Sensitivity to lunar cycles prior to the 2007 eruption of Ruapehu volcano

A long-standing question in Earth Science is the extent to which seismic and volcanic activity can be regulated by tidal stresses, a repeatable and predictable external excitation induced by the Moon-Sun gravitational force. Fortnightly tides, a similar to 14-day amplitude modulation of the daily tidal stresses that is associated to lunar cycles, have been suggested to affect volcano dynamics. However, previous studies found contradictory results and remain mostly inconclusive. Here we study how fortnightly tides have affected Ruapehu volcano (New Zealand) from 2004 to 2016 by analysing the rolling correlation between lunar cycles and seismic amplitude recorded close to the crater. The long-term (similar to 1-year) correlation is found to increase significantly (up to confidence level of 5-sigma) during the similar to 3 months preceding the 2007 phreatic eruption of Ruapehu, thus revealing that the volcano is sensitive to fortnightly tides when it is prone to explode. We show through a mechanistic model that the real-time monitoring of seismic sensitivity to lunar cycles may help to detect the clogging of active volcanic vents, and thus to better forecast phreatic volcanic eruptions

Computational convergence of the path integral for real dendritic morphologies

Neurons are characterised by a morphological structure unique amongst biological cells, the core of which is the dendritic tree. The vast number of dendritic geometries, combined with heterogeneous properties of the cell membrane, continue to challenge scientists in predicting neuronal input-output relationships, even in the case of sub-threshold dendritic currents. The Green’s function obtained for a given dendritic geometry provides this functional relationship for passive or quasi-active dendrites and can be constructed by a sum-over-trips approach based on a path integral formalism. In this paper, we introduce a number of efficient algorithms for realisation of the sum-over-trips framework and investigate the convergence of these algorithms on different dendritic geometries. We demonstrate that the convergence of the trip sampling methods strongly depends on dendritic morphology as well as the biophysical properties of the cell membrane. For real morphologies, the number of trips to guarantee a small convergence error might become very large and strongly affect computational efficiency. As an alternative, we introduce a highly-efficient matrix method which can be applied to arbitrary branching structures

Officers and Directors of ASBMT

catalogue d'expositionNational audienceLa pratique des bains de mer est avérée à La Rochelle à partir des années 1770, dans le secteur de l'actuelle plage de la Concurrence. Mais les noyades ne sont pas rares et le corps de ville met en place, à terre et sur l'eau, un dispositif de secours aux noyés

Galileo: Le Partenariat Public-Prive a l'Epreuve du "Juste Retour". = The public-private partnership (PPP) put to the test of "fair return". Bruges Political Research Papers No. 11, February 2010

No abstract

MODELISATION NUMERIQUE DE L'INTERACTION SOL-STRUCTURE LORS DU PHENOMENE DE FONTIS

International audienceThis article focuses on the simulation of soil-structure interaction during a sinkhole development by the use of a coupling numerical modelling approach. The 2D model uses a Finite Difference computer code associated with a Distinct Elements code to optimize the performances of both softwares. This allows an important decrease of computation time and the results computed are close of the experimental observations made before

Experimental analysis of the impact of ground movements on surface structure

International audienceMan's activity frequently causes ground movements: the most notable examples of ground movements are provided by the mining industry in the form of subsidence. Consequently, mining subsidence can damage the surface structures. Many empirical approaches have been developed to predict structure damage using ground movements measured in greenfield conditions by assuming that the presence of a building has no effect on the settlement prediction. To improve our understanding of that effect and investigate the potential damage to the building, we have undertaken an experimental research program by means of a large three-dimensional physical model designed to simulate mining-induced ground movements. The results pointed out the effect of building structure on greenfield movements to be taken into account and enabled an analysis of the damage to the surface building, based on the existing damage estimation approaches.L'activité humaine cause fréquemment des mouvements de terrain. Les mouvements de terrain sous la forme d'affaissement sont induits par l'exploitation minière. Les affaissements miniers peuvent endommager les structures en surface. Des approches empiriques ont été développées pour prévoir les dommages au bâti en utilisant les caractéristiques des mouvements de terrain sans prendre en compte l'effet de la présence des constructions en surface. Afin d'étudier ces effets et d'investiguer les dommages potentiels sur le bâti, nous avons réalisé une étude expérimentale à l'aide d'un modèle réduit tridimensionnel de grandes dimensions permettant de simuler des mouvements de terrain dus aux mines. Les résultats expérimentaux montrent l'influence de la présence du bâti sur les mouvements du sol, qui doit être prise en compte dans l'estimation de dommage, et permettent d'apprécier la prévision des dégradations de la structure bâtie basée sur les méthodes existantes

Apport de la modélisation expérimentale et numérique à la compréhension du phénomène d'interaction et numérique sol-structure lors d'un fontis

International audienceThis article is focused on the study of soil-structure interaction during the occurrence of a sinkhole by the use of a small-scale experimental model and a coupled numerical approach. The experimental model uses a 2D analogical soil and a building model. Tests in greenfield conditions and with the building allow determining the soil-structure interaction phenomenon. Computer simulations are validated with the results from the ex-perimental tests in order to run parametrical studies in a further developmentCet article présente une étude de l'interaction sol-structure durant la formation d'un fontis à l'aide d'un modèle physique puis d'une modélisation numérique couplée. Le modèle réduit expérimental utilise un matériau ana-logique bidimensionnel et une maquette de structure. Des essais en terrain vierge puis en présence de la structure permettent de caractériser la nature de l'interaction sol-structure. Les simulations numériques sont validées sur les résultats des essais expérimentaux en vue de mener des études paramétriques ultérieure