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Timo Tiira Tomasz Janik Elena Kozlovskaya Marek Grad Annakaisa Korja Kari Komminaho Endre HegedŰs Csaba Attila Kovács Hanna Silvennoinen Ewald BrŰckl 《Pure and Applied Geophysics》2014,171(7):1129-1152
We have studied the lateral velocity variations along a partly buried inverted paleo–rift in Central Lapland, Northern Europe with a 2D wide-angle reflection and refraction experiment, HUKKA 2007. The experiment was designed to use seven chemical explosions from commercial and military sites as sources of seismic energy. The shots were recorded by 102 stations with an average spacing of 3.45 km. Two-dimensional crustal models of variations in P-wave velocity and Vp/Vs-ratio were calculated using the ray tracing forward modeling technique. The HUKKA 2007 experiment comprises a 455 km long profile that runs NNW–SSE parallel to the Kittilä Shear Zone, a major deformation zone hosting gold deposits in the area. The profile crosses Paleoproterozoic and reactivated Archean terranes of Central Lapland. The velocity model shows a significant difference in crustal velocity structure between the northern (distances 0–120 km) and southern parts of the profile. The difference in P-wave velocities and Vp/Vs ratio can be followed through the whole crust down to the Moho boundary indicating major tectonic boundaries. Upper crustal velocities seem to vary with the terranes/compositional differences mapped at the surface. The lower layer of the upper crust displays velocities of 6.0–6.1 km/s. Both Paleoproterozoic and Archean terranes are associated with high velocity bodies (6.30–6.35 km/s) at 100 and 200–350 km distances. The Central Lapland greenstone belt and Central Lapland Granitoid complex are associated with a 4 km-thick zone of unusually low velocities (<6.0 km/s) at distances between 120 and 220 km. We interpret the HUKKA 2007 profile to image an old, partly buried, inverted continental rift zone that has been closed and modified by younger tectonic events. It has structural features typical of rifts: inward dipping rift shoulders, undulating thickness of the middle crust, high velocity lower crust and a rather uniform crustal thickness of 48 km. 相似文献
574.
Francesca Bruno Daniela Cocchi Fedele Greco Elena Scardovi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1235-1245
Rainfall is a phenomenon difficult to model and predict, for the strong spatial and temporal heterogeneity and the presence of many zero values. We deal with hourly rainfall data provided by rain gauges, sparsely distributed on the ground, and radar data available on a fine grid of pixels. Radar data overcome the problem of sparseness of the rain gauge network, but are not reliable for the assessment of rain amounts. In this work we investigate how to calibrate radar measurements via rain gauge data and make spatial predictions for hourly rainfall, by means of Monte Carlo Markov Chain algorithms in a Bayesian hierarchical framework. We use zero-inflated distributions for taking zero-measurements into account. Several models are compared both in terms of data fitting and predictive performances on a set of validation sites. Finally, rainfall fields are reconstructed and standard error estimates at each prediction site are shown via easy-to-read spatial maps. 相似文献
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Shaking table tests of a reinforced concrete waffle–flat plate structure designed following modern codes: seismic performance and damage evaluation
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Shaking table tests were conducted on a scaled reinforced concrete waffle–flat plate structure. It represented a conventional construction design under current building codes in the Mediterranean area. The test structure was subjected to a sequence of four seismic simulations of increasing magnitude. Each simulation was associated with a seismic hazard level characterized by the mean return period PR. The test structure performed well for the simulations associated with PR = 95, 475 and 975 years but collapsed under the maximum considered earthquake of PR = 2475 years. Damage concentrated at column bases, where the maximum chord rotation reached 93% of the ultimate capacity, and at the transverse beams of the exterior plate‐to‐column connection that failed in torsion. It is shown that most (from 85% to 90%) of the energy input by the earthquake that contributes to damage is dissipated by the plate. The capacity curve of the tested structure estimated from the experimental base shear vs. top displacement relationship allowed us to compute the overstrength (1.4). It is close to the maximum established by European code EN 1998‐1 (1.5). Based on a detailed study of the test results, potential updates to current codes and design recommendations are suggested. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
578.
Vitaliy D. Rusov Vladimir N. Vaschenko Elena P. Linnik Оksana T. Myhalus Yuriy A. Bondartchuk Vladimir P. Smolyar Sergey I. Kosenko Strachimir Cht. Mavrodiev Boyko I. Vachev 《Journal of Atmospheric and Solar》2010,72(5-6):389-397
The solution of energy-balance model of the Earth global climate and the EPICA Dome C and Vostok experimental data of the Earth surface palaeotemperature evolution over past 420 and 740 kyr are compared.In the framework of proposed bifurcation model (i) the possible sharp warmings of the Dansgaard-Oeschger type during the last glacial period due to stochastic resonance is theoretically argued; (ii) the concept of climatic sensitivity of water in the atmosphere, whose temperature instability has the form of so-called hysteresis loop, is proposed, and based on this concept the time series of global ice volume over the past 1000 kyr, which is in good agreement with the time series of δ18O concentration in the sea sediments, is obtained; (iii) the so-called “CO2 doubling” problem is discussed. 相似文献
579.
Boris P. Ilyashuk Elena A. Ilyashuk Eugeny A. Makarchenko Oliver Heiri 《Journal of Paleolimnology》2010,44(2):667-676
Larvae of the genus Pseudodiamesa Goetghebuer, which includes 12 described valid species and is divided by Makarchenko and Makarchenko (1999) into two species groups, Pseudodiamesa branickii group and Pseudodiamesa
nivosa group, are widespread in lakes and running waters of cold, high-latitude and high-altitude areas of the Northern Hemisphere.
Larval remains of the genus are often found in subfossil assemblages from these cold regions, but intra-genus morphotypes
usually are not distinguished by palaeoecologists. Current knowledge of the ecology of the species indicates that the Pseudodiamesa nivosa group is more cold-adapted than the Pseudodiamesa branickii group and, therefore, these two intra-genus morphotypes cannot be amalgamated into a larger taxonomic unit without losing
substantial information. Here we present the morphological characters of head capsules of Pseudodiamesa larvae attributed to the different species-group morphotypes, which are clearly visible in subfossil specimens. The information
summarized in this paper will help provide more reliable chironomid-based palaeoclimatic inferences from lake sediment records
covering colder phases through the late Quaternary in the Northern Hemisphere. 相似文献
580.
Elena Gottardini Fabiana Cristofolini Elena Paoletti Paolo Lazzeri Giancarlo Pepponi 《Journal of Atmospheric Chemistry》2004,49(1-3):149-159
Biological characterization of Corylus avellana L. and Pinus nigra L. pollen samples was carried out to determine the actual value of pollen as a bio-indicator of the effects of atmospheric pollution, using samples from plants naturally developed in sites controlled for air pollution. In Trentino (North Italy), we selected six stations at three different levels of air pollution, which are constantly monitored with automatic gauges by the Environmental Protection Agency of Trento.First results showed that pollen viability of both species, germinability and pollen tube length of P. nigra, were higher in areas with no road traffic compared to heavy traffic ones. Pollen viability of P. nigra was positively correlated to ozone (O3) concentrations and altitude but negatively to sulphur dioxide (SO2), particulate matter with a diameter less than 10 m (PM10), nitrogen oxides (NOx) and nitrogen dioxide (NO2) concentrations. 相似文献