, we discuss the effect of the Danakil microplate on the ridge morphology and show that the Arabia-Nubia-Danakil triple junction is likely located further north than previously described, around 18±0.5°N, where we observe a shift in the ridge axis orientation as well as in the spreading orientation.

The Jizan region of southwest Saudi Arabia contains large industrial point sources of CO2 and potentially the capacity to dispose substantial quantities of this gas by the subsurface mineralization of local basaltic rocks. Monte Carlo estimates suggest that the total CO2 mineralization capacity of the mafic igneous rocks in the Jizan area is ~4.2 Gt CO2, which is sufficient to store all of the carbon emissions from the local industrial facilities for four hundred years. Significant volumes of basalt were erupted in the region during the late Oligocene in a continental rift before the opening of the Red Sea. These rocks consist of lava flows and volcaniclastics intruded by dikes and shallow plutons. They are densely fractured and variably altered to chlorite-epidote-calcite assemblages. Dissolution rate measurements performed at 25 oC of four variably altered basaltic rocks from the region demonstrate their ability to increase fluid pH and liberate substantial Ca and Mg to the fluid phase. Reaction path calculations suggest that water charged CO2 will readily carbonate when interacting with the basaltic rocks at both 25 and 100 oC. Reactive transport calculations, however, suggest that while such carbonation reactions will be slow at 25 oC, these would fix more than 95% of injected water-dissolved CO2 within five years at 100 oC. Taken together, the results of this study indicate the likely success of large-scale subsurface carbon storage efforts through the subsurface carbonation of basaltic rocks in the Jizan region.

This study aims to characterize fracture permeability in altered Oligocene-Early Miocene basalts of the Jizan Group, which accumulated in half grabens during the continental rift stage of Red Sea evolution. Unlike fresh basalts, the Jizan Group was affected by low temperature hydrothermal metamorphism, which plugged the original matrix porosity in vesicles, breccias, and interflow layers with alteration minerals. On the other hand, the basalts are pervasively shattered by open closely spaced fractures in several directions. Characterization of these fractures is essential to reducing the fracture permeability uncertainty for mineral carbonation by the dissolved CO2 process such as Carbfix.Conventional measurements of fracture orientations and densities were initially taken at outcrops of the Jizan Group to characterize the fracture network. Photogrammetry of drone images covering larger areas were then used to create 3D models of the outcrops using Agisoft Metashape, which were analyzed for fracture geometries using Cloud Compare. The automated analysis of fracture orientations and densities compared well with conventional manual measurements. This gives confidence in semi-automated dronebased fracture characterization techniques in 3D, which are faster and less labor intensive, especially for characterization of large and difficult to reach outcrops.Our fracture characterization will be used to construct 3D fracture permeability models of the Jizan Group for combined physical and chemical simulation of injection of dissolved CO2 from industrial sources into basalts. This will provide essential parameters to mitigate geological risks and to determine depth, spacing, and injection rates in CO2 disposal wells.

The northern Apennines foredeep is characterized by a Plio-Pleistocene tectonic activity whose driving structures (thrust faults and related anticlines) are always buried by a high amount of syntectonic sediments, both onshore (Po Plain) and offshore (Adriatic Sea), thereby leaving subtle or none apparent signatures in the topo-bathymetry. Compared to the rest of Italy, this area has a relatively moderate earthquake hazard, but historical reports and instrumental recordings testify for significant seismicity. Seismological analyses of recent sizeable earthquakes (e.g., the Mw 6.1, Emilia earthquake in 2012) confirmed that the seismic activity is mainly due to the outermost northern Apennines buried thrusts. In this work, we reconstructed and parameterized the 3D geometry of such buried faults in an offshore sector just south of the Po River delta by interpreting a dense network of 2D seismic reflection profiles. The availability of two regional seismic reflection profiles, coupled with a detailed reconstruction of Plio-Pleistocene horizons, allowed us to restore the deformation cumulated by these thrusts. Our analysis was aimed at (1) establishing the age of inception of the main crustal thrusts, (2) reconstruct the main Plio-Pleistocene tectonic events affecting the study area, and (3) calculate the Plio-Pleistocene slip rates at different time slices and reporting them through probability distribution functions that take into account the uncertainties associated with horizon ages and restoration parameters. Our results show that the Plio-Pleistocene tectonic activity is variably distributed on different thrust faults and decreases exponentially over time after the Gelasian. The analysis performed on the most recent reflectors suggests that a low but not negligible tectonic activity characterizes the main thrusts in the studied region in the last 4-500 ka and hints at a residual activity that may last until the present.

Strike-slip structures are rarely validated because commonly used 2D restoration techniques are not applicable. Here we present the results of 3D numerical simulation of the restraining bends in Lebanon using boundary element methods of fault deformation implemented in MOVE™. The Lebanon restraining bend is the largest transpressional feature along the Dead Sea Transform (DST), and consists of two mountain ranges: Mount Lebanon on the west, dominated by the active Yammouneh fault, and the Anti-Lebanon Range to the east, influenced by the Serghaya and other faults. We built a new 3D geometrical model of the fault surfaces based on previous mapping of faults onshore and offshore Lebanon, complemented by interpretation of satellite images and DEM, and analogy with experimental models of restraining bend or transpressional structures. The model was simulated in response to the regional stress produced by the left-lateral displacement of the Arabian plate. The simulation accurately predicted the shape and magnitude of positive and negative topographic changes and faults slip directions throughout Lebanon. Furthermore, this simulation supports the hypothesis that the formation of the Anti-Lebanon Range was influenced by the intersection of the DST with the older Palmyrides belt, resulting in failed restraining bend. In contrast, the structure of Mt. Lebanon is similar to laboratory experiments of a restraining bend without inheritance. In addition, our simulation presents an approach of how strike-slip structural models may be validated in areas where subsurface data are limited.

Fault plane attitude and dimension are important parameters for deriving seismotectonic information or input data for earthquake hazard assessment and in this sense a complete 3D view and characterization of geological and structural elements is essential. However, there is always a trade-off between structural complexity and data availability at the scale of the designed application.In the last few years, merging public and confidential seismic reflection profiles and borehole data, were used in order to carry out a 3D reconstruction of fault planes and Plio-Pleistocene stratigraphic horizons in the northern Adriatic Sea, at the front of the northern Apennine fold-and-thrust belt and associated foredeep. The study area straddles the Italian coastline and subsurface data interpretation allowed us to reconstruct the structural setting of both onshore and offshore structures. Although it is known that this area has low rates of active tectonic deformation, it hosts important seismogenic faults associated with instrumental seismicity and historical earthquakes.The dense distribution of seismic reflection profiles allowed us to perform an accurate 3D reconstruction of almost 50 fault planes, of different dimensions and order of importance. Their geometrical and structural features helped to define the most recent tectonic phases. To this end, we also mapped several Plio-Pleistocene regional unconformities and integrated them with previously published reconstructions of key horizons.In some cases, where further published data were available, it was also possible to perform detailed cross sections whose restoration allowed us to reconstruct the post-Miocene (5.33 Ma) slip-rate history of some important tectonic structures with a detail of ~1 Ma. The 3D geological model revealed several structural features like fault continuity and terminations, level of connectivity, presence of lateral ramps, along strike variations of displacement that could not be fully addressed using cross sections alone.

The Dead Sea Transform is an active left lateral, strike-slip plate boundary. The Gulf of Aqaba corresponds to its southern segment, where the largest amount of opening is observed. The gulf itself is deformed by a set of en echelon faults which are bounded by normal faults. These en echelon faults show structural styles of Riedel shears which are typically observed in strike-slip tectonics. However, their orientation is the opposite to the one observed in well described models or natural cases. In this study, we compare a compiled dataset to analogue models which simulate the displacement in various strike-slip systems. This comparison to a sandbox model highlights the importance of the tectonic load in a strike-slip fault system. The model is composed of two base plates with only one straight velocity discontinuity. X-Ray Computed Tomography is used as a technique to carry out a 4D analysis of internal fault structures of the model. The 10°-transtensional model generates a set of Riedel shear faults, which merge during the later stages of deformation. The 30°-transtensional tectonic load shows two major steep bounding faults with a dip-slip component and a set of en echelon faults - opposite Riedel shears in between them. A higher amount of transtension rotates the classic Riedel shear faults to the opposite position. This fault pattern is very similar to the one observed in the Gulf of Aqaba, where the internal fault system is composed of opposite Riedel shears bounded by normal faults. These observations can increase the understanding of the structural styles seen in the Gulf of Aqaba. Moreover, our study describes a new strike-slip fault system.

Strike-slip motion is a fundamental tectonic process around the globe often resulting in prominent surface expressions. The full reconstruction and comprehension of strike-slip dominated structures can be a major challenge due to the complexity of the associated fault patterns. Further complexities occur when strike-slip dominated structures in the foreland interact with thrust belt fronts. Starting from a well-studied natural example (the Sciacca Fault Zone in the Sicilian Channel, Italy) we ran a set of analogue models simulating the interaction between strike-slip dominated fault zones and thrust structures using quartz sand as the analogue material and X-Ray Computed Tomography as a technique to carry out a 4D analysis of model internal structures. During a first phase, a thrust belt was created in our models, which was subsequently affected by a perpendicular fault system that underwent either pure strike-slip, 10°-, 20°-, 30°-transtensional, or 10°-, 20°-, 30°-transpressional motion. In general, transpressional models form pop-up structures, while the pure strike-slip model develops one sub-vertical fault bounded by two converging reverse faults. The 10˚-transtensional model generates a set of Riedel shear faults, which merge during the later stages of deformation. This model also shows a positive elevation change along the strike-slip dominated structures near the intersection with the thrust belt. The 20˚-transtensional model contains some Riedel shear faulting as well, but is dominated by two normal faults with steep dip angles and some minor sub-vertical strike-slip faults in between. This fault architecture is also observed in our 30˚-transtensional model. Three different tectonic regimes interacting with pre-existing and newly formed thrust front led to very different structural settings. These results were of help in better defining the tectonic regime that controlled the strike-slip dominated part of the Sciacca Fault Zone, but they show a fair match with other natural examples as well.

Highlights • A structural map of the northern part of the Capo Granitola-Sciacca strike-slip Fault Zone (Sicilian Channel) has been produced. • Numerous magmatic manifestations in addition to those already known in the Graham and Terrible banks, have been recognized. • A relationship between magmatism and structures associated with the Capo Granitola-Sciacca Fault Zone, has been documented. • A mechanism of non-plume origin is proposed for the magmatism observed in the study area. The tectonic framework of the northern sector of the Capo Granitola-Sciacca Fault Zone (CGSFZ), a NNE-oriented lithospheric strike-slip fault zone located in the Sicilian Channel (southern Italy), has been reconstructed with the aim to clarify the relationships between geometry and kinematics of the structures and the occurrence and distribution of the magmatic manifestations observed in the area. This has been achieved by the interpretation of a large dataset composed of 2-D multichannel seismic profiles, Chirp profiles, magnetic data and borehole information. In addition to the volcanic edifices known in the Graham and Terribile banks, this study has allowed to recognize several other magmatic manifestations. The magmatic occurrences consist of small volcanic cones, buried magma ascents and potential igneous sills. The CGSFZ is bounded by two strike-slip fault systems, the Capo Granitola Fault System (CGFS) to the west and the Sciacca Fault System (SFS) to the east, dominated by positive flower structures generated by tectonic inversion of NNE-oriented late Miocene extensional faults. Only the southern part of the CGFS shows the presence of a sub-vertical, N-S oriented strike-slip master fault. The sector between the two fault systems does not show a significant Pliocene-Quaternary tectonic deformation, except for its southern part hosting the Terribile Bank, which is dissected by WNW to NW-trending normal faults developed during late Miocene and later reactivated. This set of faults is currently active at the Terribile Bank, whereas is buried by Pliocene-Quaternary deposits in the central and northern sectors of the CGSFZ. The observed magmatism is driven by a mechanism of non-plume origin. Magmas have used as open paths the faults of the CGFS and SFS, which cut the whole lithosphere reaching the asthenosphere and producing partial melting by simple pressure release. Most of the magmatism develops along the strike-slip master fault associated with the CGFS and the normal faults affecting the Terribile Bank. The magmatic feeding of the Terribile Bank would be related to lateral magma migration coming from the structures of the SFS, which would use the open pathways represented by active normal faults. In the central-northern part of the CGSFZ, magmas migrate upward along lithospheric faults, then move laterally and rise toward the surface through NNE and NW-trending buried normal faults. These late Miocene faults do not reach the surface, and this may have favoured the emplacement of igneous sills, which in turn may explain the observed volcanic centres.

Highlights • Active tectonics in Sicilian Channel • Analogue models of transcurrent structures • 3D fault pattern reconstruction Seismo-stratigraphic and structural analysis of a large number of multichannel seismic reflection profiles acquired in the northern part of the Sicilian Channel allowed a 3-D reconstruction of a regional NS-trending transfer zone which displays a transcurrent tectonic regime, and that is of broad relevance for its seismotectonic and geodynamic implications. It is constituted of two major transcurrent faults delimiting a 30-km-wide, mostly undeformed basin. The western fault (Capo Granitola) does not show clear evidence of present-day tectonic activity, and toward the south it is connected with the volcanic area of the Graham Bank. The eastern fault (Sciacca) is structurally more complex, showing active deformation at the sea-floor, particularly evident along the Nerita Bank. The Sciacca Fault is constituted of a master and splay faults compatible with a right-lateral kinematics. Sciacca Fault is superimposed on an inherited weakness zone (a Mesozoic carbonate ramp), which borders to the east a 2.5-km-thick Plio-Quaternary basin, and that was reactivated during the Pliocene. A set of scaled claybox analogue models was carried out in order to better understand the tectonic processes that led to the structural setting displayed by seismic data. Tectonic structures and uplift/subsidence patterns generated by the models are compatible with the 3-D model obtained from seismic reflection profiles. The best fit between the tectonic setting deriving from the interpretation of seismic profiles and the analogue models was obtained considering a right-lateral movement for the Sciacca Fault. Nevertheless, the stress field in the study area derived from GPS measurements does not support the present-day modelled right-lateral kinematics along the Sciacca Fault. Moreover, seismic events along this fault show focal mechanisms with a left-lateral component. We ascribe the slip change along the Sciacca Fault, from a right-lateral transcurrent regime to the present-day left-lateral kinematics to a change of principal horizontal stress direction starting from Late Pliocene.

Mass-transport deposits (MTDs) are well developed on the slope of the Eocene Sobrarbe delta (Ainsa Basin, Spanish Pyrenees) and are studied in order to improve the understanding of soft sediment deformation in MTDs. The five examples illustrate the distinction between the extensional zone and the compressional domain. The upslope domain is illustrated by a set of three stacked nummulite-rich slid layers. They are deformed by load structures suggesting density inversion and sinking of nummulite gravel down into the underlying silty-shaly material. Post-sliding deformation is evidenced from small-scale roll-overs, neptunian dykes and syn-sedimentary normal faults. Slow extensive deformation has continued in the substratum of the scar after the main sliding episode. Soft-sediment deformation is less obvious in large displaced blocks where deformation is limited at the periphery of the blocks. Imbricate thrusts, formed on the side of a sliding layer, illustrate structures related to displacement. Striations on the thrust planes indicate that sliding occurred along the strike of the imbricate slices. The km scale Castellazo outcrop shows slump folds resting over a basal debris flow.