Local Seismic Events in the Area of Poland Based on Data from the PASSEQ 2006–2008 Experiment

PASSEQ 2006–2008 (Passive Seismic Experiment in TESZ; Wilde-Piórko et al. 2008) was the biggest passive seismic experiment carried out so far in the area of Central Europe (Poland, Germany, the Czech Republic and Lithuania). 196 seismic stations (including 49 broadband seismometers) worked simultaneously for over two years. During the experiment, multiple types of data recorders and seismometers were used, making the analysis more complex and time consuming. The dataset was unified and repaired to start the detection of local seismic events. Two different approaches for detection were applied for stations located in Poland. The first one used standard STA/LTA triggers (Carl Johnson’s STA/LTA algorithm) and grid search to classify and locate the events. The result was manually verified. The second approach used Real Time Recurrent Network (RTRN) detection (Wiszniowski et al. 2014). Both methods gave similar results, showing four previously unknown seismic events located in the Gulf of Gdańsk area, situated in the southern Baltic Sea. In this paper we discuss both detection methods with their pros and cons (accuracy, efficiency, manual work required, scalability). We also show details of all detected and previously unknown events in the discussed area.     

Magnetic signature of indoor air pollution: Household dust study

The combination of magnetic and geochemical methods was used to determine the mineralogy, grain size and domain structure of magnetic particles in indoor dust collected in 195 sites in Warsaw, Poland. Data show an asymmetric distribution of magnetic susceptibility (χ) in the wide range of 20–1514 × 10^?8 m³ kg^?1. Comparison of magnetic parameters shows that the internal dust contains outside pollution characteristic for air and soil. More than 90% of indoor dust samples were characterized by roughly uniform magnetic mineralogy, typical for fine grained magnetite (diameter of 0.2–5 μm), and grain size between pseudo-single-domain and small multi-domain with small contribution of superpara-magnetic particles (～10%). Samples with χ larger than 220 × 10^?8 m³ kg^?1 contain mainly magnetite and an anthropogenic metallic Fe with T _C > 700°C. The indoor dust contains, characteristic for the urban areas, spherical magnetic particles originated from fossil fuel combustion processes and mixture of irregular angular iron-oxides grains containing other elements, including Na, Ca, Al, Si, K, S, Mn, Cl, and Mg.     

Application of real time recurrent neural network for detection of small natural earthquakes in Poland

This study is an application of a Real Time Recurrent Neural Network (RTRN) in the detection of small natural seismic events in Poland. Most of the events studied are from the Podhale region with a magnitude of 0.4 to 2.5. The population distribution of the region required that seismic signals be recorded using temporary stations deployed in populated areas. As a consequence, the high level of seismic noise that cannot be removed by filtration made it impossible to detect small events by STA/LTA based algorithms. The presence of high noise requires an alternate method of seismic detection capable of recognizing small seismic events. We applied the RTRN, which potentially can detect seismic signals in the frequency domain as well as in the phase arrival times. Data results of small local seismic events showed that the RTRN has the ability to correctly detect most of the events with fewer false detections than STA/LTA methods.     

Quantitative and Qualitative Assessment of Soil Erosion Risk in Małopolska (Poland), Supported by an Object-Based Analysis of High-Resolution Satellite Images

In 2011 the Marshal Office of Ma?opolska Voivodeship decided to evaluate the vulnerability of soils to water erosion for the entire region. The quantitative and qualitative assessment of the erosion risk for the soils of the Ma?opolska region was done based on the USLE approach. The special work-flow of geoinformation technologies was used to fulfil this goal. A high-resolution soil map, together with rainfall data, a detailed digital elevation model and statistical information about areas sown with particular crops created the input information for erosion modelling in GIS environment. The satellite remote sensing technology and the object-based image analysis (OBIA) approach gave valuable support to this study. RapidEye satellite images were used to obtain the essential up-to-date data about land use and vegetation cover for the entire region (15,000 km²). The application of OBIA also led to defining the direction of field cultivation and the mapping of contour tillage areas. As a result, the spatially differentiated values of erosion control practice factor were used. Both, the potential and the actual soil erosion risk were assessed quantificatively and qualitatively. The results of the erosion assessment in the Ma?opolska Voivodeship reveal the fact that a majority of its agricultural lands is characterized by moderate or low erosion risk levels. However, high-resolution erosion risk maps show its substantial spatial diversity. According to our study, average or higher actual erosion intensity levels occur for 10.6 % of agricultural land, i.e. 3.6 % of the entire voivodeship area. In 20 % of the municipalities there is a very urgent demand for erosion control. In the next 23 % an urgent erosion control is needed. Our study showed that even a slight improvement of P-factor estimation may have an influence on modeling results. In our case, despite a marginal change of erosion assessment figures on a regional scale, the influence on the final prioritization of areas (municipalities) according to erosion control needs is visible. The study shows that, high-resolution satellite imagery and OBIA may be efficiently used for P-factor mapping and thus contribute to a refined soil erosion risk assessment.     

Groundwater flow modelling of multi-aquifer systems for regional resources evaluation: the Gdansk hydrogeological system, Poland

In order to evaluate groundwater regional resources, a mathematical model of the Gdansk hydrogeological system (Poland) was developed. The research area covers about 2,800 km². Groundwater occurs in Cretaceous, Paleogene and Neogene formations. The recharge zone is situated in the glacial upland of the Kashubian Lake District. The discharge zone spreads over the lowlands of Gdansk and beneath the Bay of Gdansk (Baltic Sea). The MODFLOW program was used to develop a three-dimensional steady-state model on the basis of data from over 1,700 boreholes. The research area was digitalized as a square network of sides 200 m in length. Simplification of groundwater occurrence allowed four aquifers to be distinguished: upper Pleistocene, Pleistocene-Miocene, Oligocene-Eocene, and Cretaceous and also four intervening aquitards. The mathematical model calculations showed that the system is recharged mainly by precipitation (infiltration recharge is 136 mm/year). The precipitation recharge amounts to 1,045,440 m³/day. The other part of the inflow constitutes lateral flows from beyond the area of research and also to some extent from losing rivers and lakes. The runoff from the system takes place mainly through gaining streams and through lateral outflow including under-sea and lake discharge.     

A deterministic seismic hazard analysis for shallow earthquakes in Greece

The maximum expected ground motion in Greece is estimated for shallow earthquakes using a deterministic seismic hazard analysis (DSHA). In order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the period 426 BC–2003, a seismogenic source model with representative focal mechanisms and a set of velocity models. Because of the discrete character of the earthquake catalogue and of errors in location of single seismic events, a smoothing algorithm is applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude. Based on the selected input parameters synthetic seismograms for an upper frequency content of 1 Hz are computed on a grid of 0.2° × 0.2°. The resultant horizontal components for displacement, velocity, acceleration and DGA (Design Ground Acceleration) are mapped. The maps which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter were compiled for a mean return period of 476 years. Therefore, in order to validate our deterministic analysis, the final results are compared with PGA estimated from the maximum observed macroseismic intensity in Greece during the period 426 BC–2003.Since the results are obtained for point sources, with the frequency content scaled with moment magnitude, some sensitivity tests are performed to assess the influence of the finite extent of fault related to large events. Sensitivity tests are also performed to investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas. The ratios and the relative differences between the results obtained using different models are mapped and their mean value computed. The results highlight the importance in the deterministic approach of using good and reliable velocity models.     

Variable stars in the globular cluster NGC 6362

We report the results of a CCD search for short-period variables in the field of a southern globular cluster NGC 6362. We identified 19 new candidate variables, five of which are cluster RR Lyraes, four are probable SX Phe-type stars and eight are eclipsing binaries. Of the discovered binaries, three are EA-type systems, two of which are located on the cluster CMD in the turn-off region and the third 1 mag above the turn-off point, in the yellow straggler region. Five other systems are of W UMa type, three of which are foreground objects and two are likely cluster members. The remaining two candidates exhibit a modulation of the brightness level with an amplitude of 0.1–0.2 mag; further observations are needed to reveal the nature of their variability. Phased VI light curves for 20 variables (18 RR Lyrae stars and two blue stragglers) located in the central region of the cluster are presented.     

Amery ice shelf DEM and its marine ice distribution

1 Introduction The Amery Ice Shelf, the largest ice shelf in East Antarctica, has a total surface area of about6.1×104km2. The ice shelf drains the grounded ice fromthe interior of the Lam- bert Glacier drainage basin thatcovers an area of larger than1.3…     

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.