Influence of tectonic structures on the Hope Slide, British Columbia, Canada     

Marc-Andr  Brideau  Doug Stead  Derek Kinakin  Karin Fecova 《Engineering Geology》2005,80(3-4):242-259

The Hope Slide, which occurred on January 9, 1965, involved an estimated 47-Mm³ of meta-volcanics and intrusive rocks. Previous workers reported the presence of tectonic structures (faults and shear zones) along the failure surface at the Hope Slide. These tectonic features were investigated in detail to assess their effects on rock-mass quality and the related implications for slope stability. This paper integrates basic field and laboratory concepts from structural and engineering geology. Subdividing the failure area into structural domains allowed distinct discontinuity sets to be associated with specific tectonic structures. The Geological Strength Index (GSI) was used to estimate the rock-mass damage related to the tectonic structures. Low GSI values were seen to outline tectonic damage zones. Point-load tests were used to characterise the compressive strength of rocks adjacent to the tectonic structures. Strength anisotropy, tentatively attributed to damage caused by a large shear zone, was observed in greenstone samples. Seepage zones along the failure surface were observed preferentially along shallow discontinuities that dipped downslope and in rock masses of good quality (GSI > 40). An alternative morphology of the slope failure is proposed by distinguishing between the extent of the surficial damage due to the rock-slope failure and the zone of failed material (depletion zone). For the first time, a kinematic mechanism for the Hope Slide is proposed, based on a preliminary 3-dimensional block model. A pre-1965 DEM was produced from estimates of material lost and gained as reported by previous workers. The pre-1965 DEM revealed that the tectonic structures recognised during fieldwork bounded the material that failed in the 1965 event.  相似文献   

9: Processes of tectonism, magmatism and mineralization: Lessons from Europe     

Derek Blundell  Nicholas Arndt  Peter R. Cobbold  Christoph Heinrich 《Ore Geology Reviews》2005,27(1-4):333

Metallogenic provinces in Europe range in age from the Archaean to the Neogene. Deposit types include porphyry copper and epithermal Cu–Au, volcanic-hosted massive sulphide (VMS), orogenic gold, Fe-oxide–Cu–Au, anorthosite Fe–Ti-oxide and sediment-hosted base-metal deposits. Most of them formed during short-lived magmatic events in a wide range of tectonic settings; many can be related to specific tectonic processes such as subduction, hinge retreat, accretion of island arcs, continental collision, lithosphere delamination or slab tear. In contrast, most sediment-hosted deposits in Europe evolved in extensional, continental settings over significant periods of time. In Europe, as elsewhere, ore formation is an integral part of the geodynamic evolution of the Earth's crust and mantle. Many tectonic settings create conditions conducive to the generation of water-rich magma, but the generation of ore deposits appears to be restricted to locations and short periods of change in temperature and stress, imposed by transitory plate motions. Crustal influence is evident in the strong structural controls on the location and morphology of many ore deposits in Europe. Crustal-scale fault–fracture systems, many involving strike-slip elements, have provided the fabric for major plumbing systems. Rapid uplift, as in metamorphic core complexes, and hydraulic fracturing can generate or focus magmatic–hydrothermal fluid flow that may be active for time spans significantly less than a million years. Once a hydrologically stable flow is established, ore formation is strongly dependent on the steep temperature and pressure gradients experienced by the fluid, particularly within the upper crust. In Europe, significant fracture porosity deep in the crystalline basement (1%) is not only important for magmatic–hydrothermal systems, but allows brines to circulate down through sedimentary basins and then episodically upward, expelled seismically to produce sediment-hosted base-metal deposits and Kupferschiefer copper deposits. Emerging research, stimulated by GEODE, can improve the predicting power of numerical simulations of ore-forming processes and help discover the presence of orebodies beneath barren overburden.  相似文献   

Monumental space and the uncanny     

Derek Hook 《Geoforum》2005,36(6):688-704

This paper takes up the attempt to theorize the relation between the subjectivity of the political actor and the ideological aura of the monumental site. It does this with reference to the spatial history of Strijdom Square in Pretoria, South Africa, a cultural precinct and monumental space which was the site of a series of brutal racist killings committed by the Square’s unrelated namesake, militant right-winger Barend Strydom. This troubling intersection of subjectivity, space and ideology represents something of an explanatory limit for spatio-discursive approaches, certainly in as much as they are ill-equipped to conceptualize the powerfully affective, bodily and fantasmatic qualities of monumental spaces. In contrast to such approaches I offer a psychoanalytically informed account which grapples with the individualized and imaginative identities of space, with space as itself a form of subjectivity. I do this so as understand the ideological aura of monuments as importantly linked to the ‘intersubjectivity’ of subject and personified space. I then turn to Freud’s notion of the uncanny as a theory able to explain a series of disturbing affects of monuments, such as those of ‘embodied absence’ and ‘disembodied presence’. These and similar affects of ‘ontological dissonance’ (such as unexplained instances of doubling or repetition) may function in an ideological manner, both so as to impose a ‘supernaturalism of power’, and to effect an uncanny form of interpellation.  相似文献   

Review on “Applied Geomorphology: theory and practice”: Allison, R.J., 2002. John Wiley and Sons, London. Hardback, £125, ISBN 0-471-89555-5. 480 pp.+xi     

Derek J. McGlashan   《Geomorphology》2004,57(3-4):441-443

  相似文献   

Comet Hale-Bopp and the Diffuse Interstellar Lines     

Derek McNally 《Astrophysics and Space Science》2000,273(1-4):117-119

As an illustration of the manner in whichserendipitous events can be used to obtain usefulscientific information, the reasons for observing,spectroscopically, the appulse of HD 12895 and CometHale-Bopp are discussed and the conclusions of thestudy are briefly presented.  相似文献   

Spatial process and data models: Toward integration of agent-based models and GIS   总被引：8，自引：1，他引：8  

Daniel G. Brown  Rick Riolo  Derek T. Robinson  Michael North  William Rand 《Journal of Geographical Systems》2005,7(1):25-47

The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, we identify four key relationships affecting how geographic data (fields and objects) and agent-based process models can interact: identity, causal, temporal and topological. We discuss approaches to implementing tight integration, focusing on a middleware approach that links existing GIS and ABM development platforms, and illustrate the need and approaches with example agent-based models.  相似文献   

Spectral Filtering and Classification of Terrestrial Laser Scanner Point Clouds   总被引：1，自引：0，他引：1  

Derek D.  Lichti 《The Photogrammetric Record》2005,20(111):218-240

A method is presented for filtering and classification of terrestrial laser scanner point clouds. The algorithm exploits the four-channel (blue, green, red and near infrared) multispectral imaging capability of some terrestrial scanners using supervised, parametric classification to assign thematic class labels to all scan cloud points. Its principal advantage is that it is a completely data-driven algorithm and is independent of spatial sampling resolution since the processing is performed in four-dimensional spectral feature space. Its application to two data-sets of different spatial extent and spatial and spectral complexity is reported, for which respective overall classification accuracies of 87·0% and 82·0% were achieved. Analysis of the input data with emphasis on the characteristics pertinent to the anticipated outcomes precedes detailed analysis of the classification results and error sources and their causes. Erroneously classified points are attributed to radiometric errors stemming from both detector hardware and physical effects.  相似文献   

A formula describing both magnetic and isotopic blocking temperatures     

Derek York 《Earth and Planetary Science Letters》1978,39(1):89-93

The following new theorem is proved: the equation E/RT_B =ln(1.781 k₀τ), where E = activation energy, R = the molar gas constant and T_B = blocking temperature, applies equally well to both the isotopic and the magnetic systems in rocks from a cooling orogen. The isotopic model involves first-order loss of daughter, while the magnetic model applies to an assemblage of single-domain grains with constant E. Dodson supplied the original proof that the equation applied to isotopic systems. The well-known superficial similarity between the concepts of isotopic and magnetic blocking is thus given quantitative expression.  相似文献   

A two-dimensional photochemical model of the stratosphere with Rayleigh scattering     

Guido Visconti  Gianni Pitari  Derek Cunnold 《Pure and Applied Geophysics》1980,118(2):1033-1051

Computations of concentrations of minor stratospheric gases using a two-dimensional model of the stratosphere are reported. The model includes Rayleigh scattering. This results in an increase in the photodissociation rate computation time by a factor of 1.5. The effect of ground albedo is assessed by comparing our results with a calculation of photolysis rates for a constant albedo with latitude. Comparison of results with a reference model including only molecular absorption are also made. The largest differences (50%) occur in NO and OH. An approximate expression for including the effects of Rayleigh scattering and surface reflectance in multi-dimensional models is suggested.  相似文献   

Aims and implementation in British urban and regional planning     

Derek R. Diamond 《Geoforum》1979,10(3):275-282

Failure to fully understand or recognise crucial but culturally-determined British dimensions has led to confusion and error even among the British geographers in understanding and contributing to, urban and regional planning. This point assumes more rather than less significance in the context of a discussion between British and Soviet geographers. This paper therefore examines in part one, three fundamental features of the British system of urban and regional planning and then proceeds in part two to focus on the aims and their implementation. It concludes with a reference to the nature of the relationship between planning and geography.  相似文献