## 4 In Situ AE Monitoring in Gold Mines
### Gold Mine Mponeng in South Africa
The positions of cross sections I to IV are shown by magenta rectangulars. In Figure 17b the cross sections are presented the location of manual re-located AE events in a side-view. The PG dyke is shown by two grey lines. The re-located events reveal that the rupture plane started within the PG dyke, but reached the geological boundary, where branching and bending  
Figure 16: Sketch of the location of the JAGUARS network in the Møoneng gold mine and its surrounding geologic formations. The JAGUARS network is located at 3540 m depth. The sensors are located in boreholes, that are shown as bold black lines. The Pink-Green (PG) drive is shown in gray. The gold reef with active mining located above the JAGUARS network is shown in light gray. The mining stop width is 0.5 m to 1 m. The development tunnels XC45 and XC46 are shown in dark gray [52]. Reproduced with permission. occurred. Secondary features (marked with VII and IX) are observed that likely correspond to the rupture of major aftershocks. [PERSON] et al. [78] showed that the aftershock AE events clearly delineated a plane in the PG dike with a strike of N22W and a dip of 68\({}^{\circ}\) toward N68E (Figure 17). Because waveforms of the main shock recorded by the AE network were saturated in AE recordings, the main shock was analyzed using waveform data of the in-mine geophone network. [PERSON] et al. [74] were able to resolve the complexity of the rupture plane (approximately extension 100 m \(\times\) 80 m), which underwent branching and bending according to geological heterogeneities present. [PERSON] et al. [74] applied the master-event location technique to locate the hypocenter of the main shock relative to the aftershock AE events. The main shock hypocenter obtained was about 30 m above the AE network and on the aftershock plane. The focal mechanism solution of the normal fault for the main shock using seismic waveforms recorded by the seismic network operated by the mine pointed out that one of the nodal planes agreed well with the aftershock plane. Therefore, the aftershock plane is considered to correspond to the rupture plane of the main shock plane, which demonstrates clearly that the AE aftershock activity outlines the main shock's rupture plane. [PERSON] [79] show that the aftershocks occur in areas of positive Coulomb stress change as determined using rate and state based stress modeling. Source parameter analysis demonstrated that the aftershock AE event sequence has the same characteristics as tectonic aftershock events, i.e., they follow the Omori law [36], the Gutenberg-Richter distribution [55] and a static stress drop [16]. The magnitude ranges between \(-\)5.0 and \(-\)0.8. The magnitude of completeness varied strongly in space, but was estimated to \(M_{C}=-4.8\) in the network center [52]. Figure 17: Mainshock-Aftershock sequence from 27 December 2007 recorded by the JAGUARS network. The spatial distribution of 9,444 aftershocks is shown in map view in (**a**). These aftershocks comprise a subset of the 25,000 aftershocks recorded which come with small residuals of the automatic locations. The mainshock location is shown by a grey star. Red stars show the location of all aftershocks recorded by the in-mine geophone network. The event depth (shaft depth) is color-coded, which shows that aftershocks were triggered not only on rupture plane, but also at the slope face above the mainshock. The positions of cross sections I to IV are shown by magenta rectangulars. In (**b**) cross sections are presented that show the location of manual re-located AE events in side-view. The PG dyke is shown by two grey lines. The area of rupture initiation was subject to foreshock activity that is interpreted as the breakdown of asperities [78]. Interestingly, there are indications that AE events announce the main shock in advance. Figure 18a,b display the results of manual and automatic source location, respectively, applied to the same AE events, which are within 5 m of the aftershock surface.