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31.
Jakob Fjellanger Leif Srbel Henriette Linge Edward J. Brook Grant M. Raisbeck Franoise Yiou 《Geomorphology》2006,82(3-4):255-272
For more than hundred years it has been debated whether blockfields in mountain summit areas can be used to delimit the vertical extent of Pleistocene ice sheets. In this study the relationship between blockfields, developed in quartzites and sandstones on the Varanger Peninsula, northern Norway, and glacially derived features have been evaluated. Erratics and circular ablation moraines are superimposed on the blockfields and lateral meltwater channels are eroded into them. Glacial striations and other signs of glacial sculpturing are restricted to low-lying areas with channelled ice flow. Relative ages of the blockfields and the features in them are inferred, and the first measurements of in-situ produced cosmogenic nuclides from the Varanger Peninsula are reported. We conclude that the blockfields have survived underneath at least one thick, cold-based ice sheet. Thus, these blockfields cannot be used as indicators of ice-free conditions as previously suggested for southern Norway. Our results have implications for the potential for land surface preservation beneath ice sheets and for glacial reconstructions in northern Fennoscandia. 相似文献
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Seismic Hazards Assessment for Radioactive Waste Disposal Sites in Regions of Low Seismic Activity 总被引:4,自引:0,他引:4
Clark H. Fenton John Adams Stephen Halchuk 《Geotechnical and Geological Engineering》2006,24(3):579-592
A comparative tectonic quiescence and lack of earthquakes make the stable centres of continents attractive for siting long-term
radioactive waste storage facilities. The low rates of deformation in such regions, however, make it difficult to characterize
their long-term seismotectonic behaviour, leading to uncertain estimates for the very low probability hazard estimates required
by society. In an attempt to overcome the deficiency of both contemporary seismicity and paleoseismic data in central Canada,
we have used earthquake histories from regions with similar seismotectonic characteristics from around the world. Substituting
space for time, we estimate a long-term rate per 106 km2 of 0.004 magnitude ≥6 earthquakes per annum, of which 33–100% might rupture to the surface. 相似文献
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37.
Laboratory Studies Of Wind Stress Over Surface Waves 总被引:4,自引:0,他引:4
Simultaneous laboratory observations of wind speed, wind stress, and surfacewind-wave spectra are made under a variety of wind forcing patterns using cleanwater as well as water containing an artificial surfactant. Under typical experimentalconditions, more than half of the total stress is supported by the wave-induced stressrather than by the surface viscous stress. When the surfactant reduces the shortwind-wave spectra, the wind stress also decreases by as much as 20–30% at agiven wind speed. When the wind forcing is modulated in time, the wind stresstends to be higher under decreasing wind than under increasing wind at a givenwind speed, mainly because the response of short wind-wave spectra to varyingwind forcing is delayed in time. These examples clearly demonstrate that therelationship between the wind speed and the wind stress can be significantlymodified if the surface wave field is not in equilibrium with the wind forcing.Next, we examine whether the wind stress is estimated accurately if the wave-inducedstress by all surface wave components is explicitly evaluated by linear superpositionand is added to the surface viscous stress. It is assumed that the surface viscous stressis uniquely related to the wind speed, and that the wind input rate is determined by thelocal, reduced turbulent stress rather than the total stress. Our wind stress estimatesincluding the wave contributions agree well with observed wind stress values, evenif the surface wave field is away from its equilibrium with the wind in the presenceof surface films and/or under time-transient wind forcing. These observations stronglysuggest that the wind stress is accurately evaluated as a sum of the wave-induced stressand the surface viscous stress. At very high winds, our stress estimates tend to be lowerthan the observations. We suspect that this is because of the enhancement of wind stressover very steep (or breaking) short wind-waves. 相似文献
38.
W. M. L. Meijninger A. E. Green O. K. Hartogensis W. Kohsiek J. C. B. Hoedjes R. M. Zuurbier H. A. R. De Bruin 《Boundary-Layer Meteorology》2002,105(1):63-83
A large aperture scintillometer (LAS) andradio wave scintillometer (RWS)were installed over a heterogeneous areato test the applicability of the scintillation method.The heterogeneity in the area, whichconsisted of many plots, was mainly caused bydifferences in thermal properties ofthe crops; the variations in theaerodynamic roughness lengthwere small. The water vapour fluxesderived from the combined LAS-RWSsystem, also known as the two-wavelengthmethod, agreed fairly well with the aggregatedwater vapour fluxes derived from in-situeddy covariance measurements. The water vapourfluxes derived from a stand-alone LASare also presented. It was found that a single LASand an estimate of the area averagedavailable energy (using a simple parameterisationscheme) can provide also reasonablearea-averaged water vapour fluxes. 相似文献
39.
利用欧洲资源卫星1号和2号获取的重轨干涉测量雷达数据,首先进行干涉测量数据相关性估测,并结合干涉测量数据的振幅信息,开展新疆喀什试验区地表土地类型的识别与分类,区分和识别出裸土、盐碱地、灌丛、裸岩/戈壁、沼泽和水体 6类土地类型。最后通过对不同土地类型的后向散射特性和相关性的分析,探讨了干涉测量数据相关性与干旱-半干旱地区地表特征的关系。 相似文献
40.
Marianne Font Jean-Louis Lagarde Daniel Amorese Jean-Pierre Coutard Jean-Claude Ozouf 《Comptes Rendus Geoscience》2002,334(3):171-178
The degradation of the Jobourg fault-scarp occurred by cryoclastic processes in a periglacial environment during a part of Quaternary time. An attempt of quantification indicates a bulk scarp erosion of about 39 m3 m?2, while the head accumulated at the bottom of the fault scarp only represents 4.6 m3 m?2. To cite this article: M. Font et al., C. R. Geoscience 334 (2002) 171–178. 相似文献