Observational Evidence And Modelling Of An Internal Hydraulic Jump At The Atmospheric Boundary-Layer Top During A Tramontane Event     

Philippe Drobinski  Cyrille Flamant  Jan Dusek  Pierre H. Flamant  Jacques Pelon 《Boundary-Layer Meteorology》2001,98(3):497-515

A hydraulic jump has been observed with the airborne backscatter lidar LEANDRE 1 (Lidar embarqué pour l'Etude des Aérosols, des Nuages, des interactions Dynamique-Rayonnement etdu cycle de l'Eau) at the top of the atmospheric boundary layer (ABL) during a Tramontane event in the framework of the Pyréneés experiment. An analytical fluid mechanics model is used to interpret lidar observations in connection with in situ measurements andto study the sensitivity of the hydraulic jump triggering to the boundary conditions. This model, which generalizes the reduced-gravity shallow-water theory for two-dimensional stratified flows over a topograpy, is diagnostic (i.e., the reduced gravity g' = g _{v v} is prescribed) and uses boundary conditions defined in terms of Riemann invariants. Using inflow and outflow boundary conditions as well as the reduced gravity prescribed from in situ measurements, the model is able to diagnose the presence of a hydraulic jump at the location suspected from the lidar observations. The wind speed, ABL height and Froude number derived from the model are in good agreement with the observations (within about 20–30%).  相似文献   

Extraction of water and solutes from argillaceous rocks for geochemical characterisation: Methods, processes and current understanding     

Elisa Sacchi  Jean-Luc Michelot  Helmut Pitsch  Philippe Lalieux  Jean-François Aranyossy 《Hydrogeology Journal》2001,9(1):17-33

This paper summarises the results of a comprehensive critical review, initiated by the OECD/NEA "Clay Club," of the extraction techniques available to obtain water and solutes from argillaceous rocks. The paper focuses on the mechanisms involved in the extraction processes, the consequences on the isotopic and chemical composition of the extracted pore water and the attempts made to reconstruct its original composition. Finally, it provides some examples of reliable techniques and information, as a function of the purpose of the geochemical study. Electronic Publication  相似文献   

Mouvements actuels des blocs tectoniques dans l’arc Bético-Rifain à partir des mesures GPS entre 1999 et 2005     

Abdelilah Tahayt  Taoufik Mourabit  Alexis Rigo  Kurt L. Feigl  Abdelali Fadil  Simon McClusky  Robert Reilinger  Mostafa Serroukh  Abdelouahed Ouazzani-Touhami  Driss Ben Sari  Philippe Vernant   《Comptes Rendus Geoscience》2008,340(6):400-413

GPS velocities and seismicity across the Betic–Rif Arc structural domains (Morocco and Iberia) provide a basis to evaluate present-day seismotectonic processes between different deformation belts. The results show asymmetric movements in the complex Alboran system accommodating the convergence between the African (Nubian) and Eurasian plates. While the Betic Mountains are attached to Iberia, moving toward the southeast with respect to Africa, the Rif is divided into three blocks with distinct displacements relative to Nubia: (1) the Tangier block moving southeastward, (2) the Central Rif block moving SSW, and (3) the Oriental Rif block undergoing clockwise rotation. GPS-derived motions decrease in rate from the Rif nappes complex to the foreland.  相似文献   

Editors’ Message: the Hydrogeologist Time Capsule — archival video recordings of influential hydrogeologists   总被引：1，自引：1，他引：0  

Craig T. Simmons  Philippe Renard 《Hydrogeology Journal》2008,16(1):1-3

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Collision and stress trajectories in Taiwan: a finite element model   总被引：2，自引：0，他引：2  

Philippe Huchon  Eric Barrier  Jean-Claude de Bremaecker  Jacques Angelier 《Tectonophysics》1986,125(1-3)

Field analyses of Plio-Quaternary compressional deformations in Taiwan have enabled us to reconstruct the paleostress trajectories resulting from the collision of the Luzon arc (Philippine Sea plate) with the Chinese continental margin (Eurasian plate). The direction of the maximum compressional stress σ₁ shows a fan-shaped pattern that we interpret as resulting from the collision of a rigid body (the Luzon arc) indenting a more deformable material (the thick sediments of the Chinese continental margin). Simple analytical models qualitatively explain the fan-shaped pattern, but the influence of various parameters such as boundary conditions and rheology cannot be quantitatively accounted for by this approach. Consequently, we have used a finite element technique to compute the stresses and strains induced by the push of a rigid body against a two-dimensional, viscous material. The boundary conditions are the velocities based on plate kinematics. A motion in the N300°E direction best explains the stress trajectories observed in central Taiwan. Viscosity contrasts as well as small changes in the shape of the northern edge of the indenter have little influence on the computed stress pattern. The most important parameter is the direction of convergence. Our model quantitatively explains the general pattern of the stress trajectories observed in the collision zone of Taiwan, between the Philippine Sea plate and Eurasia.  相似文献   

The Pleistocene hominid site of Ternifine, Algeria: New results on the environment, age, and human industries     

Denis Geraads  Jean-Jacques Hublin  Jean-Jacques Jaeger  Haiyan Tong  Sevket Sen  Philippe Toubeau 《Quaternary Research》1986,25(3)

A new multidisciplinary research program, started in 1981, provided new data on the stratigraphy, fauna, and human industries, as well as the first results on paleomagnetism and sedimentology, for the Ternifine site in Algeria, which yielded the earliest hominid remains known in North Africa. The fossils were deposited in a swamp or lake surrounded by a very open, dry environment. The lake was fed by artesian springs that raised the underlying Miocene sands. Although nothing suggests a camp or butchery site, we discovered the first undisputable bone artifact in this site, the earliest known in this part of Africa. According to paleontological data, 700,000 yr B.P. is a likely age for the Ternifine deposits, which is consistent with the paleomagnetic results.  相似文献   

Tectonic record of convergence changes in a collision area: the Boso and Miura peninsulas, Central Japan     

Jacques Angelier  Philippe Huchon 《Earth and Planetary Science Letters》1987,81(4)

Late Cenozoic formations in Boso and Miura have been affected by several tectonic events. Tectonic analysis enables us to reconstruct six different paleostress types: (1) early extension affecting the Oligocene/early Miocene Mineoka Group, (2) and (3), relatively minor compressional and extensional events probably early Pliocene in age, (4) major NNE-SSW compression dominating prior to 2 or 3 Ma ago, and (5) and (6) more recent major NNW-SSE compression to the west and WNW-ESE extension to the east, both types affecting the Pleistocene and prevailing since 1–2 Ma ago. The counterclockwise change from NNE-SSW to NNW-SSE compression is not accurately dated, but very likely occurred between 2 and 3 Ma ago; it is compared to similar evolutions in other areas of the Izu collision zone. We conclude that it corresponds to a major counterclockwise change in the direction of plate convergence (from SSE-NNW to SE-NW). The relationships between the directions of convergence and the distributions of Plio-Quaternary compressional paleostresses in and around the collision zone are described through a simple analogy, for the two stages of Plio-Quaternary collision. This counterclockwise change in stress fields and relative motions, also described in the Taiwan collision zone along the same Philippine Sea plate-Eurasia boundary, is interpreted as a major event at the scale of the plate. The possible significances of the other paleostress types identified in Boso are discussed. We conclude that tectonic analysis in and along collision boundaries provides a key for understanding kinematic evolution.  相似文献   

A thermal model for the origin of post-erosional alkalic lava, Hawaii     

Philippe Gurriet 《Earth and Planetary Science Letters》1987,82(1-2)

The model of lithospheric thinning and reheating for the origin of the Hawaiian swell assumes that the lower lithosphere (> 60 km) is rapidly reset to an asthenospheric temperature as it passes over the hot spot. It is shown that this heat input induces melting in a few kilometer thick layer of lithosphere just above the thermal anomaly. By solving the appropriate energy equation, the mean degree of melting in the molten layer was estimated to be 1–5% with a total melt thickness of 25–150 m. The minimum width of the thermal anomaly required to account for the observed rate of post-erosional eruptions is of the order of 10–40 km which is probably satisfied. The melt generated by this process matches the petrological and geochemical characteristics of Hawaiian post-erosional lava and their typical MORB-related isotopic signature. Because small degrees of melting are involved, the extraction time scale is long (a few million years) and is consistent with the time span of post-erosional eruptions. Also, the characteristic sequence of Hawaiian volcanism can be explained if the source for Hawaiian lava is considered as a molten layer with melt fraction decreasing upward.  相似文献   

Deep-sea submersible survey in the Suruga, Sagami and Japan Trenches: preliminary results of the 1985 Kaiko cruise, Leg 2     

Guy Pautot  Kazuaki Nakamura  Philippe Huchon  Jacques Angelier  Jacques Bourgois  Kantaro Fujioka  Toshihiko Kanazawa  Yasuo Nakamura  Yujiro Ogawa  Michel Sguret  Akira Takeuchi 《Earth and Planetary Science Letters》1987,83(1-4)

Nine submersible dives were made in three trenches off central Japan, between 2990 and 5900 m of water depth. Our observations confirm the interpretation that Daiichi-Kashima Seamount is a Cretaceous guyot formed on the Pacific plate that has traveled into the Japan Trench. We also confirmed the previous interpretation of a large normal fault that splits the seamount in two halves, the lower one being now subducting beneath the Japan margin. Compressional deformation was identified within the lower part of the inner slope in front of the seamount. The pattern of deformation that affects Quaternary sediments is in agreement with the present kinematics of the convergence between the Pacific plate and Japan. Deep-water (5700 m) clam colonies are associated with advection of fluids, driven by the subduction-related overpressures. In the northern slope of the Boso Canyon, along the Sagami Trough system (Philippine Sea plate-Japan boundary), the deformation affecting a thick upper Miocene to lower Pliocene sequence indicates two directions of shortening: a N175°E direction which is consistent with the present relative motion along the Sagami Trough (N285–N300°E) and a N30°E direction which could be related to a more northerly direction of convergence that occured during the early Quaternary and earlier.  相似文献   

Chaotic axisymmetrical spherical convection and large-scale mantle circulation     

Philippe Machetel  David A. Yuen 《Earth and Planetary Science Letters》1987,86(1)

This paper presents a study of high Rayleigh number (up to 200 times supercritical) axisymmetrical convection in a spherical shell with an aspect ratio relevant for the Earth's lower mantle. Both bottom-heated and internal heated cases have been considered. Computations have been carried out for an infinite Prandtl number isoviscous fluid with free slip isothermal boundary conditions. The first part of the paper is devoted to the influence of the resolution on the accuracy of the numerical results. It is shown that the resolution strongly influences the onset of time dependence. Recent methods of non-linear physics have been used to prove that the time dependence and the chaotic behaviors of the solutions are real ones. From these results we can confirm that convection is chaotic, in this particular geometry, even for Rayleigh numbers 200 times critical. Aperiodic boundary layer instabilities are found to be incapable of breaking up the large-scale flow, owing to the shear of the global circulation. Spectral analysis of the power associated with the thermal anomalies shows that there is an upward cascade of energy, due to small-scale chaotic instabilities, from l = 2 to l = 4–6 at the bottom boundary, in agreement with new seismic observations at the core-mantle boundary [1–3].  相似文献