The role of the 1999 Chamoli earthquake in the formation of ground cracks     

Irene Sarkar 《Journal of Asian Earth Sciences》2004,22(5):529

The moderate magnitude Chamoli earthquake that occurred in the Garhwal Higher Himalaya, in the early hours of March 29, 1999, caused intense damage to the ground and mountain slopes of the Alaknanda–Mandakini river valley and adjoining region. A systematic survey of this induced damage was conducted immediately after the earthquake occurred. Prominent shallow cracks of significant length, negligible width and indeterminate vertical extent, conspicuously tensile in nature, with little or no slip across the crack planes, were observed in the ground at several places along the surveyed route. These cracks had formed in the dynamic phase of the Chamoli earthquake process that is in the period of time during which the earthquake-generated seismic waves were passing through the geographic region of interest. However, we use the theory of earthquake-induced static (or long time) stress changes to visualize such cracks at some selected sites where ground damage was relatively more intense and varied to suggest lower bound estimates of the dynamic stress contributions of the main shock for their formation.Based on the results of our analysis we conclude that, just prior to the earthquake occurrence, under the influence of the local ambient stress field, the ground at these sites was already near failure in tension. To this, in its dynamic phase, the Chamoli earthquake induced stress perturbations, having, across the planes of the cracks, (i) shear components which were nearly equal and opposite to similar components of the ambient stress field and (ii) normal (tensile) components, necessary for triggering tensile failure of the ground. The σ₃ (or minimum principal stress) component of the resultant perturbed failure stress field thus became sufficiently tensile while the transverse stresses became sufficiently insignificant. This facilitated formation of major tensile cracks in the ground there. Our static estimates of the tensile stress changes at the different sites are, in essence, estimates of the minimal triggering stress perturbations that was provided by the Chamoli earthquake in the dynamic state for the formation of the tensile cracks there.  相似文献   

Magnetic fabrics and rock magnetism of Proterozoic dike swarm from the southern São Francisco Craton, Minas Gerais State, Brazil     

Maria Irene Bartolomeu Raposo  Alexandre O. Chaves  Paulo Lojkasek-Lima  Manoel Souza D'Agrella-Filho  Wilson Teixeira   《Tectonophysics》2004,378(1-2):43-63

Magnetic fabric and rock magnetism studies were performed on 32 mafic dikes of a Proterozoic dike swarm from the southern São Francisco Craton (SFC; Minas Gerais State, SE Brazil). Magnetic anisotropies were determined by applying anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of remanent magnetization (ARM). The latter was performed imposing both anhysteretic (total (AAR) and partial pAAR)) and isothermal remanence magnetizations (AIRM). Partial anhysteretic remanence anisotropy was performed based on remanent coercivity spectra from a pilot specimen of each site. In most sites, AMS is dominantly carried by ferromagnetic minerals, however, in some sites, the paramagnetic contribution exceeds 70% of bulk susceptibility. Rock magnetism and thin section analysis allow classifying the dikes as non-hydrothermalized and hydrothermalized. Magnetic measurement shows that the mean magnetic susceptibility is usually lower than 5×10⁻³ (SI). Ti-poor titanomagnetites up to pure magnetite pseudo-single-domain (PSD) grain sizes carry the majority of magnetic fabrics for non-hydrothermalized dikes whereas coarse to fine grained Ti-poor titanomagnetites carry the majority of magnetic fabrics for hydrothermalized dikes.Three primary AMS fabrics are recognized which are coaxial with ARM fabric, except for two dikes, from both non-hydrothermalized and hydrothermalized dikes. Normal AMS fabric surprisingly is not dominant (31%). The parallelism between AMS, pAAR_0–30, pAAR_30–60 and pAAR_60–90 fabrics in the hydrothermalized dikes indicates that magnetic grains formed due to late-stage crystallization or to remobilization of iron oxides due to hydrothermal alteration after dike emplacement have acquired a mimetic fabric coaxial with the primary fabric given by coarse-grained early crystallized Ti-poor titanomagnetites. This fabric is interpreted as magma flow in which the analysis of K_max inclination permitted the inference that the dikes were fed by horizontal or subhorizontal fluxes (K_max<30°). Intermediate AMS fabric is the most important (41%) in the investigated swarm. It is interpreted as due to vertical compaction of a static magma column with the minimum stress along the dike strike. ARM determinations for these sites also remained intermediate except for two dikes. In one of them, AIRM fabric resulted in normal AMS fabric while for the other AAR fabric resulted in inverse AMS fabric. A combination of AMS and ARM fabrics suggest that magmatic fabric for both dikes were overprinted by some late local event, probably related to Brasiliano orogenic processes after dike emplacement. InverseInverse AMS fabric is a minority (four dikes). ARM determinations also remained inverse suggesting a primary origin for inverse AMS fabric.  相似文献   

Microbial dechlorination of HCB,PCP, PCB180, HCH and PCE in a Yangtze Three Gorges Reservoir enrichment culture,China     

Irene Kranzioch-Seipel  Ulrike Beckert  Chaofeng Shen  Daqiang Yin  Andreas Tiehm 《Environmental Earth Sciences》2016,75(10):928

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Assessment of the acid drainage neutralization capacity and the toxic metals lixiviation of tailing from Guanajuato mining district,Mexico   总被引：1，自引：0，他引：1  

María Elena García-Arreola  Luisa María Flores-Vélez  Marcos Loredo-Tovías  Alfredo Aguillón-Robles  Rubén Alfonso López-Doncel  Irene Cano-Rodríguez  Sonia Hortensia Soriano-Pérez 《Environmental Earth Sciences》2018,77(9):355

In Mexico, many environmental problems are generated by large mining activities taking place in several mining districts. These mining activities produce great quantities of residues; large majorities of these have high sulfur content, which could generate acid drainage due to their interaction with the oxygen in the environment. The study area was located in the Mining District of Guanajuato, Mexico with abandoned tailings generated mainly by the gold and silver production. Two areas, called as Monte de San Nicolás (SN) and Peregrina (P) were selected for this study. The results study shows that there was no risk of production of acid drainage, since these tailings contained high amount of carbonates, which neutralized the generation of acidity and consequently decreased the possibility of leaching of some elements. However, not all elements leach in acid pH, as arsenic bound to oxyhydroxides, which is in a basic environment and its increased release by increasing the pH.  相似文献   

Social capital,individual responses to heat waves and climate change adaptation: An empirical study of two UK cities     

Johanna Wolf  W. Neil Adger  Irene Lorenzoni  Vanessa Abrahamson  Rosalind Raine 《Global Environmental Change》2010,20(1):44-52

It has been claimed that high social capital contributes to both positive public health outcomes and to climate change adaptation. Strong social networks have been said to support individuals and collective initiatives of adaptation and enhance resilience. As a result, there is an expectation that social capital could reduce vulnerability to risks from the impacts of climate change in the health sector. This paper examines evidence on the role social networks play in individuals’ responses to heat wave risk in a case study in the UK. Based on interviews with independently living elderly people and their primary social contacts in London and Norwich, we suggest that strong bonding networks could potentially exacerbate rather than reduce the vulnerability of elderly people to the effects of heat waves. Most respondents interviewed did not feel that heat waves posed a significant risk to them personally, and most said that they would be able to cope with hot weather. Bonding networks could perpetuate rather than challenge these narratives and therefore contribute to vulnerability rather than ameliorating it. These results suggest a complex rather than uniformly positive relationship between social capital, health and adaptation to climate change.  相似文献   

Bacterial contribution to sedimentary organic matter; a comparative study of lipid moieties in bacteria and Recent sediments     

H. Goossens  W. Irene  C. Rijpstra  R.R. Düren  J.W. De Leeuw  P.A. Schenck 《Organic Geochemistry》1986,10(4-6)

A systematic study of the lipid composition of thirteen bacterial species and three Recent sediments (methanogenic sediment, cyanobacterial mat and evaporative gypsum crust) was undertaken in an attempt to recognize bacterial organic matter in sediments. A sequential method, which distinguishes between three different modes of occurrence of lipid moieties (free, OH⁻- and H⁺-labile), was applied. The acid-labile fractions are discussed.The three main groups of bacteria, archaebacteria, gram-positive eubacteria and gram-negative eubacteria, are easily distinguished. Methanogenic and extremely halophilic archaebacteria are characterized by the presence of diphytanyl glyceryl ether and the absence of fatty acids. The gram-positive eubacteria contain primarily iso- and anteiso-branched fatty acids whereas the gram-negative bacteria and sediments are dominated by β- and α-hydroxy fatty acids. A wide variety of H⁺-labile hydroxy fatty acids was observed which included several, as yet unknown, structures.β-Hydroxy fatty acids in this H⁺-labile mode of occurrence are exclusively present in bacteria. Their distribution patterns in sediments are considered “fingerprints” of past and present bacterial populations. The specific differences in β -hydroxy fatty acid compositions observed in the different bacteria and the three sediments investigated, suggest that amide-linked β-hydroxy fatty acid patterns are useful as markers of bacterial populations and therefore of environmental conditions.  相似文献   

Modelling the variability of midlatitude storm activity on decadal to century time scales   总被引：1，自引：0，他引：1  

Irene Fischer-Bruns  H. von Storch  J. F. González-Rouco  E. Zorita 《Climate Dynamics》2005,25(5):461-476

The output of several multi-century simulations with a coupled ocean–atmosphere general circulation model is examined with respect to the variability of global storm activity in winter on time scales of decades and longer. The frequency of maximum wind speed events within a grid box, using the lower limits on the Beaufort wind speed scale of 8 and 10 Bft as thresholds, is taken as the characteristic parameter. Two historical climate runs with time-dependent forcing of the last five centuries, one control simulation, and three climate change experiments are considered. The storm frequency shows no trend until recently. Global maps for the industrially influenced period hardly differ from pre-industrial maps, even though significant temperature anomalies temporarily emerge in the historical runs. Two indicators describing the frequency and the regional shift of storm activity are determined. In historical times they are decoupled from temperature. Variations in solar and volcanic forcing in the historical simulations as well as in greenhouse gas concentrations for the industrially influenced period are not related to variations in storm activity. Also, anomalous temperature regimes like the Late Maunder Minimum are not associated with systematic storm conditions. In the climate change experiments, a poleward shift of storm activity is found in all three storm track regions. Over the North Atlantic and Southern Ocean, storm activity increases, while it decreases over the Pacific Ocean. In contrast to the historical runs, and with the exception of the North Pacific storm frequency index, the storm indices parallel the development of temperature, exceeding the 2 σ-range of pre-industrial variations in the early twenty-first century.  相似文献   

Investigation of waste disposal areas using electrical methods: a case study from Chania,Crete, Greece   总被引：1，自引：0，他引：1  

Pantelis Soupios  Ilias Papadopoulos  Maria Kouli  Irene Georgaki  Filippos Vallianatos  Eleni Kokkinou 《Environmental Geology》2007,51(7):1249-1261

A geophysical investigation of a landfill area was conducted as inextricable phase of a preliminary geotechnical, geological and hydrogeological study of the area under investigation. Electrical resistivity tomography (ERT), one of the most promising prospecting techniques mainly concerning its effective contribution to resolve several environmental problems, was applied for the geophysical modeling. ERT is a robust imaging method the theory and implementation of which are well documented in geophysical research literature. The survey site is located in Akrotirion Peninsula, about 7 km east of Chania city in Crete I. The geological setting comprises Trypalion limestones, marly limestones and a clayed weathered layer. Cavities are also identified at various scales which are recent tectono-karstic voids. Due to the above-mentioned geological singularity and in the light of the requirement for an environmentally safe construction of the landfill, an ERT survey was carried out. Specifically, seven geoelectrical tomographies were conducted reaching the prospecting depth of 36 m. The resulted images conduced, to overcome geotechnical problems since the spatial distribution of karstic voids was determined, to plan the future sites for waste disposal as the geological conditions were studied in detail and to reliably estimate the thickness of the already deposited wastes. The resulted images were confirmed using available borehole logs and ambient noise measurements.  相似文献   

The figure of the earth — Changes in concepts     

Irene Fischer 《Surveys in Geophysics》1975,2(1):3-54

The search for the Figure of the Earth is rooted in the age-old wonder about the world we live in. The ancient mythical notions have developed, under the tutelage of Greek systematic thought, into specific questions of the shape and size of the Earth. The history of these questions, now spanning more than two millenia, shows a continuous refinement in formulation, as each bona fide answer prompted refined measurements which, in turn, started a new round of problems. The change in concept of what one was looking for was, and still is, closely connected with the technical capability and its potential for further development. This change in concept is traced here from ancient times to the present throungh some of its milestones: Anaximander's partly invisible celestial sphere and Pythagoras' spherical Earth; Eratosthenes' exemplary combination of astronomy and land surveying for the dual purpose of determining the size of the spherical Earth and making a map of the habitable world; the identical dual purpose followed by the Académie Royale des Sciences in the 17th century, but on a more sophisticated technical level; the challenge to the spherical concept by Newton's gravitational theory and the absorption of that theory into a wider concept of the Figure of the Earth; the acknowledgment of the irregular geoid by Gauss, Bessel, and Helmert, and the changed significance of the ellipsoid; Heiskanen's and Vening Meinesz' ‘Basic Hypothesis of Geodesy’ concerning the hydrostatic equilibrium of the Earth, and O'Keefe's contradiction on the basis of satelite data; the dream of global surveys come true through satellite geodesy and the accompanying inclusion of the outer gravity field of the Earth into the concept of its Figure; and lastly, the present and projected capability of high precision measurement and the widening of the concept of the Figure of the Earth from 3-dimensional rigidity to 4-dimensional time-dependence.  相似文献   

Upper Limit of Iodine Oxide in the Lower Stratosphere     

Irene Pundt  Jean-Pierre Pommereau  Celine Phillips  Eric Lateltin 《Journal of Atmospheric Chemistry》1998,30(1):173-185

It has been suggested that iodine oxides, IOx, could play a significant role in the ozone destruction in the lower stratosphere. To investigate this suggestion, spectra from nine SAOZ uv-visible spectrometer balloon flights were examined for the IO absorption signature between 405 and 450 nm. IO was not detected, either at mid- or high latitude, in the morning or the evening, in summer or winter. An upper limit of 0.2 parts per trillion by volume (pptv) at 20 km and 0.1 pptv at 15 km at the 95% confidence level (2), was derived from the best measurements at 90° SZA at sunset and sunrise. Since a photochemical model shows that 70% of inorganic iodine should be in the form IO at that time, it is concluded that unless iodine chemistry is different from that assumed at the moment, the role of iodine in stratospheric ozone depletion is small.  相似文献