Thessaly lies on the Aegean (micro-)plate, undergoing internal crustal deformation due to the plate relative motion against the adjacent Anatolian and Nubian plates. As a result, the whole Thessalian Basin was supposed to be under an extensional tectonic regime of N-S direction. However, the recent earthquake sequence of March 2021 which occurred close to the northwestern margin of the basin revealed NE-SW direction of extension. Based on 7-year GPS measurements recorded by stations installed within and around the basin we assessed four deformational parameters for Thessaly aiming at the understanding of the deformation processes that control the region. These parameters are i) the Maximum Horizontal Extension (MAHE), ii) the Total Velocity (TV), iii) the Maximum Shear Strain (MSS), and iv) the Area Strain (AS). The results show that during the monitoring period, Thessaly moved toward the S-SW with a simultaneous clockwise rotation and underwent dispersed deformation mostly associated with dilatation. Focusing on the epicentral area of the 2021 sequence, strain during the 7-year period was rather low in all three strain parameters, implying a mature stage of elastic strain accumulation before the fault rupture., Ilias Lazos, Sotirios Sboras, Konstantinos Chousianitis, Stylianos Bitharis, Evaggelos Mouzakiotis, Vassilios Karastathis, Christos Pikridas, Aristeidis Fotiou and Dimitris Galanakis., and Obsahuje bibliografii
The aim of this paper is to present the results of an investigation of induced seismic events which occurred during mining in the coalfields of Plants Paskov and Staříč of the Paskov Mine which belong to the southern part of the Ostrava-Karviná coal mines. Some results obtained in the time period January 1992 - December 2002 have already been published, and therefore, are mentioned here only briefly. The paper is based on new results of seismological observations at the OKC, KLOK, STEB seismic stations operated by the Institute of Geonics AS CR and stations of the Green Gas DPB, a.s., Paskov. A total of 26 seismic events were monitored from January 2008 to February 2012, most of them were localized into the area under study. As for the energy span of individual events according to the energetic classification of the Geophysical Centre of the Green Gas DPB, a.s., Paskov, all seismic events in Table 1 were estimated within the limits E(J) <5.0 ×102 ÷ 2.0 × 104>., Karel Holub, Jana Rušajová and Josef Holečko., and Obsahuje bibliografii
The Institute of the Rock Structure and Mechanics AS CR operates the GEONAS network that now consists of 17 perm anent GPS observatories. The outliers and in consistencies occur within the time series observed in the winter season 200 5/2006 for the position of the GNSS antennas of the observatories SNEC and BISK located high in the m ountains, at th e Sněžka Mt. (1602 m, the Giant Mts.) and the Biskupská kupa Mt. (890 m, the Jeseníky Mts.) respectively. Therefore web cameras and meteorological sensors were in stalled at GEONAS observatories located in the mountain regions. The snow coverage and other meteorological influences affecti ng the antennas monitoring GPS signals at these observatories were estimated. The individual photos were analyzed and compared to variations in the time series to obtain the time series for winter seasons reducing the snow coverage effects., Milada Grácová, František Mantlík, Vladimír Schenk and Zdeňka Schenková., and Obsahuje bibliografické odkazy
The essential point for seismological observation in the northern part of Moravia, Czech Republic, is a permanent seismic station Ostrava - Krásné Pole (OKC) that is a part of the Czech regional seismological network (hereafter CRSN). Institute o f Geonics AS CR, v.v.i., has also operated temporary seismic stations in this region since 1997. Current seismological stations are located in an abandoned mine working located in Zlaté Hory and in cellars in Klokočov and castle Raduň near Opava. The natural seismicity is after the swarm of microearthquakes in the vicinity of Opava in 1993 very low now. In region under discussion, seismic manifestations generated by mining induced seismicity in Upper Silesian Coal Basin (both Karviná an d Polish parts) and in Legnica-Głogów Copper District (LGOM) are also detected. Significant part of observations in this region is made by the Institute of Physics of the Earth (hereafter IPE), Masaryk University Brno, and about 1000 microearthquakes have been detected during the last ten years with maximum local magnitude up to 1.9., Zdeněk Kaláb, Jaromír Knejzlík and Karel Holub., and Obsahuje bibliografické odkazy
The article deals with estimating deformation between the African and the Eurasian Plate in the Eastern Mediterranean on the basis of GPS coordinate time series. Two sources of velocities were used for processing. The first was the freely available site velocities from the European Permanent Network (EPN). The second was the Egyptian GPS permanent network velocities. Their values were determined by the following technique. Firstly, the Egyptian site coordinates were computed from GPS daily observations, using the fiducial EPN stations. The daily site coordinates at a given time interval result in coordinate time series, which were analysed and used on velocity estimation of the Egyptian stations. Then the apparatus of the mechanics of continuum was applied to all resultant velocities. The regions of possible mutual interactions between the Eurasian and the African Plate in the Eastern Mediterranean were detected. The basic idea of this contribution is the common processing of GPS daily measurements from the Egyptian permanent network together with the EPN data. The available Egyptian GPS data cover almost the last three years, which represents a sufficient time interval for velocity estimation. Introducing the Egyptian permanent GPS measurements into processing enables a better estimate of deformations in the Eastern Mediterranean., Antonín Zeman, Khalil Hassan, Jan Holešovský, Abdel Monem S. Mohamed, Zbyněk Novotný, Mahmoud M. Salah, Jan Kostelecký and Radwan M. Ali., and Obsahuje bibliografii
Brown coal open pit mining in the basin under Krušné Hory Mts. came to contact with slopes of the mountains, and a problem of the stability in high and steep slopes in the crystalline rock became an important question. The question concerns Jezeří Castle built on the top of one of the hills in a most endangered section where even a supporting pillar in the sediments under the slope toe was left to support the slope. As a result, an extensive monitoring program regarding deformations was initiated in the region. The program involved several methods and some important results are discussed. The results that are displayed concern mainly measurements done in geophysical tiltmeter stations in two underground galleries driven into the two steep slope sections showing most dangerous situation, as well as extensometers located in the same locations. Long-term monitoring revealed a tectonic deformation process of a natural origin that is registered as slow and systematic tilts. Besides, it revealed several periods of anomalies that are of basic importance. During a long period of observation from 1982 till 2005 three important deformation anomalies were registered: the event of 1994, the event of 2002, and the event of 2003/2004. The first and the third event have been classified as of a large regional character that affected a wide mountainous area and could be interpreted as a tectonic impulse originating within the mountainous structure of the so called "Dome of Hora Svaté Kateřiny". The second event has been considered different, strictly connected with extreme precipitation of August 2002. The anomaly was evidenced even deep in the crystalline, so that it could not be seen as of a superficial character only. The movement which was registered at that time was oriented right into the pillar supporting the slope., It is concluded that it was a short manifestation of instability in the critical profile "Jezeří - pillar", which stresses the important stabilisation function of the supporting pillar without which the profile will be probably destabilised., Blahoslav Košťák, Bohumil Chán and Jan Rybář., and Obsahuje bibliografii
a2_The town of Litija was hit by four damaging earthquakes in the last 120 years which reached a maximum intensity of VII-VIII MSK. The town is located in a shallow sedimentary basin filled with relatively soft Quaternary sediments in which seismic site amplification is expected. On the other hand no borehole or geophysical data are available to support quantitative assessment of site effects. As a contribution to the first seismic microzonation of the area, we performed a free-field study based on the microtremor HVSR method in order to assess the resonance frequency of th e sediments. In ge neral clear spectral peaks were obtained for 57 measuring points which show distribution of frequencies in a broad range between 4.4 an d 22.7 Hz. The iso-frequency map was prepared by using natural neighbour interpolation algorithm. For soil-structure resonance assessment we considered large building stock from different Slovenian towns, because the building typology is similar in wider area. Low-rise masonry family houses with two or three floors prev ail. By microtremor measurements inside 45 such buildings their fundamental longitudinal and transver se frequencies were determined and statistically analysed in a complementary study. To assess the possible occurrence of soil-structure resonance in general, the average fundamental frequency +/- one standard devia tion interval is obtained for these two building heights, which give s the range 5.6-11.1 Hz. The free-field microtremor data shows that this frequency range occupies 37% of the urban area in the Litija basin. This study has shown that soil-structure resonance issue for low-rise buildings is frequently overlooked, but should be considere d seriously in shallow sedimentary basins, characterized by relatively high free-field frequencies, because many towns are located in such geological environment., a2_Second application of the derived iso-frequency map is to support soil classification, because recent investigations have shown that fundamental frequency of sediments can be used together with the average shear velocity in the upper 30 m to improve classi fications according to di fferent seismic codes., Andrej Gosar., and Obsahuje bibliografické odkazy
We estimated the common seasonal signal (annual oscillation) included in the Global Positioning System (GPS) vertical position time series by using Multichannel Singular Spectrum Analysis (MSSA). We employed time series from 24 International GNSS Service (IGS) stations located in Europe which contributed to the newest ITRF 2014 (International Terrestrial Reference Frame). The MSSA method has an advantage over the traditional modelling of seasonal signals by the Least-Squares Estimation (LSE) and Singular Spectrum Analysis (SSA) approaches because it can extract time-varying and common seasonal oscillations for stations located in the considered area. Having estimated the annual curve with LSE, we may make a misfit of 3 mm when a peak-to-peak variations of seasonal si gnals are to be estimated due to the time-variability of seasonal signal. A variance of data modelled as annual signal with SSA and MSSA differs of 3 % at average what proves that the MSSA-curves contain only time-varying and common seasonal signal and leave the station-specific part, local phenomena and power-law noise intact. In contrast to MSSA, these effects are modelled by SSA. The differences in spectral indices of power-law noise between MSSA and LSE esti mated with Maximum Likelihood Estimation (MLE) are closer to zero than the ones between SSA and LSE, which means that MSSA curves do not contain site-specific noise as much as the SSA curves do., Marta Gruszczynska, Anna Klos, Severine Rosat and Janusz Bogusz., and Obsahuje bibliografické odkazy
The article deals with geodynamical phenomena of marginal parts of sandstone plateaus. The area of interest consists of several partial areas in the Bohemian Paradise natural reserve. These areas rise above terrain as relics of a once uniform sandstone plateau. The current relief developed mainly in the Pleistocene, when the Jizera River carved present day wide valley and the underlying soft clay rocks were uncovered. Thus favorable conditions were created for slow destruction of sandstone plateaus. Here, the slope movements occur up to the present days in the form of landsliding and slow block movements and their epiphenomena. Due to this continuing activity of the slope movements, human settlements and cultural monuments are endangered. Research in this area helps us to clarify the relation between slope movements and other factors, such as the presence of a significant tectonic failure in the vicinity or the influence of the water regime., Ingrid Forczek., and Obsahuje bibliografii