Mining-Induced Stress Transfer and Its Relation to a $$\text{M}_w$$ M w  1.9 Seismic Event in an Ultra-deep South African Gold Mine

Abstract

On 27 December 2007 a M w 1.9 seismic event occurred within a dyke in the deep level Mponeng gold mine, South Africa. From the seismological network of the mine and the one from the JAGUARS group, the hypocentral depth (3509 m), focal mechanism and aftershock location was estimated. Since no mining activity took place in the days before the event, dynamic triggering due to blasting can be ruled out as the cause. To investigate the hypothesis that stress transfer, due to excavation of the gold reef, induced the event, we set up a small scale (450 × 300 × 310 m 3) high resolution 3D geomechanical-numerical model. The model consists of the four different rock units present in the mine: quartzite (footwall), hard lava (hanging wall), conglomerate (gold reef), and diorite (dykes). The numerical solution is computed with a finite element method, with a discretised mesh of approximately 10 6 elements. The initial stress state of the model is in agreement with in-situ data from a neigh

Review on In Situ Acoustic Emission Monitoring in the Context of Structural Health Monitoring in Mines

“…The stress changes owing to the approaching mining front on the PG dyke are modeled by Ziegler [77]. A main shock with magnitude of M W = 1.9 occurred on 27 December 2007 in the center of the AE monitoring network [33,36,74].…”

“…Yabe et al [77] showed that the aftershock AE events clearly delineated a plane in the PG dike with a strike of N22W and a dip of 68° 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.…”

“…The area of rupture initiation was subject to foreshock activity that is interpreted as the breakdown of asperities [77]. Interestingly, there are indications that AE events announce the main shock in advance.…”

“…Gray contours show the areal density of the aftershocks drawn by feeding areal densities in 5 m× 5m cells. The thin black dashed contour indicates the aftershock area defined by Naoi et al [77]. The light blue solid circle is the access tunnel along which the observation network was deployed.…”

A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin

“…The stress field also provides critical a priori information for safe and sustainable underground engineering such as wellbore planning and stability, reservoir management, tunnelling, mining, and underground waste storage (Altmann et al, 2014;Cornet et al, 1997;Fuchs and Müller, 2001;Moeck and Backers, 2011;Tingay et al, 2008;Zang et al, 2013;Ziegler et al, 2015;Zoback, 2010). The quantification of the criticality of the in situ stress state in terms of fault reactivation in advance of any underground treatment is essential for identifying areas of low criticality for safe and efficient utilization of the subsurface (Hornbach et al, M. O. Ziegler et al: Multi-stage 3-D stress modelling 2015; Zoback et al, 1985;Häring et al, 2008;Kohl and Mégel, 2007).…”