Council For Geoscience Research Articles

Comparison of sinkhole size versus borehole hazard classification

Sinkholes are a common occurrence on dolomitic land in South Africa. Different methods have been used in the past to classify the risk of sinkhole occurrence. The inherent hazard classifications (IHC) of boreholes are compared in this article to actual sinkhole occurrences. The national sinkhole database and the ENGEODE database of boreholes, both belonging to the Council for Geoscience (CGS), were used for this comparison between the IHC of the borehole and the size of the sinkhole that occurred within a 50 m radius. Thus, the sinkholes in the database were used for this comparison that had a borehole located within 50 m from the sinkhole. Four regions were identified and described separately, namely the Far West Rand, the Tshwane and Ekurhuleni Municipalities as separate areas, and the fourth group as the Johannesburg and Sedibeng Municipalities and the Mpumalanga, North West and Northern Cape Provinces. Although a very high percentage has been underestimated (ranging from 42% to 59% for the different regions), there is a relatively good IHC correlation between the hazard classification of the boreholes and the sinkholes (between 56% to 67%). Another problem is that an IHC of 1 to 4 (low to medium risk) was assigned to the boreholes in 17% to 29% of the cases for the different areas, yet sinkholes still formed. These areas are more problematic, since the risk from the drilling has been underestimated. The current methodology to classify boreholes has not proved to be one hundred percent accurate to predict the size of the sinkhole for the area, and several factors have been highlighted that should be taken into account when boreholes are classified. Further research needs be carried out around the discrepancies between the IHC of boreholes compared to actual sinkholes.

Evolution of Geotourism in Australia from Kanawinka Global Geopark and Australian National Landscapes to GeoRegions and Geotrails: A Review and Lessons Learned

The geological heritage of Australia’s landscapes and World Heritage areas has generally been underpromoted to the public by the tourism industry. However, in 2008, the fledgling world of geotourism in Australia received a significant boost with two events: the Inaugural Global Geotourism Conference ‘Discover the Earth beneath our Feet’ held in Fremantle, Western Australia, and the declaration of the UNESCO Kanawinka Global Geopark, which linked volcanic regions in South Australia and Victoria. Simultaneously the Australian Federal Government launched the ‘Australian National Landscapes’ (ANL) program. However, this impetus was not sustained when the Kanawinka Global Geopark was deregistered as a UNESCO-branded geopark in 2012, and the ANL program faded within a decade. Despite these setbacks, as an outcome of the 2008 Fremantle conference, several productive lines of geotourism have developed across Australia. This paper reviews the history of Australian geotourism since 2008. It examines the impacts of the experiences, lessons learned, problems for geology as perceived by National Parks and the Environment movement, geological communication problems, and the subsequent evolution of Australian geotourism. From these issues, new non-government bodies and initiatives have arisen, including the Australian Geoparks Network, the Australian Geoscience Council, and the recent development of a National Geotourism Strategy. Strong elements emerging from these initiatives are the increasing development of geotrails (which suit the large Australian continent) and the new Australian concept of ‘GeoRegions’. These are in response to an awareness that geotourism requires a flexible outlook to widen the appreciation and appeal of geological heritage and landscapes to the broader public. A further new direction is suggested: for Australian geotourism to combine with some elements of ICOMOS Cultural Routes. An outstanding example, the ICOMOS Overland Telegraph Line (OTL) Cultural Route that crosses Australia from south to north, is considered. For 2000 km, the construction of this line in the 1870s followed the regional geology and hydrology, relying upon the available biota but bringing about a clash of human cultures. The six colonies of Australia were finally linked to the world by wire, but the arrival of the OTL had a significant impact on the country’s Indigenous inhabitants. In Australia and globally, geotourism is incorporating the A–B–Cs (abiotic, biotic and cultural elements) to more effectively encourage the public to value their landscapes and the associated stories. The OTL provides an example of a newly introduced fourth dimension for geotourism, which gives consideration to the socio-political context of landscape adaptation.

Exploring strategies for management of disasters associated with illegal gold mining in abandoned mines: A case study of Ekurhuleni Metropolitan Municipality.

Due to many abandoned mines that are not rehabilitated, there will be illegal mining. Although the mining industry and government continue to prevent illegal gold mining in abandoned mines by sealing open shafts, it is not possible to close all the shafts at once due to limited resources. Furthermore, after sealing the shafts, illegal miners often create alternative openings to enter underground workings while little or nothing is being done to stop the surface illegal gold mining. As long as illegal gold mining is there, disasters associated with illegal mining are prevalent. Effective disaster preparedness and response requires a competent strategy. The purpose of this study was to develop a strategy that can be used for emergency preparation and rescue efforts associated with disasters caused by abandoned mines and illegal gold mining. In this qualitative study, semi-structured interviews were held with officials and experts on disaster management from the Council for Geoscience and the City of Ekurhuleni. This study indicates that the safety of illegal miners and communities near abandoned mines depends on several factors including the ability to identify and respond to a disaster. The study identified three interlinked themes within the report as strategies for dealing with disasters related to abandoned mines and illegal gold mining. These themes included emergency countermeasures and short-term measures, roles and responsibilities and communication. These interlinked themes should be validated through further research that involves input from the national disaster response community at large. This study will serve as a model that can be implemented in other areas impacted by illegal mining in South Africa.

Macroseismic survey of the 6 February 2016 KwaZulu-Natal, South Africa earthquake

AbstractOn the 6th of February 2016 at 11:00 hours local time (0900 UTC), KwaZulu-Natal was struck by an earthquake of local magnitude ML=3.8. The epicentre of the earthquake was located offshore in the Durban Basin. The earthquake shaking was widely felt within the province as well as in East London in the Eastern Cape province and was reported by various national media outlets. Minor structural damage was reported. A macroseismic survey using questionnaires was conducted by the Council for Geoscience (CGS) in collaboration with the University of KwaZulu-Natal (UKZN) which yielded 41 intensity data points. Additional intensity data points were obtained from the United States Geological Survey (USGS) Did You Feel It? programme. An attempt was made to define a local intensity attenuation model. Generally, the earthquake was more strongly felt in low-cost housing neighbourhoods than in more affluent suburbs.

The AGC launches the National Geotourism Strategy

The Australian Geoscience Council (AGC) is Australia’s peak council of geoscientific societies, including the ASEG. The AGC President, Professor David Cohen, recently announced that the Council has...

Reassessment of source parameters of ‘major’ southern African earthquakes

AbstractModerate to large earthquakes within an earthquake catalogue contribute significantly to the seismic hazard and risk assessment results of any region. Thus it is prudent to ensure these events have reliable source parameters (epicentres and magnitude). The dataset of events compiled in this study contains a total of 117 instrumentally recorded events of magnitude M ≥5.0, whose parameters were obtained from the Council for Geoscience (CGS) and International Seismological Centre (ISC) databases. The events are mostly located in South Africa with a few in neighbouring countries. Parametric data made up of all available phase data and amplitudes associated with each of the earthquakes were compiled. The availability of these data enabled the earthquake epicentres and magnitude values to be recalculated using the velocity model and the local magnitude relation that are currently being used by the CGS in its analysis of national seismic data. The accuracy of the relocations was determined by producing and analysing three parameters, the azimuthal distribution of seismograph stations (GAP), root-mean-square of travel time residuals (RMS) and epicenter location error data. The analysis of these parameters showed that there was an improvement in the accuracy of the relocated events. Using the ISC location algorithm, iLOC, eight preselected events were further analysed. From this analysis, two earthquakes were found to satisfy the conditions for Ground Truth (GT595%) candidacy whilst four events satisfied the criteria for GT2090% candidacy.

Improved earthquake location in the gold mining regions of South Africa using new velocity models

AbstractReliable local earthquake locations depend on many factors of which a major one is the velocity model. Currently the Council for Geoscience (CGS) has been using the global IASP91 velocity model for earthquake locations in the cluster networks. To continue improving the earthquake locations it is necessary that new velocity models are determined for each cluster region (Central and East Rand - CERAND, the Klerksdorp – Orkney – Stilfontein – Hartebeesfontein – KOSH and the Far West and West Rand - WRAND). The availability of good quality data recorded by the cluster networks since their inception in 2010 provides an opportunity to conduct this work. Thus data from the cluster networks database were selected according to set quality criteria to obtain parametric data for 130 earthquakes in the CERAND region, 404 in the KOSH region and 1024 in the WRAND region. These data were used to determine a minimum 1-D velocity model with associated station corrections for each of the regions using the VELEST software package. Comparison of epicentres obtained using the new velocity models to epicentres previously published by the CGS, showed improvement in the quality of the new locations. Thus, the new models will be implemented in the day-to-day analysis of data recorded in the three study regions by the cluster network of stations.

Estimation of Groundwater Recharge Using GIS Method: A Case Study of Makotopong Village—Polokwane, South Africa

South Africa is a relatively dry country, with most rural areas experiencing high demand for water supply. Groundwater is one of the best alternative sources that can be used to augment the demand. However, this cannot sustainably be achieved unless accurate prediction of recharge to the groundwater aquifer is done. The objective of the study was to accurately estimate the groundwater recharge using ArcGIS method with a view of ensuring adequate groundwater for water supply exploitation. The study was conducted in Makotopong village in Polokwane. Data used in the study were sourced from diverse governmental agencies. Borehole logs were obtained from National Groundwater Archives. Geological and hydrogeological data were obtained from Council for Geoscience. All captured data were analysed to show the rainfall variations and estimation of groundwater recharge in different years. Groundwater recharge was estimated using ArcGIS 10.5. The simulated annual groundwater recharge varied from 0 mm to 51 mm with a mean recharge value of 12.04 mm/yr. The estimation of groundwater recharge using GIS methods resulted in a mean recharge value of 12.04 mm/year which shows a close comparison with previous studies conducted using Chlorine Mass Balance (CMB) and Water-Table Fluctuation (WTF). This implies that GIS is a potential tool that can be used to estimate groundwater recharge. It is recommended that GIS Method of estimating recharge be used in designing optimal sustainable groundwater supply systems.

What the marine geology of Table Bay, South Africa can inform about the western Saldania Belt, geological evolution and sedimentary dynamics of the region

Around the city of Cape Town, South Africa, the basal Neoproterozoic rocks are poorly exposed. There is however, historical evidence for good exposure of these rocks on the seafloor of Table Bay, although not mapped at sufficient resolution nor areal extent for significant conclusions. The Council for Geoscience therefore decided to commence their offshore mapping programme with this bay, mapping it at 1 m resolution using multibeam and sidescan sonar. The hope was that these data would help to unify the detailed sub-aerial investigations with offshore geological data.The seafloor outcrops are composed almost exclusively of rocks from the western branch of the Neoproterozoic Saldania Orogenic Belt and represent the largest exposure of the Tygerberg Formation regionally (~103 km2 under water compared to ~2 km2 exposed along the coastline). We demonstrate that the seafloor of Table Bay is an ideal locale to gain insight into the kinematics that have affected the rock mass on a regional scale. The outcrops display evidence of a shallow northwest-plunging anticline – syncline pair with associated smaller scale folds. The dip and strike of bedding planes delineate fold axial surface traces and fold type. The presence of lineaments and offset bedding suggest the presence of faults and/or fractures. The relative orientation of which is used to infer fault kinematics. Bedding truncation against a large northwest trending, linear, bathymetric low that is coincident with a weakly magnetic linear anomaly has led us to infer the presence of a regional Table Bay Fault zone. Lineaments interpreted as R1, R2 and P Riedel shears associated with this fault suggest sinistral strike-slip kinematics, similar to those recognised for other major fault zones on land with almost identical strike. The UNESCO world heritage site of Robben Island is located in the core of a syncline, its basal rocks composed of units marginally more arenaceous in character. The magnetic data acquired demonstrate the semi-continuous, anastomosing network of dolerite dykes within the Cretaceous False Bay Suite. Neogene features are absent in Table Bay, but as a result of Pleistocene sea level fluctuations, a complex palaeo-drainage network has incised into the seafloor during glacio-eustatically driven sea-level stillstands throughout the Quaternary Period.

Update to the South African Stratigraphic Code and Guidelines for Standardised Lithostratigraphic/Lithodemic Descriptions

Summary The South African Committee for Stratigraphy (SACS) is the official body in South Africa which regulates the nomenclature and definition of lithostratigraphic and lithodemic rock units, unconsolidated deposits and soils. The robust framework set in the existing stratigraphic code and guide for publication by the Council for Geoscience (CGS) have for many years provided leadership in this field, but there are a number of aspects in need of reconsideration. One example is the non-compliance of our nomenclature for high-grade supracrustal rocks with international (and South African) stratigraphic codes and another is manuscript format changes necessitated by publishing SACS descriptions in the SAJG. Any stratigraphic code is a living document that should be able to accommodate changing views and circumstances. This review provides a consensus opinion from experts on how to deal with changing needs.

How Legacy Data Can Open New Potential for Carbon Capture and Storage in South Africa

The process of Carbon Capture and Storage (CCS) has been practiced since the mid 1970’s within the hydrocarbon industry. Since the early 2000’s, South Africa, Africa’s largest producer of CO2, has carried out various studies to ascertain whether it has the potential for safe CCS. A series of storage site assessments and investigations with governmental collaborations have been undertaken. A Pilot Carbon Storage Project (PCSP) is currently underway, led by the South African National Energy Development Institute with support from the World Bank CCS Trust Fund, and in collaboration with its research partners, the Council for Geoscience, Petroleum Agency SA and Battelle. The aim of the PCSP is to transport, monitor and safely store between 10 000 to 50 000t of CO2.

The 03 April 2017 Botswana M6.5 earthquake: Preliminary results

An earthquake of magnitude Mw 6.5 occurred on the evening of 3 April 2017 in Central Botswana, southern Africa. The event was well recorded by the regional seismic networks. The location by the Council for Geoscience (CGS) placed it near the Central Kgalagadi Game Reserve. Its effects were felt widely in southern Africa and were pronounced for residents of Gauteng and the North West Province in South Africa. In response to this event, the CGS, together with the Botswana Geoscience Institute (BGI), embarked on two scientific projects. The first project involved a macroseismic survey to study the extent and nature of the effects of the event in southern Africa. This involved CGS and BGI scientists soliciting information from members of the public through questionnaire surveys. More information was collected through questionnaires submitted online by the public. In total, 181 questionnaires were obtained through interviews and 151 online from South Africa, Zimbabwe and Namibia through collaboration between the CGS, the Meteorological Services Department of Zimbabwe and the Geological Survey of Namibia. All collected data were analysed to produce 79 intensity data points (IDPs) located all over the region, with maximum intensity values of VI (according to the Modified Mercalli Intensity scale) observed near the epicentre. This is quite a low value of maximum intensity for such a large event, but was expected given that the epicentral region is in a national park which is sparsely populated. The second scientific project involved the rapid installation of a temporary network of six seismograph stations in and around the location of the main event with the purpose of detecting and recording its aftershocks over a period of three months. Data recorded in the first month of April 2017 were collected and delivered to both the CGS and BGI for processing. More than 500 aftershock events of magnitude ML ≥ 0.8 were recorded and analysed for this period. All the events were located at the eastern edge of the Central Kgalagadi Park near the location of the main event in two clear clusters. The observed clusters imply that a segmented fault is the source of these earthquakes and is oriented in a NW-SE direction, similar to the direction inferred from the fault plane solution of the main event.

Rupture process of the 2014 Orkney earthquake, South Africa

An earthquake has occurred at 10:22:33 UT on 5 August 2014 in the Klerksdorp district, the North West province of South Africa. Its hypocenter is located beneath an Orkney town, where more than 10 gold mines exist. The Council for Geoscience (CGS) in South Africa reported that the magnitude and depth was ML5.5 and 4.7 km, respectively. CGS has been operating 17 surface seismic acceleration stations with 10 km interval in average, and obtained continuous acceleration seismograms through the time of the earthquake and following aftershocks. Using these seismograms, we analyzed the mainshock rupture process of this earthquake. Analyzing these seismograms, we found the ‘initial rupture’ with a Richter scale approximately 4 has occurred 0.3 sec before mainshock. Furthermore, by applying detailed aftershock distribution analysis, we found most of aftershocks occurred surrounding upper and southern part of mainshock rupture area, including initial rupture hypocenter. In order to understand detailed rupture process of this event, we surveyed for strong motion generating area (SMGA) of mainshock by applying Isochrones backprojection method (IBM) to the mainshock S wave waveforms. SMGA distribution seems to fill the vacant space of the aftershock distribution and initial rupture’s hypocenter. And we also found that a horizontal layered seismic vacancy exists between aftershocks with gold mine blastings. This fact implies mainshock rupture did not extent up to gold mine.

Uranium in South Africa: Exploration and Supply Capacity

The major uranium deposits types are quartz-pebble conglomerate of the Central Rand Group (Witwatersrand Supergroup) and the Dominion Group, sandstone of the Karoo Uranium Province, surficial deposits of the Namaqualand region, as well as coal of the Springbok Flats Basin. Recent exploration activities (both greenfields and near-mine) have increased the resource potentials of these deposits. South Africa's Council for Geoscience has conducted high resolution magnetic and radiometric surveys in the Namaqualand region. Witwatersrand Basin is the only deposit where uranium mining is active at present in South Africa. Total uranium production in 2015 was 448 t. However, with production expected to increase in the Witwatersrand Basin, production is expected to reach 700 t U by the end of 2018. Furthermore, with uranium production envisaged to begin in the Karoo Uranium Province, uranium production may exceed 1000 t U by the year 2020.

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

The South African National Seismograph Network operated by the Geophysics Competency of the Council for Geoscience.

Iphakade is Earth Stewardship Science

### Inkaba yeAfrica and !Khure Africa – the past Two collaborative bilateral Earth System Science Programmes - Inkaba yeAfrica and !Khure Africa - have been active for 12 and 6 years with Germany and France, respectively, and have been generously supported by DST and NRF throughout this time (see www.inkaba.org ). More recently the two programmes merged into one as the bilateral spirits of these programmes started to fade. It is therefore timely to move on and establish a South African Programme that can stand on its own, and attract international collaborations on the basis of its indigenous research excellence in one of Earth’s most attractive natural and enigmatic social laboratories. From a small beginning in 2004 with 10 students, the programmes 10 years later catered for 181 students in some 31 projects; and by 2015, 224 students had graduated. The largest student participation continues to be at MSc level (with a ratio of Honours:MSc:PhD at 1:6:5). In terms of gender, the total number of female students in 2014 was 43%; and 64% of the students were black. On average, the cost of running this program over a decade has been about R24k per student, including 1 or 2 student conferences/workshops per annum. The success of the project to-date has largely been due to dedicated mentoring by senior researchers and university support (in 2014, 12 South African universities and the Council for Geoscience participated); and to the near 24/7 ukuphatha (liaison) and management for the student interests by Ms Elronah Schaap over the last decade. Building on the two bilateral programmes we have now combined the research goals and capacity building aims of the two Earth Systems Science programmes into one unified endeavour that we have called –’Iphakade’ – an isiKhosa word that best encapsulates ‘Earth Stewardship Science’. It is perhaps a reflection of the dedications and hard work …

Impact of Recent Moderately Sized Earthquakes in South Africa: Macroseismic Investigations of the 18 November and 2 December 2013 Earthquakes

Recent moderately sized earthquakes (18 November 2013 and 2 December 2013) occurred in the Johannesburg area (M L = 3.6) and southern Limpopo Province (M L = 3.9) respectively. The earthquakes vigorously shook the epicentral areas. Following the shaking, many people submitted reports to the Council for Geoscience (CGS) through an online questionnaire which recorded their experience, whilst others reported the earthquake and its effects on social networks like Twitter. Following both earthquakes, the CGS sent teams of experts into the surrounding areas to assess the effects of the earthquake by interviewing members of the public and completing additional questionnaires. Analyses of the collected macroseismic data produced intensity data points which showed that a maximum intensity of VI was experienced at Fleurhof for the 18 November 2013 earthquake. Maximum shaking with intensity of IV to V was also experienced at KwaMhlanga, Modimolle, and Bela-Bela during the 2 December 2013 earthquake. Surprisingly, strong shaking of intensity IV was also experienced in northern Johannesburg, about 150 km from the epicentre. Investigations showed that this apparent amplification of the ground motion in Johannesburg can be linked to topographic effects. By analyzing first motion polarities, fault plane solutions were obtained for both earthquakes, oblique normal faulting with strike of 72° dip 51° and rake of −77° for the 18 November earthquake; normal oblique left lateral faulting with strike of 135°, dip of 45° and rake of −82° for the 2 December 2013 earthquake.

INTRODUCTION TO REPORTS OF THE SOUTH AFRICAN COMMITTEE ON STRATIGRAPHY (SACS):

In 1971 the South African Committee for Stratigraphy (SACS) drew up a code of stratigraphic terminology and nomenclature, and used this as the basis to subsequently present a comprehensive outline of South African stratigraphy (SACS, 1971, 1980). Units which were not included in the 1980 Handbook were formally described in the periodicals known as the “Lithostratigraphic Series” (detailed descriptions) and the “Catalogue” (abridged descriptions), published by the Council for Geoscience and its predecessor, the Geological Survey of South Africa. These valuable documents were never as widely circulated as their content warranted, thus the Geological Society of South Africa was approached to incorporate the stratigraphic descriptions produced under the auspices of SACS into the South African Journal of Geology. At their 44th meeting at the University of Pretoria, on 27th October 2014, the National Committee …

The Australian Geoscience Council in 2015

The Australian Geoscience Council in 2015

Macroseismic survey of the ML5.5, 2014 Orkney earthquake

On 5 August 2014 at 1222 hours (local time), an earthquake of local magnitude ML = 5.5 occurred in the Orkney area in the North West Province, South Africa. The earthquake shaking was felt widely in South Africa as far as Cape Town as well as in Maputo, Mozambique, and Gaborone in Botswana. One person was killed when a wall collapsed on him, and more than 600 houses were damaged. Following the earthquake, many people submitted reports to the Council for Geoscience (CGS) through an online questionnaire which recorded their experience, whilst others reported the event and its effects on social networks like Twitter and in newspapers. The CGS also sent out a team of scientists to further assess the effects of the event in the community by interviewing members of the public and completing additional questionnaires. A total of 866 observations were collected. Analysis of the collected macroseismic data produced 170 intensity data points which showed that a maximum intensity of VII was experienced in communities located in the epicentral area. The observed attenuation of intensity values was comparable to that observed on the French stable continental region especially in the area of 600-km radius from the epicentre. Airborne geophysical data were used to try and identify the fault along which the earthquake occurred. This was necessary as there was no surface expression of the earthquake and no previously identified fault near the epicentre. The interpretation of the data showed a fault located about 500 m from the epicentre appearing to form a boundary to the east of located aftershocks.