Building climate change into risk assessments     

Alex Coletti  Antonio De Nicola  Maria Luisa Villani 《Natural Hazards》2016,84(2):1307-1325

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Confidence and Trust in Public Institution Natural Hazards Management: Case Studies in Urban and Rural China     

Alex Y. Lo  Lewis T. O. Cheung  Anna Ka-Yin Lee  Bixia Xu 《The Professional geographer》2016,68(3):475-484

This research aims to investigate the extent to which urban and rural residents trust grassroots-level institutions and how this might affect community resilience to environmental change in China. It focuses on the commitments of institutional actors and their capacities to manage natural hazards and coordinate the community's response. Semistructured interviews were conducted with megacity (Tianjin) and remote village (Wolong) residents in China. We found that public confidence in grassroots-level institutions is limited due to inherent constraints on resources and power. Residents of Wolong tend to recognize the commitment and role of those institutions in connecting individuals with one another, whereas their urban counterparts in Tianjin remain skeptical. Issues of solidarity might account for this difference. These findings will have implications for state–society cooperation and disaster risk comanagement in both urban and rural China.  相似文献   

An introduction to R for spatial analysis and mapping,by Chris Brunsdon and Lex Comber,London, Sage Publications Ltd., 2015, 360 pp., AU$92.00, NZ$94.78 (paperback), ISBN 9781446272954/AU$238.00, NZ$269.74 (hardback), ISBN 9781446272947     

Alex Singleton 《International journal of geographical information science》2016,30(4):821-822

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Coherent changes in wood charcoals,site occupation and lithic technology across the MIS 4/3 transition at Klein Kliphuis rock shelter,South Africa     

Alex Mackay  Caroline R. Cartwright 《第四纪科学杂志》2023,38(1):38-48

We explore the correspondence between changing palaeoenvironments, patterns of site use, and lithic technology at the rock shelter site Klein Kliphuis (South Africa) across the interval 65–55 000 years before present. This period coincides with the termination of Marine Isotope Stage (MIS) 4, and the disappearance of an iconic late Pleistocene archaeological unit known as the Howiesons Poort. Wood charcoals indicate sufficient soil moisture around Klein Kliphuis throughout the Howiesons Poort to support diverse tree species at a time when site occupation was relatively intense. At least some fuelwood-gathering in this period may have been undertaken to support heat treatment of silcrete, which was the dominant lithology in tool production. A coherent set of changes occurs across the MIS 4/3 transition: occupational intensity declines, tracked by declining diversity of fuelwood species, an increase in the proportion of charcoals from shrubs and small flowering plants, lower prevalence of silcrete, and less heat treatment. While declining soil moisture is implied, there appears to be a significant change in behaviour relating to site usage, whereby foraging for dense fuelwoods was replaced by the construction of ‘fast fires’ that may reflect briefer visits and increased forager mobility in early MIS 3.  相似文献   

Integrated cave drip monitoring for epikarst recharge estimation in a dry Mediterranean area,Sif Cave,Israel     

Nathan A. Sheffer  Moty Cohen  Efrat Morin  Tamir Grodek  Alex Gimburg  Einat Magal  Haim Gvirtzman  Manuela Nied  Daniel Isele  Amos Frumkin 《水文研究》2011,25(18):2837-2845

Understanding recharge mechanisms and controls in karst regions is extremely important for managing water resources because of the dynamic nature of the system. The objective of this study was to evaluate water percolation through epikarst by monitoring water flow into a cave and conducting artificial irrigation and tracer experiments, at Sif Cave in Wadi Sussi, Israel from 2005 through 2007. The research is based on continuous high‐resolution direct measurements of both rainfall and water percolation in the cave chamber collected by three large PVC sheets which integrate drips from three different areas (17, 46, and 52 m²). Barrels equipped with pressure transducers record drip rate and volume for each of the three areas. The combined measured rainfall and cave data enables estimation of recharge into the epikarst and to better understand the relationship of rainfall‐recharge. Three distinct types of flow regimes were identified: (1) ‘Quick flow’ through preferential flow paths (large fractures and conduits); (2) ‘Intermediate flow’ through a secondary crack system; and (3) ‘Slow flow’ through the matrix. A threshold of ～100 mm of rain at the beginning of the rainy season is required to increase soil water content allowing later rainfall events to percolate deeper through the soil and to initiate dripping in the cave. During winter, as the soil water content rises, the lag time between a rain event and cave drip response decreases. Annual recharge (140–160 mm in different areas in the cave) measured represents 30–35% of annual rainfall (460 mm). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A flexible nonlinear modelling framework for nonstationary generalized extreme value analysis in hydroclimatology     

Alex J. Cannon 《水文研究》2010,24(6):673-685

Parameters in a generalized extreme value (GEV) distribution are specified as a function of covariates using a conditional density network (CDN), which is a probabilistic extension of the multilayer perceptron neural network. If the covariate is time or is dependent on time, then the GEV‐CDN model can be used to perform nonlinear, nonstationary GEV analysis of hydrological or climatological time series. Owing to the flexibility of the neural network architecture, the model is capable of representing a wide range of nonstationary relationships. Model parameters are estimated by generalized maximum likelihood, an approach that is tailored to the estimation of GEV parameters from geophysical time series. Model complexity is identified using the Bayesian information criterion and the Akaike information criterion with small sample size correction. Monte Carlo simulations are used to validate GEV‐CDN performance on four simple synthetic problems. The model is then demonstrated on precipitation data from southern California, a series that exhibits nonstationarity due to interannual/interdecadal climatic variability. Copyright © 2009 Her Majesty the Queen in right of Canada. Published by John Wiley & Sons, Ltd.  相似文献   

The Proportional Effect   总被引：2，自引：1，他引：1  

J. G. Manchuk  O. Leuangthong  C. V. Deutsch 《Mathematical Geosciences》2009,41(7):799-816

Many regionalized variables encountered in geostatistical application show a proportional effect, that is, greater variability in high valued areas. The proportional effect is a consequence of the univariate distribution of the variable being considered. This presents several challenges including inference of variograms and conditional distributions. The correlogram and relative variogram were devised to mitigate challenges with variography. Other techniques such as normalization, direct simulation, and indicators provide a means to characterize conditional distributions. A review of these tools is given along with several examples to provide an explanation of the proportional effect.  相似文献   

Dating terrestrial impact events     

Alexander Deutsch  Urs Schrer 《Meteoritics & planetary science》1994,29(3):301-322

Abstract— Systematic examination of dating results from various craters indicates that about 90% of the rocks affected by an impact preserve their pre-shock ages because shock and post-shock conditions are not sufficient to disturb isotopic dating systems. In the other 10% of target lithologies, various geochronometers show significant shock-induced effects. Major problems in dating impactites are caused by their non-equlibrated character. They often display complex textures, where differently shocked and unshocked phases interfinger on the sub-mm scale. Due to this, dating on whole rock samples or insufficiently pure mineral fractions often yielded ambiguous results that set broad age limits but are not sufficient to answer reliably questions such as a possible periodicity in cratering on Earth, or correlation of impact events with mass extinctions. Dating results from shock recovery experiments indicate that post-shock annealing plays the most important role in resetting isotopic clocks. Therefore, the major criterion for sample selection in and around craters is the post-shock thermal regime. Based on their different thermal evolution, the following geological impact formations can be distinguished: (1) the coherent impact melt layer, (2) allochthonous breccia deposits, (3) the crater basement, and (4) distant ejecta deposits. Samples of the coherent impact melt layer are the most suitable candidates for dating. Excellent ages of high precision can be obtained by internal Rb-Sr, and Sm-Nd isochrons, U-Pb analyses on newly crystallized accessory minerals, and K-Ar (³⁹Ar-⁴⁰Ar) dating of clast-free melt rocks. Fission track counting on glassy material has yielded correct ages, and paleomagnetic measurements have been successfully applied to post-Triassic craters. In the ideal case of a fast-cooling impact melt layer, all these different techniques should give identical ages. Allochthonous breccias contain shocked, unshocked, and/or glassy components in various proportions; and, hence, each of these ejecta deposits has its own individual thermal history, making sample evaluation difficult Glassy melt particles in suevitic breccias are well suited for fission track and Ar-Ar dating. Weakly shocked material may yield reliable Ar-Ar and fission track ages, if formation temperatures were high, and cooling rates moderate. In contrast, highly shocked but rapidly cooled lithologies show only disturbed and not reset isotopic systems. For ejecta deposits and the crater wall of young craters, dating with cosmogenic nuclides is a new and powerful technique. Crater basement lithologies have a high potential in impact dating, although it has not been exploited so far. A prerequisite for resetting of isotopic clocks in these lithologies is the presence of an overlaying impact melt layer, which causes thermal metamorphism. Fission track and K-Ar techniques are most promising, because both systems are easily reset at low temperatures. Good candidates for impact dating are long-term annealed rocks, even if shock metamorphic overprint is very weak. In addition, Ar-Ar dating dating of pseudotachylites appears promising. In large impact structures, where high temperatures persist for long times, polymict “footwall” breccias beneath the melt sheet are also appropriate for dating, using the isochron approach and U-Pb on accessory minerals. Distant ejecta material have undergone very fast cooling, and the ejecta deposits have ambient formation temperatures. Among this material, tektites and impact melt glass are ideal objects for Ar-Ar and fission track impact dating. Dating on other material from distant ejecta deposits, such as U-Pb analyses on zircons, offers new possibilities. Efforts to correlate distant ejecta with distinct craters critically depend on proper error assignment to a specific age. This aspect is illustrated on the K/T boundary example.  相似文献   

Magmatic 87Sr/86Sr relicts in hydrothermally altered quartz diorites (Brabant Massif,Belgium) and the role of epidote as a Sr filter     

Luc André  Sarah Deutsch 《Contributions to Mineralogy and Petrology》1986,92(1):104-112

The porphyritic quartz diorites of the Caledonian Brabant Massif have been totally altered. Ca, Rb, Sr, Zr, Ce, Y measurements and Sr-Nd isotopic analyses were performed on the Quenast plug and the Lessines sill, in an attempt to study the relative mobility of Sr and evaluate the extent, direction and magnitude of the ⁸⁷Sr/⁸⁶Sr alterations. Sr electron microprobe analyses of epidote were also carried out to assess its role in the Sr distribution.The initial ⁸⁷Sr/⁸⁶Sr ratio is shown to have had an unsteady behaviour during the studied water/rock interactions since it has been sometimes enhanced, sometimes depressed and occasionally not modified. The possibility and magnitude of the ⁸⁷Sr contamination turn out to be strictly related to the degree of Sr accommodation in the secondary minerals. Epidote in particular has proved to be the main trap for the hydrothermal Sr and this mineral is thus regarded as the major controlling factor of ⁸⁷Sr hydrothermal contamination. The epidote-poor rocks (albite+chlorite-rich rocks) seem to have been unaffected by any Sr interchange with the aqueous solutions. Therefore, as alteration quickly follows the crystallization of the magma, their initial ⁸⁷Sr/ ⁸⁶Sr ratio, which is deduced from an isochron, might be a primary petrogenetic feature enabling interpretation of the genesis of their parental magmas. On the other hand, in the epidote-rich rocks, this ratio has been readily altered; it could thus generally be used only to trace the origin of the hydrothermal solutions. As a consequence, these rocks should not be selected for dating an alteration event by the Rb-Sr method.  相似文献   

Noble gas systematics of deep rift zone glasses from Loihi Seamount, Hawaii   总被引：3，自引：0，他引：3  

Peter J. Valbracht  Thomas Staudacher  Alex Malahoff  Claude J. Allgre 《Earth and Planetary Science Letters》1997,150(3-4):399-411

We report new noble gas fusion and crushing data for six pillow rim glasses, recovered between 3 and 5 km water depth on the south rift zone of Loihi Seamount, Hawaii. Helium abundances of the glasses vary from 0.3 to 2.3 μcc/g, with ⁴He/³He ratios between 30000 and 27000 (24–27 R_A), similar to previously reported values. The neon data form a correlation line which is similar to the Loihi-Kilauea line reported by Honda et al. [1], but extends to much higher ratios, up to 12.9 and 0.0382 for the ²⁰Ne/²²Ne and ²¹Ne/²²Ne ratios, respectively. This provides conclusive evidence for the suggestion that the Hawaiian plume, thought to originate in the lower mantle, has a solar-like ²⁰Ne/²²Ne composition [1], but a slightly higher ²¹Ne/²²Ne ratio. ⁴⁰Ar/³⁶Ar ratios of the deep rift-zone glasses are as high as 2600, and show a positive correlation with neon isotopic ratios. In contrast to neon and argon, all xenon isotopic compositions are isotopically indistinguishable from air, which either suggests preferential atmospheric contamination of xenon, or could indicate an atmospheric xenon isotopic composition for the lower mantle.  相似文献