Contents
Academic literature on the topic 'Imagerie sismique passive'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Imagerie sismique passive.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Dissertations / Theses on the topic "Imagerie sismique passive"
Poli, Piero. "Utilisation du bruit sismique pour l'imagerie de la croûte, du manteau et du noyau terrestre." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENU046.
Full textAmbient seismic noise correlation technique is today widely applied in seismology. The attractive aspect of this method relies in the possibility of obtaining an estimated Green's function everywhere in the world, also in absence of explosions or earthquakes. As surface waves dominate the estimated Green's fucntion, they can be used for high-resolution imaging of the shallow Earth. Similar observation of body waves would provide the required resolution to solve the deeper Earth structures.In the first part of our work we focus on resolving the crustal structure of northern Finland. Using surface waves reconstructed from noise correlation, we reconstructed a threedimensional S waves model that gives acces to the ancient structures of the crust.In the second part we analyse how body waves can emerge from seismic noise correlation. We show that body waves travelling from regional to teleseismic distances are well reconstructed from noise correlation. As these waves contain information about the Earth structure they represent a new and original dataset to improve the knowledge of our planet
Rivet, Diane. "Suivi temporel de la zone de subduction d'Amérique Centrale et imagerie de la vallée de Mexico." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00721987.
Full textTouma, Rita. "Approche matricielle de l’imagerie sismique passive par ondes de volume." Thesis, Université Grenoble Alpes, 2022. http://www.theses.fr/2022GRALU011.
Full textRevealing the structure of fault zones provides insights required to assess seismic hazards. Reflection imaging methods, in particular migration, are commonly used to image the subsurface. An accurate velocity model is often needed to properly locate the reflectors in depth.Imaging fault zones is challenging due to the complex distribution of velocity. Also, most reflection techniques image fault zones indirectly from the discontinuity of geological layers. Wave diffraction by small-scale heterogeneities, such as cracks and fractures is generally neglected.In this thesis, we propose a matrix imaging approach for geophysical exploration that handles the velocity variation in the crust and allows to resolve heterogeneities of the order of the wavelength throughout the fault zone.The reflection matrix approach is inspired from previous studies in ultrasound and optical imaging of complex media. First, ambient noise cross-correlations are used to retrieve the reflection matrix associated with a dense array of geophones. The body wave components of this matrix contains all the information available on the medium. Second, the presented approach does not require a detailed velocity model of the subsurface. A set of matrix operation is applied to compensate for the mismatch between the actual wave velocity model and its approximate model.In a first application, we use ambient noise records in the frequency band [10 20] Hz from a dense array in order image the San Jacinto Fault, California, at small scale with an horizontal resolution of 80 m. ZZ cross-correlations are computed and arranged as 2D matrix. By applying time delays, the response matrix is projected to depth, using a homogeneous velocity model. A focused reflection matrix is obtained, that contains the impulse response between virtual sources and receivers at depth. From this matrix, the image of the medium is built and the resolution of the image can be quantified.Variations between the considered model and the reality result in phase distortions, i.e aberrations, that have detrimental effects on the image of the medium.We develop an aberration correction process that allows to compensate for these distortions by introducing a novel operator, the distortion matrix. 3D images of the first 4 km of the crust are retrieved. These images reveal the backscattered intensity generated by the heterogeneities in the medium. The location and reflectivity of scatterers are retrieved with a resolution 8 times better than the one in free space. Differences in the scattering between the Northwest and the Southeast of the fault were reported with an intense localized damage zone in the Southeast.In a second application, we image the large scale structure of North Anatolian Fault using [0.1 0.5] Hz horizontal cross-correlations computed between 73 pairs of stations. A multi-layered velocity model is considered. A local correction of the phase distortions is performed. The scattering structure of the crust and the upper mantle is revealed. Differences in the Moho depth are reported, with a step below the northern branch. Strong scattering is observed in the region lying along the northern strand of the fault, coinciding with the limit of the lithospheric blocks. The scattering in the North extends to 60 km depth, suggesting a shear zone that penetrates in the upper mantle beneath the northern strand. The scattering also reveals the deep structure of the main geological blocks.In the last part of this thesis, we propose an approach that paves the route towards a 3D passive tomography of the body wave velocity. Finally, all the presented applications confirm the efficiency of the reflection matrix approach in revealing the structure of the subsurface. It provides new insights into the scattering distribution in the Earth. It can be applied to any scale, scattering regime, and frequency bandwith, if the spatial sampling of the geophones' array satisfies the Nyquist criterion
Kazantsev, Alexandre. "Perturbations d'amplitude du bruit ambiant au droit des hétérogéneités : étude de faisabilité pour l'exploration et la surveillance de réservoirs multi-fluide." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM075/document.
Full textThis PhD work investigates the possible elastic mechanisms behind the ambient noise amplification above multi-phase fluid reservoirs. Three datasets are analysed above different reservoirs. The observed spectral signature is different in the gas storage and geothermal contexts. A non-supervised algorithm for amplitude spectrum classification is developed, allowing to extract and map the relevant attributes of a multi-phase fluid presence. As a first modelling step, a wavefield characterisation methodology is applied to determine the composition of the ambient noise. It reveals the presence of strong Rayleigh overtones. Numerical 2D elastic modelling is used to simulate the propagation of overtones across a reservoir within a realistic geological structure. The modelled reservoir response is too small compared to the real data. However, the small amplitude perturbations arising in the numerical simulations are successfully inverted for the position of the reservoir, in simple background models. The developed method could in theory be used for imaging small time-lapse amplitude variations (monitoring), despite the obstacles remaining to be overcome before a real-data application. Neither visco-elastic nor 3D effects are adressed. Thus this work does not exclude the possibility of strong reservoir-specific spectral anomalies
Giraudat, Elsa. "Imagerie matricielle spatio-temporelle : de la sismologie passive des volcans à l'échographie transcrânienne du cerveau." Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLS008.
Full textWave imaging aims at characterizing an unknown environment by actively probing it and then recording the waves reflected by the medium. This is the principle behind ultrasound imaging or reflection seismology, for example. Conventional imaging methods are based on two fundamental assumptions: homogeneity of wave velocity in the medium and a simple scattering regime. In reality, these assumptions can rarely be verified, be it for in vivo medical ultrasound or in situ seismic exporation. Spatial variations in phase velocity distort the wavefronts and can cause multiple scattering events or reverberation, which significantly affect the focusing process and thus image resolution and contrast. To overcome these fundamental limitations, the matrix imaging approach has recently been developed in various domains of wave physics. In this approach, the reflection matrix associated with a sensor array facing the medium is measured. Once this matrix is known, a series of operations can be applied to it to learn how to virtually focus on any point in the medium and thus estimate a reliable reflectity map.First, the matrix formalism is leveraged to image the internal structure of the volcano La Soufrière de Guadeloupe. Correlations of seismic noise recorded by a geophone network are used to access the response matrix of the medium. Using a broadband redatuming process, the matrix is then projected into a virtual geophone basis at each depth. By isolating wavefront distortions in a distortion matrix and analyzing them from the Earth’s surface basis, we can exploit an angular memory effect to compensate for heterogeneities in seismic wave velocity and reveal the volcanic vent over the first five kilometers. By correcting these wavefront distortions from the plane wave basis, we then obtain an image of the magma storage system down to a depth of 10 kilometers, with a resolution on the order of half a wavelength. Such a resolution goes far beyond the diffraction limit, which is usually determined by the finite size of the geophone array.Secondly, the matrix approach is exploited to address reverberation compensation in transcranial ultrasound imaging. For this purpose, the focused reflection matrix is no longer considered only at the ballistic time, but its investigation is extended to the time domain. The concept of distortion matrix is extended to the frequency domain and spatio-temporal focusing laws are estimated to compensate for reverberation through the human skull. However, this method relies on a local memory effect, which may not be sufficient for a medium as complex as the skull.To circumvent this problem, we can take advantage of the dynamic nature of the cerebrovascular system to propose a method for extracting aberration laws that does not rely on the assumption of local isoplanetism. Preliminary results are shown using an in vivo transcranial imaging experiment on a sheep. This approach paves the way for a high-resolution measurement of the transmission matrix connecting each probe transducer fo each image voxel. Access to this matrix is the Holy Grail for imaging, since its inversion would allow us to make any skull bone transparent
Kazantsev, Alexandre. "Perturbations d'amplitude du bruit ambiant au droit des hétérogéneités : étude de faisabilité pour l'exploration et la surveillance de réservoirs multi-fluide." Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM075.
Full textThis PhD work investigates the possible elastic mechanisms behind the ambient noise amplification above multi-phase fluid reservoirs. Three datasets are analysed above different reservoirs. The observed spectral signature is different in the gas storage and geothermal contexts. A non-supervised algorithm for amplitude spectrum classification is developed, allowing to extract and map the relevant attributes of a multi-phase fluid presence. As a first modelling step, a wavefield characterisation methodology is applied to determine the composition of the ambient noise. It reveals the presence of strong Rayleigh overtones. Numerical 2D elastic modelling is used to simulate the propagation of overtones across a reservoir within a realistic geological structure. The modelled reservoir response is too small compared to the real data. However, the small amplitude perturbations arising in the numerical simulations are successfully inverted for the position of the reservoir, in simple background models. The developed method could in theory be used for imaging small time-lapse amplitude variations (monitoring), despite the obstacles remaining to be overcome before a real-data application. Neither visco-elastic nor 3D effects are adressed. Thus this work does not exclude the possibility of strong reservoir-specific spectral anomalies
Larose, Eric. "Diffusion multiple des ondes sismiques et expériences analogiques en ultrasons." Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10100.
Full textThis thesis manuscript is devoted to the study of the seismic and ultrasonic wave propagation in complex media. Two methods are proposed to take advantage of the phase information contained in diffuse waves. 1) Weak localization of seismic waves is observed on a volcano (Auvergne). This field experiment demonstrates the presence of multiple scattering in coda waves, and allows the direct measurement of the transport mean free path of the sub-surface that quantifies the heterogeneities. 2) A passive imaging technique is also proposed : it is based on the correlation of diffuse field or noise, a correlation that yield the elastic or acoustic Green function between passive sensors as if one of them was a source. Initially applied to ultrasonic cavities, this technique is generalized to open scattering media. A physical interpretation based on a Time-Reversal analogyis proposed. The time symmetry of the correlations is studied, with means of numerical simulations, seismic experiment in Alaska, and ultrasonic experiment in the lab using a small medium ana logo us to the Earth's crust. The role of scattering and source position is emphasized. The passive imaging technique is used to perform the tomography of a layered medium, to image of interfaces and localized reflectors. Ln the end this technique is applied to Lunar seismic noise records, acquiered by four geophones emplaced on the Moon during Apollo 17 mission (1972). This last observation demonstrates the feasibility of correlating the noise to image the subsurface on other planets than the Earth which should provide a novel avenue for future extraterrestrial exploration missions
LAROSE, Eric. "Diffusion multiple des ondes sismiques et expériences analogiques en ultrasons." Phd thesis, 2005. http://tel.archives-ouvertes.fr/tel-00010020.
Full textGouedard, Pierre. "Techniques de corrélation : aspects méthodologiques et applications à la sub-surface." Phd thesis, 2008. http://tel.archives-ouvertes.fr/tel-00357045.
Full textCe travail est centré sur les petites échelles de la géophysique (10 m à 1 km) et aux hautes fréquences (5 à 50 Hz), où les propriétés du champ d'onde mettent souvent en défaut l'hypothèse de champ diffus du théoréme de corrélation. A partir de cas expérimentaux où la fonction de corrélation ne converge pas vers la fonction de Green, de nouvelles approches sont définies afin de retrouver malgré tout les propriétés du milieu.
L'importance de la distribution des sources de bruit pour les milieux non diffusant est mise en évidence. La caractérisation du champ d'onde est ainsi essentielle avant la mise en place de méthodes passives. Une étude comparative des méthodes l'imagerie active et passive est proposée. Elle montre que la résolution de l'imagerie passive est au moins aussi bonne que celle de l'imagerie active.
Enfin, une approche méthodologique est proposée pour l'étude du bruit ambiant, à partir d'outils issus de l'acoustique sous marine. Son application à l'étude de zones hydrothermales est discutée.