Analysis of the primary and secondary microseisms in the wavefield of the ambient noise recorded in northern Poland     

Simone Lepore  Marek Grad 《Acta Geophysica》2018,66(5):915-929

Seasonal changes of the primary and secondary microseisms were analysed in the wavefield of the ambient noise recorded during the entire 2014 at the “13 BB star” array located in northern Poland, composed of thirteen, symmetrically arranged, broadband seismic stations. To that, spectral analysis, seismic interferometry, surface scalar wind speed distribution, and beamforming were used. Spectral analysis allowed to observe that a splitting of the secondary microseism peak was present in winter and autumn, and that the primary microseism peak was visible in spring, summer and autumn. Using seismic interferometry, the long-term characteristics of the noise wavefield were recognized. The seasonal variations of the secondary microseism source were described by means of the analysis of the surface scalar wind speed for each month. The splitting of the secondary peak was attributed to the interaction of a strong wind blowing from the North Sea with a weak wind blowing from the Baltic Sea. The seasonal variations of the primary microseism peak were characterized through the frequency-domain beamforming. The peak was identified during spring, summer and autumn, when the generated wavefield was coming from the Baltic Sea. The velocity of the wavefield was evaluated within the 2.0–5.0 km/s range. The described mechanism of generation of the microseisms, based on the interaction of the nearby winds, was found to be consistent with the models reported in the literature.  相似文献   

Sub-annual moraine formation at an active temperate Icelandic glacier     

Benjamin M.P. Chandler  Samuel J.P. Chandler  David J.A. Evans  Marek W. Ewertowski  Harold Lovell  David H. Roberts  Martin Schaefer  Aleksandra M. Tomczyk 《地球表面变化过程与地形》2020,45(7):1622-1643

This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low-relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub-annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub-annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt-driven squeeze events and (ii) larger push moraines formed during winter re-advances. We suggest the development of this process-form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice-marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process-form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Sediment accumulation rates in subpolar fjords – Impact of post-Little Ice Age glaciers retreat,Billefjorden, Svalbard     

Witold Szczuciński  Marek Zajączkowski  Jan Scholten 《Estuarine, Coastal and Shelf Science》2009

The Little Ice Age (∼1600–1900 AD) and 20th century sediment accumulation rates in Billefjorden, a subpolar fjord on Svalbard, were reconstructed by applying ²¹⁰Pb, ¹³⁷Cs and AMS ¹⁴C datings. The modern sediment accumulation rate decreases from more than 0.39 cm y⁻¹ at the fjord head to 0.08 cm y⁻¹ close to the fjord mouth. However, during the Little Ice Age the sediments accumulated at a much lower rate of 0.02 cm y⁻¹ in the central fjord basin. This difference is most likely related to the rapid retreat of glaciers during the 20th century, when most of them withdrew up to 2 km. The post-Little Ice Age increases in temperature and a negative glacier mass balance resulted in a larger meltwater discharge transferring substantial amounts of sediments released from the glaciers, as well as those eroded from previously stored unconsolidated glacial sediments. A comparison of data from the subpolar fjords of Svalbard suggests that the increase in the sediment accumulation rate is a common trend, and further increases might be expected if climate warming continues. The properties of the fjord sediments (grain size, IRD, coarse-fraction composition, clay mineralogy) from the Little Ice Age and the 20th century showed no distinct differences. The change in the accumulation rate may be the most evident sedimentary record of this climatic change.  相似文献   

The Lateglacial and Holocene in Central Europe: a multi‐proxy environmental record from the Bohemian Forest,Czech Republic          下载免费PDF全文

Klára Vočadlová  Libor Petr  Pavla Žáčková  Marek Křížek  Lenka Křížová  Simon M. Hutchinson  Miroslav Šobr 《Boreas: An International Journal of Quaternary Research》2015,44(4):769-784

The Hercynian mountain ranges were islands of mountain glaciation and alpine tundra in a Central European ice‐free corridor during the Late Pleistocene. Today they are notable areas of glacial landforms, alpine‐forest free areas, peatlands and woodlands. However, our knowledge of the Lateglacial and early Holocene environmental changes in this region is limited. We present a new multi‐proxy reconstruction of a mid‐altitude environment in the Bohemian Forest spanning this period. A core (5.2 m length) in the ?erné Lake cirque (1028 m a.s.l.) was subjected to lithological, geochemical, pollen and macrofossil analysis supplemented by two optically stimulated luminescence (OSL) and 10 AMS radiocarbon dates. We determined the impact of regional and supraregional climate changes on the environment. The two most significant changes in sedimentation during the Lateglacial (17.6 and 15.8–15.5 cal. ka BP) were synchronous with regional glacial chronostratigraphy. Unlike Central European mountain ranges, in the Bohemian Forest the Younger Dryas was not coincident with glacier re‐advance, but was a dry, cold episode with low lake levels, which prevailed until the early Preboreal. Plant macrofossils indicate local establishment of Betula nana and Betula pendula/pubescens at 15.4–13.4 cal. ka BP. Comparison with Holocene records from Central Europe shows a similar immigration history of vegetation at mid and higher altitudes. The tree line exceeded an altitude of ~1000 m a.s.l. around 10.5 cal. ka BP and coincided with rapid geochemical changes in the sediment. The 8.2 ka BP event did not have any response in the sedimentary record, but corresponded to stabilization of the Picea abies population and expansion of Fagus. Fagus colonized the Bohemian Forest earlier than other Hercynian mid‐mountains, but never predominated in the composition of the forest at higher elevations. Abies alba was the last tree species that immigrated to the study area.  相似文献   

Lightcurve Analysis,Shapes and Spins of Asteroids Ermolova and Silver from Long-Term Observations     

Marek Husárik 《Earth, Moon, and Planets》2016,119(1):35-45

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The Košice meteorite fall: Recovery and strewn field          下载免费PDF全文

Juraj Tóth  Ján Svoreň  Jiří Borovička  Pavel Spurný  Antal Igaz  Leonard Kornoš  Peter Vereš  Marek Husárik  Július Koza  Aleš Kučera  Pavel Zigo  Štefan Gajdoš  Jozef Világi  David Čapek  Zuzana Krišandová  Dušan Tomko  Jiří Šilha  Eva Schunová  Marcela Bodnárová  Diana Búzová  Tereza Krejčová 《Meteoritics & planetary science》2015,50(5):853-863

We provide the circumstances and details of the fireball observation, search expeditions, recovery, strewn field, and physical characteristics of the Ko?ice meteorite that fell in Slovakia on February 28, 2010. The meteorite was only the 15th case of an observed bolide with a recovered mass and subsequent orbit determination. Despite multiple eyewitness reports of the bolide, only three videos from security cameras in Hungary were used for the strewn field determination and orbit computation. Multiple expeditions of professionals and individual searchers found 218 fragments with total weight of 11.3 kg. The strewn field with the size of 5 × 3 km is characterized with respect to the space distribution of the fragments, their mass and size‐frequency distribution. This work describes a catalog of 78 fragments, mass, size, volume, fusion crust, names of discoverers, geographic location, and time of discovery, which represents the most complex study of a fresh meteorite fall. From the analytical results, we classified the Ko?ice meteorite as an ordinary H5 chondrite.  相似文献   

Cosmology beyond the standard model: Multi-component dark matter model     

M.?DemiańskiEmail author  A.?G.?Doroshkevich 《Astronomy Reports》2015,59(6):491-493

We show that both the mass and composition of dark matter (DM) particles strongly influence the formation of low mass DM halos. Comparison of theoretical predictions with observations allows us to select the more promising DM models. More details can be found in our paper arXiv:1404.3362.  相似文献   

Ruthenium in komatiitic chromite     

Marek Locmelis  Norman J. Pearson  Marco L. Fiorentini 《Geochimica et cosmochimica acta》2011,75(13):3645-3661

The distinction between Ru in solid solution and Ru-bearing inclusions is essential for the predictive modeling of platinum-group element (PGE) geochemistry in applications such as the lithogeochemical exploration for magmatic sulfide deposits in komatiites. This study investigates the role of chromite in the fractionation of Ru in ultramafic melts by analyzing chromite grains from sulfide-undersaturated komatiites and a komatiitic basalt from the Yilgarn Craton in Western Australia. In situ analysis using laser ablation ICP-MS yields uniform Ru concentrations in chromites both within-grain and on a sample scale, with concentrations between 220 and 540 ppb. All other platinum-group elements are below the detection limit of the laser ablation ICP-MS analysis. Carius tube digestion isotope dilution ICP-MS analysis of chromite concentrates confirms the accuracy of the in-situ method. Time resolved laser ablation ICP-MS analyses have identified the presence of sub-micron Ir-bearing inclusions in some chromite grains from the komatiitic basalt. However, Ru-bearing inclusions have not been recognized in the analyzed chromites and this combined with the in situ data suggests that Ru exists in solid solution in the crystal lattice of chromite. These results show that chromite can control the fractionation and concentration of Ru in ultramafic systems.  相似文献   

Hydrologic and geologic factors controlling groundwater geochemistry in the Turonian aquifer (southern Tunisia)   总被引：2，自引：0，他引：2  

Kamel Abid  Kamel Zouari  Marek Dulinski  Najiba Chkir  Brahim Abidi 《Hydrogeology Journal》2011,19(2):415-427

Water in the fissured limestone and dolomite of the Turonian aquifer of Tunisia has been investigated using geochemical (major ions) and isotopic (δ¹⁸O, δ²H, ¹⁴C) data. To carry out a characterization of aquifer behaviour, 48 representative samples were collected at the end of the humid season. The evolution of chemical composition of groundwater from recharge areas to discharge areas is characterized by increasing sodium, chloride and sulphate contents as a result of leaching of evaporite rock. In the study, three distinct chemical trends in groundwater were identified. The major reactions responsible for the chemical evolution of groundwater in the investigated area fall into three categories: (1) calcite precipitation, (2) gypsum and halite dissolution, and (3) ion exchange. The stable isotope composition of water samples indicates large-scale interaction between the Continental Intercalaire and the Turonian aquifer and the presence of a young local component which probably enters the system via faults and/or fractures.  相似文献   

Deciphering interaction of regional aquifers in Southern Tunisia using hydrochemistry and isotopic tools     

Kamel Abid  Marek Dulinski  Friha Hadj Ammar  Kazimierz Rozanski  Kamel Zouari 《Applied Geochemistry》2012

Groundwater is the most important source of water supply in southern Tunisia. Previous hydrogeologic and isotopic studies carried out in this region revealed the existence of two major aquifer systems: the “Complex Terminal” (CT) and the “Continental Intercalaire” (CI). Turonian carbonates constitute one of the major aquifer levels of the CT multilayered aquifer. It extends over most of southern Tunisia, and its hydrodynamic regime is largely influenced by tectonics, lithology and recharge conditions. Forty-eight groundwater samples from the CI and Turonian aquifers were collected between January and April 2004 for chemical and isotopic analyses. Hydrochemistry and isotopic tools were combined to get an insight into the processes controlling chemical composition of groundwater and wide-scale interaction of these two aquifer systems. Analysis of the dissolved constituents revealed that several processes control the observed chemical composition: (i) incongruent dissolution of carbonate minerals, (ii) dissolution of evaporitic minerals, and (iii) cation exchange. Dissolution alone cannot account for the observed high supersaturation states of groundwater with respect to calcite and dolomite. The observed supersaturation is most probably linked to geogenic CO₂ entering water-bearing horizons of the CT and CI aquifers via deep tectonic faults and discontinuities and subsequent degassing in the exploitation wells. Presence of geogenic CO₂ in the investigated region was confirmed by C isotope data of the DIC reservoir. The radiocarbon content of the Turonian samples varied between 9.5 and 43 pmc. For CI samples generally lower values were recorded, between 3.8 and 22.5 pmc. Stable isotope composition of Turonian groundwater samples varied from −8.3 to −5.3‰ for δ¹⁸O and from −60 to −25‰ for δ²H. The corresponding ranges of δ values for the Continental Intercalaire samples were from −8.9‰ to −6.9‰ for δ¹⁸O and from −68.2‰ to −45.7‰ for δ²H. Stable isotope composition of groundwater representing CT and CI aquifers provide strong evidence for regional interaction between both systems.  相似文献