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1. Chapter 13 Modelling Seismic Wave Propagation for Geophysical Imaging

Author

Tago, J., Cruz-Atienza, V., Chaljub, E., Brossier, R., Coutant, O., Garambois, S., Prieux, V., Operto, S., Mercerat, D., Virieux, J., and Ribodetti, A.

Subjects
seismic wave, geophysical imaging, Boundary value problem, Finite element method, Free surface, Frequency domain, Seismology, Time domain, Velocity, bic Book Industry Communication::P Mathematics & science::PD Science: general issues
Abstract

The Earth is an heterogeneous complex media from the mineral composition scale (10−6m) to the global scale ( 106m). The reconstruction of its structure is a quite challenging problem because sampling methodologies are mainly indirect as potential methods (Günther et al., 2006; Rücker et al., 2006), diffusive methods (Cognon, 1971; Druskin & Knizhnerman, 1988; Goldman & Stover, 1983; Hohmann, 1988; Kuo & Cho, 1980; Oristaglio & Hohmann, 1984) or propagation methods (Alterman & Karal, 1968; Bolt & Smith, 1976; Dablain, 1986; Kelly et al., 1976; Levander, 1988; Marfurt, 1984; Virieux, 1986). Seismic waves belong to the last category. We shall concentrate in this chapter on the forward problem which will be at the heart of any inverse problem for imaging the Earth. The forward problem is dedicated to the estimation of seismic wavefields when one knows the medium properties while the inverse problem is devoted to the estimation of medium properties from recorded seismic wavefields.

Published
2012
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3. Assessing the reliability of local earthquake tomography for crustal imaging: 30 years of records in the Western Alps as a case study

Author

Virieux, J, Paul, A, Langlais, M, Janex, G, Guéguen, P, Helmstetter, A, Stehly, L, Virieux, J, Paul, A, Langlais, M, Janex, G, Guéguen, P, Helmstetter, A, and Stehly, L

Abstract

Local earthquake tomography (LET) is a popular method for inverting arrival time picks of local-regional earthquakes for P- and S-wave velocity and hypocenter parameters in seismically active regions. This popularity is due to some robust and well-documented open-source codes that are sometimes used as black boxes. The availability of a very complete time-pick database on the Western Alps gives us a chance to thoroughly investigate the influence of the numerous processes and parameters involved when applying LET to the Western Alps or similar targets. From a subset of high-quality manual picks (1989-2014), we compute preliminary P and S velocity models that are used to predict arrival times for later events and allow the selected fusion of picks downloaded from different seismological agencies for a consistent 33-year database (1989-2021). Different model reconstructions are proposed by selecting different subsets of the arrival time dataset. Aside data input into the LET, influence of initial stratified or three-dimensional velocity models and related initial earthquake locations is investigated together with grid discretization, Laplacian smoothing and damping parameters in the standard penalty approach commonly used by LET codes. These numerical parameters account for the expected limited resolution of seismic waves due to their finite-frequency content. Parameter selection is handled by the user, whereas frequency impact is only implicit in the onset picks. The earthquake distribution allows a reconstruction down to 40-km depth over an area of ∼ 500x500 km2. Robust features such as the high-velocity Ivrea body anomaly, and a deep low-velocity anomaly associated with crustal thickening underneath the mountain belt survive whatever the tomography strategy and parameters. Finally, a comparison with previous LET reconstructions suggests that finite-frequency content be explicitly incorporated through wave equation tomography to improve spatial resolution. This would

Published
2023
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4. Assessing the reliability of local earthquake tomography for crustal imaging: 30 yr of records in the Western Alps as a case study.

Author

Virieux, J, Paul, A, Langlais, M, Janex, G, Guéguen, P, Helmstetter, A, and Stehly, L

Subjects
*EARTHQUAKES, *EARTHQUAKE zones, *SEISMIC waves, *TOMOGRAPHY, *SEISMIC event location, *SEISMIC tomography, *FEATURE selection, *PALEOSEISMOLOGY
Abstract

Local earthquake tomography (LET) is a popular method for inverting arrival time picks of local-regional earthquakes for P - and S -wave velocities and hypocentre parameters in seismically active regions. This popularity is due to some robust and well-documented open-source codes that are sometimes used as black boxes. The availability of a very complete time-pick database on the Western Alps gives us a chance to thoroughly investigate the influence of the numerous processes and parameters involved when applying LET to the Western Alps or similar targets. From a subset of high-quality manual picks (1989–2014), we compute preliminary P and S velocity models that are used to predict arrival times for later events and allow the selected fusion of picks downloaded from different seismological agencies for a consistent 33-yr database (1989–2021). Different model reconstructions are proposed by selecting different subsets of the arrival time data set. Aside data input into the LET, influence of initial stratified or 3-D velocity models and related initial earthquake locations is investigated together with grid discretization, Laplacian smoothing and damping parameters in the standard penalty approach commonly used by LET codes. These numerical parameters account for the expected limited resolution of seismic waves due to their finite-frequency content. Parameter selection is handled by the user, whereas frequency impact is only implicit in the onset picks. The earthquake distribution allows a reconstruction down to 40-km depth over an area of ∼500 × 500 km2. Robust features such as the high-velocity Ivrea body anomaly, and a deep low-velocity anomaly associated with crustal thickening underneath the mountain belt survive whatever the tomography strategy and parameters. Finally, a comparison with previous LET reconstructions suggests that finite-frequency content be explicitly incorporated through wave equation tomography to improve spatial resolution. This would fully exploit observables collected from seismograms, albeit with a significant increase in computer costs. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Slope tomography based on eikonal solvers and the adjoint-state method

Author

Tavakoli F., B., Operto, S., Ribodetti, A., Virieux, J., Géoazur (GEOAZUR 7329), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), Institut des Sciences de la Terre (ISTerre), 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-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])

Subjects
Mathematical optimization, Seismic tomography, 010504 meteorology & atmospheric sciences, Computer science, Geophysical imaging, Eikonal equation, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Inversion (meteorology), Solver, 010502 geochemistry & geophysics, System of linear equations, 01 natural sciences, Geophysics, Numerical modelling, Geochemistry and Petrology, Adjoint state method, Tomography, Inverse theory, Algorithm, 0105 earth and related environmental sciences
Abstract

International audience; Velocity macromodel building is a crucial step in the seismic imaging workflow as it provides the necessary background model for migration or full waveform inversion. In this study, we present a new formulation of stereotomography that can handle more efficiently long-offset acquisition, complex geological structures and large-scale data sets. Stereotomography is a slope tomographic method based upon a semi-automatic picking of local coherent events. Each local coherent event, characterized by its two-way traveltime and two slopes in common-shot and common-receiver gathers, is tied to a scatterer or a reflector segment in the subsurface. Ray tracing provides a natural forward engine to compute traveltime and slopes but can suffer from non-uniform ray sampling in presence of complex media and long-offset acquisitions. Moreover, most implementations of stereotomography explicitly build a sensitivity matrix, leading to the resolution of large systems of linear equations, which can be cumbersome when large-scale data sets are considered. Overcoming these issues comes with a new matrix-free formulation of stereotomography: a factored eikonal solver based on the fast sweeping method to compute first-arrival traveltimes and an adjoint-state formulation to compute the gradient of the misfit function. By solving eikonal equation from sources and receivers, we make the computational cost proportional to the number of sources and receivers while it is independent of picked events density in each shot and receiver gather. The model space involves the subsurface velocities and the scatterer coordinates, while the dips of the reflector segments are implicitly represented by the spatial support of the adjoint sources and are updated through the joint localization of nearby scatterers. We present an application on the complex Marmousi model for a towed-streamer acquisition and a realistic distribution of local events. We show that the estimated model, built without any prior knowledge of the velocities, provides a reliable initial model for frequency-domain FWI of long-offset data for a starting frequency of 4 Hz, although some artefacts at the reservoir level result from a deficit of illumination. This formulation of slope tomography provides a computationally efficient alternative to waveform inversion method such as reflection waveform inversion or differential-semblance optimization to build an initial model for pre-stack depth migration and conventional FWI.

Published
2017
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13. Transmission of light in deep sea water at the site of the Antares neutrino telescope

Author

Aguilar, JA, Albert, A, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, FE, Aslanides, E, Aubert, JJ, Azoulay, R, Bailey, D, Basa, S, Battaglieri, M, Becherini, Y, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, Bland, RW, de Botton, N, Boulesteix, J, Bouwhuis, MC, Brooks, CB, Bradbury, SM, Bruijn, R, Brunner, J, Bugeon, F, Burgio, GF, Cafagna, F, Calzas, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, SL, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compere, C, Croquette, J, Cooper, S, Coyle, P, Cuneo, S, Damy, G, van Dantzig, R, Deschamps, A, De Marzo, C, Destelle, JJ, De Vita, R, Dinkelspiler, B, Dispau, G, Drougou, JF, Druillole, F, Engelen, J, Favard, S, Feinstein, F, Ferry, S, Festy, D, Fopma, J, Fuda, JL, Gallone, JM, Giacomelli, G, Girard, N, Goret, P, Gournay, JF, Hallewell, G, Hartmann, B, Heijboer, A, Hello, Y, Hernandez-Rey, JJ, Herrouin, G, Hossl, J, Hoffmann, C, Hubbard, JR, Jaquet, M, de Jong, M, Jouvenot, F, Kappes, A, Karg, T, Karkar, S, Karolak, M, Katz, U, Keller, P, Kooijman, P, Korolkova, EV, Kouchner, A, Kretschmer, W, Kudryavtsev, VA, Lafoux, H, Lagier, P, Lamare, P, Languillat, JC, Laubler, L, Legou, T, Le Guen, Y, Le Provost, H, Le van Suu, A, Lo Nigro, L, Lo Presti, D, Loucatos, S, Louis, F, Lyashuk, V, Magnier, P, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Mazeas, F, Mazeau, B, Mazure, A, McMillan, JE, Michel, JL, Millot, C, Milovanovic, A, Montanet, F, Montaruli, T, Morel, JP, Moscoso, L, Nezri, E, Niess, V, Nooren, GJ, Ogden, P, Olivetto, C, Palanque-Delabrouille, N, Payre, P, Petta, C, Pineau, JP, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Randazzo, N, Real, D, van Rens, BAP, Rethore, F, Ripani, M, Roca-Blay, V, Romeyer, A, Rollin, JF, Romita, M, Rose, HJ, Rostovtsev, A, Ruppi, M, Russo, GV, Sacquin, Y, Saouter, S, Schuller, JP, Schuster, W, Sokalski, I, Suvorova, O, Spooner, NJC, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, LF, Tilav, S, Usik, A, Valdy, P, Vallage, B, Vaudaine, G, Vernin, P, Virieux, J, Vladimirsky, E, de Vries, G, Huberts, PD, de Wolf, E, Zaborov, D, Zaccone, H, Zakharov, V, Zavatarelli, S, de Zornoza, JD, Zuniga, J, Collaboration, ANTARES, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANTARES, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Aix Marseille Université (AMU), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), J.A. AGUILAR, A. ALBERT, P. AMRAM, M. ANGHINOLFI, G. ANTON, S. ANVAR, F.E. ARDELLIER-DESAGES, E. ASLANIDES, J-J. AUBERT, R. AZOULAY, D. BAILEY, S. BASA, M. BATTAGLIERI, Y. BECHERINI, R. BELLOTTI, J. BELTRAMELLI, V. BERTIN, M. BILLAULT, R. BLAES, F. BLANC, R.W. BLAND, N. DE BOTTON, J. BOULESTEIX, M.C. BOUWHUIS, C.B. BROOKS, S.M. BRADBURY, R. BRUIJN, J. BRUNNER, F. BUGEON, G.F. BURGIO, F. CAFAGNA, A. CALZAS, L. CAPONETTO, E. CARMONA, J. CARR, S.L. CARTWRIGHT, S. CECCHINI, P. CHARVIS, M. CIRCELLA, C. COLNARD, C. COMPE`RE, J. CROQUETTE, S. COOPER, P. COYLE, S. CUNEO, G. DAMY, R. VAN DANTZIG, A. DESCHAMPS, C. DE MARZO, J.-J. DESTELLE, R. DE VITA, B. DINKELSPILER, G. DISPAU, J.-F. DROUGOU, F. DRUILLOLE, J. ENGELEN, S. FAVARD, F. FEINSTEIN, S. FERRY, D. FESTY, J. FOPMA, J-L. FUDA, J.-M. GALLONE, G. GIACOMELLI, N. GIRARD, P. GORET, J.-F. GOURNAY, G. HALLEWELL, B. HARTMANN, A. HEIJBOER, Y. HELLO, J.J. HERNANDEZ-REY, G. HERROUIN, J. HOßL, C. HOFFMANN, J.R. HUBBARD, M. JAQUET, M. DE JONG, F. JOUVENOT, A. KAPPES, T. KARG, S. KARKAR, M. KAROLAK, U. KATZ, P. KELLER, P. KOOIJMAN, E.V. KOROLKOVA, A. KOUCHNER, W. KRETSCHMER, V.A. KUDRYAVTSEV, H. LAFOUX, P. LAGIER, P. LAMARE, J-C. LANGUILLAT, L. LAUBIER, T. LEGOU, L.GUEN, H. LE PROVOST, A. LE VAN SUU, L. LO NIGRO, D. LO PRESTI, S. LOUCATOS, F. LOUIS, V. LYASHUK, P. MAGNIER, M. MARCELIN, A. MARGIOTTA, C. MARON, A. MASSOL, F. MAZEAS, B. MAZEAU, A. MAZURE, J.E. MCMILLAN, J.-L. MICHEL, C. MILLOT, A. MILOVANOVIC, F. MONTANET, T. MONTARULI, J.-P. MOREL, L. MOSCOSO, E. NEZRI, V. NIESS, G.J. NOOREN, P. OGDEN, C. OLIVETTO, N. PALANQUE-DELABROUILLE, P. PAYRE, C. PETTA, J.-P. PINEAU, J. POINSIGNON, V. POPA, R. POTHEAU, T. PRADIER, C. RACCA, N. RANDAZZO, D. REAL, B.A.P. VAN RENS, F. RETHORE´, M. RIPANI, V. ROCA-BLAY, A. ROMEYER, J.-F. ROLLIN, M. ROMITA, H.J. ROSE, A. ROSTOVTSEV, M. RUPPI, G.V. RUSSO, Y. SACQUIN, S. SAOUTER, J.-P. SCHULLER, W. SCHUSTER, I. SOKALSKI, O. SUVOROVA, N.J.C. SPOONER, M. SPURIO, T. STOLARCZYK, D. STUBERT, M. TAIUTI, L.F. THOMPSON, S. TILAV, A. USIK, P. VALDY, B. VALLAGE, G. VAUDAINE, P. VERNIN, J. VIRIEUX, E. VLADIMIRSKY, G. DE VRIES, P. DE WITT HUBERTS, E. DE WOLF, D. ZABOROV, H. ZACCONE, V. ZAKHAROV, S. ZAVATARELLI, J.D. DE ZORNOZA, and J. ZUNIGA

Subjects
Photomultiplier, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Neutrino telescope, Lambda, 01 natural sciences, Light scattering, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Sea water properties: absorption and transmission of light, High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, Angular resolution, 07.89.+b, 29.40.Ka, 42.25.Bs, 42.68.Xy, 92.10.Bf, 92.10.Pt, 95.55.Vj, 010306 general physics, Cherenkov radiation, Physics, neutrino telescope, undersea Cherenkov detectors, sea water properties, absorption and transmission of light, Undersea Cherenkov detectors, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Scattering, Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, Attenuation length, Astronomy and Astrophysics, Scattering length, absorption and transmission of light, High Energy Physics - Phenomenology, 13. Climate action, Física nuclear, sea water properties
Abstract

The ANTARES neutrino telescope is a large photomultiplier array designed to detect neutrino-induced upward-going muons by their Cherenkov radiation. Understanding the absorption and scattering of light in the deep Mediterranean is fundamental to optimising the design and performance of the detector. This paper presents measurements of blue and UV light transmission at the ANTARES site taken between 1997 and 2000. The derived values for the scattering length and the angular distribution of particulate scattering were found to be highly correlated, and results are therefore presented in terms of an absorption length lambda_abs and an effective scattering length lambda_sct^eff. The values for blue (UV) light are found to be lambda_abs ~ 60(26) m, lambda_sct^eff ~ 265(122) m, with significant (15%) time variability. Finally, the results of ANTARES simulations showing the effect of these water properties on the anticipated performance of the detector are presented., Comment: 40 pages, 23 figures (including 4 available as separate figures), to be published in Astroparticle Physics

Published
2005
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16. An accurate discontinuous Galerkin method for solving point-source Eikonal equation in 2-D heterogeneous anisotropic media.

Author

Le Bouteiller, P., Benjemaa, M., Métivier, L., and Virieux, J.

Subjects
IMAGING systems in seismology, GALERKIN methods, EIKONAL equation, NONLINEAR differential equations, NUMERICAL analysis, GEOPHYSICS
Abstract

Accurate numerical computation of wave traveltimes in heterogeneous media is of major interest for a large range of applications in seismics, such as phase identification, data windowing, traveltime tomography and seismic imaging. A high level of precision is needed for traveltimes and their derivatives in applications which require quantities such as amplitude or take-off angle. Even more challenging is the anisotropic case, where the general Eikonal equation is a quartic in the derivatives of traveltimes. Despite their efficiency on Cartesian meshes, finite-difference solvers are inappropriate when dealing with unstructured meshes and irregular topographies. Moreover, reaching high orders of accuracy generally requires wide stencils and high additional computational load. To go beyond these limitations, we propose a discontinuous-finite-element-based strategy which has the following advantages: (1) the Hamiltonian formalism is general enough for handling the full anisotropic Eikonal equations; (2) the scheme is suitable for any desired high-order formulation or mixing of orders (p-adaptivity); (3) the solver is explicit whatever Hamiltonian is used (no need to find the roots of the quartic); (4) the use of unstructured meshes provides the flexibility for handling complex boundary geometries such as topographies (h-adaptivity) and radiation boundary conditions for mimicking an infinite medium. The point-source factorization principles are extended to this discontinuous Galerkin formulation. Extensive tests in smooth analytical media demonstrate the high accuracy of the method. Simulations in strongly heterogeneous media illustrate the solver robustness to realistic Earth-sciences-oriented applications. [ABSTRACT FROM AUTHOR]

Published
2018
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17. Which parameterization is suitable for acoustic vertical transverse isotropic full waveform inversion ? : Part 1. Sensitivity and trade-off analysis

Author

Gholami, Y., Brossier, R., Prieux, V., Operto, S., Ribodetti, A., Virieux, J., Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-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-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), 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
010504 meteorology & atmospheric sciences, Wave propagation, Computation, Acoustics, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Geochemistry and Petrology, ALGORITHME, CALIBRAGE, Wavenumber, Anisotropy, 0105 earth and related environmental sciences, Physics, PROSPECTION MAGNETIQUE, METHODE D'ANALYSE, PROPAGATION D'ONDE, Isotropy, SISMOGRAMME, MODELISATION, ONDE SISMIQUE, PROSPECTION ACOUSTIQUE, Transverse plane, Geophysics, Frequency domain, Acoustic approximation
Abstract

International audience; In most geologic environments, accounting for anisotropy is necessary to perform acoustic full waveform inversion (FWI) of wide-azimuth and wide-aperture seismic data because of the potential dependence of wave speeds on the direction of the wave propagation. In the framework of multiparameter FWI, the subsurface parameterization controls the influence of the different parameter classes on the modeled seismic data as a function of the scattering angle and hence the resolution with which the parameters can be reconstructed and the potential trade-off between different parameters. We have evaluated a numerical procedure based on computation of the scattering patterns of the different parameters to assess the sensitivity of the seismic data to different parameterizations of vertical transverse isotropic media in the acoustic approximation. Among the different categories we have tested, a monoparametric FWI was found for imaging one wave speed with a broad wavenumber content, keeping the Thomsen parameters fixed, which have a small influence on the data relative to the wave speed. This raises the question of the initial information required in the background models of the Thomsen parameters to perform reliable monoparameter FWI. Alternatively, simultaneously inverting the horizontal and vertical wave speeds introduces limited trade-off effects because these wave speeds have significant influence on the data for distinct ranges of scattering angles, while the influence of the Thomsen parameter δ remains weak. With such parameterization, the short-to-intermediate wavelengths of the vertical velocity are updated from the short-to-intermediate scattering angles, while the long-to-intermediate wavelengths of the horizontal velocity are updated from the wide-to-intermediate scattering angles. We concluded that the choice of the subsurface parameterization can be driven by the acquisition geometry, which controls the scattering-angle coverage and hence the resolving power of FWI, and by the accuracy of the available initial FWI models. Read More: http://library.seg.org/doi/abs/10.1190/geo2012-0204.1

Published
2013
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18. Joint ray plus Born least-squares migration and simulated annealing optimization for target-oriented quantitative seismic imaging

Author

Ribodetti, Alessandra, Operto, S., Agudelo, W., Collot, Jean-Yves, and Virieux, J.

Abstract

A seismic processing workflow based on iterative ray + Born migration/inversion and target-oriented postprocessing of the migrated image is developed for fine-scale quantitative characterization of reflectors. The first step of the workflow involves linear iterations of the ray + Born migration/inversion. The output of the first step is a true-amplitude migrated image parameterized by velocity perturbations. In a second step, postprocessing of the migrated image is performed through a random search with a very-fast simulated annealing (VFSA) algorithm. The forward problem of the global optimization is a simple convolutional model that linearly relates a vertical profile of the band-limited migrated image after depth-to-time conversion to a 1D velocity model composed of a stack of homogeneous layers of arbitrary velocity and thickness. The aim of the postprocessing is to eliminate the limited bandwidth effects of the source from the migrated image for resolution improvement and enhanced geological interpretation of selected targets. The global optimization approach allows for uncertainty analysis required by the intrinsic nonuniqueness of the velocity model output by the postprocessing. The relevance of the convolutional model when applied to the output of the ray + Born migrated inversion is first illustrated with a one-layer model. The accuracy and the robustness of the workflow to image geologically complicated models are then illustrated with an application to the synthetic Marmousi model. Some practical issues (e. g., the source wavelet estimate and the scaling of the migrated image required by the VFSA optimization) are discussed with an application to a 2D real seismic multichannel reflection data set collected in the Gulf of Guayaquil (Ecuador). The postprocessing is applied to derive the fine-scale velocity structure of a decollement zone on top of the subduction channel. The postprocessing allows for mapping structural variations along different segments of the decollement, which can be associated with changes in fluid content and porosity.

Published
2011

22. Seismic reflections reveal a massive melt layer feeding Campi Flegrei caldera

Author

Zollo, Aldo, Maercklin, Nils, Vassallo, Maurizio, Dello Iacono, Dario, Virieux, J., Gasparini, Paolo, Department of Physics, Università degli studi di Napoli Federico II-RISSC-Lab, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Zollo, Aldo, N., Maercklin, M., Vassallo, D., Dello Iacono, J., Virieux, and Gasparini, Paolo

Subjects
[SDU]Sciences of the Universe [physics], magma sill, seismic reflections, caldera
Abstract

International audience; Campi Flegrei is an active, resurgent caldera that is located a few kilometres west of the city of Naples, a densely populated urban settlement in southern Italy. Identifying, locating at depth and better defining the geometry of the magma feeding system of the caldera is highly relevant for assessing and monitoring its volcanic hazard. Based on a high resolution seismic reflection data set, we investigated the deep structure of the volcano. Here we show that seismic wave amplitude variations with distance from the radiating source provide clear evidence for large amplitude seismic reflections from the top of an extended supercritical fluid-bearing rock formation at about 3,000 m and of an about 7,500 m deep, 1,000 m thick, low velocity layer, which is associated with a mid-crust, partial melting zone beneath the caldera. The modeling of magma properties based on measured seismic velocities indicates a relatively high melt percentage (in the range 80–90%). These new data suggest that a large magmatic sill is present well within the basement formations, which is possibly linked to the surface through a system of deep fractures bordering the caldera. The lateral extension and similar depth of the melt zone observed beneath the nearby Mt.Vesuvius support the hypothesis of a single continuous magma reservoir feeding both of these volcanoes.

Published
2008
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23. Seismic hazard on the French Riviera : new data, interpretation and simulations

Author

Courboulex, F., Larroque, C., Deschamps, Anne, Kohrs-Sansorny, C., Gélis, C., Got, J.-L., Charreau, J., Stéphan, J.-F., Béthoux, N., Virieux, J., Brunel, D., Maron, C., Duval, A.-M., Perez, J.-L., Mondielli, P., Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), ERA 6 Risque sismique (ERA 6 Risque sismique - Equipe recherche associée au LCPC), Avant création Cerema, Direction environnement urbanisme et construction, Principauté de Monaco, Principauté de Monaco, Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Central des Ponts et Chaussées (LCPC)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), and Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, seismotectonics, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], earthquake location, strong ground motion, fault tectonics, microseismicity, earthquake-source mechanism
Abstract

International audience; We present here a detailed analysis of a seismic data set recorded by a dense seismological network installed over 6 months in the southeast of France. This experiment was set-up at the boundary between the Ligurian basin and the southern subalpine thrust belt (the Nice arc), which is a complex tectonic region that undergoes low to moderate seismicity. We recorded more than 500 microearthquakes, among which 348 occurred exactly in the centre of the network during a very active seismic sequence that lasted mainly over 2 months. We performed an absolute location of all of the events and calculated the magnitudes. Then we applied a cross-correlation technique to gather similar events and to relocate relatively few of them. This method revealed a very clear alignment of 19 events in a direction N120° oblique to the N20° general trend of seismicity. Focal mechanisms were determined for the four largest events and composite solutions for 32 smaller ones. Both the alignments of the earthquakes and the focal solutions revealed that two oblique segments of the fault were activated during the crisis. The main segment (8 km long) that was oriented NNE with a left-lateral strike slip movement is called the Blausasc fault. Taking into account the tectonic evolution and the relationships between surface structures and the distribution of earthquakes, and through a paleaoreconstruction of the tectonic evolution, we propose that the Blausasc fault is the hidden root of the Peille-Laghet fault, which has a mapped length of at least 15 km. The smaller segment (0.6 km long) that was activated during the crisis could be interpreted as an antithetic Riedel fracture. The active Blausasc fault is located in a densely populated zone, at only 10 km from the crowded cities of Monaco and Nice. It is thus particularly interesting to analyse it for hazard assessment. In the last section, we present a simulation that is aimed at predicting what the ground motion in the city of Nice would be like if an earthquake of magnitude 5.7 occurs on this fault. For this, we used the recordings of the largest event of the seismic sequence (Ml= 3.2) and an empirical Green's function summation scheme to simulate the ground motion at two stations situated in urban environments. The values obtained show that especially on soft soil sites, the effects of such an earthquake would be considerable in the city of Nice.

Published
2007
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25. Stress and fluid transfer in a fault zone due to overpressures in the seismogenic crust

Author

Cappa, F., Guglielmi, Y., Virieux, J., Earth Science Division [LBNL Berkeley] (ESD), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

International audience; Stress and fluid transfers were analyzed on the surface of a 30 m thick dextral strike-slip fault zone subjected to an overpressure of 63 kPa. Pressure-strain measurements taken during the pressurization indicated a strain state primarily controlled by the hydromechanical behavior of permeable fractures, and then, by the fluid diffusion in the matrix. Using THM modeling, we simulated an extension of these hydromechanical effects to a 25 km depth in the seismogenic crust, applying a lithostatic pressure at the base of the fault. The simulations indicate that a significant strain in the damage zone greater than that in the protolith, along with the differences in hydraulic diffusivity between the damage zone and protolith, may induce high static stress and fluid accumulations in the core. Under this stress, this core is projected to exhibit deformity—as much as a 12 m shear slip distributed over a 175 m long active zone.

Published
2007
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26. Slope tomography based on eikonal solvers and the adjoint-state method.

Author

F., B. Tavakoli, Operto, S., Ribodetti, A., and Virieux, J.

Subjects
IMAGING systems in seismology, TOMOGRAPHY, EIKONAL equation, RAY tracing, SEISMIC migration
Abstract

Velocity macromodel building is a crucial step in the seismic imaging workflow as it provides the necessary background model for migration or full waveform inversion. In this study, we present a new formulation of stereotomography that can handle more efficiently long-offset acquisition, complex geological structures and large-scale data sets. Stereotomography is a slope tomographic method based upon a semi-automatic picking of local coherent events. Each local coherent event, characterized by its two-way traveltime and two slopes in common-shot and common-receiver gathers, is tied to a scatterer or a reflector segment in the subsurface. Ray tracing provides a natural forward engine to compute traveltime and slopes but can suffer from non-uniform ray sampling in presence of complex media and long-offset acquisitions. Moreover, most implementations of stereotomography explicitly build a sensitivity matrix, leading to the resolution of large systems of linear equations, which can be cumbersome when large-scale data sets are considered. Overcoming these issues comes with a new matrix-free formulation of stereotomography: a factored eikonal solver based on the fast sweeping method to compute first-arrival traveltimes and an adjoint-state formulation to compute the gradient of the misfit function. By solving eikonal equation from sources and receivers, we make the computational cost proportional to the number of sources and receivers while it is independent of picked events density in each shot and receiver gather. The model space involves the subsurface velocities and the scatterer coordinates, while the dips of the reflector segments are implicitly represented by the spatial support of the adjoint sources and are updated through the joint localization of nearby scatterers. We present an application on the complex Marmousi model for a towed-streamer acquisition and a realistic distribution of local events. We show that the estimated model, built without any prior knowledge of the velocities, provides a reliable initial model for frequency-domain FWI of long-offset data for a starting frequency of 4 Hz, although some artefacts at the reservoir level result from a deficit of illumination. This formulation of slope tomography provides a computationally efficient alternative to waveform inversionmethod such as reflectionwaveforminversion or differential-semblance optimization to build an initial model for pre-stack depth migration and conventional FWI. [ABSTRACT FROM AUTHOR]

Published
2017
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27. Infrasound modeling in a spherical heterogeneous atmosphere

Author

Dessa, J.-X., Virieux, J., Lambotte, S., Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut de physique du globe de Strasbourg (IPGS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Ecole et Observatoire des sciences de la terre (EOST), Centre National de la Recherche Scientifique (CNRS)-Université Louis Pasteur - Strasbourg I-Institut national des sciences de l'Univers (INSU - CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

International audience; The deployment of a worldwide network for infrasound detection requires numerical methods for modeling these signals over long distances. A ray theoretical approach appears robust and efficient. It furthermore allows a straightforward interpretation of recorded phases. We have developed a three-dimensional Hamiltonian ray tracing for modeling linear acoustic waves in the atmosphere. Propagating over distances superior to 500 km requires the curvature of the Earth to be considered, which is achieved by using spherical coordinates. High atmospheric winds are properly handled through a modified Hamiltonian. These winds as well as sound velocity can change significantly during long-lasting propagations; these variations are also included in our modeling. Finally, the amplitude of infrasonic signals is computed by concomitantly solving for paraxial rays and assessing the evolution of the ray tube thus defined. We present the theory for this atmospheric infrasound modeling and some simple applications that establish its robustness and potential.

Published
2005
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28. Transmission of light in deep sea water at this site of the ANTARES neutrino telescope

Author

Aguilar, J A, Albert,A, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, F E, Aslanides, E, Aubert, Jean-Jacques, Azoulay, R, Bailey, D, Basa, S, Battaglieri, M, Becherini, Y, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, Bland, R W, De Botton, N R, Boulesteix, J, Bouwhuis, M C, Brooks, C B, Bradbury, S M, Bruijn, R, Brunner, J, Bugeon, F, Burgio, G F, Cafagna, F, Calzas, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, S L, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compère, C, Croquette, J, Cooper, S, Coyle, P, Cuneo, S, Damy, G, Van Dantzig, R, Deschamps, A, De Marzo, C, Destelle, J J, Vita, R De, Dinkelspiler, B, Dispau, G, Drougou, J F, Druillole, F, Engelen, J, Favard, S, Feinstein, F, Ferry, S, Festy, D, Fopma, J, Fuda, J L, Gallone, J M, Giacomelli, G, Girard, N, Goret, P, Gournay, J F, Hallewell, G D, Hartmann, B, Heijboer, A, Hello, Y, Hernàndez-Rey, J J, Herrouin, G, Hössle, J, Hoffmann, C, Hubbard, John R, Jaquet, M, Jong, M de, Jouvenot, F, Kappes, A, Karg, T, Karka, S, Karola, M, Katz, U, Keller, P, Kooijman, P, Korolkova, E V, Kouchner, A, Kretschmer, W, Kudryavtsev, V A, Lafoux, H, Lagier, P, Lamare, P, Languillat, J C, Laubier, L, Legou, T, Guen, Y Le, Le Provost, H, Van Suu, Le, Nigro, L Lo, Presti, D Lo, Loucatos, Sotirios S, Louis, F, Lyashuk, V, Magnier, P, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Mazéas, F, Mazeau, B, Mazure, A, McMillan, J E, Michel, J L, Millot, C, Milovanovic, A, Montanet, François, Montaruli, T, Morel, J P, Moscoso, L, Nezri, E, Niess, V, Nooren, G J, Ogden, P, Olivetto, C, Palanque-Delabrouille, Nathalie, Payre, P, Petta, C, Pineau, J P, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Randazzo, N, Real, D, Van Rens, B A P, Réthoré, F, Ripani, M, Roca-Blay, V, Romeyer, A, Rollin, J F, Romita, M, Rose, H J, Rostovtsev, A, Ruppi, M, Russo, G V, Sacquin, Yu, Saouter, S, Schuller, J P, Schuster, W, Sokalski, I A, Suvorova, O, Spooner, N J C, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, L F, Tilav, S, Usik, A, Valdy, P, Vallage, B, Vaudaine, G, Vernin, P, Virieux, J, Vladimirsky, E, Vries, G de, De Witt-Huberts, P K A, De Wolf, E, Zaborov, D, Zaccone, Henri, Zakharov, V, Zavatarelli, S, De Zornoza, J D, and Zúñiga, J

Subjects
Detectors and Experimental Techniques
Published
2004

29. Dynamic rupture simulation of nonplanar faults with a finite difference approach

Author

Cruz-Atienza, V.M., Virieux, J., Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU]Sciences of the Universe [physics], seismic rupture, boundary conditions, dynamic rupture, finite-difference modelling, non-planar faults, Physics::Geophysics, seismic source modelling
Abstract

Geophysical Journal International, v. 158, n. 3, p. 939-954, 2004. http://dx.doi.org/10.1111/j.1365-246X.2004.02291.x; International audience; Two-dimensional (2-D) modelling of dynamic seismic rupture is performed using a recent staggered-grid finite-difference formulation. Rupture boundary conditions are applied only inside the crack, without assuming any symmetry with respect to the rupture surface. By a simple rotation of the stress tensor, the local orientation of the crack is taken into consideration at each stress point. The grid size is controlled by the source discretization. The greater the number of grid nodes discretizing the finite source, the lower the grid size could be. Below the lower bound value associated with a given discretization, numerical artefacts are not negligible with respect to the spatial frequency content of the dynamic solution. Solutions converge for both point and finite sources by densifying the number of stress points in the source. Numerical scaling of boundary conditions is an important element of this convergence and allows the removal of high-frequency spurious effects of dynamic rupture conditions. For the self-similar crack, a comparison with Kostrov's analytical solution shows that accurate stress singularities are obtained for various crack orientations with respect to the numerical grid. For spontaneous rupture modelling assuming a slip-weakening constitutive law, similar solutions are found for both rupture kinematics and excited wavefield in planar faults with any orientation. Finally, based on these results, rupture propagation over an arbitrary non-planar fault is justified and then performed in the presence of heterogeneous medium.

Published
2004
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31. Adaptive wavelet-based finite-difference modelling of SH-wave propagation

Author

Operto, S., Virieux, J., Hustedt, B., Malfanti, F., Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), and Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

Geophysical Journal International, v. 148, n. 3, p. 476-498, 2002. http://dx.doi.org/10.1046/j.1365-246x.2002.01573.x; International audience

Published
2002
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34. Transmission of light in deep sea water at the site of the ANTARES neutrino telescope

Author

Aguilar, J A, Albert, A, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, F E, Aslanides, E, Aubert, J J, Azoulay, R, Bailey, D, Basa, S, Battaglieri, M, Becherini, Yvonne, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, Bland, R W, de Botton, N, Boulesteix, J, Bouwhuis, M C, Brooks, C B, Bradbury, S M, Bruijn, R, Brunner, J, Bugeon, F, Burgio, G F, Cafagna, F, Calzas, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, S L, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compere, C, Croquette, J, Cooper, S, Coyle, P, Cuneo, S, Damy, G, van Dantzig, R, Deschamps, A, De Marzo, C, Destelle, J J, De Vita, R, Dinkelspiler, B, Dispau, G, Drougou, J F, Druillole, F, Engelen, J, Favard, S, Feinstein, F, Ferry, S, Festy, D, Fopma, J, Fuda, J L, Gallone, J M, Giacomelli, G, Girard, N, Goret, P, Gournay, J F, Hallewell, G, Hartmann, B, Heijboer, A, Hello, Y, Hernandez-Rey, J J, Herrouin, G, Hossl, J, Hoffmann, C, Hubbard, J R, Jaquet, M, de Jong, M, Jouvenot, F, Kappes, A, Karg, T, Karkar, S, Karolak, M, Katz, U, Keller, P, Kooijman, P, Korolkova, E V, Kouchner, A, Kretschmer, W, Kudryavtsev, V A, Lafoux, H, Lagier, P, Lamare, P, Languillat, J C, Laubler, L, Legou, T, Le Guen, Y, Le Provost, H, Le van Suu, A, Lo Nigro, L, Lo Presti, D, Loucatos, S, Louis, F, Lyashuk, V, Magnier, P, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Mazeas, F, Mazeau, B, Mazure, A, McMillan, J E, Michel, J L, Millot, C, Milovanovic, A, Montanet, F, Montaruli, T, Morel, J P, Moscoso, L, Nezri, E, Niess, V, Nooren, G J, Ogden, P, Olivetto, C, Palanque-Delabrouille, N, Payre, P, Petta, C, Pineau, J P, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Randazzo, N, Real, D, van Rens, B A P, Rethore, F, Ripani, M, Roca-Blay, V, Romeyer, A, Rollin, J F, Romita, M, Rose, H J, Rostovtsev, A, Ruppi, M, Russo, G V, Sacquin, Y, Saouter, S, Schuller, J P, Schuster, W, Sokalski, I, Suvorova, O, Spooner, N J C, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, L F, Tilav, S, Usik, A, Valdy, P, Vallage, B, Vaudaine, G, Vernin, P, Virieux, J, Vladimirsky, E, de Vries, G, Huberts, P D, de Wolf, E, Zaborov, D, Zaccone, H, Zakharov, V, Zavatarelli, S, de Zornoza, J D, Zuniga, J, Aguilar, J A, Albert, A, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, F E, Aslanides, E, Aubert, J J, Azoulay, R, Bailey, D, Basa, S, Battaglieri, M, Becherini, Yvonne, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, Bland, R W, de Botton, N, Boulesteix, J, Bouwhuis, M C, Brooks, C B, Bradbury, S M, Bruijn, R, Brunner, J, Bugeon, F, Burgio, G F, Cafagna, F, Calzas, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, S L, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compere, C, Croquette, J, Cooper, S, Coyle, P, Cuneo, S, Damy, G, van Dantzig, R, Deschamps, A, De Marzo, C, Destelle, J J, De Vita, R, Dinkelspiler, B, Dispau, G, Drougou, J F, Druillole, F, Engelen, J, Favard, S, Feinstein, F, Ferry, S, Festy, D, Fopma, J, Fuda, J L, Gallone, J M, Giacomelli, G, Girard, N, Goret, P, Gournay, J F, Hallewell, G, Hartmann, B, Heijboer, A, Hello, Y, Hernandez-Rey, J J, Herrouin, G, Hossl, J, Hoffmann, C, Hubbard, J R, Jaquet, M, de Jong, M, Jouvenot, F, Kappes, A, Karg, T, Karkar, S, Karolak, M, Katz, U, Keller, P, Kooijman, P, Korolkova, E V, Kouchner, A, Kretschmer, W, Kudryavtsev, V A, Lafoux, H, Lagier, P, Lamare, P, Languillat, J C, Laubler, L, Legou, T, Le Guen, Y, Le Provost, H, Le van Suu, A, Lo Nigro, L, Lo Presti, D, Loucatos, S, Louis, F, Lyashuk, V, Magnier, P, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Mazeas, F, Mazeau, B, Mazure, A, McMillan, J E, Michel, J L, Millot, C, Milovanovic, A, Montanet, F, Montaruli, T, Morel, J P, Moscoso, L, Nezri, E, Niess, V, Nooren, G J, Ogden, P, Olivetto, C, Palanque-Delabrouille, N, Payre, P, Petta, C, Pineau, J P, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Randazzo, N, Real, D, van Rens, B A P, Rethore, F, Ripani, M, Roca-Blay, V, Romeyer, A, Rollin, J F, Romita, M, Rose, H J, Rostovtsev, A, Ruppi, M, Russo, G V, Sacquin, Y, Saouter, S, Schuller, J P, Schuster, W, Sokalski, I, Suvorova, O, Spooner, N J C, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, L F, Tilav, S, Usik, A, Valdy, P, Vallage, B, Vaudaine, G, Vernin, P, Virieux, J, Vladimirsky, E, de Vries, G, Huberts, P D, de Wolf, E, Zaborov, D, Zaccone, H, Zakharov, V, Zavatarelli, S, de Zornoza, J D, and Zuniga, J

Abstract

The ANTARES neutrino telescope is a large photomultiplier array designed to detect neutrino-induced upward-going muons by their Cherenkov radiation. Understanding the absorption and scattering of light in the deep Mediterranean is fundamental to optimising the design and performance of the detector. This paper presents measurements of blue and UV light transmission at the ANTARES site taken between 1997 and 2000. The derived values for the scattering length and the angular distribution of particulate scattering were found to be highly correlated, and results are therefore presented in terms of an absorption length;,ab, and an effective scattering length lambda(sct)(eff). The values for blue (UV) light are found to be lambda(abs) similar or equal to 60(26) m, lambda(sct)(eff similar or equal to) 265(122) m, with significant (similar to15%) time variability. Finally, the results of ANTARES simulations showing the effect of these water properties on the anticipated performance of the detector are presented. (C) 2004 Elsevier B.V. All rights reserved.

Published
2005
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35. Study of large hemispherical photomultiplier tubes for the ANTARES neutrino telescope

Author

Aguilar, J A, Albert, A, Ameli, F, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, F E, Aslanides, E, Aubert, J J, Bailey, D, Basa, S, Battaglieri, M, Becherini, Yvonne, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, de Botton, N, Boulesteix, J, Bouwhuis, M C, Brooks, C B, Bradbury, S M, Bruijn, R, Brunner, J, Burgio, G F, Cafagna, F, Calzas, A, Capone, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, S L, Castorina, E, Cavasinni, V, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compere, C, Coniglione, R, Cooper, S, Coyle, P, Cuneo, S, Damy, G, van Dantzig, R, Deschamps, A, De Marzo, C, Denans, D, Destelle, J J, De Vita, R, Dinkelspiler, B, Distefano, C, Drogou, J F, Druillole, F, Engelen, J, Ernenwein, J P, Falchini, E, Favard, S, Feinstein, F, Ferry, S, Festy, D, Flaminio, V, Fopma, J, Fuda, J L, Gallone, J M, Giacomelli, G, Girard, N, Goret, P, Graf, K, Hallewell, G, Hartmann, B, Heijboer, A, Hello, Y, Hernandez-Rey, J J, Herrouin, G, Hossl, J, Hoffmann, C, Hubbard, J R, Jaquet, M, de Jong, M, Jouvenot, F, Kappes, A, Karg, T, Karkar, S, Karolak, M, Katz, U, Keller, P, Kooijman, P, Korolkova, E V, Kouchner, A, Kretschmer, W, Kuch, S, Kudryavtsev, V A, Lafoux, H, Lagier, P, Lahmann, R, Lamare, P, Languillat, J C, Laschinsky, H, Laubier, L, Legou, T, Le Guen, Y, Le Provost, H, Van Suu, A L, Lo Nigro, L, Lo Presti, D, Loucatos, S, Louis, F, Lyashuk, V, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Masullo, R, Mazeas, F, Mazure, A, McMillan, J E, Migneco, E, Millot, C, Milovanovic, A, Montanet, F, Montaruli, T, Morel, J P, Morganti, M, Moscoso, L, Musumeci, M, Naumann, C, Naumann-Godo, M, Nezri, E, Niess, V, Nooren, G J, Ogden, P, Olivetto, C, Palanque-Delabrouille, N, Papaleo, R, Payre, P, Petta, C, Piattelli, P, Pineau, J P, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Raia, G, Randazzo, N, Real, D, van Rens, B A P, Rethore, F, Riccobene, G, Rigaud, V, Ripani, M, Roca-Blay, V, Rolin, J F, Romita, M, Rose, H J, Rostovtsev, A, Ruppi, M, Russo, G V, Sacquin, Y, Salesa, F, Salomon, K, Saouter, S, Sapienza, P, Shanidze, R, Schuller, J P, Schuster, W, Sokalski, I, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, L F, Tilav, S, Valdy, P, Valente, V, Vallage, B, Vernin, P, Virieux, J, de Vries, G, Huberts, P D, de Wolf, E, Zaborov, D, Zaccone, H, Zakharov, V, Zornoza, J D, Zuniga, J, Aguilar, J A, Albert, A, Ameli, F, Amram, P, Anghinolfi, M, Anton, G, Anvar, S, Ardellier-Desages, F E, Aslanides, E, Aubert, J J, Bailey, D, Basa, S, Battaglieri, M, Becherini, Yvonne, Bellotti, R, Beltramelli, J, Bertin, V, Billault, M, Blaes, R, Blanc, F, de Botton, N, Boulesteix, J, Bouwhuis, M C, Brooks, C B, Bradbury, S M, Bruijn, R, Brunner, J, Burgio, G F, Cafagna, F, Calzas, A, Capone, A, Caponetto, L, Carmona, E, Carr, J, Cartwright, S L, Castorina, E, Cavasinni, V, Cecchini, S, Charvis, P, Circella, M, Colnard, C, Compere, C, Coniglione, R, Cooper, S, Coyle, P, Cuneo, S, Damy, G, van Dantzig, R, Deschamps, A, De Marzo, C, Denans, D, Destelle, J J, De Vita, R, Dinkelspiler, B, Distefano, C, Drogou, J F, Druillole, F, Engelen, J, Ernenwein, J P, Falchini, E, Favard, S, Feinstein, F, Ferry, S, Festy, D, Flaminio, V, Fopma, J, Fuda, J L, Gallone, J M, Giacomelli, G, Girard, N, Goret, P, Graf, K, Hallewell, G, Hartmann, B, Heijboer, A, Hello, Y, Hernandez-Rey, J J, Herrouin, G, Hossl, J, Hoffmann, C, Hubbard, J R, Jaquet, M, de Jong, M, Jouvenot, F, Kappes, A, Karg, T, Karkar, S, Karolak, M, Katz, U, Keller, P, Kooijman, P, Korolkova, E V, Kouchner, A, Kretschmer, W, Kuch, S, Kudryavtsev, V A, Lafoux, H, Lagier, P, Lahmann, R, Lamare, P, Languillat, J C, Laschinsky, H, Laubier, L, Legou, T, Le Guen, Y, Le Provost, H, Van Suu, A L, Lo Nigro, L, Lo Presti, D, Loucatos, S, Louis, F, Lyashuk, V, Marcelin, M, Margiotta, A, Maron, C, Massol, A, Masullo, R, Mazeas, F, Mazure, A, McMillan, J E, Migneco, E, Millot, C, Milovanovic, A, Montanet, F, Montaruli, T, Morel, J P, Morganti, M, Moscoso, L, Musumeci, M, Naumann, C, Naumann-Godo, M, Nezri, E, Niess, V, Nooren, G J, Ogden, P, Olivetto, C, Palanque-Delabrouille, N, Papaleo, R, Payre, P, Petta, C, Piattelli, P, Pineau, J P, Poinsignon, J, Popa, V, Potheau, R, Pradier, T, Racca, C, Raia, G, Randazzo, N, Real, D, van Rens, B A P, Rethore, F, Riccobene, G, Rigaud, V, Ripani, M, Roca-Blay, V, Rolin, J F, Romita, M, Rose, H J, Rostovtsev, A, Ruppi, M, Russo, G V, Sacquin, Y, Salesa, F, Salomon, K, Saouter, S, Sapienza, P, Shanidze, R, Schuller, J P, Schuster, W, Sokalski, I, Spurio, M, Stolarczyk, T, Stubert, D, Taiuti, M, Thompson, L F, Tilav, S, Valdy, P, Valente, V, Vallage, B, Vernin, P, Virieux, J, de Vries, G, Huberts, P D, de Wolf, E, Zaborov, D, Zaccone, H, Zakharov, V, Zornoza, J D, and Zuniga, J

Abstract

The ANTARES neutrino telescope, to be immersed depth in the Mediterranean Sea, will consist of a three-dimensional matrix of 900 large area photomultiplier tubes housed in pressure-resistant glass spheres. The selection of the optimal photomultiplier was a critical step for the project and required an intensive phase of tests and developments carried out in close collaboration with the main manufacturers worldwide. This paper provides an overview of the tests performed by the collaboration and describes in detail the features of the photomultiplier tube chosen for ANTARES. (c) 2005 Elsevier B.V. All rights reserved.

Published
2005
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38. Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano

Author

Auger, E, Virieux, J, Zollo, A, Auger, E, Virieux, J, and Zollo, A

Abstract

In this paper, we show how the migration of active seismic data can be used to identify and position a seismic discontinuity in a complex medium, and how the amplitude variations of the converted P to S waves can be interpreted to constrain the seismic velocities below the interface. For the application we turn our attention on Mt Vesuvius, an active volcano threatening a densely populated area. To better define its plumbing system, we investigate a mid-crust seismic discontinuity first identified by Zollo et al. (1996, Science, 274, 592-594) and assumed to be the top of a layer containing low-velocity material. We deduce a reference velocity model from previous works on first arrival times, and use it to migrate PP reflected and PS converted waves. In the migration image, the interface extends at least 20 000 m NE and 20 000 m SW of the volcano, at the depth of 8000 m, and with a mean dip less than 3 per cent. The migration of finite-difference synthetics exclude the fact that the migrated phases interpreted as 8000 m deep reflections or conversions might be multiples in the shallow layers. The PS and first arrival amplitudes are compared at a fixed station and for all the shots to determine the variations of the P-to-S conversion coefficient with the angle of incidence. It appears to vary very slowly over the whole range of incidence angle at disposal (50degrees-80degrees). This implies a dramatic drop of S-wave velocity from approximately 3600 m s(-1) above to less than 1000 m s(-1) below the interface. The smoothness of the variations indicate that the P-wave velocity also diminishes across the interface. The very low S-wave velocity, other geophysical observations at Vesuvius and in other volcanic systems, lead to the conclusion that below the 8000 m discontinuity there is a very extended layer of hot, partially molten material.

Published
2003
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40. Crustal structure deduced from receiver functions via single-scattering migration

Author

Bertrand, E, Deschamps, A, Virieux, J, Bertrand, E, Deschamps, A, and Virieux, J

Abstract

An investigation of the teleseismic P -wave coda is performed using the single-scattering approximation. The method allows one to image short-wavelength scale (less than or equal to2 km) velocity and density heterogeneities and structures that are barely detected by traveltime tomography. Source effects are removed by using receiver functions for data interpretation, but the amplitude (especially the sign of the signal) is synthesized. Both broad-band seismological stations in the southwestern Alps (France) and Campanian plain (Italy) are used for the illustration of the proposed method. Because of the large aperture of our arrays, laterally small-scale heterogeneities are difficult to image and we must assume lateral continuity of the detectable structure. If so, we show that this depth migration based on a single-scattering approach can recover both the depth and the geometry of the main discontinuities below the studied areas. In the southwestern Alps, we underline a complex crustal structure and Moho dipping topography. The Moho depth increases from 20 to 30 km between the coastline and the Mercantour range. In the Campanian plain (surrounding Mount Vesuvius) we also find a southeastwards-dipping Moho. Furthermore, the three main discontinuities are imaged, showing a relatively shallow mantle-crust discontinuity and a deeper one near the coastline.

Published
2002
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46. Asymptotic viscoacoustic diffraction tomography of ultrasonic laboratory data: a tool for rock properties analysis

Author

Ribodetti, A, Operto, S, Virieux, J, Lambare, G, Valero, Hp, Gibert, D, Ribodetti, A, Operto, S, Virieux, J, Lambare, G, Valero, Hp, and Gibert, D

Abstract

This paper presents an application of 2.5-D asymptotic viscoacoustic diffraction tomography to ultrasonic data recorded during a physically scaled laboratory experiment. This scaled experiment was used to test the reliability of our method when applied to a real data set to estimate the attenuation factor Q. Diffraction tomography relies on ray theory to compute the Green functions in a smooth background medium and on the Born approximation to linearize the relation between the scattered wavefield and the velocity and Q perturbations. The perturbations are inferred from the data by an iterative (linear) quasi-Newtonian algorithm. The inversion formula was specifically developed to account for the acquisition geometry designed in this study. The derivation of the Hessian operator shows that, for this acquisition, the velocity and Q perturbations are theoretically decoupled. The processing of the data was split into two steps: first, we applied the tomography to the data without deconvolving them. Second, we designed a post-processing procedure for the tomographic images to remove the source signature and to estimate the absolute Values of the velocity and the attenuation factor Q. At the conclusion of the first step, both the velocity and the Q tomographic images allowed one to delineate the gross contour of the target. We obtained an excellent match between the observed data and the viscoacoustic ray-Born synthetics. The match obtained with the viscoacoustic rheology was significantly better than for a purely acoustic one. In the second step, the post-processing allowed us to recover the shape of the target. We estimated the absolute values of the velocity and Q, although we had no quality control with regard to these results (the rheological properties of the material used in this study were unknown). The results suggest that the uncertainty of the velocity measurement is lower than that for Q. The application presented in this study suggests that the procedure tha

Published
2000
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48. Seismic hazard on the French Riviera: observations, interpretations and simulations

Author

Courboulex, F., primary, Larroque, C., additional, Deschamps, A., additional, Kohrs-Sansorny, C., additional, Gélis, C., additional, Got, J. L., additional, Charreau, J., additional, Stéphan, J. F., additional, Béthoux, N., additional, Virieux, J., additional, Brunel, D., additional, Maron, C., additional, Duval, A. M., additional, Perez, J-L., additional, and Mondielli, P., additional

Published
2007
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