High-quality and open-access seismic data are of great importance for both research and increasing public awareness of actual seismic hazards and risks. We present four seismic networks that currently operate in Poland: the backbone Polish Seismological Network (PLSN), which monitors natural teleseismic events as well as regional events from Poland, and three networks that mainly serve the monitoring of anthropogenic seismicity. The acquired data from all four networks are openly available through the European Plate Observing System (EPOS) Information Technology (IT) facilities: the PLSN data within the Observatories and Research Facilities for European Seismology–European Integrated Data Archive and the anthropogenic seismicity data episodes through the induced seismicity-EPOS platform of EPOS Thematic Core Service Anthropogenic Hazards. For each network, we describe briefly the recorded seismic activity, the equipment and composition of the network, the acquisition system, and the data availability. Information from recent studies is used to demonstrate the scientific potential of the acquired anthropogenic seismicity data.
In the study, a comparison between the results of seismic profiling and the active seismoacoustic method WAS-96/RMS has been presented. The methods were used to assess the impact of an overlying coal seam edge on the relative stress state of the test heading in the chosen hard coal mine in the Upper Silesian Coal Basin, Poland. The work presents the methodologies of measurement, processing and interpretation of both methods. In the research area there were two edges of the adjacent seams at vertical distances of 70 and 100 m. The obtained results allowed for the development of conclusions regarding the effectiveness of both methods. It was stated, that the seismic profiling method, as well as the WAS-96/RMS method allowed for the identification of anomalies in the area of impact of the overlying coal seams. Based on previous experience, a comparison of the advantages and limitations of the seismic profiling and the WAS- 96/RMS method has also been presented. As a result, it was found that seismic profiling should be the basic method for assessing the impact of the edges and remnants of exploited seams, whereas the WAS-96/RMS method may be used as a complementary method if a confirmation of the rockbursts threat is required.
Summary We have modified a method for estimation of location errors distribution for local seismic networks in area with intense shallow seismicity. We have used the variance-covariance matrices in a regular grid of points. The travel time residuals variance is calculated as a function of source-receiver distance, while the new idea is to estimate the detection range of seismic stations on the basis of the probability of detection plots. In consequence, the method enables the evaluation of the applied velocity models during the analysis of travel time residuals, as well as evaluation of the usefulness of individual stations with the use of probability plots. Ultimately, it provides assessment of the station configuration by analyzing the distribution of location errors. The data needed for the analysis are a seismic catalog containing earthquakes locations together with travel time residuals and the velocity model, as well as stations metadata. The method is tested on using the real data which come from the LUMINEOS local seismic network, the network used for induced seismicity monitoring in the Legnica-Głogow Copper District in Poland.
<p>Estimation of hypocenter location errors&#160; is not a simple task. These errors are influenced by many factors. The most important are: the quality of velocity model, the configuration of stations in the observation network and the noise level recorded at stations. While the network configuration affects the error distribution in a deterministic manner, the noise level is largely random. It means that the uncertainties cannot be determined in a deterministic way and only statistical approach can be used. There are several methods for estimating location errors for particular seismic network. Some techniques use synthetic seismograms to calculate the detection range related to each station. However, this approach requires very precise knowledge of the geological model, which is not always possible. Instead, in this work we present a different approach, which uses only phase data for events included in the catalog. In this method, the detection range for each station is estimated using the detection probability (Schorlemmer & Woessner, 2008) used for both P- and S- waves first arrivals. The usefulness of this approach is discussed assuming the shape of&#160; LUMINEOS seismic network which operates in the Legnica-G&#322;og&#243;w Copper District (LGCD), Poland. In the LGCD region seismic activity is related to three deep underground copper mines. Every year thousand of seismic events with magnitudes up to M4.0 are registered here. Some of them are followed by tragic mining collapses and are widely felt by local residents.</p>
In this work, the results of four seismic tomography surveys are presented. The research was conducted to identify the zones exposed to the threat of gas and rock outburst. The changes to the dolomite layer stiffness in the mining excavation roofs were analyzed. The surveys were conducted in the Rudna copper ore mine in the field of XXVIII/1. The research area was about 0.21 km2. The seismic waves were generated by a small amount of explosive material (100 - 300 g) located and installed in short blast holes (1.5 - 2.0 m). The processing and the interpretation of the measurement data did not cause serious problems due to the more favourable elastic properties of the dolomite layer compared to the adjacent anhydrite and sandstone layers. As a result, the maps of parameters like the longitudinal wave velocity (P-wave), the shear wave velocity (S-wave), and the ratio of the Pwave velocity to S-wave velocity and the dynamic Young modulus were estimated. The results showed that the changes in the seismic parameters were relatively small over most of the research area. This may be evidence of the minor effects of gas and rock outbursts.
In the study, the determining of the reference velocity of the P-wave in coal seams used in seismic profiling to assess increases and decreases in relative stresses at large depths has been presented. The seismic profiling method proposed by Dubinski in 1989 covers a range of depth up to 970 m. At present, coal seams exploitation in Polish coal mines is conducted at greater depths, even exceeding 1200 m, which creates the necessity for a new reference velocity model. The study presents an empirical mathematical model of the change of the P-wave velocity in coal seams in the geological conditions of the Jastrzebie coal mine. A power model analogous to the Dubinski’s one was elaborated with new constants. The calculations included the results from 35 measurements of seismic profiling carried out in various coal seams of the Jastrzebie mine at depths from 640 to 1200 m. The results obtained cause changes in the result of calculations of seismic anomalies. Future validation of the proposed model with larger data set will be required.
Legnica-Głogów Copper District (LGCD) is one of the most active seismic regions in Europe. Several thousand seismic events induced by underground copper mines are recorded there each year, with the strongest reaching magnitudes above 4. Seismicity in LGCD is monitored by the LUMINEOS surface seismic network and the mine's underground networks. While the horizontal location uncertainty of the LUMINEOS network is about 300–600 m, the declared epicenter uncertainty of dense mine networks is less than 50 m. It gives us a unique opportunity to test the location accuracy of seismic events recorded by the LUMINEOS network determined with various algorithms and automatic procedure. In our work, we compared the location accuracies of traveltime-based algorithms LocSAT and NonLinLoc as well as waveform-based algorithm BackTrackBB. The iterative, Geiger-type LocSAT algorithm is used in routine daily processing for the LUMINEOS. Its downside is the need to use the S wave onset times, which in the case of the LUMINEOS network are very uncertain. As an alternative, we tested the probabilistic NonLinLoc algorithm, and the waveform based BackTrackBB algorithm. The BackTrackBB algorithm is known to work well with local, high noise seismic networks. We aimed to find out if it could be used routinely with the LUMINEOS data. In addition, we conducted a comparative analysis of the location uncertainty of these algorithms to determine the effectiveness of this parameter in assessing accuracy.
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