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21.
Regional watershed characterization and classification with river network analyses 总被引:1,自引:0,他引:1
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Cédric Gaucherel Romain Frelat Ludovic Salomon Bastien Rouy Neha Pandey Christophe Cudennec 《地球表面变化过程与地形》2017,42(13):2068-2081
In order to understand and manage a hydrological region, one usually needs to comprehensively characterize the watersheds (basins) and their river networks. This usually and primarily involves analysis of hydrological and geomorphological properties of the watershed derived from the digital terrain model (DTM), but this approach neglects the information content of the associated river networks. In this study, we used a combination of traditional DTM and original river network‐related indices to the watersheds of an understudied region, Haiti. We also used Monte Carlo simulations to estimate index confidence levels of these indices. Compared to commonly used indices, the network indices provided valuable information that could then be used in statistical analyses as a way to identify the dominant features of the country's watershed morphology. On this basis, we identified four watershed groups in Haiti: (i) high, elongated watersheds, (ii) lowlands, with sinuous networks and relatively slow runoff, (iii) high watersheds with dendritic networks, and (iv) lowlands with high downstream–upstream contrast in properties and rapid runoffs. We argue that river network features provide complementary information in terms of flow topology, highly relevant to characterize contrasting relief countries, such as Haiti. Hence, more exhaustive characterization of watersheds would predictably benefit from the approach outlined in this paper. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Christian Sue Bastien Delacou Jean‐Daniel Champagnac Cecile Allanic Martin Burkhard 《地学学报》2007,19(3):182-188
Neotectonics of the Western and Central Alps is characterized by ongoing widespread extension in the highest zones of the chain and transcurrent/compressive tectonics at the external limits of the belt. The overall geodetically measured deformations also indicate extension across the Western Alps. There is a good qualitative coherency between seismotectonic and geodetic approaches. Here we attempt to quantify the seismic part of the deformation. The seismic strain is compared to the deformation derived from geodesy. In sub‐areas of homogeneous seismic stress/strain, we computed the total seismic moment tensor and related strain tensor. This study provides new quantitative elements about the ongoing geodynamic processes in the alpine belt. The important discrepancies obtained between seismic strains and geodetically‐measured deformations raise the issue of aseismic deformation in the Alps, which could be related to elastic loading, creeping and/or a slower ductile‐style deformation. 相似文献
24.
Martin Houde Ruisheng Peng Hiroshige Yoshida Roger H. Hildebrand Thomas G. Phillips C. Darren Dowell Pierre Bastien Jessie L. Dotson John E. Vaillancourt 《Astrophysics and Space Science》2004,292(1-4):127-134
We discuss how the combination of polarimetry and ion-to-neutral molecular line width ratio measurements permits the determination of the magnitude and orientation of the magnetic field in the weakly ionized parts of molecular clouds. Polarimetry measurements give the field orientation in the plane of the sky and the ion-to-neutral molecular line width ratio determines the angle between the magnetic field and the line of sight. We show the first results obtained with this technique on the M17 and Orion A star-forming region using Hertz 350 μm polarimetry maps and HCO+-to-HCN molecular line width ratios to provide the first view of the spatial orientation of the magnetic field these molecular clouds. 相似文献
25.
P. Bastien 《Astrophysics and Space Science》1998,260(1-2):135-144
Various aspects of mass loss associated with Young Stellar Objects are reviewed. The classification of the driving sources
of the outflows is presented, and the properties of the youngest sources, the Class 0 protostars, are given. The observed
properties of the molecular, atomic, and neutral components of the bipolar flows are discussed and critically compared with
the most recent theoretical models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
26.
Quantification of strain rate in the Western Alps using geodesy: comparisons with seismotectonics 总被引:1,自引:0,他引:1
Bastien Delacou Christian Sue Jean-Mathieu Nocquet Jean-Daniel Champagnac Cécile Allanic Martin Burkhard 《Swiss Journal of Geoscience》2008,101(2):377-385
The contrasted seismotectonic regime of the Western Alps is characterized by radial extension in the high chain, combined with local compressive areas at the foothill of the belt, and everywhere occurrence of transcurrent tectonics. Here, we compare this seismotectonic regime to a large-scale compilation of GPS measurements in the Western Alpine realm. Our analysis is based on the raw GPS database, which give the measured velocity field with respect to the so called “stable Europe”, and an interpolated velocity field, in order to smooth the database on a more regular mesh. Both strain rate and rotational components of the deformation are investigated. The strain rate field shows patch-like structure, with extensional areas located in the core and to the North of the belt and compressional areas located in its periphery. Although the GPS deformation fields (both raw and interpolated) are more spatially variable than the seismotectonic field, a good qualitative correlation is established with the seismotectonic regionalization of the deformation. The rotation rate fields (both raw and interpolated) present counterclockwise rotations in the innermost part of the belt and a surprising continuous zone of clockwise rotations following the arc-shape geometry of the Western Alps along their external border. We interpret this new result in term of a counterclockwise rotation of the Apulia plate with respect to the stable Europe. This tectonic scheme may induce clockwise rotations of crustal block along the large strike-slip fault system, which runs in the outer part of the belt, from the Rhône-Simplon fault to the Belledonne fault and Southeastward, to the High-Durance and Argentera fault. 相似文献
27.
Effect of anelastic patchy saturated sand layers on the reflection and transmission responses of a periodically layered medium
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Based on analytic relations, we compute the reflection and transmission responses of a periodically layered medium with a stack of elastic shales and partially saturated sands. The sand layers are considered anelastic (using patchy saturation theory) or elastic (with effective velocity). Using the patchy saturation theory, we introduce a velocity dispersion due to mesoscale attenuation in the sand layer. This intrinsic anelasticity is creating frequency dependence, which is added to the one coming from the layering (macroscale). We choose several configurations of the periodically layered medium to enhance more or less the effect of anelasticity. The worst case to see the effect of intrinsic anelasticity is obtained with low dispersion in the sand layer, strong contrast between shales and sands, and a low value of the net‐to‐gross ratio (sand proportion divided by the sand + shale proportion), whereas the best case is constituted by high dispersion, weak contrast, and high net‐to‐gross ratio. We then compare the results to show which dispersion effect is dominating in reflection and transmission responses. In frequency domain, the influence of the intrinsic anelasticity is not negligible compared with the layering effect. Even if the main resonance patterns are the same, the resonance peaks for anelastic cases are shifted towards high frequencies and have a slightly lower amplitude than for elastic cases. These observations are more emphasized when we combine all effects and when the net‐to‐gross ratio increases, whereas the differences between anelastic and elastic results are less affected by the level of intrinsic dispersion and by the contrast between the layers. In the time domain, the amplitude of the responses is significantly lower when we consider intrinsic anelastic layers. Even if the phase response has the same features for elastic and anelastic cases, the anelastic model responses are clearly more attenuated than the elastic ones. We conclude that the frequency dependence due to the layering is not always dominating the responses. The frequency dependence coming from intrinsic visco‐elastic phenomena affects the amplitude of the responses in the frequency and time domains. Considering intrinsic attenuation and velocity dispersion of some layers should be analyzed while looking at seismic and log data in thin layered reservoirs. 相似文献
28.
In Europe and especially in France,there is a growing enthusiasm for outdoor sports and recreation.In the meantime,the risk of both severe and frequent injuries associated with active pursuits is acknowledged,especially in mountainous areas.The effectiveness of prevention must rely on detailed knowledge of typical circumstances and scenarios but thorough understanding of the mechanisms of accidentality remains limited by the fragmentation of sources and by mostly heterogeneous methodologies.This paper aims at giving insights on victims’profiles,season,location,and circumstances of mountaineering accidents in the French Alps,through the study of rescue interventions data from 2008 to 2018.Thanks to the analysis of the exhaustive database of search and rescue interventions from the French mountain national police force,and while questioning its limitations,we strive to answer two questions:what are the characteristics of the hazardous situations leading to a rescue intervention in mountaineering?Among these situations,what are the characteristics that tend to make them more harmful? 相似文献
29.
Bastien Soens Matthias van Ginneken Stepan Chernonozhkin Nicolas Slotte Vinciane Debaille Frank Vanhaecke Herman Terryn Philippe Claeys Steven Goderis 《地学前缘(英文版)》2021,(4):202-214
The ~790 ka Australasian (micro)tektite strewn field is one of the most recent and best-known examples of im-pact ejecta emplacement as the result of a large-sc... 相似文献
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Qing He Kwok Pan Chun Mou Leong Tan Bastien Dieppois Liew Juneng Julian Klaus Matthieu Fournier Nicolas Massei Omer Yetemen 《水文研究》2021,35(9):e14356
Ocean–atmosphere modes of climate variability in the Pacific and Indian oceans, as well as monsoons, regulate the regional wet and dry episodes in tropical regions. However, how those modes of climate variability, and their interactions, lead to spatial differences in drought patterns over tropical Asia at seasonal to interannual time scales remains unclear. This study aims to analyse the hydroclimate processes for both short- and long-term spatial drought patterns (3-, 6, 12- and 24-months) over Peninsular Malaysia using the Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, and Palmer Drought Severity Index. Besides that, a generalized least squares regression is used to explore underlying circulation mechanisms of these spatio-temporal drought patterns. The tested drought indices indicate a tendency towards wetter conditions over Peninsular Malaysia. Based on principal component analysis, distinct spatio-temporal drought patterns are revealed, suggesting North–South and East–West gradients in drought distribution. The Pacific El Nino Southern Oscillation (ENSO), the South Western Indian Ocean (SWIO) variability, and the quasi-biennial oscillation (QBO) are significant contributors to the observed spatio-temporal variability in drought. Both the ENSO and the SWIO modulate the North–South gradient in drought conditions over Peninsular Malaysia, while the QBO contributes more to the East–West gradient. Through modulating regional moisture fluxes, the warm phases of the ENSO and the SWIO, and the western phases of the QBO weaken the southwest and northeast monsoon, leading to precipitation deficits and droughts over Peninsular Malaysia. The East–West or North–South gradients in droughts are related to the middle mountains blocking southwest and northeast moisture fluxes towards Peninsular Malaysia. In addition, the ENSO and QBO variations are significantly leading to short-term droughts (less than a year), while the SWIO is significantly associated with longer-duration droughts (2 years or more). Overall, this work demonstrates how spatio-temporal drought patterns in tropical regions are related to monsoons and moisture transports affected by the oscillations over the Pacific and Indian oceans, which is important for national water risk management. 相似文献