Papers by Bernard Mercier de Lépinay
Bulletin of the Seismological Society of America
Earthquakes pose a major threat to the people of Haiti, as tragically shown by the catastrophic 2... more Earthquakes pose a major threat to the people of Haiti, as tragically shown by the catastrophic 2010 Mw 7.0 earthquake and more recently by the 2021 Mw 7.2 earthquake. Both events occurred within the transpressional Enriquillo–Plantain Garden fault zone (EPGFZ), which runs through the southern peninsula of Haiti and is a major source of seismic hazard for the region. Satellite-based Interferometric Synthetic Aperture Radar (InSAR) data are used to illuminate the ground deformation patterns associated with the 2021 event. The analysis of Sentinel-1 and Advanced Land Observation Satellite (ALOS)-2 InSAR data shows (1) the broad coseismic deformation field; (2) detailed secondary fault structures as far as 12 km from the main Enriquillo–Plantain Garden fault (EPGF), which are active during and after the earthquake; and (3) postseismic shallow slip, which migrates along an ∼40 km unruptured section of the EPGF for approximately two weeks following the earthquake. The involvement of seco...
HAL (Le Centre pour la Communication Scientifique Directe), Nov 1, 2021
HAL (Le Centre pour la Communication Scientifique Directe), Nov 15, 2021
(7) et l'équipe du projet OSMOSE (en tout 30 participants Haïtiens et Français)
International Geology Review, 2021
We present a new U-Pb zircon age and geochemical data from an intermediate calc-alkaline pluton w... more We present a new U-Pb zircon age and geochemical data from an intermediate calc-alkaline pluton with adakitic affinity from NW Hispaniola (Haiti). The data provide important constraints and offer new insight on the Late Cretaceous (~90 Ma) development and geological evolution of the Greater Antilles Arc (GAA). The pluton intrudes Cretaceous basalts and mafic basic tuffs of the volcanic arc domain in the Massif du Nord (northern Haiti), equivalent to the Tireo Fm (Cordillera Central) in the Dominican Republic. The calc-alkaline, low-K tonalite shows LREE enrichment, and HREE depletion and have geochemical features similar to adakites, including 67.11 wt.% SiO<sub>2</sub>, high Na<sub>2</sub>O contents (3.69 wt.%), and high Sr/Y (38.6). U-Pb SHRIMP zircon dating yielded a concordant <sup>206</sup>Pb/<sup>238</sup>U emplacement age of 88.9 ± 1.1 Ma, similar to other calc-alkaline intrusions in Hispaniola and Cuba related to the Cretaceous GAA. We link the presence of rocks with adakitic affinities in Eastern Cuba (La Corea and Sierra del Convento Mélanges), Haiti (Massif du Nord; present study), and Dominican Republic (Cordillera Central) with subduction of the Proto-Caribbean ridge and eastward (present coordinates) migration of the corresponding ridge-trench-trench triple junction since at least ~120 Ma in eastern Cuba to the mid-Cretaceous (~90 Ma) in Hispaniola. Here we show that this migration is not consistent with left-lateral oblique subduction and propose that it was not characterized by steady motion but by sudden jumps resulting from the segmentation of the proto-Caribbean ridge by transform faults. Ridge subduction and jumping triple point migration should have been active during the Late Cretaceous to early Tertiary, when the activity of the Proto-Caribbean ridge vanished.
Geochemistry, Geophysics, Geosystems, 2021
Based on 2D seismic profiles, multibeam and seabed grab cores acquired during the Garanti cruise ... more Based on 2D seismic profiles, multibeam and seabed grab cores acquired during the Garanti cruise in 2017, 1–5 km wide seabed giant polygons were identified in the Grenada basin, covering a total area of ∼55,000 km2, which is the largest area of outcropping polygonal faults (PF) ever found on Earth so far. They represent the top part of an active 700–1,200 m thick underlying polygonal fault system (PFS) formed due to the volumetric contraction of clay‐ and smectite‐rich sediments, initiated in the sub‐surface at the transition between the Early to Middle Pliocene. The short axes of the best‐fit ellipses obtained from a graphical center‐to‐center method were interpreted as the local orientation of a preferential contraction perpendicular to the creep deformation of slope sediments. In the North Grenada Basin, the polygons are relatively regular, but their short axes seem to be parallel to a N40°E extension recently evidenced in the forearc, possibly extending in the backarc, but not s...
Tectonics, 2021
The Lesser Antilles Subduction Zone (hereafter LASZ), at the easternmost boundary of the narrow C... more The Lesser Antilles Subduction Zone (hereafter LASZ), at the easternmost boundary of the narrow Caribbean plate is one of the most arcuate subduction zone at present-day (Figure 1a). The subducting plate of the LASZ consists of both the North and South American plates, hereafter collectively referred to as the American plates, since their relative motion in the study area is negligeable. To the north, the convergence between the American and the Caribbean plates is highly oblique (
Submarine Mass Movements and Their Consequences, 2010
The Algerian continental margin, a Cenozoic passive margin along the plate boundary between Euras... more The Algerian continental margin, a Cenozoic passive margin along the plate boundary between Eurasia and Africa presently reactivated in compression, is one of the most seismically active areas in the Western Mediterranean, having experienced several moderate to strong earthquakes in the coastal zone during the last century. The morphology of the continental slope offshore Algeria is steep and dominated by the presence of numerous canyons of variable size and seafloor escarpments that are probably the seafloor expression of active thrust-folds. Numerous submarine landslides are present along these structures, as well as asso-A. Cattaneo () and N. Sultan Ifremer, GM
Natural Hazards and Earth System Sciences, 2012
Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to poten... more Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to potentially trigger catastrophic sediment collapse and flow. On 21 May 2003, a magnitude 6.8 earthquake located near Boumerdès (central Algerian coast) triggered large turbidity currents responsible for 29 submarine cable breaks at the foot of the continental slope over ∼150 km from west to east. Seafloor bathymetry and backscatter imagery show the potential imprints of the 2003 event and of previous events. Large slope scarps resulting from active deformation may locally enhance sediment instabilities, although faults are not directly visible at the seafloor. Erosion is evident at the foot of the margin and along the paths of the numerous canyons and valleys. Cable breaks are located at the outlets of submarine valleys and in areas of turbiditic levee overspilling and demonstrate the multi-source and multi-path character of the 2003 turbiditic event. Rough estimates of turbidity flow velocity are not straightforward because of the multiple breaks along the same cable, but seem compatible with those measured in other submarine cable break studies elsewhere. While the signature of the turbidity currents is mostly erosional on the continental slope, turbidite beds alternating with hemipelagites accumulate in the distal reaches of sediment dispersal systems. In perspective, more chronological work on distal turbidite successions offshore Algeria offers promising perspectives for paleoseismology reconstructions based on turbidite dating, if synchronous turbidites along independent sedimentary dispersal systems are found to support triggering by major earthquakes. Preliminary results on sediment core PSM-KS23 off Boumerdès typically show a 800-yr interval between turbidites during the Holocene, in accordance with the estimated mean seismic cycle on land, even if at this stage it is not yet possible to prove the earthquake origin of all the turbidites.
Des données de cartographie EM12D e t de géophysique récoltées pendant la campagne GEODYNZ-SUD Le... more Des données de cartographie EM12D e t de géophysique récoltées pendant la campagne GEODYNZ-SUD Leg 1 sur la marge Kermadec-Hikurangi révèlent la tectogénèse associée au passage de la subduction intra-océanique oblique à la subduction sous-continentale très oblique, puis à la transpression intracontinentale. Le partitionnement des composantes décrochante et compressive de la déformation est suggéré dans l'ensemble de la zone étudiée, excepté à son extrémité méridionale. La distribution des structures distensives (au Nord) et compressives (au Sud) est associée à la manifestation probable du processus d'érosion tectonique au Nord e t d'accrétion tectonique au Sud.
The Mediterranean back-arc basins, once opened, are often rapidly submitted to inversion along th... more The Mediterranean back-arc basins, once opened, are often rapidly submitted to inversion along the complex Eurasian-African convergent border. Along their continental margins, these small basins consist of heterogeneous systems that juxtapose lithospheres with different nature, mechanical behavior and structural inheritance. In this study, we focus on the northern Ligurian margin to examine how such complex systems might deform when they are submitted to compressive stress. The northern Ligurian margin, of Oligo-Miocene age, has been undergoing contraction over at least the last 6 Ma. Below the margin, active thrust faults responsible for the regional uplift of the continental edge have been proposed in previous works, but have never been imaged. Seaward of the margin, no recent or active crustal compressional structure has been identified so far in the oceanic domain, although seismicity extends as far as midway through the basin. We use seismic reflection data, including 72- and 12-channel high-resolution acquisitions (MALISAR, 2006 and FABLES, 2012) and 96-channel deep-penetrating ones (MALIS, 1995), to image the Ligurian margin and the adjacent oceanic domain. In the seismic lines, the Messinian event, well dated over the Mediterranean (5.96-5.32 Ma) and well identified in the seismic stratigraphy, allows us to quantify the vertical deformation over the last 5.3 Ma. The seismic reflection data set is interpreted together with 3D-velocity-depth models deduced from wide-angle seismic data (GROSMARIN, 2008). Below the margin, the contraction is characterized by folds, south verging thrusts, tilted crustal blocks, and by a global margin uplift that exceeds 1500m. Within the adjacent oceanic domain, noticeable deformation is restricted to large, SW-NE elongated salt walls located 10 to 40 km from the margin toe, over a 70 km length. We interpret them as resulting from combined deep-seated crustal and thin-skinned deformations. However, although the salt walls are well expressed in the seafloor morphology, their seismic images do not reveal any significant vertical throw across their trace, and the amount of deformation gradually disappears toward the structure ends. This suggests that the post-Messinian deformation taken along these features is moderate, compared to the margin. The synchronicity of the crustal deformation in the oceanic and the continental domains supports the idea that the lower deformation amounts observed within the deep basin are related to different mechanical behaviours within the continental margin and the adjacent oceanic domain, rather than the result of a recent basinward propagation of the deformation. Thermo-mechanical models suggest that mainly two factors could control the focused deformation along the margin: (1) the locus of highest topographic gradient of the main crustal interfaces, (2) the thermal contrast between the subsiding cooling oceanic domain and the uplifting warming margin. According to these models, the continental versus oceanic nature of the lithospheres would be of second order in the localization of the deformation
The Journal of Geology, 1999
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NoDerivatives| 4.0 International License
Marine Geology, 2012
An overview is given of mass wasting features along the slopes of the Sea of Marmara, Turkey, bas... more An overview is given of mass wasting features along the slopes of the Sea of Marmara, Turkey, based on new data and previously published information. The Sea of Marmara is characterized by active tectonics along the North Anatolian Fault and by eustatic sea level changes controlling the connections both to the Mediterranean and Black Sea (i.e. lacustrine and marine conditions during sea-level low and high stands, respectively). High resolution bathymetric data, subsurface echosounder and seismic reflection profiling, seafloor visual observations, as well as stratigraphic analysis of sediment cores have been used to identify, map and date submarine slope failures and mass wasting deposits. Gravity mass movements are widespread on the steep slopes of the Sea of Marmara, and range from small scale slope failures, mainly located within the canyons, to wider unstable areas (20 to 80 km 2). The largest mass wasting features, i.e. the Tuzla, Ganos and Yalova complexes, have been analyzed in connection with crustal deformation. These gravitational gliding masses are probably induced by the transtensional deformation within the crust. Moreover, age determination of landslides and debris flows indicate that they were more frequent during the last transgressive phase, when the rate of terrigenous sediments supplied by the canyons to the deep basin was higher. We discuss these results taking into account activity, pre-conditioning and trigger mechanisms for slope instability with respect to tectonics and paleo-environmental changes induced by sea-level oscillations. Highlights ► We map mass wasting features in the Sea of Marmara. ► Climate change appears as one of the factor triggering slope instability. ► The biggest slides occur in areas of high micro-seismic activity. ► Underlying crustal deformation influence the distribution of slope instability.
Earth and Planetary Science Letters, 1988
Marine geophysical surveys employing Seabeam, multi-and single-channel seismic reflection, gravit... more Marine geophysical surveys employing Seabeam, multi-and single-channel seismic reflection, gravity and magnetic instruments were conducted at two locations along the continental slope of the Peru Trench during the Seaperc cruise of the R/V "Jean Charcot" in July 1986. These areas are centered around 5 "30's arid 9 "30's off the coastal towns of Paita and Chimbote respectively. These data indicate that (1) the continental slope off Peru consists of three distinct morpho-structural domains (from west to &st ate the lower, middle and upper slopes) instead of just two as previously reported: (2) the middle slope has the characteristics of a zone of tectonic collapse at the front of a gently flexured upper slope; (3) the upper half of the lower slope appears to represent the product of mass wasting; (4) thrusting at the foot of the margin produces a continuous morphologic feature representing a deformation front where the products of mass-wasting are overprinted by a compressional tectonic fabric; (5) a change in the tectonic regime from tensional to compressional occurs at the mid-slope-lower slope boundary, the accretionary prism being restricted to the very base af the lower slope in the Paita area. The Andean margin off Peru is an "extensional active margin" or a "collapsing active margin" developing a subordinated accretionary complex induced by massive collapse of the middle slope area. 8 O 30's and 9 O 30's offshore Chimbote (CDP-2). Marine geophysical surveys employing Seabeam, multi-and single-channel seismic reflec-0012-821X/88/$03.50 O 1988 Elsevier Science Publishers B.V. * c CDP-2, respectively. The northern zone is the Paita area (box 2 of the Seaperc cruise) and the southern zqne is the Chimbote area (box 6) (Fig.
Based on an extensive seismic and multibeam dataset, 1-5 km wide giant polygons were identified a... more Based on an extensive seismic and multibeam dataset, 1-5 km wide giant polygons were identified at the bottom of the Grenada basin, covering a total area of ~55000 km². They represent the top ...
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Papers by Bernard Mercier de Lépinay