An earthquake of magnitude M = 4.4, macroseismic intensity Io = 7 in the EMS scale, followed by a long series of aftershocks occurred on November 30, 2004 in southern margin of the Orawa-Nowy Targ Basin, Western Carpathians. Macroseismic epicentral data were determined for the main earthquake and the strongest aftershocks. The foci were shallow, less than 5 km i.e., originated in the Podhale Flysch. An array of seismic stations located in this seismically active area is necessary for better recognizing of the ongoing tectonic process., Barbara Guterch., and Obsahuje bibliografii
Various geotechnical tasks require the knowledge of rock properties, e.g., of elastic moduli, fracture systems, inhomogeneities, etc. Seismic measurements usually provide these parameters. To describe the detailed properties of small rock volumes, it is necessary to use high-frequency signals and suitable registration systems. Seismic measurements are carried out directly on rock surfaces. Although the conditions, under which measuremen ts are carried out, seem to be simple and convenient, practical measurements themselves are often complicated. The various measuring systems, including seismic sources and seismic receivers used for different base lengths, are discussed in this paper. It was found that, for the repeatability of measurements, the fixing of the sensors with plaster plays most significant role. Repeatability of hammer blow as seismic source is adversely affected namely by signal amplitude triggering. Pencil lead breaking tests with lead 1 and 6 mm in diameter were found as suitable for testing of the hi gh-frequency measuring systems. Measuring directly on the rock massif surface is different compared to exploration seismic measurements. Due to absence of a low-velocity layer it necessary to use a special choice of mutual orientation of sources and receivers. Polarization analysis may be advantageous to identify the arrival of P and S seismic waves. It was also found that the rock massif behaves as a narrow frequency-b and pass filter. For exciting frequencies of 0.1 and 1 MHz the transmitted signal displayed the same frequency of 25 kHz at a distance of 1.1 m., Jan Vilhelm, Vladimír Rudajev, Roman Živor and Tomáš Lokajíček., and Obsahuje bibliografické odkazy
The motion of GPS permanent stations during three earthquakes has been investigated with the use of Precise Point Positioning (PPP) technique and the seismological data. The study examines the ability of high-rate GPS observations to reflect the ground motion retrieved by the strong motion instruments (SM), considered to be more reliable and precise. The goal of this article is to show the sensitivity of GPS PPP kinematic high-rate positioning with position domain filtering using the band-pass Butterworth filter on small samples of position time series. The kinematic PPP approach in RTKLib software was used, supported by the CODE precise orbit and clock products to estimate positions from 5-hour long GPS phase datasets. Obtained position time series were reduced to 5-minute samples covering the time of co-seismic motion. The application of Butterworth band-pass filtering of GPS and seismological time series increased the agreement between them up to 72 % in terms of correlation, resulting in correlations within the range 0.34 to 0.99. The comparison of peak ground displacements (PGD) revealed that for Italian events, GPS–SM absolute value of the average difference is 6 mm with GPS–SM distances within the range of 0.05 to 2.14 km. In all analysed earthquakes, the agreement between GPSgrams and seismograms in terms of the first P-arrival polarity was checked and it was found that it is consistent in all cases. This confirms the GNSS technique capability for determining fault plane solution for earthquakes with magnitudes over 6.
Since 1982, several study programs were in itiated for monitoring seismicity, unde rground water behavior and recent crustal movements. The main characteristics of the seismic activity and the seismotectonics of the Aswan region are investigated based on the recently recorded seismic activity from 1982 to 2010 and the geodetic results. The results from these data sets are compared and combined in order to determine the main characteristics of deformation and hazard estimation in the Aswan region. GPS observations are being carried out by Aswan ge odetic network twice a year since 1997 and still until now. Analysis of the repeated 10-years GPS campaigns from the network revealed horizont al movements at the level of 7 - 10 mm/a. The estimated strain rate tensors show compression and tension components in the directions WNW-ESE and NNE- SSW which consistent with the P- and T-axes derived from ear thquake fault plane solutions, respectively. The network are a has been suffered from post-seismic deformation during the present interval; hence an increase in the general earthquake activity in the area could be expected., Mohamed S. Abdel-Monem, Haggag H. Mohamed, Mohamed Saleh and Nadia Abou-Aly., and Obsahuje bibliografické odkazy
For the last decade the Egyptian government has planned to implement the Tushka project at the southeastern part of the western Desert. This project includes the construction of a number of new cities. Tushka New City is one of these cities. Tushka area has a complex tectonic and geological history. Although no historical earthquakes are known to have occurred in the Tushka area, five large earthquakes of magnitude between 5.1 and 6.2 were recently observed from four active zones located around Tushka area. In addition to these four zones many microearthquakes have been detected in and around Tushak area. The main purpose of this research is to elucidate the seismicity and estimate the seismic hazard due to this activity in the study area. According to the spatial distribution of earthquakes that located in and around the study area, 9 seismic zones are defined on the seismotectonic map. For each seismic zone the seismic hazard parameters are estimated and used as input data for seismic hazard analysis. The resulting probability distributions are taken to produce iso-acceleration map for specific periods and economic life of public structures. The hazard at the proposed Tushka New City site is given by the hazard curve that is represented by the relationship between the peak ground acceleration and its annual exceedance probability. The maximum peak ground acceleration is 49, 137, 157 and 177 cm/s2 (gal) for zones Z-1, Z-6, Z-9 and Z-4 respectively. Although the values of PGA in zones Z-4, Z-6 and Z-9 are almost the same, Z-4 has a significant effect on the proposed Tushka New City site due to its location about 140 km northeast to the study area, while the calculated maximum acceleration with 90 percent probability of not being exceeded in 50 years of exposure time (475 years return period) at the proposed Tushka New City site was about 22 cm/s2., Raafat E. Fat-Helbary, Hussein M. El Khashab, Dragi Dojcinovski, Karrar O. El Faragawy and Abdel-nasser M. Abdel-Motaal., and Obsahuje bibliografii
Local seismicity of the Hronov-Poříčí Fault Zone is studied using two-year continuous seismic data from four seismic stations in the area. Newly developed software for automatic seismic events detection is introduced - it is based on the method used at the Icelandic seismic network. Twelve major local earthquakes are detected, localized and their magnitudes are estimated. Simultaneously, groundwater levels are continuously monitored in three wells in the area. Multiple-filtering method, originally used for processing of broadband and dispersed seismic signals, is modified and used for the frequency-time analysis of the water level data. Dominant tidal influence on the groundwater level variations is shown. Theoretical tidal potential for all three well locations is computed. Groundwater data and tidal potential are bandpass filtered to focus on the semidiurnal periods. Mutual amplitude ratio and phase shift between both quantities are computed. Each of the three wells exhibits different pattern of the groundwater level variations with respect to tides. A distinct change in the phase shift is observed at the VS-3 well in the second half of 2009. In the same time span, increased seismic activity is also observed. However, other two wells do not exhibit any evidence of such phase shift. Detailed groundwater level data analysis does not prove any significant rises or drops of the groundwater levels in 28 day intervals around the detected local events. In contras t, unexplained groundwater level drop in the V-34 well is obser ved 18 hours before the teleseismic Tohoku earthquake, Japan, March 11, 2011, Mw = 9.0., Petr Kolínský, Jan Valenta and Renata Gaždová., and Obsahuje bibliografické odkazy
Bosnia’s seismotectonics seems to follow the Mediterranean marine regime. Earthquakes occur mostly in the outer Dinaric Alps (southern Bosnia), while the strongest earthquakes occur within the Sarajevo Fault system in southern and northwestern Bosnia. In addition to active tectonics being strong, crustal earthquakes occur often as well. Due to Bosnia’s rich hydrogeology, crustal loading such as by snow and rain, or reservoir inundation, represents the most important secondary seismogenic source in the region. Despite its exquisite and active geomorphology no comprehensive and reliable geodynamical studies exist on the region. Seismic sensors coverage is extremely poor also. One centenary analogue, and a few recently installed digital seismometers are insufficient for a region that exhibits mild-to-high seismic activity. Significant investments are needed in order for GPS, seismic and other sensor-instrumented networks to be put in place or enhanced. Technical personnel needs to be educated to enable support provide for studies that are done within broader scientific activities. Such efforts that presently seek to include Bosnia under their scope are ESF-COST Action 625, NATO Stability Pact DPPI program, and EUREF/CERGOP geophysics projects., Mensur Omerbashich and Galiba Sijarić., and Obsahuje bibliografii