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71.
J. L. Simón M. A. Soriano L. E. Arlegui J. Gracia C. L. Liesa A. Pocoví 《Environmental Geology》2008,53(5):1057-1065
Space and time variations of alluvial karst subsidence in the central Ebro Basin are analysed in trenches (paleodolines),
aerial photographs (historical dolines) and field surveys (present-day active dolines). The measured subsidence rates, as
well as a comparison between densities of paleodolines computed in randomly selected scan-lines and density of active dolines
computed in maps, suggest that present-day subsidence in favourable areas is more intense than that of Pleistocene times.
According to diachronic maps drawn from (a) different aerial photographs taken after 1946 and (b) field surveys on deformations
in urbanized areas, subsidence behaved as a nearly steady process while the whole area was used for agriculture. In contrast,
rapid changes (through periods of several tens of years) have occurred in urbanized areas, in which dolines expand their boundaries
through small marginal collapses, shifting sharply their sinking centres to neighbouring sites. These rapid changes do not
have an equivalent in observed paleodolines. 相似文献
72.
Tõnu Viik 《Earth, Moon, and Planets》1990,49(2):163-175
The discrete ordinale method by Chandrasekhar is used to solve the conservative Milne problem in a homogeneous plane-parallel atmosphere which scatters the radiation according to the Rayleigh-Cabannes law.The approximate solution which is supposed to converge uniformly to an exact one when increasing the order of approximation is obtained explicitly. In addition to a tabulation of the Hopf vector for different factors of depolarization, the extrapolation distance, the values of c, q and the Rubenson degrees of polarization at the limb are given. 相似文献
73.
Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: Relationships to Gondwana breakup and passive margin development 总被引:1,自引:0,他引:1
Silvio T. Hiruma Claudio Riccomini May C. Modenesi-Gauttieri Peter C. Hackspacher Julio C. Hadler Neto Ana O.B. Franco-Magalhes 《Gondwana Research》2010,18(4):674-687
The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins. 相似文献
74.
P. Lafuente L. E. Arlegui C. L. Liesa J. L. Simón 《International Journal of Earth Sciences》2011,100(7):1713-1732
The Concud fault is a 13.5 km long, NW–SE striking normal fault at the eastern Iberian Chain. Its recent (Late Pleistocene)
slip history is characterized from mapping and trench analysis and discussed in the context of the accretion/incision history
of the Alfambra River. The fault has been active since Late Pliocene times, with slip rates ranging from 0.07 to 0.33 mm/year
that are consistent with its present-day geomorphologic expression. The most likely empirical correlation suggests that the
associated paleoseisms have potential magnitudes close to 6.8, coseismic displacements of 2.0 m, and recurrence intervals
from 6.1 to 28.9 ka. At least six paleoseismic events have been identified between 113 and 32 ka. The first three events (U
to W) involved displacement along the major fault plane. The last three events (X to Z) encompassed downthrow and hanging-wall
synthetic bending prompting fissure opening. This change is accompanied by a decrease in slip rate (from 0.63 to 0.08–0.17 mm/year)
and has been attributed to activation of a synthetic blind fault at the hanging wall. The average coseismic displacement (1.9–2.0 m)
and recurrence period (6.7–7.9 ka) inferred from this paleoseismic succession are within the ranges predicted from empirical
correlation. Such paleoseismic activity contrasts with the moderate present-day seismicity of the area (maximum instrumental
Mb = 4.4), which can be explained by the long recurrence interval that characterizes intraplate regions. 相似文献
75.
Andres Simón-Moral Jose Luis Santiago Alberto Martilli 《Boundary-Layer Meteorology》2017,163(1):103-121
A Reynolds-averaged Navier–Stokes microscale model is used for the simulation of the effect of unstable thermal stratification on the flow within an aligned configuration of building-like cubes as used in Santiago et al. (Urban Clim 9:115–133, 2014). The spatially-averaged results show increased dispersive fluxes, turbulent length scales and sectional drag coefficient. An extension of K-theory is presented to parametrize the sum of the turbulent and dispersive fluxes, and the length scale and drag coefficient increases are parametrized as functions of the ratio of buoyant and inertial forces. This approach improves the results of urban canopy parametrization simulations inside and above the urban canyon and represents the first attempt to account for the dispersive fluxes and the effect of solar radiation on the flow. 相似文献
76.
A. Aghaee P. Petitjean R. Srianand C. S. Stalin R. Guimarães 《Journal of Astrophysics and Astronomy》2010,31(2):59-79
In recent years, the Lyman-α forest in quasar spectra has been used, together with N-body simulations, to determine the underlying matter distribution in the intergalactic medium (IGM). One of the key parameters
to be known in order to compare observations and numerical simulations is the mean HI absorption in the IGM. To derive the
latter, one has first to fit the quasar continuum. We have observed 20 high redshift and highly luminous QSOs (m
V ≤ 17.5 and 2.40 ≤ z
em ≤ 3.91) at intermediate spectral resolution, with either EMMI (ESO Multi-Mode Instrument) on the ESO-NTT telescope or CARELEC
at the OHP (Observatoire de Haute-Provence), and applied different methods of determining the QSO continuum to this QSO sample.
We have measured the amount of absorption, known as the flux decrement, DA, in the Lyman-α forest for these different methods and compared the results. In addition, we have compared DA values measured along the same lines of sight observed at high and intermediate spectral resolutions. We discuss the systematics
resulting from the use of automatic continuum fitting methods. 相似文献
77.
78.
The development of surface hydrological connectivity is a key determinant of flood magnitude in drylands. Thresholds in runoff response may be reached when isolated runoff-generating areas connect with each other to form continuous links to river channels, enabling these areas to contribute to flood hydrographs. Such threshold behaviour explains observed nonlinearities and scale dependencies of dryland rainfall–runoff relationships and complicates attempts at flood prediction. However, field methods for measuring the propensity of a surface to transmit water downslope are lacking, and conventional techniques of infiltration measurement are often inappropriate for use on non-agricultural drylands. Here, we argue for a reconceptualization of the dryland surface runoff process, suggesting that the downslope transfer of water should be considered alongside surface infiltration; that is, there is a need for the “aggregated” measurement of infiltration and overland flow hydraulics. Surface application of a set volume of water at a standardized rate generates runoff that travels downslope; the distance it travels downslope is determined by infiltration along the flow, integration of flow paths, and flow resistance. We demonstrate the potential of such a combined measurement system coupled with structure-from-motion photogrammetry to identify surface controls on runoff generation and transfer on dryland hillslopes, with vegetation, slope, surface stone cover, and surface roughness all having a significant effect. The measurement system has been used on slopes up to 37° compared with the flat surface typically required for infiltration methods. On average, the field workflow takes ~10–15 min, considerably quicker than rainfall simulation. A wider variety of surfaces can be sampled with relative ease, as the method is not restricted to stone and vegetation-free land. We argue that this aggregated measurement represents surface connectivity and dryland runoff response better than standard hydrological approaches and can be applied on a much greater variety of dryland surfaces. 相似文献
79.
80.
Fernando?G.?BastanteEmail authorView authors OrcID profile Elena?Alonso María?Araújo Julio?García Menéndez 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(9):2605-2618
Goodness of empirical models for predicting explosive detonation velocity and pressure was analysed using 3 databases consisting of experimental velocity and pressure measurements for different explosives. The first database was used to estimate experimental errors for detonation velocity and pressure measurements. The second database was used to compare residuals obtained by the experimental models and by various thermochemical codes. Finally, the third database, consisting of some 600 data on 130 explosive substances, was used to estimate residual bias and dispersion resulting from the application of the experimental models. Also analysed was model coherence with the ideal detonation theory. Our main conclusion is that all the models introduce bias in their predictions depending on the density and oxygen balance values of the explosive. Of those analysed, the Xiong model was notable for its good results, with residual dispersion comparable to that obtained from application of the best thermochemical codes. Our results would indicate that the Xiong model is the only model that may be compatible with the ideal detonation theory. The pressure equation derived from the ideal detonation theory and calibrated with experimental data had excellent predictive capacity. 相似文献