# Detection of Rock Mass Defects Using Seismic Tomography
###### Abstract  
Elastic wave tomography is a non-destructive technique used to obtain velocity images of internal structures. Wave velocity tomography has been used to quantitatively describe abnormal structures and identify boundaries in different media and shapes. This research aims to quantitatively describe anomalous structures on a laboratory scale and identify boundaries in different media and shapes. Wave velocity tomography technology was applied to non-empty and empty anomalous areas, and the accuracy of the resulting velocity images was quantified. The reliability of boundary recognition was studied and analyzed. The accuracy of the results was found to relate to the size and shape of the anomalous structures estimated in the prior model, as well as the wave velocity difference between the anomalous and normal regions. In practical engineering, when the presence of abnormal areas cannot be determined, a completely homogeneous prior model is used. The results indicate that, although the inversion velocity may not be accurate, it is sufficient to identify boundaries. The larger the velocity difference, the clearer the boundary to be recognized. Furthermore, to assess the practical efficacy of this physical detection method, the wave velocity tomography technology was used to detect hidden goats within a tantalum-niobium mine belonging to the Hunan Fuguihengton Mining Company. Utilizing physical detection, 12 potential goats and 100 confirmed goats were identified within the mine, demonstrating the efficacy of the proposed empty anomalous area detection methodology in accurately identifying and delineating the boundaries of hidden goats. elastic wave tomography; wave velocity imaging; detection of rock mass defects; goat 202515238  
22 January 202511 December 202422 January 202511 December 202422 January 2  
to study micro-crack development (e.g., [5; 6; 7; 8; 9]), identify the location of defects (e.g., [10; 11; 12; 13]), and validate numerical simulations (e.g., [14; 15; 16]). Compared to acoustic emission (AE) technology, which is also widely used for the non-destructive testing of internal defects in rock masses, seismic tomography primarily relies on recording the propagation velocity and attenuation characteristics of seismic waves (typically P-waves and S-waves) in geotechnical media. By recording reflected or refracted waves from multiple seismic sources and receivers, it allows for the inversion of subsurface structural features. In contrast, AE is an active monitoring technique, typically used to detect small-scale damage or stress concentration areas within rock masses or structures, focusing on localized dynamic events within materials rather than constructing an image of the entire subsurface structure [17]. Although there are differences in principles and applications, the combination of both methods enables more comprehensive non-destructive testing of internal defects in rock masses in geotechnical engineering. In 1993, [PERSON] et al. [5] combined tomographic difference imaging and acoustic emission techniques. They proved that the combination of these methods is useful for evaluating induced damage in rock. [PERSON] et al. (2011) [8] used this combination to monitor brittle failure initiated by water injection. Velocity imaging and injected volume measurements confirmed the close relationship between the water front and the induced AE cloud. To understand the physical mechanisms governing CO\({}_{2}\)-water replacement, [PERSON] and [PERSON] (2009) [10] carried out seismic measurements in porous sandstone under laboratory conditions. They confirmed that, when employed with differential arrival times and relative amplitudes determined from the cross correlation of waveforms, the difference tomography method can efficiently image changes in velocity and attenuation associated with the partial replacement of water. To better understand rock fracture and fault instability driven by high-pressure fluid sources, [PERSON] et al.