The CGS developed a microzonation model for the City of Johannesburg
The CGS developed a microzonation model for the City of Johannesburg, including those areas triggered by the abandoned and flooding mines. The objective of this model is to assist the mitigation of possible earthquake damages. The microzonation is a process where seismic hazards are identified at different locations within a geographical area and is essential for identifying potential seismic “hotspots”, which could affect critical structures, for example, bridges, elevated highways, subways, sky trains, dam sites (including tailings dams from the mines), and many more.
Quite a number of large cities around the world, including those in regions of low to moderate natural seismicity, such as South Africa, have put some effort into developing microzonation models for better understanding of the earthquake hazards within major cities. The CGS is now concentrating on the cities within Kwa-Zulu Natal and will hopefully cover most of the cities within the country with these intergrated multi-disciplinary models.
Each of the microzonation projects include the following tasks :
- Geological Setting Investigations,
- Preparation of the PSHA inputs,
- PSHA Calculations & Post processing to prepare Response Spectrum,
- Collection and analysis of borehole data, and
- Field Measurements to obtain shear wave velocity profiles and ambient noise vibrations