Characteristics of Fault Rocks Within the Aftershock Cloud of the 2014 Orkney Earthquake (M5.5) Beneath the Moab Khotsong Gold Mine, South Africa

Abstract Cores recovered during the International Continental Scientific Drilling Program project “Drilling into Seismogenic zones of M2.0 to M5.5 earthquakes in deep South African Gold Mines” include fault breccia from within aftershock cloud 2014 Orkney earthquake (M5.5). The and surrounding intrusive rocks, probably lamprophyres rich talc, biotite, calcite, amphibole, had high magnetic susceptibilities owing presence magnetite. All these characteristics can be attributed fluid‐related alteration. Both low friction coefficients showed evidence velocity strengthening, which is inconsistent with occurrence earthquakes. Variable amounts amphibole might have produced complex frictional properties spatial heterogeneity stability. altered may host rocks earthquake, but complexity governed magnitudes main‐ aftershocks their distributions.