Rupture processes and magnitude statistics of inducedearthquakes and aftershocks: A detailed view from deepSouth African gold mines

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Despite our general understanding of earthquake processes, it is still not fully understood how earthquakes ruptures nucleate and propagate and why they stop. Furthermore, the controlling factors of the frequency and the size of earthquake are subject of ongoing research. In our proposal, we aim to address these questions with a comprehensive study of seismicity in deep South African gold mines. Here, we find the unique situation that the seismicity consists of both mining-induced earthquakes and triggered aftershocks. We hypothesize that the finiteness and geometry of the volume of stress perturbation, either by mining activity or by a main shock, controls the nucleation and propagation of ruptures and influences the frequency-magnitude distribution. To test our hypothesis, we will apply novel approaches to the seismicity from the deep mines which involve both waveform-based and probabilistic methods. These methods were recently elaborated and successfully applied to fluid injection induced earthquakes and include rupture propagation imaging, rupture directivity analysis, and studies of the scaling of the magnitude statistics. In this proposal, we want to test the applicability of these approaches to the seismicity in deep South African mines, which also occurs in a finite volume, which will contribute to a better understanding of seismogenic processes and, in particular, to an improved assessment and the mitigation of seismic hazard in mining environment.