Derivation of the Theis (1935) Equation by Substitution     

by Tomas Perina 《Ground water》2010,48(1):6-7

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Magnetic properties and Archeointensity of Earth’s magnetic field recovered from El Opeño,earliest funeral architecture known in Western Mesoamerica     

Modesto Pineda Duran  Avto Goguitchaichvili  Juan Morales  Bertha Aguilar Reyes  Luis M. Alva Valdivia  Arturo Oliveros-Morales  Manuel Calvo-Rathert  Tomas Gonzalez Moran  Jasinto Robles-Camacho 《Studia Geophysica et Geodaetica》2010,54(4):575-593

Despite of the impressive cultural heritage and abundant archaeological sites, absolute geomagnetic intensity data from Mesoamerica are still sparse. Archeointensity determinations using the Coe variant of the Thellier and Thellier method have been carried out on some selected pottery fragments from the El Opeño archeological site which has the earliest funeral architecture known in western Mesoamerica. The El Opeño chronology is supported by six C¹⁴ datings performed on carbon-bearing materials. Detailed rock magnetic experiments including susceptibility vs. temperature curves, hysteresis cycles and thermal demagnetization procedures were carried out in order to estimate the magnetic carriers and their stability. Cooling rate and anisotropy remanence corrected intensity values range from 25.0 ± 2.3 to 40.2 ± 3.0 μT and corresponding virtual axial dipole moments (VADM) range from 5.6 ± 0.5 to 8.9 ± 0.7 × 10²² Am². In addition, we present here a new compilation and analysis of existing absolute intensity data in order to try to estimate the variation of the Earth’s magnetic field over the past three millennia. The mean archeointensity obtained in the present study agrees reasonably well with the predicted absolute intensities retrieved from the CALS7K main field model. Other available Mesoamerican data, however, differ from this model. Most of available archeointensity data from Mesoamerica agree reasonably well with the ARCH3K main field model prediction. The broad peak defined at about 50 A.D. by our data is also predicted by the CALS3k.3 main field model but slightly displaced to the right while two smaller peaks are observed on the ARCH3K curve for the same time interval. The intensity value obtained at about 200 B.C. is a clear outlier and thus its geomagnetic significance should be confirmed by further investigations.  相似文献   

The impacts of a Laki-like eruption on the present Swedish society     

Karin Mossberg Sonnek  Tomas Mårtensson  Ester Veibäck  Peter Tunved  Håkan Grahn  Pontus von Schoenberg  Niklas Brännström  Anders Bucht 《Natural Hazards》2017,88(3):1565-1590

In this study, we analyse and discuss the possible impacts on the Swedish society of a volcanic eruption on Iceland, emitting ash particles and large quantities of sulphur dioxide. A scenario was developed, based on the historical Laki eruption of 1783–1784, to describe the content of a potential sulphur fog over time in Sweden. Due to its high complexity and the many uncertainties in the underpinning scientific data, the scenario was developed using a cross-disciplinary approach incorporating experts from different scientific fields. An analysis of the impacts of the hazard on human health, environment and technical equipment was then performed and, finally, representatives from national authorities assessed the overall societal challenges in responding to the consequences of a massive volcanic eruption. The analysis shows that it is the peak concentrations of sulphur dioxide and sulphuric acid rather than the longer periods of moderate concentrations that contribute most to the negative consequences for human health and environment. Altogether, three societal challenges were identified: the ability to compile and disseminate relevant information fast enough, to perform continuous measurements of concentrations of different substances in affected areas and to meet the large demand for medical care.  相似文献   

Archaean greenstone belt from the Central African Republic (Equatorial Africa)     

J.L. Poidevin  J. Dostal  C. Dupuy 《Precambrian Research》1981,16(3):157-170

The Bandas belt, one of two prominent Archaean greenstone belts in the Central African Republic (Equatorial Africa), is ca. 250 km long. At the southernmost part of the belt, a metasedimentary—metavolcanic rock suite is preserved only in brachysynclines. The suite can be divided into two lithostratigraphic units. The lower unit is composed predominantly of volcanic rocks, while the upper one contains mainly metasedimentary rocks. The volcanic rocks, which are part of a sequence ca. 3600 m thick, can be sub-divided according to stratigraphic position, lithology and geochemistry into three groups. The lowermost group includes low-K tholeiitic basalts depleted in light REE. The second group consists of tholeiitic basalts with light REE-enriched patterns and the third, uppermost, group includes andesites, which are similar in several respects to Recent calc-alkaline andesites.The tholeiitic basalts of the first two groups are probably related to different upper mantle sources. The andesites of the third group were produced either by fractional crystallization from a basaltic magma enriched in light REE or equilibrium melting of eclogite or garnet amphibolite.  相似文献   

Hydrogeological model of the Baltic Artesian Basin   总被引：1，自引：0，他引：1  

Janis Virbulis  Uldis Bethers  Tomas Saks  Juris Sennikovs  Andrejs Timuhins 《Hydrogeology Journal》2013,21(4):845-862

The Baltic Artesian Basin (BAB) is a complex multi-layered hydrogeological system in the south-eastern Baltic covering about 480,000 km². The aim of this study is to develop a closed hydrogeological mathematical model for the BAB. Heterogeneous geological data from different sources were used to build the geometry of the model, i.e. geological maps and stratigraphic information from around 20,000 boreholes. The finite element method was used for the calculation of the steady-state three-dimensional (3D) flow of unconfined groundwater. The 24-layer model was divided into about 1,000,000 finite elements. A simple recharge model was applied to describe the rate of infiltration, and the discharge was set at the water-supply wells. Variable hydraulic conductivities were used for the upper (Quaternary) deposits, while constant hydraulic conductivity values were assumed for the deeper layers. The model was calibrated on the statistically weighted borehole water-level measurements, applying L-BFGS-B (automatic parameter optimization method) for the hydraulic conductivities of each layer. The principal flows inside the BAB and the integral flow parameters were analyzed. The modeling results suggest that deeper aquifers are characterized by strong southeast–northwest groundwater flow, which is altered by the local topography in the upper, active water-exchange aquifers.  相似文献   

Mantle source heterogeneity of the Early Jurassic basalt of eastern North America     

Gregory Shellnutt  J.  Dostal  Jaroslav  Yeh  Meng-Wan 《International Journal of Earth Sciences》2018,107(3):1033-1058

International Journal of Earth Sciences - One of the defining characteristics of the basaltic rocks from the Early Jurassic Eastern North America (ENA) sub-province of the Central Atlantic Magmatic...  相似文献   

Multi-methodological approach to evaluate trace elements and major components in wetland system with subsaline and freshwater characteristics     

Vlado Cuculić  Stanislav Frančišković-Bilinski  Halka Bilinski  Krešimir Maldini  Damir Tomas  Nenad Tomašić 《Environmental Earth Sciences》2016,75(20):1351

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Rifts,arcs and orogens in space and time: a volume in honor of J. Duncan Keppie—an introduction     

J. Brendan Murphy  R. Damian Nance  Jaroslav Dostal  Cecilio Quesada 《International Journal of Earth Sciences》2014,103(5):1181-1186

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