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Browsing Fakultet for naturvitenskap og teknologi by Title
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Dahle, Peter (Master thesis; Mastergradsoppgave, 15-Jun-2007)[+][-]
Abstract: Several actors are involved in all layers the handset architecture, from hardware producers to service providers, and the numbers are raising. Lack of collaboration amongst these actors across and within layers has led to a complex development-process of services and applications, which in turn leads to difficult use of such applications and services. In this thesis we took a closer look at the mobile phone, examined challenges surrounding development and use of services on mobile phones, and found initiatives by actors to handle these challenges. This knowledge was used to design and implement a solution to handle identified challenges. The solution involves using the UICC as the main application platform and container of state, with the possibility to deploy handset-specific parts of an application on the handset. Standardized tools on the handset give UICC-applications the means to communicate with external processes and users. In addition the network operator is given an important role to administrate and adapt applications on the UICC as services change communication technology and application standard. The designed architecture facilitates more widespread development and use of services on the mobile handset. The architecture is realizable through current platforms and standards. By implementing a simulation and subset of our design on a handset the design was substantiated. URI: http://hdl.handle.net/10037/1136 File(s) in this item: 2
thesis.pdf (2.060Mb)thesis.zip (2.343Mb) -
Blair, Gordon S.; Yang, Jie; Andersen, Anders (Research report; Forskningsrapport, 2005)[+][-]
Abstract: It is becoming clear that modern middleware platforms must provide both deploy-time configuration and run-time reconfiguration to accommodate rapid changing requirements and also to be able to operate in dynamic environments. J2EE is a key example of a middleware architecture that supports enterprise applications via its Enterprise JavaBeans (EJB) component model. EJB provides limited configurability in terms of a fixed set of non-functional middleware services at deployment-time (via a declarative deployment descriptor). However, EJB along with other related enterprise architectures generally do not provide enough support for re-configuration or evolution. At best, there is limited support in some platforms for replacing or updating particular services. This paper discusses the design of configurable and re-configurable middleware architecture and also the key role of separation of concerns for such platforms. The paper also describes the Arctic Beans component model which uses the Composition Filters model to capture such concerns and also support their safe composition.The paper also explains how this model can be used to construct an Arctic Beans container, in the style of EJB. The main contribution of the paper is to demonstrate that adaptable middleware platform can be developed using separation of concern technologies, specifically the composition filters model. URI: http://hdl.handle.net/10037/396 File(s) in this item: 1
report.pdf (335.0Kb) -
Zamelczyk, Katarzyna Agnieszka (Doctoral thesis; Doktorgradsavhandling, 11-May-2012)[+][-]
Abstract: The aim of the PhD study was to use planktic foraminifera to elucidate paleoceanographic variability and the preservation state of calcium carbonate in the eastern Fram Strait throughout the last 30,000 years. Sediment cores were studied using a multiproxy approach which included analyzing planktic and benthic foraminiferal fauna distribution patterns, measurements of stable isotopes (δ18O, δ13C), grain size analysis, IRD counts, and chemical analysis of bulk sediment. In addition, mean shell weight records combined with fragmentation indices were applied. Three time periods representing important oceanographic changes in the Fram Strait were investigated with a high temporal resolution. The results show that the Atlantic water inflow governed the oceanographic development and had an important influence on the preservation state of calcium carbonate in the Fram Strait. The best preserved planktic foraminifera assemblages during the last 30,000 years were found during the Last Glaciation Maximum. Some minor dissolution events occurred during the Last Glacial Maximum as response to seasonally changing physical oceanographic parameters, sea ice formation, increased surface productivity, and melt water pulses. During the deglaciation and the Holocene, the preservation state of carbonates generally deteriorated. This trend was interrupted at 10,800-8000 BP, where the preservation of planktic foraminifera markedly improved. Changes in preservation are related to the extent and influence of the Arctic water and the marginal ice zone (MIZ) and its associated high organic productivity in the surface waters. During the last century, the preservation of small subpolar species improved. This coincided with distinctly increased sedimentation rates in the eastern and central Fram Strait. This study of planktic foraminifera preservation has shown that carbonate dissolution is a common phenomenon in the Fram Strait and should be considered in paleoreconstructions based on planktic foraminifera fauna. Description: The papers of this thesis are not available in Munin:
1. Zamelczyk, K., Rasmussen, T.L, Husum, K., Haflidason, H., de Vernal, A., Ravna, E.K., Hald, M. and Hillaire-Marcel, C.: 'Between two oceanic fronts : Paleoceanographic changes and calcium carbonate dissolution in the central Fram Strait during the last 20,000 years' (manuscript in revision for Quaternary Research).
2. Zamelczyk, K., Rasmussen, T.L., Husum, K. and Hald, M.: 'Marine calcium carbonate preservation vs. climate change over the last two millennia in the Fram Strait : implications for planktic foraminiferal paleostudies' (manuscript submitted to Marine Micropaleontology).
3. Zamelczyk, K., Husum, K., Rasmussen, T.L., Godtliebsen, F. and Hald, H.: 'Surface water conditions and calcium carbonate preservation in the Fram Strait during the late Weichselian 29,000-16,000 years BP', (manuscript to be submitted to Paleooceangraphy).
4. Spielhagen, R. F.,Werner, K., Aagaard-Sørensen, S., Zamelczyk, K., Kandiano,E., Budeus, G., Husum, K., Marchitto, T., and Hald, M.: 'Enhanced modern heat transfer to the Arctic by warm Atlantic Water', Science (2011), vol. 331 no. 6016:450-453. Available at http://dx.doi.org/10.1126/science.1197397
5. Werner, K., Spielhagen, R.F., Bauch, D., Hass, H.Ch., Kandiano, E. and Zamelczyk, K.: 'Atlantic Water advection to the eastern Fram Strait- Multiproxy evidence for late Holocene variability', Palaeogeography, Palaeoclimatology, Palaeoecology (2011), vol. 308 no. 3-4:264-276. Available at http://dx.doi.org/10.1016/j.palaeo.2011.05.030URI: http://hdl.handle.net/10037/4148 File(s) in this item: 1
thesis.pdf (948.6Kb) -
Hall, Chris; Manson, Alan; Meek, Chris; Chshyolkova, Tatyana; Xu, X.; Aso, Takehiko; Drummond, J. R.; Hocking, Wayne; Jacobi, Ch.; Tsutsumi, Masaki; Ward, W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)[+][-]
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Eriksen, Dan Peder (Master thesis; Mastergradsoppgave, 01-Jun-2007)[+][-]
Abstract: With the emergence of the internet and e-commerce in the 90’s new common problems arose when developing applications that span the internet. These common problems include among others scalability, robustness, networking, database usage and heterogeneity. Software developers creating internet applications saw themselves reinventing the wheel repeatedly. This lead to the creation of middleware systems that aimed to solve these common problems. This thesis will present Argos which uses a different way of building middleware systems. Argos is able to provide tailored, flexible and extensible middleware support using reflection, dependency injection, Java Management Extensions (JMX) notifications and hot deployment. The result is a platform capable of tackling domain specific challenges. It provides rapid development of feature rich applications for managing and processing information. Argos has gone through thorough testing proving production stability. URI: http://hdl.handle.net/10037/1138 File(s) in this item: 1
thesis.pdf (1.599Mb) -
Grineviciute, Laima (Master thesis; Mastergradsoppgave, 08-Jun-2012)[+][-]
Abstract: Attempted syntheses of 1,3,4,6-tetrasubstituted-2,5-diketopiperazines using microwave assisted heating URI: http://hdl.handle.net/10037/4379 File(s) in this item: 1
thesis.pdf (2.043Mb) -
Arild, Ronny; Stabell-Kulø, Tage (Research report; Forskningsrapport, 18-Jan-1999)[+][-]
Abstract: A distributed file repository is described. It supports interaction between different machines used by a single user, as well as between users that share data. Files can be replicated and consistency will be maintained, or files can be shipped (copied) to a remote site. As with more traditional systems, the servers are trusted not to leak information. However, the rôle servers play is not as much the hub in the system. In particular, users are in charge of delegating acccess to files. For flexibility, delegations might take place outside of the realm of the system proper; by any means available to the users. Users can delegate access rights to local and remote users, including remote users in other domains. ACLs are used to maintain local access control; capabilities are used to access remote files. These capabilities are valid within epochs, but are immediately revoked when being used, thus being valid at-most-once. In essence, we have realized a flexible infrastructure where users can implement their own security policy. URI: http://hdl.handle.net/10037/360 File(s) in this item: 1
report.pdf (261.1Kb) -
Evertsen, Martin Hætta (Master thesis; Mastergradsoppgave, Jun-2010)[+][-]
Abstract: People love to take images, but are not so willing to annotate the images af-terwards with relevant tags. Manually tagging images is both subjective (dependent on annotator) and time consuming. It would be nice if the tag-ging process could be done automatically. A requirement for effective searching and retrieval of images in rapid growing online image databases is that each image has accurate and useful annotation. This thesis shows that automatic tagging of images with relevant tags is possible by using a combination of the capture location, the date/time when the image was captured and an image category. The use of image categories (together with location and date/time) ensures that many relevant tags are returned and restrict the occurrence of noisy tags to a very low level despite using a noisy image database (Flickr). Other methods used for further re-stricting noise are to restrict usage of more than one image from same user (as basis for tagging the query image) and a dynamic approach for using many images when possible, and fewer images when not many relevant im-ages are found. The designed system is able to tag an image as long as there are a sufficient number of geo-referenced and already tagged images that is relevant for the query image available on Flickr. The query image must also have been geo-referenced and it is assumed that the user provides an image category. Im-ages are processed based on which category the images belongs to, i.e. an image is processed with the best method to handle images belonging to that specific category. In short, this means that images of objects or places are processed differently than images from events. The evaluation of the system indicates that usage of image categories is very helpful when tagging images. The system finds more relevant tags and fewer noisy tags than baseline systems using only location. It also performs good compared to a system using both location and content-based image analysis. URI: http://hdl.handle.net/10037/2633 File(s) in this item: 1
thesis.pdf (2.347Mb) -
Sivertsen, Agnar Holten (Doctoral thesis; Doktorgradsavhandling, 11-Nov-2011)[+][-]
Abstract: The manual trimming and inspection of cod fillets by candling, is considered the bottleneck of cod fillet processing. The operation is both labour intensive and expensive, reported to account for as much as 50 % of the cost with cod fillet production. Due to the high labour costs in Norway, it is of great interest for the industry to optimize this process. In this work a hyperspectral imaging system has been developed, capable of inspecting cod fillets, with or without skin, at a conveyor belt speed of 400 mm/seconds, corresponding to the industrial processing speed of one fish per second. The system is designed as proof of concept, and the algorithms are not implemented to be run in real time. A method for segmenting a cod fillet image into the respective parts: loin, belly and tail, using the centerline as a reference system, has been developed. The method is useful for selecting standardized measurement regions on the fillet, and used for extracting data for automatic freshness assessment. Freshness, as days on ice, can be predicted using spectroscopy in part of the visible region (450-700 nm). This can be done with an accuracy comparable to what is reported for sensory evaluation using a panel of trained evaluators. The same system is used for detecting fillets which have been previously frozen, both as whole fish and as fillets with skin. The results show a complete separation between the fresh and frozen-thawed samples. Similar mechanisms are affecting the spectra from fish stored fresh on ice, and fish that has been through the freeze-thaw cycle. The main variations seen in the spectra from cod fillets stored on ice, or frozen and then thawed, are due to oxidation of heme proteins in the muscle. This is supported by independent measurements using two different instruments, and by previous studies pointing to the visible region as the best region for freshness prediction. Detectingobjectsembeddedintissue, usingvisiblelight, isdifficultduetovariability in the optical properties of the surrounding tissue. A method for calibrating the spectral signature from small objects embedded in translucent material has been developed. This method uses the estimated local background spectrum to calibrate the hyperspectral image, and the method is evaluated for automatic nematode detection, using the hyperspectral imaging system, at a commercial cod fillet processing plant. The local calibration method is superior to using traditional spectroscopic pre-treatment methods, and reduces both spatial and spectral variations across the image. The results from the industrial test show that the system can detect nematodes in cod fillets with a performance which is comparable or better, to what is reported by manual inspection. Description: The papers of this thesis are not available in Munin:
1. A. H. Sivertsen, C. Chu, L. Wang, F. Godtliebsen, K. Heia and H. Nilsen: 'Ridge detection with application to automatic fish fillet inspection', Journal of Food Engineering (2009), vol. 90, pp. 317–324. Available at http://dx.doi.org/10.1016/j.jfoodeng.2008.06.035
2. A. H. Sivertsen, K. Heia, S. K. Stormo, E. Elvevoll and H. Nilsen: 'Automatic nematode detection in cod fillets (Gadus Morhua) by transillumination hyperspectral imaging', Journal of Food Science (2011), vol. 76, pp. 77-83. Available at http://dx.doi.org/10.1111/j.1750-3841.2010.01928.x
3. A. H. Sivertsen, K. Heia, K. Hindberg and F. Godtliebsen: 'Automatic nematode detection in cod fillets (Gadus Morhua L.) by hyperspectral imaging' Journal of Food Science (2011), Volume 76, Issue 1, pages S77–S8. Available at http://dx.doi.org/10.1111/j.1750-3841.2010.01928.x
4. A. H. Sivertsen, T. Kimiya and K. Heia: 'Automatic freshness assessment of cod (Gadus morhua) fillets by VIS/NIR spectroscopy', Journal of Food Engineering (2011), vol 103, pp. 317-323. Available at http://dx.doi.org/10.1016/j.jfoodeng.2010.10.030URI: http://hdl.handle.net/10037/3681 File(s) in this item: 1
thesis.pdf (8.438Mb) -
Sivertsen, Agnar Holten; Heia, Karsten; Hindberg, Kristian; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: Detection of objects embedded in tissue, using visible light, is difficult due to light scattering. The optical properties of the surrounding tissue will influence the spectral characteristics of the light interacting with the object, and the spectral signature observed from the object will be directly affected. A method for calibrating the spectral signature of small objects, embedded in translucent material, by the estimated local background spectrum is presented. The method is evaluated under industrial conditions in a new hyperspectral imaging system for automatic detection of nematodes in cod fillets. The system operates at a conveyor belt speed of 400 mm/s which meets the industrial required speed of assessing one fillet per second. The local calibration method reduces the number of spectra needed to be classified by 89.6%. For one or more false alarms in 60% of the fillets sampled after the trimming station, the Gaussian maximum likelihood classifier detects 70.8% and 60.3% of the dark and pale nematodes, respectively. This is better than what is previously reported using a higher resolution instrument on a slow moving conveyor belt, and comparable or better to what is reported for manual inspection under industrial conditions. URI: http://hdl.handle.net/10037/4571 File(s) in this item: 1
article.pdf (1.170Mb) -
Zortea, Maciel; Skrøvseth, Stein Olav; Schopf, Thomas Roger Griesbeck; Kirchesch, Herbert M.; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Accurate detection of the borders of skin lesions is a vital first step for computer aided diagnostic systems. This paper presents a novel automatic approach to segmentation of skin lesions that is particularly suitable for analysis of dermoscopic images. Assumptions about the image acquisition, in particular, the approximate location and color, are used to derive an automatic rule to select small seed regions, likely to correspond to samples of skin and the lesion of interest. The seed regions are used as initial training samples, and the lesion segmentation problem is treated as binary classification problem. An iterative hybrid classification strategy, based on a weighted combination of estimated posteriors of a linear and quadratic classifier, is used to update both the automatically selected training samples and the segmentation, increasing reliability and final accuracy, especially for those challenging images, where the contrast between the background skin and lesion is low. URI: http://hdl.handle.net/10037/3975 File(s) in this item: 1
article.pdf (6.131Mb) -
Nesse, H.; Rietveld, Michael T.; Heinrich, D.; Williams, B.; Hoppe, U.-P.; Stadsnes, J.; Singer, W.; Blum, U.; Sandanger, M. I.; Trondsen, E. (Journal article; Tidsskriftartikkel; Peer reviewed, 28-May-2008)[+][-]
Abstract: Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya and near Tromsø in Norway gives us an opportunity to test the different theories applied to high latitude sporadic sodium layers. We use the ALOMARWeber sodium lidar to monitor the appearance and characteristics of a sporadic sodium layer that was observed on 5 November 2005. We also monitor the temperature to test the hypotheses regarding a temperature dependent mechanism. The EISCAT Tromsø Dynasonde, the ALOMAR/UiO All-sky camera and the SKiYMET meteor radar on Andøya are used to test the suggested relationships of sporadic sodium layers and sporadic E-layers, electron precipitation, and meteor deposition during this event. We find that more than one candidate is eligible to explain our observation of the sporadic sodium layer. URI: http://hdl.handle.net/10037/2417 File(s) in this item: 1
article.pdf (635.6Kb) -
Arntzen, Ingar Mæhlum (Master thesis; Mastergradsoppgave, 02-Dec-2009)[+][-]
Abstract: This thesis describes the design and implementation of a proxy client for a chain replicated storage system. URI: http://hdl.handle.net/10037/2361 File(s) in this item: 1
thesis.pdf (2.632Mb) -
Thon, Kevin (Master thesis; Mastergradsoppgave, 22-Jun-2007)[+][-]
Abstract: This thesis discusses some of the many techniques for performing blind source separation. Its focus is on the theoretical concepts that allow for the problem to be solved. It starts with presenting the EM algorithm, which is the method underpinning many of the algorithms that are presented later in the thesis. Some of the established methods are presented, and we proceed to devolop source separation algorithms based upon modelling the sources as scale mixtures of Gaussians. Such models are particularly well suited at modelling the super-Gaussian probability densities that characterise many real world signals, speech being perhaps the most commom. When evaluating the performance of the algorithms in this thesis, our focus is mainly on the quality of separation, and discussions on computational efficiency are mostly superficial. We find that in particular one of the algorithms we have constructed shows promise. Its performance is on par with existing methods, and further examination of its properties might be in order. URI: http://hdl.handle.net/10037/1100 File(s) in this item: 1
thesis.pdf (954.2Kb) -
Pettersen, Ørjan (Master thesis; Mastergradsoppgave, 25-Jun-2010)[+][-]
Abstract: This thesis covers the design, implementation and evaluation of a configuration tool for process oriented Unmanned Aerial Vehicle (UAV) programming. In addition it will examine if and how a process network can be used to control sensors and communication channels on an UAV in flight. NORUT-IT is currently developing a sensor platform based on UAVs. The mission computer software they have at the moment have room for improvement when it comes down to issues regarding routing and prioritizing between available network connections. One issue that has been identified is not being able to route between multiple available networks. They have to predefine which network connection the UAV should use to connect to the ground station when it is in flight. It will use this connection the entire flight even if a faster and/or cheaper network connection is available in some areas of the mission. Together with this issue, having a platform with a number of sensors working together, will be challenging to configure and might require programming skills to some degree to set up correctly. Communicating sequential processing(CSP) have properties that can help in building concurrent, reliable and scalable programs. By using CSP and a process configuration tool, the complexity of configuring the mission computer of an UAV can be reduced. The implementation will demonstrate a tool that are believed to be intuitive and will lower the challenge of configuring a process network intended to control the sensors and communication channels on an UAV. The process network creator tool have a graphical interface and a collection of premade CSP processes. It will also have the ability to convert the graphical representation of the process network into a running CSP process. URI: http://hdl.handle.net/10037/2722 File(s) in this item: 1
thesis.pdf (3.511Mb) -
Hansen, Christer Andre (Master thesis; Mastergradsoppgave, 18-May-2010)[+][-]
Abstract: Accessing route information should be easy. Today, most collective transport companies distribute timeta- bles online as electronic documents and in paper format. These solutions are outdated and cumbersome to use. However, systems have been built to make the task of finding route information easy, and to replace these formats. Most of these systems, still, have limitations. They rely on users knowing the name of the bus stops, and the destination is left out when finding information. In this thesis we present a system that is able to find travel alternatives based on two parameters, the user’s current location and the destination. Successful tests and experiments have proved that our system can be useful for people that does not know the following; the name of the bus stops, where the bus stops are located, what route to use, and where to get of the bus. We also suggest an architecture where our system is integrated as part of a personal cloud. URI: http://hdl.handle.net/10037/2604 File(s) in this item: 1
thesis.pdf (7.253Mb) -
Hanssen, Øyvind (Research report; Forskningsrapport, Dec-2005)[+][-]
Abstract: In this report we define the semantics of a language for dynamic QoS expressions which can be evaluated at run-time for conformance. We define how expressions can be constructed from atomic expressions termed ’basic profiles’ using composition operators. Two such operators are defined: The sum ( ’+’ ) which corresponds to simple conjunction and component-sum (’Å’) which assume that the operands denote properties of separate environments and therefore must be satisfied separately. Based on those, algorithms for conformance checking any pair of expressions can be developed. Concrete models are typically defined for specific application domains, they define the basic profile space and explicitly establishes conformance relationships between basic profiles. These are essentially sets of axioms from which we can infer conformance. Description: Publisert desember 2005, oppdatert februar 2006 / Published December 2005, updated February 2006 URI: http://hdl.handle.net/10037/383 File(s) in this item: 1
report.pdf (265.9Kb) -
A detection theoretical approach to digital communications using autoregressive process shift keyingAnfinsen, Stian Normann (Master thesis; Mastergradsoppgave, 10-Mar-2001)[+][-]
Abstract: I klassisk digital kommunikasjon overføres en bitstrøm gjennom en kanal ved å modulere parametrene til en deterministisk bærebølge. Noen kjente eksempler er amplitudemodulasjon (AM), frekvensmodulasjon (FM) og fasemodulasjon (PM). Mottakeren estimerer parametrene til det informasjonsbærende signalet og bruker en deteksjonsregel til å klassifisere den mottatte bølgeformen som en av flere mulige parametriske signaler. Konvensjonelle metoder gir ingen beskyttelse mot at ikke-autoriserte mottakere avlytter og dekoder signalet. Blant ferske metoder som tilbyr en viss beskyttelse mot avlytting finner vi såkalte spredt spektrum-teknikker og kaotiske digitale kodere. Slike teknikker krever nøyakig synkronisering mellom sender og mottaker. Selv små synkroniseringsfeil kan føre til store bitfeilrater hos mottakeren. Denne oppgaven har undersøkt et nytt konsept innen digital kommunikasjon, som er basert på å bruke realisasjoner av stokastiske prosesser som informasjonsbærende signaler. Teknikken har innebygd sikkerhet mot avlytting. Samtidig er det mulig å konstruere dekodere som er enklere enn de som brukes i spredt spektrum og kaotisk kommunikasjon. Målet med prosjektet er å undersøke noen fundamentale egenskaper ved den nye teknikken: 1) Hvordan kan vi finne et statistisk mål på avstand mellom de informasjonsbærende stokastiske prosessene? 2) Hvilken detektor skal vi bruke for å dekode informasjonssekvensen, og hvor god ytelse gir denne? 3) Hvordan skal vi velge de stokastiske prosessene? URI: http://hdl.handle.net/10037/235 File(s) in this item: 1
thesis.pdf (3.697Mb) -
Skadsem, Marte Karidatter (Master thesis; Mastergradsoppgave, 08-Jun-2006)[+][-]
Abstract: In this thesis we present the development of a distributed and parallel environment which offers functionality to robots to support them in their task performance. We want the environment to be a framework where students can experiment with robots, and in which we can arrange robot competitions. Our motivation for this thesis is an earlier developed robot system at our department. It was used as an instrument to demonstrate the principles and practice of distributed and high performance parallel computing. The system was used by students on advanced courses on cluster architecture and programming, and popular competitions were held in it. The old system had many infrastructure demands and had to be closed. We want to make a new system that has less infrastructure demands and more functionality. The environment has control over a certain amount of work space where the robots can operate. Within this work space, the environment offers functionality that includes context awareness, location, mapping, naming, and structured interfaces for interaction between the different components. Users can control the robots through the environment, and they assign tasks to the robots. Users can also download extensions to robots through the environment, and robots can upload data to the environment. The state of the environment, the robots and the work space is visualized on a display wall. Users can interact with this visualization and assign simple tasks through it. URI: http://hdl.handle.net/10037/1009 File(s) in this item: 1
thesis.pdf (1.883Mb) -
Vevik, Kristine (Master thesis; Mastergradsoppgave, 15-Jun-2011)[+][-]
Abstract: A widespread bottom-simulating reflection (BSR) defining the base of the gas hydrate stability zone (BGHSZ) exists on seismic data from the western Svalbard margin, including the Vestnesa Ridge, which is a mounded and elongated sediment drift NW of Svalbard to the north of the Molloy Transform. The BSR stretches from the continental slope to within few km of the mid-oceanic ridge system thereby shoaling due to an increase in heat flow over the juvenile oceanic crust, which cools off in eastward direction. The interpretation of a BSR leads to the subdivision into three regions based on distribution and geological setting, namely the Vestnesa Ridge, the continental slope and the Molloy Transform Fault (MTF), where potential gas hydrate occurrences comprise an area of ~2700 km2. The BSR occurrence and inferred hydrate accumulation zone is bound by impermeable glacial debris-flow (GDF) deposits on the upper continental slope, the Knipovich Ridge and MTF to the south and the Molloy Ridge to the west. Enhanced reflections beneath the BSR indicate the presence of significant amounts of free gas. The crest of the Vestnesa Ridge at water depth between 1200-1500 m is pierced with fluid-flow features, but they are absent on the flanks of the ridge, where hydrate-bearing sediments effectively reduce the permeability of the sediments. Thus, fluids are forced to migrate laterally upwards along the GHSZ towards the crest in this topographically controlled system. The vigorous flow of fluids at the crest disrupts the BSR, causing it to shoal locally in vicinity of fluid-flow features. The fluid-flow features are often connected to deep-seated faults indicating a deep hydrocarbon gas supply, which is corroborated by hydrate-stability modeling suggesting a larger fraction of thermogenic hydrocarbons involved in hydrate formation. In addition to that, the combination of high heat flow, tectonic activity, a thick sedimentary cover and a shallow maturation window suggests that the free-gas/gas-hydrate system at the Vestnesa Ridge is more active and dynamic than elsewhere in the study area. Free-gas/gas-hydrate systems on the lower continental slope and at the MTF seem mostly in a steady state with gas predominantly originating from biogenic methanogenesis. URI: http://hdl.handle.net/10037/3474 File(s) in this item: 1
thesis.pdf (6.956Mb)
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