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Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa
Despite being in a stable continental region (SCR), South Africa has experienced significant seismic activity. Historical records cite a possible 6.5 magnitude earthquake in Cape Town in 1809. On September 29, 1969, a 6.3 magnitude earthquake struck the Ceres-Tulbagh region, less than 100 km from th...
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| Format: | Thesis |
| Language: | English English |
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Department of Geological Sciences
2026
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| _version_ | 1867613184020447232 |
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| access_status_str | Open Access |
| author | Van Zyl, Wade |
| author2 | Quiros, Ugalde Diego |
| author_browse | Quiros, Ugalde Diego Van Zyl, Wade |
| author_facet | Quiros, Ugalde Diego Van Zyl, Wade |
| author_sort | Van Zyl, Wade |
| collection | Thesis |
| description | Despite being in a stable continental region (SCR), South Africa has experienced significant seismic activity. Historical records cite a possible 6.5 magnitude earthquake in Cape Town in 1809. On September 29, 1969, a 6.3 magnitude earthquake struck the Ceres-Tulbagh region, less than 100 km from the Koeberg Nuclear Power Station (KNPS) in Cape Town. Previous studies have found a relationship between enhanced micro-seismicity over long periods and source zones of historical SCR earthquakes. This thesis seeks to identify heightened micro-seismic activity on regional fault structures to infer potential source zones for the 1809 event and future damaging earthquakes. To achieve this, eighteen three-component geophones were deployed across a 40 by 35-kilometre area near the KNPS. The geophones recorded data from August to October 2021 and were located near the Ceres-Tulbagh region, Cape Town, the proposed Milnerton fault, and the Colenso fault zone. Seismicity around these fault zones was analyzed using machine learning, visual inspection, and Short-Time Average to Long-time Average (STA/LTA) algorithms. Thirty-five events were found, categorized into two groups of elevated seismicity: one group was located offshore, outside the study area, while the other was situated between the proposed Milnerton fault and the Colenso fault system. Within the second group, the Colenso fault system shows elevated micro-seismicity, indicating that it is potentially active. Additional findings suggest that machine learning and visual examination of waveform data are more accurate than STA/LTA algorithms combined with manual assessment at detecting micro-seismic phases and consequently events. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/42748 |
| institution | University of Cape Town (South Africa) |
| language | English eng |
| last_indexed | 2026-06-10T12:32:06.010Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Department of Geological Sciences |
| publisherStr | Department of Geological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/42748 Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa Van Zyl, Wade Quiros, Ugalde Diego Sloan, Alastair earthquake Cape Town South Africa Despite being in a stable continental region (SCR), South Africa has experienced significant seismic activity. Historical records cite a possible 6.5 magnitude earthquake in Cape Town in 1809. On September 29, 1969, a 6.3 magnitude earthquake struck the Ceres-Tulbagh region, less than 100 km from the Koeberg Nuclear Power Station (KNPS) in Cape Town. Previous studies have found a relationship between enhanced micro-seismicity over long periods and source zones of historical SCR earthquakes. This thesis seeks to identify heightened micro-seismic activity on regional fault structures to infer potential source zones for the 1809 event and future damaging earthquakes. To achieve this, eighteen three-component geophones were deployed across a 40 by 35-kilometre area near the KNPS. The geophones recorded data from August to October 2021 and were located near the Ceres-Tulbagh region, Cape Town, the proposed Milnerton fault, and the Colenso fault zone. Seismicity around these fault zones was analyzed using machine learning, visual inspection, and Short-Time Average to Long-time Average (STA/LTA) algorithms. Thirty-five events were found, categorized into two groups of elevated seismicity: one group was located offshore, outside the study area, while the other was situated between the proposed Milnerton fault and the Colenso fault system. Within the second group, the Colenso fault system shows elevated micro-seismicity, indicating that it is potentially active. Additional findings suggest that machine learning and visual examination of waveform data are more accurate than STA/LTA algorithms combined with manual assessment at detecting micro-seismic phases and consequently events. 2026-01-29T08:51:52Z 2026-01-29T08:51:52Z 2025 2026-01-29T08:49:10Z Thesis / Dissertation Masters MSc http://hdl.handle.net/11427/42748 en eng application/pdf Department of Geological Sciences Faculty of Science University of Cape Town |
| spellingShingle | earthquake Cape Town South Africa Van Zyl, Wade Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| thesis_degree_str | Master's |
| title | Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| title_full | Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| title_fullStr | Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| title_full_unstemmed | Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| title_short | Investigating seismicity in Cape Town: implications for active fault lines in the Western Cape, South Africa |
| title_sort | investigating seismicity in cape town implications for active fault lines in the western cape south africa |
| topic | earthquake Cape Town South Africa |
| url | http://hdl.handle.net/11427/42748 |
| work_keys_str_mv | AT vanzylwade investigatingseismicityincapetownimplicationsforactivefaultlinesinthewesterncapesouthafrica |