Horizontal movements in the eastern Barents Sea constrained by numerical models and plate reconstructions     

Susanne J. H. Buiter  Trond H. Torsvik 《Geophysical Journal International》2007,171(3):1376-1389

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A level-set corrector to an adaptive multiscale permeability prediction     

Inga Berre  Martha Lien  Trond Mannseth 《Computational Geosciences》2007,11(1):27-42

We consider the inverse problem of permeability estimation for two-phase porous-media flow. The novel approach is based on regularization by zonation, where the geometry and size of the regions are chosen adaptively during the optimization procedure. To achieve this, we have utilized level-set functions to represent the permeability. The available data are sparsely distributed in space; hence, it is reasonable to confine the estimation to coarse-scale structures. The level-set approach is able to alter the boundaries between regions of different permeability without strict restrictions on their shape; however, when the data are sparse, a reasonable initial guess for the permeability is required. For this task, we use adaptive multiscale permeability estimation, which has the potential of identifying main permeability variations. These are described by a piecewise constant function, where the constant values are attained on rectangular zones. In the current work, we develop a level-set corrector strategy, assuming adaptive multiscale permeability estimation as a predictor.  相似文献   

Overview,roles, and performance of the North East Atlantic fisheries commission (NEAFC)     

Trond Bjørndal 《Marine Policy》2009

According to the 1995 United Nations Fish Stocks Agreement (UNFSA), straddling fish stocks and highly migratory fish stocks are to be managed by Regional Fisheries Management Organisations (RFMOs), consisting of coastal states and relevant Distant Water Fishing Nations (DWFNs). In the North East Atlantic there are several straddling stocks, including herring, mackerel, blue whiting, redfish and numerous deep sea stocks that are exploited both within coastal states’ 200 mile Exclusive Economic Zones and on the high seas. Management of such stocks poses special management problems. In this area, the North East Atlantic Fisheries Commission (NEAFC) represents the relevant RFMO. So far the literature has devoted little attention to RFMOs in general and to NEAFC in particular. The purpose of this report is, first, to provide an overview of the organisation, structure, and objectives of NEAFC and, second, to consider its performance with regard to resource management.  相似文献   

Bayesian analysis of stage–fall–discharge models for gauging stations affected by variable backwater     

Asgeir Petersen‐Øverleir  Trond Reitan 《水文研究》2009,23(21):3057-3074

Parsimonious stage–fall–discharge rating curve models for gauging stations subject to backwater complications are developed from simple hydraulic theory. The rating curve models are compounded in order to allow for possible shifts in the hydraulics when variable backwater becomes effective. The models provide a prior scientific understanding through the relationship between the rating curve parameters and the hydraulic properties of the channel section under study. This characteristic enables prior distributions for the rating curve parameters to be easily elicited according to site‐specific information and the magnitude of well‐known hydraulic quantities. Posterior results from three Norwegian and one American twin‐gauge stations affected by variable backwater are obtained using Markov chain Monte Carlo simulation techniques. The case studies demonstrate that the proposed Bayesian rating curve assessment is appropriate for developing rating procedures for gauging stations that are subject to variable backwater. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Relation Between Level Set and Truncated Pluri-Gaussian Methodologies for Facies Representation   总被引：1，自引：1，他引：0  

Trond Mannseth 《Mathematical Geosciences》2014,46(6):711-731

Truncated Gaussian/pluri-Gaussian representations and level set representations are two methodologies for implicit representation that can be applied to large-scale subsurface structures. Identification of facies in a petroleum reservoir from dynamic well data is a common field of application for these representation methodologies. No comparison of the methodologies has appeared in the literature to date. The paper seeks to improve on this situation by comparing selected level set and truncated Gaussian/pluri-Gaussian representations in detail. Strong similarities are found, in the sense that every truncated Gaussian/pluri-Gaussian representation considered has a level set counterpart. Furthermore, the transition from a truncated Gaussian/pluri-Gaussian representation to the corresponding level set representation is easily accessible. In addition to the comparison aspect, this paper also introduces a novel level set representation—the hierarchical level set representation—that removes a difficulty present in existing level set representations in a shape estimation setting. It is shown that the hierarchical level set representation corresponds to a well-known truncated pluri-Gaussian representation.  相似文献   

Continental growth and reworking on the edge of the Columbia and Rodinia supercontinents; 1.86–0.9 Ga accretionary orogeny in southwest Fennoscandia     

Nick M.W. Roberts  Trond Slagstad 《International Geology Review》2015,57(11-12):1582-1606

Geological history from the late Palaeoproterozoic to early Neoproterozoic is dominated by the formation of the supercontinent Columbia, and its break-up and re-amalgamation into the next supercontinent, Rodinia. On a global scale, major orogenic events have been tied to the formation of either of these supercontinents, and records of extension are commonly linked to break-up events. Presented here is a synopsis of the geological evolution of southwest Fennoscandia during the ca. 1.9–0.9 Ga period. This region records a protracted history of continental growth and reworking in a long-lived accretionary orogen. Three major periods of continental growth are defined by the Transscandinavian Igneous Belt (1.86–1.66 Ga), Gothian (1.66–1.52 Ga), and Telemarkian (1.52–1.48 Ga) domains. The 1.47–1.38 Ga Hallandian–Danopolonian period featured reorganization of the subduction zone and over-riding plates, with limited evidence for continental collision. During the subsequent 1.38–1.15 Ga interval, the region is interpreted as being located inboard of a convergent margin that is not preserved today and hosted magmatism and sedimentation related to inboard extensional events. The 1.15–0.9 Ga period is host to Sveconorwegian orogenesis that marks the end of this long-lived accretionary orogen and features significant crustal deformation, metamorphism, and magmatism. Collision of an indenter, typically Amazonia, is commonly inferred for the cause of widespread Sveconorwegian orogenesis, but this remains inconclusive. An alternative is that orogenesis merely represents subduction, terrane accretion, crustal thickening, and burial and exhumation of continental crust, along an accretionary margin. During the Mesoproterozoic, southwest Fennoscandia was part of a much larger accretionary orogen that grew on the edge of the Columbia supercontinent and included Laurentia and Amazonia amongst other cratons. The chain of convergent margins along the western Pacific is the best analogue for this setting of Proterozoic crustal growth and tectonism.  相似文献   

Comparison of five different ways to assimilate data for a simplistic weakly nonlinear parameter estimation problem     

Trond Mannseth 《Computational Geosciences》2015,19(4):791-804

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Fluid-assisted zircon and monazite growth within a shear zone: a case study from Finnmark,Arctic Norway   总被引：1，自引：0，他引：1  

Christopher L. Kirkland  Martin J. Whitehouse  Trond Slagstad 《Contributions to Mineralogy and Petrology》2009,158(5):637-657

The U–Pb ages, REE content, and oxygen isotopic composition of zircon rims developed within a major shear zone in the Kalak Nappe Complex (KNC), Arctic Norway have been determined along with the age of monazite crystals. Different generations of granitic veins have been distinguished based on both field criteria and monazite ages of 446 ± 3 and 424 ± 3 Ma. Within each of these veins, inherited zircon cores are mantled by homogeneous low CL-response zircon rims which yield a range of concordant U–Pb dates of ca. 470–360 Ma. Significant numbers of zircon rims coincide with the timing of monazite crystallization. The zircon rims have moderate light REE enrichment compared to cores, distinctive (Sm/La) _n values of less than 12, and La between 0.3 and 10 ppm. This indicates free elemental exchange between newly formed zircon rims and the surrounding matrix. The rims have calculated accumulated alpha-radiation dosages corresponding with a crystalline structure and δ¹⁸O values of 1‰. This implies rim crystallization directly from a zirconium-saturated hydrothermal fluid which was modified by some silicate melt. Growth of the zircon rims was prolonged and locally variable due to preferential fluid flow. A third type of zircon can be recognized, forming both rims and cores, with high alpha-radiation doses, and significant enrichment in La, Pr, and Eu. These are interpreted as low-temperature hydrothermally altered metamict zircons. The high volatile input and partial melting in the shear zone favoured prolonged zircon rim growth due to its ability to easily nucleate on inherited seeds. On the other hand, monazite, susceptible to dissolution and re-growth, crystallized in brief episodes, as has been predicted from theoretical phase diagrams. From a regional perspective, these results elucidate cryptic Ar–Ar cooling ages, providing the first record of a Late Ordovician heating and cooling phase within the KNC prior to the climactic Scandian collision.  相似文献   

Local content in emerging growth poles: Local effects of multinational corporations’ use of contract strategies     

Sveinung Eikeland  Trond Nilsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(1):13-23

The article analyses ‘local content’ in the strategies of multinational corporations (MNCs). Local content is explored as a link between MNCs and growth poles emerging through contract systems that encourage regional firms to connect with global networks entering a region. With a theoretical starting point in literature on local content and growth pole development, the analysis contributes to developing theories of growth poles by adding novel elements such as MNCs’ procurement strategies and their influence on growth poles through local content in contracts. Three aspects of MNCs’ contracts able to secure local content and thus increase contributions from extraction projects to regional development processes are analysed: (1) whether and how MNC projects are divided into subcontract modules, (2) the position and use of framework contracts, and (3) how transportation costs to sites are included in the biddings. It is concluded that further research on MNCs and local content would need to be aware of the following: factors that facilitate or maintain discrimination between bidders included and not included in global networks; reasons why advantages of geographical proximity are underexposed; and how public authorities (states) establish rules that give equality to local enterprises in their competition with firms entering from outside.  相似文献   

Assessment of Erythemal UV Level in Nepal Based on Solar UV Estimates from Total Ozone Mapping Spectrometer     

Binod Kumar BHATTARAI  Berit KJELDSTAD  Trond Morten THORSETH 《大气科学进展》2011,28(4):789-796

Nepal lies on the southern slope of Himalaya in Asia. In a width ranging between 150 and 250 km, the altitude varies greatly from about 100 m at its southern border to a maximum of 8848 min the northern part. Like the variation in altitude, climatic condition varies quite a lot. Long-term monthly mean erythemal UV daily dose values for Nepal are evaluated using Total Ozone Mapping Spectrometer (TOMS) estimation from the time of its overpass between 1996 and 2003. The results are presented as summer and winter maps of mean UV levels in each satellite grid. The mean winter erythemal UV daily dose ranges between 2.1 and 3.6 kJ m-2 whereas summer values are found to lie between 4.6 and 9.7 kJ m-2. The altitude variation increases the UV levels by about 0.2 kJ km-1 in winter months, and 0.9 kJ km-1 in summer. A multiyear monthly average erythemal daily dose in most of the areas shows that the summer value is about three times higher than that in winter. Although year-to-year variation is not pronounced in high- and mid-elevation regions, UV levels seemed to decrease from 1997 to 2002 in the southern part of the country in the low elevation region by about 5.35%. Due to the combined effects of the altitude, low ozone concentration in the troposphere, and thin air, surface UV radiation at higher altitudes is found to be higher than in the surrounding regions.  相似文献