Morphology and downslope sediment displacement in a deep-sea valley,the Valencia Valley (Northwestern Mediterranean)     

Suzanne O'Connell  Belen Alonso  Kim A. Kastens  Andrés Maldonado  Alberto Malinverno  C. Hans Nelson  Alberto Palanques  William B. F. Ryan 《Geo-Marine Letters》1985,5(3):149-156

The Valencia Valley is a Quaternary, 200 km long deep-sea valley in the Valencia Trough, Western Mediterranean Sea. A swathmapping survey approximately mid-way along the valley length, where the floor has an average gradient of 1:250 (0.2°), shows valley walls that rise 200 to 350 m above the valley floor, with slopes of 2 to 18°. Sediment forming the walls is undergoing retrogressive, upslope-directed slumping with increasing bedding disruption along steeper walls. The valley exhibits a winding course with steep outer and gentler inner walls around bends, and bedforms on the valley floor. Lateral migration around bends is less than 5 km and the valley is deeply entrenched into Quaternary-bedded sediments.  相似文献   

Fortresses of desire: Melrose Arch and the emergence of urban tourist spectacles     

Teresa Dirsuweit  Florian Schattauer 《GeoJournal》2004,60(3):239-247

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Solar particle events seen by the MOPITT instrument     

Florian Nichitiu  James R. Drummond  Jiansheng Zou  Robert Deschambault 《Journal of Atmospheric and Solar》2004,66(18):40

This paper reports on Device Single Events (DSEs) occurring in the Measurements Of Pollution In The Troposphere (MOPITT) space instrument piezoelectric accelerometers. It is found that DSEs correlate with the radiation environment, solar activity and high intensity Solar Proton Events.  相似文献   

Influence of glacier advance on the development of the multipart Riffeltal rock glacier,Central Austrian Alps          下载免费PDF全文

Jana‐Marie Dusik  Matthias Leopold  Tobias Heckmann  Florian Haas  Ludwig Hilger  David Morche  Fabian Neugirg  Michael Becht 《地球表面变化过程与地形》2015,40(7):965-980

The multipart Riffeltal rock glacier, located in a tributary valley of the Kaunertal, Tyrol, Austria is investigated to enlarge the knowledge about spatial and temporal development of rock glaciers in and at the margins of pro‐glacial areas and to get a better understanding of glacier–rock glacier interactions. The subject of interest consists of a complex system of two adjacent rock glacier tongues and various superposed lobes with differing ages, origin and root zones, and therefore diverse development. To determine the reasons for their diverging development, the internal structure and permafrost occurrence on and in the surrounding area of the rock glacier were studied by application of geomorphological mapping, geophysical methods and measurement of the basal temperature of the winter snow cover (BTS). Permafrost modelling was performed on the basis of BTS data and land surface parameters derived from a high resolution airborne laser scanning (ALS) digital elevation model (DEM). Additionally, the ALS data were used to measure vertical and horizontal changes of the rock glacier surface between 2006 and 2012. Glacier–rock glacier interactions during and since the Little Ice Age (LIA) are evident for the development of the studied rock glacier. A geomorphic map gives important information about the connection between glacial advance or retreat and permafrost or ground ice occurrence. The combination of all information helps in the analysis of diverse kinematic action of neighbouring rock glacier tongues. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

From geotechnical analysis to quantification and modelling using LiDAR data: a study on rockfall in the Reintal catchment,Bavarian Alps,Germany     

Tobias Heckmann  Martin Bimböse  Michael Krautblatter  Florian Haas  Michael Becht  David Morche 《地球表面变化过程与地形》2012,37(1):119-133

In the year 2007, enhanced rockfall activity was observed within the scarp of a 500 BP rockslide in the Reintal catchment (Northern Calcareous Alps, Germany); the largest of a series of events took place in August, when almost 50000 m³ of rock were detached from the subvertical rock face and deposited on a talus cone. In this case study, we focus on three aspects of rockfall research: first, we compile detailed geomorphological and geotechnical findings to explain the causes of the recent events. The results of laboratory tests and stability estimations suggest that rockfall activity will persist in the future as the old rockslide scarp still contains unstable rock masses. Second, we use digital elevation data from a pre‐event airborne LiDAR survey (ALS) and post‐event terrestrial laserscanning (TLS) to quantify landform changes and the mass balance of the rockfall event(s). The widespread availability of ALS elevation data provides a good opportunity to quantify fresh events using a comparatively inexpensive TLS survey; this approach is complicated by uncertainties resulting from the difficult coregistration of ALS and TLS data and the specific geometric problems in steep (ALS) and flat (TLS) terrain; it is therefore limited to at least medium‐sized events. Third, the event(s) is simulated using the results of the LiDAR surveys and a modified GIS‐based rockfall model in order to test its capability of predicting the extent and the spatial distribution of deposition on the talus cone. Results show that the model generally reproduces the process domain and the spatial distribution of topographic changes but frequently under‐ and over‐estimates deposition heights. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Characteristics of developing scour-holes at a sand-embedded cylinder   总被引：3，自引：2，他引：1  

Oscar LINK  Florian PFLEGER  and Ulrich ZANKE Dr.-Ing.  Assistant Prof.  Dept. of Civil Engineering  University of Concepción  Edmundo Larenas  Concepción  Chile. Doctoral Research Fellow  Institute for Hydromechanics  Technische Universitt München  Arcisstrasse  München  Germany. Full Prof.  Institute for Hydraulic  Water Resources Engineering  Darmstadt University of Technology  Rundeturmstraβe  Germany. 《国际泥沙研究》2008,23(3):258-266

Characteristics of developing scour-holes at a sand-embedded 0.2 m diameter circular cylinder are presented. Non-intrusive, high-resolution topographic measurements of developing scour-holes were made with an experimental installation using a laser distance sensor （LDS） and precision step-motors. A clear-water experiment was conducted with bed shear stress equal to 95% of the critical bed shear stress for the initiation of sediment motion at the undisturbed plane sand bed with a d50 of 0.26 mm. During the running experiment of 21 hours duration, measurements were taken by the LDS in different azimuthal half-planes with θ= 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165 and 180° in order to study the spatio-temporal variation of geometric properties in developing scour-holes. After 21 hours, the equilibrium condition was approached, with a scour rate less than d50 per hour. Measurement of maximum scour depth in different azimuthal half-planes at different points in time during the experiment show that scour started at the cylinder side and surrounded the cylinder after about 20% of experiment time. Slopes of developing scour-holes presented three regions with different inclinations, which were attributed to vortex action. Both maximum scour depth and maximum scour radius at different azimuthal half-planes are well correlated with the maximum scour depth at plane with θ = 0°. When providing maximum scour depth at the cylinder front, the presented correlations are useful for simple calculation of scour-hole topography. This work provides an experimental database for advanced numerical simulation for loose sediment hydraulics.  相似文献   

Multi-method global sensitivity analysis of flood inundation models   总被引：1，自引：0，他引：1  

Florian Pappenberger  Keith J. Beven  Marco Ratto  Patrick Matgen 《Advances in water resources》2008

Global sensitivity analysis is a valuable tool in understanding flood inundation models and deriving decisions on strategies to reduce model uncertainty. In this paper, a sensitivity analysis of a one-dimensional flood inundation model (HEC-RAS) on the River Alzette, Luxembourg, is presented. It is impossible to define sensitivity in a unique way and different methods can lead to a difference in ranking of importance of model factors. In this paper five different methods (Sobol, Kullback–Leibler entropy, Morris, regionalised sensitivity analysis and regression) are applied and the outcomes on selected examples compared. It is demonstrated that the different methods lead to completely different ranking of importance of the parameter factors and that it is impossible to draw firm conclusions about the relative sensitivity of different factors. Moreover, the uncertainty inherent in the sensitivity methods is highlighted.  相似文献   

Landslides, Ice Quakes, Earthquakes: A Thermodynamic Approach to Surface Instabilities     

Klaus Regenauer-Lieb  David A. Yuen  Florian Fusseis 《Pure and Applied Geophysics》2009,166(10-11):1885-1908

The total rate of rock deformation results from competing deformation processes, including ductile and brittle mechanisms. Particular deformation styles arise from the dominance of certain mechanisms over others at different ambient conditions. Surprisingly, rates of deformation in naturally deformed rocks are found to cluster around two extremes, representing coseismic slip rates or viscous creep rates. Classical rock mechanics is traditionally used to interpret these instabilities. These approaches consider the principle of conservation of energy. We propose to go one step further and introduce a nonlinear far-from-equilibrium thermodynamic approach in which the central and explicit role of entropy controls instabilities. We also show how this quantity might be calculated for complex crustal systems. This approach provides strain-rate partitioning for natural deformation processes occurring at rates in the order of 10^-3 to 10^-9 s^-1. We discuss these processes using examples of landslides and ice quakes or glacial surges. We will then illustrate how the mechanical mechanisms derived from these near-surface processes can be applied to deformation near the base of the seismogenic crust, especially to the phenomenon of slow earthquakes.  相似文献   

Climate variability over the last 9900 cal yr BP from a swamp forest pollen record along the semiarid coast of Chile     

Antonio Maldonado  Carolina Villagrán 《Quaternary Research》2006,66(2):246-258

We present a fossil pollen analysis from a swamp forest in the semiarid coast of Chile (32°05′S; 71°30′W), at the northern influence zone of southern westerly wind belt. A ∼10,000 cal yr BP (calendar years before 1950) palynological sequence indicates a humid phase characterized by dense swamp forest taxa dated between ∼9900 and 8700 cal yr BP. The presence of pollen-starved sediments with only scant evidence for semiarid vegetation indicates that extreme aridity ensued until ∼5700 cal yr BP. The swamp forest recovered slowly afterwards, helped by a significant increase in moisture at ∼4200 cal yr BP. A new swamp forest contraction suggests that another slightly less intense drought occurred between ∼3000 and 2200 cal yr BP. The swamp forest expansion begins again at ∼2200 cal yr BP, punctuated by a highly variable climate. Comparisons between the record presented here with other records across the region imply major variations in the extent of the southern westerlies during the Holocene. This variability could have been caused either by latitudinal displacements from the present mean position of southern westerlies wind belt or by changes in the intensity of the South Pacific Subtropical Anticyclone, both of which affect winter precipitation in the region.  相似文献   

Coupled modeling of thermics and hydrogeology with the Cast3M code: application to the Rainbow hydrothermal field (Mid-Atlantic Ridge, 36°14′N)     

Florian Perez  Claude Mügler  Philippe Jean-Baptiste  Jean Luc Charlou 《Computational Geosciences》2013,17(2):217-237

We present a new numerical tool developed in the Cast3M software framework to model hydrothermal circulation. Thermodynamic properties of one-phase pure water are calculated from the International Association for the Properties of Water and Steam formulation. This new numerical tool is validated on several test cases of convection in closed-top and open-top boxes. Simulations of hydrothermal circulation in a homogeneous-permeability porous medium also give results in good agreement with already published simulations. This new numerical tool is used to construct a geometric and physical conceptual model of the Rainbow vent site at 36°14^′N on the Mid-Atlantic Ridge. Several configurations are discussed, showing that high temperatures and high mass fluxes measured at the Rainbow site cannot be modeled with hydrothermal circulation in a homogeneous-permeability porous medium. These high values require the presence of a fault or a preferential pathway right below the venting site. We propose and discuss a two-dimensional single-pass model that allows us to simulate both high temperatures and high mass fluxes. This modeling of the hydrothermal circulation at the Rainbow site constitutes the first but necessary step to understand the origin of high concentrations of hydrogen issued from this ultramafic-hosted vent field.  相似文献