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Asymptotic viscoacoustic diffraction tomography of ultrasonic laboratory data: a tool for rock properties analysis ArchiMer
Ribodetti, A; Operto, S; Virieux, J; Lambare, G; Valero, Hp; Gibert, D.
This paper presents an application of 2.5-D asymptotic viscoacoustic diffraction tomography to ultrasonic data recorded during a physically scaled laboratory experiment. This scaled experiment was used to test the reliability of our method when applied to a real data set to estimate the attenuation factor Q. Diffraction tomography relies on ray theory to compute the Green functions in a smooth background medium and on the Born approximation to linearize the relation between the scattered wavefield and the velocity and Q perturbations. The perturbations are inferred from the data by an iterative (linear) quasi-Newtonian algorithm. The inversion formula was specifically developed to account for the acquisition geometry designed in this study. The derivation...
Tipo: Text Palavras-chave: Asymptotic method; Attenuation; Diffraction tomography; Rock properties; Ultrasonic seismic data.
Ano: 2000 URL: https://archimer.ifremer.fr/doc/00466/57770/60029.pdf
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Deep structure of the northern Kerguelen Plateau and hotspot-related activity ArchiMer
Charvis, P; Recq, M; Operto, S; Brefort, D.
Seismic refraction profiles were carried out in 1983 and 1987 throughout the Kerguelen Isles (southern Indian Ocean, Terres Australes and Antarctiques Francaises, TAAF) and thereafter at sea on the Kerguelen-Heard Plateau during the MD66/KeOBS cruise in 1991. These profiles substantiate the existence of oceanic-type crust beneath the Kerguelen-Heard Plateau stretching from 46 degrees S to 55 degrees S, including the archipelago. Seismic velocities within both structures are in the range of those encountered in 'standard' oceanic crust. However, the Kerguelen Isles and the Kerguelen-Heard Plateau differ strikingly in their velocity-depth structure. Unlike the Kerguelen Isles, the thickening of the crust below the Kerguelen-Heard Plateau is caused by a 17 km...
Tipo: Text Palavras-chave: Hotspot; Kerguelen; Lower crust; Oceanic islands; Oceanic plateau; Underplating.
Ano: 1995 URL: https://archimer.ifremer.fr/doc/00297/40791/39809.pdf
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Small-scale crustal variability within an intraplate structure: the Crozet Bank (southern Indian Ocean) ArchiMer
Recq, M; Goslin, J; Charvis, P; Operto, S.
The Crozet Bank, the easternmost region of the Crozet Plateau (austral Indian Ocean), is capped by two groups of islands which form the Crozet Archipelago (Terres Australes and Antarctiques Francaises). A N-S-trending 2 km deep basin, the Indivat Basin, extends between the two groups of islands and bisects the Crozet Bank into two separate domains. The interpretation of the KeOBS8 seismic refraction profile shot during the KeOBS/MD66 cruise (January-February 1991) over the eastern Crozet Plateau was carried out by ray tracing and the computation of synthetic seismograms. This interpretation leads to a rather complex seismic structure and outlines a pronounced eastward crustal thinning from 16.5 to 10 km at the expense of layer 2. The thinning of the crust...
Tipo: Text Palavras-chave: Aseismic ridge; Crozet Islands platform; Crustal structure; Gravity anomalies; Hotspots; Seismic refraction.
Ano: 1998 URL: https://archimer.ifremer.fr/doc/00297/40789/39805.pdf
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Structure and development of a microcontinent: Elan Bank in the southern Indian Ocean ArchiMer
Borissova, I; Coffin, Mf; Charvis, P; Operto, S.
Microcontinents appear to commonly form on young continental margins close to hot spots, but difficulties in understanding their geology and evolution have inhibited assessment of their global distribution and significance. Thick volcanic accumulations in areas affected by hot spot magmatism only complicate the issue. Elan Bank, a large western salient of the Kerguelen Plateau, is a microcontinent that originally lay between India and Antarctica in Gondwana. Recent regional plate tectonic reconstructions suggest that during Gondwana breakup, Elan Bank and India initially separated from Antarctica, and Elan Bank became isolated in the Southern Ocean via a ridge jump to the north between Elan Bank and India. In Albian time (similar to 108 Ma), voluminous...
Tipo: Text Palavras-chave: Elan Bank; Marine seismics; Oceanic structures.
Ano: 2003 URL: https://archimer.ifremer.fr/doc/00225/33665/32079.pdf
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