The research in question deals with problems of determining seismic P- and S-wave velocities for purposes of computing the elastic constants of a rock massif. This experimental study indicates various ways of measurement and its processing for different geological conditions. The experimental measurements were carried out on the surface of the studied rock massif, on the walls in workings, as well as on the surface in a quarry. The question of seismic pick-ups, geophones or piezo-electric transducers and the number of components required to identify P- and S-waves, is discussed. This is considered in connection with the choice and properties of the impact or piezo-electric seismic source. The result is a number of generalizing recommendations with respect to the measuring technique, inclusive of its use for determining the directional dependence of the elastic moduli., Roman Živor, Jan Vilhelm, Vladimír Rudajev and Tomáš Lokajíček., and Obsahuje bibliografii
The paper deals with a new criterion of evaluating the disintegration by blasting operations using cylindrical as well as concentrated charges in quarries and undergrounds. The results of our research show that for seismic safety determination of blasting, the maximum of concentrated charge blasting in one delay stage is not critical, but decisive is the explosion of the total mass of blasting material., Blažej Pandula and Kamila Jelšovská., and Obsahuje bibliografické odkazy
The Precise Point Positioning (PPP) analysis technique adapted for monitoring of moderate high-rate coordinate variations from GPS observations is applied for measuring actual displacements related to earthquakes. Two approaches are examined: kinematic PPP which is suitable for larger displacements and analysis of residuals from quasi-static PPP which is suitable for detection of minor displacements. Results from simulated horizontal movements of GPS antenna as well as analyses of 1 Hz GPS data from M 9.0 Sendai earthquake, M 6.3 L’Aquila earthquake and M 4.3 Tatabanya earthquake are shown. Our experiments proved the ability to measure dynamic seismic-related short-term coordinate variations at sub-centimetre level with PPP and to detect both strong and weak seismic signals using GPS satellites observations., Ján Hefty and Ľubomíra Gerhátová., and Obsahuje bibliografické odkazy
Distributed control and measurement system for evaluation of hydrologic, geomechanical and other parameters has been built up in the medieval ore mine Jeroným. The instrumentation is generally based on commercial measurement and control kit and sensors. Technique of implementation of special sensors, e.g. laser distance meter and/or CCBM probe for measurement of rock massif stress changes, is also described. The distributed system is integrated into the existing seis mic recording station equipped by data transmission via GSM network. Comprehensive monitoring system is modular in order to have possibility to change the system configuration., Jaromír Knejzlík and Zdeněk Rambouský., and Obsahuje bibliografické odkazy
In the article the results of registering seismic events located under mining coal seam are presented. Such mining tremors have occurred in several Polish mines. The geological and mining conditions affecting the induction of that type of seismic events are shown. The mechanisms of deep seismic events (more than 1000m) triggered by mining are discussed in relation to regional geology. The most deep mining seismic events in Upper Silesia were related to regional geological structures focusing stress (e.g. syncline) or tectonic structures (younger faults), where mining stresses were only additional factor to trigger strong regional seismic events. The tremors were characterized by a shear mechanism in the source (double-couple forces). Tremors located directly under the performed operation, usually characterized by an uniaxial tension mechanism, associated with the regional tension axis and the space created during the operation of the coal seam, causing pushing loaded rock-mass into new gobs. Proposed methods of seismic monitoring for case of seismic events location under mining coal seam are discussed., Grzegorz Mutke., and Obsahuje bibliografii
The application of the double-difference ( DD) algorithm to the relocation of induced seismic events from the Upper Silesian Coal Basin is discussed. The method has been enhanced by combining it with the Monte Carlo sampling technique in order to evaluate relocation errors. Results of both synthetic tests and relocation of real events are shown. They are compared with estimates of the classical single-event (SE) appr oach obtained through the Monte Carlo sampling of the a posteriori probability. On the basis of this comparis on we have concluded that the double-difference approach yields better estimates of depth than the classical location technique., Łukasz Rudziński and Wojciech Dębski., and Obsahuje bibliografické odkazy
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
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