TY  - JOUR
A1  - Ziegler, Moritz O.
A1  - Reiter, Karsten
A1  - Heidbach, Oliver
A1  - Zang, Arno
A1  - Kwiatek, Grzegorz
A1  - Stromeyer, Dietrich
A1  - Dahm, Torsten
A1  - Dresen, Georg
A1  - Hofmann, Gerhard
T1  - Mining-Induced Stress Transfer and Its Relation to a 1.9 Seismic Event in an Ultra-deep South African Gold Mine
JF  - Pure and applied geophysics
N2  - On 27 December 2007, a 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 Japanese-German Underground Acoustic Emission Research in South Africa (JAGUARS) group, the hypocentral depth (3,509 m), focal mechanism and aftershock location were 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 high-resolution three-dimensional (3D) geomechanical numerical model. The model consisted 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 was computed using a finite-element method with a discretised mesh of approximately elements. The initial stress state of the model is in agreement with in situ data from a neighbouring mine, and the step-wise excavation was simulated by mass removal from the gold reef. The resulting 3D stress tensor and its changes due to mining were analysed based on the Coulomb failure stress changes on the fault plane of the event. The results show that the seismic event was induced regardless of how the Coulomb failure stress changes were calculated and of the uncertainties in the fault plane solution. We also used the model to assess the seismic hazard due to the excavation towards the dyke. The resulting curve of stress changes shows a significant increase in the last in front of the dyke, indicating that small changes in the mining progress towards the dyke have a substantial impact on the stress transfer.
KW  - Induced seismicity
KW  - static stress change
KW  - deep-level mining
KW  - tabular mining
KW  - Coulomb failure stress
KW  - 3D geomechanical numerical model
Y1  - 2015
U6  - https://doi.org/10.1007/s00024-015-1033-x
SN  - 0033-4553
SN  - 1420-9136
VL  - 172
IS  - 10
SP  - 2557
EP  - 2570
PB  - Springer
CY  - Basel
ER  -