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671.
M. Beatriz Aguirre-Urreta Pablo J. Pazos Darío G. Lazo C. Mark Fanning Vanesa D. Litvak 《Journal of South American Earth Sciences》2008,26(1):91-99
A high-resolution ion-microprobe (SHRIMP) U–Pb zircon age from a tuff layer intercalated in the ammonoid bearing sedimentary succession of the Neuquén Basin in Argentina provides a robust geochronologic date to add to the absolute ages and to improve the relative chronology of the Early Cretaceous Hauterivian stage. The tuff layer appears interbedded between shales of the upper member (Agua de la Mula) of the Agrio Formation within the Spitidiscus riccardii ammonoid zone (base of the Late Hauterivian) yielding a date of 132.5 ± 1.3 Ma. This date confirms and supports an accurate correlation between the ammonoid biostratigraphy of the Neuquén Basin with the Western Mediterranean Province of the Tethys during the Early Cretaceous and matches with the most recently published time scale. It also casts doubts on the validity of K–Ar ages on glauconite-grains recently reported from the Lower Cretaceous of the Vocontian Basin of France. 相似文献
672.
David P. Bacon Nash’at N. Ahmad Thomas J. Dunn Michael C. Monteith Ananthakrishna Sarma 《Natural Hazards》2008,44(3):317-327
By definition, a crisis is a situation that requires assistance to be managed. Hence, response to a crisis involves the merging
of local and non-local emergency response personnel. In this situation, it is critical that each participant: (1) know the
roles and responsibilities of each of the other participants; (2) know the capabilities of each of the participants; and (3)
have a common basis for action. For many types of natural disasters, this entails having a common operational picture of the unfolding events, including detailed information on the weather, both current and forecasted, that may impact on either
the emergency itself or on response activities. The Consequences Assessment Tool Set (CATS) is a comprehensive package of
hazard prediction models and casualty and damage assessment tools that provides a linkage between a modeled or observed effect
and the attendant consequences for populations, infrastructure, and resources, and, hence, provides the common operational
picture for emergency response. The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric
simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies
with numerical weather prediction to provide specific weather analysis and forecast capability that can be merged into the
geographic information system framework of CATS. This paper documents the problem of emergency response as an end-to-end system
and presents the integrated CATS–OMEGA system as a prototype of such a system that has been used successfully in a number
of different situations. 相似文献
673.
Gregory P. Marchildon Suren Kulshreshtha Elaine Wheaton Dave Sauchyn 《Natural Hazards》2008,45(3):391-411
Agriculture in the southern Great Plains of Canada has been particularly vulnerable to prolonged episodes of drought. Using
climate data and a precipitation minus potential evapotranspiration index, the extent of the region’s exposure to drought
is examined. Between 1914 and 1917, the Dry Belt was particularly vulnerable to drought, whereas after 1928, a much larger
region known as the Palliser Triangle covering most of southern Alberta and Saskatchewan was much more exposed to drought.
These droughts provoked major institutional adaptation, in particular the establishment of the Special Areas Board by the
Government of Alberta, and the creation of the Prairie Farm Rehabilitation Administration by the Government of Canada. Both
organizations have proved to be relatively permanent public adaptations to the natural hazard of drought in the region. Moreover,
these earlier experiences with prolonged drought as well as institution-building may be of value in helping the residents
of the Palliser Triangle adapt to predicted climate changes in the future as well as anticipate some of the barriers to effective
institutional adaptation. 相似文献
674.
In this study, households’ decisions on reconstruction of damaged houses were modeled, using questionnaire data in Japan.
Characteristics of households’ decisions were investigated using parameter estimation results. The effects of subsidizing
policy were evaluated as follows. First, subsidy for rebuilding may be effective for the households whose houses were heavily
damaged. Second, there is a possibility that subsidy accelerated rebuilding of houses by the households having children. Third,
subsidy for rebuilding may not be effective for elderly people’s households and households in depopulated areas. 相似文献
675.
Flood hazard delineation combining geomorphological and hydrological methods: an example in the Northern Iberian Peninsula 总被引:2,自引:1,他引:1
Flood mapping requires the combination and integration of geomorphological and hydrological-hydraulic methods; however, despite
this, there is very little scientific literature that compares and validates both methods. Two types of analysis are addressed
in the present article. On the one hand, maps of flood plains have been elaborated using geomorphological evidence and historical
flood data in the mountainous area of northwestern Spain, covering an area of more then 232 km2 of floodplains. On the other hand, a hydrometeorological model has been developed (Clark semidistributed unit hydrograph)
in the Sarria River basin (155 km2, NW Spain). This basin is not gauged, hence the model was subjected to a goodness-of-fit test of its parameter (curve number)
by means of Monte Carlo simulation. The peak flows obtained by means of the hydrological model were used for hydraulic modeling
(one-phase, one-dimensional and steady flow) in a 4 km2 urban stretch of the river bed. The delineation of surface areas affected by floods since 1918, as well as those analyzed
subsequent to the geomorphological study, reveals a high degree of reliability in the delineation of the flooded areas with
frequent recurrence intervals (<50 years). If we compare these flooded surface areas with the estimate obtained by the hydrological-hydraulic
method we can see that the latter method overestimates the extent of the surface water by 144% for very frequent recurrence
intervals (>10 years) and underestimates it as the recurrence interval increases, by up to 80% less floodplain for exceptional
events (>500 years). Finally, a management map is put forth combining the most reliable results available by integrating both
methods.
Originally presented at the Sixth International Conference on Geomorphology. 相似文献
676.
Gravitational spreading of mountain ridges displays primary disequilibrium of flysch mountain areas of the Czech Carpathians.
The progression of various types of mass movements is a product of long-term ridge disintegration and is predisposed by the
geological structure of the area and the upper Tertiary-Quaternary morphogenesis of the mountain area. Deep-seated slope deformations
are spatially interconnected by the occurrence of some other types of slope deformations (e.g. debris flows, debris slides,
slumps, rock avalanches, etc.), which pose a considerable risk for the existence of human society. An important causative
factor in these dynamically developing hazardous processes is, among other factors, the way in which land has been used in
the last three centuries. Therefore, the occurrence of various types of slope deformations is studied in terms of their relation
to deep-seated gravitational deformations and in terms of other limiting factors (structural geological, morphological and
climatic factors, manmade impacts, etc.). The paper presents several case studies of slope deformations (Velká Čantoryje Mt,
Lysá hora Mt, Ropice Mt and Smrk Mt) in the area of the Outer Carpathians within the territory of the Czech Republic and also
adverts to some consequences in terms of the socioeconomic structure of the landscape. 相似文献
677.
Prakash C. Sinha Indu Jain Neetu Bhardwaj Ambarukhana D. Rao Shishir K. Dube 《Natural Hazards》2008,45(3):413-427
The Orissa coast of India is one of the most vulnerable regions of extreme sea levels associated with severe tropical cyclones.
There was extensive loss of life and property due to the October 1999 super cyclone, which devastated large part of the Orissa
coast. The shallow nature of the head bay, presence of a large number of deltas formed by major rivers of Orissa such as Mahanadi
and Dhamra, and high tidal range are responsible for storm surge flooding in the region. Specifically, rising and falling
tidal phases influence the height, duration, and arrival time of peak surge along the coast. The objective of the present
study is to evaluate the tide-surge interaction during the 1999 Orissa cyclone by using nonlinear vertically integrated numerical
models. The pure tidal solution for the head bay region of the Bay of Bengal provides the initial condition for the fine resolution
nested grid Orissa model. However, the feedback from the Orissa model does not affect the head bay model as the study provides
a one-way interaction. Numerical experiments are performed to study the tide-surge interaction by considering various relative
phases of the tidal waves with the surge-wave produced by 1999 Orissa cyclone. The comparison, although utilizing only the
limited estimates of tidal data, appears adequate to assert that the principal features are reproduced correctly. 相似文献
678.
Stephan Lowitzer Dan J. Wilson Björn Winkler Victor Milman Julian D. Gale 《Physics and Chemistry of Minerals》2008,35(3):129-135
Knowledge of the defect properties of Lunar and Mercurian minerals has recently become important, with the advent of models
which attempt to explain the formation of the thin exosphere of these celestial bodies. Here, we have calculated the formation
energies of sodium and oxygen vacancies in the mineral albite (NaAlSi3O8), as well as the Schottky defect energy for the removal of a Na2O unit. We have employed both the supercell and Mott–Littleton approaches, using Kohn–Sham density functional theory and classical
interatomic potential methods. As well as reporting the defect energies and structures, we comment upon the relative merits
of the methods used. 相似文献
679.
D. J. Cherniak 《Physics and Chemistry of Minerals》2008,35(4):179-187
Self-diffusion of Si under anhydrous conditions at 1 atm has been measured in natural zircon. The source of diffusant for
experiments was a mixture of ZrO2 and 30Si-enriched SiO2 in 1:1 molar proportions; experiments were run in crimped Pt capsules in 1-atm furnaces. 30Si profiles were measured with both Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis with the resonant
nuclear reaction 30Si(p,γ)31P. For Si diffusion normal to c over the temperature range 1,350–1,550°C, we obtain an Arrhenius relation D = 5.8 exp(−702 ± 54 kJ mol−1/RT) m2 s−1 for the NRA measurements, which agrees within uncertainty with an Arrhenius relation determined from the RBS measurements
[62 exp(−738 ± 61 kJ mol−1/RT) m2 s−1]. Diffusion of Si parallel to c appears slightly faster, but agrees within experimental uncertainty at most temperatures
with diffusivities for Si normal to c. Diffusion of Si in zircon is similar to that of Ti, but about an order of magnitude faster than diffusion of Hf and two
orders of magnitude faster than diffusion of U and Th. Si diffusion is, however, many orders of magnitude slower than oxygen
diffusion under both dry and hydrothermal conditions, with the difference increasing with decreasing temperature because of
the larger activation energy for Si diffusion. If we consider Hf as a proxy for Zr, given its similar charge and size, we
can rank the diffusivities of the major constituents in zircon as follows: D
Zr < D
Si << D
O, dry < D
O, ‘wet’. 相似文献
680.
Flaring of associated gas from oil exploitation has several consequences on the environment. This study explores the spatial
variability effects of gas flaring on the growth and development of cassava (Manihot esculenta), waterleaf (Talinum triangulare), and pepper (Piper spp.) crops commonly cultivated in the Niger Delta, Nigeria. Data was collected on soil and atmospheric temperature and moisture
at a 20-m interval, starting at 40 m from the flare point to a distance of 140 m. Lengths and widths of crop leaves, height
of crop plants and cassava yields were measured at the specified distances. The amino acid, ascorbic acid, starch, and sugar
constituents of the cassava yields were determined. The results suggest that a spatial gradient exists in the effects of gas
flares on crop development. Retardation in crop development manifests in decreased dimensions of leaf lengths and widths of
cassava and pepper crops closer to the gas flare point. Statistical analysis also confirms that cassava yields are higher
at locations further away from the flare point. In addition, the amount of starch and ascorbic acid in cassava decreased when
the plant is grown closer to the gas flare. High temperatures around the gas flare appear to be the most likely cause of this
retardation. The waterleaf crop, on the other hand, appears to thrive better around the gas flare point. 相似文献