Palaeoflood discharge estimation using dendrogeomorphic methods,rainfall-runoff and hydraulic modelling—a case study from southern Crete     

Ruman  Stanislav  Tichavský  Radek  Šilhán  Karel  Grillakis  Manolis G. 《Natural Hazards》2021,105(2):1721-1742

Natural Hazards - This study represents the first palaeoflood discharge estimation using dendrogeomorphic evidence from two ungauged catchments in southern Crete. Dendrogeomorphological methods,...  相似文献   

Spatial structure of standing wave electromagnetic fields at the lower harmonics of the ionospheric Alfvén resonator     

Karel Prikner  Felix Z. Feygin  Tero Raita 《Studia Geophysica et Geodaetica》2014,58(2):326-337

During the multiband wave Pc1 event on March 7, 2001 the EISCAT UHF and VHF incoherent scatter radars operated simultaneously covering an exceptionally wide altitude range of the ionosphere ～90—2000 km. This made possible to test the ionospheric Alfvén resonator (IAR) model over a large altitude range. The three lowest IAR eigenfrequencies, where the most of the Pc1 pulsation signal bands occur, were selected for the spatial analysis of the standing wave electromagnetic fields, applying the full-wave numerical simulation method. The altitude spread of amplitude maxima and nodes together with polarization characteristics of oscillation maxima in the horizontal plane are presented. The comparison of the standing wave oscillations on the altitude profile with the signal amplitude observed on the ground is also presented.  相似文献   

A simple smoothed velocity model of the uppermost Earth’s crust derived from joint inversion of Pg and Sg waves     

Karel Holub  Bohuslav Růžek  Jana Rušajová 《Acta Geophysica》2012,60(2):487-497

The paper presents some results of seismic experiments carried out on the territory of northern Moravia and Silesia, roughly delimited by the coordinates 16°E–19°E and 49°N–51°N. The experiments were aimed at compiling a velocity model of the uppermost Earth’s crust using the database of arrival times of Pg and Sg waves recorded at a fairly large number of seismic stations, which enabled us to produce a simple 1D-layered velocity model of the region. The velocity model was computed using the traditional tomographic iterative process composed of consecutive solutions of linear equations. Based on the analysis of velocity distribution, it was found that the velocities of Pg and Sg waves increase from about 5.9 and 3.3 km/s at the surface, to about 6.1 and 3.5 km/s at a depth of 11 km, respectively.  相似文献   

Tree‐age control on reconstructed debris‐flow frequencies: examples from a regional dendrogeomorphic reconstruction in the Crimean Mountains          下载免费PDF全文

Karel Šilhán  Tomáš Pánek  Jan Hradecký  Markus Stoffel 《地球表面变化过程与地形》2015,40(2):243-251

The Crimean Mountains (Ukraine) are renowned for the highest occurrence of debris flows along the northern coast of the Black Sea, but information on their origin, frequency and triggers is widely lacking. This study reconstructs a regional time series of debris flows in eight catchments located on the slopes above Yalta. Dendrogeomorphic analyses were performed on 1122 increment cores selected from 566 black pines (Pinus nigra ssp. pallasiana) with clear signs of external damage induced by past debris‐flow activity. The trees sampled were divided into old and young trees. The sample contains 361 young trees with post‐1930 innermost rings and 205 old trees with pre‐1930 germination dates. The two groups of trees were analyzed separately to identify possible age effects in the reconstructed debris‐flow series and to assess the ability of P. nigra to record geomorphic disturbances over time. We date a total of 215 debris flows back to ad 1701 and observe a mean decadal frequency of 6.9 events, with a peak in activity during the 1940s (20 events). The young trees record an increase in debris‐flow activity over the last 70 years, whereas the frequency of events remained fairly constant in the old trees for the same period. By contrast, the formation of reaction wood became increasingly scarce with increasing tree age whereas the occurrence of abrupt growth suppression increased. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Correlation Between Compositional Parts Based on Symmetric Balances     

Petra Kynčlová  Karel Hron  Peter Filzmoser 《Mathematical Geosciences》2017,49(6):777-796

Correlation coefficients are most popular in statistical practice for measuring pairwise variable associations. Compositional data, carrying only relative information, require a different treatment in correlation analysis. For identifying the association between two compositional parts in terms of their dominance with respect to the other parts in the composition, symmetric balances are constructed, which capture all relative information in the form of aggregated logratios of both compositional parts of interest. The resulting coordinates have the form of logratios of individual parts to a (weighted) “average representative” of the other parts, and thus, they clearly indicate how the respective parts dominate in the composition on average. The balances form orthonormal coordinates, and thus, the standard correlation measures relying on the Euclidean geometry can be used to measure the association. Simulation studies provide deeper insight into the proposed approach, and allow for comparisons with alternative measures. An application from geochemistry (Kola moss) indicates that correlations based on symmetric balances serve as a sensitive tool to reveal underlying geochemical processes.  相似文献   

PC1 with a broad frequency spectrum — “Goose pulsations”     

Felix Z. Feygin  Karel Prikner  Jorma Kangas 《Studia Geophysica et Geodaetica》2009,53(4):519-536

Geomagnetic pulsations in the frequency range of Pc1 pearl waves with the dynamic spectra having a very narrow spectrum width at the beginning of the event and a very broad spectrum width (Δf/f₀ ∼ 1) in the later part of the event are analyzed. One of the observed events shown by the dynamic spectrum resembles a goose with the beak at the beginning of the event and with the wing in the later part of the event. Various interpretations of these geomagnetic pulsations are presented taking into account nonlinear effects, quasilinear interaction of electromagnetic ion-cyclotron waves with energetic, anisotropic protons and modulation of plasma parameters in the magnetosphere by Pc3–5 hydromagnetic waves. The ionospheric effect in the signal formation is determined by the ionospheric Alfvén resonator. It can control the frequency range of the dynamic spectra, but not the internal structure of the signal.  相似文献   

Chemical fractionation of zinc versus cadmium among other metals nickel, copper and lead in the northern North Sea     

Rob F. Nolting  Hein J. W. de Baar  Klaas R. Timmermans  Karel Bakker 《Marine Chemistry》1999,67(3-4)

Concentrations of dissolved Ni, Cu, Zn, Cd and Pb were measured in water samples collected during a cruise with R.V Pelagia (29-6/14-7-1993) in the northern North Sea and N.E. Atlantic Ocean. At least six depths (0–90 m) were sampled with modified Go-Flo samplers from a rubber zodiac. In the study area, the first 25 m were well mixed and stratification occurred below this depth. The local bloom of Emiliania huxleyi hardly affected the trace metals concentration, except for some removal of Cd as seen from its correlation with nitrate. The mean dissolved concentrations were for Ni (3.66 nM), Cu (1.61 nM), Zn (4.5 nM), Cd (48 pM) and Pb (108 pM). These concentrations are among the lowest reported for the North Sea and are of similar magnitude to those found in the eastern North Atlantic at the same latitude. Zn was the only exception with values 10 times higher compared to those in the Atlantic Ocean, suggesting external inputs, mainly atmospheric and possibly from surrounding land masses. The observed ratio Zn:Cd in the North Sea and estuaries is in between the high ratio 600–900 for continental sources and the low ratio 5–10 for oceanic waters. Latter low ratio is consistent with the 21-fold stronger inorganic complexation of Cd in seawater which, in combination with the preferential biological uptake of Zn, may lead to the observed about hundredfold fractionation of Zn versus Cd in the marine system. Other processes may play a role but would need further investigation. The dissolved Pb values tend to be lower than found before in the North Sea, indicating decreasing inventories due to reduced anthropogenic emissions.  相似文献   

The fate of moderately volatile elements in impact events—Lithium connection between the Ries sediments and central European tektites          下载免费PDF全文

Zuzana Rodovská  Tomáš Magna  Karel Žák  Roman Skála  Tomasz Brachaniec  Channon Visscher 《Meteoritics & planetary science》2016,51(12):2403-2415

Lithium abundances and isotope compositions are presented for a suite of sediments from the surroundings of the Ries Impact structure, paralleled by new Li data for central European tektites (moldavites) from several substrewn fields (South Bohemia, Moravia, Cheb Basin, Lusatia), including a specimen from the newly discovered substrewn field in Poland. The data set was supplemented by three clay fractions isolated from sedimentary samples. Moldavites measured in this study show a very narrow range in δ⁷Li values (?0.6 to 0.3‰ relative to L‐SVEC) and Li contents (23.9–48.1 ppm). This contrasts with sediments from the Ries area which show remarkable range in Li isotope compositions (from ?6.9 to 13.4‰) and Li contents (0.6–256 ppm). The OSM sediments which, based on chemical similarity, formed the major part of moldavites, show a range in δ⁷Li values from ?2.0 to 7.9‰ and Li contents from 5.8 to 78.9 ppm. Therefore, the formation of moldavites was apparently accompanied by large‐scale mixing, paralleled by chemical and isotope homogenization of their parent matter. The proposed Li mixing model indicates that sands, clayey sediments, and low volumes of carbonates are the major components for tektite formation whereas residual paleokarst sediments could have been a minor but important component for a subset of moldavites. Striking homogenization of Li in tektites, combined with limited Li loss during impacts, may suggest that moderately volatile elements are not scavenged and isotopically fractionated during large‐scale collisions, which is consistent with recent models. In general, whether homogenization of bodies with distinct Li isotope systematics takes place, or collision of bodies with similar Li systematics operates cannot be resolved at present stage but Li isotope homogeneity of solar system planets and asteroidal bodies tentatively implies the latter.  相似文献   

Mechanics of Variscan Orogeny: A modern view on orogenic research     

Karel Schulmann 《Comptes Rendus Geoscience》2009,341(2-3):97-102

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Three-dimensional Crustal model of the Moravo-Silesian region obtained by seismic tomography     

Bohuslav Růžek  Karel Holub  Jana Rušajová 《Studia Geophysica et Geodaetica》2011,55(1):87-107

All recent available data sets containing traveltimes of Pg and Sg phases for the Moravo-Silesian region were collected. These data come from several experiments designed mostly in 2D (in-line) configurations. Simultaneous processing of all data is possible only considering the true 3D measurement geometry. The goal of this work is to establish the representative 3D seismic model by means of seismic tomography. The resulting minimum-structure model is presented in a simple and easy to use form on the Internet. The amount of processed data is relatively low but repeating the computations with new experimental data included would be very easy. Important material related to this paper is placed on web pages.  相似文献