A b s t r a c tThis article presents a method of predicting the peak horizontal velocity of ground motion, PHV, and the duration of vibration, t H , for strong seismic events (E 5·10 6 J, M L > 2.5) in the Upper Silesian Coal Basin (USCB). For the prediction of PHV, a model proposed by Si and Midorikawa was used. The regression method takes into account the impact of the local geology under seismic stations on the ground motion according to the Eurocode 8 classification. The ground classification was based on the results of a seismic survey conducted near the seismometer stations. This method is of great practical use because it allows the degree of vibration intensity to be determined on the basis of the Mining Seismic Instrumental Intensity Scale MSIIS-15 (acronym GSI GZW in Polish version) at any distance from the epicentre of the seismic events induced or triggered by mining.

Seismic energy propagation from the hypocentre of mining-induced tremors usually causes an uneven distribution of the peak ground velocity PGVHmax in tectonically complicated structures, and consequently, an uneven distribution of damage to buildings located on the ground surface. This study aimed to estimate the impact of high-energy mining-induced tremors in fault zones on damage to buildings. In the study, we describe a case of one of the highest-energy mining-induced tremors E = 4.0 · 108 J (local magnitude ML = 3.6) that occurred in the Upper Silesian Coal Basin (USCB), Poland. The hypocentre of the tremor was most probably located in the Barbara fault zone, one of the larger faults in that western part of the USCB. Numerous damaged buildings on the terrain surface were registered, both in the epicentral zone and at a greater distance from the epicentre, mostly from the southern side of the Barbara fault zone. We calculated that the tremor was characterised by a normal slip mechanism associated with the same kind of fault as the Barbara fault. The azimuth of the nodal planes was similar to the west-east direction, which is consistent with the azimuth of the Barbara fault. From the focal mechanism, the greatest propagation of seismic energy occurred in south and west-east directions from the tremor hypocentre towards the surface. It was found that from the northern side of the hanging wall of the Barbara fault, there were 14 instances of damage (19%), and in the southern part of a hanging wall, there were 58 (81%). Therefore, the directionality of seismic energy propagation is aligned with the focal mechanism acting in the Barbara fault. It has also been concluded that a width of the zone of up to about 1200 m along the Barbara fault is the most threatening on the basis of registered building damage in the geological conditions of USCB. The study has shown that in assessing the impact of mining-induced tremors on buildings and the environment, the disturbance of seismic energy propagation by larger faults should be considered.

Mining seismic events have been associated with the mining of hard coal in the Upper Silesian Coal Basin in Poland for many years. These seismic events pose a threat to people working underground and cause damage to construction facilities on the surface. It is possible to predict seismic vibrations from mining seismic events using numerical calculations. One such method is the spectral element method (SEM). In this method, synthetic seismograms that enable the imaging of the full waveform are calculated. A complex mechanism of the source is assumed by applying the seismic moment tensor, which best reflects the balance of forces in the source. This paper presents the results of SEM modeling of ground motions of a seismic event which occurred on November 8, 2018, in the Budryk mine with a magnitude of 3.8 on the Richter scale. The modeling results show that even if the calculated synthetic seismograms do not fully correlate with real vibration registrations, it is possible to determine the peak values of seismic vibrations at any point in the model. This method can be a good complement to the analytical methods used to assess seismic hazard caused by mining seismic events.

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