NCR-days 2008 : 10 years NCR: November 20-21

De verschillende subthema’s van de NCR-dagen 2008, (i) Stroomgebied en Overstromingsrisico management (ii) Hydrologie en (iii) Geomorfodynamica en Morfologie, dekken een groot gedeelte van het hedendaagse onderzoek dat in Nederland op rivierkundig gebied wordt uitgevoerd

Proceedings of the second "international Traveling Workshop on Interactions between Sparse models and Technology" (iTWIST'14)

The implicit objective of the biennial "international - Traveling Workshop on Interactions between Sparse models and Technology" (iTWIST) is to foster collaboration between international scientific teams by disseminating ideas through both specific oral/poster presentations and free discussions. For its second edition, the iTWIST workshop took place in the medieval and picturesque town of Namur in Belgium, from Wednesday August 27th till Friday August 29th, 2014. The workshop was conveniently located in "The Arsenal" building within walking distance of both hotels and town center. iTWIST'14 has gathered about 70 international participants and has featured 9 invited talks, 10 oral presentations, and 14 posters on the following themes, all related to the theory, application and generalization of the "sparsity paradigm": Sparsity-driven data sensing and processing; Union of low dimensional subspaces; Beyond linear and convex inverse problem; Matrix/manifold/graph sensing/processing; Blind inverse problems and dictionary learning; Sparsity and computational neuroscience; Information theory, geometry and randomness; Complexity/accuracy tradeoffs in numerical methods; Sparsity? What's next?; Sparse machine learning and inference.Comment: 69 pages, 24 extended abstracts, iTWIST'14 website: http://sites.google.com/site/itwist1

Scientific drilling projects in ancient lakes: integrating geological and biological histories

Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information, e.g., through molecular dating of molecular phylogenies. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets for creating an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep drilling projects

Seismic imaging of crustal structure at mid-ocean ridges: a three-dimensional approach

Over recent years geological, geochemical and geophysical surveys of mid-ocean ridges have revealed a significant degree of along-axis variability not only in seabed morphology, but also in crustal structure, particularly Numerous geophysical surveys of the Valu Fa Ridge, southwest Pacific, have mapped the extent of an axial mid-crustal reflector. This reflector has been interpreted as representing the top of a sill-like melt lens, comprising a high percentage of partial melt, lying at the top of a crustal magma chamber. In 1995, a controlled-source, wide-angle seismic dataset was acquired at the Valu Fa Ridge during RN Maurice Ewing cruise EW9512, to investigate the mid-deep crustal structure at this ridge, and particularly the crustal magma chamber associated with the melt lens beneath the ridge axis. The EW9512 acquisition geometry was primarily two-dimensional in design, and modelling of these 2-D profiles revealed the presence of an axial low velocity zone beneath the melt lens. This low velocity zone is thought to represent a region of crystal mush comprising a much lower percentage of partial melt than is present in the overlying melt lens. Similar structures have been modelled beneath a number of other mid-ocean ridges. The primary aim of this study was to build on this 2-D interpretation by taking advantage of three-dimensional ray coverage in the axial region in order to assess the along-axis continuity of the magmatic system, correlate this to any ridge segmentation apparent in the seabed morphology, and determine if ridge segmentation is related to the magma supply. The 3-D data were analysed using a tomographic inversion technique. The inversion results suggest that the axial low velocity zone may be segmented on a scale of 5-10 km, which correlates with the morphological segmentation of the ridge crest and is believed to reflect episodic magma supply with different ridge segments at different stages of a cycle of magmatic and amagmatic extension. However, three- dimensional ray coverage is not ideal owing to the dominantly 2-D acquisition geometry. Therefore a detailed assessment of data uncertainty and resolution was undertaken to enable a meaningful interpretation of the inversion results in terms of which features have a geological origin and which are artefacts of the inversion process. P-S mode converted arrivals arising from mid-crustal interfaces were also modelled in order to obtain improved geological constraints on the crustal structure than is possible from P-wave studies alone. This modelling indicates that the uppermost crust is pervaded by thin cracks. In addition, techniques were developed for modeling the polarisation of 5-wave arrivals with low signal strength. Application of these methods suggests that the thin cracks have a preferred orientation parallel to the ridge crest on-axis, and oblique to the ridge crest off-axis which is thought to reflect the pattern of southward propagation of the ridge system inferred from regional tectonic and bathymetric studies. Modelling of P-S mode converted arrivals arising from conversion at the top of the melt lens provided additional constraints on the properties of the melt lens. In conjunction with the 3-D tomographic results, this work suggests that the southernmost ridge segment in the study area has recently become magmatically active following a period of amagmatic extension suggested by its morphology, thus providing evidence for episodic melt supply at this ridge. As part of the suggestions for further work, a theoretical investigation of survey resolution was undertaken to test commonly adopted acquisition geometries with a view to optimising the design and cost-effectiveness of future 3-D controlled-source tomographic experiments

Global Monitoring for Security and Stability (GMOSS) - Integrated Scientific and Technological Research Supporting Security Aspects of the European Union

This report is a collection of scientific activities and achievements of members of the GMOSS Network of Excellence during the period March 2004 to November 2007. Exceeding the horizon of classical remote-sensing-focused projects, GMOSS is characterized by the integration of political and social aspects of security with the assessment of remote sensing capabilities and end-users support opportunities. The report layout reflects the work breakdown structure of GMOSS and is divided into four parts. Part I Concepts and Integration addresses the political background of European Security Policy and possibilities for Earth Observation technologies for a contribution. Besides it illustrates integration activities just as the GMOSS Gender Action Plan or a description of the GMOSS testcases. Part II of this book presents various Application activities conducted by the network partners. The contributions vary from pipeline sabotage analysis in Iraq to GIS studies about groundwater vulnerability in Gaza Strip, from Population Monitoring in Zimbabwe to Post-Conflict Urban Reconstruction Assessments and many more. Part III focuses on the research and development of image processing methods and Tools. The themes range from SAR interferometry for the measurement of Surface Displacement to Robust Satellite Techniques for monitoring natural hazards like volcanoes and earthquakes. Further subjects are the 3D detection of buildings in VHR imagery or texture analysis techniques on time series of satellite images with variable illumination and many other more. The report closes with Part IV. In the chapter ¿The Way Forward¿ a review on four years of integrated work is done. Challenges and achievements during this period are depicted. It ends with an outlook about a possible way forward for integrated European security research.JRC.G.2-Support to external securit

Visual Techniques for Geological Fieldwork Using Mobile Devices

Visual techniques in general and 3D visualisation in particular have seen considerable adoption within the last 30 years in the geosciences and geology. Techniques such as volume visualisation, for analysing subsurface processes, and photo-coloured LiDAR point-based rendering, to digitally explore rock exposures at the earth’s surface, were applied within geology as one of the first adopting branches of science. A large amount of digital, geological surface- and volume data is nowadays available to desktop-based workflows for geological applications such as hydrocarbon reservoir exploration, groundwater modelling, CO2 sequestration and, in the future, geothermal energy planning. On the other hand, the analysis and data collection during fieldwork has yet to embrace this ”digital revolution”: sedimentary logs, geological maps and stratigraphic sketches are still captured in each geologist’s individual fieldbook, and physical rocks samples are still transported to the lab for subsequent analysis. Is this still necessary, or are there extended digital means of data collection and exploration in the field ? Are modern digital interpretation techniques accurate and intuitive enough to relevantly support fieldwork in geology and other geoscience disciplines ? This dissertation aims to address these questions and, by doing so, close the technological gap between geological fieldwork and office workflows in geology. The emergence of mobile devices and their vast array of physical sensors, combined with touch-based user interfaces, high-resolution screens and digital cameras provide a possible digital platform that can be used by field geologists. Their ubiquitous availability increases the chances to adopt digital workflows in the field without additional, expensive equipment. The use of 3D data on mobile devices in the field is furthered by the availability of 3D digital outcrop models and the increasing ease of their acquisition. This dissertation assesses the prospects of adopting 3D visual techniques and mobile devices within field geology. The research of this dissertation uses previously acquired and processed digital outcrop models in the form of textured surfaces from optical remote sensing and photogrammetry. The scientific papers in this thesis present visual techniques and algorithms to map outcrop photographs in the field directly onto the surface models. Automatic mapping allows the projection of photo interpretations of stratigraphy and sedimentary facies on the 3D textured surface while providing the domain expert with simple-touse, intuitive tools for the photo interpretation itself. The developed visual approach, combining insight from all across the computer sciences dealing with visual information, merits into the mobile device Geological Registration and Interpretation Toolset (GRIT) app, which is assessed on an outcrop analogue study of the Saltwick Formation exposed at Whitby, North Yorkshire, UK. Although being applicable to a diversity of study scenarios within petroleum geology and the geosciences, the particular target application of the visual techniques is to easily provide field-based outcrop interpretations for subsequent construction of training images for multiple point statistics reservoir modelling, as envisaged within the VOM2MPS project. Despite the success and applicability of the visual approach, numerous drawbacks and probable future extensions are discussed in the thesis based on the conducted studies. Apart from elaborating on more obvious limitations originating from the use of mobile devices and their limited computing capabilities and sensor accuracies, a major contribution of this thesis is the careful analysis of conceptual drawbacks of established procedures in modelling, representing, constructing and disseminating the available surface geometry. A more mathematically-accurate geometric description of the underlying algebraic surfaces yields improvements and future applications unaddressed within the literature of geology and the computational geosciences to this date. Also, future extensions to the visual techniques proposed in this thesis allow for expanded analysis, 3D exploration and improved geological subsurface modelling in general.publishedVersio

Morphometric Study of Longitudinal Ridges in Long Runout Landslides on Mars, Earth, and the Moon

Long runout landslides are hypermobile landslides ubiquitous in our solar system. The exact mechanism(s) that have to be invoked in order to explain their high velocity and exceptional travel distances over nearly horizontal surfaces has yet to be successfully determined. In this thesis I focused on the distinctive longitudinal ridges that mark the surface of long runout landslide deposits in the attempt to link these morphological features and their related internal structures to the mechanisms involved during the emplacement of such catastrophic events. I conducted a morphometric analysis of longitudinal ridges of three case studies: the Coprates Labes landslide in Valles Marineris on Mars; the El Magnifico landslide in Chile – on Earth; the Tsiolkovskiy crater landslide – on the Moon. For the first time in natural landslides, I found that the wavelength of the longitudinal ridges is consistently 2 to 3 times the thickness of the landslide deposit, in agreement with experimental work on rapid granular flows. The recurrence of the scaling relationship suggests a scale- and environment-independent mechanism. Therefore, I concluded that the existence of longitudinal ridges in long runout landslides cannot be used to infer the presence of specific lithologies forming the basal surface; nor environmental and climatic conditions at the time of landslide emplacement. Based on the agreement between the results obtained from my morphometric analysis and the laboratory experiments on rapid granular flows, I proposed that longitudinal ridges in long runout landslides are imparted by high-speed granular flow convection mechanisms. In order to ground truth such hypothesis, I conducted field work at the terrestrial El Magnifico landslide and studied the internal structures of the deposit and their relationship with the longitudinal ridges. I concluded that evidence cannot rule out a convection-style mechanism observed in laboratory experiments of granular flows but is also not equivocal in its support. I advanced an alternative hypothesis that longitudinal ridges may have formed by a mechanism that involves pattern-forming vibrations. Such proposed mechanism supports the existence of heterogeneous stress distribution and stress fluctuation within long runout landslide deposits, which are considered the hallmark of acoustic fluidization. I suggested the use of the scaling relationship between the wavelength of longitudinal ridges and the thickness of the deposit as a tool to infer the thickness of landslide deposits where its calculation is not otherwise possible using typical methods in geomorphology. I applied this novel idea to the Light Mantle landslide, Taurus-Littrow valley, at the Apollo 17 landing site: by calculating the representative wavelength of the longitudinal ridges I derived the thickness of its deposit, as it could not be derived through interpolation. I discussed the finding of my work within the context of the literature on frictional weakening in fault mechanics, on the similarity of weakening of shear zones in landslide and earthquake mechanics, and on the geomorphology of long runout landslide deposits. Following this, I defined a new framework under which the understanding of the formation mechanism of long runout landslides should be approached. Finally, I identified four possible directions for future work: extending the morphometric analysis of longitudinal ridges in martian double layer ejecta; investigating the importance of the roughness of the substrate in the formation of longitudinal ridges; performing friction experiments to study weakening mechanisms in lunar rock analogues; using martian long runout landslide deposits as stratigraphic markers in order to constrain the timing of geological processes