Slawomir J. Gibowicz

Seismicity induced by mining: Ten years later

Publisher Summary During the past several years, seismic monitoring has been expanded in several mining districts, a number of new techniques have been introduced, and new significant results have been obtained in studies of the seismic events induced by mining. New techniques in seismic monitoring in mines, geological and mining factors affecting seismicity, source parameters and their scaling relations, and shearing versus non-shearing source mechanisms are briefly described in the chapter. Statistical techniques and methods that are used extensively in recent years in studies of seismicity in mines, especially for seismic hazard assessment are discussed. This chapter provides an overview of the seismic discrimination between underground explosions and seismic events originating in deep mines. Seismic events induced by mining are not uniformly distributed in either space or time. Extensive studies performed on the space-time-energy distributions of seismic events in mines show that the tendency to form nests, swarms, and clusters is commonly observed. Seismicity in mines is strongly affected by local geology and tectonics, and by interaction between mining and crustal state of stress on a local and regional scale.

Seismicity Induced by Mining: Recent Research

Abstract The present review of seismicity induced by mining is a continuation of the previous reviews, published in 1990 and 2001 in Advances in Geophysics, describing the problems involved and the state-of-the-art of relevant research in this field at the end of 1980s and 1990s. During the last decade, seismic monitoring has been expanded in several mining districts, a number of new techniques have been introduced, and new significant results have been obtained in studies of seismic events induced by mining. This review is organized similarly to some extent to the previous ones. New techniques in seismic monitoring in mines, mining factors affecting seismicity, source mechanisms and source time functions, source parameters and their scaling relations are briefly discussed. Precursory phenomena observed in mines and some attempts at prediction of larger events are reviewed. The new results obtained so far by the Japanese research group in South African gold mines, the concepts of stress diffusion and of “critical earthquakes” applied to seismicity in mines, and numerical modeling of rock mass response to mining are also briefly discussed.

Seismicity Induced by Mining

Publisher Summary This chapter describes the various aspects of seismicity induced by mining. An increase in seismicity in seismic areas and the generation of seismicity in aseismic areas have been observed as a result of deep underground mining and large-scale surface quarrying. Seismicity induced by mining, fluid injection, and reservoir loading are the three main types of triggered seismicity affecting the preexisting stress field in different ways. Mining operations, leading to the removal of large masses of rock, have their major impact on the elastic stress and fluid injections influence the distribution of fluid pressure in the upper layers of the crust. The orientation of the principal stress in nature is different in different tectonic environments. Regions of thrust faulting are characterized by the minimum compressive stress being vertical, in regions of normal faulting the maximum compressive stress is vertical, and in regions of strike-slip faulting the intermediate stress is vertical. It is found that the depth of mine tremors strongly depends on the type of rocks forming the roofs and floors of ore seams.

Source Time Function of Seismic Events at Rudna Copper Mine, Poland

Abstract — The empirical Greens function deconvolution technique is used to retrieve the source time functions from the records of P waves of seven seismic events that occurred at the Rudna copper mine in 1996 and were located in the middle of the underground network. Their moment magnitudes ranged from 2.1 to 2.9. The records of smaller events from the same area and with similar source mechanism, with moment magnitudes ranging from 1.5 to 2.0, were accepted as empirical Greens functions. The relative source time functions were successfully retrieved at a number of stations for six events. Directivity effects, implying unilateral rupture propagation, were observed in five cases. The azimuth of rupture propagation direction and the rupture velocity were estimated from the distribution of pulse widths and pulse maximum amplitudes as a function of the cosine of station azimuths. The rupture propagated approximately either from south to north or from north to south. The rupture velocity was low, ranging from 0.25 to 0.54 of the shear-wave velocity. The source dimensions, represented by the fault length, were also small in comparison with those estimated in the frequency domain and ranged from 80 to 250 m.

Scaling relations for seismic events induced by mining

The values of seismic moment andS-wave corner frequency from 1575 seismic events induced in South African, Canadian, Polish, and German underground mines were collected to study their scaling relations. The values ofP-wave corner frequency from 649 events were also available. Seismic moments of these events range from 5*103 to 2*1015 N·m (moment magnitude is from −3.6 to 4.1), theS-wave corner frequency ranges from 0.7 to 4438 Hz, and theP-wave corner frequency is between 5 and 4010 Hz. The slope of a regression line between the logarithm ofS- andP-wave corner frequencies is equal to one, and the corner frequencies ofP waves are higher than those ofS waves on the average by about 25 percent. In studies of large and moderate earthquakes it has been found that stress drop is approximately independent of the seismic moment, which means that seismic moment is inversely proportional to the third power of corner frequency. Such a behavior was confirmed for most of the data considered here. A breakdown in the similarity betwen large and small events seems to occur for the events with moment magnitude below −2.5. The average values of seismic moment referred to the same range of corner frequency, however, are vastly different in various mining areas.

Magnitude and energy of subterrane shocks in Upper Silesia

РезюмеРассматриваются зависимости собственной частоты и затухания от парциальных постоянных сейсмографов для схожих парциальных частот или схожих парциальных затуханий сейсмометра и гальванометра и для некоторых конкретных значений парциальных постоянных сейсмографа, не удовлетворяющих ни одному из предыдущих соотношений. Два первых случая значений парциальных постоянных сейсмографа (n01=knn02,D01=kDD02,kn=1 илиkD=1) дают возможность сделать общий вывод собственных постоянных (пар. 2a, 2b), третий случай решался приближенно.Если не учитывать эти решения собственных постоянных, справедливые в ограниченных пределах σ2 (дляkn=1,D01>1,D02>1, и дляkn≠1,kD=1,D01≧1), то на основании произведенных расчетов получается, что по мере возрастания коэффициента связи собственные частоты сейсмометра и гальванометра проявляют склонность к достижению схожих эначений. Как только это будет достигнуто (или в случае, что парциальные частотыуже равновелики) собственные частоты обеих систем будут схожи. Собственное затухание в ряде случаев (kn=1,D01 иD02—произвольной величины;kn≠1,kD=1,D01>1; часть комбинацийkn≠1,kD≠1) проявляют обратную тенденцию а именно: разности собственных затуханий по мере возрастания связи увеличиваются, и в случае неравных парциальных затуханий меньшее собственное затухание будет уменьшаться, а большее—увеличиваться. Однако помимо этого существуют такие комбинации парциальных постоянных сейсмографа, когда разности собственных затуханий для части значений σ2 0не меняются (kD=1,D01<1) и оба затухания превыааюот значение парциального затухания или же разности собственных затуханий, хотя и увеличиваются, однако затухание системы с меньшим парциальным эначением возрастает (некоторые случаиkn≠1,kD≠1). Характер же изменений собственных частот притом сохраняется. Такое комбинирование парциальных значений является выгодным с точки эрения использования связи для достижения значительного увеличения некоторых типов сейсмографов.

Physics of fracturing and seismic energy release: A review

This review was prepared as an opening lecture for the International Symposium on Physics of Fracturing and Seismic Energy Release, held at the Castle of Liblice near Prague from October 28 to November 1, 1985, and organized by the Geophysical Institute of the Czechoslovak Academy of Sciences. The review attempts to classify and synthesize results of recent studies in fracture mechanics and earthquake source physics. The following topics are discussed: recent developments in fracture mechanics, earthquake source modeling, heterogeneous fault planes, foreshocks and aftershocks, faults and fractals, and moment tensor solutions. This rather broad range of topics prevents presentation of a complete list of all relevant works, though over one hundred and seventy references are cited.

P-wave travel time residuals from the Alaskan aftershocks of 1964

Abstract Travel time residuals of P-waves from 90 Alaskan aftershocks of 1964 have been studied. The data were selected from ISC bulletins. Altogether 9889 observations from 183 stations in the distance range 3 to 97° have been analyzed by a least-squares technique used by Cleary and Hales (1966a). In this way, deviations from the J-B tables have been separated from the station effect. The same method was subsequently employed to reveal the anomalies of azimuth and epicentral distance from the station residuals. Azimuth-distance dependent anomalies, called here the regional residuals, were calculated for 7° azimuth cells in the range 269 to 140°, and for 2° distance cells in the range 3 to 93°. Regional residuals distribution show some general features. Station residuals have been considered to three approximations: after separation from J-B travel time corrections, after removing the azimuthal effect, and after removing the distance effect. Station residuals to the third approximation are in general smaller from those to the first approximation, they do not show a marked regional trend and their frequency distribution is fairly normal. No evidence of any correlation with station height was found.