Mining-induced earthquakes pose a risk to workers in deep mines, while large earthquakes that occur near plate boundaries (and occasionally in stable continental regions) pose a risk to the public. A five-year Japanese–South African collaborative project’Observational studies in South African mines to mitigate seismic risks’ was concluded in 2015. Acoustic emission sensors, accelerometers, strain meters, and controlled seismic sources were installed in three deep Witwatersrand gold mines to monitor the deformation of the rock mass, the accumulation of damage during the earthquake preparation phase, and the propagation of the rupture front. A surface array of accelerometers was installed in the Far West Rand mining district. This data was integrated with measurements of stress, in-stope closure, and strong motion, as well as data recorded by the mine-wide seismic networks. New insights into the physics of earthquakes were gained, and technologies developed or adapted to assess seismic hazard and mitigate rockburst risks.