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Registros recuperados: 12
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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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Le répulsif à cétacés : performances acoustiques requises ArchiMer
Le Gall, Yves; Origne, Laurent; Scalabrin, Carla; Morizur, Yvon.
Acoustic deterrent devices could be an appealing solution to tackle accidental cetacean by-catches in pelagic trawls or in fishing net gears. The bibliographical data on two species (Harbour porpoise and bottlenosed dolphin) have been analyzed in terms of audiogram, discomfort noise level that could lead to behavioural changes, sensory fatigue, and threshold for permanent hearing injuries. It is possible, on the basis of the above data, to characterize an efficient annoyance sound threshold which is not harmful to the species to be protected. Taking into account the properties of the sound waves propagation in the marine environment and according to the required range, the minimal amplitude of the repulsive sound to emit is proposed. Accordingly, the...
Tipo: Text Palavras-chave: Wave propagation; Behaviour; Audiogram; Capture; Cetacean; In fishing net gear; Pelagic trawl; Acoustic deterrent; Propagation onde; Comportement; Audiogramme; Capture; Cétacé; Filet; Pêche artisanale; Chalutage pélagique; Répulsif acoustique.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/2004/acte-1124.pdf
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Microevents produced by gas migration and expulsion at the seabed: a study based on sea bottom recordings from the Sea of Marmara ArchiMer
Tary, Jean-baptiste; Geli, Louis; Guennou, Claude; Henry, Pierre; Sultan, Nabil; Cagatay, N.; Vidal, V..
Different types of 4-component ocean bottom seismometers (OBS) were deployed for variable durations ranging from 1 week to about 4 months in 2007, over soft sediments covering the seafloor of the Tekirdag Basin (western part of the Sea of Marmara, Turkey). Non-seismic microevents were recorded by the geophones, but generally not by the hydrophones, except when the hydrophone is located less than a few tens of centimetres above the seafloor. The microevents are characterized by short durations of less than 0.8 s, by frequencies ranging between 4 and 30 Hz, and by highly variable amplitudes. In addition, no correlation between OBSs was observed, except for two OBSs, located 10 m apart. Interestingly, a swarm of similar to 400 very similar microevents (based...
Tipo: Text Palavras-chave: Time series analysis; Gas and hydrate systems; Body waves; Interface waves; Seismic attenuation; Wave propagation.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00089/20012/17825.pdf
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Modelling long-term seismic noise in various environments ArchiMer
Stutzmann, E.; Ardhuin, Fabrice; Schimmel, M.; Mangeney, A.; Patau, G..
The strongest seismic noise, called secondary microseisms, is generated by ocean wave interactions and we model this noise using the theory of Longuet-Higgins generalized to random ocean gravity waves. Noise sources are computed with an ocean wave model that takes into account coastal reflections. Variations of the source locations are consistent with seasonal variations of seismic noise spectra. Noise spectra are modelled over many years for stations representative of various environments such as continent, island and polar area to constrain, for each environment, the parameters involved in the modelling. For each station, we quantify the trade-off between ocean wave coastal reflection and seismic wave attenuation that both affect the amplitude of the...
Tipo: Text Palavras-chave: Surface waves and free oscillations; Theoretical seismology; Wave propagation.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00107/21839/19436.pdf
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Modelling secondary microseismic noise by normal mode summation ArchiMer
Gualtieri, L.; Stutzmann, E.; Capdeville, Y.; Ardhuin, Fabrice; Schimmel, M.; Mangeney, A.; Morelli, A..
Secondary microseisms recorded by seismic stations are generated in the ocean by the interaction of ocean gravity waves. We present here the theory for modelling secondary microseismic noise by normal mode summation. We show that the noise sources can be modelled by vertical forces and how to derive them from a realistic ocean wave model. We then show how to compute bathymetry excitation effect in a realistic earth model by using normal modes and a comparison with Longuet-Higgins approach. The strongest excitation areas in the oceans depends on the bathymetry and period and are different for each seismic mode. Seismic noise is then modelled by normal mode summation considering varying bathymetry. We derive an attenuation model that enables to fit well the...
Tipo: Text Palavras-chave: Surface waves and free oscillations; Seismic attenuation; Theoretical seismology; Wave propagation.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00146/25703/24020.pdf
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Multiresolution seismic data fusion with a generalized wavelet-based method to derive subseabed acoustic properties ArchiMer
Ker, Stephan; Le Gonidec, Y.; Gibert, D..
In the context of multiscale seismic analysis of complex reflectors, that takes benefit from broad-band frequency range considerations, we perform a wavelet-based method to merge multiresolution seismic sources based on generalized Lévy-alpha stable functions. The frequency bandwidth limitation of individual seismic sources induces distortions in wavelet responses (WRs), and we show that Gaussian fractional derivative functions are optimal wavelets to fully correct for these distortions in the merged frequency range. The efficiency of the method is also based on a new wavelet parametrization, that is the breadth of the wavelet, where the dominant dilation is adapted to the wavelet formalism. As a first demonstration to merge multiresolution seismic...
Tipo: Text Palavras-chave: Wavelet transform; Wave propagation; Acoustic properties.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00157/26824/24935.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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Multiscale seismic attributes: source-corrected wavelet response and application to high-resolution seismic data ArchiMer
Ker, Stephan; Le Gonidec, Yves; Gibert, Dominique.
A wavelet-based method was presented in a previous work to introduce multiscale seismic attributes for high-resolution seismic data. Because of the limited frequency bandwidth of the seismic source, we observed distortions in the seismic attributes based on the wavelet response of the subsurface discontinuities (Le Gonidec et al.). In this paper, we go further in the seismic source-correction by considering L´evy alpha-stable distributions introduced in the formalism of the continuous wavelet transform (CWT). The wavelets are Gaussian derivative functions (GDF), characterized by a derivative order. We show that a high-resolution seismic source, after a classical signature processing, can be taken into account with a GDF. We demonstrate that in the...
Tipo: Text Palavras-chave: Wavelet transform; Wave propagation; Acoustic properties.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00090/20155/17828.pdf
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Orienting and locating ocean-bottom seismometers from ship noise analysis ArchiMer
Trabattoni, A; Barruol, G; Dreo, R; Boudraa, A O; Fontaine, F R.
Breakthroughs in understanding the structure and dynamics of our planet will strongly depend upon instrumenting deep oceans. Progress has been made these last decades in ocean-bottom seismic observations, but ocean-bottom seismometer (OBS) temporary deployments are still challenging and face set-up limitations. Launched from oceanographic vessels, OBSs fall freely and may slightly drift laterally, dragged by currents. Therefore, their actual orientation and location on the landing sites are hard to assess precisely. Numerous techniques have been developed to retrieve this key information, but most of them are costly, time-consuming or inaccurate. In this work, we show how ship noise can be used as an acoustic source of opportunity to retrieve both the...
Tipo: Text Palavras-chave: Seismic instruments; Seismic noise; Wave propagation; Body waves; Statistical methods; Acoustic properties.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00593/70463/68591.pdf
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Ray-theoretical modeling of secondary microseism P-waves ArchiMer
Farra, V.; Stutzmann, Eleonore; Gualtieri, Lucia; Schimmel, M.; Ardhuin, Fabrice.
Secondary microseism sources are pressure fluctuations close to the ocean surface. They generate acoustic P-waves that propagate in water down to the ocean bottom where they are partly reflected, and partly transmitted into the crust to continue their propagation through the Earth. We present the theory for computing the displacement power spectral density of secondary microseism P-waves recorded by receivers in the far field. In the frequency domain, the P-wave displacement can be modeled as the product of (1) the pressure source, (2) the source site effect that accounts for the constructive interference of multiply reflected P-waves in the ocean, (3) the propagation from the ocean bottom to the stations, (4) the receiver site effect. Secondary microseism...
Tipo: Text Palavras-chave: Seismic interferometry; Body waves; Seismic noise; Wave propagation.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00344/45509/45063.pdf
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The spectral wave model, WAM, adapted for applications with high spatial resolution OMA
Monbaliu, J.; Padilla-Hernandez, R.; Hargreaves, J.C.; Carretero Albiach, J.C.; Luo, W.; Sclavo, M.; Günther, H..
New features have been added and several necessary changes have been made to the standard WAM-cycle4 (WAMC4) model code for it to run efficiently when applied to shallow water regions. The restriction of having a source term integration time step smaller than or equal to the propagation time step was relaxed, considerably reducing the computational time needed. An additional reduction in computing time and an increase in accuracy were obtained by introducing a split-frequency time step. There is now a choice of using the octant or quadrant coordinate system for the propagation of the wave energy. The source term integration and, more particularly, the use of a limiter on the energy growth, were studied. For the evaluation of the energy decay in shallow...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Breaking waves; Coastal engineering; Mathematical models; Shallow water; Wave predicting; Wave propagation.
Ano: 2000 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6924
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The tsunami signature on a submerged promontory: the case study of the Atacames Promontory, Ecuador ArchiMer
Ioualalen, Mansour; Ratzov, G.; Collot, Jean-yves; Sanclemente, E..
P>Shelf promontories exhibit very specific bathymetric features with regards to tsunamis. Because of their submerged cape morphology, a potential tsunami generated seawards of the promontory will exhibit a specific mode of propagation and coastal impact. To identify this peculiar tsunami signature, the Atacames Promontory, Ecuador, was chosen as a case study (another example is the shelf of the Nile delta, Egypt). The area is tectonically very active, hosts earthquakes among the most powerful recorded, as well as areas of slope instabilities that have triggered significant submarine landslides in the past (several cubic kilometres of volume). Both types of events are likely to be tsunamigenic. To examine the tsunami behaviour at the coastal area of the...
Tipo: Text Palavras-chave: Tsunamis; Site effects; Wave propagation; Submarine landslides; South America.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00200/31101/29509.pdf
Registros recuperados: 12
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