###### Abstract  
To explore the causes of mine tremors in coal mines with sandstone roofs, a three-point bending loading experiment was designed for composite sandstone layers, and the fracture and interlayer shear slip characteristics of the composite sandstone layers were studied using optical measurement and acoustic emission techniques. The results show that the bending of the rock layers led to interlayer sliding deformation, while the fracturing greatly promoted interlayer sliding. The maximum interlayer slip accelerations during bending deformation and fracturing were 0.6 mm/s\({}^{2}\) and 3.8 mm/s\({}^{2}\), respectively. During the fracturing of the rock layers, the proportion of acoustic emission shear fracture events increased with the continuous occurrence of long-lasting and high-amplitude acoustic emission events. The mechanism of mine tremors in thick sandstone roofs is as follows: the increase in the area of the goat causes rock bending deformation and fracturing, accompanied by interlayer shear slip, fracturing of the sandstone layer, and friction dislocation at the concentration surface of the adjacent sandstone layers, which jointly cause vibration of the roof. mining tremors; hard roof; interlayer shear slip; coalburst; fracturing +
Footnote †: journal: Medical Imaging  
0000-0001-882-2227-2271][PERSON]  
0000-0002-2270-3199][PERSON]  
0000-0002-2270-3222-3222-3222-32222-32222-32  
that occurred in Shenmu City, Shaanxi Province, on 14 October 2004. In the northern region of Shaanxi Province and the adjacent Ordos region, roof-type tremor events with magnitudes exceeding M\({}_{\text{L}}\) 2.0 occurred more than 20 times annually [9]. Although there are generally no casualties, these events have caused varying degrees of surface fissuring and house cracks and have even triggered underground coalbursts, leading to concerns among residents about safety in the mining area (Figure 2). This indicates that the prevention and mitigation of mine tremors are of undeniable significance for maintaining the natural ecology of the mining area, ensuring the safety of underground production, and safeguarding the well-being of residents. The mechanism of mine tremors is a hot topic in the field of rock mechanics. Compared to fault-type tremors, the mechanism of roof-type tremors is less clear. The former has a generation similar to that of natural earthquakes, and their occurrence is accompanied by the shear fracturing of the rock mass and stick-slip motion on faults. This has been confirmed by numerous experiments and field data collected by researchers [11; 12; 13]. It is inappropriate to attribute roof-type tremors solely to the fracturing of rock strata. This phenomenon frequently occurs during coal extraction as the rock strata reach their tensile stress limits especially when the rock strata are relatively hard. However, only a very small number of mines experience tremors. Undeniably, the regions where roof-type tremors occur commonly host rigid roofs, and the energy released by the tensile fracturing of these rigid roofs is considerable. This can sometimes lead to dynamic disasters such as coalbursts [14; 15; 16]. However, these dynamic disasters occur instantaneously and have a very short duration, contrasting significantly with the sensation felt by surface residents in the tremor areas, which can last for tens of seconds. For instance, on 7 December 2012, a mine tremor occurred in the goaf of the Changing Coal Mine in Yulin City, Shaanxi Province. Local residents described a sudden loud noise followed by a rumbling sound, accompanied by a sensation of the buildings beginning to sway. The recognition of the sensing of vibrations suggests that the mine tremor waveform had a prolonged duration and low frequency. The research on acoustic emissions associated with rock fracturing indicates that low rise time and high frequency are typical characteristics of tensile-type fractures, while shear-type fractures typically result in longer wave forms, longer rise times, and lower frequencies [17].