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Registros recuperados: 12
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Anisotropic Tomography Around La Reunion Island From Rayleigh Waves ArchiMer
Mazzullo, Alessandro; Stutzmann, Eleonore; Montagner, Jean-paul; Kiselev, Sergey; Maurya, Satish; Barruol, Guilhem; Sigloch, Karin.
In the western Indian Ocean, the Reunion hot spot is one of the most active volcanoes on Earth. Temporal interactions between ridges and plumes have shaped the structure of the zone. This study investigates the mantle structure using data from the Reunion Hotspot and Upper Mantle-Reunions Unterer Mantel (RHUM-RUM) project, which significantly increased the seismic coverage of the western part of the Indian Ocean. For more than 1year, 57 ocean bottom seismometer stations and 23 temporary land stations were deployed over this area. For each earthquake station path, the Rayleigh wave fundamental mode phase velocities were measured for the periods from 30s to 300s and group velocities for the period from 16s to 250s. A three-dimensional model of the shear...
Tipo: Text Palavras-chave: Tomography; Indian Ocean; Seismic anisotropy; Hot spot ridge; Upper mantle.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00600/71180/69533.pdf
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Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources ArchiMer
Obrebski, Mathias; Ardhuin, Fabrice; Stutzmann, Eleonore; Schimmel, Martin.
Among the different types of waves embedded in seismic noise, body waves present appealing properties but are still challenging to extract. Here we first validate recent improvements in numerical modeling of microseismic compressional (P) body waves and then show how this tool allows fast detection and location of their sources. We compute sources at similar to 0.2 Hz within typical P teleseismic distances (30-90 degrees) from the Southern California Seismic Network and analyze the most significant discrete sources. The locations and relative strengths of the computed sources are validated by the good agreement with beam-forming analysis. These 54 noise sources exhibit a highly heterogeneous distribution, and cluster along the usual storm tracks in the...
Tipo: Text Palavras-chave: Compressionnal body waves; Noise source; Double frequency microseism; Numerical modeling.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00161/27251/25448.pdf
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Frequency-dependent noise sources in the North Atlantic Ocean ArchiMer
Sergeant, Amandine; Stutzmann, Eleonore; Maggi, Alessia; Schimmel, Martin; Ardhuin, Fabrice; Obrebski, Mathias.
[1] Secondary microseisms are the most energetic waves in the noise spectra between 3 and 10 s. They are generated by ocean wave interactions and are predominantly Rayleigh waves. We study the associated noise sources in the North Atlantic Ocean by coupling noise polarization analysis and source mapping using an ocean wave model that takes into account coastal reflections. From the Rayleigh wave polarization analysis, we retrieve the back azimuth to the noise sources in the time-frequency domain. Noise source modeling enables us to locate the associated generation areas at different times and frequencies. We analyze the distribution of secondary microseism sources in the North Atlantic Ocean using 20 broadband stations located in the Arctic and around the...
Tipo: Text Palavras-chave: Noise sources; Secondary microseism; North Atlantic Ocean; Polarization.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00169/28075/26290.pdf
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How ocean waves rock the Earth: two mechanisms explain microseisms with periods 3 to 300 s ArchiMer
Ardhuin, Fabrice; Gualtieri, Lucia; Stutzmann, Eleonore.
Microseismic activity, recorded everywhere on Earth, is largely due to ocean waves. Recent progress has clearly identified sources of microseisms in the most energetic band, with periods from 3 to 10 s. In contrast, the generation of longer-period microseisms has been strongly debated. Two mechanisms have been proposed to explain seismic wave generation: a primary mechanism, by which ocean waves propagating over bottom slopes generate seismic waves, and a secondary mechanism which relies on the nonlinear interaction of ocean waves. Here we show that the primary mechanism explains the average power, frequency distribution, and most of the variability in signals recorded by vertical seismometers, for seismic periods ranging from 13 to 300 s. The secondary...
Tipo: Text Palavras-chave: Hum; Infragravity waves; Numerical model; Microseisms.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00251/36219/34769.pdf
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Infragravity waves: from driving mechanisms to impacts ArchiMer
Bertin, Xavier; De Bakker, Anouk; Van Dongeren, Ap; Coco, Giovanni; Andre, Gael; Ardhuin, Fabrice; Bonneton, Philippe; Bouchette, Frederic; Castelle, Bruno; Crawford, Wayne C.; Davidson, Mark; Deen, Martha; Dodet, Guillaume; Guerin, Thomas; Inch, Kris; Leckler, Fabien; Mccall, Robert; Muller, Heloise; Olabarrieta, Maitane; Roelvink, Dano; Ruessink, Gerben; Sous, Damien; Stutzmann, Eleonore; Tissier, Marion.
Infragravity (hereafter IG) waves are surface ocean waves with frequencies below those of wind-generated "short waves" (typically be- low 0.04 Hz). Here we focus on the most common type of IG waves, those induced by the presence of groups in incident short waves. Three related mechanisms explain their generation: (1) the development, shoaling and release of waves bound to the short-wave group envelopes (2) the modulation by these envelopes of the location where short waves break, and (3) the merging of bores (breaking wave front, resembling to a hydraulic jump) inside the surfzone. When reaching shallow water (O(1-10 m)), IG waves can transfer part of their energy back to higher frequencies, a process which is highly dependent on beach slope. On gently...
Tipo: Text Palavras-chave: Infragravity waves; Bound wave; Dissipation; Reflection; Sediment transport; Barrier breaching; Seiche; Earth hum.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00417/52876/53800.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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Ocean wave sources of seismic noise ArchiMer
Ardhuin, Fabrice; Stutzmann, Eleonore; Schimmel, Martin; Mangeney, Anne.
Noise with periods 3 to 10 s, ubiquitous in seismic records, is expected to be mostly generated by pairs of ocean wave trains of opposing propagation directions with half the seismic frequency. Here we present the first comprehensive numerical model of microseismic generation by random ocean waves, including ocean wave reflections. Synthetic and observed seismic spectra are well correlated (r > 0.85). On the basis of the model results, noise generation events can be clustered in three broad classes: wind waves with a broad directional spectrum (class I), sea states with a significant contribution of coastal reflections (class II), and the interaction of two independent wave systems (class III). At seismic stations close to western coasts, noise...
Tipo: Text
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00044/15531/12926.pdf
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Phenomenal sea states and swell from a North Atlantic Storm in February 2011: a comprehensive analysis ArchiMer
Hanafin, Jennifer; Quilfen, Yves; Ardhuin, Fabrice; Sienkiewicz, Joseph; Queffeulou, Pierre; Obrebski, Mathias; Chapron, Bertrand; Reul, Nicolas; Collard, Fabrice; Corman, David; De Azevedo, Eduardo B.; Vandemark, Doug; Stutzmann, Eleonore.
Tipo: Text
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00094/20538/18197.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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Sea state trends and variability: consistency between models, altimeters, buoys, and seismic data (1979‐2016) ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Stutzmann, Eleonore; Lecocq, Thomas.
Wave hindcasts of long time series (> 30 years) have been instrumental in understanding the wave climate. However it is still difficult to have a consistent reanalysis suitable for study of trends and inter‐annual variability. Here we explore the consistency of a wave hindcast with independent observations from moored buoys, satellite altimeters, and seismic data. We use the Climate Forecast System Reanalysis (CFSR) winds to drive a wave model since extreme events are generally well captured. Unfortunately the original CFSR winds are not homogeneous in time. We systematically modify this wind field in time and space to produce a wave field that has homogeneous differences against the Globwave/SeaStateCCI altimeter wave height database. These corrections...
Tipo: Text Palavras-chave: Wave hindcasting; COWCLIP; Seismic noise; Long-term trends; Climate Forecast System Reanalysis; Data homogeneity.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00490/60181/63522.pdf
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The Earth's hum variations from a global model and seismic recordings around the Indian Ocean ArchiMer
Deen, M.; Stutzmann, Eleonore; Ardhuin, Fabrice.
The Earth's hum is the continuous oscillations of the Earth at frequencies between 2 and 20 mHz in the absence of earthquakes. The hum strongest signal consists mainly of surface waves. These seismic waves can be generated by infragravity waves propagating over a sloping ocean bottom close to the coast. So far, this theory has only been tested quantitatively using European seismic stations. We use seismic data recorded all around the Indian Ocean together with an ocean wave model that provides time‐frequency varying hum sources. We show that seasonal variations of the hum sources are smaller in the southern hemisphere (SH) than the northern hemisphere (NH). Using these sources, we model Rayleigh wave RMS amplitudes in the period band 3.5‐20 mHz, and the...
Tipo: Text Palavras-chave: Seismic hum; Infragravity waves; Indian Ocean; Seismic noise; Hum sources; Modeling.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00455/56678/58435.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
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