Automated placement of supplementary contour lines     

Timofey Samsonov  Sergey Koshel  Dmitry Walther  Bernhard Jenny 《International journal of geographical information science》2019,33(10):2072-2093

Supplementary contour lines are placed between regular contour lines to visualize small but important forms that regular contour lines are unable to show. On topographic maps, typical forms are hillcrests, depressions, saddles, terraces, banks, and levees. No automated method for the selection of supplementary contour lines has been described so far. We document cartographic design principles for the selection of supplementary contour lines for topographic maps, and present an automated method for their placement. Results of the automated method are similar to manually placed supplementary contour lines. Our method helps map authors to create contour line maps that more effectively illustrate relevant small details in maps showing terrain elevation or other scalar fields.  相似文献   

What do biphasic flow experiments reveal on the variability of exposure on alluvial fans and which implications for risk assessment result from this?     

Diaz  Hector  Mazzorana  Bruno  Gems  Bernhard  Rojas  Ivan  Santibañez  Nicole  Iribarren  Pablo  Pino  Mario  Iroumé  Andrés 《Natural Hazards》2022,111(3):3099-3120

Sudden avulsions, unexpected channel migrations and backfilling phenomena are autogenic phenomena that can considerably change the propagation patterns of sediment-laden flows on alluvial fans. Once the initial and boundary conditions of the hazard scenario with a given return period are determined, the assessment of the associated exposed areas is based on one numerical, essentially deterministic, process simulation which may not adequately capture the underlying process variability. We generated sediment-laden flows on an experimental alluvial fan by following a “similarity-of-process concept”. Specifically, we considered a convexly shaped alluvial fan model layout featuring a curved guiding channel. As loading conditions, we defined a reference, an increased and a reduced level for the released water volume and the predisposed solid fraction, respectively. Further, we imposed two different stream power regimes and accomplished, for each factor combination, eight experimental runs. The associated exposure areas were recorded by video and mapped in a GIS. We then analysed exposure data and determined exposure probability maps superposing the footprints of the eight repetitions associated with each experimental loading condition. The patterns of exposure referred to the specific loading conditions showed a noticeable variability related to the main effects of the total event volume, the solid fraction, the interactions between them, and the imposed stream power in the feeding channel. Our research suggests that adopting a probabilistic notion of exposure in risk assessment and mitigation is advisable. Further, a major challenge consists in adapting numerical codes to better reflect the stochastics of process propagation for more reliable flood hazard assessments.

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Spatio‐temporal variability of zooplankton biomass and environmental control in the Northern Benguela Upwelling System: field investigations and model simulation          下载免费PDF全文

Bettina Martin  Anja Eggert  Rolf Koppelmann  Rabea Diekmann  Volker Mohrholz  Martin Schmidt 《Marine Ecology》2015,36(3):637-658

Spatial and temporal distribution patterns of zooplankton are highly variable in the Northern Benguela Upwelling System. We studied the distribution of zooplankton (size class ≥ 0.33 mm) and used field data from four cruises that took place between March 2008 and February 2011, as well as simulation results of a regional ecosystem model. Remotely sensed sea surface temperatures (SST) and surface chlorophyll concentrations were analysed to investigate environmental influences on zooplankton biomass. The Intense Benguela Upwelling Index showed a distinct seasonal signal throughout the years and the highest upwelling peaks in August/September. Even though surface chlorophyll concentrations were very variable throughout the year, the highest concentrations were always detected in September, following the upwelling of nutrient‐rich water. In field catches, zooplankton biomass concentration in the upper 200 m was highest above the outer shelf and shelf‐break in December 2010 and February 2011, i.e. 6 months after the upwelling peaks. In contrast, zooplankton biomass simulated by the model in the surface water was highest in September. In March/April, biomass maxima were typically measured in the field at intermediate water depths, but the vertical distribution was also affected by extensive oxygen minimum zones. The ecosystem model reproduced this vertical pattern. Although general trends were similar, simulation data of zooplankton standing stocks overestimated the field data by a factor of 3. In upwelling systems, food webs are generally considered to be short and dominated by large cells. However, our field data indicate more small‐sized zooplankton organisms above the shelf than offshore.  相似文献   

Characterisation of deformation and flow mechanics around porphyroclasts in a calcite marble ultramylonite by means of EBSD analysis   总被引：1，自引：0，他引：1  

Michel Bestmann  David J. Prior  Bernhard Grasemann 《Tectonophysics》2006,413(3-4):185-200

This paper studies the flow heterogeneity around porphyroclasts associated with greenschist facies deformation of a calcite marble shear zone. Microstructural data from electron backscatter diffraction analyses (EBSD) are used to constrain the flow mechanics of this dominantly non-coaxial type of deformation. The microstructure of the undisturbed ultramylonite (grain-size range 5–100 μm, mean 40 μm) is interpreted to represent steady-state (time-independent) flow conditions with flow planes parallel to the shear zone boundary. Single calcite porphyroclasts (grain-size 1–3 mm) caused flow perturbation in the fine-grained marble ultramylonite. It is the shape, in particular, of these rigid porphyroclasts that controls their rotational behaviour during deformation and, therefore, the development of specific flow fabrics. The flow planes around elongated-rhomboidal, stable porphyroclasts change the orientation to become roughly parallel to the porphyroclast margin, whereas the geometry of flow planes around nearly equant, rotating porphyroclasts describes a δ-type flow pattern. We infer that to some extent decoupling at the clast–matrix interface has occurred to guarantee a stable orientation of elongated porphyroclasts, but was not sufficient to reduce the rotation rate of equant clasts to zero. According to the flow deflection, the general crystallographic preferred orientation (CPO) with its single c-axis maximum perpendicular to the flow plane is rotated about an axis which is (sub)parallel to the kinematic rotation axis of the shear zone. Ultramylonite microstructures, CPOs and misorientation data are best explained by the dual operation of grain-size-insensitive (dislocation creep with recovery and recrystallization) and grain-size-sensitive (diffusion creep) mechanisms. The limited grain-size reduction around porphyroclasts suggests that the grain-size-insensitive mechanisms controlled rheology.  相似文献   

Laterally constrained inversion of helicopter-borne frequency-domain electromagnetic data     

Bernhard Siemon  Esben Auken  Anders Vest Christiansen 《Journal of Applied Geophysics》2009,67(3):259-268

Helicopter-borne frequency-domain electromagnetic (HEM) surveys are used for fast high-resolution, three-dimensional resistivity mapping. Standard interpretation tools are often based on layered earth inversion procedures which, in general, explain the HEM data sufficiently. As a HEM system is moved while measuring, noise on the data is a common problem. Generally, noisy data will be smoothed prior to inversion using appropriate low-pass filters and consequently information may be lost.For the first time the laterally constrained inversion (LCI) technique has been applied to HEM data combined with the automatic generation of dynamic starting models. The latter is important because it takes the penetration depth of the electromagnetic fields, which can heavily vary in survey areas with different geological settings, into account. The LCI technique, which has been applied to diverse airborne and ground geophysical data sets, has proven to be able to improve the HEM inversion results of layered earth structures. Although single-site 1-D inversion is generally faster and — in case of strong lateral resistivity variations — more flexible, LCI produces resistivity — depth sections which are nearly identical to those derived from noise-free data.The LCI results are compared with standard single-site Marquardt–Levenberg inversion procedures on the basis of synthetic data as well as field data. The model chosen for the generation of synthetic data represents a layered earth structure having an inhomogeneous top layer in order to study the influence of shallow resistivity variations on the resolution of deep horizontal conductors in one-dimensional inversion results. The field data example comprises a wide resistivity range in a sedimentary as well as hard-rock environment.If a sufficient resistivity contrast between air and subsurface exists, the LCI technique is also very useful in correcting for incorrect system altitude measurements by using the altitude as a constrained inversion parameter.  相似文献   

The western end of the Eoalpine High‐Pressure Belt (Texel unit,South Tyrol / Italy)          下载免费PDF全文

Hannah Pomella  David Flöss  Romed Speckbacher  Peter Tropper  Bernhard Fügenschuh 《地学学报》2016,28(1):60-69

Eclogites in the Texel Unit (Eastern Alps; South Tyrol, Italy) represent the westernmost outcrops of the E–W striking Eoalpine High‐Pressure Belt (EHB). East of the Tauern Window, the EHB forms part of a Cretaceous intracontinental south‐dipping subduction/collision zone; however, the same nappe stack displays a northwest dip at its western end. This prominent change in dip direction gave rise to discussions on the general setting of the Eoalpine collision. Based on our own observations and literature data, we present a new tectonic model for the western end of the EHB. Due to the special situation of this area at the tip of the Southalpine indenter, originally south(east) dipping structures became overturned, and former thrusts appear as normal faults (e.g. Schneeberg fault zone) while former normal faults presently display thrust geometries (e.g. Jaufen fault). Thus, we explain the current configuration with a coherent Eoalpine subduction direction.  相似文献   

A comparison of helicopter-borne electromagnetics in frequency- and time-domain at the Cuxhaven valley in Northern Germany     

Annika Steuer  Bernhard Siemon  Esben Auken 《Journal of Applied Geophysics》2009,67(3):194-205

Two different airborne electromagnetic methods were applied in the same area: the frequency-domain helicopter-borne electromagnetic (HEM) system operated by the Federal Institute for Geosciences and Natural Resources, Germany, and the time-domain SkyTEM system of the HydroGeophysics Group at the University of Aarhus, Denmark. For verification of and comparison with the airborne methods, ground-based transient electromagnetics and 2-D resistivity surveying were carried out. The target of investigation was the Cuxhaven valley in Northern Germany, which is a significant local groundwater reservoir. The course of this buried valley was revealed by drillings and the shape was determined by reflection seismics at several cross sections.We applied electrical and electromagnetic methods to investigate the structure of the valley filling consisting of gravel, sand, silt and clay. The HEM survey clearly outlines a shallow conductor at about 20m depth and a deeper conductor below 40m depth inside the valley. This is confirmed by 2-D resistivity surveying and a drilling. The thickness of the deeper conductor, however, is not revealed due to the limited investigation depth of the HEM system. The SkyTEM survey does not resolve the shallow conductor, but it outlines the thickness of the deeper clay layer inside the valley and reveals a conductive layer at about 180m depth outside the valley. The SkyTEM results are very consistent with ground-based transient electromagnetic soundings.Airborne electromagnetic surveying in general has the advantage of fast resistivity mapping with high lateral resolution. The HEM system is cost-efficient and fast, but the more expensive and slower SkyTEM system provides a higher depth of investigation. Ground-based geophysical surveys are often more accurate, but they are definitively slower than airborne surveys. It depends on targets of interest, time, budget, and manpower available by which a method or combination of methods will be chosen. A combination of different methods is useful to obtain a detailed understanding of the subsurface resistivity distribution.  相似文献   

Methodische Verbesserungen bei der routinemäßigen Schlämmanalyse von Ton- und Bodenproben     

Bernhard Mattiat 《Contributions to Mineralogy and Petrology》1964,10(2):216-224

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Stabilität einer Rutschscholle unter Einstau     

Bernhard Albiker 《Rock Mechanics and Rock Engineering》1977,9(4):173-181

ZusammenfassungStabilität einer Rutschscholle unter Einstau Die Elta, linker Seitenzufluß der Donau auf der Höhe Tuttlingen, sollte an der topografisch günstigsten Stelle zur Errichtung eines 12 Mio m³ großen Speichers abgesperrt werden. Die geologische Vorerkundung ergab Hinweise auf eine erfolgte Rutschung größerer Kubatur im linken Hangbereich. Die danach angesetzte Erkundung zeigte, daß eine Scholle aus Gesteinen des Weißen Jura unter Ausbildung einer Gleitfläche auf dem unterlagernden Braunen Jura abgeglitten war. Mit dem Teileinstau dieser Hangpartie mußte befürchtet werden, daß die Scholle erneut in Bewegung geraten und in das Becken gleiten würde (Vergleichssituation zu Vajont). Die bodenmechanische Berechnung ergab für den Lastfall der schnellen Senkung des Beckenspiegels eine nicht ausreichende Standsicherheit der Scholle, weshalb die Sperrstelle aufgegeben werden mußte.

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SummaryStability of a Rock Slide in a Reservoir The Elta, left tributory river of the upper Danube should have been dammed up at the topographically most suitable location in order to erect a reservoir for water supply of 12 mio. m³ in volume. Since the topography of the valley part in consideration showed some peculiarities, a more detailed geological survey was undertaken. Due to geo-morphological aspects on the left slope part of the valley expecially in the area of the dam abutment in prospection a former landslide was indicated. More detailed ascertainments showed that a stratum of malm had performed a slideway on the dogger yielding the actual morphological position.In projecting the basin it had to be taken into consideration the possibility of a renewed sliding expecially in the state of lowering the water table (comparative situation to Vajont).Indeed the soil mechanical safety determination of the slope part in consideration verified a not sufficient stability in the state of repeated sudden drow down of the water table in the basin. Due to this result one had to renounce on the realization of the project.

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RésuméStabilité d'un éboulement dans un bassin On devait construire un barrage sur la Elta (affluent gauche du Danube, à la hauteur de Tuttlingen), à l'endroit le plus favorable du point de vue topographique, afin de créer un réservoir de 12 Mio. m³. Le sondage géologique préalable a fourni des indications au sujet d'un glissement de cubage assez important, s'étant produit dans la région pentue gauche.Le sondage effectué par la suite montra qu'une masse de pierres du Jura Blanc s'était détachée en ferment une surface glissante sur le Jura Brun qui se trouve à la base. Avec le remplissage du bassin partiel il était à craindre que la masse ne se mît de nouveau en mouvement et ne glissât dans le bassin (Situation comparable à Vajont).Les calculs de la mécanique du sol n'ont pas révélé une sécurité suffisant de la stabilité de la masse, dans le cas d'une baisse rapide du niveau du bassin, c'est pourquoi on a dû renoncer à un barrage à cet endroit.

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Ammoniten-Ökologie am Beispiel des Oberjura     

Prof. Dr. Bernhard Ziegler 《International Journal of Earth Sciences》1967,56(1):439-464

Zusammenfassung In vielen Fällen beeinflussen äußere Faktoren das Vorkommen der Ammoniten. Im Oberjura spielt die Wassertiefe eine große Rolle, daneben tritt die Wassertemperatur. Voraussetzungen der ökologischen Analyse sind bodenbezogenes Leben der Tiere und postmortale Autochthonie der Schalen. Methoden und Fehlerquellen werden besprochen. Aus der ökologischen Bindung vieler Ammoniten ergeben sich Folgen, vor allem für Stratigraphie, Phylogenie und Ontogenie.

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In many cases external factors determine the occurence of the ammonites. In the Upper Jurassic the depth of the sea is of great importance, as well as the temperature of the water. Ecological analysis requires life of the animals close to the sea floor, and that the shells are autochthonous.Methods and sources of errors are discussed. The dependence on environment of many ammonites has consequences, especially for stratigraphy, phylogeny and ontogeny.

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Résumé Souvent des facteurs extérieurs déterminent la présence des ammonites. Dans le Jurassique Supérieur la profondeur de la mer joue un grand rôle, aussi bien que la température de l'eau. L'analyse écologique doit supposer que les animaux vivent près du fond de la mer et que les coquilles sont autochtones. Les méthodes et les sources d'erreurs sont discutées. La dépendance des ammonites de leur milieu a des conséquences avant tout pour la stratigraphie, la phylogénie et l'ontogénie.

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