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| Gualtieri, L; Stutzmann, E; Juretzek, C; Hadziioannou, C; Ardhuin, Fabrice. |
| Primary microseism is the less studied seismic background vibration of the Earth. Evidence points to sources caused by ocean gravity waves coupling with the seafloor topography. As a result, these sources should be in water depth smaller than the wavelength of ocean waves. Using a state-of-the-art ocean wave model, we carry out the first global-scale seismic modeling of the vertical-component power spectral density of primary microseisms. Our modeling allows us to infer that the observed weak seasonality of primary microseisms in the southern hemisphere corresponds to a weak local seasonality of the sources. Moreover, a systematic analysis of the source regions that mostly contribute to each station reveals that stations on both the East and West sides of... |
| Tipo: Text |
Palavras-chave: Numerical modelling; Computational seismology; Seismic noise; Theoretical Seismology. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00487/59842/62990.pdf |
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| Trabattoni, A; Barruol, G; Dreo, R; Boudraa, A O; Fontaine, F R. |
| Breakthroughs in understanding the structure and dynamics of our planet will strongly depend upon instrumenting deep oceans. Progress has been made these last decades in ocean-bottom seismic observations, but ocean-bottom seismometer (OBS) temporary deployments are still challenging and face set-up limitations. Launched from oceanographic vessels, OBSs fall freely and may slightly drift laterally, dragged by currents. Therefore, their actual orientation and location on the landing sites are hard to assess precisely. Numerous techniques have been developed to retrieve this key information, but most of them are costly, time-consuming or inaccurate. In this work, we show how ship noise can be used as an acoustic source of opportunity to retrieve both the... |
| Tipo: Text |
Palavras-chave: Seismic instruments; Seismic noise; Wave propagation; Body waves; Statistical methods; Acoustic properties. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00593/70463/68591.pdf |
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| 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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| Hable, Sarah; Sigloch, Karin; Stutzmann, Eleonore; Kiselev, Sergey; Barruol, Guilhem. |
| We use seismic noise cross-correlations to obtain a 3-D tomography model of SV-wave velocities beneath the western Indian Ocean, in the depth range of the oceanic crust and uppermost mantle. The study area covers 2000×2000 km2 between Madagascar and the three spreading ridges of the Indian Ocean, centred on the volcanic hotspot of La Réunion. We use seismograms from 38 ocean bottom seismometers (OBSs) deployed by the RHUM-RUM project and 10 island stations on La Réunion, Madagascar, Mauritius, Rodrigues, and Tromelin. Phase cross-correlations are calculated for 1119 OBS-to-OBS, land-to-OBS, and land-to-land station pairs, and a phase-weighted stacking algorithm yields robust group velocity measurements in the period range of 3-50 s. We demonstrate that OBS... |
| Tipo: Text |
Palavras-chave: Crustal imaging; Seismic instruments; Seismic interferometry; Seismic noise; Seismic tomography. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00508/61988/66099.pdf |
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| Rascle, Nicolas; Ardhuin, Fabrice. |
| A multi-scale global hindcast of ocean waves is presented that covers the years 1994-2012, based on recently published parameterizations for wind sea and swell dissipation [Ardhuin, F., Rogers, E., Babanin, A., Filipot, J.-F., Magne, R., Roland, A., van der Westhuysen, A., Queffeulou, P., Lefevre, J.-M., Aouf, L., Collard, F., 2010. Semi-empirical dissipation source functions for wind-wave models: Part I. Definition, calibration and validation. J. Phys. Oceanogr. 40 (9), 1917-1941]. Results from this hindcast include traditional wave parameters, like the significant wave height and mean periods, and we particularly consider the accuracy of the results for phenomenal sea states, with significant heights above 14 m. Using unbiased winds, there is no evidence... |
| Tipo: Text |
Palavras-chave: Waves; Hindcast; Air-sea fluxes; Stokes drift; Mean square slope; Seismic noise. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00155/26582/25477.pdf |
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| 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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| Hable, Sarah; Sigloch, Karin; Barruol, Guilhem; Staehler, Simon C.; Hadziioannou, Celine. |
| Many applications in seismology rely on the accurate absolute timing of seismograms. However, both seismological land stations and ocean bottom seismometers (OBSs) can be affected by clock errors, which cause the absolute timing of seismograms to deviate from a highly accurate reference time signal, usually provided by GPS satellites. Timing problems can occur in land stations when synchronization with a GPS signal is temporarily or permanently lost. This can give rise to complicated, time-dependent clock drifts relative to GPS time, due to varying environmental conditions. Seismometers at the ocean bottom cannot receive GPS satellite signals, but operate in more stable ambient conditions than land stations. The standard protocol is to synchronize an OBS... |
| Tipo: Text |
Palavras-chave: Time-series analysis; Seismic instruments; Seismic interferometry; Seismic noise. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00444/55599/57230.pdf |
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