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101.
Sandra G. Catane Hillel B. Cabria Cristituto P. Tomarong Jr Ricarido M. Saturay Jr Mark Albert H. Zarco Winston C. Pioquinto 《Landslides》2007,4(1):85-90
On 17 February 2006, a rockslide-debris avalanche cascaded down the steep slope of Mt. Can-abag, burying the entire village
of Guinsaugon in St. Bernard, Southern Leyte, Philippines. Casualties include 139 dead with 980 still missing and presumed
dead, making it perhaps the most catastrophic landslide in Philippine history. The landslide started at the ridge top along
a fault plane associated with the active Philippine Fault Zone. It started as a block slide that transformed into an avalanche.
The entire event lasted for only a few minutes. Estimated maximum landslide velocity is 120–130 m/s. The landslide left behind
a deep, wedge-shaped scarp. The central part of the deposit exhibits a hummocky topography typical of avalanches, in contrast
to the flatter surface of the debris-flow-type marginal deposit. High amounts of soil in the matrix were derived from the
scouring of ancient landslide deposits and rice fields in the valley. The landslide has a total area of 3.2 km2 and a runout distance of 4.1 km. Estimated volume of debris is approximately 20 Mm3. At least four streams were dammed by the landslide debris. Intense precipitation and earthquakes preceding the landslide
are the potential triggers. Preliminary back analyses assuming a planar and wedge slip surface yielded very low factors of
safety even under dry conditions. A more rigorous analysis of the failure mechanism of the landslide is needed. 相似文献
102.
Sandra J. Winterbottom 《Geomorphology》2000,34(3-4)
Channel planform change was analysed using a variety of data-sources for the medium-term (>25 years and <250 years) and short-term (<25 years) on a reach of the Rivers Tay and Tummel, Scotland. Map data were input into a Geographic Information System (GIS) and used to determine planform characteristics and changes in width, braiding index and sinuosity for the study reach between 1755 and 1976. Aerial photographs were utilised to determine the more recent changes that had taken place between 1971 and 1994. The analysis showed that significant changes had occurred over the medium term with a mean reduction in channel width of 34% for this period. These changes are comparable to those found in studies of similar European rivers for this period. Changes determined for the short-term displayed a continuance of this trend at a comparable rate of change. An analysis of flood frequency and magnitude, precipitation and discharge records for both periods does not show an associated decrease and therefore does not reflect the changes in channel planform. Evidence points towards flood embankment construction in the mid-1800s as the initial cause of channel change for the study reach which was later exacerbated by flow regulation. Incision and the subsequent stabilisation of lateral and mid-channel gravel bars by vegetation succession has resulted in an overall increase in the stability of the study reach which has persisted even where the embankments have fallen into disrepair. 相似文献
103.
Jo Moore Andreas Beinlich Jennifer K. Porter Cristina Talavera Jasper Berndt Sandra Piazolo Håkon Austrheim Andrew Putnis 《Journal of Metamorphic Geology》2020,38(1):103-127
As a common constituent of metamorphic assemblages, rutile provides constraints on the timing and conditions of rock transformation at high resolution. However, very little is known about the links between trace element mobility and rutile microstructures that result from synmetamorphic deformation. To address this issue, here we combine in situ LA-ICP-MS and sensitive high-resolution ion microprobe trace element data with electron back-scatter diffraction microstructural analyses to investigate the links between rutile lattice distortions and Zr and U–Pb systematics. Furthermore, we apply this integrated approach to constrain further the temperature and timing of amphibolite facies metamorphism and deformation in the Bergen Arcs of southwestern Norway. In outcrop, the formation of porphyroblastic rutile in dynamically hydrated leucocratic domains of otherwise rutile-poor statically hydrated amphibolite provides key contextual information on both the ambient conditions of hydration and deformation and the composition of the reactive fluid. Rutile in amphibolite recorded ambient metamorphic temperatures of ~590–730°C during static hydration of the granulitic precursor. By contrast, rutile from leucocratic domains in the directly adjacent shear zone indicates that deformation was accompanied by a localized increase in temperature. These higher temperatures are recorded in strain-free rutile (~600–860°C) and by Zr concentration measurements on low-angle boundaries and shear bands (620–820°C). In addition, we also observe slight depletions of Zr and U along rutile low-angle boundaries relative to strain-free areas in deformed grains from the shear zone. This indicates that crystal–plastic deformation facilitated the compositional re-equilibration of rutile upon cooling to slightly below the peak temperature of deformation. Cessation of deformation at mid-crustal conditions near ~600°C is recorded by late stage growth of small (<150 µm) rutile in the high-strain zones. U–Pb age data obtained from the strain-free and distorted rutile grains cluster in distinct populations of 437.4 ± 2.7 Ma and c. 405–410 Ma, respectively. These different ages are interpreted to reflect the difference in closure for thermally induced Pb diffusion between undeformed and deformed rutile during post-deformation exhumation and cooling. Thus, our results provide a reconstruction of the thermochronological history of the amphibolite facies rocks of the Lindås Nappe and highlight the importance of integration of microstructural data during application of thermometers and geochronometers. 相似文献
104.
Waldo Sven Lavado Casimiro David Labat Jean Loup Guyot Sandra Ardoin‐Bardin 《水文研究》2011,25(24):3721-3734
In this article, we propose an investigation of the modifications of the hydrological response of two Peruvian Amazonas–Andes basins in relationship with the modifications of the precipitation and evapotranspiration rates inferred by the IPCC. These two basins integrate around 10% of the total area of the Amazonian basin. These estimations are based on the application of two monthly hydrological models, GR2M and MWB3, and the climatic projections come from BCM2, CSMK3 and MIHR models for A1B and B1 emission scenarios (SCE A1B and SCE B1). Projections are approximated by two simple scenarios (anomalies and horizon) and annual rainfall rates, evapotranspiration rates and discharge were estimated for the 2020s (2008–2040), 2050s (2041–2070) and 2080s (2071–2099). Annual discharge shows increasing trend over Requena basin (Ucayali river), Puerto Inca basin (Pachitea river), Tambo basin (Tambo river) and Mejorada basin (Mantaro river) while discharge shows decreasing trend over the Chazuta basin (Huallaga river), the Maldonadillo basin (Urubamba river) and the Pisac basin (Vilcanota river). Monthly discharge at the outlet of Puerto Inca, Tambo and Mejorada basins shows increasing trends for all seasons. Trends to decrease are estimated in autumn discharge over the Requena basin and spring discharge over Pisac basin as well as summer and autumn discharges over both the Chazuta and the Maldonadillo basins. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
105.
Abstract– To better explain the unusual distribution and relative abundances of several 6‐ and 7‐carbon amino acids found in meteorites, their thermodynamic properties were studied using accurate ab initio techniques. In addition to optimized structures and relative energies, vibrational frequency and thermochemical analysis of different diastereomers were performed at temperatures relevant to conditions of synthesis of these amino acids in meteorites. The results of calculations were compared with the measured content of the amino acids in the Murchison meteorite. The distribution of several longer chain amino acids in meteorites seems to point to at least some thermodynamic control in their formation. For diastereomeric compounds, on the other hand, the comparison suggests that their synthetic conditions, or those of their precursors, were far from thermodynamic equilibrium. 相似文献
106.
An Evaluation of the Effects of Primary and Cross‐Contamination during the Preparation of Rock Powders for Chemical Determinations 下载免费PDF全文
José P. Sertek Sandra Andrade Horstpeter H. Ulbrich 《Geostandards and Geoanalytical Research》2015,39(3):381-397
Quartz crystals from the Batatal site, Minas Gerais, southern Brazil, were used to determine quantitatively primary contamination when submitting the samples to milling processes. Crushing devices used were a primary steel jaw crusher (br1), a secondary tungsten carbide (WC) crusher (br2) and a hydraulic press with stainless steel plates (pr). Fragments with suitable sizes were then ground in different Fritsch planetary mills, equipped with agate, WC and chromium‐steel rings for 7, 4 and 3 min, respectively. Solutions of the powders were analysed initially with the TotalQuant? method in a quadrupole ICP‐MS instrument, providing semi‐quantitative results for seventy‐five elements. Contamination from crushers and mills was visible in major and minor elements such as Fe, Mn and Ti, and noticeable in trace elements such as Cr, Co, Ni, Cu and also V, Zr, Sc; significant contamination was observed from W, Mo, Co, Ta and Nb (mainly by use of the WC devices). Little or no contamination was observed for Pb, REE, Sr and Rb, elements that are important in routine isotopic determinations. Cross‐contamination was tested by grinding either a granite or a basalt sample, followed by conventional cleaning with mica‐free quartz sand, before the working quartz powder was prepared. 相似文献
107.
Robustness of GNSS integer ambiguity resolution in the presence of atmospheric biases 总被引:3,自引:1,他引:2
Both the underlying model strength and biases are two crucial factors for successful integer GNSS ambiguity resolution (AR) in real applications. In some cases, the biases can be adequately parameterized and an unbiased model can be formulated. However, such parameterization will, as trade-off, reduce the model strength as compared to the model in which the biases are ignored. The AR performance with the biased model may therefore be better than with the unbiased model, if the biases are sufficiently small. This would allow for faster AR using the biased model, after which the unbiased model can be used to estimate the remaining unknown parameters. We assess the bias-affected AR performance in the presence of tropospheric and ionospheric biases and compare it with the unbiased case. As a result, the maximum allowable biases are identified for different situations where CORS, static and kinematic baseline models are considered with different model settings. Depending on the size of the maximum allowable bias, a user may decide to use the biased model for AR or to use the unbiased model both for AR and estimating the other unknown parameters. 相似文献
108.
109.
Ecosystem-based marine spatial management: Review of concepts, policies, tools, and critical issues 总被引:1,自引:0,他引:1
Stelios Katsanevakis Vanessa Stelzenmüller Andy South Thomas Kirk Sørensen Peter J.S. Jones Sandy Kerr Fabio Badalamenti Christos Anagnostou Patricia Breen Guillem Chust Giovanni D’Anna Mike Duijn Tatiana Filatova Fabio Fiorentino Helena Hulsman Kate Johnson Aristomenis P. Karageorgis Ingrid Kröncke Simone Mirto Carlo Pipitone Susan Portelli Wanfei Qiu Henning Reiss Dimitris Sakellariou Maria Salomidi Luc van Hoof Vassiliki Vassilopoulou Tomás Vega Fernández Sandra Vöge Anke Weber Argyro Zenetos Remment ter Hofstede 《Ocean & Coastal Management》2011,54(11):807-820
Conventional sectoral management and piecemeal governance are considered less and less appropriate in pursuit of sustainable development. Ecosystem based marine spatial management (EB-MSM) is an approach that recognizes the full array of interactions within an ecosystem, including human uses, rather than considering single issues, species, or ecosystem services in isolation. Marine spatial planning and ocean zoning are emerging concepts that can support EB-MSM. EB-MSM is driven by high-level goals that managers aim to achieve through the implementation of measures. High-level goals and objectives need to be translated into more operational objectives before specific targets, limits and measures can be elaborated.Monitoring, evaluation and adaptation are necessary to ensure that marine management measures are both effective and efficient. Solid monitoring frameworks are the foundation of adaptive management, as they provide the necessary information to evaluate performance and the effectiveness of management actions. Marine protected areas (MPAs) - possibly set up in networks - constitute a key component in EB-MSM policies and practises and have been applied as a cornerstone in conservation of marine biodiversity, management of fish populations, development of coastal tourism, etc. Moreover, MPA experiences have provided methods and concepts (such as zoning) to a wider EB-MSM context. The assignment of values to biophysical features of the marine environment allows the direct assessment of related management choices and may assist EB-MSM.A range of monetary valuation techniques have been proposed to reduce attributes of goods and services to a single metric. However, in the marine environment such an approach is often over simplistic, and thus less reductive techniques may be necessary. Rather than producing a single metric, the results of non-monetary assessments guide policy allowing weight to be given as necessary to potential areas of conflict and consensus.Strategies to take into account climate change effects and geohazard risks in EB-MSM have been applied or proposed worldwide. EB-MSM regimes must be alert to such risks and flexible to account for changes. 相似文献
110.
Arsenic in shallow groundwater of Bangladesh: investigations from three different physiographic settings 总被引:1,自引:0,他引:1
M. Aziz Hasan K. Matin Ahmed Ondra Sracek Prosun Bhattacharya Mattias von Brömssen Sandra Broms Johan Fogelström M. Lutful Mazumder Gunnar Jacks 《Hydrogeology Journal》2007,15(8):1507-1522
Occurrences of arsenic (As) in the Bengal Basin of Bangladesh show close relationships with depositional environments and sediment textures. Hydrochemical data from three sites with varying physiography and sedimentation history show marked variations in redox status and dissolved As concentrations. Arsenic concentration in groundwater of the Ganges Flood Plain (GFP) is characteristically low, where high Mn concentrations indicate redox buffering by reduction of Mn(IV)-oxyhydroxides. Low DOC, \( {\text{HCO}}^{ - }_{3} \), \( {\text{NH}}^{ + }_{4} \) and high \( {\text{NO}}^{ - }_{3} \) and \( {\text{SO}}^{{2 - }}_{4} \) concentrations reflect an elevated redox status in GFP aquifers. In contrast, As concentration in the Ganges Delta Plain (GDP) is very high along with high Fe and low Mn. In the Meghna Flood Plain (MFP), moderate to high As and Fe concentrations and low Mn are detected. Degradation of organic matter probably drives redox reactions in the aquifers, particularly in MFP and GDP, thereby mobilising dissolved As. Speciation calculations indicate supersaturation with respect to siderite and vivianite in the groundwater samples at MFP and GDP, but groundwater in the GFP wells is generally supersaturated with respect to rhodochrosite. Values of log PCO2 at MFP and GDP sites are generally higher than at the GFP site. This is consistent with Mn(IV)-redox buffering suggested at the GFP site compared to Fe(III)-redox buffering at MFP and GDP sites. 相似文献