Geohazard identification: the gap between the possible and reality in geophysical surveys for the engineering industry     

Julie M. Dyer 《Marine Geophysical Researches》2011,32(1-2):37-47

Offshore Contractors engaged in the business of installing pipelines and subsea structures routinely rely on third party survey data to identify and assess the risk of surface and buried geohazards. In many cases, route or site survey data are supplied to a marine Contractor with the latter having little or no input to the manner in which the geophysical and geotechnical data are acquired, processed and reported. Often, the completed survey reports indicate that neither data acquisition nor the subsequent data processing were carried out with the ultimate goal of the survey or the end user in mind. This lack of focus at the survey stage can contribute to incorrect or over-optimistic assessments of geohazard risk, with serious impact on offshore installation operations as a consequence. Two case studies from the North Sea are discussed where inappropriate data processing and reporting of geophysical data had a negative impact on offshore installation operations; these are used as a basis for a more general discussion of the underlying reasons for the production of engineering survey reports which are ??not-fit-for-purpose??.  相似文献   

Estuarine and Wetland Processes with emphasis on modelling: Edited by P. Hamilton and K. B. MacDonaldPlenum Press,New York, 1980, xi+653 pp., $69.50, £43.79     

K.R. Dyer 《Estuarine, Coastal and Shelf Science》1982,15(1):116-118

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The rail-cutter: a simple,cheap and compact system for opening sediment cores in the lab and field     

Graeme N. D. Rogers  Karen I. Bonner  Jamie R. Wood  Janet M. Wilmshurst 《Journal of Paleolimnology》2015,53(4):433-436

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Life-bearing primordial planets in the solar vicinity     

N. Chandra Wickramasinghe  Jamie Wallis  Daryl H. Wallis  Rudolph E. Schild  Carl H. Gibson 《Astrophysics and Space Science》2012,341(2):295-299

The space density of life-bearing primordial planets in the solar vicinity may amount to ～8.1×10⁴?pc^?3 giving total of ～10¹⁴ throughout the entire galactic disk. Initially dominated by H₂ these planets are stripped of their hydrogen mantles when the ambient radiation temperature exceeds 3?K as they fall from the galactic halo to the mid-plane of the galaxy. The zodiacal cloud in our solar system encounters a primordial planet once every 26 My (on our estimate) thus intercepting an average mass of 10³ tonnes of interplanetary dust on each occasion. If the dust included microbial material that originated on Earth and was scattered via impacts or cometary sublimation into the zodiacal cloud, this process offers a way by which evolved genes from Earth life could become dispersed through the galaxy.  相似文献   

Australian Climate,Energy and Water Policies: conflicts and synergies     

Jamie Pittock  Karen Hussey  Samuel McGlennon 《The Australian geographer》2013,44(1):3-22

Responding to the threat of climate change, conserving freshwater ecosystems and securing adequate energy and water supplies are among the greatest challenges facing modern societies. Yet recognition of the interdependencies between climate, energy and water policy—with resulting synergies and trade-offs—remains limited, leaving societies and governments alike vulnerable to the dangers of conflicted or unintended policy outcomes from sectoral decisions. In this paper, we analyse current Australian climate, energy and water policies to identify the risks of perverse outcomes between the three policy sectors. In doing so we categorise the conflicts and synergies between particular energy generation, carbon sequestration and water supply policies to improve understandings of the challenges facing decision makers in Australia and internationally. Four types of interventions are identified that would enable integration and optimisation of policies, namely: better cross-sectoral knowledge to inform decisions; the identification of technologies with co-benefits; markets with broader cross-sectoral participation (including linking water and carbon markets); and better-integrated governance institutions.  相似文献   

Fieldwork Unbound: Spaces of Association in Postconflict Vietnam     

Jamie Gillen 《The Professional geographer》2013,65(4):599-609

This article traces the ways in which the field emerges and becomes emplaced among three groups of people by presenting an inclusive reading of fieldwork in postconflict Vietnam. It employs a heuristic device called spaces of association to illustrate the different yet interrelated socio-spatial fields that surface when conducting fieldwork in an environment known for violence. In shedding light on the field's ability to extend beyond the territorially defined “field site,” this article speaks to debates surrounding the socio-spatial production of multiple and overlapping fields, describes the audiences engaged with and implicated in research, and contributes to understandings of ethical research engagement with postconflict field sites.  相似文献   

Fumarolic pipes in the Tshirege Member of the Bandelier Tuff on the Pajarito Plateau, Jemez Mountains, New Mexico     

Florie A. Caporuscio  Jamie N. Gardner  Emily S. Schultz-Fellenz  Richard E. Kelley 《Bulletin of Volcanology》2012,74(5):1023-1037

The objective of this study is to demonstrate the relationships among devitrification, vapor phase alteration, localization of gas emanations into fumarolic pipes, and initial deformation of the ash flow sheet during cooling and lithification. Utilizing a unique and temporary exposure of the Tshirege Member of the Bandelier Tuff near Los Alamos, New Mexico, we identify several zones of distinctly preserved fossil fumarolic activity. The fumarolic zones vary in width from a few centimeters to more than a meter. Almost ubiquitously, these zones demonstrate fines-depletion, induration of the margins, upward-flaring geometries, and intense fracturing of overlying geologic units. The fumaroles were preferentially located on post welding, early formed cooling joints that vented to the surface after the vapor phase alteration stage. The pipes were regularly spaced at distances of approximately 4.5?m (N–S) to 7?m (E–W). In turn the pipes were covered by a surge deposit and overlying tuff which rapidly lithified. The overlying tuff was then brecciated during continued fumarolic pipe emissions. Geochemical evaluations confirm the presence of high-temperature mineral (scapolite) indicative of transport of hot volcanic gases through these zones. The pipe centers and walls are depleted in SiO₂, and enriched in Al₂O₃ and FeO. The overlying tuff breccia zones are enriched in Al₂O₃, FeO and MgO, and depleted in SiO₂, NaO, and K₂O. From comparison to other ignimbrite cooling histories, the fissures, fumaroles, and structures observed all likely formed in the first few decades after the deposition of the upper Tshirege subunits. This may have significant implications as to timing of initial cooling fractures and subsequent consolidation of gas emission pathways.  相似文献   

Fractional order intensity measures for probabilistic seismic demand modeling applied to highway bridges     

Abdollah Shafieezadeh  Karthik Ramanathan  Jamie E. Padgett  Reginald DesRoches 《地震工程与结构动力学》2012,41(3):391-409

Probabilistic seismic analysis of structures involves the construction of seismic demand models, often stated as probabilistic models of structural response conditioned on a seismic intensity measure. The uncertainty introduced by the model is often a result of the chosen intensity measure. This paper introduces the concept of using fractional order intensity measures (IMs) in probabilistic seismic demand analysis and uses a single frame integral concrete box‐girder bridge class and a seismically designed multispan continuous steel girder bridge class as case studies. The fractional order IMs considered include peak ground response and spectral accelerations at 0.2 and 1.0 s considering a single degree of freedom system with fractional damping, , as well as a linear single degree of freedom system with fractional response, . The study reveals the advantage of fractional order IMs relative to conventional IMs such as peak ground acceleration, peak ground velocity, or spectral acceleration at 0.2 and 1.0 s. Metrics such as efficiency, sufficiency, practicality, and proficiency are measured to assess the optimal nature of fractional order IMs. The results indicate that the proposed fractional order IMs produce significant improvements in efficiency and proficiency, whereas maintaining practicality and sufficiency, and thus providing superior demand models that can be used in probabilistic seismic demand analysis. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

High-frequency rock temperature data from hyper-arid desert environments in the Atacama and the Antarctic Dry Valleys and implications for rock weathering   总被引：1，自引：0，他引：1  

Christopher P. McKay  Jamie L. Molaro  Margarita M. Marinova 《Geomorphology》2009,110(3-4):182-187

In desert environments with low water and salt contents, rapid thermal variations may be an important source of rock weathering. We have obtained temperature measurements of the surface of rocks in hyper-arid hot and cold desert environments at a rate of 1/s over several days. The values of temperature change over 1-second intervals were similar in hot and cold deserts despite a 30 °C difference in absolute rock surface temperature. The average percentage of the time dT/dt > 2 °C/min was ~ 8 ± 3%, > 4 °C/min was 1 ± 0.9%, and > 8 °C/min was 0.02 ± 0.03%. The maximum change over a 1-second interval was ~ 10 °C/min. When sampled to simulate data taken over intervals longer than 1 s, we found a reduction in time spent above the 2 °C/min temperature gradient threshold. For 1-minute samples, the time spent above any given threshold was about two orders of magnitude lower than the corresponding value for 1-second sampling. We suggest that a rough measure of efficacy of weathering as a function of frequency is the product of the percentage of time spent above a given threshold value multiplied by the damping depth for the corresponding frequency. This product has a broad maximum for periods between 3 and 10 s.  相似文献   

Bathymetric control of surf zone retention on a rip-channelled beach     

Bruno Castelle  Ad Reniers  Jamie MacMahan 《Ocean Dynamics》2014,64(8):1221-1231

Simulations from a numerical model address the impact of nearshore morphology on surf zone retention on, open coast, rip-channelled beaches exposed to shore-normal waves. In the model, rip channels are regularly spaced alongshore with a given spacing λ. For a given reference case bathymetry (λ= 200 m), rip current circulations retain floating material at a hourly rate R of about 80 % which is in line with most existing field and laboratory studies in similar settings. The influence of a surf zone rip-channel morphology on surf zone retention is evaluated by a number of morphologic parameters. Results show that rip spacing is important. The ratio of the surf zone width X _s to rip spacing λ controls surf zone retention with R rapidly increasing with increasing X _s /λ up to a threshold of about 1 above which R levels off to become asymptotic to 100 %. The impact of the presence of a rip head bar is profound but nonlinear. The onset of wave breaking across the rip head bar drives a weak seaward located circulation providing major pathways for surface water exiting the surf zone compartment. Additional simulations suggest that alongshore variations in the offshore bathymetry are important. Patterns in the wave field enforced by wave refraction and potentially wave breaking across offshore bathymetric anomalies can provide a conduit for transporting floating material out of the surf zone and into the inner shelf region. This has major implications for surf zone flushing by inner-bar rips on multiple-barred beaches and on beaches facing bathymetric anomalies on the inner shelf.  相似文献