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31.
Nadia Senechal Stéphane Abadie Edith Gallagher Jamie MacMahan Gerd Masselink Hervé Michallet Ad Reniers Gerben Ruessink Paul Russell Damien Sous Ian Turner Fabrice Ardhuin Philippe Bonneton Stéphane Bujan Sylvain Capo Raphael Certain Rodrigo Pedreros Thierry Garlan 《Ocean Dynamics》2011,61(12):2073-2098
A large multi-institutional nearshore field experiment was conducted at Truc Vert, on the Atlantic coast of France in early 2008. Truc Vert’08 was designed to measure beach change on a long, sandy stretch of coast without engineering works with emphasis on large winter waves (offshore significant wave height up to 8 m), a three-dimensional morphology, and macro-tidal conditions. Nearshore wave transformation, circulation and bathymetric changes involve coupled processes at many spatial and temporal scales thus implying the need to improve our knowledge for the full spectrum of scales to achieve a comprehensive view of the natural system. This experiment is unique when compared with existing experiments because of the simultaneous investigation of processes at different scales, both spatially (from ripples to sand banks) and temporally (from single swash events to several spring-neap tidal cycles, including a major storm event). The purpose of this paper is to provide background information on the experiment by providing detailed presentation of the instrument layout and snapshots of preliminary results. 相似文献
32.
Andreas Günther Paola Reichenbach Jean-Philippe Malet Miet Van Den Eeckhaut Javier Hervás Claire Dashwood Fausto Guzzetti 《Landslides》2013,10(5):529-546
In the framework of the European Soil Thematic Strategy and the associated proposal of a Framework Directive on the protection and sustainable use of soil, landslides were recognised as a soil threat requiring specific strategies for priority area identification, spatial hazard assessment and management. This contribution outlines the general specifications for nested, Tier-based geographical landslide zonings at small spatial scales to identify priority areas susceptible to landslides (Tier 1) and to perform quantitative susceptibility evaluations within these (Tier 2). A heuristic, synoptic-scale Tier 1 assessment exploiting a reduced set of geoenvironmental factors derived from common pan-European data sources is proposed for the European Union and adjacent countries. Evaluation of the susceptibility estimate with national-level landslide inventory data suggests that a zonation of Europe according to, e.g. morphology and climate, and performing separate susceptibility assessments per zone could give more reliable results. To improve the Tier 1 assessment, a geomorphological terrain zoning and landslide typology differentiation are then applied for France. A multivariate landslide susceptibility assessment using additional information on landslide conditioning and triggering factors, together with a historical catalogue of landslides, is proposed for Tier 2 analysis. An approach is tested for priority areas in Italy using small administrative mapping units, allowing for relating socioeconomic census data with landslide susceptibility, which is mandatory for decision making regarding the adoption of landslide prevention and mitigation measures. The paper concludes with recommendations on further work to harmonise European landslide susceptibility assessments in the context of the European Soil Thematic Strategy. 相似文献
33.
Distinguishing volcanic debris avalanche deposits from their reworked products: the Perrier sequence (French Massif Central) 总被引:1,自引:1,他引:0
Benjamin Bernard Benjamin van Wyk de Vries Hervé Leyrit 《Bulletin of Volcanology》2009,71(9):1041-1056
Debris avalanches associated with volcanic sector collapse are usually high-volume high-mobility phenomena. Debris avalanche
deposit remobilisation by cohesive debris flows and landslides is common, so they can share textural characteristics such
as hummocks and jigsaw cracks. Distinguishing original deposits from reworked products is critical for geological understanding
and hazard assessment because of their different origin, frequency and environmental impact. We present a methodology based
on field evidence to differentiate such epiclastic breccias. Basal contact mapping constrained by accurate altitude and location
data allows the reconstruction of deposit stratigraphy and geometry. Lithological analysis helps to distinguish the different
units. Incorporation structures, kinematic indicators and component mingling textures are used to characterise erosion and
transport mechanisms. We apply this method to the enigmatic sequence at Perrier (French Massif Central), where four units
(U1–U4) have been interpreted either as debris flow or debris avalanche deposits. The sequence results from activity on the
Monts Dore Volcano about 2 Ma ago. The epiclastic units are matrix supported with an almost flat top. U2 and U3 have clear
debris flow deposit affinities such as rounded clasts and intact blocks (no jigsaw cracks). U1 and U4 have jigsaw cracked
blocks with matrix injection and stretched sediment blocks. U1 lacks large blocks (>10 m wide) and has a homogenous matrix
with an upward increase of trapped air vesicle content and size. This unit is interpreted as a cohesive debris flow deposit
spawned from a debris avalanche upstream. In contrast, U4 has large mega-blocks (up to 40 m wide), sharp contacts between
mixed facies zones with different colours and numerous jigsaw fit blocks (open jigsaw cracks filled by monogenic intra-clast
matrix). Mega-blocks are concentrated near the deposit base and are spatially associated with major substratum erosion. This
deposit has a debris avalanche distal facies with local debris flow affinities due to partial water saturation. We also identify
two landslide deposits (L1 and L2) resulting from recent reworking that has produced a similar facies to U1 and U4. These
are distinguishable from the original deposits, as they contain blocks of mixed U1/U4 facies, a distinctly less consolidated
and more porous matrix and a fresh hummocky topography. This work shows how to differentiate epiclastic deposits with similar
characteristics, but different origins. In doing so, we improve understanding of present and past instability of the Monts
Dore and identify present landslide hazards at Perrier. 相似文献
34.
Claude Robin Jean-Philippe Eissen Pablo Samaniego Hervé Martin Minard Hall Joseph Cotten 《Bulletin of Volcanology》2009,71(3):233-258
The Mojanda–Fuya Fuya Volcanic Complex consists of two nearby volcanoes, Mojanda and Fuya Fuya. The older one, Mojanda volcano
(0.6 to 0.2 Ma), was first constructed by andesites and high-silica andesites forming a large stratovolcano (Lower Mojanda).
This edifice was capped by a basaltic andesite and andesitic cone (Upper Mojanda), which collapsed later to form a 3-km-wide
summit caldera, after large phreatomagmatic eruptions. The Lower Fuya Fuya edifice was constructed by the extrusion of viscous
Si-rich andesitic lavas and dacitic domes, and the emission of a thick sequence of pyroclastic-flow and fallout deposits which
include two voluminous rhyolitic layers. An intermediate construction phase at Fuya Fuya is represented by a mainly effusive
cone, andesitic in composition (San Bartolo edifice), the construction of which was interrupted by a major sector collapse
in the Late Pleistocene. Finally, a complex of thick siliceous lavas and domes was emplaced within the avalanche amphitheatre,
forming the Upper Fuya Fuya volcanic centre. This paper shows that the general evolution from an effusive to an explosive
eruptive style is related to a progressive adakitic contribution to the magma source. Although all the rocks of the complex
are included in the medium-K field of continental arcs, the Fuya Fuya suite (61–75 wt.% SiO2) shows depletion in Y and HREE and high Sr/Y and La/Yb values, compared to the less silicic Mojanda suite (55–66.5 wt.% SiO2). The Mojanda calc-alkaline suite was generated by partial melting of an adakite-metasomatised mantle source that left a
residue with 2% garnet, followed by fractional crystallization of dominant plagioclase + pyroxene + olivine at shallow, intra-crustal
depths. For Fuya Fuya, geochemical and mineralogical data suggest either (1) partial melting of a similar metasomatised mantle
with more garnet in the residue (4%), followed by fractional crystallization involving plagioclase, amphibole and pyroxene,
or (2) mixing of mafic mantle-derived magma from the Mojanda suite and slab melts, followed by the same fractional crystallization
process. 相似文献
35.
Andesite and dacite genesis via contrasting processes: the geology and geochemistry of El Valle Volcano,Panama 总被引:3,自引:0,他引:3
Mare J. Defant Lee F. Clark Robert H. Stewart Mark S. Drummond Jelle Z. de Boer René C. Maury Hervé Bellon Thomas E. Jackson Juan F. Restrepo 《Contributions to Mineralogy and Petrology》1991,106(3):309-324
The easternmost stratovolcano along the Central American arc is El Valle volcano, Panama. Several andesitic and dacitic lava
flows, which range in age 5–10 Ma, are termed the old group. After a long period of quiescence (approximately 3.4 Ma), volcanic
activity resumed approximately 1.55 Ma with the emplacement of dacitic domes and the deposition of dacitic pyroclastic flows
0.9–0.2 Ma. These are referred to as the young group. All of the samples analyzed are calc-alkaline andesites and dacites.
The mineralogy of the two groups is distinct; two pyroxenes occur in the old-group rocks but are commonly absent in the young
group. In contrast, amphibole has been found only in the young-group samples. Several disequilibrium features have been observed
in the minerals (e.g., oscillatory zoning within clinopyroxenes). These disequilibrium textures appear to be more prevalent
among the old- as compared with the young-group samples and are most likely the result of magma-mixing, assimilation, and/or
polybaric crystallization. Mass-balance fractionation models for major and trace elements were successful in relating samples
from the old group but failed to show a relationship among the young-group rocks or between the old- and young-group volcanics.
We believe that the old-group volcanics were derived through differentiation processes from basaltic magmas generated within
the mantlewedge. The young group, however, does not appear to be related to more primitive magmas by differentiation. The
young-group samples cannot be related by fractionation including realistic amounts of amphibole. Distinctive geochemical features
of the young group, including La/Yb ratios〉15, Yb〈1, Sr/Y〉150, and Y〈6, suggest that these rocks were derived from the partial
melting of the subducted lithosphere. These characteristics can be explained by the partial melting of a source with residual
garnet and amphibole. Dacitic material with the geochemical characteristics of subducted-lithosphere melting is generated
apparently only where relatively hot crust is subducted, based on recent work. The young dacite-genesis at El Valle volcano
is related to the subduction of relatively hot lithosphere. 相似文献
36.
Naomi Mazzilli Hervé Jourde Thomas Jacob Vincent Guinot Nicolas Le Moigne Marie Boucher Konstantinos Chalikakis Hélène Guyard Anatoly Legtchenko 《Environmental Earth Sciences》2013,68(6):1631-1646
This work examines the relevance of the inclusion of ground-based gravity data in the calibration process of a global rainfall-discharge reservoir model. The analysis is performed for the Durzon karst system (Larzac, France). The first part of the study focuses on the hydrological interpretation of the ground-based gravity measurements. The second part of the study investigates further the information content of the gravity data with respect to water storage dynamics modelling. The gravity-derived information is found unable to either reduce equifinality of the single-objective, discharge-based model calibration process or enhance model performance through assimilation. 相似文献
37.
A modified parameterization of flux-profile relationships in the surface layer using different roughness length values for heat and momentum 总被引:1,自引:0,他引:1
The surface-layer flux-profile formulae of Louis (1979), used in many atmospheric models, are modified in a simple way to allow for different values of the roughness lengths for heat and momentum. The modified set of formulae simplifies the calculation of surface-layer fluxes over most natural land surfaces, where the roughness length for momentum can be almost an order of magnitude greater than that for heat. 相似文献
38.
Chantal Guillard Hervé Delprat Can Hoang-van Pierre Pichat 《Journal of Atmospheric Chemistry》1993,16(1):47-59
The photodegradation of naphthalene (NPH), chosen as a model of polynuclear aromatic pollutants, has been studied in the presence of a layer of four water-insoluble inorganic solids which can be found in the troposphere (TiO2, Fe2O3, muscovite, and a fly ash sample). Direct photolysis of NPH is negligible at >340 nm. Dark adsorption of NPH on TiO2 (mainly anatase, nonporous, 50 m2 g–1) at 293 K corresponds to a surface coverage ofca. 50% at equilibrium. Under these conditions (saturated surface), the stationary-state photocatalytic degradation reaches 0.4 molecule nm–2 h–1 (>340 nm, radiant fluxca. 22 mW cm–2). Dioxygen is required and its partial pressure in air is such that the degradation is zero order in O2. Water vapor markedly increases the rate. The other particulates have also an effect, less important than that of TiO2, however quite noticeable with respect to surface area unit for the fly ash sample which contains 3.2% Fe2O3. Apart from 1,4-naphthoquinone, which is the main intermediate product in all cases, 2-naphthol, phthalide, phthaldialdehyde, phthalic acid, acetophenone, benzaldehyde, benzoic acid are also formed on dry TiO2. Depending on their volatility, these compounds are transferred to the gas phase or remain principally adsorbed on the solid particles where they are further transformed. For instance, phthalic acid (or anhydride) and benzoic acid are generated from 1,4-naphthoquinone. Degradation mechanisms are briefly discussed. 相似文献
39.
Assessment of groundwater recharge processes through karst vadose zone by cave percolation monitoring
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Amaël Poulain Arnaud Watlet Olivier Kaufmann Michel Van Camp Hervé Jourde Naomi Mazzilli Gaëtan Rochez Romain Deleu Yves Quinif Vincent Hallet 《水文研究》2018,32(13):2069-2083
Recharge processes of karst aquifers are difficult to assess given their strong heterogeneity and the poorly known effect of vadose zone on infiltration. However, recharge assessment is crucial for the evaluation of groundwater resources. Moreover, the vulnerability of karst aquifers depends on vadose zone behaviour because it is the place where most contamination takes place. In this work, an in situ experimental approach was performed to identify and quantify flow and storage processes occurring in karst vadose zone. Cave percolation monitoring and dye tracing were used to investigate unsaturated zone hydrological processes. Two flow components (diffuse and quick) were identified and, respectively, account for 66% and 34% of the recharge. Quickflow was found to be the result of bypass phenomenon in vadose zone related to water saturation. We identify the role of epikarst as a shunting area, most of the storage in the vadose zone occurring via the diffuse flow component in low permeability zones. Relationship between rainfall intensity and transit velocity was demonstrated, with 5 times higher velocities for the quick recharge mode than the diffuse mode. Modelling approach with KarstMod software allowed to simulate the hybrid recharge through vadose zone and shows promising chances to properly assess the recharge processes in karst aquifer based on simple physical models. 相似文献
40.
Mediterranean flash flood transfer through karstic area 总被引:1,自引:0,他引:1
Vincent Bailly-Comte Hervé Jourde Axel Roesch Séverin Pistre 《Environmental Geology》2008,54(3):605-614
Karstic aquifers influence flash floods propagation in Mediterranean countries. Near Montpellier, Southern France, discharge
data are recorded on the Coulazou River upstream and downstream of the Aumelas Causse. Two gauging stations are used to describe
the hydrodynamics of this binary karstic system. The first station characterizes the non-karstic catchment area. The second
one is representative of the karstic part of the watershed. Records since April 2004 are used to understand how the river
interacts with a karstic aquifer. Hydrograph analysis of three flash flood events is described. Corresponding discharge time
series recorded at the two gauging stations are used to describe the modification of the hydrographs by auto- and crosscorrelations
analyses. Finally, linear system analyses are used to provide the transfer functions of this binary karstic system according
to the three flood events characteristics (initial conditions, volume, spatial distribution of rainfall, etc.). Theses functions
summarize the hydrodynamic behaviour of the system: their shapes are indicative of the dynamics of the storage, the release
and the contribution to surface waters.
相似文献
Vincent Bailly-ComteEmail: |