Speaker: Gerrie van Aswegen
The Dagbreek fault yielded the first major mining-induced earthquake in Welkom in 1976. It failed again in 1988 and the last time in 1999 – the last one being the Matjhabeng earthquake. The latter is described in terms of the seismic gap remaining after the first two earthquakes and also in terms of some precursory activity and the possible triggering affect of a mine fire at the time. The Brand fault failed in 1989 – a textbook example of how to make an earthquake. The Stuirmanspan earthquake in 1990 showed the practical application of apparent stress as a spatial indicator of the future earthquake source.