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Extension the informativity of seismic tomography in exploitation of mines |
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Extension the informativity of seismic tomography in exploitation of mines Author: A. Lurka
The paper presents the application of gradient and laplace differential operators to the velocity field obtained from passive tomography calculations. The passive tomography calculations were performed using the evolutionary algorithms. These algorithms are very often used when searching of global minimum is required for multidimensional functions. The main purpose of using gradient and laplace differential operators was to find the correlations between these ╣uantities and the seismic hazard in Polish mines. From previous experiences of using passive tomography calculations to seismic hazard asses-sment in Polish mines one can conclude such relationship between seismic hazard and seismic velocity anomaly. However there are observations showing that seismic anomaly does not correlate well with areas of high seismic activity. It turns out that other ╣uantities: the velocity gradient and laplace operator of velocity field correlates much better in such situations. The main problem of comparing results of the calculated velocity anomaly, the velocity gradient and the laplace operator of velocity field is that these ╣uantities have different physical units. To compare the seismic velocity anomaly, the velocity gradient and the laplace operator of velocity field the method of normalization of these differential operators was introduced. As the practical application of using the yelocity gradient and the laplace operator of velocity field the passive tomography calculations in the area of the longwall no. 772 from Zabrze Bielszowice coal minŕ were carried out. The presented results show that velocity gradient and laplace operator of yelocity field correlates better with areas of high seismic hazard than seismic anomaly. Especial│y the yelocity gradient images give new physical insight into the assessment of seismic risk in mines.
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2011