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1. Muons tomography applied to geosciences and volcanology

Author

Marteau, J., Gibert, D., Lesparre, N., Nicollin, F., Noli, P., and Giacoppo, F.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment, Physics - Geophysics
Abstract

Imaging the inner part of large geological targets is an important issue in geosciences with various applications. Dif- ferent approaches already exist (e.g. gravimetry, electrical tomography) that give access to a wide range of informations but with identified limitations or drawbacks (e.g. intrinsic ambiguity of the inverse problem, time consuming deployment of sensors over large distances). Here we present an alternative and complementary tomography method based on the measurement of the cosmic muons flux attenuation through the geological structures. We detail the basics of this muon tomography with a special emphasis on the photo-active detectors., Comment: Invited talk at the 6th conference on New Developments In Photodetection (NDIP'11), Lyon-France, July 4-8, 2011; Nuclear Instruments and Methods in Physics Research Section A, 2011

Published
2012
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3. A high resolution study of trace elements and stable isotopes in oyster shells to estimate Central Asian Middle Eocene seasonality

Author

Bougeois, L., de Rafélis, M., Reichart, G.-J., de Nooijer, L.J., Nicollin, F., Dupont-Nivet, G., NWO-DARWIN: Sensing Seasonality: Validation of seasonal proxies using planktic foraminifera, NWO-VIDI: Is the collision between India and Asia responsible for global climate cooling?, Stratigraphy & paleontology, Stratigraphy and paleontology, Organic geochemistry, Paleomagnetism, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), NWO-DARWIN: Sensing Seasonality: Validation of seasonal proxies using planktic foraminifera, NWO-VIDI: Is the collision between India and Asia responsible for global climate cooling?, Stratigraphy & paleontology, Stratigraphy and paleontology, Organic geochemistry, and Paleomagnetism

Subjects
010504 meteorology & atmospheric sciences, δ18O, Temperature salinity diagrams, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Oyster shell, 010502 geochemistry & geophysics, Eocene, 01 natural sciences, Isotopes of oxygen, Sclerochronology, Geochemistry and Petrology, medicine, 0105 earth and related environmental sciences, Stable isotope ratio, Geology, Seasonality, medicine.disease, Arid, Asian climate change, Salinity, Oceanography, 13. Climate action
Abstract

Modern Asian climate is characterized by strong seasonality caused by the duality between monsoon-dominated conditions in southeastern Asia and semi-arid to arid conditions in Central Asia. Eocene high-resolution proxy records which enable the reconstruction of the onset and magnitude of changes in seasonality are lacking to understand in details how and when this climatic turnover pattern occurred. Here, we propose an original method to estimate inter- and intra-annual variabilities in seawater temperature and salinity recorded by carbonate shell growth increments of the fossil oyster Sokolowia buhsii (Grewingk) collected from Late Lutetian marine strata of the Proto-Paratethys in the southwestern Tarim Basin (western China). Elemental ratio (Mg/Ca, Mn/Ca) and carbonate stable isotope composition (delta O-18) were determined perpendicular to the growth lines of foliated calcite accumulated in the ligamental area during the oyster's lifetime. We use temperature dependant Mg incorporation to estimate seasonal temperature contrast in the past. Results suggest a warm annual average temperature (similar to 27-28 degrees C) with large offset between summer and winter temperatures (until Delta T similar or equal to 19 degrees C). Combining these temperature estimates with stable oxygen isotope analyses from the same growth increments we deconvolve seawater delta O-18(sw) as a proxy for salinity. This suggests an average annual salinity about similar to 34-35 increasing strongly during summermonths and decreasing inwinter. Based on these data we conclude that during the Middle Eocene, Central Asian climate was characterized by a strong intra-seasonal variability in both temperature and salinity. Although the subtidal setting might have contributed to the strong seasonal offsets this still suggests that semi-arid to arid conditions prevailed during summer, whereas winter was characterized by enhanced rainfall. These results are consistent with previous regional palaeoenvironmental data and climate modelling experiments. They thus attest for the reliability of the method developed here as a seasonal palaeoclimatic indicator.

Published
2014
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4. Muon tomography of the Soufrière of Guadeloupe (Lesser Antilles): Comparison with other geophysical imaging methods and assessment of volcanic risks

Author

Gibert, D., Lesparre, N., Marteau, J., Taisne, B., Nicollin, F., Coutant, O., Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique des 2 Infinis de Lyon (IP2I Lyon), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
1972 INFORMATICS / Sensor web, 0545 COMPUTATIONAL GEOPHYSICS / Modeling, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 8494 VOLCANOLOGY / Instruments and techniques, 8485 VOLCANOLOGY / Remote sensing of volcanoes
Abstract

International audience; Density tomography of rock with muons of cosmic origin measures the attenuation of the flux of particles crossing the object of interest to derive its opacity, i.e. the quantity of matter encountered by the particles along their trajectories. Recent progress in micro-electronics and particle detectors make field measurement possible and muon density tomography is gaining a growing interest (e.g. Tanaka et al., 2010; Gibert et al., 2010). We have constructed field telescopes based on the detectors of the OPERA experiment devoted to study neutrino oscillation (Lesparre et al., 2011a). Each telescope may be equipped with a variable number of detection matrices with 256 pixels. The spatial resolution is adaptable and is typically of about 20 meters (Lesparre et al., 2010). The telescopes are portable autonomous devices able to operate in harsh field conditions encountered on tropical volcanoes. The total power consumption is less than 40W, and an Ethernet link allows data downloading and remote control of the electronic devices and on-board computers. Larger high-resolution telescopes are under construction. The instruments have been successfully tested on the Etna and Soufrière of Guadeloupe volcanoes were a telescope is operating continuously since Summer 2010. Muon radiographies of the Soufrière lava dome reveal its very heterogeneous density structure produced by an intense hydrothermal circulation of acid fluids which alters its mechanical integrity leading to a high risk level of destabilisation. Small-size features are visible on the images and provide precious informations on the structure of the upper hydrothermal systems. Joined interpretation with other geophysical data available on the Soufrière - seismic tomography, electrical resistivity tomography, gravity data - is presented and discussed. Density muon tomography of the internal structure of volcanoes like the Soufrière brings important informations for the hazard evaluation an is particularly adapted to brought constraints on flank destabilization and hydrothermal circulation models. Tanaka et al., Three dimensional computational axial tomography scan of a volcano with cosmic ray muon radiography, J. Geophys. Res., 115, B12332, doi:10.1029/2010JB007677, 2010. Gibert et al., Muon Tomography: Plans for Observations in the Lesser Antilles, Earth Planets and Space, Vol. 52, 153-165, doi: 10.5047/eps.2009.07.003, 2010. Lesparre et al., Geophysical muon imaging: feasibility and limits, Geophysical Journal International, Vol. 183, 1348-1361, doi: 10.1111/j.1365-246X.2010.04790.x, 2010. Lesparre et al., Design and Operation of a Field Telescope for Cosmic Ray Geophysical Tomography, Nuclear Instruments and Methods in Physics Research A, to appear, 2011a. Lesparre et al., Bayesian Dual Inversion of Experimental Telescope Acceptance and Integrated Flux for Geophysical Muon Tomography, Geophysical Journal International, to appear, 2011b.

Published
2011

5. A high resolution study of trace elements and stable isotopes in oyster shells to estimate central asian middle eocene seasonality

Author

NWO-DARWIN: Sensing Seasonality: Validation of seasonal proxies using planktic foraminifera, NWO-VIDI: Is the collision between India and Asia responsible for global climate cooling?, Stratigraphy & paleontology, Stratigraphy and paleontology, Organic geochemistry, Paleomagnetism, Bougeois, L., de Rafélis, M., Reichart, G.-J., de Nooijer, L.J., Nicollin, F., Dupont-Nivet, G., NWO-DARWIN: Sensing Seasonality: Validation of seasonal proxies using planktic foraminifera, NWO-VIDI: Is the collision between India and Asia responsible for global climate cooling?, Stratigraphy & paleontology, Stratigraphy and paleontology, Organic geochemistry, Paleomagnetism, Bougeois, L., de Rafélis, M., Reichart, G.-J., de Nooijer, L.J., Nicollin, F., and Dupont-Nivet, G.

Published
2014

6. Aménagements du Néolithique moyen dans le marais de Dol, au pied de la butte de Lillemer (Ille-et-Vilaine)

Author

Luc Laporte, Vincent BERNARD, Catherine Bizien-Jaglin, Blanchet, S., Marie-France Dietsch-Sellami, Guitton, V., N, Guyodo J., Gael Hamon, Madioux, P., Naar, S., Nicollin, F., Noslier, A., Oberlin, C., Quesnel, L., Civilisations atlantiques & Archéosciences (C2A), Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Ministère de la Culture et de la Communication (MCC), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ministère de la Culture et de la Communication (MCC)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Université de Nantes (UN)-Université de Nantes (UN), Université de Rennes (UR)-Ministère de la Culture et de la Communication (MCC)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Université de Nantes (UN)-Université de Nantes (UN)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)

Subjects
Archéologie, milieux humides, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, [SHS.ENVIR]Humanities and Social Sciences/Environmental studies, Néolithique, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2003

7. Monitoring the excavation damaged zone by three-dimensional reconstruction of electrical resistivity

Author

Lesparre, N. (Nolwenn), Gibert, D. (Dominique), Nicollin, F. (Florence), Nussbaum, C. (Christophe), Adler, A. (Andy), Lesparre, N. (Nolwenn), Gibert, D. (Dominique), Nicollin, F. (Florence), Nussbaum, C. (Christophe), and Adler, A. (Andy)

Abstract

A damaged zone is formed during the excavation of underground galleries, altering the rock properties. From a perspective of nuclear waste storage in deep geological sites, there is a clear interest to monitor the rock properties in such zones. We constructed electrical resistivity tomograms as a function of time to monitor the damaged area in gallery 04 of the Mont Terri underground rock laboratory (Switzerland). Measurements were performed using electrode rings surrounding the gallery. The experience showed a heterogeneous distribution of damages around the gallery and their fast formation after the excavation. Two main areas were concerned by damage formation, located in regions where the bedding was tangential to the excavated gallery. Such re

Published
2013
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13. Mars 96 GPR program

Author

Barbin, Y., primary, Nicollin, F., additional, Kofman, W., additional, Zolotarev, V., additional, and Glotov, V., additional

Published
1995
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16. Joint inversion of P-wave velocity and density, application to La Soufrière of Guadeloupe hydrothermal system.

Author

Coutant, O., Bernard, M. L., Beauducel, F., Nicollin, F., Bouin, M. P., and Roussel, S.

Subjects
INVERSION (Geophysics), SPEED of P-waves (Seismology), GRAVITY, VOLCANOES, VOLCANIC hazard analysis, TOMOGRAPHY, BAYESIAN analysis, SEISMOLOGY
Abstract

SUMMARY We present the result of a 3-D gravity and P-wave traveltime joint inversion applied to the hydrothermal system of La Soufrière of Guadeloupe. The joint inversion process is used here to overcome the different resolution limitations attached to the two data sets. P-wave traveltimes were obtained from three active seismic surveys that were conducted from 2001 to 2007. Gravity data collected during a microgravity campaign is described in a companion paper. We use a joint inversion process based on a Bayesian formulation and a deterministic iterative approach. The coupling between slowness and density is introduced through a supplementary constraint in the misfit function that tries to minimize the distance between parameter values and a theoretical relationship. This relationship is derived from measurements on samples representative of Mt Pelée of Martinique and La Soufrière volcanoes. We chose a grid discretization that leads to an under-determined problem that we regularize using spatial exponential covariance between the nodes parameters. Our results are compared to geophysical electromagnetic results obtained using resistivity and VLF surveys. They confirm the presence of highly contrasted dense/fast and light/slow zones in La Soufrière dome and crater basement. Our images suggest however that some non-conductive zones may be massive andesite bodies rather than argilized zones, and that these bodies may have deeper roots than hypothesized. [ABSTRACT FROM AUTHOR]

Published
2012
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19. The Mexico Earthquake of September 19, 1985—The Incident Wavefield in Mexico City during the Great Michoacán Earthquake and Its Interaction with the Deep Basin

Author

Campillo, M., Bard, P-Y., Nicollin, F., and Sánchez-Sesma, F.

Abstract

We used the vertical displacement records of the ground motion in Mexico City during the great 1985 Michoacan earthquake to identify the nature of the waves responsible for the heavy damage suffered by the town. The records at the different stations exhibit very similar waveshapes. A multichannel phase analysis shows the arrival, from the source zone, of a strong coherent wavetrain which represent the most of the energy incident at periods around 3 sec. We interpreted this arrival as the regional continental phase Lg. The study of other instrumental data in the period range relevant to the present investigation shows the efficiency of Lg propagation between the subduction zone and Mexico City.We have computed the response to Lg waves of a sedimentary basin whose characteristics correspond to the deep basin beneath Mexico City. The amplification reaches a value of about 5. The results obtained are in good agreement with the response of the basin to a single obliquely incident plane wave. The durations of the theoretical signals are similar to those of actual observations at sites in the hills zone and in the intermediate zone.

Published
1988
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20. Structural imaging and monitoring of volcanoes with cosmic muons

Author

Gibert, D., Jourde, K., Nolwenn Lesparre, C Komorowski, J., J Sibilla, J., Sirol, O., Marteau, J., Carlus, B., Gardien, S., Girerd, C., C Ianigro, J., L Montorio, J., Ars, Jean Bremond D., Kergosien, B., Le Gonidec, Y., Nicollin, F., Rolland, P., Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Institut de Physique Nucléaire de Lyon (IPNL), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

23. Observation of the Dynamics of Hydrothermal Activity in La Soufrière of Guadeloupe Volcano with Joint Muography, Gravimetry, Electrical Resistivity Tomography, Seismic and Temperature Monitoring

Author

Dominique Gibert, Jean Bremond d'Ars, Bruno Carlus, Sébastien Deroussi, Jean‐Christophe Ianigro, David E. Jessop, Kevin Jourde, Bruno Kergosien, Yves Le Gonidec, Nolwenn Lesparre, Jacques Marteau, Roberto Moretti, Florence Nicollin, Marina Rosas‐Carbajal, László Oláh, Hiroyuki K. M. Tanaka, Dezső Varga, Gibert, D., de Bremond d'Ars, J., Carlus, B., Deroussi, S., Ianigro, J. -C., Jessop, D. E., Jourde, K., Kergosien, B., Le Gonidec, Y., Lesparre, N., Marteau, J., Moretti, R., Nicollin, F., Rosas-Carbajal, M., Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique des 2 Infinis de Lyon (IP2I Lyon), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), CEA Grenoble, Université de Strasbourg (UNISTRA), László Oláh, Hiroyuki K. M, and Tanaka Dezső Varga

Subjects
Gravimetry, Fumerole temperature, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Geophysical method, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Electrical resistivity tomography, Seismic monitoring, Volcanic hydrothermal systems, Muon tomography
Abstract

International audience; Muography uses muons contained in the natural cosmic rays to determine the density of rock volumes. The measurements consist of counting the muons emerging from the target to determine the screening effect produced by the rock. Since the larger the rock thickness, the smaller the number of muons able to cross, the time resolution that can be achieved by muography to monitor density changes is on the order of one or two weeks for kilometer-sized volcanoes. This limitation of the method can be reduced by joining muography with high time-resolution measurements like passive seismic monitoring. In the case of structural imaging, muography benefits from the fact that muon trajectories are linear, making the tomography problem simpler than for other geophysical techniques like electrical resistivity tomography. Experiments performed on La Soufrière of Guadeloupe volcano are described to show how muography can be used to contribute to structural imaging of a highly heterogeneous lava dome and to detect abrupt transient hydrothermal phenomena likely to produce dangerous explosive events.

Published
2022
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24. Volcano electrical tomography unveils edifice collapse hazard linked to hydrothermal system structure and dynamics.

Author

Rosas-Carbajal M, Komorowski JC, Nicollin F, and Gibert D

Abstract

Catastrophic collapses of the flanks of stratovolcanoes constitute a major hazard threatening numerous lives in many countries. Although many such collapses occurred following the ascent of magma to the surface, many are not associated with magmatic reawakening but are triggered by a combination of forcing agents such as pore-fluid pressurization and/or mechanical weakening of the volcanic edifice often located above a low-strength detachment plane. The volume of altered rock available for collapse, the dynamics of the hydrothermal fluid reservoir and the geometry of incipient collapse failure planes are key parameters for edifice stability analysis and modelling that remain essentially hidden to current volcano monitoring techniques. Here we derive a high-resolution, three-dimensional electrical conductivity model of the La Soufrière de Guadeloupe volcano from extensive electrical tomography data. We identify several highly conductive regions in the lava dome that are associated to fluid saturated host-rock and preferential flow of highly acid hot fluids within the dome. We interpret this model together with the existing wealth of geological and geochemical data on the volcano to demonstrate the influence of the hydrothermal system dynamics on the hazards associated to collapse-prone altered volcanic edifices.

Published
2016
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25. Nonlinear synthesis of input signals in ultrasonic experimental setups.

Author

Conil F, Gibert D, and Nicollin F

Abstract

A method is proposed to find the digital input signals to enter in nonlinear acoustical systems (power amplifiers, transducers, etc.) in order to obtain desired arbitrary response signals. The searched input signals are found by performing a Monte Carlo search guided by a simulated annealing process applied to a hidden model with a small number of parameters. The physical system is actually used in the optimization procedure, in a real-time manner, so that no theoretical model of the system response is required. The main aspects of the algorithm are described and illustrated with several examples.

Published
2004
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