United States

Diagnostic morphological features (e.g. rectilinear seafloor scarps) and lateral offsets of the Upper Quaternary deposits are typically used to infer offshore active faults. These structures are not necessarily capable of producing large earthquakes as they could be shallow and formed in response to local stresses. We present a multiscale approach to reconstruct the structural pattern in offshore areas and distinguish between shallow, non-seismogenic, active faults, and deep blind faults, potentially associated with large seismic release. The approach is based on the interpretation of seismic reflection profiles with different resolution/penetration and the quantitative morphometric analysis of multibeam bathymetry. The site chosen for testing the method is the Sant’Eufemia Gulf (south-eastern Tyrrhenian Sea) because it is a natural laboratory to investigate the relationships between regional and local processes associated with a slab tear fault (e.g. Rosenbaum et al., 2008) and crustal structures controlling the Plio-Quaternary tectonic evolution (e.g. Brutto et al., 2016). Data highlights the occurrence of three major tectonic events since the Late Miocene. The first extensional or transtensional phase occurred during the Late Miocene. Since the Early Pliocene, a right-lateral transpressional event caused the positive inversion of deep (&gt; 3 km) tectonic features, and the formation of NE-SW faults in the central part of the gulf. Also, NNE-SSW to NE-SW trending anticlines (e.g. Maida Ridge) developed in the eastern sector. Since the Early Pleistocene (Calabrian), shallow (&lt; 1.5 km) NNE-SSW oriented structures formed in a left-lateral transtensional regime. The results of this work integrated with literature data indicate that the transpressional/transtensional structures developed in an ~E-W oriented principal displacement zone extending from the Sant’Eufemia Gulf to the Ionian offshore. The strike-slip zone likely represents the upper plate response to the development of a slab tear fault.  The quantitative morphometric and bathymetric analyses indicate that NNE-SSW to NE-SW trending anticlines were negatively reactivated during the last tectonic phase. We suggest that the deep structure below the Maida Ridge may correspond to the seismogenic source of the large magnitude earthquake that struck the Calabrian region in 1905. The multiscale approach contributes to understanding the tectonic imprint of active faults with different hierarchical order developed in a strike-slip zone orthogonal to the Calabrian Arc.

SGI 2021

Geometry and kinematics of offshore active faults revealed by an integrated multiscale method

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L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


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With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


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Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

Diagnostic morphological features (e.g. rectilinear seafloor scarps) and lateral offsets of the Upper Quaternary deposits are typically used to infer offshore active faults. These structures are not necessarily capable of producing large earthquakes as they could be shallow and formed in response to local stresses. We present a multiscale approach to reconstruct the structural pattern in offshore areas and distinguish between shallow, non-seismogenic, active faults, and deep blind faults, potentially associated with large seismic release. The approach is based on the interpretation of seismic reflection profiles with different resolution/penetration and the quantitative morphometric analysis of multibeam bathymetry. The site chosen for testing the method is the Sant’Eufemia Gulf (south-eastern Tyrrhenian Sea) because it is a natural laboratory to investigate the relationships between regional and local processes associated with a slab tear fault (e.g. Rosenbaum et al., 2008) and crustal structures controlling the Plio-Quaternary tectonic evolution (e.g. Brutto et al., 2016). Data highlights the occurrence of three major tectonic events since the Late Miocene. The first extensional or transtensional phase occurred during the Late Miocene. Since the Early Pliocene, a right-lateral transpressional event caused the positive inversion of deep (> 3 km) tectonic features, and the formation of NE-SW faults in the central part of the gulf. Also, NNE-SSW to NE-SW trending anticlines (e.g. Maida Ridge) developed in the eastern sector. Since the Early Pleistocene (Calabrian), shallow (< 1.5 km) NNE-SSW oriented structures formed in a left-lateral transtensional regime. The results of this work integrated with literature data indicate that the transpressional/transtensional structures developed in an ~E-W oriented principal displacement zone extending from the Sant’Eufemia Gulf to the Ionian offshore. The strike-slip zone likely represents the upper plate response to the development of a slab tear fault.  The quantitative morphometric and bathymetric analyses indicate that NNE-SSW to NE-SW trending anticlines were negatively reactivated during the last tectonic phase. We suggest that the deep structure below the Maida Ridge may correspond to the seismogenic source of the large magnitude earthquake that struck the Calabrian region in 1905. The multiscale approach contributes to understanding the tectonic imprint of active faults with different hierarchical order developed in a strike-slip zone orthogonal to the Calabrian Arc.

poster

Lower Cretaceous carbonate platforms record distinctive facies in the area of Getic unit defined Beriasian, Valanginian, Hauterivian and Urgonian like facies. These deposits result from the continuous trend of shallow-water sedimentation that started in the Middle Jurassic time. Recent studies on the Getic carbonate platform succession focused on outcrops in Romania and Bulgaria, whereas detailed investigation on the Serbian side of the Getic platform was limited to solving biostratigraphy, paleontology and facies distribution issues on local scale, mostly in northeastern Serbia. The most exhaustive research on the Getic platform in southern and central Serbia dates back to the 70s of last century (Jankičević, 1978). The study area is located in the Carpatho-Balkanides of Serbia, close to the town of Dimitrovgrad, and includes the narrow belt of Lower Cretaceous (Valanginian-Hauterivian) carbonate successions in the southern sector of the Getic Carbonate Platform. The identified carbonate facies consist of foraminifera mudstone to wackestone, bioclastic wackestone, (fenestral) peloidal grainstone, skeletal packstone and mixed siliciclastic sediments (sandstone) indicative of different environments from shallow platform interior to slope and basin. The data from Dimitrovgrad locality with beds fully made of Bacinella sp. show the significant changes in environment of deposition from platform interior to reef depositional environment. Besides that, the pyrite rich siliciclastics provide the information of transition to slope environment. The distribution of different facies show rapid lateral and vertical changes of depositional environments varying from platform interior to reef and finally to the slope and basin conditions.

New data from the Lower Cretaceous carbonate platform deposits of Dimitrovgrad section (Southeastern Serbia)

The Monte Amiata volcano is located in southern Tuscany, at the geographical overlap of the Tuscan magmatic province with the Roman magmatic province. It is a small Pleistocenic volcano made up prevalently by viscous lava flows and domes ranging in composition from trachydacites to olivine latites. The volcanic rocks emplaced in a very short period of time, between 305 and 231 ka (Laurenzi et al., 2015). Lava flows and domes are grouped into three main complexes, one for each stage of activity: the “Basal Trachydacitic Complex” (BTC), the “Dome and Lava flow Complex” (DLC) and the  “Olivine Latite  final lavas” (OLF;  Conticelli  et al.,  2015;  Marroni  et al., 2015). The most important petrographic characteristics of Monte Amiata volcanic rocks are represented by: i) the occurrence of sanidine megacrysts, mostly confined in the rocks emplaced in concomitance with the second stage of the Monte Amiata volcanic activity (DLC); ii) the occurrence of rounded fine-grained mafic enclaves with cuspidate margins convex toward the host, which constitute proof of the mingling process that took place at Monte Amiata and that possibly triggered the eruptions of these highly viscous magmas; iii) the occurrence of mafic olivine latitic lava flows, emplaced as the final product of the volcanic activity and characterised by an intermediate composition between the early silica-rich volcanic rocks and the most mafic enclaves hosted by Monte Amiata volcanic rocks. Here, we present the preliminary results about the origin, the evolution, and the distribution of the mafic enclaves hosted by the Monte Amiata lavas and domes. To do this, thin sections were studied under the petrographic microscope, chemical analyses of whole rocks and enclaves and their rock-forming minerals were carried out. A statistical survey on the magmatic enclaves distribution and their size variations was also made. These preliminary results suggest that Monte Amiata mafic enclaves change in composition and increase in size and abundance from those hosted by domes and lavas with the highest silica contents to those hosted by domes and lavas with the lowest silica contents.

Study of the origin, the evolution, and the distribution of Monte Amiata mafic enclaves

The Early Cretaceous ammonite fauna is well-known from several localities in Central Serbia. Discovered Lower Cretaceous sediments extend in the narrow belt Belgrade-Kosmaj-Topola-Gledić Mts. (Anđelković, 1954). The wide study area belongs to the: Eastern Vardar Ophiolitic Unit (Schmid et al., 2008), Main Vardar Zone (Karamata, 2006) or Northern part of Central Vardar Subzone (Dimitrijević, 1997). Newly collected ammonite assemblages described herein came from Kotraža section located SW of Topola in Šumadija District. In Serbian geological literature, the oldest Cretaceous sediments of this area are described as Barremian-Aptian shallow-marine limestones, which are overlying younger Upper Albian glauconitic sandstones, marls and marly sandstones (Anđelković, 1954). The Upper Albian sediments of Kotraža section profile are represented by 11 m thick glauconitic sandstones and marly sandstones bearing rich fauna of ammonites, belemnites, gastropods and plant tissues. These sediments yielded a rich ammonite fauna that includes representatives of three superfamilies of Phylloceratoidea, Tetragonitoidea and Desmoceratoidea. The lower and middle part of the profile is dominated by 8 m thick glauconitic sandstones and reddish Fe-rich sandstones from which some ammonite taxa are isolated: Anisoceras sp., Mortoniceras sp., Phylloceras (Hypophylloceras) velledae and Puzosia mayoriana. The uppermost part of the profile, consists of 3 m thick sandy marls and marly sandstones with dominant fauna of genus Puzosia and other species: Kossmatella agassiziana and Puzosia (Puzosia) mayoriana. The studied deposits with ammonite assemblages belongs to the lower part of the Mortoniceras perinflatum Zone (sensu Reboulet et al., 2018).

Late Albian ammonites from Kotraža (Topola area, Central Serbia) and their biostratigraphic implications

More than 100 years after the devasting Messina-Reggio Calabria earthquake (M=7.1), the largest seismic event ever recorded in southern Europe in the instrumental epoch, its causative seismic source is still unknown, and the several rupture models proposed in the last decades are far from any shared solution. Data interpretation on a new dataset of sub-seafloor geophysical soundings with unprecedented resolution, relocated seismicity, and Vp model, together with morphotectonic investigations and inverse modelling of available levelling data, provide additional constraints on the deformation mechanisms and seismotectonics of the Strait of Messina area. High-resolution seismic lines in the offshore, along with displaced Quaternary marine terraces on land, point to active deformation along a previously unmapped ~ 34.5 km-long extensional fault. The spatial distribution of relocated earthquakes highlighted that a cut-off of the seismicity occurs within the crustal depth. The seismic discontinuity roughly delineates a foreland-dipping and low-angle discontinuity apparently confirming previous studies predicting low-angle seismogenic sources for the 1908 seismic event. However, according to the overburden stress and the attitude of the discontinuity, stress analysis suggests that a seismic slip is unlikely along it. This, therefore, weakens the hypothesis that a large earthquake may have nucleated along a low-angle discontinuity. Rather, aseismic creeping is instead expected since movement is allowed only by assuming a mechanical weakness of the plane. This mechanical behavior is currently also supported by the large interseismic strain-rate recorded in the area. Both seismic tomography and crustal-to-subcrustal scale 3D-modelling strongly suggest a cause-and-effect relationship between slab retreat, mantle wedging, uplift in the upper plate block, and active extension in the Strait of Messina area. Lithospheric doming of the upper plate is here interpreted to be the main process controlling uplift in the Peloritani Mts. of Sicily and subsidence in the Strait of Messina region where deformation is mainly accommodated by the weak low-angle discontinuity. In this frame, an almost aseismical slip toward the foreland of the low-angle discontinuity is here accounted to produce stress perturbation in the area. Coulomb stress change modelling revealed that simulated normal slip on the foreland-dipping discontinuity can induce additional stress and promote failure in the overlying brittle faults. An excellent fit between calculated and observed subsidence is achieved by geodetic data inversion that resolved a normal slip on the low-angle discontinuity and a transtensional (slightly left-lateral) motion on the 34.5 km-long and previously unknown extensional fault. The fault-length along with the observed seafloor displacement make this tectonic structure as the most likely to have produced large earthquakes in the Strait of Messina area.

The Strait of Messina: Seismotectonics and the source of the 1908 earthquake

Evidence for the Early Jurassic Western Tethys rifting is in the Alps and the Apennines. This normal faulting phase dismembered a vast carbonate platform (Calcari Grigi and Calcare Massiccio platform) and produced a complex paleogeographic setting made of intrabasinal morphostructural highs and deeper-water basins (i.e. pelagic carbonate platform or PCP/basin system). Basin-fill pelagites and their geometrical and facies variations highlight this complex architecture. There are growing clues for Early Cretaceous, post-rift, synsedimentary normal faults affecting and displacing the margins of PCP, as in the Umbria-Marche-Sabina Domain and the Trento Plateau-Lombardy Basin. Typical stratigraphic and sedimentological features of this syndepositional tectonic phase include: i) the back-stepping of PCP margins, ii) the deposition of calciclastic bodies, iii) the occurrence of neptunian dykes, and iv) the development of angular unconformities. Geological mapping in the Narni-Amelia Ridge allowed to identify field-evidence for this Cretaceous normal faulting. A polygenic breccia (“Mt. Cosce Breccia”) made of clasts of lithologies not younger than the Early Cretaceous, dispersed in a matrix of Maiolica-type facies, rests through an erosional surface on a Jurassic horst-block of Calcare Massiccio. Comparable clastic deposits are embedded in the uppermost part of the Maiolica in hangingwall-basin successions, associated with soft-sediment deformation. Lower Cretaceous pelagites (Maiolica+Marne a Fucoidi) are locally seen onlapping the unroofed Calcare Massiccio, as well as infilling neptunian dykes. Impressive similarities were recognized along the Jurassic western margin (Ballino escarpment) of the Trento Plateau, albeit at a larger scale. Here, a Lower Cretaceous polygenic breccia (Ballino, Pregasio and Prabione breccias) bearing heterometric (up to >20 m across) blocks of Jurassic-Lower Cretaceous deposits referable to the Calcari Grigi Group, the basinal Lombardy Succession and the horst block-top Venetian Succession, occurs. The clasts are dispersed in a Maiolica-type matrix. The breccia rests unconformably on the Calcari Grigi Group and on several Jurassic units of the Lombardy basin-margin succession, and is accompanied by neptunian dykes made of Maiolica facies. Where preserved by Neogene Alpine deformations, Cretaceous normal faults were locally observed, sealed by the calciclastics and the uppermost part of Maiolica. Field-evidence suggests a phase of tectonic instability during the late Early Cretaceous, coeval with the deposition of the uppermost part of Maiolica, affecting PCP-basin systems in both Central Apennines and Southern Alps. Cretaceous faults locally re-activated Jurassic ancestors, locally had a higher angle than Jurassic faults, locally developed as new faults. The result was the displacement and rejuvenation of inherited Early Jurassic escarpments, or the backstepping of PCP-margins producing exhumation of Jurassic structural highs.

Tectono-stratigraphic evolution of Jurassic Tethyan rift basins in the Early Cretaceous: a comparison between the Central Apennines and the Southern Alps

The NNW-SSE trending Malta Escarpment (MESC) offshore eastern Sicily is accounted to have a significant role in the recent seismotectonic picture of the Western Ionian Basin and the Hyblean foreland domain, where some of the largest and most destructive Mediterranean earthquakes occurred (Boschi et al., 1995; Piatanesi&Tinti, 1998; Bianca et al., 1999; Azzaro&Barbano, 2000; Tinti et al., 2001, 2004; Rovida et al., 2016). Seismic data and bathymetric grids allow to better constrain the recent/active deformation pattern affecting the northern sector of the MESC. Accurate seafloor mapping and seismic profiling point to a 60 km-long, roughly N–S trending and E-dipping extensional faults belt slicing across the Ionian offshore between CataniaSiracusa.The fault belt deformed the seafloor producing up to 60 m-high fault scarps. Near-fault sediment pattern and displacement analysis provide constraints on the through-time faults activity and deformation rate. Fault parameters were achieved by 3D modeling and then used to derive expected magnitudes and their reactivation propensity. Moreover, empirical scaling relationships (Wells & Coppersmith, 1994; Leonard, 2010) point to a high seismic potential for the detected fault. This combined analysis pointed out how the longest (~60 km) and most continuous fault could be capable of generating M > 7 seismic events, putting forward strong seismotectonic implications for the adjacent and densely populated Hyblean Plateau. The expected magnitude and the estimated recurrence time interval (470-537yrs) are compatible with those inferred for large historical earthquakes that occurred in the area. However, by comparing the depicted tectonic pattern with other structural settings concerning passive margin worldwide (e.g., along the Pará-Maranhão Basin in the Brazilian equatorial margin, see Matos, 2000) and considering the occurrence of ductile layers in the sediment section (e.g. evaporites), part of the observed deformations (i.e. the seafloor scarps) should be also charged to large-scale slope instability or generated by accommodation space following salt migration in response to the overlying sediment load. Accordingly, seafloor deformation could be (partially)the result of this kind of process and this issue should be seriously considered in the seismotectonic analysis. Although our study highlights that classical tools used by marine geologists(i.e. high-resolution seismic data and bathymetric grids) work well in detecting offshore faulting, some other significant faults parameters, which are essential in the seismotectonic analysis (e.g. size parameters and slip rate,), need additional approaches to be achieved. In this view, computer-based 3Dmodelling can represent a starting point for further elaborations such as stress/strain analysis, back/forward and dislocation modeling, sediment decompaction, etc.

3D modeling and sequential back-restoration as tools for assessing faults deformation rate in offshore setting and estimation of their seismic potential

The Quaternary marks a time of important change in the tectonic regime that affected the central Apennine chain. The shift from the late Miocene-early Pliocene compressional regime to the late Pliocene-early Pleistocene extensional regime produced surface uplift of the chain, tectonic activity expressed along normal faults, and rapid evolution of the intra-montane basins. The development of several paleosurface levels in the central Apennines suggests the uplift was not constant through time; dating those paleosurfaces is critical for determining how uplift rates and landscapes changed through time. The Aterno and Tirino basins preserve a record of subplanar highlands that can be related to paleosurfaces. Recent studies on the Quaternary deposits in the L’Aquila Basin allowed the identification of the Valle Daria abandonment surface, which marks an important phase of base-level fall of the drainage system that occurred during the early Pleistocene (Gelasian). Although morphostratigraphic analysis well describes the evolution of these two basins during the Quaternary, the knowledge related to the higher paleosurfaces and their meaning in the landscape evolution is still poorly constrained. In this study, we applied advanced morphometric and morphostructural analysis to the Aterno and Tirino basins, with a focus on the identification of the main paleosurfaces, their dating, and reconstructions of the baselevel-fall variations of the drainage system through time. We used a 10-m resolution DEM to map the position and elevation ranges of the flat surfaces, extract the drainage system, and identify knickpoints and low-gradient levels. We then combined the morphometric results with the morphostratigraphy and tectonics of the area to define the paleosurfaces, correlate the levels, and assign them ages. We identified 4 main levels of paleosurfaces, the lowermost (P3 and P4) respectively related to Valle Daria (early Pleistocene, top Gelasian) and the top of Fosso Genzano Synthem (middle Pleistocene), the higher ones (P1 and P2) that have been related to the thrust-top basins of Monte Coppe (latest Messinian) and Rigopiano (late Zanclean). We finally applied linear inversion of the Aterno and Tirino drainage systems to infer the evolution of base-level and find a possible correlation with central Apennine uplift phases. Our results show three main events in the drainage baselevel-fall rate. The first two events occurred at ca. 3 Ma and 2 Ma, in accordance with the uplift and abandonment of P2 and P3, and the middle to late Pleistocene peak in base-level fall that could be related to changes in the Sulmona Basin and Pescara River systems.

Paleosurface mapping and Quaternary uplift evolution of the Aterno and Tirino Basins

Proofs of synsedimentary tectonics during the Early Permian in the central Southern Alps (cSA, N Italy) are recorded in the volcanic and terrigenous successions of the Laghi Gemelli Group, which are characterized by the occurrence of abrupt facies variations often associated with coarse-grained deposits. These features are generally attributed to syn-sedimentary tectonic activity demonstrated by the local occurrence of sediments deformation (Berra et al., 2011) such as liquefaction or slumping due to seismic shaking. Detailed fieldwork allowed us to recognize dewatering structures and sedimentary dikes, ball and pillars and small slumps, occurring along hundreds of mesoscopic faults showing meter-scale displacement in correspondence of high-angle conjugate systems as well as domino-style faults, often accompanied by growth structures. These structures are mainly concentrated in the fine-grained sediments of the Pizzo del Diavolo Formation, which were deposited on top of the volcaniclastic succession of the Ca’ Bianca Volcanite and crossed by seismogenic synsedimentary faults. The Permian synsedimentary structures of cSA are mostly associated with high-angle Andersonian normal faults which are combined with low-angle normal faults (LANFs) that developed along the interface between the Permian sedimentary cover and the Variscan basement (Zanchi et al., 2019). This LANFs system is relevant for the Permian hydrothermal circulation, resulting in widespread tourmalinites deposition along fault zones, and locally in U mineralization. According to our structural analysis the Permian tectonic setting is characterized by pure extension, dominated by ENE-WSW striking normal faults inverted during the Alpine shortening as high-angle reverse faults (Zanchetta et al., 2015).

Evidence of syndepositional tectonics during the Early Permian in the Orobic Basin (central Southern Alps, N Italy)

Seismic images are fundamental to interpret subsurface setting on both continental and marine environments. However, in carbonate systems, seismic response can be very difficult to be analyzed due to the petrophysical heterogeneities, being the interpretation particularly complicated when faults are present. In fact, faults rocks are generally characterized by different petrophysical properties with respect to the host rocks. Synthetic seismic forward modeling is a powerful tool to quantifying the seismic response associated with fault-related petrophysical changes, since input parameters can be modified. In this study, field and laboratory measurements are used to analyze the spectrum of the carbonate-bearing fault seismic response. Here, we focused on the carbonate ramp setting outcropping in the Majella Massif since it represents an excellent surface analogue of buried porous and faulted carbonate reservoirs worldwide. Density and porosity were measured through a helium pycnometer on representative fault (damage zone) rocks sampled at increasing distances from fault planes. Investigated damage zone samples, show both increased and decreased porosity with respect to the host rock, depending on the single fault characteristics. A 2D (12 km long) synthetic profile from the platform top to the basin, oriented SSE-NNW, was then carried out in Matlab simulating the outcropping architecture and spatial distribution of the sedimentary facies and of the faults. Together with a proper porosity variation related to facies distribution, the porosity along the damage zones (DZ) of the simulated faults was set according to the laboratory measurements. The low-frequency (40Hz) synthetic seismic profile shows marked diffraction hyperbolas in the modeled fault zones for faults characterized by higher porosity DZ where lower seismic velocity is expected. On the contrary, fault zone characterized by lower porosity DZ with respect to the host rock resulted to give a less clear seismic image. Going into the details, faults with decreased porosity and consequent increased seismic velocity of 1000 m/s in the damage zone respect to the host rock, do not show a visible difference in the seismic response if compared with the seismic image without modified petrophysical characteristics within the faults. On the other hand, faults with increased porosity and decreased seismic velocity of just 500 m/s respect to the host rock, show clear diffraction hyperbolas where their apexes correspond to the fault planes. Ongoing laboratory measurements and simulations changing geometries, thicknesses and orientations of the damage zones, are expected to help in improving the knowledge of fault seismic response. This work helps in bridging the gap between forward modeling and actual seismic imaging with large implications for hydrocarbon-reservoir characterization and the identification of potential CO2 or hydrogen storage sites.

Synthetic seismic forward modeling as a tool to assess the seismic signature of carbonate-bearing fault zones

The Eastern Mediterranean Sea results from an alternation between extensional and contractional phases. Although several geodynamic reconstructions have been proposed, its tectonostratigraphic evolution is still a matter of debate. The main tectonic phases that affected the area were the Mesozoic rifting, followed by a Cenozoic contractional phase, due to the inception of the convergence between Africa and Eurasia and the subduction of the oceanic lithosphere. From the Miocene, the opening of the Red Sea induced a rotation and northward migration of the Arabian Plate. At the same time, the rollback of the subducting oceanic lithosphere in the Central Mediterranean area favoured a westward escape of the Anatolian plate squeezed out by the northward migration of the Arabian Plate. Our study area is located in the easternmost portion of the Mediterranean Sea, offshore Turkey, Cyprus and Syria, on the ancient passive margin of the Tethys between the Arabian continental lithosphere and the African oceanic lithosphere. Along the Cyprus Arc, the Neo-Tethys oceanic crust is subducting toward NE. Most of the authors (Symeou et al. 2018 and references therein) suggested that this system is continuous from Cyprus to Syria. In this work, multi-channel seismic reflection profiles have been used to analyze the basement nature (oceanic vs continental), to recognize potential subduction zones and their lateral continuity, and to reconstruct the contractional events. Our data suggest a continental nature of the basement, excluding a continuous ophiolite complex and subduction in eastern Cyprus offshore. Most of the recent structures evidenced in the area derive from transpressional reactivation of inherited extensional fault systems.

Geometry and kinematics of offshore active faults revealed by an integrated multiscale method

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