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| Registros recuperados: 13 | |
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| Guillon, Laurent; Lurton, Xavier. |
| Signals received by low-frequency multibeam echosounders are strongly affected by sound penetration inside the upper sediment layers and by backscattering from buried layers down to depths of a few meters; this may lead to serious ambiguities and misinterpretations of experimental data. These phenomena are modeled here using a concept of equivalent input backscattering strength (EIBS), based on a combination of classical models of local backscattering strength and propagation inside fluid layered media. The local backscattering strength at a buried interface is expressed first to account for the impedance adaptation due to the overlying layers, for the angular refraction effects due to the velocity profile, and for the layered structure of the underlying... |
| Tipo: Text |
Palavras-chave: Sound propagation; Sediment structure; Multibeam sonar; Echosounding; Backscatter; Acoustic properties; Sediment properties. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/2001/publication-729.pdf |
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| Dano, Alexandre; Praeg, Daniel; Migeon, Sebastien; Augustin, Jean-marie; Ceramicola, Silvia; Ketzer, Joao Marcelo; Augustin, Adolfo Herbert; Ducassou, Emmanuelle; Mascle, Jean. |
| The central Nile Deep-Sea Fan contains a broad area of seabed destabilisation in association with fluid seepage: slope-parallel sediment undulations are associated with multibeam high-backscatter patches (HBPs) related to authigenic carbonates. During the 2011 APINIL campaign, a deep-towed sidescan and profiling system (SAR) was used to acquire high-resolution data along three transects across water depths of 1,700-2,650 m. Three seabed domains are distinguished, all developed within stratified sediments overlying mass-transport deposits (MTDs). Upslope of the undulations (<1,950 m), sidescan HBPs record focused fluid seepage via seabed cracks. In the western area of undulations, sidescan HBPs are distinct from intermediate-backscatter patches (IBPs)... |
| Tipo: Text |
Palavras-chave: Fluid seepage; Sediment deformation; Backscatter; Gas flares. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00226/33752/37059.pdf |
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| Praeg, Daniel; Ketzer, Joao Marcelo; Augustin, Adolfo Herbert; Migeon, Sebastien; Ceramicola, Silvia; Dano, Alexandre; Ducassou, Emmanuelle; Dupre, Stephanie; Mascle, Jean; Rodrigues, Luiz Frederico. |
| On the central Nile deep-sea fan, stratified sediments overlying mass-transport deposits (MTDs) are deformed into slope-parallel seabed undulations associated with fluid seepage. The western part of this system, in water depths of 1,950–2,250 m, is examined using multi-frequency data from hull-mounted and deep-towed swath/profiling systems. Sub-bottom profiles show sub-vertical fluid pipes that terminate both at and below seabed, and gas signatures along fault planes bounding the undulations. Fluid seepage is recorded by high- to intermediate-backscatter patches (HBPs, IBPs) that differ in appearance on multibeam imagery (30 kHz, ≤3 m penetration) and sidescan swaths (170/190 kHz, <0.1 m penetration). Comparison of the two suggests a distinction of (a)... |
| Tipo: Text |
Palavras-chave: Slope undulations; Fluid seeps; Backscatter; Carbonates; Pipes; Faults. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00158/26956/25251.pdf |
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| Dupre, Stephanie; Buffet, G.; Mascle, J.; Foucher, Jean-paul; Gauger, S.; Boetius, A.; Marfia, Christian. |
| Two highly active mud volcanoes located in 990-1,265 m water depths were mapped on the northern Egyptian continental slope during the BIONIL expedition of R/V Meteor in October 2006. High-resolution swath bathymetry and backscatter imagery were acquired with an autonomous underwater vehicle (AUV)-mounted multibeam echosounder, operating at a frequency of 200 kHz. Data allowed for the construction of similar to 1 m pixel bathymetry and backscatter maps. The newly produced maps provide details of the seabed morphology and texture, and insights into the formation of the two mud volcanoes. They also contain key indicators on the distribution of seepage and its tectonic control. The acquisition of high-resolution seafloor bathymetry and acoustic imagery maps... |
| Tipo: Text |
Palavras-chave: Eastern Mediterranean; Seafloor morphology; Backscatter; Bathymetry; AUV; Nile Deep Sea Fan; Mud volcanoes. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6395.pdf |
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| Dupre, Stéphanie; Woodside, John; Klaucke, Ingo; Mascle, Jean; Foucher, Jean-paul. |
| The Nile deep sea fan system presents a rich variety of fluid escape structures, gas chimneys, pockmarks and carbonate crust mounds, brines pools, and several types of mud volcano. These seep-related structures were explored for the first time with the Nautile submersible during the 2003 Nautinil expedition and are characterized by high thermal gradients and highly gas-saturated sediments. More recently, high resolution side scan sonar data acquired during the 2004 Mimes expedition brings more detail to the geophysical imagery. The EdgeTech DTS-1 deep tow sonar coupled with a 2-8 kHz chirp subbottom penetrator was deployed around 100 m above the seafloor and operated at a frequency of 75 kHz. Several gas plumes were acoustically detected in the water... |
| Tipo: Text |
Palavras-chave: Free gas emission; Backscatter; Authigenic carbonate crust; Mud volcanism; Gas chimneys; Nile Deep Sea Fan. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2005/acte-6396.pdf |
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| Lamarche, Geoffroy; Lurton, Xavier; Verdier, Anne-laure; Augustin, Jean-marie. |
| A comprehensive EM300 multibeam echo-sounder dataset acquired from Cook Strait, New Zealand, is used to develop a regional-scale objective characterisation of the seafloor. Sediment samples and high-resolution seismic data are used for ground-truthing. SonarScope (R) software is used to process the data, including signal corrections from sensor bias, specular reflection compensation and speckle noise filtering aiming at attenuating the effects of recording equipment, seafloor topography, and water column. The processing is completed by correlating a quantitative description (the Generic Seafloor Acoustic Backscatter-GSAB model) with the backscatter data. The calibrated Backscattering Strength (BS) is used to provide information on the physical... |
| Tipo: Text |
Palavras-chave: Backscatter; Multibeam echo-sounder; Sediment waves; Habitat mapping. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14260/11552.pdf |
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| Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand. |
| Multi-year field measurements of sea surface Ka-band dual-co-polarized (vertical transmit–receive polarization (VV) and horizontal transmit–receive polarization (HH)) radar Doppler characteristics from an oceanographic platform in the Black Sea are presented. The Doppler centroid (DC) estimated using the first moment of 5 min averaged spectrum, corrected for measured sea surface current, ranges between 0 and ≈1 m/s for incidence angles increasing from 0 to 70∘ . Besides the known wind-to-radar azimuth dependence, the DC can also depend on wind-to-dominant wave direction. For co-aligned wind and waves, a negative crosswind DC residual is found, ≈−0.1 m/s, at ≈20 ∘ incidence angle, becoming negligible at ≈ 60 ∘ , and raising to, ≈+0.5 m/s, at 70∘ . For our... |
| Tipo: Text |
Palavras-chave: Radar; Scatterometer; Ocean; Backscatter; Doppler shift; Doppler centroid; Sea surface current; Wind drift; Modulation; Transfer function; Empirical model. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00489/60077/63399.pdf |
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| Schulien, Jennifer A.; Della Penna, Alice; Gaube, Peter; Chase, Alison P.; Haëntjens, Nils; Graff, Jason R.; Hair, Johnathan W.; Hostetler, Chris A.; Scarino, Amy Jo; Boss, Emmanuel S.; Karp-boss, Lee; Behrenfeld, Michael J.. |
| Changes in airborne high spectral resolution lidar (HSRL) measurements of scattering, depolarization, and attenuation coincided with a shift in phytoplankton community composition across an anticyclonic eddy in the North Atlantic. We normalized the total depolarization ratio (δ) by the particulate backscattering coefficient (bbp) to account for the covariance in δ and bbp that has been attributed to multiple scattering. A 15% increase in δ/bbp inside the eddy coincided with decreased phytoplankton biomass and a shift to smaller and more elongated phytoplankton cells. Taxonomic changes (reduced dinoflagellate relative abundance inside the eddy) were also observed. The δ signal is thus potentially most sensitive to changes in phytoplankton shape because... |
| Tipo: Text |
Palavras-chave: HSRL; Depolarization; Backscatter; Phytoplankton community composition; Eddy. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00641/75313/75809.pdf |
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| Sen, Arunima; Ondreas, Helene; Gaillot, Arnaud; Marcon, Yann; Augustin, Jean-marie; Olu, Karine. |
| Deep-sea ecosystems have attracted considerable commercial interest in recent years because of their potential to sustain a diverse range of mankind's industrial needs. If these systems are to be preserved or exploited in a sustainable manner, mapping habitats and species distributions is critical. As biodiversity at cold-seeps or other deep-sea ecosystems is driven by habitat heterogeneity, imagery is the obvious choice for characterizing these systems and has indeed proven extremely valuable towards mapping biogenic habitats formed by dense aggregations of large sized species, such as coral reefs, tubeworm bushes or bivalve beds. However, the acquisition of detailed images with resolution sufficient for reliable identification is extremely time... |
| Tipo: Text |
Palavras-chave: Mapping; Cold seeps; Multibeam; Bathymetry; Backscatter; Biogenic habitats. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00312/42286/41612.pdf |
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| Registros recuperados: 13 | |
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