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排序方式: 共有110条查询结果,搜索用时 46 毫秒
1.
Rainfall thresholds for the triggering of landslides considering previous soil moisture conditions (Asturias,NW Spain) 总被引:1,自引:0,他引:1
Pablo Valenzuela María José Domínguez-Cuesta Manuel Antonio Mora García Montserrat Jiménez-Sánchez 《Landslides》2018,15(2):273-282
Given its geological and climatic conditions and its rugged orography, Asturias is one of the most landslide prone areas in the North of Spain. Most of the landslides occur during intense rainfall episodes. Thus, precipitation is considered the main triggering factor in the study area, reaching average annual values of 960 mm. Two main precipitation patterns are frequent: (i) long-lasting periods of moderate rainfall during autumn and winter and (ii) heavy short rainfall episodes during spring and early summer. In the present work, soil moisture conditions in the locations of 84 landslides are analysed during two rainfall episodes, which represent the most common precipitation patterns: October–November 2008 and June 2010. Empirical data allowed the definition of available water capacity percentages of 99–100% as critical soil moisture conditions for the landslide triggering. Intensity-duration rainfall thresholds were calculated for each episode, considering the periods with sustained high soil moisture levels before the occurrence of each analysed landslide event. For this purpose, data from daily water balance models and weather stations were used. An inverse relationship between the duration of the precipitation and its intensity, consistent with published intensity-duration thresholds, was observed, showing relevant seasonal differences. 相似文献
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Romero Jorge E. Vergara-Pinto Francisca Aguilar Germn Garcs Alex Montserrat Santiago 《Landslides》2022,19(4):865-883
Landslides - An extreme precipitation event produced catastrophic debris flows in central Chile during 29–31 January 2021 (austral summer). Our study focuses on the triggering factors and... 相似文献
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Factors influencing the distribution of coastal lichens Hydropunctaria maura and Wahlenbergiella mucosa 下载免费PDF全文
Responses to abiotic and biotic stresses that potentially drive the vertical zonation of the intertidal lichens Hydropunctaria maura, an upper littoral lichen, and Wahlenbergiella mucosa, a lower littoral lichen, were investigated in field and laboratory experiments. When transplanted, both lichens exhibited an inability to survive outside their normal vertical distribution range. W. mucosa appeared to be unable to tolerate prolonged periods of desiccation following translocation from lower to upper littoral regions, whereas H. maura was unable to survive in lower littoral zones possibly owing to increased grazing pressure. The effect of desiccation in both lichens was compared using pulse amplitude modulated chlorophyll fluorescence and infra‐red gas analysis; results indicated a more hydration‐dependent nature of W. mucosa. Photosynthetic (algal) pigments and phenolic compounds were determined in both lichen thalli, and a range of additional coastal lichens occupying a natural gradient from upper to lower shore levels. Pigment composition and concentration in both lichen thalli were similar whereas levels of phenolic compounds were up to three times higher in W. mucosa than H. maura. Pigment and phenolic concentration and composition exhibited some seasonality across 13 different lichens originating from different shore levels. Phenolic concentration increased towards the lower shore, suggesting a potential anti‐herbivory function. This marks the first study of pigments and phenolics in coastal lichen communities, and prompts further investigations on the particular physiological features of marine and maritime lichens that enable them to thrive in this extreme environment. 相似文献
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Ana Moreno Blas L. Valero‐Garcés Montserrat Jiménez‐Sánchez María José Domínguez‐Cuesta M. Pilar Mata Ana Navas Penélope González‐Sampériz Heather Stoll Pedro Farias Mario Morellón J. Pablo Corella Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091
A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Andrés Gutiérrez-Rodríguez Mikel Latasa Marta Estrada Montserrat Vidal Celia Marrasé 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):486-500
The carbon flux through major phytoplankton groups, defined by their pigment markers, was estimated in two contrasting conditions of the Northwestern Mediterranean open ocean ecosystem: the spring bloom and post-bloom situations (hereafter Bloom and Post-bloom, respectively). During Bloom, surface chlorophyll a (Chl a) concentration was higher and dominated by diatoms (53% of Chl a), while during Post-bloom Synechococcus (42%) and Prymnesiophyceae (29%) became dominant. The seawater dilution technique, coupled to high pressure liquid chromatography (HPLC) analysis of pigments and flow cytometry (FCM), was used to estimate growth and grazing rates of major phytoplankton groups in surface waters. Estimated growth rates were corrected for photoacclimation based on FCM-detected changes in red fluorescence per cell. Given the 30% average decrease in the pigment content per cell between the beginning and the end of the incubations, overlooking photoacclimation would have resulted in a 0.40 d?1 underestimation of phytoplankton growth rates. Corrected average growth rates (μo) were 0.90±0.20 (SD) and 0.40±0.14 d?1 for Bloom and Post-bloom phytoplankton, respectively. Diatoms, Cryptophyceae and Synechococcus were identified as fast-growing groups and Prymnesiophyceae and Prasinophyceae as slow-growing groups across Bloom and Post-bloom conditions. The higher growth rate during Bloom was due to dominance of phytoplankton groups with higher growth rates than those dominating in Post-bloom. Average grazing rates (m) were 0.58±0.20 d?1 (SD) and 0.31±0.07 d?1. The proportion of phytoplankton growth consumed by microzooplankton grazing (m/μo) tended to be lower in Bloom (0.69±0.34) than in Post-bloom (0.80±0.08). The intensity of nutrient limitation experienced by phytoplankton indicated by μo/μn (where μn is the nutrient-amended growth rate), was similar during Bloom (0.78) and Post-bloom (0.73). Primary production from surface water (PP) was estimated with 14C incubations. A combination of PP and Chl a synthesis rate yielded C/Chl a ratios of 34±21 and 168±75 (g:g) for Bloom and Post-bloom, respectively. Transformation of group-specific Chl a fluxes into carbon equivalents confirmed the dominant role of diatoms during Bloom and Synechococcus and Prymnesiophyceae during Post-bloom. 相似文献
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Active galactic nuclei and galaxy interactions 总被引:1,自引:0,他引:1
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Rheological control on the tectonic evolution of a continental suture zone: the Variscan example from NW Iberia (Spain) 总被引:1,自引:1,他引:0
Rubén Díez Fernández David A. Foster Juan Gómez Barreiro Montserrat Alonso-García 《International Journal of Earth Sciences》2013,102(5):1305-1319
The Variscan continental suture zone exposed in NW Iberia is examined to uncover the long-lived rheological control exerted by the strata deposited over the external parts of Gondwana on its geodynamic evolution. The suture occurs within a set of allochthonous terranes whose limits were taken as domain boundaries to interpret the Variscan stacking of Paleozoic continental domains and retrodeform the resulting nappe pile. The suture zone formed due to closure of ocean basins located between Gondwana and Laurussia during the Late Paleozoic and consists of relics of oceanic and transitional crust. The suture zone exhibits a tabular to lens shape due to repeated tectonic events dominated by non-coaxial deformation (thrusts and low-angle normal faults). Thrusting and normal faulting also involved the margins of the continents bounding the suture. The structure of the continental blocks, however, is dominated by folds, particularly large nappe folds with pronounced superimposed flattening. The upper part of the basal allochthonous units comprises a rheologically incompetent domain below the suture zone. This domain is typified by the carbonaceous-rich strata, which are probably Ordovician–Silurian sediments based on U–Pb detrital zircon populations. The rheology of this layer determined the location of the first accretionary thrust that initiated the Late Devonian subduction of the Gondwana margin below the suture zone. By favoring fault development, the upper sequence of the basal allochthonous units as a whole influenced the exhumation of deep-seated continental crust, the transference of the suture zone over Gondwana, and the re-equilibration of the resulting overthickened crust. 相似文献