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41.
Development of large‐scale seismites in Upper Cretaceous fluvial sandstones in a fault‐proximal setting
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Michael C. Wizevich Edward L. Simpson Hannah L. Hilbert‐Wolf Sarah E. Tindall 《Sedimentology》2016,63(6):1719-1738
Large‐scale soft‐sediment deformation structures occur within fluvial sandstone bodies of the Upper Cretaceous Wahweap Formation in the Kaiparowits basin, southern Utah, USA. These structures represent an exceptional example of metre‐scale fault‐proximal, seismogenic load structures in nearly homogenous sandstones. The load structures consist of two types: large‐scale load casts and wedge‐shaped load structures. Large‐scale load casts penetrate up to 4·5 m into the underlying sandstone bed. Wedge‐shaped load structures include metre‐scale, parallel, sub‐vertical features and decimetre‐scale features along the periphery of the large‐scale load casts or other wedge‐shaped load structures. Wedge‐shaped load structures contain well‐developed, medial cataclastic shear deformation bands. All load structures contain pervasive well‐defined millimetre‐thick to centimetre‐thick internal laminae, oriented parallel to the outside form of the load structures and asymptotic to deformation bands. Both types of load structures formed because of an inverted density profile, earthquake‐triggered liquefaction and growth of irregularities (a Rayleigh–Taylor instability) on the sandstone–sandstone erosional contact. The internal laminae and deformation bands formed during deformation and clearly demonstrate polyphase deformation, recording a transition from liquefied to hydroplastic to brittle modes of deformation. Decimetre‐scale wedge‐shaped load structures on the edge of the large‐scale load casts probably formed towards the end of a seismic event after the sediment dewatered and increased the frictional contact of grains enough to impart strength to the sands. Metre‐scale wedge‐shaped load structures were created as the tips of downward foundering sediments were driven into fractures, which widened incrementally with seismic pulsation. With each widening of the fracture, gravity and a suction effect would draw additional sediment into the fracture. Superimposed laminae indicate a secondary syndeformational origin for internal laminae, probably by flow‐generated shearing and vibrofluidization mechanisms. Large‐scale and wedge‐shaped load structures, polyphase deformation and secondary laminae may characterize soft‐sediment deformation in certain fault‐proximal settings. 相似文献
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Introductory courses in Geographic Information Science (GIS) expose students to the concepts and practices necessary for future academic and professional use of GIS tools. Traditional GIS courses balance lectures in the theories of GIS with pre‐built and pre‐packaged lab activities to learn the practices of GIS. This article presents a case study of an experimental introductory course in which students conducted novel, independent project‐based group research under the supervision of graduate or advanced undergraduate students enrolled in the course, culminating in a class presentation and publication quality paper. Surveys and interviews indicated that students reacted more positively to project‐based group research than to traditional activities. Students felt the projects better prepared them for ‘real world’ applications of GIS, and recommend project‐based group research in other GIS coursework. Additionally, our findings indicate that students appreciate interactions with peers of varying skill levels and experiences, as these broaden their capabilities to work with other GIS users. 相似文献
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Crime is a complex phenomenon, emerging from the interactions of offenders, victims, and their environment, and in particular from the presence or absence of capable guardians. Researchers have historically struggled to understand how police officers create guardianship. This presents a challenge because, in order to understand how to advise the police, researchers must have an understanding of how the current system works. The work presents an agent‐based model that simulates the movement of police vehicles, using a record of real calls for service and real levels of police staffing in spatially explicit environments to emulate the demands on the police force. The GPS traces of the simulated officers are compared with real officer movement GPS data in order to assess the quality of the generated movement patterns. The model represents an improvement on existing standards of police simulation, and points the way toward more nuanced understandings of how police officers influence the criminological environment. 相似文献
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Lise Byskov Herslund Fatemeh Jalayer Nathalie Jean-Baptiste Gertrud Jørgensen Sigrun Kabisch Wilbard Kombe Sarah Lindley Patrik Karlsson Nyed Stephan Pauleit Andreas Printz Trond Vedeld 《Natural Hazards》2016,82(2):149-172
In this paper, we develop and apply a multi-dimensional vulnerability assessment framework for understanding the impacts of climate change-induced hazards in Sub-Saharan African cities. The research was carried out within the European/African FP7 project CLimate change and Urban Vulnerability in Africa, which investigated climate change-induced risks, assessed vulnerability and proposed policy initiatives in five African cities. Dar es Salaam (Tanzania) was used as a main case with a particular focus on urban flooding. The multi-dimensional assessment covered the physical, institutional, attitudinal and asset factors influencing urban vulnerability. Multiple methods were applied to cover the full range of vulnerabilities and to identify potential response strategies, including: model-based forecasts, spatial analyses, document studies, interviews and stakeholder workshops. We demonstrate the potential of the approach to assessing several dimensions of vulnerability and illustrate the complexity of urban vulnerability at different scales: households (e.g., lacking assets); communities (e.g., situated in low-lying areas, lacking urban services and green areas); and entire cities (e.g., facing encroachment on green and flood-prone land). Scenario modeling suggests that vulnerability will continue to increase strongly due to the expected loss of agricultural land at the urban fringes and loss of green space within the city. However, weak institutional commitment and capacity limit the potential for strategic coordination and action. To better adapt to urban flooding and thereby reduce vulnerability and build resilience, we suggest working across dimensions and scales, integrating climate change issues in city-level plans and strategies and enabling local actions to initiate a ‘learning-by-doing’ process of adaptation. 相似文献
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Słodczyk Elżbieta Pietranik Anna Glynn Sarah Wiedenbeck Michael Breitkreuz Christoph Dhuime Bruno 《International Journal of Earth Sciences》2018,107(6):2065-2081
International Journal of Earth Sciences - The Polish Lowlands, located southwest of the Teisseyre–Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly... 相似文献
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M. S. Sreekala Sarah John Sareen Sivalingam Rajathi 《Journal of the Geological Society of India》2018,91(5):621-626
Geo-environmental studies in parts of Ernakulam district (Kerala, India) were carried out. The study area comprises of sedimentary (Limestone, sandstone, Clay and Lignite) and crystalline (Charnockite and gneisses) rocks. The sedimentary terrain is characterized by confined and unconfined aquifers. In hard crystalline formations groundwater occurs under phreatic conditions in the shallow weathered portions and under semi confined to confined conditions in the deep-seated fractures. The study area is demarcated into five areas based on soil types. Climate is hot humid to hot summer with heavily raining monsoon. Two major rivers Periyar and Muvattupuzha drain through the area. Agricultural and industrial activities are prevalent in Ernakulam district. The major cause of pollution in the study area is due to the presence of coliforms. Detailed investigations carried out to identify the coliforms indicated spatial and seasonal changes in the distribution pattern. Monsoon and post monsoon showed significantly high total coliforms compared to pre-monsoon. Thermo-tolerant coliforms is high during monsoon season. This seasonal change could be due to the effect of rainfall, overland flow, nutrient load and temperature change. Wide variations in the coliform counts are observed in wells situated near rivers, canals, paddy fields and in water bodies lying close to pilgrimage center, fertilizer industry, and public places. It is noticed that the chemical characteristics of the groundwater influence the coliform survival. pH, nitrite, bicarbonate, hardness, and alkalinity play a significant role in controlling coliform count. At the outset, the study highlighted the impact of anthropogenic activities on ground water in a coastal district of Kerala state. 相似文献
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