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1

Identification of strong tremor causes for appropriate rock burst prevention in a hard coal mine

Pakosz Rafał, Wojtecki Łukasz, Mendecki Maciej J., Krzyżanowska Agnieszka

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 2

132--146

EN

The exploitation carried out in the Bielszowice part of the Ruda Hard Coal Mine is mainly accompanied by seismic and rock burst hazards. The occurrence of high-energy tremors may be associated with many factors, e.g., fracturing of thick layers of high-strength rocks or destruction processes of a stressed and/or thick coal seam. These factors are often combined when excavating a single longwall panel. Determining the causes of strong tremors is of fundamental importance for mining and rock burst prevention. The extraction of the 004z longwall panel in the top layer of coal seam No. 504 was designed in complex geological and mining conditions. During the mining of the 004z longwall panel, strong tremors with energies of 105 J and 106 J occurred. The analysis of the focal mechanisms of these tremors using the seismic moment tensor inversion method allowed to determine the most probable causes of their occurrence. They were mainly related to the processes of fracture and slip in the thick layers of sandstone deposited in the direct or main roof of coal seam No. 504. Therefore, active rock burst prevention was aimed mainly at fracturing high-strength roof rocks.

2

Development of an empirical ground-motion model for postmining induced seismicity near Gardanne, France

Gehl Pierre, Dominique Pascal, Aochi Hideo, Delatre Mickael, Kinscher Jannes, Contrucci Isabelle

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 2

98--117

EN

Since the closure of mining activities in 2003, the coal basin of Gardanne in South-East France has experienced thousands of small-magnitude earthquake events, mostly triggered by the flooding of mine workings. Some of these events have been powerful enough to be strongly felt by the population, generating nuisance and concern about potential damage to buildings. The aim of this study is to improve the characterisation of the level of ground motion at the surface, by developing a ground-motion model for post-mining induced seismicity, based on several years of recorded data. A Bayesian-based method is applied to the data in order to account for uncertainties in the estimation of moment magnitude. Station-to-station ground-motion site terms are also quantified for the nine recording stations in the area, thus providing additional information on the local site conditions. The developed model is compared to existing prediction equations for seismicity induced by other types of anthropic activities, confirming the need for a specific model in the case of post-mining induced seismicity. Finally, the Gardanne ground-motion model is also integrated with a shake-map procedure, showing how this predictive model may be merged with recorded data in order to generate rapid estimates of shaking levels in the area.

3

The effects of component rotation on H/V spectra: a comparison of rotational and translational data

Nawrocki Dariusz, Mendecki Maciej J., Teper Lesław

Geology, Geophysics and Environment

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2024

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Vol. 50, no. 2

145--154

EN

The presented investigation focused on site effect estimations, specifically resonance frequency and amplification. These estimations were carried out for both rotational and translational signals, using waveforms from mining-induced seismic events. Site effect parameters were calculated using the horizontal-to-vertical spectral ratio (HVSR) technique, which is commonly applied to translational records by comparing the spectral ratio between horizontal and vertical components. In this study, we also applied the horizontal-to-vertical (H/V) ratio to rotational records. However, due to the different orientations of motion propagation, we introduced the spectral H/V ratio for rotational motion as the torsion-to-rocking spectral ratio (TRSR). Furthermore, we analyzed these signals according to two approaches. First, we estimated the site effect parameters for directly registered signals, and secondly, we considered rotated components by varying the angle from 0° to 180° in 5-degree increments. Generally, the H/V curves indicated two peaks for translational motions and four peaks for rotational motions. The averaged H/V spectra and spectra obtained for different angles of component rotation showed insignificant fluctuation in amplification values for both rotational and translational motions. However, when comparing each component’s spectrum for all angles, we observed changes in the site effect parameter values for both motion types. Radar plots depicting amplification values versus rotation angles for separated components revealed characteristic fluctuations, suggesting local anisotropy. Moreover, when comparing the radar plots between rotational and translational results, it was evident that rotational resonance frequencies shifted to higher frequency values, potentially indicating shallower geological layers as their source.

4

Novel approach for the destress blasting in hard rock underground copper mines

Mertuszka Piotr, Szumny Marcin, Fuławka Krzysztof, Kondoł Piotr

Journal of Sustainable Mining

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2022

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Vol. 21, iss. 2

141--154

EN

The present study investigates the possibility of developing a novel method for reducing seismicity and rockbursts in deep underground mines based on modifying drilling and blasting patterns. The main goal was to develop and implement firing patterns for multi-face production blasting, which allow increasing the capability of inducing stress relief in the rock mass, manifested in the seismic event. This method may improve stability control in underground workings, and mitigate risks associated with the dynamic effects of rock mass pressure compared with currently used methods. Thus, the seismic energy may be released immediately after blasting in a controlled way. For this purpose, underground tests using modified blasting patterns and precise electronic detonators were carried out. Vibration data recorded from the multi-face blasting in the considered trial panels were assessed in the scope of amplitude distribution. Results of trials have proven that the method is promising and should be further developed to improve the effectiveness of rockburst prevention in deep hard rock mines.

5

Syntetyczne testy inwersji pełnego pola falowego w warunkach rzeczywistej sieci monitoringu sejsmicznego ZG Rudna

Caputa Alicja, Rudziński Łukasz

Przegląd Geofizyczny

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2020

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Z. 3-4

123--138

PL

Sejsmiczność indukowana działalnością górniczą jest stale monitorowana i analizowana w celu zwiększenia bezpieczeństwa wydobycia kopalin. Jedną z procedur, chociaż niestosowanych rutynowo w polskim górnictwie węgla i miedzi, jest wyznaczanie mechanizmów ogniskowych silniejszych wstrząsów. Najprostszą i jak dotąd jedyną stosowaną metodą ich obliczania jest inwersja pierwszych wstąpień fali P w domenie czasu. Metoda ta pomimo swojej prostoty i możliwości bezpośredniej kontroli analizowanego wejścia fali sejsmicznej, jest procedurą bardzo czułą na geometrię sieci pomiarowej. Jest to szczególnie kłopotliwe w przypadku dołowych sieci kopalnianych, gdzie geometria sieci ograniczona jest istniejącą infrastrukturą podziemną. W niniejszym opracowaniu proponujemy i testujemy metodę inwersji pełnego pola falowego, przeprowadzaną w domenie częstotliwości oraz czasu, która do tej pory nie była powszechnie stosowana w polskim górnictwie. W oparciu o sejsmogramy syntetyczne obliczone dla lokalnego modelu prędkościowego oraz z wykorzystaniem geometrii rzeczywistej sieci monitoringu sejsmicznego, przeprowadziliśmy badanie przydatności inwersji pełnego pola falowego do obliczeń w warunkach górniczych. W pracy prezentujemy analizy 10 różnych modeli mechanizmów ogniskowych testowanych w różnych lokalizacjach kopalni dla zmiennej siły wstrząsu oraz z dodatkowym rzeczywistym szumem sejsmicznym. Na podstawie otrzymanych wyników możemy stwierdzić, iż głównym czynnikiem warunkującym jakość rozwiązania jest siła wstrząsu i wynikająca z niego zależność amplituda/szum. Natomiast metoda ta nie jest czuła na geometrię sieci pomiarowej.

EN

In order to improve the safety procedures of georesources exploitation, the induced seismicity is constantly monitored and examined. One of the procedures method, although even though not routinely used in Polish coal and copper mining mines, is the calculation of focal mechanisms of strong seismic events. The simplest and so far the only used method for source mechanisms estimation is the inversion of the first P wave onsets in the time domain. Despite its simplicity and the ability to direct control of analyzed seismic waves used during inversion, it is a procedure very sensitive to the geometry of the monitoring seismic network. This is particularly troublesome in the case of underground seismic monitoring system, where the geometry of the network is limited by the existing underground infrastructure. In this study, we propose and test the full waveform inversion method, performed both in the frequency and time domain. This kind of method has not been widely used in Polish miningmines. Basing on synthetic seismograms prepared for the local velocity model and using geometry of the real seismic monitoring network, we conducted a study of the suitability of the full waveform inversion for calculations in underground mining conditions. In this paper, we present analyzes of 10 different source models of focal mechanisms tested in various mine locations within mining area. The tests were performed for variable events strength and with additional real seismic noise. On the grounds of obtained results, we can conclude that the main factor determining the solution quality is the strength of mining tremor and amplitude/noise relationship resulting from it. However, this method is not sensitive to the geometry of the measurement network.

6

Group winning blasting as a measure to mitigate seismic hazard in a deep copper ore mine, SW Poland

Gogolewska Anna Barbara, Kowalczyk Małgorzata

Mining Science

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2020

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Vol. 27

155--164

EN

Three deep mines have been excavating the copper ore deposit in south-west Poland for about fifty years. Rock mass tremors and their effects such as rock bursts pose the most dangerous hazard which increases with intensity and depth of exploitation. The permanent growth of seismicity of the deposit necessitated the implementation of preventive activities into mining technology. Temporary and long-term as well as active and passive methods were developed to reduce or eliminate the hazard among which group winning blasting seems to be one of the most successful preventive technique. The paper aimed to assess seismic activity and the effectiveness of active prevention as well as to verify the connection between induced seismicity of rock mass and elements of blasting works. To realize the goal, seismic activity, the number of blasted faces, the number of explosives, and blasting-induced seismicity were analyzed. Moreover, the linear correlation coefficients between the aforementioned parameters and characteristics were calculated. One mining division of the Polkowice-Sieroszowice copper ore mine was investigated over three years during a high rate of seismic hazard and intense exploitation.

7

Distribution of peak ground vibration caused by mining induced seismic events in the Upper Silesian Coal Basin in Poland

Dubiński Józef, Mutke Grzegorz, Chodacki Jacek

Archives of Mining Sciences

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2020

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Vol. 65, no. 3

419--432

EN

The solutions presented permit the practical determination of the physical parameters of peak ground vibration, caused by strong mining tremors induced by mining, in the Polish part of the Upper Silesian Coal Basin (USCB). The parameters of peak ground horizontal velocity (PGVH) and peak ground horizontal acceleration (PGAH10) at any point of earth’s surface depend on seismic energy, epicentral distance and site effect. Distribution maps of PGVH and of PGAH10 parameters were charted for the period 2010-2019. Analysis of the results obtained indicates the occurrence of zones with increased values of these parameters. Based on the Mining Seismic Instrumental Intensity Scale (MSIIS-15), which is used to assess the degree of vibration intensity caused by seismic events induced by mining, and using the PGVH parameter, it was noted that the distribution map of this parameter includes zones where there vibration velocities of both 0.04 m/s and 0.06 m/s were exceeded. Vibrations with this level of PGVH correspond to intensities in the V and VI degree according to the MSIIS-2015 scale, which means that they can already cause slight structural damage to building objects and cause equipment to fall over. Moreover, the reason why the second parameter PGAH10 is less useful for the evaluation of the intensity of mining induced vibrations is explained. The PGAH10 vibration acceleration parameter, in turn, can be used to design construction of the objects in the seismic area of the Upper Silesian Coal Basin, where the highest acceleration reached a value of 2.8 m/s2 in the period from 2010 to 2019.

8

Using ground motion prediction equations to monitor variations in quality factor due to induced seismicity: a feasibility study

Convertito Vincenzo, De Matteis Rafaella, Esposito Roberta, Capuano Paolo

Acta Geophysica

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2020

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Vol. 68, no. 3

723--735

EN

Sub-surface operations for energy production such as gas storage, fuid reinjection or hydraulic fracking may modify the physical properties of the rocks, in particular the seismic velocity and the anelastic attenuation. The aim of the present study is to investigate, through a synthetic test, the possibility of using empirical ground-motion prediction equations (GMPEs) to observe the variations in the reservoir. In the synthetic test, we reproduce the expected seismic activity (in terms of rate, focal mechanisms, stress drop and the b value of the Gutenberg-Richter) and the variation of medium properties in terms of the quality factor Q induced by a fuid injection experiment. In practice, peak-ground velocity data of the simulated earthquakes during the feld operations are used to update the coefcients of a reference GMPE in order to test whether the coefcients are able to capture the medium properties variation. The results of the test show that the coefcients of the GMPE vary during the simulated feld operations revealing their sensitivity to the variation of the anelastic attenuation. The proposed approach is suggested as a promising tool that, if confrmed by real data analysis, could be used for monitoring and interpreting induced seismicity in addition to more conventional techniques.

9

Wyznaczanie względnych współczynników amplifikacji dla wartości szczytowych przyspieszenia i prędkości drgań gruntu w oparciu o relację tłumienia w rejonie uskoku Kłodnickiego

Lurka Adam, Gierlotka Michał, Siata Robert

Przegląd Górniczy

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2019

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T. 75, nr 3

1--8

PL

Strefa uskoku Kłodnickiego jest jednym z głównych rejonów wysokiej aktywności sejsmicznej obszaru Górnośląskiego Zagłębia Węglowego. Generowane eksploatacją wstrząsy z kopalń, których obszar górniczy znajduje się w tej strefie, stanowią nie tylko zagrożenie dla podziemnych wyrobisk górniczych w kopalniach, ale są także przyczyną uszkodzeń infrastruktury powierzchniowej i uciążliwości dla mieszkańców. W rejonie uskoku Kłodnickiego od 2006 roku prowadzona jest przez jedną z kopalń węgla ciągła rejestracja drgań gruntu pochodzących od wstrząsów indukowanych działalnością górniczą przy pomocy 6 trójskładowych stanowisk sejsmometrycznych typu AMAX. W oparciu o zbiór danych sejsmometrycznych otrzymanych z rejestracji wysokoenergetycznych wstrząsów z lat 2006-2017 podjęto próbę wyznaczenia parametrów relacji tłumienia drgań sejsmicznych wraz z uwzględnieniem amplifikacji tych drgań przez przypowierzchniowe warstwy geologiczne. Amplifikacja to efekt zwiększania wartości amplitud drgań sejsmicznych rejestrowanych na powierzchni terenu, zależny od parametrów warstw przypowierzchniowych, takich jak gęstość, miąższość oraz prędkość propagacji rozpatrywanych fal sejsmicznych. Estymację współczynników amplifikacji drgań wykonano metodą regresji wielokrotnej w oparciu o model relacji tłumienia Joynera- Boore’a. Obliczenia regresyjne wykonano dla sześciu zestawów względnych współczynników amplifikacji, za każdym razem przyjmując jedno stanowisko bazowe, na którym współczynnik amplifikacji wynosił 1. Wybrano ten zestaw współczynników amplifikacji drgań, dla którego test statystyczny dawał wartości p statystyki mniejsze od 0,001 dla wszystkich współczynników regresyjnych badanego modelu tłumienia drgań.

EN

The Kłodnicki Fault Zone is one of the main areas of high seismic activity in the Upper Silesian Coal Basin. The induced mining tremors from coal mines whose mining area is located in this zone are not only a threat to underground mine workings, but are also the cause of damage to surface infrastructure and nuisance to residents. In the area of Kłodnicki fault, since 2006, one of the coal mines has been continuously monitoring ground vibrations from seismic events induced by mining activity using 6 three-component AMAX seismic stations. Based on the seismic data obtained from recordings of high- -energy tremors in the years between 2006 and 2017, an attempt was made to estimate the parameters of seismic attenuation relations, including the site amplification factors related to near-surface geological layers. Site amplification is the effect of increasing the amplitude of seismic vibrations recorded on the surface that is dependent on the parameters of the subsurface layers such as density, thickness and seismic velocity. The estimation of the site amplification factors was made by multiple regression analysis based on the Joyner-Boore attenuation model. The presented research was performed on various groups of attenuation relations and relative amplification factors assuming one of amplification factors of surface seismic stations was equal 1. Finally, the estimated site amplification factors were selected for which calculated p-values of statistical test were less than 0.001 for all coefficients of the analyzed attenuation relation.

10

Sonda do pomiaru prędkości kątowej drgań rotacyjnych w podziemnych wyrobiskach górniczych

Logiewa Hubert, Mutke Grzegorz, Lurka Adam

Przegląd Górniczy

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2019

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T. 75, nr 12

18--25

PL

W ciągu ostatniej dekady temat rotacyjnych drgań gruntu stał się istotny w zakresie badań sejsmologicznych, a szczególnie inżynierii sejsmicznej. Do tej pory nie prowadzono jednak obserwacji drgań rotacyjnych w podziemnych wyrobiskach kopalnianych, ze względu na brak odpowiednich czujników pomiarowych. W Głównym Instytucie Górnictwa opracowano prototyp sondy rotacyjnej LMLROT do pomiaru prędkości kątowej drgań gruntu w warunkach zagrożenia wybuchowego. Sonda może współpracować z systemami obserwacji sejsmologicznej SOS oraz innymi urządzeniami odbierającymi sygnały prądowe z linii transmisyjnej. Trójskładowa sejsmiczna sonda rotacyjna LMLROT umożliwia pomiar prędkości kątowej drgań w zakresie do 100 mrad/s dla częstotliwości od 2 do 200 Hz. Sonda LMLROT może być wykorzystana między innymi do badań dotyczących wpływu wstrząsów sejsmicznych na stateczność wyrobisk górniczych.

EN

Over the last decade, the subject of rotational vibrations has become important in the field of seismological research, and in particular earthquake engineering. Until now, however, no rotational vibration observations have been carried out in underground mine workings, due to the lack of appropriate measuring sensors. At the Central Mining Institute, a prototype of the LMLROT rotary probe was developed to measure the angular velocity of ground vibrations in explosive conditions. The probe can cooperate with SOS seismological observation systems and other devices receiving current signals from the transmission line. The three-component seismic LMLROT rotary probe measures angular velocity up to 100 mrad/s for frequencies from 2 to 200 Hz. The LMLROT probe can be used, inter alia, for studies on the impact of mining seismic quakes on the stability of mining excavations.

11

Badania przemieszczeń powierzchni spowodowanych wstrząsami górniczymi z zastosowaniem satelitarnej interferometrii radarowej na przykładzie LGOM

Owczarz Katarzyna, Blachowski Jan

Przegląd Górniczy

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2019

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T. 75, nr 1

53--61

PL

W artykule przedstawiono wyniki obliczeń metodą satelitarnej interferometrii różnicowej (DInSAR) wykonanych dla trzech wstrząsów indukowanych, które wystąpiły na terenach górniczych LGOM. Wybrane do analiz zdarzenia miały magnitudy: 4.8, 4.5 oraz 3.9 i wystąpiły odpowiednio: 26.12.2017 r., 20.07.2018 r. oraz 12.08.2018 r. Do określania potencjalnych zmian na powierzchni w wyniku tych wstrząsów wykorzystano zobrazowania SAR zarejestrowane przez satelity Sentinel-1A i Sentinel-1B bezpośrednio przed i po wystąpieniu wstrząsów. Wyznaczono koherencję, opracowano interferogramy, a następnie wyznaczono przemieszczenia powierzchni w linii widoczności satelity (LOS). Dla wstrząsu o magnitudzie 4.8 obniżenia pionowe (LOS) wyniosły ponad 8 cm, a dla wstrząsu o magnitudzie 4.5 około 7 cm. Dla wstrząsu o najmniejszej magnitudzie nie zidentyfikowano wyraźnego obrazu deformacji na powierzchni. Wyniki posłużyły do analizy wielkości i zasięgu zmian na powierzchni powstałych w wyniku tych zdarzeń, a także do dyskusji na temat przydatności satelitarnej interferometrii radarowej do pozyskiwania wiarygodnych danych o deformacjach powierzchni powodowanych sejsmiką indukowaną działalnością górniczą.

EN

This paper presents the results of calculations using the differential satellite radar interferometry (DInSAR) method made for three induced shocks that occurred in the LGOM mining areas. The events selected for the analysis had the magnitudes of 4.8, 4.5 and 3.9 and occurred on the 26.12.2017, 20.07.2018 and 12.08.2018 respectively. To identify potential changes on the surface as a result of these shocks, SAR imagery recorded by Sentinel -1A and Sentinel-1B satellites immediately before and after these events was used. In the calculation process: coherence was determined, interferograms were developed, and then surface displacements in the line of the sight (LOS) were determined. For the magnitude 4.8 the vertical movements (LOS) reached - 8 cm, and for a magnitude 4.5 event approx. - 7 cm. For the seismic event with the smallest magnitude deformation, the image could not be identified on the surface. The results were used to analyze the size and extent of changes on the surface resulting from these events, as well as to discuss the usefulness of the satellite radar interferometry method to obtain reliable data on deformations caused by mining induced seismicity.

12

Idea kompleksowego monitoringu sejsmologicznego na terenie eksploatacji geozasobów w Polsce

Mirek Janusz, Koza Janusz, Łukasz Rudziński

Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie

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2019

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nr 8

11--16

PL

Sejsmiczność indukowana działalnością człowieka na terenie Legnicko-Głogowskiego Okręgu Miedziowego stanowi problem niemal od rozpoczęcia eksploatacji. W celu rejestracji zjawisk sejsmicznych zainstalowano sieci sejsmiczne nastawione na obserwację terenu LGOM lub poszczególnych kopalń. Najodleglejszą i najstarszą sieć stanowią sejsmometry regionalnych sieci międzynarodowych. Z kolei najbliżej ognisk wstrząsów znajdują się sejsmometry sieci dołowych. Najnowszą siecią sejsmiczną zainstalowaną na terenie 3 gmin ponad kopalniami miedziowymi jest Lumineos, złożona z sejsmometrów i akcelerometrów. Kopalnie i gminy posiadają także powierzchniowe sieci akcelerometryczne przeznaczone do obserwacji wpływu drgań na powierzchnię. W pracy przedstawiono zalety i wady poszczególnych systemów rejestracji oraz koncepcje łączenia danych z poszczególnych sieci. Zasygnalizowano problemy z tym związane i możliwości, jakie połączone sieci mogą zaoferować, by pomóc w rozwiązywaniu zadań z zakresu sejsmologii i prac inżynierskich.

EN

There, in the article the idea of a new approach to seismological observations in mining areas in Poland is presented. Based on experience in working with different networks in the LGCD (Legnica-Glogow Copper District) and USCD (Upper Silesian Coal District), there is opened discussion needed by profession, on the possibility of designing a comprehensive seismic monitoring. This type of approach will significantly improve the determination of seismic source parameters like location or estimation of shocks energy. As a consequence, the accuracy of the analysis of seismic hazard in mines and impact of exploitation on the surface will increase. Despite the unquestionable and obvious advantages of the comprehensive network, different categories of problems are presented, which have been faced during the design work. Some of the problematic elements can be solved using currently available options. Nevertheless, key ones, such as the conversion of formats or the creation of databases, require discussion within the scientific community and practitioners from coal and copper mines.

13

Tracking the development of seismic fracture network from The Geysers geothermal field

Orlecka-Sikora Beata, Cielesta Szymon, Lasocki Stanisław

Acta Geophysica

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2019

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Vol. 67, no. 1

341--350

EN

Underground fluid injections result in rock mass fracturing. The associated environmental hazards in a significant part stem from a possibility for linking these fractures. The resultant crevices may allow for an undesired and hazardous fluid migration. We studied the fracture linking problem on data from a part of The Geysers geothermal field in California, USA. We parameterized seismic events by the distance between hypocenter and injecting well, by the angle between the position vector of hypocentre and the maximum horizontal stress direction and by the angle of rotation required to turn the event’s doublecouple mechanism into the prevailing in this area faults’ orientation. To make these parameters comparable, we transformed them to equivalent dimensions. Based on distances between events in the transformed parameter space, we divided the seismic events into clusters. The percentage of potentially linked fractures in clusters was greater at low than at high injection rate.

14

Small-aperture array as a tool to monitor fluid injectionand extraction‑induced microseismicity: applications and recommendations

Karamzadeh Nasim, Kühn Daniela, Kriegerowski Marius, Lopez-Comino José Ángel, Cesca Simone, Dahm Torsten

Acta Geophysica

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2019

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Vol. 67, no. 1

311--326

EN

The monitoring of microseismicity during temporary human activities such as fluid injections for hydrofracturing, hydrothermal stimulations or wastewater disposal is a difficult task. The seismic stations often cannot be installed on hard rock, and at quiet places, noise is strongly increased during the operation itself and the installation of sensors in deep wells is costly and often not feasible. The combination of small-aperture seismic arrays with shallow borehole sensors offers a solution. We tested this monitoring approach at two different sites: (1) accompanying a fracking experiment in sedimentary shale at 4 km depth and (2) above a gas field under depletion. The small-aperture arrays were planned according to theoretical wavenumber studies combined with simulations considering the local noise conditions. We compared array recordings with recordings available from shallow borehole sensors and give examples of detection and location performance. Although the high-frequency noise on the 50-m-deep borehole sensors was smaller compared to the surface noise before the injection experiment, the signals were highly contaminated during injection by the pumping activities. Therefore, a set of three small-aperture arrays at different azimuths was more suited to detect small events, since noise recorded on these arrays is uncorrelated with each other. Further, we developed recommendations for the adaptation of the monitoring concept to other sites experiencing induced seismicity.

15

Seismicity induced by hydraulic fracturing and wastewater disposal in the Appalachian Basin, USA: a review

Brudzinski Michael R., Kozłowska Maria

Acta Geophysica

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2019

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Vol. 67, no. 1

351--364

EN

Eastern Ohio is an area of North America where a significant increase in seismicity rate was noted in the early 2010s. This increase has been associated with intensification of unconventional gas extraction performed in the Appalachian Basin and has been directly linked to two processes: hydraulic fracturing and disposal of the associated wastewater. In this paper, we review the recent seismicity in the Appalachian Basin including various episodes of induced seismicity that were temporally and spatially linked to operational activity, and we have performed some comparable analyses on the most recent sequences. The activities have not been as pervasive as other areas of North America, such that the cases are typically isolated and provide opportunities to study the seismogenic process in detail. The observed seismicity is concentrated in a narrow corridor that extends north–south in eastern Ohio and into central West Virginia, perhaps due to differences in operational targets and geologic variations. Ohio appears to have a higher prevalence of seismicity induced by wastewater disposal than surrounding states, but this is based on limited number of cases. Ohio also has an order of magnitude higher prevalence of seismicity induced by hydraulic fracturing than surrounding states, and prior work has suggested this is due to the targeting of the deeper Utica–Point Pleasant formation in Ohio that is closer to basement rocks than the Marcellus formation in West Virginia or Pennsylvania. In areas where hydraulic fracturing has induced seismicity, the percentage of stimulated wells that produce detectable seismicity is approximately 10–33%. Detailed studies of induced seismicity via double-difference relocation and focal mechanism analysis have revealed a series of linear fault segments, none of which correspond to previously mapped faults. Yet, the remarkable coherence in their orientation suggests these were preexisting, optimally oriented, and critically stressed. These fault orientations reveal a consistent regional stress field that only varies over a narrow azimuthal range from ~ 50° to 74°. The strongest observed seismic events in Ohio appear to occur in the Precambrian basement and indicate that these rocks have the maturity needed to produce M > 2 earthquakes and hence the greater potential hazard.

16

Opis drgań powierzchni terenu wywołanych wstrząsami górotworu uwzględniający kierunkowość tłumienia drgań

Bańka P., Lier E.

Systemy Wspomagania w Inżynierii Produkcji

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2018

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Vol. 7, iss. 1

241--255

PL

Sejsmiczność indukowana prowadzonymi robotami górniczymi w wielu przypadkach powoduje silnie odczuwalne drgania powierzchni terenu. W celu rejestracji drgań gruntu występujących na obszarach górniczych kopalń rozbudowywane są sieci stanowisk obserwacyjnych. Dane z tych punktowych obserwacji wykorzystywane są do odtwarzania pól przyspieszeń (prędkości) drgań gruntu na całym obszarze objętym dynamicznymi wpływami wstrząsów górotworu. Niejednokrotnie powszechnie stosowane relacje tłumienia nie umożliwiają uzyskania wystarczającej, z praktycznego punktu widzenia, dokładności opisu wyników obserwacji. W takich przypadkach wykorzystanie relacji tłumienia uwzględniającej kierunkowość rozchodzenia się drgań może pozwolić zwiększyć dokładność odtworzenia przyspieszeń (prędkości) drgań gruntu. W artykule przedstawiono wyniki odtworzenia zarejestrowanych przyspieszeń drgań gruntu wywołanych wstrząsami górotworu, które wystąpiły w obszarze jednej z kopalń GZW. We wszystkich prezentowanych przypadkach stwierdzono występowanie kierunkowości rozchodzenia się drgań. Wyniki obliczeń pokazują, że kierunek mniejszego tłu-mienia drgań powierzchni terenu jest równoległy do kierunku zaburzenia tektonicznego sąsiadującego z epicentrum wstrząsu generującego te drgania.

EN

Seismicity induced by conducted mining works in many cases causes the strongly felt surface vibrations. In order to record ground vibrations occurring in the mining areas, network of observation stations is being expanded. Data from these point observations are used to repro-duce acceleration (velocities) fields of ground vibrations over the entire area affected by dynamic impacts of rockmass tremors. Many times, commonly used attenuation relations do not allow to obtain a sufficiently practicable accuracy of the description of the results of observations. In such cases, using the attenuation relationship that takes into account the directivity of the propagation of vibrations may allow to increase the accuracy of the reproduction of ground vibration accelerations (velocities). In the article, the reproduction’s results of recorded accelerations of ground vibration caused by rockmass tremors, occurring in the area of one of the GZW mines, are presented. In all cases, the directivity of vibration propagation was observed. The results of the calculations show that the direction of lower surface vibration attenuation is parallel to the direction of the tectonic fault adjacent to the epicenter of the tremor generating these vibrations.

17

Statystyczna weryfikacja regresyjnego modelu relacji tłumienia wyznaczonego na podstawie wyników obserwacji drgań gruntu

Szuła Ł.

Przegląd Górniczy

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2018

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T. 74, nr 8

51--58

PL

Drgania gruntu wywoływane wstrząsami górniczymi stanowią coraz poważniejszy problem w wielu zakładach górniczych. Mogą one powodować uszkodzenia obiektów budowlanych, z reguły powodują zaniepokojenie mieszkańców terenów narażonych na występowanie dynamicznych wpływów wstrząsów górotworu. Z tego powodu bardzo ważne jest prowadzenie obserwacji wartości drgań powierzchni terenu oraz ich prognozowanie w aspekcie planowanych robót górniczych. Ponieważ nie jest możliwe prowadzenie pomiarów parametrów drgań gruntu we wszystkich obiektach, a także w celu sporządzania prognoz, konieczne jest dysponowanie zależnościami pozwalającymi określić wartość drgań w zależności od energii sejsmicznej wstrząsu i odległości epicentralnej. Wśród wielu propozycji empirycznego powiązania parametru opisującego intensywność drgań z energią wstrząsu oraz odległością od źródła najczęściej stosowana jest zależność Joyner’a – Boor’a. Parametry struktury stochastycznej modelu relacji tłumienia drgań szacowane są przy wykorzystaniu regresji liniowej. W celu umożliwienia sporządzania wiarygodnych prognoz wartości drgań gruntu, każdorazowo przy szacowaniu parametrów modelu, konieczne jest przeprowadzenie jego analizy weryfikacyjnej. W artykule szczególną uwagę zwrócono na sprawdzenie spełnienia założeń stosowania klasycznej metody najmniejszych kwadratów oraz konsekwencje ich niespełnienia.

EN

Ground vibrations triggered by mining tremors are an increasingly significant problem in numerous mines. They may cause damage to buildings, they usually cause anxiety among the inhabitants of areas exposed to the presence of dynamic influences of rock mass tremors. For this reason, it is very important to observe the values of vibrations on the surface of the area and to forecast them in the aspect of planned mining works. Since it is impossible to measure the parameters of ground vibrations in all facilities, and in order to prepare forecasts, it is necessary to have relations making it possible to determine the value of vibrations depending on the seismic energy of the tremor and epicenter distance. The Joyner-Boore model is most often used among the numerous proposals of an empirical link between the parameter describing the intensity of vibrations and the energy of the tremor as well as the distance from the source. Parameters of the stochastic structure of the ground - motion model are estimated with the use of linear regression. It is necessary to conduct a verification analysis of the model each time the model’s parameters are estimated in order to enable the preparation of credible forecasts of ground vibration values. Special attention in this paper is paid to the verification of the fulfillment of assumptions for using the classic method of least squares as well as the consequences of the failure to fulfil them.

18

Passive Seismic Tomography at Rudna Copper Ore Mine

Dębski W., Cianciara A., Koziarz E.

Przegląd Geofizyczny

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2018

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Z. 4

339--352

EN

Seismic tomography is a technique widely used to image the Earth’s interior at various scales, from the very local subsurface to the whole Earth’s interior. Successful tomographic applications in seismology have opened the question of whether, or not, the method can also be helpful in assessing the safety of mining operations. Long-time efforts and accumulated evidence with tomography imaging carried out at the Rudna copper mine clearly indicate that this is really the case. Repeating imaging of velocity distributions reveals that the observed temporal changes provide information that is useful for improving the safety of mining processes. In this paper, we describe our experience of performing seismic passive velocity tomography at the Rudna copper ore mine in the south-western part of Poland. We consider only the last 10 years, when the geophysical unit of Rudna copper mine began using an advanced modern tomography software developed originally for this mine.

19

The application of seismic interferometry for estimating a 1D S-wave velocity model with the use of mining induced seismicity

Czarny R., Pilecki Z., Drzewińska D.

Journal of Sustainable Mining

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2018

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Vol. 17, iss. 4

209--214

EN

The main objective of this paper is to present the usefulness of the seismic interferometry method to determine the S-wave velocity model of the rock mass affected by exploitation in the KGHM Rudna copper ore mine. The research aim was achieved on the basis of seismic data, acquired from seismograms, of 10 strong seismic events of magnitude greater than 2.6. They were recorded by a pair of seismometers deployed on mining terrain. In the first stage, the Rayleigh wave between seismometers was estimated. Then, the group velocity dispersion curves of fundamental and first higher modes were identified. Finally, inversion of the dispersion curves to a 1D S-wave velocity model up to 500m in depth was obtained. The velocity model was determined for the part of the rock mass partially affected by mining. The results confirm similar rock mass structure and velocities of the subsurface layers as those obtained by the archival 3D model. In both models, a high degree of correlation in the boundary location between the overburden of the Cenozoic formations and the bedrock of the Triassic formations was observed. The applied methodology can be used to estimate the S-wave velocity model in other mining regions characterized by strong seismicity.

20

The acceleration response spectra for Legnica-Glogow copper district

Olszewska D.

Technical Transactions

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2017

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Vol. 9(114)

99--115

EN

This paper presents average normalised acceleration response spectra calculated for mining induced seismic events which were recorded by twenty-one stations located in the area of Legnica-Glogow Copper District (LGCD). In this paper, 5.246 ground motion signals with peak ground acceleration (PGA) over 0.03 m/s2 were analysed. The ground motions were caused by 1.886 mining events with ML greater than 2 (energy > 105J), which occurred from 2004 to 2015. The design response spectra were estimated based on average normalised acceleration response spectra. Further analysis of results shows that the shape and amplitude of response spectra are strongly dependent on the event magnitude, the epicentral distance and the location of the stations. The obtained response spectra could be used for computing seismic forces which have impact on buildings response to ground motions caused by mining events in LGCD.

PL

W pracy wyznaczono średnie znormalizowane przyspieszeniowe spektra odpowiedzi na podstawie zapisów drgań wstrząsów górniczych, zarejestrowanych przez 21 stanowisk akcelerometycznych znajdujących się, na terenie Legnicko Głogowskiego Okręgu Miedziowego (LGOM). Do analizy wykorzystano 5246 rejestracje drgań gruntu o wartościach szczytowych powyżej 0.03 m/s2, wywołane 1886 wstrząsami górniczymi, o ML5J), które miały miejsce od 2004 do 2015 roku. Na podstawie wyznaczonych znormalizowanych przyspieszeniowych spektrów odpowiedzi wyznaczono wzorcowe spektrum odpowiedzi dla tego rejonu. Pokazano także, że kształt i amplituda spektrów odpowiedzi zależy od wielkości zjawiska, odległości epicentralnej oraz od miejsca. Otrzymane wzorcowe spektrum odpowiedzi może być wykorzystywane do obliczania sił sejsmicznych oddziałujących na budowle w wyniku drgań podłoża wywołanych wstrząsami górniczymi w tym rejonie.