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31.
Alastair H. F. Robertson Corina Ionescu Volker Hoeck Friedrich Koller Kujtim Onuzi Ioan I. Bucur Dashamir Ghega 《International Journal of Earth Sciences》2012,101(6):1535-1558
Sedimentology can shed light on the emplacement of oceanic lithosphere (i.e. ophiolites) onto continental crust and post-emplacement settings. An example chosen here is the well-exposed Jurassic Mirdita ophiolite in southern Albania. Successions studied in five different ophiolitic massifs (Voskopoja, Luniku, Shpati, Rehove and Morava) document variable depositional processes and palaeoenvironments in the light of evidence from comparable settings elsewhere (e.g. N Albania; N Greece). Ophiolitic extrusive rocks (pillow basalts and lava breccias) locally retain an intact cover of oceanic radiolarian chert (in the Shpati massif). Elsewhere, ophiolite-derived clastics typically overlie basaltic extrusives or ultramafic rocks directly. The oldest dated sediments are calpionellid- and ammonite-bearing pelagic carbonates of latest (?) Jurassic-Berrasian age. Similar calpionellid limestones elsewhere (N Albania; N Greece) post-date the regional ophiolite emplacement. At one locality in S Albania (Voskopoja), calpionellid limestones are gradationally underlain by thick ophiolite-derived breccias (containing both ultramafic and mafic clasts) that were derived by mass wasting of subaqueous fault scarps during or soon after the latest stages of ophiolite emplacement. An intercalation of serpentinite-rich debris flows at this locality is indicative of mobilisation of hydrated oceanic ultramafic rocks. Some of the ophiolite-derived conglomerates (e.g. Shpati massif) include well-rounded serpentinite and basalt clasts suggestive of a high-energy, shallow-water origin. The Berriasian pelagic limestones (at Voskopoja) experienced reworking and slumping probably related to shallowing and a switch to neritic deposition. Mixed ophiolite-derived clastic and neritic carbonate sediments accumulated later, during the Early Cretaceous (mainly Barremian-Aptian) in variable deltaic, lagoonal and shallow-marine settings. These sediments were influenced by local tectonics or eustatic sea-level change. Terrigenous sediment gradually encroached from neighbouring landmasses as the ophiolite was faulted or eroded. An Aptian transgression was followed by regression, creating a local unconformity (e.g. at Boboshtica). A Turonian marine transgression initiated widespread Upper Cretaceous shelf carbonate deposition. In the regional context, the southern Albania ophiolites appear to have been rapidly emplaced onto a continental margin in a subaqueous setting during the Late Jurassic (Late Oxfordian-Late Tithonian). This was followed by gradual emergence, probably in response to thinning of the ophiolite by erosion and/or exhumation. The sedimentary cover of the south Albanian ophiolites is consistent with rapid, relatively short-distance emplacement of a regional-scale ophiolite over a local Pelagonian-Korabi microcontinent. 相似文献
32.
Flood quantiles are routinely used in hydrologic engineering to design hydraulic structures, optimize erosion control structure
and map the extent of floodplains. As an increasing number of papers are pointing out cycles and trends in hydrologic time
series, the use of stationary flood distributions leads to the overestimation or underestimation of the hydrologic risk at
a given time. Several authors tried to address this problem by using probability distributions with time-varying parameters.
The parameters of these distributions were assumed to follow a linear or quadratic trend in time, which may be valid for the
short term but may lead to unrealistic long-term projections. On the other hand, deterministic rainfall-runoff models are
able to successfully reproduce trends and cycles in stream flow data but can perform poorly in reproducing daily flows and
flood peaks. Rainfall-runoff models typically have a better performance when simulation results are aggregated at a larger
time scale (e.g. at a monthly time scale vs. at a daily time scale). The strengths of these two approaches are combined in
this paper where the annual maximum of the time-averaged outputs of a hydrologic model are used to modulate the parameters
of a non-stationary GEV model of the daily maximum flow. The method was applied to the Kemptville Creek located in Ontario,
Canada, using the SWAT (Soil and Water Assessment Tool) model as rainfall-runoff model. The parameters of the non-stationary
GEV model are then estimated using Monte Carlo Markov Chain, and the optimal span of the time windows over which the SWAT
outputs were averaged was selected using Bayes factors. Results show that using the non-stationary GEV distribution with a
location parameter linked to the maximum 9-day average flow provides a much better estimation of flood quantiles than applying
a stationary frequency analysis to the simulated peak flows. 相似文献
33.
34.
Coastal and bank erosion along the St. Lawrence River Waterway in Quebec, Canada, represents a hazard to local communities
living along the river banks, as well as to the local fauna habitat. The purpose of this study is to assess the potential
impact of the waves generated by long containerships on riverbank erosion and recession at critical sites along the St. Lawrence
River Waterway, which have already experienced significant damage. A field study was carried out to investigate the ship-generated
hydrodynamics and the various driving mechanisms of the erosion process induced by ship waves. The field measurements provided
an assessment of the influence of the length of large vessels by comparing the characteristics of the hydrodynamics fields
induced by the passage of two containerships of different lengths. The potential for bank erosion and recession is assessed
in terms of the wake erosive energy incident to the shoreline. The field data are compared against analytical results predicted
by an empirical model, as well as against a ship-generated hydrodynamics model. Several numerical simulations for quantifying
the ship’s drawdown and its effects are also presented. 相似文献
35.
Viorel Badescu Christian A. Gueymard Sorin Cheval Cristian Oprea Madalina Baciu Alexandru Dumitrescu Flavius Iacobescu Ioan Milos Costel Rada 《Theoretical and Applied Climatology》2013,111(3-4):379-399
Fifty-four broadband models for computation of solar diffuse irradiation on horizontal surface were tested in Romania (South-Eastern Europe). The input data consist of surface meteorological data, column integrated data, and data derived from satellite measurements. The testing procedure is performed in 21 stages intended to provide information about the sensitivity of the models to various sets of input data. There is no model to be ranked “the best” for all sets of input data. However, some of the models performed better than others, in the sense that they were ranked among the best for most of the testing stages. The best models for solar diffuse radiation computation are, on equal footing, ASHRAE 2005 model (ASHRAE 2005) and King model (King and Buckius, Solar Energy 22:297–301, 1979). The second best model is MAC model (Davies, Bound Layer Meteor 9:33–52, 1975). Details about the performance of each model in the 21 testing stages are found in the Electronic Supplementary Material. 相似文献
36.
We present here the results of pollen analysis of two sequences of about 8.06 m and 11.90 m length, originating from two adjacent peat bogs in the southern part of Transylvania province, Romania (155 and 122 pollen spectra). The vegetation record, which is supported by 17 14C dates, begins in the Late Glacial interstadial when forest recolonisation began with the development of Pinus, without a pioneer Betula phase. Picea began to expand from regional refuges. After a well‐defined Younger Dryas, the Holocene opens with the expansion of Betula, Ulmus and Picea, followed, at about 10 400 cal. yr BP, by Fraxinus, Quercus and Tilia. The Corylus optimum is correlated with the Atlantic chronozone (after 8600 cal. yr BP). The local establishment of Carpinus occurred at about 6500 cal. yr BP, with a maximum at about 5700 cal. yr BP. Fagus pollen is regularly recorded after 8200 cal. yr BP. This taxon became dominant at about 3700 cal. yr BP. The first indications of human activities appear at around 7200 cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
37.
The paper is intended to summarize the most important instrumental data of direct relevance for engineering activities, obtained in connection with the strong Vrancea earthquakes of 4 March 1977, 30 August 1986, 30 May 1990, and 31 May 1990, and to point out some significant consequences and conclusions derived on this basis. Two main objectives of this analysis may be emphasized: (a) in-depth analysis of the radiation pattern; and (b) analysis of the spectral contents of ground motion in connection with the features of local conditions, and with the intention of assessing the relative importance of two main factors: source mechanism and long-distance wave propagation, versus features of local geological conditions. Some specific methodological developments used in this context may be mentioned: (a) use of a new approach to the quantification of ground motion intensity on the basis of instrumental (accelerographic) information; (b) analysis of radiation pattern in spectral and directivity terms; (c) parametric analysis of site-specific transfer functions for the local sequences of geological layers; and (d) a critical view on the outcome of post-earthquake survey techniques, keeping in view the implications of the spectral features of ground motion. The main results obtained are related to: (a) ground motion radiation features that have to be taken into account in connection with the data on the source mechanisms of the successive events dealt with; (b) expected spectral features of future strong ground motion at different sites; (c) methodological developments proposed for the assessment of local transfer functions; and (d) implications for microzonation activities. 相似文献
38.
Ioan Ianos Dr. 《GeoJournal》1996,38(2):175-179
Change in the village reflects the evolution of society and the conditions in the surrounding territory, including the neighbouring rural settlements and towns with which there is interaction. These considerations will determine the size and functions of a village, moving through centuries of change, often marked by violent events (invasions and wars; epidemics and natural disasters). So the search for equilibrium has often been frustrated by changing events. The paper concentrates on the upheavals associated with communism at the end of the Second World War, leading to the degradation of rural society, and the adjustments now being made in the light of the revolution of 1989. After the upheavals of the first transition years there are signs that prosperity is beginning to return to the villages as higher incomes from agriculture benefit the rural economy as a whole. 相似文献
39.
40.
Classification of Tsunami and Evacuation Areas 总被引:3,自引:2,他引:1
Tomoya Shibayama Miguel Esteban Ioan Nistor Hiroshi Takagi Nguyen Danh Thao Ryo Matsumaru Takahito Mikami Rafael Aranguiz Ravindra Jayaratne Koichiro Ohira 《Natural Hazards》2013,67(2):365-386
On March 11, 2011, a large earthquake that occurred offshore the north-east coast of Japan generated a large tsunami which devastated extensive areas of the Tohoku coastline. Despite Japan being considered a country well prepared for these types of disasters, large casualties were recorded, with numerous discussions amongst the Japanese coastal engineering community ensuing. As a result, two different levels of tsunamis have been proposed and now recognized in Japan, depending on the frequency of such extreme events. The idea that hard measures can protect the lives of inhabitants of coastal areas has been abandoned, and these measures are only considered to be effective in protecting properties against the more frequent but lower magnitude events. Soft measures should always be used to protect against the loss of lives, and to this respect, the authors of the paper propose the introduction of a Classification of Evacuation Areas, to show which of these should be prioritized by residents as they seek to evacuate. 相似文献