Seismotectonic Models for South Africa: Synthesis of Geoscientific Information, Problems, and the Way Forward

Singh, Mayshree; Kijko, Andrzej; Durrheim, Raymond

doi:10.1785/gssrl.80.1.71

Cited by 29 publications

(18 citation statements)

References 11 publications

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“…2013), areas/zones of induced seismicity in the gold mining region (e.g. Singh, 2009) and seismic swarms Guzman, 1979 andAkromah, 2013), together with the position of prominent sources of explosions associated with opencast mines identified from the South African Mineral Deposits Database (SAMINDABA, 2014), is shown as Figure 2.…”

Section: Seism Icitymentioning

confidence: 99%

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Statistical evaluation of seismic event location accuracy by the South African National Seismograph Network over four decades

Saunders

Kijko

Fourie

2016

South African Journal of Geology

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© 2 0 1 6 M arch G eo lo g ica l S o ciety o f Sou th A frica A b stractWe analyzed the changes/improvements of seismic event detection and location accuracy of the South African National Seismograph Network over the last four decades. The effect of three regional velocity models on epicentral solutions was tested during the initial study. It is shown that the hypocentral depth considered during this study, viz. at 2 km for mining related events, and 5 km to 10 km for tectonic earthquakes, have a negligible effect on the error in epicentre location. Further, three detection distances were evaluated during this study, viz. 300, 500 and 1000 km. The location errors decreased significantly by increasing the detecting distance. This study highlights the importance of including 5-phase arrival times to better constrain seismic event locations. This observation is of particular value for the 1970 to 1997 period, when only P-phases were considered during the location procedure. Lastly, it is shown how the errors in epicentre location decrease with an increase in the number and geographical distribution of seismic stations.

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Section: Seism Icitymentioning

confidence: 99%

“…The polygons with stippled outlines define the extent o f the Sutherland swarm 13, (Fernandez and Guzman, 1979), Lesotho-South African border swarm 14, (Fernandez and Guzman, 1979) and the Augrabies swarm 15, (Akromah, 2013). The hatched polygon defines the gold mining region (Singh et al, 2009)…”

Section: Seism Icitymentioning

confidence: 99%

Statistical evaluation of seismic event location accuracy by the South African National Seismograph Network over four decades

Saunders

Kijko

Fourie

2016

South African Journal of Geology

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“…An intraplate sinistral strikeslip earthquake with local magnitude (M L ) 6.3 occurred near the towns of Ceres and Tulbagh in the Western Cape, South Africa, on 29 September 1969 (Green and Bloch, 1971;Green and McGarr, 1972;Krüger and Scherbaum, 2014). To date this is the largest instrumentally recorded earthquake in South African history, and the towns of Ceres and Tulbagh have continued to experience regular seismicity of M L > 3 after 1969 (Singh et al, 2009;Saunders et al, 2012). We first review the geology and tectonic history of this area, before we consider the 1969 earthquake and its aftershocks.…”

Section: Introductionmentioning

confidence: 99%

Microseismic Activity and Basement Controls on an Active Intraplate Strike‐Slip Fault, Ceres–Tulbagh, South Africa

Smit

Fagereng

Braeuer³

et al. 2015

Bulletin of the Seismological Society of America

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Earthquakes far from plate boundaries are poorly understood, because of few well-studied examples and uncertainty of what controls the location of these events. In 1969 a damaging local magnitude (M L ) 6.3 strike-slip earthquake, with no surface expression, occurred in the Ceres-Tulbagh region in the South African stable continental interior. Here, we present a microseismic study of the Ceres-Tulbagh area, conducted over three months in 2012, in which 172 events recorded on at least three stations follow a Gutenberg-Richter relationship for −1:5 < M L < 0:5. The events delineate a 5 km wide, subvertical zone that is microseismically active to a depth of 15 km. This fault zone is subparallel to the 1969 aftershock zone and at low angle to the regionally inferred greatest horizontal stress. We argue that the microseismically active zone is guided by inherited structures in the basement geology. This and similar structures may represent significant earthquake hazard in plate interiors.Online Material: Tables of station and event parameters, and P-and S-wave arrival times.

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“…The event occurred on 29 September, 1969 in the Ceres-Tulbagh region of the Western Cape Province about 100 km northeast of Cape Town. Serious damage occurred to buildings in the area (valued at a total of U.S. $24 million) (Singh et al, 2009). The structural damage to buildings varied from almost total destruction of old and poorly constructed buildings to large cracks in better designed and built structures ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…The structural damage to buildings varied from almost total destruction of old and poorly constructed buildings to large cracks in better designed and built structures ( Figure 1). Twelve people were killed and many more injured (Singh et al, 2009). Other large events of tectonic origin felt in South Africa include the 1912 Koffiefontein earthquake of magnitude 6.2, the 31 December 1932 Cape St Lucia earthquake of local magnitude 6.…”

Section: Introductionmentioning

confidence: 99%

Comparison and Quantitative Study of Vulnerability/Damage Curves in South Africa

Pule

Fourie

Kijko

et al. 2015

South African Journal of Geology

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Southern Africa is considered a stable continental region in spite of several reported medium size earthquakes, some of which caused considerable damage and casualties. The 1969 Ceres 6.3 magnitude earthquake is considered the most destructive and caused serious damage estimated at US$24 million, with 12 mortalities and many more injured. Others include six mining related tremors which caused significant damage i.e. Welkom 1976, Klerksdorp 1977, Welkom 1989 and Carletonville 1992 Most buildings and structures in South Africa are not designed to resist even relatively low intensity earthquake. Most architects, engineers and builders in South Africa do not consider seismic resistance as a design requirement. In this work, potential damage caused by strong earthquake was estimated for three classes of buildings situated in Sandton, Cape Town, Durban and Port Elizabeth. The effect of earthquakes causing damage was studied by considering the "worst case-scenario", i.e. the occurrence of an earthquake with the maximum possible magnitude for an area. In four studied urban areas, expected damage was estimated for three classes of buildings: unreinforced masonry, bearing wall, low rise, reinforced concrete shear wall, without moment resisting frame, medium rise, and reinforced concrete shear wall, without moment resisting frame, high rise. The results of the analysis showed that in case of occurrence of a strong earthquake, the most damage is expected for the building classified as 'unreinforced masonry, bearing wall, low rise, and reinforced concrete shear wall'.

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Seismotectonic Models for South Africa: Synthesis of Geoscientific Information, Problems, and the Way Forward

Cited by 29 publications

References 11 publications

Statistical evaluation of seismic event location accuracy by the South African National Seismograph Network over four decades

Statistical evaluation of seismic event location accuracy by the South African National Seismograph Network over four decades

Microseismic Activity and Basement Controls on an Active Intraplate Strike‐Slip Fault, Ceres–Tulbagh, South Africa

Comparison and Quantitative Study of Vulnerability/Damage Curves in South Africa

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