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| Maurya, S.; Montagner, J-p; Kumar, M. Ravi; Stutzmann, E.; Kiselev, S.; Burgos, G.; Rao, N. Purnachandra; Srinagesh, D.. |
| We present a high-resolution 3-D lithospheric model of the Indian plate region down to 300 km depth, obtained by inverting a new massive database of surface wave observations, using classical tomographic methods. Data are collected from more than 550 seismic broadband stations spanning the Indian subcontinent and surrounding regions. The Rayleigh wave dispersion measurements along similar to 14,000 paths are made in a broad frequency range (16-250 s). Our regionalized surface wave (group and phase) dispersion data are inverted at depth in two steps: first an isotropic inversion and next an anisotropic inversion of the phase velocity including the SV wave velocity and azimuthal anisotropy, based on the perturbation theory. We are able to recover most of the... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00600/71183/69536.pdf |
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| Ardhuin, Fabrice; Balanche, Abel; Stutzmann, E.; Obrebski, Mathias. |
| Seismic noise is an indirect source of information on ocean waves. Using a model of noise generation and propagation, seismic stations can be separated into those that are mostly sensitive to local sea states, and those that integrate sources from a large oceanic area. The model also provides a classification of noise-generating sea states into three classes. The analysis of Central California seismic noise data, well correlated with local waves, reveals that class I events dominate in summer, caused by a single wind-sea system, and for which ocean wave spectral levels are proportional to seismic spectral levels to an exponent b similar or equal to 0.9. In winter, noise is dominated by class II generation, for which coastal reflection is important, with a... |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00083/19443/17051.pdf |
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| Obrebski, Mathias; Ardhuin, Fabrice; Stutzmann, E.; Schimmel, M.. |
| The location of oceanic sources of the micrometric ground displacement recorded at land stations in the 0.1-0.3 Hz frequency band ("double frequency microseisms") is still poorly known. Here we use one particularly strong noise event in the Pacific to show that small swells from two distant storms can be a strong deep-water source of seismic noise, dominating temporarily the signals recorded at coastal seismic stations. Our interpretation is based on the analysis of noise polarization recorded all around the source, and the good fit achieved for this event and year-round between observed and modeled seismic data. The model further suggests that this is a typical source of these infrequent loud noise bursts, which supports previous inconclusive evidences of... |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00085/19625/17262.pdf |
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| Schimmel, M.; Stutzmann, E.; Ardhuin, Fabrice; Gallart, J.. |
| We quantify, analyze, and characterize the frequency-dependent microseismic noise recorded by worldwide distributed seismic stations. Microseismic noise is generated through the interaction of ocean waves. It is the strongest ambient noise, and it is observed everywhere on Earth. We introduce a new approach which permits us to detect polarized signals in the time-frequency domain and which we use to characterize the microseismic noise. We analyze 7 years of continuous seismograms from the global GEOSCOPE network. Microseisms are dominated by Rayleigh waves, and we therefore focus on elliptically polarized signals. The polarized signals are detected in the time-frequency domain through a degree of polarization measure. We design polarization spectra and... |
| Tipo: Text |
Palavras-chave: Microseismic noise; Polarization; Primary and secondary microseisms; Seismology. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00041/15219/12713.pdf |
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| 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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| Davy, C.; Stutzmann, E.; Barruol, G.; Fontaine, F. R.; Schimmel, M.. |
| Ocean waves activity is a major source of microvibrations that travel through the solid Earth, known as microseismic noise and recorded worldwide by broadband seismometers. Analysis of microseismic noise in continuous seismic records can be used to investigate noise sources in the oceans such as storms, and their variations in space and time, making possible the regional and global-scale monitoring of the wave climate. In order to complete the knowledge of the Atlantic and Pacific oceans microseismic noise sources, we analyse 1 yr of continuous data recorded by permanent seismic stations located in the Indian Ocean basin. We primarily focus on secondary microseisms (SM) that are dominated by Rayleigh waves between 6 and 11 s of period. Continuous... |
| Tipo: Text |
Palavras-chave: Surface waves and free oscillations; Indian Ocean. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00287/39825/38335.pdf |
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