Wyniki wyszukiwania - Biblioteka Nauki

1

Ground-motion prediction equations for induced seismicity in the main anticline and main syncline, Upper Silesian Coal Basin, Poland

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Golik A. , Mendecki M.

Acta Geophysica

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2012

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tom Vol. 60, no. 2

410-425

EN

The purpose of the research was to determine parameters of ground-motion models for two areas characterized by considerable induced seismicity and different geology. Fifty-nine events collected from surface seismological stations of coal mine "Bielszowice" (at the Main Anticline, South Poland) and 144 events from coal mine "Ziemowit" (at the Main Syncline, South Poland) were used for computation. For both areas, simple ground-motion prediction equations (GMPEs) without site effects were derived, but the model was acceptable only for "Bielszowice" area. The GMPE was calculated once again for "Ziemowit", but this time we took into consideration the amplification coefficient, which significantly improved the model solution. Finally, the theoretical value of amplification was calculated. Knowing that the amplification is associated with subsurface layers, we used three different models of overburden: (i) with Quaternary sediments only, (ii) with a complex of Quaternary-Tertiary sediments, and (iii) with a complex of Quaternary-Tertiary-Triassic sediments and Carboniferous as a basement. Usually, the amplification of vibrations appears in the Quaternary sediments. However, theoretical calculations of amplification were consistent with the results obtained from GMPE when a rigid Carboniferous substratum was applied.

2

A study of the interaction among mining-induced seismic events in the Legnica-Głogów Copper District, Poland

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Orlecka-Sikora B. , Papadimitriou E. , Kwiatek G.

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tom Vol. 57, no. 2

413-434

EN

We applied the Coulomb stress transfer technique to investigate interactions among seismic events induced by mining works in the Rudna mine in the Legnica-Glogów Copper District in Poland. We considered events with energy greater than 10⁵ J from the period 1993-1999. We examined the influence of the cumulative static stress changes (ΔCFF) due to previous events on the generation of subsequent ones. The results indicate that in many cases strong mining tremors produce changes in the state of stress of a sufficient magnitude to influence subsequent events. The location of over 60% of events is consistent with stress-enhanced areas where the values of ΔCFF were above 0.01 MPa. For most of the events located inside areas of a calculated negative ΔCFF, their modelled rupture zone was partially located inside stress enhanced area, providing thus additional evidence for possible triggering at the nucleation point.

3

Distribution of Peak Ground Vibration Caused by Mining Induced Seismic Events in the Upper Silesian Coal Basin in Poland

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Dubiński J. , Mutke G. , Chodacki J. , Dubiński J. , Mutke G. , Chodacki J.

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4

Badania dynamiki zdarzeń w przestrzeni fazowej procesu sejsmiczności indukowanej

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Laskownicka A. , Mortimer Z. , Korytowska B.

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2006

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tom nr 6

32-34

PL

Prezentowane są badania wielowymiarowej przestrzeni fazowej strumienia sejsmiczności. Dynamika układu przejawia się przez zmiany zdarzeń sejsmicznych na trajektorii fazowej procesu. Wymiary przestrzeni fazowej i jej atraktor zostały oszacowane przy zastosowaniu szeregów czasowych uogólnionej odległości pomiędzy kolejnymi wstrząsami w przestrzeni energii i położenia zdarzeń.

EN

Phenomena of mining induced seismicity are presented as nonlinear dynamics systems. The dynamics is characterized by changes of the seismic event position on the phase trajectory of the process. Embedded spaces constructed from the observations of individual variables were analysed. Dimensions of the phase space and its attractor were approximated based on the time series of the time distance and generalized distance between succeeding shocks, energy and the epicentre/hypocenter. Attention was chiefly concentrated on the generalized distances between succeeding shocks and their variations during high and low seismic activity.

5

Aktywność sfer uskokowych w polach ścianowych

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Patyńska R.

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2007

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tom nr 6

33-35

PL

Praca bazuje na pomiarach dołowych sejsmiczność indukowanej miejsc zaistniałych wstrząsów i tąpnięc w latach 1993 - 2003. Zestawienie tych pomiarów z geolo-giczno-gómiczymi uwarunkowaniami eksploatacji wskazuje na możliwość ograniczenia zagrożenia tąpaniam, poprzez właściwe usytuowanie kierunku biegu ściar względem płaszczyzn uskokowych. Przechodzenie frontem ścian przez strefy uskokowe w istotny sposót zaburza ich planowany bieg. Analiza szczegółowa tektoniki, zwłaszcza stref uskokowych, pozwala ne wyznaczenie miejsc o zróżnicowanym jednostkowyrr wydatku energetycznym - JWE (J/t). Usytuowanie płaszczyzn uskoków w stosunku do struktury warstw otaczających eksploatowany pokład pozwala ne uściślenie warunków istnienia strefo różnej intensywność zjawisk sejsmicznych w każdym polu ścianowym.

EN

The study is based on the underground mining - induced seismicity measurements taken in the areas of mine tremors and rockbursts occurrences during a period from 1989 to 2006. From the juxtaposition of the measurement results and the mining and geological conditions, it follows that there is a possibility to reduce the rockburst hazard through the proper situation of the longwall face advance direction relative to the fault planes. Passing the fault zones by longwall faces may considerably disturb their planned progress The detailed analysis of tectonics, particularly that of fault zones, allows locating places of the differentiated expenditure of energy (JWE, Jit). The position of fault planes with respect to the structure of the stratę surrounding the seam being mined allows defining accurately the conditions of existence of the zones of different intensity of seismic events in each panel.

6

Seismic doublets and multiplets at Polish coal and copper mines

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Gibowicz S.

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2006

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tom Vol. 54, no. 2

142-157

EN

The following criteria for selection of doublets at Polish coal mines were accepted: the difference in magnitude (based on seismic moment) of two events not larger than 0.15, the distance between their hypocenters not greater than 150 m, and the time interval between their occurrence not longer than 10 days. Similarly, the criteria for seismic events at copper mines are: the difference in magnitude not exceeding 0.15, the distance not greater than 200 m, and the time interval not longer than 20 days. Seismic events from the Wujek and Ziemowit coal mines that oc-curred between 1993 and 1995, and seismic events from the Polkowice copper mine that occurred between 1994 and 1996 and from the Rudna copper mine that occurred between 1994 and 2004 were considered. Their source parameters and focal mechanisms were known in most cases from previous studies. Altogether 108 seismic pairs from coal mines and 118 pairs from copper mines were found, forming doublets, triplets and quadruplets, within the magnitude range from 0.7 to 3.5. The distance and time intervals between two events forming pairs are not dependent on magnitude of these events. The focal mechanism of seismic events forming pairs is similar in over 60 percent of pairs at coal mines and in about one third of pairs at copper mines. Spa-tial distributions of doublets in particular sections of coal and copper mines display dominant linear trends, characteristic for a given area, which are often in conformity with the direction of nodal planes determined by fault plane solution of one or both the events forming a doublet. In such cases, the rupture plane can be discriminated among the nodal planes.

7

Apparent stress and stress drop from seismic events induced by mining

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Gibowicz S.

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2002

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tom Vol. 50, nr 1

35-49

EN

Seven sets of the values of uniformly estimated apparent stress and Brune's stress drop from 987 seismic events, with moment magnitude ranging from -3.6 to 3.8, were collected from two South African gold mines, two Polish coal and two copper mines, and from the Underground Research Laboratory (URL) in Canada. They are used to examine their relations with radiated energy, seismic moment and source dimension to provide observational evidence of differences for slip-weakening as compared to velocity-weakening friction, found from elasto-dynamic source modeling of Shaw (1998). The observations from various data sets scale differently, but their pattern is not always distinctly related to the different frictions. The distribution of the apparent stress divided by the stress drop as a function of seismic moment is the most similar to the relevant distribution obtained by modeling, and it seems that both modes of friction are possible during the generation of seismic events in various mining environments.

8

Comparison of source time functions retrieved in the frequency and time domains for seismic events in a copper mine in Poland

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Domański B. , Gibowicz S.

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2001

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tom Vol. 49, nr 2

169-188

EN

The extraction of source time functions based on empirical Green's functions is especially convenient for source studies of seismic events in mines, where underground seismic networks are situated in the source area and are often composed of a large number of sensors. The empirical Green's function deconvolution techniques were applied to retrieve the source time functions from the records of P waves of several seismic events that occurred in 1998 at Rudna copper mine in Poland. The selected events were located within the underground network composed of 32 vertical sensors situated at a depth of about 1 km; the size of the network is about 10 by 10 km. Their moment magnitude ranged from 2.7 to 3.2. The records of smaller events from the same area and with similar source mechanism, with moment magnitude from 2.2 to 2.4, were accepted as empirical Green's functions. The results of classic deconvolution approach in the frequency domain are reported elsewhere. The results of the application of projected Landweber deconvolution in the time domain to the same set of data are described here. The projected Landweber approach is an iterative deconvolution technique, allowing introduction of physical constrains on the final source time function. This technique successfully overcomes the instability effects of the deconvolution process inherent in the frequency domain and provides stable and reliable relative source time functions retrieved at several stations. Although the results obtained in the frequency and time domains were found to be similar, the time domain approach provides more objective determination of the source time function duration, essential for a proper determination of the source dimension. The relative source time functions retrieved by both methods display directivity effects in several cases, implying unilateral rupture propagation. The rupture propagation direction and rupture velocity were estimated from the distribution of pulse widths and pulse maximum amplitudes as a function of the station azimuths.

9

Radiated energy scaling for seismic events induced by mining

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Gibowicz S.

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2001

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tom Vol. 49, nr 1

95-111

EN

Seven sets of the values of radiated energy from 987 seismic events from two South African gold mines, four Polish coal and copper mines, and from the Underground Research Laboratory (URL) in Canada are used to examine their scaling with seismic moment, apparent stress and average displacement. Moment magnitude of these events ranges from -3.6 to 3.8, the seismic energy ranges from 1x10(-3) to 1x10(11) J, and the apparent stress is between 0.0025 and 5 MPa. The slope of regression straight line between the logarithm of radiated energy and that of seismic moment is very close to 1.5 in all cases, which seems to have theoretical justification. The average values of seismic energy, however, referred to the same range of seismic moment, are about 30 times higher for seismic events from South African hard-rock mines that those observed from events in Polish mines. Similarly, the slope of a linear regression between the logarithm of apparent stress and that of energy is fairly close to 1/3 for the events from South African and Polish mines. But the average apparent stress, referred to the same range of seismic energy, is about 10 times higher for the events in South Africa than for those in Poland. The relations between the average slip and the energy are on a logarithmic scale surprisingly consistent and more regular than similar relations based on seismic moment. The events from the URL follow the same trend as the events from South Africa, whereas for the events from Poland the average slip is about 5 times lower than that for the other events.

10

Method of evaluating the probability of a strong tremor

63%

Sokoła-Szewioła V.

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2008

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tom T. 24, z. 3/1

41-49

EN

The method of evaluating the probability of a strong tremor using the relationship between the size of the ground surface deformation and recorded seismic activity of a rock mass. Seismicity induced by conducted mining was characterized by total seismic energy of the tremors E and the number of tremors N. The assumption was made that there is a relationship between the volume of the subsiding through created on the surface and observed seismicity of a rock mass. The cross-section area Pw of the subsiding through along the observation line situated parallel to the direction of an advancing wall front was assumed as an index of the deformation of the ground surface in the model. The method described uses a logit model. The total seismic energy Ei recorded in time-periods of realized geodesic surveying was used in the model, on the basis of the results, in which the Pw was determined. It was assumed that the seismic energy which should be released is proportional to the increasing area Pw. The aim of the evaluation is to determine the probability of a strong tremor occurrence on the basis of the increasing area Pw and Ei (total seismic energy released in i time-period of realized periodical geodesic levelling surveying). It was assumed that the relationship will be searched that will allow us to calculation the probability of a strong tremor with the energy of the order of above 5ź104 [J] on the basis of the determined logit model. The relationship between the occurring frequency of particular values of the dependent variable and the selected independent variables was described in the model. The method was applied for the set of observations obtained as a result of the research project 4T12A 032 26. The functional relation between Ei, Pw and L (logit) was determined. The calculated multiple correlation coefficient R = 0.528 is on the level p < 0.05 significantly different from zero. The model can be used for forecasting the probabilities of strong tremors occurrence.

PL

Metoda szacowania prawdopodobieństwa wystąpienia silnego wstrząsu podziemnego wykorzystująca zależność pomiędzy odkształceniem powierzchni i zarejestrowaną aktywnością sejsmiczną górotworu. Aktywność sejsmiczna wywołana przez górnictwo określona została jako całkowita energia sejsmiczna wstrząsów E, a ilość wstrząsów jako N. Założona została zależność pomiędzy objętością koryta osiadającej na powierzchni a zaobserwowaną aktywnością sejsmiczną. Za wskaźnik modelowej deformacji powierzchni przyjęto powierzchnię przekroju Pw osiadającej synkliny wzdłuż linii obserwacyjnej usytuowanej równolegle do posuwającego się przodka ścianowego. Opisana metoda wykorzystuje model logitowy. Na podstawie wyników, w których określono Pw, w modelu wykorzystano całkowitą energię sejsmiczną Ei zarejestrowaną w poszczególnych okresach czasu pomiarów geodezyjnych. Przyjęto założenie, że energia sejsmiczna, która powinna zostać uwolniona jest proporcjonalna do wzrastającej powierzchni Pw. Szacunki mają na celu określenie prawdopodobieństwa wystąpienia silnego wstrząsu na podstawie powiększającej się powierzchni Pw oraz Ei (całkowitej energii sejsmicznej uwolnionej w okresie czasu i przeprowadzonych okresowych geodezyjnych pomiarów niwelacyjnych). Przyjęto założenie, że znaleziona zostanie zależność, która pozwoli na obliczenie prawdopodobieństwa wystąpienia silnego wstrząsu podziemnego posiadającego energię rzędu ponad 5.104 [J] na podstawie modelu logitowego. W modelu opisano zależność pomiędzy występującą częstotliwością określonych wartości zależnych zmiennych oraz wybranych niezależnych zmiennych. Metodę zastosowano dla szeregu obserwacji uzyskanych w wyniku projektu badawczego 4T12A 032 26. Określono funkcjonalną zależność pomiędzy Ei, Pw oraz L (logit). Obliczony współczynnik korelacji wielokrotnej R = 0,528 znajduje się na poziomie p <0,05, różniącym się znacząco od 0. Model może zostać wykorzystany do prognozowania prawdopodobieństw występowania silnych wstrząsów podziemnych.