# Microseismic Electronic Fencing for Monitoring of Transboundary Mining in Mines
## 3 Measured Data Analysis  
To evaluate the effectiveness of the nested microseismic observation system proposed in this paper for monitoring transboundary mining activities, a tunnel of Huangshajie on the Guanzhuang-Xinhua Expressway in Hunan Province, which is under excavation, was selected to carry out the relevant experimental research. The left line of Huangshajie Tunnel is 4354 m long, the maximum depth of the left line is 463.200 m, and the maximum depth of the right line is 471.200 m. The test section is located between K13 + 600 and K13 + 900, with the maximum depth of the station from the tunnel being 400 m, and the minimum depth 300 m and the difference in the height of the station being 200 m. The stratigraphic distribution of the area through which the tunnel passes is relatively simple, with most of the Quaternary overburden less than 2 m, and the lower bedrock is sandy slate of the Wuqiangxi Group (Ptbn2w) of the Banxi Group and sandy slate of the Lower Aurignacian System (Za), and there are fractured slates in local tectonically developed areas. Sixty  
Figure 5: Layout and localization results for different numbers of sensor arrangements (the small red triangle in (**a**,**c**) is the surface sensor, the small blue triangle is the well sensor, and the green sphere is the event): (**a**) 39 sensors (**b**) localization results for 6–39 sensors (**c**) 15 sensors (**d**) localization results for 15 sensors.  
SmartSolo IGU-16 HR 3C seismic sensors (SmartSolo Scientific, Calgary, AB, Canada) were deployed for this test, and their planar distribution is shown in Figure 6a, with a station distribution radius of about 500 m. The recording time was from 10 July 2022 to 25 July 2022 for a total of 15 days. A total of 167 events were selected from the blast vibration records acquired by the seismographs, and Figure 6b shows the waveform record of one of the events, from which the initial value is clearer.  
Firstly, the nested observation system with 9, 15, and 26 stations were selected from the 60 stations deployed for the localization analysis, which was used to test the localization accuracy of the system with different numbers of stations. The velocity model required for localization was measured by means of shot-hole correction (with the location of the blast point known) and the average wave velocity in the survey area was calculated to be approximately 3700 m/s. The localization method adopts a simplex algorithm, and the initial depth location of the seismic source is set to 300 m. The localization results show that the localization error of the blasting event is around 50 m\(\sim\)60 m when the number of stations is 9 and 15; when the number of stations is increased to 26, the localization error reaches around 15 m\(\sim\)20 m (which includes the velocity model as well as the first-arrival pickup error), and there was no longer a large improvement in the localization error using all 60 stations compared to that of the nested observation system of 26 stations.  
Figure 7 illustrates the results of using these 26 stations to locate all the events. It can be observed that the distribution of the localized microseismic events is roughly linear (as shown in Figure 7b), and the location of this 'line' corresponds closely to the location of the tunnels. Therefore, it can be determined that the microseismic events located are the blasting events at different locations during the excavation of the tunnel. The results of this analysis further demonstrate that the nested observation system designed in this paper can effectively monitor mining and excavation activities in underground target areas. Consequently, it can be more effectively applied to regulate transboundary mining operations.  
Figure 6: Live view of station layout and vibration signal recording: (**a**) live view (**b**) vibration recording.