Oceanic–atmospheric modes of variability and their influence on riverine input to coastal Louisiana and Mississippi     

Guillermo Sanchez-Rubio  Harriet M. Perry  Patricia M. Biesiot  Donald R. Johnson  Romuald N. Lipcius 《Journal of Hydrology》2011,396(1-2):72-81

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Regional VS30 model for the St. Lawrence Lowlands,Eastern Canada     

Miroslav Nastev  Michel Parent  Nicolas Benoit  Martin Ross  Danielle Howlett 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(3):200-212

Shear-wave velocity of the top 30?m, V_S30, is commonly used for prediction of the seismic site response. This paper presents development, validation and uncertainty assessment of a regional V_S30 model based on a combination of simplified 3D geology and statistically representative velocity values. Results identify soft marine sediments in deep sedimentary basins as zones most susceptible to seismic shaking. Compared to the available urban-scale seismic zonation studies, the regional model showed a success rate of roughly 64% in predicting local site category. The standard deviation was in average 30% of the expected V_S30 value.  相似文献   

The relation between dilatancy,effective stress and dispersive pressure in granular avalanches     

Perry Bartelt  Othmar Buser 《Acta Geotechnica》2016,11(3):549-557

Here we investigate three long-standing principles of granular mechanics and avalanche science: dilatancy, effective stress and dispersive pressure. We first show how the three principles are mechanically interrelated: Shearing of a particle ensemble creates a mechanical energy flux associated with random particle movements (scattering). Because the particle scattering is inhibited at the basal boundary, there is a spontaneous rise in the center of mass of the particle ensemble (dilatancy). This rise is connected to a change in potential energy. When the center of mass rises, there is a corresponding reaction at the base of the flow that is coupled to the vertical acceleration of the ensemble. This inertial stress is the dispersive pressure. Dilatancy is therefore not well connected to effective-stress-type relations, rather the energy fluxes describing the configurational changes of the particle ensemble. The strict application of energy principles has far-reaching implications for the modeling of avalanches and debris flows and other dangerous geophysical hazards.  相似文献   

Does Anzac Sit Comfortably within Australia's Multiculturalism?     

Danielle Drozdzewski 《The Australian geographer》2016,47(1):3-10

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A new record of Pleistocene hippopotamus from River Severn terrace deposits, Gloucester, UK—palaeoenvironmental setting and stratigraphical significance     

Danielle C. Schreve 《Proceedings of the Geologists' Association. Geologists' Association》2009,120(1):58-64

A new Pleistocene vertebrate assemblage from fluvial deposits of the River Severn in Gloucester, England, has yielded the remains of hippopotamus (Hippopotamus amphibius), a new record for this terrace system, with additional material from probable bison (cf. Bison priscus) and elephant (Elephantidae sp.). The presence of these taxa indicates fully temperate climatic conditions and the occurrence of hippopotamus, a significant biostratigraphical indicator for the British Late Pleistocene, suggests an age for the assemblage within MIS 5e (the Last Interglacial). This would contradict the older MIS 7-6 age for the gravel body that is currently accepted on the basis of deposit mapping and imply a more complex mode of deposition than presently envisaged in the valley.  相似文献   

Differentiation of MIS 9 and MIS 11 in the continental record: vegetational,faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex,UK     

Helen M. Roe  G. Russell Coope  Robert J.N. Devoy  Colin J.O. Harrison  Kirsty E.H. Penkman  Richard C. Preece  Danielle C. Schreve 《Quaternary Science Reviews》2009,28(23-24):2342-2373

Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.  相似文献   

Neubenennungen lithostratigraphischer Einheiten in der Helvetischen Kreide     

Schweizerisches Komitee für Stratigraphie  Thierry Adatte  Jean-Pierre Berger  Hansruedi Bläsi  Reto Burkhalter  Stephan DallAgnolo  Danielle Decrouez  Hanspeter Funk  Heinz Furrer  Yves Gouffon  Hansruedi Graf  Werner Heckendorn  Wilfried Winkler 《Swiss Journal of Geoscience》2009,102(2):363-364

In September 2007 Föllmi and coauthors requested the approval of four lithostratigraphic terms of the Swiss Committee of Stratigraphy (SCS). These terms were to be used in their publication on the Cretaceous in the Helvetic realm (Föllmi et al. 2007). At its meeting on October 18, 2007, the SCS decided the following: The Tierwis Formation (replacing the Drusberg Formation) was accepted, with the reserve that a section at Tierwis should be published in the near future. For the former “Lower Orbitolina Beds” the term Rawil Member was accepted, but here too a better type section than the one at Rawil Pass should be published. The term Rohrbachstein bed should not be used as a formal unit because it describes only a minor lithologic variation within the Grünten Member. The term Plaine Morte bed for a thin condensed horizon can not be accepted due to the fact that its definition is based mainly on biostratigraphy. Furthermore, the duplication a locality term which is in use for a previously established lithostratigraphic unit should be avoided.  相似文献   

First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line     

Richard A. Harrison  Christopher J. Davis  Christopher J. Eyles  Danielle Bewsher  Steve R. Crothers  Jackie A. Davies  Russell A. Howard  Daniel J. Moses  Dennis G. Socker  Jeffrey S. Newmark  Jean-Philippe Halain  Jean-Marc Defise  Emmanuel Mazy  Pierre Rochus  David F. Webb  George M. Simnett 《Solar physics》2008,247(1):171-193

We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun – Earth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the corona to over 40 degrees. The time – altitude history shows a constant speed of ascent over at least the first 50 solar radii and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere. Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona of Koutchmy and Lamy (IAU Colloq. 85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific example at 40 solar radii revealed CME intensities as low as 1.7×10⁻¹⁴ of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in particular, Earth-directed CMEs into the heliosphere.  相似文献   

Measurement of Ejecta from Normal Incident Hypervelocity Impact on Lunar Regolith Simulant     

David L. Edwards  William Cooke  Danielle E. Moser  Wesley Swift 《Earth, Moon, and Planets》2008,102(1-4):549-553

The National Aeronautics and Space Administration (NASA) continues to make progress toward long-term lunar habitation. Critical to the design of a lunar habitat is an understanding of the lunar surface environment. A subject for further definition is the lunar impact ejecta environment. The document NASA SP-8013 was developed for the Apollo program and is the latest definition of the ejecta environment. There is concern that NASA SP-8013 may over-estimate the lunar ejecta environment. NASA’s Meteoroid Environment Office (MEO) has initiated several tasks to improve the accuracy of our understanding of the lunar surface ejecta environment. This paper reports the results of experiments on projectile impact into powered pumice targets, simulating unconsolidated lunar regolith. The Ames Vertical Gun Range (AVGR) was used to accelerate spherical Pyrex projectiles of 0.29g to velocities ranging between 2.5 and 5.18 km/s. Impact on the pumice target occurred at normal incidence. The ejected particles were detected by thin aluminum foil targets placed around the pumice target in a 0.5 Torr vacuum. A simplistic technique to characterize the ejected particles was formulated. Improvements to this technique will be discussed for implementation in future tests.  相似文献   

Thermal infrared video details multiscale groundwater discharge to surface water through macropores and peat pipes          下载免费PDF全文

Martin A. Briggs  Danielle K. Hare  David F. Boutt  Glorianna Davenport  John W. Lane 《水文研究》2016,30(14):2510-2511

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