Projected inundations on the South African coast by tsunami waves

W Van Zyl,Hc Cawthra

doi:10.4314/sajg.v4i2.4

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.

Highlights

Tsunamis are waves generated by the large and sudden forced displacement of the seafloor, with characteristics intermediate between tides and swell waves (Løvholt et al, 2009)
Waves generated by rapid displacement along submarine faults are referred to as tsunamis generated by remote submarine seismicity and these are the most devastating (NGDC, 2011)
The work presented in this paper presents the results of a pilot study to identify vulnerable coastal areas to tsunami inundation in South Africa and a simple, reproducible methodology

Summary

Introduction

Tsunamis are waves generated by the large and sudden forced displacement of the seafloor, with characteristics intermediate between tides and swell waves (Løvholt et al, 2009). The Ceres-Kango-Baviaanskloof-Coega fault forms part of the Ceres-Baviaanskloof-St. Croix (CB-S) fault system, which traverses the Cape Fold Belt and extends offshore as the St Croix fault, joining the Agulhas-Falklands Fracture Zone (AFFZ) (Goedhart et al, 2007). Croix (CB-S) fault system, which traverses the Cape Fold Belt and extends offshore as the St Croix fault, joining the Agulhas-Falklands Fracture Zone (AFFZ) (Goedhart et al, 2007) Holocene faulting in this region suggests that the entire southern coast could be considered vulnerable to future seismic events (Goedhart et al, 2007)

Objectives

Methods

Conclusion