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Abstract

The current seismo-tectonic model for South Africa depicts the south-eastern Cape Fold Belt as a tectonically stable intraplate-type environment, where earthquakes are relatively infrequent to rare, particularly large surface-rupturing events. The closest surface rupture recorded by the SANSN, which underpins the model, is the extensional Mozambique 7.2M event on 22 February 2006, related to southward propagation of the East African Rift. A similar 84km-long extensional surface rupture has been found along the Kango fault within the southern Cape Fold Belt, 50km east of Oudtshoorn. Optically stimulated luminescence dating indicates it occurred around 10,620 ± 509, at the start of the Holocene. This fault, together with the adjoining Baviaanskloof and Coega faults, and other nearby adjacent faults, is the subject of a palaeoseismic investigation to determine the Quaternary tectonic history of the south-eastern continental margin. This region of South Africa has little seismic information, and the record is too short to include the long recurrence intervals of large, surface damaging earthquakes typical of intraplate regions. The data reported includes the location and extent of the surface rupture, the local stress direction, the date and magnitude of the most recent event, the minimum recurrence interval, and maximum slip rate. The earthquake environmental effects are also evaluated according to the new Environmental Seismic Intensity Scale (ESI 2007), to provide an independent assessment of seismic intensity. A potential local tectonic driver, the Cape Isostatic Anomaly (CIA) is also discussed, as well as a possible trigger mechanism leading to the rupture. Results should facilitate PSHA of several new critical facilities planned for the province.

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/content/papers/10.3997/2214-4609-pdb.241.goedhart_paper
2009-09-16
2022-12-01
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.241.goedhart_paper
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