共查询到20条相似文献，搜索用时 22 毫秒
1.
Renato Macciotta C. Derek Martin Norbert R. Morgenstern David M. Cruden 《Landslides》2016,13(1):115-127
Railway alignments through the Canadian Cordillera are constantly exposed to slope instabilities. Proactive mitigation strategies have been in place for a few decades now, and instability record keeping has been recognized as an important aspect of them. Such a proactive strategy has enhanced the industry’s capacity to manage slope risks, and some sections have been recognized as critical due to the frequency of instabilities. At these locations, quantification of the risks becomes necessary. Risk analysis requires knowledge of some variables for which statistical data are scarce or not available, and elicitation of subjective probabilities is needed. A limitation of such approaches lies in the uncertainty associated to those elicited probabilities. In this paper, a quantitative risk analysis is presented for a section of railway across the Canadian Cordillera. The analysis focused on the risk to life of the freight train crews working along this section. Upper and lower bounds were elicited to cope with the uncertainties associated with this approach. A Monte Carlo simulation technique was then applied to obtain the probability distribution of the estimated risks. The risk probability distribution suggests that the risk to life of the crews is below previously published evaluation criteria and within acceptable levels. The risk assessment approach proposed focuses on providing a measure of the uncertainty associated with the estimated risk and is capable of handling distributions that cover more than two orders of magnitude. 相似文献
2.
Harm E. Rondell 《Journal of African Earth Sciences》1999,28(4):867-871
A large number of changes affect the professional environment of the earth scientist. These changes are quite rapid when seen within the human life span. They are brought about by improved communication networks, continuously developing instrumentation, the increasingly interdisciplinary nature of the sciences and the changing demands of society. If taken seriously, then these changes must lead to a revision of the earth science curriculum, in which the fundamentals of the earth sciences should be studied in an integrated manner and in which skills, rather than just knowledge, are valued. Practical suggestions on how to revise the curriculum are made. 相似文献
3.
T. F. Stocker 《International Journal of Earth Sciences》1999,88(2):365-374
A review of climatic variability is given with a focus on abrupt changes during the last glacial. Evidence from palaeoclimatic
archives suggests that these were most likley due to reorganisations of the atmosphere–ocean system. The mechanisms responsible
for these changes are presented. Their implication for future climate changes is discussed in light of recent climate model
simulations.
Received: 24 June 1998 / Accepted: 27 November 1998 相似文献
4.
《Comptes Rendus Geoscience》2008,340(2-3):83-93
The underlying cause of Indosinian thermotectonism remains unclear, in part because the term has also been adopted to explain Triassic orogenesis across southern China. This paper puts forward the case that use of the term Indosinian should be confined to Vietnam where deformation is linked to continental accretion as opposed to southern China where Triassic igneous activity, metamorphism and deformation are linked to the development of an active plate margin through north-directed subduction of the Pacific oceanic plate. A review of the regional palaeogeography, as well as palaeontological and thermochronological data, highlights the lack of evidence to support the Indosinian as a major mountain building event. There is no definitive evidence for Triassic collision between the Indochina and South China blocks. Preference is given to a plate tectonic model that explains the Indosinian as a reactivation event driven by accretion of Sibumasu block to Indochina. 相似文献
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Summary The crystal structure of cesstibtantite has been solved from diffractometer data collected on samples from Leshaia, Russia and the Tanco pegmatite, Manitoba. Cesstibtantite from the Leshaia pegmatite (type locality) hasa 10.515(2) Å, space groupFd3m, composition Cs0.31(Sb0.57Na0.31Pb0.02Bi0.01)O.91(Ta1.88Nb0.12)2(O5.69[OH, F]0.31)6(OH, F)0.69, Z 8; its structure was refined toR 3.8,wR 4.3% using 96 observed (F > 3[F]) reflections (MoK). Cesstibtantite from the Tanco pegmatite hasa 10.496(1) Å, space groupFd3m, composition (Cs0.22K0.01)0.23(Na0.45Sb0.39Pb0.14· Ca0.06Bi0.02)1.06(Ta1.95Nb0.05)2(O5.78[OH,F]0.22)6(OH,F)0.55,Z 8; its structure was refined toR 3.9w R 3.7% using 104 observed reflections. Cesstibtantite differs from the normal pyrochlores in that it contains significant amounts of very large cations such as Cs. As these cations are too large (VIII[r] > 1.60 Å) for the conventional [8]-coordinated A site, they occupy the [18]-coordinated site, which normally contains monovalent anions. Natural cesstibtantite samples are non-ideal in that both Cs and monovalent anions occur at the site; thus cesstibtantite is intermediate to thenormal pyrochlores (with only monovalent anions at the site) and theinverse pyrochlores (with only large cations at the site).
Cesstibtantit—eine geologische Einfiihrung in die inversen Pyrochlore
Zusammenfassung Die Kristallstruktur von Cesstibtantit wurde auf der Basis von Diffraktometerdaten von Proben von Leshaia, Russland and dem Tanco Pegmatit, Manitoba, gelöst. Cesstibtantit aus dem Leshaia Pegmatit (Typlokalität) hat a 10.515(2) Å, RaumgruppeFd3m, die Zusammensetzung CS0.31(Sb0.57Na0.31Pb0.02Bi0.01)0.91(Ta1.88Nb0.12)2· (O5.69OH, F0.31)6(OH, F)0.69 Z 8; die Struktur wurde aufR 3.8,wR 4.3% verfeinert unter Benützung von 96 beobachteten Reflexen. Cesstibtantit vom Tanco Pegmatit hat a 10.496(1) Å, RaumgruppeFd3m, die Zusammensetzung (Cs0.22K0.01)0.23(Na0.45· Sb0.39Pb0.14Ca0.06Bi0.02)1.06(Ta1.95Nb0.05)2(O5.78OH,F0.22)6(OH,F)0.55,Z 8; seine Struktur wurde aufR 3.9wR 3.7% auf der Basis von 104 beobachteten Rettexen verfeinert. Cesstibtantit unterscheidet sich von normalen Pyrochloren insofern, als er signifikante Mengen von sehr großen Kationen, wie z.B. Cs enthält. Da these Kationen zu groß sind (VIII r 1.60 Å) für eine konventionelle [8]-koordinierteA Stelle, nehmen she die [18]-koordinierten Positionen ein, welche normalerweise monovalente Anionen enthalten. Natürliche Cesstibtantitproben sind nicht ideal insofern als sowohl Cs als auch monovalente Anionen in der Position vorkommen. Somit ist Cesstibtantit intermediär zu den normalen Pyrochloren (mit nur monovalenten Anionen auf der Position) and den inversen Pyrochloren (mit ausschließlichen großen Kationen an der Position).相似文献
7.
Over the last 30 years, a growing body of research has shown that first-order control of the elevation of Earth's surface is exercised by thermal anomalies in the upper asthenosphere. One line of research is to test models and observations of mantle behaviour against the sedimentary record. A second line of research is to use the sedimentary record to further understanding of mantle behaviour. Here this second line of research is adopted: a particular hypothesis of mantle behaviour is tested against the Quaternary sedimentary record of the Thames valley, England. Schoonman et al. (2017) have proposed that a warm finger of mantle material extending from the Icelandic plume underlies southern England at the present day. That warm finger would represent the distal end of the influence of the Icelandic plume in this area, and would have advanced broadly from west to east, causing a progressive tilt of the surface of the Thames valley towards the east. The warm-finger hypothesis is supported by the evidence reviewed here. That evidence consists of two main sets of observations, both sets established beyond reasonable doubt by many researchers over many years. First, there is the progressive increase in elevation westward from the present-day coast of the North Sea of the 2.5–2 Ma shallow-marine Red and Norwich Crags. Second, there is the subsequent Quaternary record of progressive eastward tilting of the Thames valley shown in the river terraces. 相似文献
8.
Gonçalves Leonardo Alkmim Fernando F. Pedrosa-Soares Antônio Gonçalves Cristiane C. Vieira Valter 《International Journal of Earth Sciences》2018,107(1):337-358
International Journal of Earth Sciences - The Araçuaí-West Congo orogen (AWCO) is one of the various components of the Brasiliano/Pan-African orogenic network generated during the... 相似文献
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To understand the evolution of a disaster, we propose a Framework for Assessing Crisis in a System Environment (FACSE). FACSE is set in a multi-system environment, containing the human system as well as the various natural and technological systems that interact with people. We take a lifecycle perspective, via which we quantify rhythms of life exhibited in multiple systems, across different scales, at different times. The lifecycle perspective also implies a relative approach in that rhythms of life during time t can be compared against those during t-1. We illustrate how rhythms of life in the human system can be measured at different scales. We propose a new concept??the degree of disaster, which is a composite score that encompasses the various measurements of rhythms of life from multiple systems, across different scales. We conclude the paper by discussing the potential offered by FACSE in disaster research as well as the limitations. 相似文献
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Song Danqing Liu Xiaoli Li Bin Zhang Jianmin Bastos Juan Jose Volcan 《Acta Geotechnica》2021,16(4):1281-1302
Acta Geotechnica - To investigate the influence of a rapid water drawdown (RWD) on the seismic response characteristics of reservoir rock slopes, numerical dynamic analyses and shaking table tests... 相似文献
12.
Yang Wendong Xie Quanmin Xia Yuanyou Li Xinping 《中国地质大学学报(英文版)》2005,16(4):354-358
Because the main failure type of a dangerous rock mass is collapse, the treatment of such a mass should focus on controlling collapse failure. When treating dangerous rock masses, disturbing the mass （e. g. by blasting） needs to be avoided, as this new damage could cause collapse. So the self-bearing capacity of the mountain mass must be used to treat the dangerous rock mass. This article is based on a practical example of the control of a dangerous rock mass at Banyan Mountain, Huangshi, Hubei Province. On the basis of an analysis of damage mechanism and the stability of the dangerous rock mass, a flexible network reinforcement method was designed to prevent the collapse of the rock mass. The deformations of section Ⅱ w of the dangerous rock mass before and after the flexible network reinforcement were calculated using the two-dimensional finite element method. The results show that the maximum deformation reduced by 55 % after the application of the flexible network reinforcement, from 45.99 to 20.75 ram, which demonstrates that the flexible network method is effective, and can provide some scientific basis for the treatment of dangerous rock masses. 相似文献
13.
V. F. Fateev A. I. Zharikov V. P. Sysoev E. A. Rybakov F. R. Smirnov 《Doklady Earth Sciences》2017,472(1):91-94
The results of the Russia’s first ground-based experiment for determination of the difference in the Earth’s gravitational potentials on the basis of the measurement of the gravitational effect of the time delay with the help of a high-stability transportable atomic clock are provided. The reference atomic clock was placed in Moscow oblast, and a transportable quantum clock with an instability of 3 × 10–15 was placed in the Caucasus Mountains, with a difference in height of the clocks of 1804 m. The measured difference in the gravitational potentials between the positions of the two quantum clocks was (182.0 ± 3.1)102m2s-2 at a relative measurement error of no more than 1.7%. 相似文献
14.
Natural Hazards - Major earthquakes in a given location are unpredictable, infrequent, and often fatal. Using data from a previous earthquake disaster, this study explores the relationship between... 相似文献
15.
《Quaternary Science Reviews》2004,23(11-13):1435-1454
Numerous short sediment cores have been retrieved from the central Arctic Ocean, many of which have been assigned sedimentation rates on the order of mm/ka implying that the Arctic Basin was starved of sediments during Plio–Pleistocene times. A review of both shorter-term sedimentation rates, through analysis of available sediment core data, and longer-term sedimentation rates, through estimates of total sediment thickness and bedrock age, suggests that cm/ka-scale rates are pervasive in the central Arctic Ocean. This is not surprising considering the physiographic setting of the Arctic Ocean, being a small land-locked basin since its initial opening during Early Cretaceous times. We thus conclude that the central Arctic Ocean has not been a sediment starved basin, either during Plio–Pleistocene times or during pre-Pliocene times. Rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of ∼2600 km, from the northwestern Amerasia Basin to the northwestern Eurasia Basin via the Lomonosov Ridge, using paleomagnetic, biostratigraphic, and cyclostratigraphic data. 相似文献
16.
Lobkovskiy L. I. Sokolov S. D. Sorokhtin N. O. Kononov M. V. 《Doklady Earth Sciences》2021,500(2):809-815
Doklady Earth Sciences - The popular rotational hypothesis of the formation and evolution of the main structures of the Eastern Arctic lithosphere during the Late Jurassic–Early Cretaceous,... 相似文献
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The launch of the Spektrum-Roentgen-Gamma (SRG) international orbiting astrophysical observatory is planned for the near future. It is planned tomaneuver SRGinto the vicinity of the L2 libration point of the Sun–Earth system, where it will be kept in a quasi-stable orbit. The spacecraft orbit must be maintained in order to carry out the scientific program of the project, which requires obtaining information about the current parameters of its motion. With the aim of developing methods for making optical measurements and estimating the required volume of measurement data and their accuracy, observations of the Gaia spacecraft, which is located in the vicinity of L2, were made at the Sayan Observatory in 2014–2015. The results of observations of the Gaia spacecraft on the 1.6-m infrared telescope of the Sayan Observatory are presented. The measured brightness of the spacecraft was 20.7–22m, which is close to the limiting magnitude of the telescope. The accuracy of these astrometric measurements was about one arcsecond. Possibilities for obtaining accurate astrometric data for the SRG spacecraft in orbit in the vicinity of L2 are discussed, as well as the required observing conditions and the volume of measurement data required for adequate prediction of the spacecraft motion. 相似文献
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Doklady Earth Sciences - This paper analyzes measurement data on the ionic composition of the upper atmosphere at altitudes of 810–830 km in the period from 2009 to 2018; the measurements... 相似文献
20.
Rudolf Trümpy (1921–2009) was one of the great Alpine geologists of the twentieth century and an influential figure in the
international geological community. He played a dominant role in the change of opinion concerning the Alpine evolution by
showing that normal faulting dominated the early development of the Alpine realm from the Triassic to the early Cretaceous.
This provided a convenient model for later plate-tectonic interpretations of collisional mountain belts. His further recognition
of strike-slip faulting during all stages of the Alpine evolution presaged the realisation that the Alps were not built by
a simple open-and-shut mechanism. Trümpy was educated during an intellectual lull, a time when simplistic models of the earth
behaviour inherited from the middle of the nineteenth century became prevalent under the influence of a close-minded, positivist
approach to geological problems. This period, which we term the Dark Intermezzo, lasted from about 1925 to 1965. The grand
syntheses of Suess and Argand which preceded this period were viewed from this narrow angle and consequently misunderstood.
It was thought that earth history was punctuated by global orogenic events of short duration taking place within and among
continents and oceans whose relative positions had remained fixed since the origin of the planet. These views, summarised
under the term ‘fixism’, were developed when the ocean floors were almost totally unknown. When data began coming in from
the post World War II oceanographic surveys, the world geological community was slow to receive and digest them. Trümpy followed
these developments closely, realising that his work was important in placing the geology of the mountain belts within the
emerging, new theoretical framework. He adopted the position of a critic and emphasised where detailed knowledge of the Alps,
unquestionably the best known mountain belt in the world, supported and where it contradicted the new ideas. His voice was
listened to carefully and subsequent developments have shown his critique to have been prescient. It is regrettable that he
did not publish some of the theoretical criticisms he communicated to his colleagues during scientific meetings and informal
conversations. His hesitance in becoming involved in theoretical arguments in geology may have stemmed partly from his scientific
upbringing during the Dark Intermezzo and partly because he genuinely believed that he was better off sticking to what he
thought he knew for sure. He nevertheless stressed that it is important for geologists ‘to dream’. It is often said about
teachers that one should do what they say, not what they do. In Trümpy’s case, it was the opposite. Both scientifically and
as a human being, he was a most admirable man. 相似文献