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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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5. 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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12. The RESOLVE project: a multi-physics experiment with a temporary dense seismic array on the Argenti\'ere Glacier, French Alps

Author

Gimbert, Florent, Nanni, Ugo, Roux, Philippe, Helmstetter, A., Garambois, S., Lecointre, A., Walpersdorf, A., Jourdain, B., Langlais, M., Laarman, O., Lindner, F., Sergeant, A., Vincent, C., Walter, F., Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Grenoble Alpes (UGA)-Université Gustave Eiffel-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), 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 Gustave Eiffel-Université Grenoble Alpes (UGA), ANR-18-CE01-0015,SAUSSURE,Glissement des glaciers et pression hydrologique sous glaciaire en relat(2018), and ANR-17-CE01-0008,SEISMORIV,Instrumentation sismologique des rivières: un nouveau moyen de quantifier le role des evenements climatiques extremes sur la dynamique des rivières(2017)

Subjects
Physics - Geophysics, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology
Abstract

Recent work in the field of cryo-seismology demonstrates that high frequency (>1 Hz) waves provide key constraints on a wide range of glacier processes such as basal friction, surface crevassing or subglacial water flow. Establishing quantitative links between the seismic signal and the processes of interest however requires detailed characterization of the wavefield, which at the high frequencies of interest necessitates the deployment of large and particularly dense seismic arrays. Although dense seismic array monitoring has recently become routine in geophysics, its application to glaciated environments has yet remained limited. Here we present a dense seismic array experiment made of 98 3-component seismic stations continuously recording during 35 days in early spring on the Argenti\`ere Glacier, French Alps. The seismic dataset is supplemented by a wide range of complementary observations obtained from ground penetrating radar, drone imagery, GNSS positioning and in-situ instrumentation of basal glacier sliding velocities and subglacial water discharge. Through applying multiple processing techniques including event detection from template matching and systematic beamforming, we demonstrate that the present dataset provides enhanced spatial resolution on basal stick slip and englacial fracturing sources as well as novel constraints on heterogeneous nature of the noise field generated by subglacial water flow and on the link between crevasse properties and englacial seismic velocities. We finally outline in which ways further work using this dataset could help tackle key remaining questions in the field., Comment: Submitted to Seismological Research Letters on August 11th 2020

Published
2020

22. Vignoid, a plant-pathogen model to highlight the interactions between plant growth, powdery mildew, crop management and climate. A sensitivity analysis

Author

Calonnec, Agnes, Burie, Jean-Baptiste, Langlais, M., Mammeri, Y., Bruchou, C., Santé et agroécologie du vignoble (UMR SAVE), Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB)-Institut des Sciences de la Vigne et du Vin (ISVV)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Institut de Mécanique et d'Ingénierie de Bordeaux (I2M), École Nationale Supérieure d'Arts et Métiers (ENSAM), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Institut Polytechnique de Bordeaux-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut National de la Recherche Agronomique (INRA), Laboratoire de Mathématiques Fondamentale et Appliquée, Partenaires INRAE, Biostatistique et Processus Spatiaux (BioSP), and Institut National de la Recherche Agronomique (INRA)

Subjects
[SDV]Life Sciences [q-bio], [SDE]Environmental Sciences, [SDV.IDA]Life Sciences [q-bio]/Food engineering, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, ComputingMilieux_MISCELLANEOUS
Abstract

National audience

Published
2018

26. L’art de la grotte de la Mairie (Teyjat, Dordogne) dans son contexte magdalénien

Author

Paillet, P., Man-Estier, E., Boudadi-Maligne, M., Dandurand, G., Genty, D., Konik, S., Véronique Laroulandie, B Mallye, J., Langlais, M., Histoire naturelle de l'Homme préhistorique (HNHP), and Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

29. Impacts of plant growth and architecture on pathogen processes and consequences for the epidemic behaviour

Author

Agnes Calonnec, Burie, J. B., Langlais, M., Sébastien Guyader, Sébastien Saint-Jean, Ivan Sache, Bernard Tivoli, Santé Végétale (SV), Institut National de la Recherche Agronomique (INRA)-École Nationale d'Ingénieurs des Travaux Agricoles - Bordeaux (ENITAB), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche en Santé Végétale (INRA/ENITA) (UMR SAVE), Institut National de la Recherche Agronomique (INRA)-École Nationale d'Ingénieurs des Travaux Agricoles - Bordeaux (ENITAB)-Institut des Sciences de la Vigne et du Vin (ISVV), Agrosystèmes tropicaux (ASTRO), Institut National de la Recherche Agronomique (INRA), Environnement et Grandes Cultures (EGC), AgroParisTech-Institut National de la Recherche Agronomique (INRA), BIOlogie et GEstion des Risques en agriculture (BIOGER), Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Institut National de la Recherche Agronomique (INRA)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-AGROCAMPUS OUEST, Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche en Santé Végétale (INRA/ENITA) (UMRSV), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Institut National de la Recherche Agronomique (INRA)-Université de Rennes (UR)-AGROCAMPUS OUEST, and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)

Subjects
[SDV.SA]Life Sciences [q-bio]/Agricultural sciences, Canopy structure, Disease transmission, Architectural traits, Micro-climate, Host-pathogen models
Abstract

KEYNOTEKEYNOTE; Epidemics are dynamical processes with variable rates of disease progress. How much of these changes in disease rate are triggered by the host population is still a pending issue. An epidemic is driven by its effective reproduction number: the product between the proportion of susceptible tissue, the rate of disease transmission, and the duration of the infectious period. Then, any modification in the host population, either quantitative or qualitative (distribution of plants or of susceptible organs) may have an impact on the epidemic dynamics. The growth of the host population is modified by architectural features or by cultural or agronomical practices. The production of new organs continuously modifies the porosity of the plant or of the canopy and its level of susceptibility if organ susceptibility changes with age (ontogenic resistance). Indirectly, plant growth modifies the micro-climatic environment inside the canopy, generating favourable or unfavourable conditions for pathogens. The organ susceptibility, or their susceptibility period, may also be modified by cultural practices disrupting the crop-pathogen synchronisation. These variations within host populations do impact disease incidence, severity or spread. However, they have rarely been explicitly taken into account in epidemiological models. Tracking back from the global dynamics of an epidemic the pathogen processes that are impacted and ranking the host traits involved in their modifications represents a challenge. In this paper, we will 1) review evidence of epidemic variations attributed to plant growth and architecture in main pathosystems, 2) list the pathogen processes impacted, and give some clue to identify and assess them in different epidemic contexts and 3) explore models able to measure and predict the effect of plant growth and architecture on epidemics.

Published
2012

30. Coherence between geodetic and seismic deformation in a context of slow tectonic activity (SW Alps, France)

Author

Walpersdorf, A., primary, Sue, C., additional, Baize, S., additional, Cotte, N., additional, Bascou, P., additional, Beauval, C., additional, Collard, P., additional, Daniel, G., additional, Dyer, H., additional, Grasso, J.-R., additional, Hautecoeur, O., additional, Helmstetter, A., additional, Hok, S., additional, Langlais, M., additional, Menard, G., additional, Mousavi, Z., additional, Ponton, F., additional, Rizza, M., additional, Rolland, L., additional, Souami, D., additional, Thirard, L., additional, Vaudey, P., additional, Voisin, C., additional, and Martinod, J., additional

Published
2015
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31. Bluetongue spread and vaccination strategies in cattle herd

Author

Charron, Maud, Langlais, M, SEEGERS, HENRI, Ezanno, Pauline, ProdInra, Migration, UMR1300 Bio-agression, Epidémiologie et Analyse de Risque, Institut National de la Recherche Agronomique (INRA)-ENVN, and Inconnu

Subjects
[SDV] Life Sciences [q-bio], [SDV]Life Sciences [q-bio]
Published
2009

32. A reaction-diffusion system on noncoincident spatial domains modeling the circulation of a disease between two host populations

Author

Fitzgibbon, W. E., Langlais, M., and Morgan, J. J.

Subjects
35K57, Applied Mathematics, 92D30, 35K50, Analysis
Abstract

We study the global existence and long-time behavior of the solutions to a special reaction-diffusion system arising in mathematical population dynamics, with kinetics occurring on distinct spatial domains. First, we give a comprehensive description of the dynamics of the solutions of the underlying system of ordinary differential equations. Next, we analyze a simpler problem where the spatial domain is the same for all the partial differential equations. Last, we prove global existence for the original problem; we offer a conjecture concerning the large-time behavior of solutions and give some hints on its derivation and proof.

Published
2004

35. Existence of solutions for reaction-diffusion systems with $L^1$ data

Author

Bendahmane, M., Langlais, M., and Saad, M.

Subjects
35K57, Applied Mathematics, 92D30, Quantitative Biology::Populations and Evolution, 35D05, 35K50, Analysis
Abstract

We are concerned with a system of nonlinear partial differential equations modeling the spread of an epidemic disease through a heterogeneous habitat. Assuming no-flux boundary conditions and $L^1$ data, we prove the existence of at least one weak solution.

Published
2002

36. Effects of the feline panleukemia virus on feral cat populations on islands

Author

Berthier, K., Langlais, M., Auger, P., Pontier, D., Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), Ecoépidémiologie évolutionniste, Département écologie évolutive [LBBE], Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE)

Subjects
[SDV.OT]Life Sciences [q-bio]/Other [q-bio.OT]
Published
2000

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