Estimating the maximum possible earthquake magnitude using extreme value methodology: the Groningen case

Natural Hazards - Both the river network and the regions outside the estuary mouths in the Pearl River Delta (PRD) of China experienced significant changes from 1999 to 2014. A validated...     

Geochemical and statistical approach to evaluate background concentrations of Cd,Cu, Pb and Zn (case study: Eastern Poland)

An attempt was made to evaluate background concentrations of Cd, Cu, Pb and Zn by means of geochemical and statistical approach. As many as 753 samples taken from 51 profiles located in Eastern Poland were analysed. For the estimation of geochemical background values, direct geochemical methods and a statistical analysis for the whole population of samples were applied. Average values of heavy metal concentration in loess sediments (bedrock) as well as in profiles not affected by human activity were measured. The iterative 2σ technique and calculated distribution function were chosen as statistical methods. The resulting values (background concentrations range) were as follows: Cd 0.5–0.9 mg kg⁻¹, Cu 5–16 mg kg⁻¹, Pb 12–26 mg kg⁻¹ and Zn 31–47 mg kg⁻¹. All the methods applied gave similar results. The highest deviation of the background was noted for Cu and the lowest for Zn. The lowest values of background were obtained for loess sediments and the highest in the case of the multiple 2σ method.     

Mortality of game mammals caused by an extreme flooding event in south-western Poland

We examine mortality in five terrestrial species of game animals resulting from an extreme flood event in Central Europe in July 1997. We present species-specific mortality rates and collate them with local abundances to show the susceptibilities of the different species to flood mortality. We also compare mortality rates in areas inundated by the main river and by its tributaries. Data were collected in the catchment area of the Odra River, south-western Poland. Mortality was estimated by surveying for drowned animals in flooded areas of 50 hunting districts (2,876 km²). Total mortality amounted to 3,613 individuals, mostly of roe deer Capreolus capreolus and brown hare Lepus europaeus. Relative to estimates of abundance, mortality was disproportionately high in hares. Drownings of roe deer and wild boar, Sus scrofa were proportional to local abundance. Young individuals were particularly affected. Mortality was low in foxes, Vulpes vulpes, and red deer, Cervus elaphus. The mortality rate increased with the proportion of area flooded and the duration of flooding and was four times higher along the Odra River than along its tributaries. Our data specify, for the first time, direct losses in wild, large animals in response to an extreme flood event. Despite high overall losses, negative long-term effects on populations seemed unlikely. Nevertheless, to lessen the impact, river management focused primarily on human safety should also integrate the needs of wildlife.     

Flotation study on high-hercynite ilmenite ores

Ilmenite from Polish magnetite-ilmenite ores has been floated with tall oil. Chemical and mineralogical analysis of the flotation products established that the ores containing hercynite are difficult to upgrade. For ore A (18.7% hercynite and 32.8% ilmenite) and ore B (9% hercynite and 41.3% ilmenite) poor concentrates containing much less than the required 45% TiO₂ have been obtained. It has been found that the higher concentration of hercynite in the feed, the lower the grade of concentrates in respect to TiO₂ is obtained. Ilmenite ore containing a minor amount of hercynite (ore C, 0.15% hercynite and 12.3 ilmenite) gives a good concentrate. By means of microscopic observation it was established that hercynite floats together with ilmenite in the rougher flotation but is partially depressed in the cleaning and scavenging flotation.     

Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250°C by means of Rietveld refinement of synchrotron data

Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M₁₂(Sb,As)₄S₁₃. Measurements were performed at 25 and 250°C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral ‘Cu1’–S distance (‘Cu1’ is a site of Fe substitution) and Cu2–S distances. Cu2 was refined as a split position; the Cu2–Cu2 split about the plane of the S1₂S2 triangle is about 0.56 and 0.65 Å for tetrahedrite and tennantite, respectively. Cu2–Cu2 distances in the structure cavity are 2.8–2.9 Å. Between 25 and 250°C, the lattice parameter a increased by 0.02–0.04 Å and the interatomic distances by 0.01 Å on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2–Cu2 split increases at 250°C by about 0.1 Å for tetrahedrite and by more than 0.15 Å for tennantite but the cage expansion is minimal so that the Cu2–Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.     

Darss Sill as a biological border in the fossil record of the Baltic Sea: evidence from diatoms

Biostratigraphical and palaeoecological analyses of cores along a transect from Femer Belt to the Arkona Basin reveal that North Sea waters began to enter the western Baltic Sea between 8600 and 8400 calibrated years BP. Studies of diatoms indicate that Mecklenburg Bay was characterised by slightly brackish-water conditions between 8400 and 8000 cal. years BP. At around 8000 cal. years BP increasing salinity is indicated by a strong dominance of the diatoms Paralia sulcata and Dimeregramma minor. Some centuries later another diatom assemblage appeared and became dominant in Mecklenburg Bay. This assemblage includes Hyalinella lateripunctata and Pravifusus hyalinus species typical of shallow water areas along the Atlantic coast today. At this time the first marine molluscs made their appearance. The oldest shell of a marine mollusc found in our material is dated to 7600 cal. years BP. The associated assemblage that includes adult specimens of the gastropod Aporrhais pespelicani indicates higher salinities than today.During the Littorina Sea stage a marine diatom flora with P. sulcata, Catenula adhaerens and D. minor crossed the Darss Sill and became widely distributed in the Arkona Basin, Pomeranian Bay and the Baltic Sea proper. In contrast, taxa indicative of the Hyalinella lateripunctata/P. hyalinus assemblage are only found west of the Darss Sill in Femer Belt and Mecklenburg Bay. Apparently, the Darss Sill threshold has been acting as an important salinity border from around 7800 cal. years BP until today.     

On some methodological problems in the use of environmental tracers to estimate hydrogeologic parameters and to calibrate flow and transport models

Environmental tracers are used qualitatively for a better formulation of conceptual models and quantitatively for assessing groundwater ages with the aid of box models or for calibrating numerical transport models. Unfortunately, tracers often yield different ages that do not represent uniquely the water ages. Difficulties result also from different definitions of age, e.g. water age, advective age, tracer age, or radiometric tracer age, that are measured differently and depend on aquifer parameters and characteristics of particular tracers. Even the movement of an ideal tracer can be delayed with respect to the advective movement of water due to diffusion exchange between mobile and immobile water zones, which for fissured rocks or thin aquifers, may lead to significant differences between advective and tracer ages, i.e. also between advective and tracer velocities. The advective velocity is of importance in water resources considerations as being related to Darcy velocity, whereas the tracer velocity is a more useful term for the prediction of pollutant transport. When a groundwater system changes from one hydrodynamic steady state to another, environmental tracers need much more time to reach a new steady state. Several tracer studies are recalled as examples of tracer-specific effects on the estimations of groundwater age.     

Non-integrability of the dumbbell and point mass problem

This paper discusses a constrained gravitational three-body problem with two of the point masses separated by a massless inflexible rod to form a dumbbell. This problem is a simplification of a problem of a symmetric rigid body and a point mass, and has numerous applications in Celestial Mechanics and Astrodynamics. The non-integrability of this system is proven. This was achieved thanks to an analysis of variational equations along a certain particular solution and an investigation of their differential Galois group. Nowadays this approach is the most effective tool for study integrability of Hamiltonian and non-Hamiltonian systems.     

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.