Rupture Directivity of Earthquakes below Gold Mines in South Africa

Induced seismicity is a growing research topic all over the world causing significant damage. Here, we work with seismicity which occurred below a gold mine in Orkney, South Africa. The largest earthquake occurred in a region that has been tectonically stable for the past two billion years ( Moyer et al., 2017 ) on 5 August 2014 and had a local magnitude of 5.5. In-mine as well as surface data of three-component seismometers with a sampling rate of 6 kHz are provided by AGA (AngloGold Ashanti Ltd.) and CGS (Council for Geoscience) in South Africa, respectively. We will will use the data of the in-mine network to track the rupture process using P-wave Polarization Analysis. This method is based on time dependent particle motion estimated during the propagating rupture which leads to different incident angles at a station.

The in-mine network provides an enhanced signal-to-noise ratio resulting in a remarkable quality of the data. A southeast propagation of the rupture front for approximately 1.5 seconds is visible on the E-N particle motion hodogram. The combination with other rupture imaging methods will lead to an estimation of rupture properties such as direction, speed and duration.