MHYDAS‐Erosion: a distributed single‐storm water erosion model for agricultural catchments     

Silvio Jose Gumiere  Damien Raclot  Bruno Cheviron  Gregory Davy  Xavier Louchart  Jean‐Christophe Fabre  Roger Moussa  Yves Le Bissonnais 《水文研究》2011,25(11):1717-1728

In this paper, we present MHYDAS‐Erosion, a dynamic and distributed single‐storm water erosion model developed as a module of the existing hydrological MHYDAS model. As with many catchment erosion models, MHYDAS‐Erosion is able to simulate sediment transport, erosion and deposition by rill and interrill processes. Its originality stems from its capacity to integrate the impact of land management practices (LMP) as key elements controlling the sedimentological connectivity in agricultural catchments. To this end, the water‐sediment pathways are first determined by a specific process‐oriented procedure defined and controlled by the user, which makes the integration of LMP easier. The LMP dynamic behaviours are then integrated into the model as a time‐dependent function of hydrological variables and LMP characteristics. The first version of the model was implemented for vegetative filters and tested using water and sediment discharge measurements at three nested scales of a densely instrumented catchment (Roujan, OMERE Observatory, southern France). The results of discharge and soil loss for simulated rainfall events have been found to acceptably compare with available data. The average R² values for water and sediment discharge are 0·82 and 0·83, respectively. The sensitivity of the model to changes in the proportion of LMP was assessed for a single rain event by considering three scenarios of the Roujan catchment management with vegetative filters: 0% (Scenario 1), 18% (Scenario 2, real case) and 100% (Scenario 3). Compared to Scenario 2 (real case), soil losses decreased for Scenario 3 by 65% on the agricultural plot scale, 62% on the sub‐catchment scale and 45% at the outlet of the catchment and increased for Scenario 1 by 0% on the plot scale, 26% on the sub‐catchment scale and 18% at the outlet of the catchment. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Würmian deglaciation of western Lake Geneva (Switzerland) based on seismic stratigraphy     

Julien Fiore  Stéphanie Girardclos  André Pugin  Georges Gorin  Walter Wildi 《Quaternary Science Reviews》2011,30(3-4):377-393

Western Lake Geneva (le Petit-Lac) was filled during the Quaternary over a major erosion surface truncating the cemented, folded and thrusted Tertiary sediments of the foreland Alpine basin. The carving of the lake occurred during Quaternary glaciations with ice originating from the Rhone valley catchment basin flowing in two branches oriented SW and NE over the Swiss Plateau. Lake Geneva is situated on the South-Western branch of this paleo ice-cap.For the first time, a dense grid of high-resolution seismic profiles (airgun 5-inch³, airgun 1-inch³ and echosounder) has imaged the whole Quaternary sequence, providing a paleoenvironmental interpretation and a detailed reconstruction of the Rhone glacier retreat stages during glacial events that led to the formation of western Lake Geneva.The Quaternary sequence filling up the bedrock valley is exceptionally thick with up to 220 m of deposits and consists of glacial, glacio-lacustrine and lacustrine sediments. Fourteen seismic units have been defined (units U1–U14). Unit U1 represents the remnants of glacial deposits older than the last glacial cycle, preserved in the deepest part of the lake and in secondary bedrock valleys. Unit U2 represents gravel and sands deposited by meltwater circulation at the bottom of the glacial valley. Unit U3 is a thick, stratified unit marking the beginning of the deglaciation, when the Rhone glacier became thinner and buoyant and allowed the formation of a subglacial lake. Younger glacial units (units U4, U5, U7, U9, U11) are acoustically chaotic sediments deposited subglacially under the water table (undermelt tills), while the glacier was thinning. These glacial units are bounded by synform erosion surfaces corresponding to readvances of the glacier.The transition from a glacial to a glacio-lacustrine environment started with the appearance of a marginal esker-fan system (unit U6). Esker formation was followed by a small advance–retreat cycle leading to the deposition of unit U7. Then, the ice front receded and stratified sediments were deposited in a glacio-lacustrine environment (units U8, U10 and U12). This retreat was punctuated by two readvances – Coppet (unit U9) and Nyon (unit U11) – producing large push moraines and proglacial debris flows. Finally, a lacustrine environment with a characteristic lake current pattern and mass movement deposits took place (units U13 and U14).Except for unit U1, the sedimentary sequence records the Würmian deglaciation in a fjord-like environment occupied by a tidewater glacier with a steep, calving ice front. The presence of an esker-fan system reveals the importance of subglacial meltwater flow in continental deglaciation. Push-moraines and erosion surfaces below the glacier indicate at least 5 readvances during the deglaciation thus revealing that oscillations of ice front are the key process in deglaciation of perialpine fjord-lakes. The dating of these continental glacier fluctuations would allow correlation with oceanic and ice records and help to understand the climatic mechanisms between oceans and continents.  相似文献   

Tectono‐stratigraphic history of the southern Junggar basin: seismic profiling evidences     

Sheng‐Li Wang  Yan Chen  Julien Charreau  Dong‐Tao Wei  Dong Jia 《地学学报》2013,25(6):490-495

The modern Tianshan is an active intracontinental range in central Asia. Its initial timing is poorly known and still hotly debated. As the subsidence of foreland basins is intrinsically coupled with the uplift of orogenic wedges, the foreland sedimentary records may accurately constrain the Tianshan uplifting history. To better address the question, we analyse a seismic profile across the southern Junggar foreland basin to decipher its tectonic and stratigraphic history. Four structural layers can be identified in an ascending order: the Permian – Lower Jurassic transtension‐related layer, the Jurassic – Cretaceous thermal‐subsistence layer, the Palaeogene layer and the Miocene – Quaternary foreland sedimentary layer. The oldest sedimentary sequence in the foreland succession is of the Shawan Formation deposited at ~24 Ma based on magnetostratigraphic constraints. This indicates that foreland deformation in the northern Tianshan and uplifting of the modern Tianshan probably initiated at the beginning of the Miocene.  相似文献   

High and very high resolution deep-towed seismic system: Performance and examples from deep water Geohazard studies     

T. Marsset  B. Marsset  S. Ker  Y. Thomas  Y. Le Gall 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):628-637

We present the technological development and initial results from the deep-towed seismic acquisition device SYstème SIsmique Fond de mer (SYSIF) recently built by Ifremer. The two configurations of the SYSIF are presented (high resolution (HR): 250–1000 Hz and very high resolution (VHR): 650–2000 Hz), and results are compared to conventional seismic acquisition systems such as multi-channel HR or single-channel VHR (hull-mounted sub-bottom profiler). The ability of SYSIF to achieve higher resolution imagery is due to both the technology employed (low-frequency Janus–Helmoltz piezoelectric transducer) and the deep-towed operating mode (reduction in the Fresnel zone). Sea trials have been conducted in various geological environments and in water depths as deep as 2500 m. The new technique improved imaging of deep seafloor and sub-surface features such as pockmarks, carbonate mounds, sub-marine slides and sub-surface faulting. SYSIF, therefore, is a well-suited tool to investigate deep water geological features, especially those related to geohazard for scientific and industrial purposes.  相似文献   

Large‐scale flexuring and antithetic extensional faulting along a nascent plate boundary in the SE Afar rift     

Bernard Le Gall  Mohamed Ahmed Daoud  Joel Rolet  Nima Moussa Egueh 《地学学报》2011,23(6):416-420

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Micromechanical models of the strength of a sandstone     

L. Dormieux  L. Jeannin  E. Bemer  T. H. Le  J. Sanahuja 《国际地质力学数值与分析法杂志》2010,34(3):249-271

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Estimation of an upper limit on prehistoric peak ground acceleration using the parameters of intact speleothems in Hungarian caves     

Győző Szeidovitz  Gergely Surányi  Katalin Gribovszki  Zoltán Bus  Szabolcs Leél-Őssy  Zsolt Varga 《Journal of Seismology》2008,12(1):21-33

The examination of speleothems in the Hajnóczy and Baradla caves (northeastern Hungary) allows estimating an upper limit for horizontal peak ground acceleration generated by paleoearthquakes. The density, the Young’s modulus and the tensile failure stress of the samples originating from a broken speleothem have been measured in a laboratory, whereas the natural frequency of intact speleothems was determined by in situ observations. The value of horizontal ground acceleration resulting in failure, the natural frequency and the inner friction coefficient of speleothems were assessed by theoretical calculations. The ages of the samples taken from a stalagmite 5.1 m in height (Baradla cave) have been determined by inductively coupled plasma mass spectrometry analysis and alpha spectrometry. The measured ages fall between 140,000 and 70,000 years; therefore, we assume the speleothem has not been changed since the end of this time interval. According to our modeling results, this speleothem has not been excited by a horizontal acceleration higher than 0.05 g during the last 70,000 years.  相似文献   

Study of large-scale deformation induced by gravity on the La Clapière landslide (Saint-Etienne de Tinée,France) using numerical and geophysical approaches     

E. Tric  T. Lebourg  H. Jomard  J. Le Cossec 《Journal of Applied Geophysics》2010,70(3):206-215

The large-scale deformation of high mountain slopes finds its origin in many phenomena with very different time-constants. Gravitational effect, tectonic forces, and water infiltration are generally the principal causes. However, it is always very difficult to distinguish which cause is dominant and which are their respective effects. A two-dimensional numerical experiment coupled with geophysical approach was carried out to determine (1) the effect of gravitational force on the mechanical behaviour of the “la Clapière” area, (2) a 2D-depth structure of this landslide. The results show that gravitational instability is possible and leads to destabilisation of the massif by a regressive evolution of the landslide from the bottom at 1100 m up to a height of 1800 m, which is actually the top of the La Clapière landslide. This deformation progression only concerns a depth of around 150 ± 50 m, which can be correlated to the sliding surface, as suggested by our electrical data obtained by resistivity investigations and previous studies. Our numerical results suggest that changes of the slope topography “drive” the diffusion of the plastic deformation in the mass, possibly through a channel which could be then the privileged zone along which the fracture is initiated.  相似文献   

Three-dimensional numerical modelling of the behaviour of a pile subjected to cyclic lateral loading     

E. Bourgeois  M.H.J. Rakotonindriana  A. Le Kouby  P. Mestat  J.F. Serratrice 《Computers and Geotechnics》2010,37(7-8):999-1007

This paper presents a finite element simulation of the behaviour of a vertical pile subjected to a cyclic lateral loading. First, the choice of a suitable constitutive model is discussed. The analytical solution of the model equations for a monotonic triaxial compression is given, and the model is compared with monotonic and cyclic triaxial tests on dry Fontainebleau sand. Simulations of tests carried out on a model pile with the geotechnical centrifuge of the French Public Works Research Laboratory (LCPC) were then performed with the model parameters derived from the triaxial tests. Results are in good agreement with experiments.  相似文献   

Erratum to: Iron in monticellite as an oxygen barometer for kimberlite magmas     

Audrey Le Pioufle  Dante Canil 《Contributions to Mineralogy and Petrology》2012,163(6):1047-1047

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