## 2 Materials and Methods
### General Characteristic of Seismic Activity and Rockburst Hazard  
In the first 6 years of mining operations in the panel XVII/1, seismic activity expressed as the number of seismic events (\(\Sigma\)N), total energy level (\(\Sigma\)E) and seismic energy per a single high-energy tremor (\(\Sigma\)E\({}_{\rm w}\)/N\({}_{\rm w}\)) (Table 2) was variable. In the investigated period, the total number of registered events with energy \(\geq\)10\({}^{3}\) J was 1504, equivalent to the total energy expense of 1.45 \(\times\) 10\({}^{9}\) J. While the overall seismic activity remained in the low- and medium-energy range, still 16.3% of the entire population of tremors were high-energy events (\(\geq\)10\({}^{5}\) J) (254, year average \(\sim\)41/year), accounting for 99.2% of total seismic energy released from the rock strata (1.43 \(\times\) 10\({}^{9}\) J, year average \(\sim\)2.38 \(\times\) 10\({}^{8}\) J/year). The distribution of seismic events in the function of released energy (Figure 4) can be expressed by an exponential dependence with a relatively good fit (R\({}^{2}\) = 0.965) and the general criteria of the Gutenberger-Richter distribution are satisfied. It is of primary importance considering the random nature of events and the ability of the rock strata to release large amounts of energy; hence, the likelihood of triggering a high-energy event tend to decrease sharply, yet the probability of a tremor occurrence still cannot be assumed to be almost non-existent. Considering the number of seismic events, it is reasonable to assume that even though the probability of its occurrence remains low, a high-energy event is bound to occur after a certain time. From the standpoint of mining practice, it will occur after the working face advanced over a specified distance. Figure 3: Status of mining operations in panel XVII/1 at the end of Year 6. In relation to the progress of mining operations, the level of seismicity expressed by a number of registered events was steadily increasing (except for Year 6), both in terms of high-energy tremors and the entire population of events (\(\geq\)10\({}^{3}\) J). In consideration of the energy class, a cyclic nature of seismic activity can be observed and events in the energy range 10\({}^{7}\)-10\({}^{8}\) J occur regularly, which affects the total value of seismic energy release and the average energy release per one event. Insofar as this cyclicity can be attributed to mining activities, the occurrence of high-energy tremors is indicative of the uniform yet random nature of such events even though the energy might be released during weaker tremors. The foci of registered seismic events (including high-energy tremors) are concentrated in the centre of the panel, though some of them appear to be correlated with the locations of faulting zones (Figure 5). In regard to the foci locations with respect to the working face advance, it is reasonable to conclude that the majority of tremors were registered in the undisturbed strata, prior to the panelling operations; those registered in old abandoned excavations were a minority. In the analysed 6-year period of continuing mining operations in panel XVII/1, 7 rockbursts and rock de-stressing events were registered in the excavations, differing in magnitude and impacts they exerted. All these events were triggered by high-energy tremors whose foci were located mostly near the boundary of the old excavations, along the panelling line or in the vicinity of tectonic disturbances with diverse profiles and faults with the downthrow not exceeding the height of the face entry drivage. Analyses conducted within the scope of the present study have relevance to the conditions prevailing after the occurrence of two rockbursts registered in December in Year 3 triggered by tremors of 5.1 \(\times\) 10\({}^{7}\) J and 1.3 \(\times\) 10\({}^{6}\) J (Figures 2 and 5), followed by one rockburst event registered in December in Year 6, triggered by a tremor with magnitude 1.5 \(\times\) 10\({}^{8}\) J (Figures 3 and 5).