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Registros recuperados: 5
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3-D sediment-basement tomography of the Northern Marmara trough by a dense OBS network at the nodes of a grid of controlled source profiles along the North Anatolian fault ArchiMer
Bayrakci, Gaye; Laigle, Mireille; Becel, A.; Hirn, A.; Taymaz, T.; Yolsal-cevikbilen, S..
A 3-D tomographic inversion of first arrival times of shot profiles recorded by a dense 2-D OBS network provides an unprecedented constraint on the P-wave velocities heterogeneity of the upper-crustal part of the North Marmara Trough (NMT), over a region of 180 km long by 50 km wide. One of the specific aims of this controlled source tomography is to provide a 3-D initial model for the local earthquake tomography (LET). Hence, in an original way, the controlled source inversion has been performed by using a code dedicated to LET. After several tests to check the results trade-off with the inversion parameters, we build up a 3-D a priori velocity model, in which the sea-bottom topography, the acoustic and the crystalline basements and the Moho interfaces...
Tipo: Text Palavras-chave: Body waves; Seismic tomography; Continental tectonics: strike-slip and transform; Crustal structure..
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00185/29601/28033.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 the ocean site effect on seismic noise body waves ArchiMer
Gualtieri, Lucia; Stutzmann, Eleonore; Farra, V.; Capdeville, Y.; Schimmel, M.; Ardhuin, Fabrice; Morelli, A..
Secondary microseismic noise is generated by non-linear interactions between ocean waves at the ocean surface. We present here the theory for computing the site effect of the ocean layer upon body waves generated by noise sources distributed along the ocean surface. By defining the wavefield as the superposition of plane waves, we show that the ocean site effect can be described as the constructive interference of multiply reflected P waves in the ocean that are then converted to either P or SV waves at the ocean-crust interface. We observe that the site effect varies strongly with period and ocean depth, although in a different way for body waves than for Rayleigh waves. We also show that the ocean site effect is stronger for P waves than for S waves. We...
Tipo: Text Palavras-chave: Body waves; Site effects; Theoretical seismology.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00190/30087/28634.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 Effect of Water-Column Resonance on the Spectra of Secondary Microseism P-waves ArchiMer
Meschede, Matthias; Stutzmann, Eleonore; Farra, Veronique; Schimmel, Martin; Ardhuin, Fabrice.
We compile and analyze a dataset of secondary microseismic P-wave spectra that were observed by North American seismic arrays. Two distinct frequency bands, 0.13–0.15Hz and 0.19–0.21Hz, with enhanced P-wave energy characterize the dataset. Cluster analysis allows to classify the spectra and to associate typical spectral shapes with geographical regions: Low frequency dominated spectra (0.13-0.15Hz) are mostly detected in shallower regions of the North Atlantic and the South Pacific, as well as along the Central and South American Pacific coast. High frequency dominated spectra (0.19-0.21Hz) are mostly detected in deeper regions of the North-Western Pacific and the South Pacific. For a selected subset of high quality sources, we compute synthetic spectra...
Tipo: Text Palavras-chave: Secondary microseisms; Body waves; Noise source spectra; Ocean waves; Site effect.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00404/51517/52109.pdf
Registros recuperados: 5
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