Use of Neural Networks to Forecast Seismic Hazard Expressed by Number of Tremors Per Unit of Surface
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Pure and Applied Geophysics
Use of Neural Networks to Forecast Seismic Hazard Expressed by Number of Tremors Per Unit of Surface TOMASZ CICHY,1 STANISłAW PRUSEK,1 JANINA S´WIA˛TEK,1 DEREK B. APEL,2 Abstract—The seismic and rock burst hazard should be considered as one of the most important hazards in Polish hard coal and copper ore mines. Over the last several years, Upper Silesia has witnessed a constant process of limiting the extraction of hard coal. Despite a significant decrease in production, no reduction in the number of registered high-energy tremors with energy higher than 105 J. is observed. Therefore, it is important to develop the existing methods for assessing the state of seismic hazard and seeking new ways to estimate the level of this threat. The article presents the results of research aimed at determining the possibility of using artificial neural networks to forecast the level of seismicity induced by mining operation. The data used in the conducted research came from the area of operation of a heavily seismic USCB mine. The presented research results showed that in the case of the discussed area, the use of the new tool, which is an artificial neural network, allowed to obtain good results of the forecast of the number of tremors. For the data set in question, the neural network with optimal architecture is composed of twelve neurons in the entrance layer, two neurons with bipolar characteristics in the hidden layer and one neuron with linear or bipolar characteristics in the initial layer. The results of calculations made for the highly seismic area of mining works carried out in a hard coal mine confirmed the possibility of using neural networks to estimate the changes in the size of induced seismicity associated with the deposit operation. Keywords: Elastic strain energy, induced seismicity, neural networks.
1. Introduction Seismic and rock burst hazard are the most dangerous natural hazards occurring in Polish hard coal mines. Mining works carried out in many regions generate rock mass tremors that may cause rock bursts. Strong tremors may also cause surface
1
Central Mining Institute, Katowice, Poland. University of Alberta, Edmonton, Canada. E-mail: [email protected] 3 Chongqing University, Chongqing, China. 2
and YUANYUAN PU3
vibrations and, as a consequence, occasionally damage buildings. In Poland, mining-induced tremors occur in the area of coal mining in the Upper Silesian Coal Basin (USCB), in the Legnica-Głogo´w Copper basin (Fuławka et al. 2018) where copper deposits are extracted and in Bełchato´w area where lignite is extracted by opencast mining. The strongest tremors are related to the equalization of stresses in the ground related to the consolidation of inflows from mining operations with natural stresses related mainly to the occurrence of tectonic faults. In USCB, strong tremors have been recorded for over 50 years by Upper Silesian Regional Seismic Network and are catalogued at the Central Mining Institute. Currently, in USCB, about 1000 tremors weaker than the s
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