| Records |
| Author |
Hubert G., Pazianotto M. T., Federico C. A. |
| Title |
Modeling of ground albedo neutrons to investigate seasonal cosmic ray‐induced neutron variations measured at high‐altitude stations |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Space Physics |
Abbreviated Journal |
|
| Volume |
121 |
Issue |
12 |
Pages |
12,186-12,201 |
| Keywords |
albedo neutron cosmic ray spectrometer |
| Abstract |
Abstract This paper investigates seasonal cosmic ray?induced neutron variations measured over a long?term period (from 2011 to 2016) in both the high?altitude stations located in medium geomagnetic latitude and Antarctica (Pic?du?Midi and Concordia, respectively). To reinforce analysis, modeling based on ground albedo neutrons simulations of extensive air showers and the solar modulation potential was performed. Because the local environment is well known and stable over time in Antarctica, data were used to validate the modeling approach. A modeled scene representative to the Pic?du?Midi was simulated with GEANT4 for various hydrogen properties (composition, density, and wet level) and snow thickness. The orders of magnitudes of calculated thermal fluence rates are consistent with measurements obtained during summers and winters. These variations are dominant in the thermal domain (i.e., En??20?MeV) is weakly impacted. The role of hydrogen content on ground albedo neutron generation was investigated with GEANT4 simulations. These investigations focused to mountain environment; nevertheless, they demonstrate the complexity of the local influences on neutron fluence rates. |
| Programme |
1112 |
| Campaign |
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| Address |
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| Corporate Author |
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| Publisher |
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Place of Publication |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2169-9380 |
ISBN  |
2169-9380 |
Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
6722 |
| Permanent link to this record |
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| Author |
Marchaudon A., Blelly P.‐L. |
| Title |
A new interhemispheric 16‐moment model of the plasmasphere‐ionosphere system: IPIM |
Type |
Journal |
| Year |
2015 |
Publication |
Journal of Geophysical Research: Space Physics |
Abbreviated Journal |
|
| Volume |
120 |
Issue |
7 |
Pages |
5728-5745 |
| Keywords |
centrifugal acceleration interhemispheric exchanges mirror force temperature anisotropy |
| Abstract |
Abstract We present a new interhemispheric numerical model: the IRAP plasmasphere?ionosphere model (IPIM). This model describes the transport of the multispecies ionospheric plasma from one hemisphere to the other along convecting and corotating magnetic field lines, taking into account source processes at low altitude such as photoproduction, chemistry, and energization through the coupling with a kinetic code solving the transport of suprathermal electron along the field line. Among the new developments, a 16?moment?based approach is used for the transport equations in order to allow development of strong temperature anisotropy at high altitude and we consider important but often neglected effects, such as inertial acceleration (centrifugal and Coriolis). In this paper, after presenting in detail the principle of the model, we focus on preliminary results showing the original contribution of this new model. For these first runs, we simulate the convection and corotation transport of closed flux tubes in the plasmasphere for tilted/eccentric dipolar magnetic field configuration in solstice and equinox conditions. We follow different flux tubes between 1.2 and 6 Earth Radii (RE) and demonstrate the capability of the model to describe a wide range of density (above 15 orders of magnitude). The relevance of the mathematical approach used is highlighted, as anisotropies can develop above 3000?km in the plasmasphere as a result of the mirroring effect related to the anisotropic pressure tensor. Moreover, we show that the addition of inertial acceleration may become critical to describe plasma interhemispheric transport above 4RE. The ability of the model to describe the external plasmasphere is demonstrated, and innovative studies are foreseen, regarding the dynamics of the plasma along the magnetic field lines (in particular interhemispheric exchanges and ?opening?/?closure? of a flux tube). |
| Programme |
312 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2169-9380 |
ISBN |
2169-9380 |
Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
6855 |
| Permanent link to this record |
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| Author |
Neala Creasy, Maureen D. Long, Heather A. Ford |
| Title |
Deformation in the lowermost mantle beneath Australia from observations and models of seismic anisotropy |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
122 |
Issue |
7 |
Pages |
5243-5267 |
| Keywords |
anisotropy lowermost mantle mantle dynamics postperovskite shear wave splitting |
| Abstract |
Observations of seismic anisotropy near the core-mantle boundary may yield constraints on patterns of lowermost mantle flow. We examine seismic anisotropy in the lowermost mantle beneath Australia, bounded by the African and Pacific Large Low Shear Velocity Provinces. We combined measurements of differential splitting of SKS-SKKS and S-ScS phases sampling our study region over a range of azimuths, using data from 10 long-running seismic stations. Observations reveal complex and laterally heterogeneous anisotropy in the lowermost mantle. We identified two subregions for which we have robust measurements of D″-associated splitting for a range of ray propagation directions and applied a forward modeling strategy to understand which anisotropic scenarios are consistent with the observations. We tested a variety of elastic tensors and orientations, including single-crystal elasticity of lowermost mantle minerals (bridgmanite, postperovskite, and ferropericlase), tensors based on texture modeling in postperovskite aggregates, elasticity predicted from deformation experiments on polycrystalline MgO aggregates, and tensors that approximate the shape preferred orientation of partial melt. We find that postperovskite scenarios are more consistently able to reproduce the observations. Beneath New Zealand, the observations suggest a nearly horizontal [100] axis orientation with an azimuth that agrees well with the horizontal flow direction predicted by previous mantle flow models. Our modeling results further suggest that dominant slip on the (010) plane in postperovskite aggregates provides a good fit to the data but the solution is nonunique. Our results have implications for the mechanisms of deformation and anisotropy in the lowermost mantle and for the patterns of mantle flow. |
| Programme |
133 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
|
Edition |
|
| ISSN |
2169-9356 |
ISBN |
2169-9356 |
Medium |
|
| Area |
|
Expedition |
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Conference |
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| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7324 |
| Permanent link to this record |
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| |
| Author |
Agnès Chounet, Martin Vallée |
| Title |
Global and Interregion Characterization of Subduction Interface Earthquakes Derived From Source Time Functions Properties |
Type |
Journal |
| Year |
2018 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
123 |
Issue |
7 |
Pages |
5831-5852 |
| Keywords |
global earthquake seismology radiated energy seismic coupling source time functions stress drop subduction earthquakes |
| Abstract |
Source time functions (STFs) describe how the seismic moment rate is released with time, and carry information on integral rupture properties, such as static stress drop and radiated energy. In this study, we systematically analyze a set of 1,433 STFs extracted from the SCARDEC method (Vallée and Douet, 2016, https://doi.org/10.1016/j.pepi.2016.05.012), containing the Mw≥5.6, shallow (z≤70 km) earthquakes with dip-slip mechanism that occurred between 1992 and 2014. At the global scale, STFs properties indicate scale invariance of stress drop and scaled radiated energy with magnitude. In a second step, these source parameters are investigated in light of the tectonic context of the earthquakes: in agreement with other approaches, we observe that subduction interface earthquakes have lower stress drop and scaled radiated energy relative to all other earthquakes (e.g., crustal earthquakes). Finally, a focus on subduction interface earthquakes (approximately 800 earthquakes) is done by considering 18 regional segments of subduction zones. We find that these segments do not have the same signature in terms of macroscopic rupture properties, which means that large-scale plate convergence and mechanical properties influence rupture behavior. In a given segment, local heterogeneities of stress drop or radiated energy can be associated with local features of the subduction zone: in particular, we find that low coupled zones generate earthquakes with low stress drop and scaled radiated energy. This last feature, also observed at a larger scale, suggests a positive correlation between coupling and stress drop. |
| Programme |
133 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
|
Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
|
Edition |
|
| ISSN |
2169-9356 |
ISBN |
2169-9356 |
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7383 |
| Permanent link to this record |
| |
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| |
| Author |
Kiwamu Nishida, Takuto Maeda, Yoshio Fukao |
| Title |
Seismic Observation of Tsunami at Island Broadband Stations |
Type |
Journal |
| Year |
2019 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
124 |
Issue |
2 |
Pages |
1910-1928 |
| Keywords |
broadband seismometer tsunami propagation |
| Abstract |
Previous studies have reported seismic observations of tsunami recorded at island broadband stations. Coastal loading by the tsunami can explain them. For further quantification, we model tsunami propagation assuming an axisymmetric structure: a conical island with a flat ocean floor. The total tsunami wavefield can be represented by superposition between an incident tsunami wave and the scattering. The ground deformation due to the total tsunami wavefield at the center is calculated using static Green's functions for elastic half-space with a first-order correction for bathymetry. By fitting the modeled displacement to observed seismic data, we can infer the incident tsunami wave, which can be interpreted as the virtual tsunami amplitude without the conical island. First, we apply this new method to three components of seismic data at a volcano island, Aogashima, for the 2015 Torishima-Oki tsunami earthquake. The estimated tsunami amplitude from the vertical component is consistent with the offshore array observation of absolute pressure gauges close to the island (1.5–20 mHz). The estimated incident azimuth from the three components is also consistent with ray theory. Second, we apply this method to seismic data at four island broadband stations in the Indian ocean for the 2010 Mentawai tsunami earthquake in Indonesia. Despite the limited observed frequency range from 0.5–2.0 mHz, the amplitudes and incident azimuths are consistent with past studies. These observations can complement offshore tsunami observations. Moreover, this method is applicable not only for a tsunami but also for background ocean infragravity wave activity. |
| Programme |
133 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2169-9356 |
ISBN |
2169-9356 |
Medium |
|
| Area |
|
Expedition |
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Conference |
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| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7508 |
| Permanent link to this record |
| |
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| |
| Author |
Pejić Tanja, Tkalčić Hrvoje, Sambridge Malcolm, Cormier Vernon F., Benavente Roberto |
| Title |
Attenuation tomography of the upper inner core |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
122 |
Issue |
4 |
Pages |
3008-3032 |
| Keywords |
attenuation inner core tomography |
| Abstract |
Abstract The solidification of the Earth's inner core shapes its texture and rheology, affecting the attenuation and scattering of seismic body waves transmitted through it. Applying attenuation tomography in a Bayesian framework to 398 high?quality PKIKP waveforms, we invert for the apparent Qp for the uppermost 400?km below the inner core boundary at latitudes 45°S to 45°N. We use damping and smoothing for regularization of the inversion, and it seems that the smoothing regularization combined with the discrepancy principle works better for this particular problem of attenuation tomography. The results are consistent with a regional variation in inner core attenuation more complex than hemispherical, suggesting coupling between inner core solidification and the thermal structure of the lowermost mantle. |
| Programme |
133 |
| Campaign |
|
| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
|
| ISSN |
2169-9313 |
ISBN |
2169-9313 |
Medium |
|
| Area |
|
Expedition |
|
Conference |
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| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
6767 |
| Permanent link to this record |
| |
|
| |
| Author |
Creasy Neala, Long Maureen D., Ford Heather A. |
| Title |
Deformation in the lowermost mantle beneath Australia from observations and models of seismic anisotropy |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
122 |
Issue |
7 |
Pages |
5243-5267 |
| Keywords |
anisotropy lowermost mantle mantle dynamics postperovskite shear wave splitting |
| Abstract |
Abstract Observations of seismic anisotropy near the core?mantle boundary may yield constraints on patterns of lowermost mantle flow. We examine seismic anisotropy in the lowermost mantle beneath Australia, bounded by the African and Pacific Large Low Shear Velocity Provinces. We combined measurements of differential splitting of SKS?SKKS and S?ScS phases sampling our study region over a range of azimuths, using data from 10 long?running seismic stations. Observations reveal complex and laterally heterogeneous anisotropy in the lowermost mantle. We identified two subregions for which we have robust measurements of D??associated splitting for a range of ray propagation directions and applied a forward modeling strategy to understand which anisotropic scenarios are consistent with the observations. We tested a variety of elastic tensors and orientations, including single?crystal elasticity of lowermost mantle minerals (bridgmanite, postperovskite, and ferropericlase), tensors based on texture modeling in postperovskite aggregates, elasticity predicted from deformation experiments on polycrystalline MgO aggregates, and tensors that approximate the shape preferred orientation of partial melt. We find that postperovskite scenarios are more consistently able to reproduce the observations. Beneath New Zealand, the observations suggest a nearly horizontal [100] axis orientation with an azimuth that agrees well with the horizontal flow direction predicted by previous mantle flow models. Our modeling results further suggest that dominant slip on the (010) plane in postperovskite aggregates provides a good fit to the data but the solution is nonunique. Our results have implications for the mechanisms of deformation and anisotropy in the lowermost mantle and for the patterns of mantle flow. |
| Programme |
133 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2169-9313 |
ISBN |
2169-9313 |
Medium |
|
| Area |
|
Expedition |
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Conference |
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| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
6768 |
| Permanent link to this record |
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| |
| Author |
Zhitu Ma, Colleen A. Dalton |
| Title |
Evolution of the lithosphere in the Indian Ocean from combined earthquake and ambient noise tomography |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
|
| Volume |
122 |
Issue |
1 |
Pages |
354-371 |
| Keywords |
ambient noise Indian Ocean surface wave |
| Abstract |
Abstract Rayleigh wave dispersion extracted from ambient seismic noise has been widely used to image crustal and uppermost mantle structure. Applications of this approach in continental settings are abundant, but there have been relatively few studies within ocean basins. By cross-correlating ambient noise recorded at broadband seismic stations around the Indian Ocean, we demonstrate the feasibility of extracting high-quality, long-period (10?30 mHz) Rayleigh waves that traverse the entire ocean basin. High-quality Rayleigh wave cross-correlation functions can be obtained from stacking waveforms over less than 2 years at land stations and less than 4 years at island stations. We show that adding the dispersion information extracted from ambient noise to a global earthquake data set can improve the resolution of phase velocity maps by about 20% in the northern Indian Ocean, where the station distribution is the best. We find that a plate cooling model with a potential temperature of 1450°C and plate thickness of 125 km can fit both the seismic observations and seafloor topography. The Seychelles-Mascarene Plateau is characterized by anomalously slow velocity at 30 mHz. The inclusion of ambient noise data in the tomographic inversion shifts the slow velocity anomaly into better agreement with the topographic relief, allowing us to estimate its crustal thickness and confirm that the plateau's elevation is supported by thick crust. The 10 and 20 mHz phase velocity maps show a strong asymmetry across the Central Indian Ridge that is best explained by eastward asthenospheric flow emanating from nearby hot spots. |
| Programme |
133 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
|
Edition |
|
| ISSN |
2169-9313 |
ISBN |
2169-9313 |
Medium |
|
| Area |
|
Expedition |
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Conference |
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| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7326 |
| Permanent link to this record |
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| Author |
Park Young‐Hyang, Durand Isabelle, Kestenare Elodie, Rougier Gilles, Zhou Meng, d'Ovidio Francesco, Cotté Cédric, Lee Jae‐Hak |
| Title |
Polar Front around the Kerguelen Islands: An up‐to‐date determination and associated circulation of surface/subsurface waters |
Type |
Journal |
| Year |
2014 |
Publication |
Journal of Geophysical Research: Oceans |
Abbreviated Journal |
|
| Volume |
119 |
Issue |
10 |
Pages |
6575-6592 |
| Keywords |
Kerguelen Polar Front Southern Ocean |
| Abstract |
Abstract The circulation of iron?rich shelf waters around the Kerguelen Islands plays a crucial role for a climatically important, annually recurrent phytoplankton spring bloom over the sluggish shelf region and its downstream plume area along the Antarctic circumpolar flow. However, there is a long?standing confusion about the Polar Front (PF) in the Kerguelen region due to diverse suggestions in the literature for its geographical location with an extreme difference over 10° of latitude. Based on abundant historical hydrographic data, the in situ hydrographic and current measurements during the 2011 KEOPS2 cruise, satellite chlorophyll images, and altimetry?derived surface velocity fields, we determine and validate an up?to?date location of the PF around the Kerguelen Islands. Artificial Lagrangian particle trajectories computed from altimetric velocity time series are analyzed for the possible pathways and sources of different surface/subsurface waters advected into the chlorophyll bloom area east off the islands studied during the KEOPS2 cruise. The PF location determined as the northernmost boundary of the Winter Water colder than 2°C, which is also associated with a band of strong currents, appears to be primarily controlled by topography. The PF rounds the Kerguelen Islands from the south to deflect northward along the eastern escarpment up to the northeastern corner of the Kerguelen Plateau before making its southward retroflection. It is shown that the major surface/subsurface waters found within the deep basin east of the Kerguelen Islands originate from the shelf around the Heard Island, rather than from the shallow shelf north of the Kerguelen Islands. |
| Programme |
688 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
|
| ISSN |
2169-9275 |
ISBN |
2169-9275 |
Medium |
|
| Area |
|
Expedition |
|
Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
6839 |
| Permanent link to this record |
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| |
| Author |
Etienne Vignon, Frédéric Hourdin, Christophe Genthon, Hubert Gallée, Eric Bazile, Marie-Pierre Lefebvre, Jean-Baptiste Madeleine, Bas J. H. Van de Wiel |
| Title |
Antarctic boundary layer parametrization in a general circulation model: 1-D simulations facing summer observations at Dome C |
Type |
Journal |
| Year |
2017 |
Publication |
Journal of Geophysical Research: Atmospheres |
Abbreviated Journal |
|
| Volume |
122 |
Issue |
13 |
Pages |
6818-6843 |
| Keywords |
Antarctic Plateau atmospheric boundary layer GABLS4 general circulation model physical parametrizations |
| Abstract |
The parametrization of the atmospheric boundary layer (ABL) is critical over the Antarctic Plateau for climate modelling since it affects the climatological temperature inversion and the negatively buoyant near-surface flow over the ice-sheet. This study challenges state-of-the-art parametrizations used in general circulation models to represent the clear-sky summertime diurnal cycle of the ABL at Dome C, Antarctic Plateau. The Laboratoire de Météorologie Dynamique-Zoom model is run in a 1-D configuration on the fourth Global Energy and Water Cycle Exchanges Project Atmospheric Boundary Layers Study case. Simulations are analyzed and compared to observations, giving insights into the sensitivity of one model that participates to the intercomparison exercise. Snow albedo and thermal inertia are calibrated leading to better surface temperatures. Using the so-called “thermal plume model” improves the momentum mixing in the diurnal ABL. In stable conditions, four turbulence schemes are tested. Best simulations are those in which the turbulence cuts off above 35 m in the middle of the night, highlighting the contribution of the longwave radiation in the ABL heat budget. However, the nocturnal surface layer is not stable enough to distinguish between surface fluxes computed with different stability functions. The absence of subsidence in the forcings and an underestimation of downward longwave radiation are identified to be likely responsible for a cold bias in the nocturnal ABL. Apart from model-specific improvements, the paper clarifies on which are the critical aspects to improve in general circulation models to correctly represent the summertime ABL over the Antarctic Plateau. |
| Programme |
1013 |
| Campaign |
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| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
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Editor |
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| Language |
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Summary Language |
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Original Title |
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| Series Editor |
|
Series Title |
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Abbreviated Series Title |
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| Series Volume |
|
Series Issue |
|
Edition |
|
| ISSN |
2169-8996 |
ISBN |
2169-8996 |
Medium |
|
| Area |
|
Expedition |
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Conference |
|
| Notes |
|
Approved |
yes |
| Call Number |
|
Serial |
7196 |
| Permanent link to this record |
