## 2 Geological Setting and Data  
### Formation and Mining Condition  
LW 1208 is arranged on the east side of LW 1206A, located in the south wing of the 12 th panel area of the mine. The main mining is of 2-2 coal with a thickness of 8.51-9.51 m and an average of 9.08 m. The geological conditions of the coal seam are simple, and the mining depth is 640-711 m. As shown in Figure 1, the LW 1206A is to the north of LW 1208. The stopping lines of the two LWs are aligned and the length of the open cut of both faces is 290 m, and 5 m narrow coal pillars are set. LW 1206A, with a strike length of 1120 m, was completed in October 2019. In May 2021, LW 1208 entered into mining near the goat. By 20 December 2021, 2509 m had been mined. The stopping location is 398.2 m above the front of the 1206A open-off cut, with 734.15 m remaining.  
Several microseismic sensors are located in LW 1208, which can record the waveform information of mining tremors induced in LW 1208 in real time. Three detection holes are placed in the face to detect the separation of strata as the face is mined. The line of strata movement is used to monitor surface subsidence characteristics.  
SMTs occurred on 20 August 2021, 29 August 2021, and 20 December 2021 in the goat mining phase of LW 1208, causing ground tremors. For simplicity, SMTs are named after their date of occurrence, such as \"8.20\" SMT. The basic information on the SMTs is briefly described in Table 1.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Time of Occurrence** & **Panel Position** & **Source Location** & **Energy/J** & **Magnitude** & **Field Survey Condition** \\ \hline
20 August 2021 & 289.9 m in front of 06A & 218 m behind the panel & & & \\
17:41:51 & open-off cut & position of LW 1208 and & 5.56 \(\times\) 10\({}^{5}\) & 2.40 & (1) There was no obvious \\  & & 179.8 m behind the tail entry. & & & vibration in the underground and \\
29 August 2021 & Same as above & 264.6 m behind the panel & & & no deformation in the roadway; \\
00:41:41 & (stoppage of LW 1208) & position of LW 1208, and & 1.69 \(\times\) 10\({}^{5}\) & 2.80 & (2) The ground shook slightly, and \\  & & 57.2 m behind the head entry. & & & building facilities on the ground \\ \hline
20 December 2021 & 398.2 m in front of 06A & 70.3 m behind the panel & & & (3) No loss of personnel or \\
17:03:15 & open-off cut & position of LW 1208, and & 2.92 \(\times\) 10\({}^{5}\) & 2.60 & property. \\  & & & head entry. & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Basic information of three SMTs in LW 1208.  
Figure 1: Layout of LW1208 and plane location of SMTs.  
According to the geological borehole information, the overlying strata structure on the working surface of 1208 can be drawn (seen in Figure 2). The Lower Cretaceous Zhidan Group consists of several thick sandstones, while the middle Jurassic Anding and Zhiluo formations are composed of sandstone, sandy mudstone, and interbedded mudstone. The Middle Yan'an Formation of the Jurassic system is a coal-bearing layer, and the part of the layers from the coal seam to the Zhiluo Formation are mainly sandy mudstone and mudstone.  
The thickness of the Cretaceous super-thick strata is about 300 m, and the rupture movement of the super-thick strata can cause dynamic disasters such as SMTs and rock bursts during mining. In addition, due to the thin surface soil thickness of LW 1208, the attenuation of the seismic wave is slow after the SMT induced by the fracture movement of the super-thick Cretaceous strata, which easily causes ground tremors.