


Registros recuperados: 12  


Ker, Stephan; Le Gonidec, Y.; Marsset, Bruno; Westbrook, Graham; Gibert, D.; Minshull, T. A.. 
In the context of seismic imaging of gas/gashydrate systems, the finescale structure of subseabed gasrelated reflections is assessed by taking advantage of the source signature of the deeptowed highresolution SYSIF seismic device. We demonstrate the value of an original waveletbased 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 gasrelated reflections associated with submetrescale distribution of gas. We identify a thin gascharged layer associated with an apparent normal polarity reflection, and we detect gas patches associated with a reversepolarity bright spot with... 
Tipo: Text 
Palavraschave: Wavelet transform; Gas and hydrate systems; Wave propagation; Acoustic properties; Arctic region. 
Ano: 2014 
URL: http://archimer.ifremer.fr/doc/00175/28602/27019.pdf 
 


Le Gall, Yves; Origne, Laurent; Scalabrin, Carla; Morizur, Yvon. 
Acoustic deterrent devices could be an appealing solution to tackle accidental cetacean bycatches 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 
Palavraschave: 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/acte1124.pdf 
 


Tary, Jeanbaptiste; Geli, Louis; Guennou, Claude; Henry, Pierre; Sultan, Nabil; Cagatay, N.; Vidal, V.. 
Different types of 4component 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). Nonseismic 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 
Palavraschave: 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 
 


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 LonguetHiggins 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 tradeoff between ocean wave coastal reflection and seismic wave attenuation that both affect the amplitude of the... 
Tipo: Text 
Palavraschave: Surface waves and free oscillations; Theoretical seismology; Wave propagation. 
Ano: 2012 
URL: http://archimer.ifremer.fr/doc/00107/21839/19436.pdf 
 

 


Ker, Stephan; Le Gonidec, Y.; Gibert, D.. 
In the context of multiscale seismic analysis of complex reflectors, that takes benefit from broadband frequency range considerations, we perform a waveletbased method to merge multiresolution seismic sources based on generalized Lévyalpha 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 
Palavraschave: Wavelet transform; Wave propagation; Acoustic properties. 
Ano: 2013 
URL: http://archimer.ifremer.fr/doc/00157/26824/24935.pdf 
 


Ker, Stephan; Le Gonidec, Yves; Gibert, D.; Marsset, Bruno. 
We propose a waveletbased 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 broadband 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 deepwater seismic experiment performed in 2008 during the ERIG3D cruise... 
Tipo: Text 
Palavraschave: Wavelet transform; Seismic attenuation; Wave propagation; Acoustic properties. 
Ano: 2011 
URL: http://archimer.ifremer.fr/doc/00049/15994/13449.pdf 
 


Ker, Stephan; Le Gonidec, Yves; Gibert, Dominique. 
A waveletbased method was presented in a previous work to introduce multiscale seismic attributes for highresolution 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 sourcecorrection by considering L´evy alphastable 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 highresolution seismic source, after a classical signature processing, can be taken into account with a GDF. We demonstrate that in the... 
Tipo: Text 
Palavraschave: Wavelet transform; Wave propagation; Acoustic properties. 
Ano: 2012 
URL: http://archimer.ifremer.fr/doc/00090/20155/17828.pdf 
 


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 oceanbottom seismic observations, but oceanbottom seismometer (OBS) temporary deployments are still challenging and face setup 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, timeconsuming 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 
Palavraschave: Seismic instruments; Seismic noise; Wave propagation; Body waves; Statistical methods; Acoustic properties. 
Ano: 2020 
URL: https://archimer.ifremer.fr/doc/00593/70463/68591.pdf 
 


Farra, V.; Stutzmann, Eleonore; Gualtieri, Lucia; Schimmel, M.; Ardhuin, Fabrice. 
Secondary microseism sources are pressure fluctuations close to the ocean surface. They generate acoustic Pwaves 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 Pwaves recorded by receivers in the far field. In the frequency domain, the Pwave 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 Pwaves in the ocean, (3) the propagation from the ocean bottom to the stations, (4) the receiver site effect. Secondary microseism... 
Tipo: Text 
Palavraschave: Seismic interferometry; Body waves; Seismic noise; Wave propagation. 
Ano: 2016 
URL: http://archimer.ifremer.fr/doc/00344/45509/45063.pdf 
 


Monbaliu, J.; PadillaHernandez, 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 WAMcycle4 (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 splitfrequency 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:eurepo/semantics/article 
Palavraschave: Breaking waves; Coastal engineering; Mathematical models; Shallow water; Wave predicting; Wave propagation. 
Ano: 2000 
URL: http://www.vliz.be/nl/openmarienarchief?module=ref&refid=6924 
 


Ioualalen, Mansour; Ratzov, G.; Collot, Jeanyves; 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 
Palavraschave: Tsunamis; Site effects; Wave propagation; Submarine landslides; South America. 
Ano: 2011 
URL: http://archimer.ifremer.fr/doc/00200/31101/29509.pdf 
 
Registros recuperados: 12  


