Note on fault-slip motion inferred from a study of micro-cataclastic particles from an underground shear rupture

Mining of a highly-stressed remnant in a deep South African gold mine was accompanied by considerable seismic activity and some significant rockbursts. The larger seismic events were registered some 60 km away at a WSSN station and several shear ruptures corresponding to these events were encountered during mining operations.A careful study based on detailed exploration of two of these ruptures proved them to be the source of two of the larger rockbursts.Certain striking features revealed by a scanning electron microscopic study of some of the fresh cataclastic rock-flour forming part of the comminuted filling of these ruptures provide strong evidence of violent shock rebound phenomena in the faulting process. This interpretation could provide useful insight into earthquake source mechanisms and also has practical significance in the understanding of mine rockbursts.