Grzegorz Lizurek

Mining Induced Seismic Event on an Inactive Fault

On 19 March 2013, a tremor shook the surface of Polkowice town where the Rudna Mine is located. This event, of ML = 4.2, was the third most powerful seismic event recorded in the Legnica Głogów Copper District (LGCD). Inhabitants of the area reported that the felt tremor was bigger and lasted longer than any other ones felt in the last couple of years. Analysis of spectral parameters of the records from in-mine seismic system and surface LUMINEOS network along with broadband station KSP record were carried out. The location of the event was close to the Rudna Główna Fault zone; the nodal planes orientations determined with two different approaches were almost parallel to the strike of the fault. The mechanism solutions were also obtained as Full Moment Tensor from P-wave amplitude pulses of underground records and waveform inversion of surface network seismograms. The results from the seismic analysis along with macroseismic survey and observed effects from the destroyed part of the mining panel indicate that the mechanism of the event was complex rupture initiated as thrust faulting on an inactive tectonic normal fault zone. The results confirm that the fault zones are the areas of higher risk, even in case of carefully taken mining operations.

Complex Rupture Process of the 19 March 2013, Rudna Mine (Poland) Induced Seismic Event and Collapse in the Light of Local and Regional Moment Tensor Inversion

On 19 March 2013, a strong, shallow, induced seismic event struck a mining panel in the room‐and‐pillar Rudna copper mine in southeastern Poland. The event caused important damage at the mining tunnel and trapped 19 miners, who were safely rescued a few hours later. Although mining‐induced seismicity is frequent at this mine, the 19 March event was unusual because of its larger magnitude, its occurrence far from the mining stopes, and because it was accompanied by a strong hazardous rockburst. The mining inspections following the event verified the occurrence of a rockfall with tunnel floor uplift but also recognized the presence of a faulting structure at the hypocentral location. The availability of three monitoring networks (including local and regional data, short‐period and broadband seismometers, and surface and in‐mine installation) presented an optimal setup to determine rupture parameters and to compare the performance and results from different installations. We performed waveform and spectral‐based analysis to infer source properties, with a particular interest to the determination of the rupture processes, using different moment tensor (MT) inversion techniques. Our results are surprisingly different, ranging from a dominant thrust mechanism, resolved at closest distances, to a collapse‐type rupture, resolved at regional distances. We demonstrate that a complex rupture model is needed to explain all observations and to justify these discrepancies. The final scenario indicates that the rupture nucleated as a weaker thrust mechanism along a pre‐existing weakened surface and then continued in a more energetic collapse event. The local LUMINEOS surface network has the potential to resolve both subevents but not using a standard MT decomposition. Here, we propose a new MT decomposition and an alternative MT fitting procedure that can be used to analyze the MT of collapse sources.

Moment Tensor Solution and Physical Parameters of Selected Recent Seismic Events at Rudna Copper Mine

The Lubin Copper Basin is a source of induced seismic events of considerable size. The paper presents the source mechanism study of fifty seismic events from Rudna Copper Mine that occurred in 2007. The energies of studied seismic events were greater than 105 J. Focal mechanisms for those events have been calculated with seismic moment tensor inversion method using FOCI computer software. The calculations were made using L1 and L2 norms. Final results are presented for L1 norm due to its lower sensitivity to possible errors. Spectral analysis of P and S waves was also performed. The analysis shows that typical focal radius is of about 200 m.

Seismic event near Jarocin (Poland)

The earthquake of magnitude ML = 3:8 (EMSC) took place on Friday, 6 January 2012, north-east of the town of Jarocin in Wielkopolska Region, Poland. The only historical information about past earthquakes in the region was found in the diary from 1824; apart of it, there was a seismic event noticed in the vicinity of Wielkopolska in 1606 (Pagaczewski 1982). The scope of this paper is to describe the 6 January 2012 event in view of instrumental seismology, macroseismic data analysis and known tectonics of the region, which should be useful in future seismic hazard analysis of Poland.

Preliminary Results of Anthropogenic Seismicity Monitoring in the Region of Song Tranh 2 Reservoir, Central Vietnam

Song Tranh 2 hydropower plant and the reservoir containing backed up water are located in the Quang Nam province (Central Vietnam). The region experiences unusual seismic activity related to the reservoir impoundment, with earthquakes of magnitude up to 4.7. In result of cooperation between the Institute of Geophysics, Vietnam Academy of Sciences and Technology and the Institute of Geophysics, Polish Academy of Sciences a seismic network has been built to facilitate seismic monitoring of the Song Tranh 2 area. The network, operating since August 2013, consists of 10 seismic stations. Here we show that the network is sufficient for advanced data processing. The first results of monitoring of the earthquake activity in Song Tranh 2 area in the period between 2012 and 2014, especially the completeness of catalogs, study and comparisons between water level and the seismic activity suggest direct connection between reservoir exploitation and anthropogenic seismicity.

Time-dependent seismic hazard in Bobrek coal mine, Poland, assuming different magnitude distribution estimations

The purpose of this study is to evaluate seismic hazard parameters in connection with the evolution of mining operations and seismic activity. The time-dependent hazard parameters to be estimated are activity rate, Gutenberg–Richter b-value, mean return period and exceedance probability of a prescribed magnitude for selected time windows related with the advance of the mining front. Four magnitude distribution estimation methods are applied and the results obtained from each one are compared with each other. Those approaches are maximum likelihood using the unbounded and upper bounded Gutenberg–Richter law and the non-parametric unbounded and non-parametric upper-bounded kernel estimation of magnitude distribution. The method is applied for seismicity occurred in the longwall mining of panel 3 in coal seam 503 in Bobrek colliery in Upper Silesia Coal Basin, Poland, during 2009–2010. Applications are performed in the recently established Web-Platform for Anthropogenic Seismicity Research, available at https://tcs.ah-epos.eu/.

Clustering of mining-induced seismic events in equivalent dimension spaces

High energy release during seismic events induced by mining operation is one of the major dangers perturbing production in underground mines. In this work, temporal changes of seismic event parameters for one of the Rudna Mine (Poland) panels are investigated. The study aim was to find whether the temporal clustering of smaller events in different parameters can be observed before and after the high energy events (Ml ≥ 3) in the mining panel. The method chosen for analysis was the study of temporal variation of fractal dimension of the seismic events parameter sets composed from: the interevent epicentral distance (dr), logarithm of seismic energy (lE), and interevent energy coefficient (dlE), which is the absolute difference between logarithms of energy of two consecutive events. Temporal variations study was performed in equivalent dimension (ED) space. The transformation of the seismic source parameters into ED space allowed to estimate and compare the temporal changes of the fractal dimension of different parameter spaces using the same method—correlation fractal dimension, and then easily compare the obtained temporal changes of fractal dimension of different parameter sets. The effect of grouping is expressed by decrease of fractal dimension, which is connected with the similarity of events parameter values. The temporal changes of the fractal dimension of seismicity before the strong induced events would indicate some initiation phase of the process leading to the high energy release. In the case of the studied Rudna Mine panel, the temporal behavior of the fractal dimension values in different parameter spaces before seismic events showed significant changes before three out of four events with CLVD dominant source mechanisms.

Full Moment Tensor Inversion as a Practical Tool in Case of Discrimination of Tectonic and Anthropogenic Seismicity in Poland

Tectonic seismicity in Poland is sparse. The biggest event was located near Myślenice in 17th century of magnitude 5.6. On the other hand, the anthropogenic seismicity is one of the highest in Europe related, for example, to underground mining in Upper Silesian Coal Basin (USCB) and Legnica Głogów Copper District (LGCD), open pit mining in “Bełchatów” brown coal mine and reservoir impoundment of Czorsztyn artificial lake. The level of seismic activity in these areas varies from tens to thousands of events per year. Focal mechanism and full moment tensor (MT) decomposition allow for deeper understanding of the seismogenic process leading to tectonic, induced, and triggered seismic events. The non-DC components of moment tensors are considered as an indicator of the induced seismicity. In this work, the MT inversion and decomposition is proved to be a robust tool for unveiling collapse-type events as well as the other induced events in Polish underground mining areas. The robustness and limitations of the presented method is exemplified by synthetic tests and by analyzing weak tectonic earthquakes. The spurious non-DC components of full MT solutions due to the noise and poor focal coverage are discussed. The results of the MT inversions of the human-related and tectonic earthquakes from Poland indicate this method as a useful part of the tectonic and anthropogenic seismicity discrimination workflow.

Clustering and Stress Inversion in the Song Tranh 2 Reservoir, VietnamClustering and Stress Inversion in the Song Tranh 2 Reservoir, Vietnam

The seismicity in the vicinity of the Song Tranh 2 reservoir that commenced in late 2010 is an example of reservoir‐induced seismicity. Moment tensor (MT) solutions are mostly normal‐faulting mechanisms with shearing as the main component of full MT, which suggest reservoir exploitation stress field changes as a triggering origin of this seismicity. However, the local tectonic stress field plays a role in the seismogenic process, which is accelerated by the reservoir exploitation. Two main orientations of discontinuities reactivated by reservoir exploitation are identified, with clustering of events located in two main areas: northern and southern. In addition to the northern cluster (NC) and southern cluster (SC), further smaller clusters are distinguishable, assuming both clustering of epicenters and similarity of focal mechanisms as the clustering criteria. Maximum seismic activities in clusters appear in different periods, with high seismicity in the SC preceding that in the NC. The results indicate significant differences between the NC and SC. It is shown that the SC is an example of rapid triggering, whereas the NC is a delayed triggering type. Also, magnitude distribution differs between the NC ( b≈1.1b≈1.1 ) and SC ( b≈1.3b≈1.3 ).

IS-EPOS: a platform for anthropogenic seismicity research

Research in the field of anthropogenic seismicity (AS) requires not only seismicity data but also data regarding the progress of the technological/production activities which is the origin of the induced or triggered seismic events. Such data are typically restricted and proprietary, and therefore, usually not available for independent researchers who wish to develop, perform and verify scientific research. The induced seismicity-European plate observing system (IS-EPOS) web portal offers to its user’s access to data, applications and documents in order to facilitate AS research. IS-EPOS web portal has been designed to serve as one of the main pillars of the Thematic Core Service—-Anthropogenic Hazards belonging to pan-European multidisciplinary research infrastructure created within the EPOS program. IS-EPOS platform is open for research community and general public according to its rules of access. The platform is operating since January 2016 and is now integrated in the EPOS Integrated Core Services. IS-EPOS e-platform promotes new opportunities to study and comprehend the dynamic and complex solid earth system by integrating the use of multidisciplinary data, data products, analysis models and online applications. The integration of existing and new national and transnational Research Infrastructures increases the access and use of multidisciplinary data recorded by the solid earth observing systems, acquired in laboratory experiments and/or produced by computational simulations. In this paper, we describe the structure and the main innovative characteristics implemented in IS-EPOS. The platform is open to accommodate data integrated within other research projects, and it is continuously being updated with improvements in existing features and implementations of new ones. An appendix at the end of the article provides a summary of acronyms and abbreviations in order to make the reader familiar with the terms used throughout the manuscript.