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Registros recuperados: 21
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Analysis of Holocene sedimentary features on the Adriatic shelf from 3D very high resolution seismic data (Triad survey) ArchiMer
Marsset, Tania; Marsset, Bruno; Thomas, Yannick; Cattaneo, Antonio; Thereau, Estelle; Trincardi, F; Cochonat, Pierre.
Very High Resolution (VHR) 3D seismic data were collected on the Adriatic shelf offshore the city of Ortona in order to define the small-scale geometric complexity of late Holocene deposits. Three groups of units are distinguished from the bottom up: (1) units U1 to U3 forming the Transgressive System Tract (TST); (2) units U4 and U5 representing the condensed interval deposited on the Maximum flooding surface (MFS) and the basal unit of the High stand System Tract (HST); and (3) U6 to U 10 forming the progradational units of the HST. The muddy HST deposits show seafloor and subsurface sedimentary features over up to 40% of its extent on the Adriatic shelf. In the area offshore Ortona, the HST shows shore-parallel undulations in water depth of ca. 30-70 m...
Tipo: Text Palavras-chave: Bottom hugging currents; Sediment deformation; 3D VHR seismic; Adriatic shelf; Late Holocene.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/2004/publication-496.pdf
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Anomalously deep BSR related to a transient state of the gas hydrate system in the western Black Sea ArchiMer
Ker, Stephan; Thomas, Yannick; Riboulot, Vincent; Sultan, Nabil; Bernard, Céline; Scalabrin, Carla; Ion, G; Marsset, Bruno.
A comprehensive characterization of the gas hydrate system offshore the western Black Sea was performed through an integrated analysis of geophysical data. We detected the Bottom Simulating Reflector (BSR), which marks, in this area, the base of gas hydrate stability. The observed BSR depth does not fit the theoretical steady-state base of gas hydrate stability zone (BGHSZ). We show that the disparity between the BSR and predicted BGHSZ is the result of a transient state of the hydrate system due to the ongoing re-equilibrium since the Last Glacial Maximum. When gas hydrates are brought outside the stability zone due to changes in temperature and sea level, their dissociation generates an increase in interstitial pore pressure. This process is favorable to...
Tipo: Text Palavras-chave: Gas hydrate; BSR; Excess pore pressure; Black Sea.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00474/58531/61081.pdf
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Contourite identification along Italian margins: The case of the Portofino drift (Ligurian Sea) ArchiMer
Cattaneo, Antonio; Miramontes, Elda; Samalens, Kevin; Garreau, Pierre; Caillaud, Matthieu; Marsset, Bruno; Corradi, Nicola; Migeon, Sebastien.
A brief review of the published evidence of current deposits around Italy is the occasion to test the robustness of matching bottom current velocity models and seafloor morphologies to identify contourite drifts not yet documented. We present the result of the regional hydrodynamic model MARS3D in the Northern Tyrrhenian and Ligurian Sea with horizontal resolution of 1.2 km and 60 levels with focus on bottom current: data are integrated over summer and winter 2013 as representative of low and high intensity current conditions. The Eastern Ligurian margin is impacted by the Levantine Intermediate Water (LIW) with modeled mean velocity of bottom current up to 20 cm s−1 in winter 2013 and calculated bottom shear stress exceeding 0.2 N m−2 in water depth of...
Tipo: Text Palavras-chave: Sediment drift; Circulation model; Bottom current velocity; Levantine Intermediate Water; Submarine landslide; Mediterranean.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00378/48977/49394.pdf
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Deep-towed High Resolution multichannel seismic imaging ArchiMer
Marsset, Bruno; Menut, Eric; Ker, Stephan; Thomas, Yannick; Regnault, Jean-pierre; Leon, Pierre; Martinossi, Henri; Artzner, Laurent; Chenot, Damien; Dentrecolas, Stephane; Spychalski, B.; Mellier, G.; Sultan, Nabil.
High Resolution (220–1050 Hz) seismic acquisition performed in deep water using deep-towed systems provides unrivalled lateral resolution when compared to conventional surface seismic. The lateral resolution of these acquisitions is controlled by the width of the first Fresnel zone, taking advantage of their positions close to the sea bottom. No current existing deep towed equipment can benefit from seismic imaging processing techniques to improve this resolution as a consequence of positioning inaccuracies. The technological developments of a digital deep-towed multichannel streamer are presented with a particular attention to positioning: each hydrophone incorporates a pitch, roll and heading sensor in order to monitor the constant deformation of the...
Tipo: Text Palavras-chave: Deep-towed seismics; Multichannel streamer; Seismic imaging.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00206/31745/35690.pdf
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Deep-towed high resolution seismic imaging II: Determination of P-wave velocity distribution ArchiMer
Marsset, Bruno; Ker, Stephan; Thomas, Yannick; Colin, Florent.
The acquisition of high resolution seismic data in deep waters requires the development of deep towed seismic sources and receivers able to deal with the high hydrostatic pressure environment. The low frequency piezoelectric transducer of the SYSIF (SYstème Sismique Fond) deep towed seismic device comply with the former requirement taking advantage of the coupling of a mechanical resonance (Janus driver) and a fluid resonance (Helmholtz cavity) to produce a large frequency bandwidth acoustic signal (220–1050 Hz). The ability to perform deep towed multichannel seismic imaging with SYSIF was demonstrated in 2014, yet, the ability to determine P-wave velocity distribution wasn't achieved. P-wave velocity analysis relies on the ratio between the...
Tipo: Text Palavras-chave: Deep-towed seismic; Seismic imaging; P-wave velocity distribution.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00418/52971/53908.pdf
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Développements électroacoustiques en sismique marine Très Haute Résolution ArchiMer
Le Gall, Yves; Marsset, Bruno.
High to Very High Resolution marine seismics are of common use to build and refine models of sediment processes and to explore, for instance, relationships between sediment stratigraphy and sea level variations. The frequency range of this technology lays between 200 and 4000 Hz, providing a vertical resolution of metric to sub-metric scale. Marine experiments with seismic source and receivers towed close to the seafloor are set up in order to limit the energy loss related to wave front divergence and unwanted 3D effects or diffraction hyperbolas deteriorating the quality of the resulting seismic image. The technological challenge was thus to provide users with appropriate seismic acquisition system able to deal with high hydrostatic pressure which forbids...
Tipo: Text
Ano: 2007 URL: http://archimer.ifremer.fr/doc/00127/23830/21754.pdf
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Dynamics of fault-fluid-hydrate system around a shale-cored anticline in deepwater Nigeria ArchiMer
Sultan, Nabil; Riboulot, Vincent; Ker, Stephan; Marsset, Bruno; Geli, Louis; Tary, Jean-baptiste; Klingelhoefer, Frauke; Voisset, Michel; Lanfumey, Valentine; Colliat, Jean-louis; Adamy, Jerome; Grimaud, S..
Gas hydrates were recovered by coring at the eastern border of a shale-cored anticline in the eastern Niger Delta. To characterize the link between faults and fluid release and to identify the role of fluid flow in the gas hydrate dynamics, three piezometers were deployed for periods ranging from 387 to 435 days. Two of them were deployed along a major fault linked to a shallow hydrocarbon reservoir while the third monitored the fluid pressure in a pockmark aligned above the same major fault. In addition, 10 ocean-bottom seismometers (OBS) were deployed for around 60 days. The piezometers simultaneously registered a prolonged fluid flow event lasting 90 days. During this time, OBS measurements record several episodic fluid release events. By combining and...
Tipo: Text
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00060/17106/14624.pdf
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Fine-scale gas distribution in marine sediments assessed from deep-towed seismic data ArchiMer
Ker, Stephan; Le Gonidec, Y.; Marsset, Bruno; Westbrook, Graham; Gibert, D.; Minshull, T. A..
In the context of seismic imaging of gas/gas-hydrate systems, the fine-scale structure of subseabed gas-related reflections is assessed by taking advantage of the source signature of the deep-towed high-resolution SYSIF seismic device. We demonstrate the value of an original wavelet-based method and associated multiscale seismic attributes, applied to seismic data recently acquired on the western margin of the Arctic archipelago of Svalbard. From analysis in the wavelet domain, we recognize two types of gas-related reflections associated with submetre-scale distribution of gas. We identify a thin gas-charged layer associated with an apparent normal polarity reflection, and we detect gas patches associated with a reverse-polarity bright spot with...
Tipo: Text Palavras-chave: Wavelet transform; Gas and hydrate systems; Wave propagation; Acoustic properties; Arctic region.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00175/28602/27019.pdf
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First results of a geophysical survey on the northern flank of the Storegga. slides (Norway). ArchiMer
Nouze, Herve; Contrucci, Isabelle; Foucher, Jean-paul; Marsset, Bruno; Thomas, Yannick; Thereau, Estelle; Normand, Alain; Le Drezen, Eliane; Didailler, Stephane; Regnault, Jean-pierre; Le Conte, Sandie; Guidart, Stéphanie; Lekens, Win; Dean, Simon; Throo, Alexandre.
The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suro (i) over capt aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area.
Tipo: Text Palavras-chave: Slope stability; Fluid escapes; Gas hydrates; Storegga.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/2004/publication-511.pdf
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Freshwater lake to salt-water sea causing widespread hydrate dissociation in the Black Sea ArchiMer
Riboulot, Vincent; Ker, Stephan; Sultan, Nabil; Thomas, Yannick; Marsset, Bruno; Scalabrin, Carla; Ruffine, Livio; Boulart, Cedric; Ion, Gabriel.
Gas hydrates, a solid established by water and gas molecules, are widespread along the continental margins of the world. Their dynamics have mainly been regarded through the lens of temperature-pressure conditions. A fluctuation in one of these parameters may cause destabilization of gas hydrate-bearing sediments below the seafloor with implications in ocean acidification and eventually in global warming. Here we show throughout an example of the Black Sea, the world’s most isolated sea, evidence that extensive gas hydrate dissociation may occur in the future due to recent salinity changes of the sea water. Recent and forthcoming salt diffusion within the sediment will destabilize gas hydrates by reducing the extension and thickness of their thermodynamic...
Tipo: Text
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00418/52981/53916.pdf
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Gas occurrence and shallow conduit systems in the Western Sea of Marmara: a review and new acoustic evidence ArchiMer
Saritas, Hakan; Cifci, Gunay; Geli, Louis; Thomas, Yannick; Marsset, Bruno; Henry, Pierre; Grall, Celine; Rochat, Alexis.
Based on 3D and 2D high-resolution multichannel seismic reflection data in the Western High-Sea of Marmara, this study reviews shallow gas occurrence and related structures and classifies gas conduit systems within the upper, few hundred meter-thick sediment layers below the seafloor. Acoustic anomalies including high amplitude-reverse polarity reflections (bright spots), low amplitude transparent zones, chaotic or discontinuous reflections, pull-down effects, and plumes in the water column are interpreted in terms of natural gas occurrence and fluid flow structures (e.g., mud volcanoes, pockmarks). The gas occurrence is thought to be mostly of thermogenic origin. Mud volcanoes are one of the primary gas conduits forming craters on the seabed due to...
Tipo: Text Palavras-chave: Shallow gas; Gas conduit systems; Mud volcano; Pockmark; 2D-3D seismic; Western High; Sea of Marmara.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00456/56737/58689.pdf
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High-resolution seismic imaging in deep sea from a joint deep-towed/OBH reflection experiment: application to a Mass Transport Complex offshore Nigeria ArchiMer
Ker, Stephan; Marsset, Bruno; Garziglia, Sebastien; Le Gonidec, Y.; Gibert, D.; Voisset, Michel; Adamy, J..
P>We assess the feasibility of high-resolution seismic depth imaging in deep water based on a new geophysical approach involving the joint use of a deep-towed seismic device (SYSIF) and ocean bottom hydrophones (OBHs). Source signature measurement enables signature deconvolution to be used to improve the vertical resolution and signal-to-noise ratio. The source signature was also used to precisely determine direct traveltimes that were inverted to relocate source and receiver positions. The very high accuracy of the positioning that was obtained enabled depth imaging and a stack of the OBH data to be performed. The determination of the P-wave velocity distribution was realized by the adaptation of an iterative focusing approach to the specific...
Tipo: Text Palavras-chave: Controlled source seismology; Seismic tomography; Acoustic properties; Submarine landslides; Atlantic Ocean.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00044/15510/12959.pdf
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Hydrate dissolution as a potential mechanism for pockmark formation in the Niger delta ArchiMer
Sultan, Nabil; Marsset, Bruno; Ker, Stephan; Marsset, Tania; Voisset, Michel; Vernant, Antoine-mathieu; Bayon, Germain; Cauquil, Eric; Adamy, J.; Colliat, J. L.; Drapeau, D..
Based on acquired geophysical, geological and geotechnical data and modeling, we suggest hydrate dissolution to cause sediment collapse and pockmark formation in the Niger delta. Very high-resolution bathymetry data acquired from the Niger delta reveal the morphology of pockmarks with different shapes and sizes going from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression. Geophysical data, in situ piezocone measurements, piezometer measurements and sediment cores demonstrate the presence of a common internal architecture of the studied pockmarks: inner sediments rich in gas hydrates surrounded by overpressured sediments. The temperature, pressure and salinity conditions of the studied area have allowed...
Tipo: Text Palavras-chave: Methane gas hydrate; Sea floor; Marine sediments; Pore pressure; Porous media; Continental margin; Clathrate hydrate; Fluid flow; Stability; Slope.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00012/12300/9092.pdf
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Identification of Shear Zones and Their Causal Mechanisms Using a Combination of Cone Penetration Tests and Seismic Data in the Eastern Niger Delta ArchiMer
Garziglia, Sebastien; Sultan, Nabil; Cattaneo, Antonio; Ker, Stephan; Marsset, Bruno; Riboulot, Vincent; Voisset, Michel; Adamy, J.; Unterseh,.
In a site investigation of the eastern part of the offshore Niger delta, cone penetration tests (CPTU) showed significant drops in tip resistance, associated with decreases in sleeve friction and induced excess pore pressures at the interface between superficial sediments and the underlying deposits of a mass-transport complex (MTC) called NG1. Such signature characteristics of weakened zones are clearly expressed at three sites where the drop in tip resistance reaches more than 40% over 2-3 m-thick intervals. Correlations between CPTU profiles and both 3D and ultrahigh-resolution 2D seismic data suggest that the weakened zones surround syndepositional the within the frontal part of NG1. Hence, weakening appears associated with the remobilization of thrust...
Tipo: Text Palavras-chave: Cone penetration tests; Shear zone; 3D seismic data; Ultrahigh-resolution 2D seismic; Mass-transport complex; Slope stability.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00105/21662/19695.pdf
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Layering and turbulence surrounding an anticyclonic oceanic vortex: in situ observations and quasi-geostrophic numerical simulations ArchiMer
Hua, Bach-lien; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Marsset, Bruno; Aiki, Hidenori.
Evidence of persistent layering, with a vertical stacking of sharp variations in temperature, has been presented recently at the vertical and lateral periphery of energetic oceanic vortices through seismic imaging of the water column. The stacking has vertical scales ranging from a few metres up to 100 m and a lateral spatial coherence of several tens of kilometres comparable with the vortex horizontal size. Inside this layering, in situ data display a [k(h)(-5/3)k(h)(2)] scaling law of horizontal scales for two different quantities, temperature and a proxy for its vertical derivative, but for two different ranges of wavelengths, between 5 and 50 km for temperature and between 500 m and 5 km for its vertical gradient. In this study, we explore the dynamics...
Tipo: Text Palavras-chave: Geostrophic turbulence; Quasi; Geostrophic flows; Stratified flows.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00159/27070/25322.pdf
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Leaking methane reservoirs offshore Svalbard ArchiMer
Minshull, T. A.; Westbrook, Graham; Weitemeyer, K. A.; Sinha, M. C.; Goswami, B. K.; Marsset, Bruno.
Methane hydrate—a solid substance in which methane is trapped within ice‐like crystals—is stable at low temperatures and high pressures and may be destabilized by ocean warming on both geological and human time scales. Methane is a powerful greenhouse gas, and methane released from hydrate provides a potential positive feedback mechanism in global climate change [e.g., Archer and Buffett, 2005]—in theory, the more methane is released by the hydrates, the warmer the climate gets, causing the ocean to warm and release more methane. However, methane escaping from the seabed is oxidized and dissolved in the ocean, and insufficient methane may reach the atmosphere to affect the climate significantly. Its importance for climate change therefore depends on...
Tipo: Text Palavras-chave: Methane hydrate; Svalbard; Sea floor; Seismic; Electromagnetic; Arctic.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00451/56262/57832.pdf
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Multiscale seismic attributes: A wavelet-based method and its application to high-resolution seismic and ground truth data ArchiMer
Ker, Stephan; Le Gonidec, Yves; Gibert, D.; Marsset, Bruno.
We propose a wavelet-based method to characterize acoustic impedance discontinuities from a multiscale analysis of seismic reflected waves. Our approach relies on the analysis of ridge functions which contain most of the information of the wavelet transform in a sparse support. This method falls in the framework of the wavelet response (WR) introduced by Le Gonidec et al. which analyses the impedance multiscale behaviour by propagating dilated wavelets into the medium. We further extend the WR by considering its application to broad-band seismic data. We take into account the bandpass filter effect related to the limited frequency range of the seismic source. We apply the method to a deep-water seismic experiment performed in 2008 during the ERIG3D cruise...
Tipo: Text Palavras-chave: Wavelet transform; Seismic attenuation; Wave propagation; Acoustic properties.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00049/15994/13449.pdf
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Potential role of compressional structures in generating submarine slope failures in the Niger Delta ArchiMer
Sultan, Nabil; Voisset, Michel; Marsset, Bruno; Marsset, Tania; Cauquil, E; Colliat, J.
The study area, offshore Nigeria, is located in one of the compressional zones within the Niger Delta, which is characterized by imbricate thrust structures. Although the low mean slope angle (around 2°), bathymetry data from the study area have shown the existence of several submarine landslides which coincide with known subsurface faulted compressive features. In this paper, we have focused on a submarine slide occurring in water depths ranging between 1690 and 1750 m. Headwall scars, internal architecture and associated deposits have been characterized using a combination of 3D seismic data, near-bottom echosounder seismic profiles, Kullenberg cores and in-situ geotechnical measurements. The slide shows horseshoe shaped headwall scars and depositional...
Tipo: Text Palavras-chave: Slope stability; Piezometer; Penetrometer; Niger Delta; Modelling; Compressional structures.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2408.pdf
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Seismic reflection imaging of shallow oceanographic structures ArchiMer
Piete, Helene; Marie, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-andre.
Multichannel seismic (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow seismic oceanography (SO), we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. Seismic data processing dedicated to SO was also investigated. Conventional seismic acquisition systems were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large...
Tipo: Text Palavras-chave: Seismic oceanography; Seismic acquisition system; Seasonal thermocline; Iroise Sea; Gulf of Cadiz; Florida Straits.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00141/25193/23302.pdf
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Slip rate estimation along the western segment of the Main Marmara Fault over the last 405–490 ka by correlating mass transport deposits ArchiMer
Grall, Celine; Henry, P.; Thomas, Yannick; Westbrook, Graham; Cagatay, M. N.; Marsset, Bruno; Saritas, H.; Cifci, G.; Geli, Louis.
[1] High-resolution 3-D seismic data acquired in the Sea of Marmara on the Western High, along the northwestern branch of the North Anatolian Fault (also known as the Main Marmara Fault), shed new light on the evolution of the deformation over the last 500–600 ka. Sedimentary sequences in ponded basins are correlated with glacioeustatic cycles and transitions between marine and low sea/lake environments in the Sea of Marmara. In the 3 × 11 km2 of the 3-D seismic survey, deformation over the last 405–490 ka is localized along the main fault branch and north of it, where N130°–N140° trending normal faults and N40°–N50° folding accommodated strike-slip deformation associated with active argillokinesis. There is some evidence that deformation was more...
Tipo: Text
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00169/28074/26289.pdf
Registros recuperados: 21
Primeira ... 12 ... Última
 

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