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31.
The seismic damage of internal partitions may cause significant earthquake loss; this phenomenon is caused by (a) their tendency to exhibit damage for low demand levels and (b) the consequent loss of inventory and breakdown that their collapse can cause. Quasi‐static tests are performed on six 5‐m‐high plasterboard internal partitions, which represent typical partitions in industrial and commercial buildings in the European area. A steel test setup is designed to transfer the load, which is provided by the actuator, to the partition. The testing protocol provided by Federal Emergency Management Agency (FEMA) 461 is adopted for the quasi‐static tests. The typical failure mode of the specimens is the buckling of a steel stud, which involves the boards that are attached to the buckled stud. The buckling failure usually concentrates across the plasterboard horizontal joints. A frictional behavior is exhibited for low demand levels, whereas a pinched behavior is shown for moderate‐to‐high demand levels. The interstory drift ratios required to reach a given damage limit state are evaluated using a predefined damage scheme. Based on the experimental data, the fragility curves for three different damage states (DS1, DS2, and DS3) are estimated. The fragility curve yields median interstory drift ratio values of 0.28%, 0.81%, and 2.05% and logarithmic standard deviations of 0.39, 0.42, and 0.46 for DS1, DS2, and DS3, respectively. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Hydrological processes in mountain headwater basins are changing as climate and vegetation change. Interactions between hydrological processes and subalpine forest ecological function are important to mountain water supplies due to their control on evapotranspiration (ET). Improved understanding of the sensitivity of these interactions to seasonal and interannual changes in snowmelt and summer rainfall is needed as these interactions can impact forest growth, succession, health, and susceptibility to wildfire. To better understand this sensitivity, this research examined ET for a sub-alpine forest in the Canadian Rockies over two contrasting growing seasons and quantified the contribution of transpiration (T) from the younger tree population to overall stand ET. The younger population was focused on to permit examination of trees that have grown under the effect of recent climate change and will contribute to treeline migration, and subalpine forest densification and succession. Research sites were located at Fortress Mountain Research Basin, Kananaskis, Alberta, where the subalpine forest examined is composed of Abies lasiocarpa (Subalpine fir) and Picea engelmannii (Engelmann spruce). Seasonal changes in water availability from snowmelt, precipitation, soil moisture reserves yielded stark differences in T and ET between 2016 and 2017. ET was higher in the drier year (2017), which had late snowmelt and lower summer rainfall than in the wetter year (2016) that had lower snowmelt and a rainy summer, highlighting the importance of spring snowmelt recharge of soil moisture. However, stand T of the younger trees (73% of forest population) was greater (64 mm) in 2016 (275 mm summer rainfall) than 2017 (39 mm T, 147 mm summer rainfall), and appears to be sensitive to soil moisture decreases in fall, which are largely a function of summer period rainfall. Relationships between subalpine forest water use and different growing season and antecedent (snowmelt period) hydrological conditions clarify the interactions between forest water use and alpine hydrology, which can lead to better anticipation of the hydrological response of subalpine forest-dominated basins to climate variability and change. 相似文献
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Seasonal ground ice impacts on spring ecohydrological conditions in a western boreal plains peatland
Brandon Van Huizen Richard M. Petrone Jonathan S. Price William L. Quinton John W. Pomeroy 《水文研究》2020,34(3):765-779
Peatlands in the Western Boreal Plains act as important water sources in the landscape. Their persistence, despite potential evapotranspiration (PET) often exceeding annual precipitation, is attributed to various water storage mechanisms. One storage element that has been understudied is seasonal ground ice (SGI). This study characterized spring SGI conditions and explored its impacts on available energy, actual evapotranspiration, water table, and near surface soil moisture in a western boreal plains peatland. The majority of SGI melt took place over May 2017. Microtopography had limited impact on melt rates due to wet conditions. SGI melt released 139mm in ice water equivalent (IWE) within the top 30cm of the peat, and weak significant relationships with water table and surface moisture suggest that SGI could be important for maintaining vegetation transpiration during dry springs. Melting SGI decreased available energy causing small reductions in PET (<10mm over the melt period) and appeared to reduce actual evapotranspiration variability but not mean rates, likely due to slow melt rates. This suggests that melting SGI supplies water, allowing evapotranspiration to occur at near potential rates, but reduces the overall rate at which evapotranspiration could occur (PET). The role of SGI may help peatlands in headwater catchments act as a conveyor of water to downstream landscapes during the spring while acting as a supply of water for the peatland. Future work should investigate SGI influences on evapotranspiration under differing peatland types, wet and dry spring conditions, and if the spatial variability of SGI melt leads to spatial variability in evapotranspiration. 相似文献
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Katsuichiro?GodaEmail author Crescenzo?Petrone Raffaele?De?Risi Tiziana?Rossetto 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(9):2337-2355
This study conducts coupled simulation of strong motion and tsunami using stochastically generated earthquake source models. It is focused upon the 2011 Tohoku, Japan earthquake. The ground motion time-histories are simulated using the multiple-event stochastic finite-fault method, which takes into account multiple local rupture processes in strong motion generation areas. For tsunami simulation, multiple realizations of wave profiles are generated by evaluating nonlinear shallow water equations with run-up. Key objectives of this research are: (i) to investigate the sensitivity of strong motion and tsunami hazard parameters to asperities and strong motion generation areas, and (ii) to quantify the spatial variability and dependency of strong motion and tsunami predictions due to common earthquake sources. The investigations provide valuable insights in understanding the temporal and spatial impact of cascading earthquake hazards. Importantly, the study also develops an integrated strong motion and tsunami simulator, which is capable of capturing earthquake source uncertainty. Such an advanced numerical tool is necessary for assessing the performance of buildings and infrastructure that are subjected to cascading earthquake–tsunami hazards. 相似文献
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Seasonal dynamics in shallow freshwater pond‐peatland hydrochemical interactions in a subarctic permafrost environment 
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下载免费PDF全文 Terrestrial and aquatic ecological productivity are often nutrient limited in subarctic permafrost environments. High latitude regions are experiencing significant climatic change, including rapid warming and changing precipitation patterns, which may result in changes in nutrient dynamics within terrestrial and aquatic systems and hydrochemical transport between them. The objective of this research was to characterize changes in runoff quantity and quality within, and between peatlands and ponds throughout the snow‐free summer season. Two ponds and their catchments were monitored over the snow‐free season to measure changes in hydrologic storage, and to determine how water chemistry changed with the evolution of the frost table depth. Thresholds in hydrologic storage combined with frost table position (which inhibited infiltration and storage) produced nonlinear responses for runoff generation through highly conductive shallow peat layers while deeper, less conductive layers retarded flow. Greater inputs were required to exceed hydrologic storage (fill and spill) as a deepening frost table increased the hydrologically active portion of the soil, leading to seasonal variability in runoff pathways between peatlands and ponds. Runoff contributions to ponds were an integral component of the snow‐free water balance during the study period, contributing up to 60% of all snow‐free inputs. Groundwater chemistry (and pond chemistry following runoff events when ponds were connected with peatlands) reflected the different depths of peat and mineral soil accessed throughout the season. This work has improved scientific understanding of the combined controls of hydrologic inputs and ground frost on runoff and nutrient transport between peatlands and ponds, and sheds insight into how nutrient dynamics in cold regions may evolve under a changing climate. 相似文献
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Subalpine forests are hydrologically important to the function and health of mountain basins. Identifying the specific water sources and the proportions used by subalpine forests is necessary to understand potential impacts to these forests under a changing climate. The recent “Two Water Worlds” hypothesis suggests that trees can favour tightly bound soil water instead of readily available free-flowing soil water. Little is known about the specific sources of water used by subalpine trees Abies lasiocarpa (Subalpine fir) and Picea engelmannii (Engelmann spruce) in the Canadian Rocky Mountains. In this study, stable water isotope (δ18O and δ2H) samples were obtained from S. fir and Engelmann spruce trees at three points of the growing season in combination with water sources available at time of sampling (snow, vadose zone water, saturated zone water, precipitation). Using the Bayesian Mixing Model, MixSIAR, relative source water proportions were calculated. In the drought summer examined, there was a net loss of water via evapotranspiration from the system. Results highlighted the importance of tightly vadose zone, or bound soil water, to subalpine forests, providing insights of future health under sustained years of drought and net loss in summer growing seasons. This work builds upon concepts from the “Two Water Worlds” hypothesis, showing that subalpine trees can draw from different water sources depending on season and availability. In our case, water use was largely driven by a tension gradient within the soil allowing trees to utilize vadose zone water and saturated zone water at differing points of the growing season. 相似文献
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Antonio Santo Giuseppe Di Crescenzo Giovanni Forte Raffaele Papa Marianna Pirone Gianfranco Urciuoli 《Landslides》2018,15(1):63-82
In the last 20 years, major efforts have been made to investigate shallow flow-type landslides. Such phenomena are usually rainfall-induced and in the geological context of Campania (Southern Italy) occur in pyroclastic soils resting on steep slopes mainly constituted by carbonate or volcanic bedrock and by flysch deposits. They are generally complex landslides with an early soil slide and a subsequent flow evolution. In this paper, a database of flowslides occurring in recent years within the flysch deposits of Avellino (Campanian Apennines) is first discussed and then the case study of Bosco de’ Preti landslide on March 4, 2005, is described. The geological and geotechnical characteristics of the soils involved are described and the monitoring of the groundwater heads collected over 1 year from June 2005 to June 2006 is also shown. The last part of the paper illustrates the results of numerical modelling of the landslide triggering to gain insights into such phenomena. Slope stability analyses are preceded by hydrological modelling of the slope based on the monitoring data. Numerical analysis demonstrated that the rainfall during the 2 months preceding the event was able to fully saturate the pyroclastic cover and to establish positive pore water pressure at the depth of the surface of rupture, a soil condition never witnessed in carbonatic contexts. Hence, a combination of antecedent (predisposing factors) and single rainfall events (triggering factors) led to slope failure, as usually happens in pyroclastic soils in carbonatic and volcanic contexts. Finally, analysis of the historical landslides together with detailed investigation of the Bosco de’ Preti case study permitted comparison between flow-type landslides in pyroclastic soils on carbonatic/volcanic bedrock and those on flysch. 相似文献
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Chiara M. Petrone 《Lithos》2010,119(3-4):585-606
A large Quaternary monogenetic volcanic field is present in the western part of the Trans-Mexican Volcanic Belt. It is composed by mafic-intermediate scoria cones and silicic domes that are arranged in two NNW–SSE alignments. These mark the north and south borders (Northern Volcanic Chain and Southern Volcanic Chain, SVC) of the San Pedro–Ceboruco graben. The products of this monogenetic volcanic field span a large range of compositions (from basalt to rhyolite) and magma affinities (from sub-alkaline to Na-alkaline), defining different magmatic groups. Mafic and silicic monogenetic centres from the north alignment also coexist with two stratovolcanoes (Ceboruco and Tepetiltic) and sometimes punctuate their flanks.Whole-rock analyses indicate the existence of 4 different types of primitive magmas (Na-alkaline, High-Ti, Low-Ti/SVC and sub-alkaline) which have evolved independently by low-P magmatic processes. Despite the relatively small size and simplicity of the monogenetic magmatism, open-system processes have modified the geochemical and isotope composition of erupted products. The negative correlation between Sr isotope ratios and MgO contents observed for Southern Volcanic Chain and High-Ti groups points to crustal interaction via AFC processes, involving upper granitic crust and mafic lower crust respectively. In contrast, the large variability in Nd-isotopic ratios, combined with low and less variable 87Sr/86Sr, shown by the most mafic compositions of the High-Ti group is mostly due to mantle source heterogeneities. Low-Ti and Na-alkaline compositions are only slightly modified by crustal contamination processes and their whole-rock geochemistry reflects the complex nature of the western Mexico sub-arc mantle. It is therefore apparent that a combination of mantle source processes plus crustal assimilation has generated complex geochemical and isotopic characteristics in the western part of the Trans-Mexican Volcanic belt.Despite the presence of monogenetic cones on the flanks of stratovolcanoes, limited magma interaction between monogenetic and polygenetic magmatism has been recognised only at Ceboruco, possibly producing the chemical variability of post-caldera lavas. Indeed, mafic magma feeding High-Ti monogenetic systems might represent the possible mafic end-member which triggered the Ceboruco caldera-forming event. This may have important implications for other explosive systems in which monogenetic magmatism is associated with stratovolcanoes.A geographic/tectonic control is also suggested by the geochemical data. Na-alkaline compositions are only found in the northern part of the Northern Volcanic Chain. Parental magmas of both the High-Ti and Low-Ti monogenetic series, erupted between the Ceboruco and Tepetiltic stratovolcanoes, were modified by lower crust AFC processes possibly favoured by the stress regime. Indeed, the presence of a local left-hand step over along the northern main fault systems between the two stratovolcanoes might inhibit free uprising of monogenetic mafic magmas. The preferential alignment of stratovolcanoes and monogenetic volcanic vents parallel to the northern main fault systems and the possible mixing between High-Ti mafic monogenetic magmas and more evolved Ceboruco magmas suggests that, under the predominance of regional stress, the influence of central volcanic vents on monogenetic magmatism might be more complex than simple control of vent directions and might favours magma mixing processes. 相似文献
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The relative contributions to total actual evapotranspiration (AET) from pond and riparian areas in a pond‐wetland complex in the Western Boreal Plain (WBP) of northern Alberta are measured using the Bowen ratio energy balance technique. Measurements show that a pond typical of the WBP evaporates at a rate more than twice that of the adjacent riparian peatland. Relating the actual to potential evapotranspiration over both surfaces yields Priestley–Taylor α coefficients of 0·69 and 1·11 for the peatland and pond respectively. Further results demonstrate that the sheltering and turbulent influences of the adjacent forested areas must be considered in the processes governing the permanence of WBP ponds. That is, forestry practices may inadvertently enhance the evaporative losses from the ponds, over and above the controls exerted by the regional climate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献