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91.
This article presents the development of a relatively low cost and rapidly applicable methodology to simulate the spatio‐temporal occurrence of groundwater flooding in chalk catchments. In winter 2000/2001 extreme rainfall resulted in anomalously high groundwater levels and groundwater flooding in many chalk catchments of northern Europe and the southern United Kingdom. Groundwater flooding was extensive and prolonged, occurring in areas where it had not been recently observed and, in places, lasting for 6 months. In many of these catchments, the prediction of groundwater flooding is hindered by the lack of an appropriate tool, such as a distributed groundwater model, or the inability of models to simulate extremes adequately. A set of groundwater hydrographs is simulated using a simple lumped parameter groundwater model. The number of models required is minimized through the classification and grouping of groundwater level time‐series using principal component analysis and cluster analysis. One representative hydrograph is modelled then transposed to other observed hydrographs in the same group by the process of quantile mapping. Time‐variant groundwater level surfaces, generated using the discrete set of modelled hydrographs and river elevation data, are overlain on a digital terrain model to predict the spatial extent of groundwater flooding. The methodology is applied to the Pang and Lambourn catchments in southern England for which monthly groundwater level time‐series exist for 52 observation boreholes covering the period 1975–2004. The results are validated against observed groundwater flood extent data obtained from aerial surveys and field mapping. The method is shown to simulate the spatial and temporal occurrence of flooding during the 2000/2001 flood event accurately. British Geological Survey © NERC 2011. Hydrological Processes © 2011 John Wiley & Sons, Ltd. 相似文献
92.
Gamma‐ray curves from surface outcrops together with U–Pb SHRIMP zircon dating are used to redefine the evolution of a Palaeoproterozoic sandy dolostone succession from northern Australia. This case history indicates that gamma‐ray logging of surface sections should accompany lithostratigraphic logging or an inadequate interpretation of stratigraphic evolution is a likely outcome. The 1200 m‐thick Nathan Group from the McArthur River area had previously been interpreted as a more‐or‐less continuous package of carbonates deposited in lacustrine and associated shallow‐water environments. Now it is seen to comprise the preserved remnants of three truncated, second‐order supersequences—the Lawn, Wide and Doom Supersequences—each a few hundred metres thick and each deposited over a time period of a few million years. These supersequences are separated by major stratigraphic breaks each approaching probably 10 million years duration. Each supersequence comprises several third‐order sequences which themselves contain higher‐order cycles. These were deposited in a series of continental, shoreline, and inner to outer carbonate platform environments. Transgressive, high‐energy, fluvial to marginal marine, mixed clastic‐carbonate facies dominate most of the sequences. The middle, Wide Supersequence, however, preserves deeper water (mostly sub‐storm‐wave‐base) stromatolitic facies in one sequence, and storm‐reworked clastics in another. These are interpreted as condensed intervals deposited around their respective maximum flooding surfaces and are succeeded by regressive facies that probably represent highstand systems tracts. New correlations between these 1615–1575 Ma sandy carbonate successions of the McArthur Basin (Amos, Balbirini and Dungaminnie Formations) and time‐equivalent largely clastic successions in the Lawn Hill area (Lawn Hill and Doomadgee Formations), some 400 km to the southeast, are proposed. 相似文献
93.
Many lens surveys have hitherto used observations of large samples of background sources to select the small minority which are multiply imaged by lensing galaxies along the line of sight. Recently surveys such as SLACS and OLS have improved the efficiency of surveys by pre-selecting double-redshift systems from SDSS. We explore other ways to improve survey efficiency by optimum use of astrometric and morphological information in existing large-scale optical and radio surveys. The method exploits the small position differences between FIRST radio positions of lensed images and the SDSS lens galaxy positions, together with the marginal resolution of some larger gravitational lens systems by the FIRST beam. We present results of a small pilot study with the VLA and MERLIN, and discuss the desirable criteria for future surveys. 相似文献
94.
M. Chauvin H.-G. Florén M. Jackson T. Kamae T. Kawano M. Kiss M. Kole V. Mikhalev E. Moretti G. Olofsson S. Rydström H. Takahashi J. Lind J.-E. Strömberg O. Welin A. Iyudin D. Shifrin M. Pearce 《Experimental Astronomy》2016,41(1-2):17-41
In the 50 years since the advent of X-ray astronomy there have been many scientific advances due to the development of new experimental techniques for detecting and characterising X-rays. Observations of X-ray polarisation have, however, not undergone a similar development. This is a shortcoming since a plethora of open questions related to the nature of X-ray sources could be resolved through measurements of the linear polarisation of emitted X-rays. The PoGOLite Pathfinder is a balloon-borne hard X-ray polarimeter operating in the 25-240 keV energy band from a stabilised observation platform. Polarisation is determined using coincident energy deposits in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. The PoGOLite Pathfinder was launched from the SSC Esrange Space Centre in July 2013. A near-circumpolar flight was achieved with a duration of approximately two weeks. The flight performance of the Pathfinder design is discussed for the three Crab observations conducted. The signal-to-background ratio for the observations is shown to be 0.25 ±0.03 and the Minimum Detectable Polarisation (99 % C.L.) is (28.4 ±2.2) %. A strategy for the continuation of the PoGOLite programme is outlined based on experience gained during the 2013 maiden flight. 相似文献
95.
We revisit a set of symplectic variables introduced by Andre Deprit (Celest Mech 30, 181–195, 1983), which allows for a complete symplectic reduction in rotation invariant Hamiltonian systems, generalizing to arbitrary dimension
Jacobi’s reduction of the nodes. In particular, we introduce an action-angle version of Deprit’s variables, connected to the
Delaunay variables, and give a new hierarchical proof of the symplectic character of Deprit’s variables. 相似文献
96.
M. M. Bisi B. V. Jackson A. R. Breen G. D. Dorrian R. A. Fallows J. M. Clover P. P. Hick 《Solar physics》2010,265(1-2):233-244
The European Incoherent SCATter (EISCAT) radar has been used for remote-sensing observations of interplanetary scintillation (IPS) for a quarter of a century. During the April/May 2007 observing campaign, a large number of observations of IPS using EISCAT took place to give a reasonable spatial and temporal coverage of solar wind velocity structure throughout this time during the declining phase of Solar Cycle 23. Many co-rotating and transient features were observed during this period. Using the University of California, San Diego three-dimensional (3-D) time-dependent computer assisted tomography (C.A.T.) solar-wind reconstruction analysis, we show the velocity structure of the inner heliosphere in three dimensions throughout the time interval of 20 April through 20 May 2007. We also compare to white-light remote-sensing observations of an interplanetary coronal mass ejection (ICME) seen by the STEREO Ahead spacecraft inner Heliospheric Imager on 16 May 2007, as well as to in-situ solar-wind measurements taken with near-Earth spacebourne instrumentation throughout this interval. The reconstructions show clear co-rotating regions during this period, and the time-series extraction at spacecraft locations compares well with measurements made by the STEREO, Wind, and ACE spacecraft. This is the first time such clear structures have been revealed using this 3-D technique with EISCAT IPS data as input. 相似文献
97.
M. M. Bisi A. R. Breen B. V. Jackson R. A. Fallows A. P. Walsh Z. Mikić P. Riley C. J. Owen A. Gonzalez-Esparza E. Aguilar-Rodriguez H. Morgan E. A. Jensen A. G. Wood M. J. Owens M. Tokumaru P. K. Manoharan I. V. Chashei A. S. Giunta J. A. Linker V. I. Shishov S. A. Tyul’bashev G. Agalya S. K. Glubokova M. S. Hamilton K. Fujiki P. P. Hick J. M. Clover B. Pintér 《Solar physics》2010,265(1-2):49-127
We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching ?263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation. 相似文献
98.
Pietro Marescotti Eva Azzali Diego Servida Cristina Carbone Giovanni Grieco Luisa De Capitani Gabriella Lucchetti 《Environmental Earth Sciences》2010,61(1):187-199
In this work, we investigated a 3 ha sulphide-bearing waste-rock dump (Libiola Mine, Italy) using mineralogical, geochemical,
and geostatistical analyses. The dumped materials were highly heterogeneous in grain size and lithology and varied both laterally
and vertically. Other than the host rock of the ore, basalts and serpentinites, the dumped materials contained high amounts
of low-grade chalcopyrite- and pyrite-rich mineralisations. Due to these characteristics and to the absence of minerals able
to neutralise acidity, this waste-rock dump can be classified as an acid mine drainage (AMD) producer. The study confirms
that AMD is still active and, in the best scenario, can persist for up to 6.17 × 103 years. The consequences of this process are of serious environmental concern as it involves strong acidification of the circulating
waters, the release of potentially toxic metals into the soil, streams and rivers and the precipitation of huge quantities
of secondary Fe-oxides and Fe-oxyhydroxides. 相似文献
99.
Thilo Wrona Alexander C. Whittaker Rebecca E. Bell Robert L. Gawthorpe Haakon Fossen Christopher A.-L. Jackson Marit Stokke Bauck 《Basin Research》2023,35(2):744-761
Our understanding of continental rifting is, in large parts, derived from the stratigraphic record. This record is, however, incomplete as it does not often capture the geomorphic and erosional signal of rifting. New 3D seismic reflection data reveal a Late Permian-Early Triassic landscape incised into the pre-rift basement of the northern North Sea. This landscape, which covers at least 542 km2, preserves a drainage system bound by two major tectonic faults. A quantitative geomorphic analysis of the drainage system reveals 68 catchments, with channel steepness and knickpoint analysis of catchment-hosted palaeo-rivers showing that the landscape preserved a >2 Myr long period of transient tectonics. We interpret that this landscape records a punctuated uplift of the footwall of a major rift-related normal fault (Vette Fault) at the onset of rifting. The landscape was preserved by a combination of relatively rapid subsidence in the hangingwall of a younger fault (Øygarden Fault) and burial by post-incision sediments. As such, we show how and why erosional landscapes are preserved in the stratigraphic record, and how they can help us understand the tectono-stratigraphic evolution of ancient continental rifts. 相似文献
100.
In this study, we integrate 3D seismic reflection, wireline log, biostratigraphic and core data from the Egersund Basin, Norwegian North Sea to determine the impact of syn‐depositional salt movement and associated growth faulting on the sedimentology and stratigraphic architecture of the Middle‐to‐Upper Jurassic, net‐transgressive, syn‐rift succession. Borehole data indicate that Middle‐to‐Upper Jurassic strata consist of low‐energy, wave‐dominated offshore and shoreface deposits and coal‐bearing coastal‐plain deposits. These deposits are arranged in four parasequences that are aggradationally to retrogradationally stacked to form a net‐transgressive succession that is up to 150‐m thick, at least 20 km in depositional strike (SW‐NE) extent, and >70 km in depositional dip (NW‐SE) extent. In this rift‐margin location, changes in thickness but not facies are noted across active salt structures. Abrupt facies changes, from shoreface sandstones to offshore mudstones, only occur across large displacement, basement‐involved normal faults. Comparisons to other tectonically active salt‐influenced basins suggest that facies changes across syn‐depositional salt structures are observed only where expansion indices are >2. Subsidence between salt walls resulted in local preservation of coastal‐plain deposits that cap shoreface parasequences, which were locally removed by transgressive erosion in adjacent areas of lower subsidence. The depositional dip that characterizes the Egersund Basin is unusual and likely resulted from its marginal location within the evolving North Sea rift and an extra‐basinal sediment supply from the Norwegian mainland. 相似文献