Papers by Jacques Hinderer
Geophysical Journal International, 1982
The basic equations describing the dynamical effects of the Earth's fluid core (Liouville, Navier... more The basic equations describing the dynamical effects of the Earth's fluid core (Liouville, Navier-Stokes and elasticity equations) are derived for an ellipsoidal earth model without axial symmetry but with an homogeneous and deformable fluid core and elastic mantle. We develop the balance of moment of momentum up t o the second order and use Love numbers t o describe the inertia tensor's variations. The inertial torque takes into account the ellipticity and the volume change of the liquid core. On the core-mantle boundary we locate dissipative, magnetic and viscous torques. In this way we obtain quite a complete formulation for the Liouville equations. These equations are restricted in order to obtain the usual Chandler and nearly diurnal eigenfrequencies. Then we propose a method for calculating the perturbations of these eigenfrequencies when considering additional terms in the Liouville equations.
Variations temporelles de la gravité en relation avec la dynamique interne de la Terre Apport des... more Variations temporelles de la gravité en relation avec la dynamique interne de la Terre Apport des gravimètres supraconducteurs présentée par
Le parcours d'une thèse m'a souvent fait penser à un voyage initiatique dont je tiens à remercier... more Le parcours d'une thèse m'a souvent fait penser à un voyage initiatique dont je tiens à remercier toute l'équipée. Le rôle du mentor revient à Jacques Hinderer, qui m'a donné l'opportunité de commencer cette aventure de longue haleine. Je le remercie chaleureusement pour la confiance qu'il m'a accordée, ainsi que pour ses encouragements et ses conseils m'ayant guidé au travers des dédales de la géodésie. Ce travail n'aurait été possible sans l'encadrement discret mais constant de Guillaume Favreau. Sa connaissance des différents visages de l'Afrique sahélienne m'ont été d'une aide précieuse pendant ces trois années de thèse. Je tiens également à remercier Marie Boucher pour son écoute attentive de la résonance des protons. Un grand merci à Bernard Cappelaere dont les avis éclairés ont su guidé mes pas d'hydrologue débutante. Je remercie également sincèrement Cédric Champollion pour m'avoir redonné foi en la microgravimétrie. Je n'oublie pas Jean-Paul Boy et Caroline de Linage, dont les yeux exercés savent observer les mouvements de la Terre depuis l'espace. Merci également à Jérôme Demarty, Natalie Benarrosh et à tous les intervenants impliqués dans la mise en place et le maintien de l'observatoire AMMA-CATCH Niger. J'adresse mes sincères remerciements aux rapporteurs de cette thèse Hervé Jourde, Nicolas Florsch et Frédéric Masson pour leurs lectures critiques et constructives. Merci à Pierre Genthon d'avoir pris le temps de venir à ma soutenance. Cette formidable expérience n'aurait été possible sans les bras, les têtes et les jambes de nombreux compagnons de terrain: Bernard, Nicolas, Martha, Sébastien, Monique, Maxime, Olivier, merci d'avoir porté ces gravimètres en des coins reculés de l'Afrique de l'Ouest. Merci également { Yahaya Nazoumou et { tous les étudiants de l'université de Niamey venus nous soutenir sur le terrain. Merci à Thibaud pour avoir sillonné la mare et les ravines de Wankama avec son attirail de géomètre. Merci à Bodo pour sa conduite de pilote. Je ne saurais assez remercier les habitants du village de Wankama pour leur accueil. Je tiens également à remercier tout le personnel de la représentation IRD Niger pour leur aide irremplaçable sur place qui a rendu ce travail possible. Puis viennent les coéquipiers de ce voyage: une troupe de docteurs apprentis ou confirmés, ingénieurs, étudiants, secrétaires, maîtres de conférences, professeurs et que sais-je encore. Merci { toute l'équipe de l'Institut de Physique du Globe de Strasbourg pour avoir rendu ce iv travail possible. Je tiens particulièrement à remercier l'équipe de dynamique globale pour le cadre de travail agréable qu'ils ont su instauré et savent si bien partager. Merci aux gestionnaires et secrétaires souvent mises à contribution lors des nombreuses missions effectuées au cours de cette thèse. J'adresse également une foule de remerciements aux ex ou futurs géodocteurs:
The authors present some examples of Earth's deformation under various physical processes... more The authors present some examples of Earth's deformation under various physical processes, using a Love numbers formalism: taking into account these effects may be usefull when establishing reference systems. Major perturbations are generated by atmospheric loading effects and corresponding deformations are found to reach an amplitude of one centimeter. Other effects are smaller.
C R Acad Sci Ser Ii a, 2001
Ocean loading involves both the dynamic and geometric effects that result from the action of ocea... more Ocean loading involves both the dynamic and geometric effects that result from the action of ocean water masses on the crust. Gravity variations are generated by the direct attraction of the ocean masses, by the deformation of the crust and by the redistribution potential of the masses. Such effects are still perceptible far inland. A Green's function formalism, using loading Love numbers, allows to predict the loading effects. We present here the first French experiment in coastal areas devoted to the study of this phenomenon. The campaign took place in Brest in March 1998. The absolute gravimeter of the French community recorded during four days the gravity changes. Once the standard contributions (body tides, atmospheric pressure effect, polar motion) are removed, the residual variations are mainly due to the ocean loading and they can be confronted to the models. The observed gravity variations exceed by 16 % the theoretical predictions, and we impute this fact to the raw spatial resolution of the global ocean tide models, with a strong consequence near the coasts. Improvements are needed in all the geodetic features of coastal type (tide gauge links, vertical displacement displacement, motion of reference geodetic stations), and also in the validation of the hydrodynamic models by using gravity as an integrating quantity.
Geothermal Energy, 2015
The study is devoted to the monitoring of a geothermal reservoir by hybrid gravimetry combining d... more The study is devoted to the monitoring of a geothermal reservoir by hybrid gravimetry combining different types of instruments (permanent superconducting gravimeter, absolute ballistic gravimeter, and micro-gravimeters) and different techniques of measurements (both time-discrete and recording data collection). Using a micro-gravimetric repetition network around a reference station, which is regularly measured, leads to the knowledge of the time and space changes in surface gravity. Such changes can be linked to the natural or anthropic activities of the reservoir. A feasibility study using this methodology is applied to two geothermal sites in the Alsace region (France) of the Rhine graben. We show the results in terms of gravity double differences from weekly repetitions of a network of 11 stations around the geothermal reservoir of Soultz-sous-Forêts, separated into 5 loops during July-August 2013 and 2014 as well as preliminary results from 2 stations near Rittershoffen (ECOGI). We point out the importance of a precise leveling of the gravity points for the control of the vertical deformation. A first modeling of surface gravity changes induced by realistic geothermal density perturbations (Newtonian attraction) is computed in the frame of the existing geological model and leads to gravity changes below the μGal level being hence undetectable. However, and for the same case, borehole gravity modeling showed a significant anomaly with depth that can be used as a complementary monitoring method. We show that in the limit of our uncertainties (SD ~5 μGal), we do not detect any significant gravity change on the geothermal site of Soultz in agreement with the fact that there was indeed no geothermal activity during our analysis period. On the contrary, the measurements near Rittershoffen show a signal above the noise level which correlates in time with a production test but cannot be explained in terms of Newtonian attraction effects according to our basic numerical simulation.
We investigate the time-variable gravity changes in Europe retrieved from the initial GRACE month... more We investigate the time-variable gravity changes in Europe retrieved from the initial GRACE monthly solutions spanning a 21-month duration from April 2002 to December 2003. Gravity anomaly maps are retrieved from the satellite solutions from which we compare the fields according to various truncation levels (typically between degree 10 and 20) of the initial fields. For these different degrees, an empirical orthogonal function (EOF) decomposition of the time-variable gravity field leads us to its main spatial and temporal characteristics. We show that the dominant signal is found to be annual with amplitude and phase in agreement with predictions in Europe using snow and soil-moisture variations from recent hydrology models. We compare these GRACE gravity field changes to surface gravity observations from 6 superconducting gravimeters of the GGP (Global Geodynamics Project) European subnetwork, with a special attention to loading corrections. Initial results suggest that all 3 data sets (GRACE, hydrology load and GGP) respond to annual changes in near-surface water in Europe of a few microGal (at length scales of ~ 1000 km) that show a high value in winter and a summer minimum. We also point out that the GRACE gravity field evolution seems to indicate that there is a trend in gravity between summer 2002 and summer 2003 which can be related to the 2003 heatwave in Europe and its hydrological consequences (drought). Despite the limited time span of our analysis and the uncertainties in retrieving a regional solution from the network of gravimeters, the calibration and validation aspects of the GRACE data processing based on the annual hydrology cycle in Europe are in progress.
We first review some history of the Global Geodynamics Project (GGP), particularly in the progres... more We first review some history of the Global Geodynamics Project (GGP), particularly in the progress of ground-satellite gravity comparisons. The GGP Satellite Project has involved the measurement of ground-based superconducting gravimeters (SGs) in Europe for several years and we make quantitative comparisons with the latest satellite GRACE data and hydrological models. The primary goal is to recover information about seasonal hydrology cycles, and we find a good correlation at the microgal level between the data and modeling. One interesting feature of the data is low soil moisture resulting from the European heat wave in 2003. An issue with the ground-based stations is the possibility of mass variations in the soil above a station, and particularly for underground stations these have to be modeled precisely. Based on this work with a regional array, we estimate the effectiveness of future SG arrays to measure co-seismic deformation and silent-slip events. Finally we consider gravity surveys in volcanic areas, and predict the accuracy in modeling subsurface density variations over time periods from months to years.
As has been recognized for several years, attempts to validate GRACE satellite data using any kin... more As has been recognized for several years, attempts to validate GRACE satellite data using any kind of ground data immediately runs into the problem of horizontal scale lengths. Over Europe we have only 7 GGP stations operating since GRACE observations began and these are insufficient to give more than a simple averaging of local hydrology variations. Yet the approach from averaging ground stations is conceptually correct and would be effective if we had numerous stations all situated at the ground / atmosphere interface. Here we review how a combination of surface and underground stations (i.e. those measuring gravity below a local soil moisture horizon) can be used to validate satellite data. We show results from several GRACE models with the European GGP data since 2002.
For several years, it has been the goal of the Global Geodynamics Project (GGP) to convert high r... more For several years, it has been the goal of the Global Geodynamics Project (GGP) to convert high rate acceleration data recorded on superconducting gravimeters (SG) to a format compatible with the seismic data archived at IRIS. The problem for the GGP community has been to properly establish the metadata for characterizing the response of the instrument, particularly its phase characteristics.
Studia Geophysica et Geodaetica, 2014
Since 1973, the Gravimetric Observatory of Strasbourg (France) is located in an old fort named J9... more Since 1973, the Gravimetric Observatory of Strasbourg (France) is located in an old fort named J9 and has been the place for various gravity experiments. We present a comparison of the noise levels of various instruments that are or were continuously
Treatise on Geophysics, 2007
A major challenge in water resources research is to document the spatial and temporal variability... more A major challenge in water resources research is to document the spatial and temporal variability of the hydrological processes over short time and space scales. Indeed, the quality of model predictions for resource assessment is dependent on reliable datasets, representative of the hydrological regime and its variations. This issue is particularly sensitive in Sahelian Africa, where available hydrological datasets are scarce. In this study, the variability of the water storage was investigated at the subcatchment scale (< 1km) by an intensive microgravity field campaign. Weekly microgravity surveys were carried out in a small endoreic catchment in Southwest Niger, during three months of the rainy season in 2009. Gravity measurements were performed at 16 stations located near a temporary pond, where rapid infiltration towards the aquifer occurs. The highest (63 μGal) gravity signal was measured on a station located above the pond and is well explained by the direct effect of the ...
Water Resources Research, 2013
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
The purpose of this paper is to investigate the role of the correlation between atmospheric press... more The purpose of this paper is to investigate the role of the correlation between atmospheric pressure and gravity in the context of a single scalar admittance. We consider two GGP data sets from Boulder and Strasbourg, both of which we processed from the raw data before decimating to 1minute files. The cross correlation and scalar admittance between gravity and pressure were determined for 3 averaging windows of 1 hour, 6 hours and 1 day. The data clearly show that cross correlation and admittance are related; furthermore, the shorter the averaging window the more the scatter in both quantities. We found that when the correlation was high the admittance tended towards a value that was higher for shorter windows and higher frequencies. Our attempts to use the correlation to improve the traditional assumption of a single scalar factor (e.g. -0.3 µgal mbar-1) were unsuccessful, probably due to the inherent noise in the gravity residuals.
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Papers by Jacques Hinderer