Projected inundations on the South African coast by tsunami waves

Abstract

Historical and recent evidence recorded along the South African coast suggests that five tsunami events have occurred since 1960. These were mostly associated with trigger mechanisms associated with sources of remote submarine seismicity along far-field subduction zones and local atmospheric disturbances (meteotsunami). The passive margin of the South African West Coast, and the broad Agulhas Bank spanning the South- and Southeast coasts, have contributed to an increased susceptibility to inundation of waves in the adjacent low-lying coastal areas in these regions. In the published models and empirical studies for South Africa, the bathymetry and orientation of Port Elizabeth Bay is seen to amplify effects of a tsunami wave. Other regions including the Cape Town and St Helena Bay areas are also vulnerable to coastal inundation through the data generated in this study. The methodology presented here provides a simple means of determining the susceptibility of coastal areas to significant inundation by far-field tsunamis.