18 Figure 2.2 Map of Southern Africa with seismic events (stars) and IDPs reported in the text. dotted circles) with corresponding epicenters of earthquakes reported within a few days by reported IDPs. 45 Figure 3.2 Seismicity of the KZN region with the results of focal mechanism studies (data from . Geoscience Council). 49 Figure 3.5 Regional gravimetric map of South Africa overlaid on major geological. data from the Geoscience Council).
53 Figure 3.9 Map of structural lineaments contained in Geology 1-250K (Geoscience Council data) and neotectonic structures digitized from reports cited here. 57 Figure 3.13 Seismotectonic interpretations taking into account multidisciplinary data and research (historical earthquakes – red, instrumental earthquakes – green).
INTRODUCTION
- Problem Definition
- Motivation
- Aims and Objectives
- Research Approach
- Technical and Scientific Contributions
- Structure of the Thesis
- References
Each of the objectives outlined above was achieved using different research methods and will be described separately. The custodian of the earthquake catalog for South Africa is the Council for Geoscience (CGS). Note that during data collection there was no restriction on the scale of data to be collected.
Nevertheless, these databases will ensure the longevity of the research and facilitate easy updating and validation. Seismogenic domains - areas of diffuse seismicity that cannot be associated with specific geological structures. The seismotectonic model is the sum of the seismotectonic zones.
ANALYSIS OF POSSIBLE SOURCES OF SOME UNREGISTERED HISTORICAL
- Introduction
- Literature Review
- Methodology
- Results and Discussion
- Conclusions
- Acknowledgements
- References
The first step in the methodology was to collect existing historical datasets for the country. A list was then made of the events that were not recorded in the national datasets. Most of the events in the above publications were already registered in the database.
Note that one of the reasons why these events were not included in the national database was that Von Veh's (1988) work was not published. For the 1 September 1970 event, three earthquakes were reported in the Mozambique Channel which is the most likely location of the epicenter of this IDP.
SEISMOTECTONIC ANALYSIS OF KWA-ZULU NATAL, SOUTH AFRICA
Introduction
The coastal province of KwaZulu-Natal (KZN) is a seismically active region of South Africa (SA) that is the site of major infrastructure developments. The increase in population density and therefore vulnerability requires a thorough analysis of seismic sources and potentially active fractures and geological structures. A seismotectonic source area model for the province is proposed, which is built from a multidisciplinary geo-database that can help in active fault determination and to understand the causes of earthquake generation.
The enhanced earthquake database used in this study includes fault ellipses for location and focal mechanism solutions where possible. The KZN coastal areas have experienced several potentially damaging historical earthquakes at a time with less population density and fewer buildings, so there is little memory or record of earthquake damage. The reported damage was significantly less than if such incidents were to occur today, due to the higher level of today's infrastructure and population.
The collected data sets reveal that the coastal areas have numerous NE-SW faults that formed during the breakup of Gondwana. Thermal springs are also located here, indicating a possible area of neotectonic activity. While seismic hazard maps were calculated for South Africa [Fernandez and du Plessis, in most cases the methodology used for the seismic hazard maps was based on non-zonal methods, mainly because the seismotectonic model for the region was poorly documented.
Internationally, regulations for the seismic design of public infrastructure such as nuclear power stations, bridges and tunnels require seismotectonic models to be included in some form in the seismic hazard assessments (SHA), hence their importance. In this work we analyze all available geological, geomorphological, tectonic, seismic and geophysical data (from published literature and professional reports from research institutions and surveys) and explain our seismotectonic approach.
Literature Review – State of the art
Methodology
Data Assembly and Interpretation
- Seismic System
- Structural Systems
- Kinematic System of the African Plate
- Discussion - Assimilation
The lithological units that crop out in the province are shown in the figure, giving a general overview of the rock units that crop out in the province. The basement rock units outcrop in the northern part of the province towards the Swaziland border. Most of the central part of the province consists of Paleozoic to Mesozoic (300-180Ma) Karoo Supergroup (KS) sediments.
The broad structure of the province consists of undisturbed Karoo rocks in the interior of the province, which dip gently westward into the Karoo basin. There has been controversy surrounding the model used to explain the structural patterns and topography of the region. Leinweber and Jokat (2011) undertook a detailed geophysical study of the geology of the Northern Natal Valley and Mozambique Ridge.
They describe in great detail the complex truncated structures in the lignite beds of the Port Durnford Formation (Holocene age) (NECSA, 1989). One controversial aspect of Bird et al. 2006) is a projection of the southernmost extent of the EARS. The fault pattern becomes more complex in the extreme northern part of the region, where different trending faults intersect.
Alternatively, a re-evaluation of the finite element neotectonic models of Bird et al. Subdomain 3a is the faulted region south of the KC and Subdomain 3c is to the north. Subareas 3c and 3d span the relatively unfaulted western region south and north of the KC.
Conclusions
Correlation with geological features and historical and instrumental earthquakes - Identification of possible seismogenic structures even in areas where there is no seismicity - Delineation of earthquake source areas. Checking the self-consistency of time-zero kinematic results with present-day stress field reconstructions from independent datasets (geodetic data, seismological data) Present and historical seismicity system. Assimilation of historical seismic data from various sources -Instrumental seismic data - relocation of events, removal of induced events.
180-300Ma Karoo Supergroup Lebombo Group rhyolite and basalt Drakensburg Group basalt and dolerite Stormberg Group mudstone and sandstone Group mudstone and sandstone. Late Jurassic, Early Cretaceous - to late Early Miocene - African 1st erosion cycle Extensive volcanic activity - seaward tilting and down-faulting along the Natal coast - NNMB and KS rocks lowered to sea level along the coast. The Falkland Islands separated from Africa along a short rifted margin and moved 1300 km along the Agulhus transform fault movement along the extensional transform along the Tanzanian continental margin and the northern end of Lebomba and the southeastern side of Falkland Island.
Late Pliocene to Holocene – Climatic and Sea Level Fluctuation Late Pliocene to Holocene – Post-African Erosion Cycle II. Post African Surface Formation II, gorge incision, incision and terrace formation along rivers Asymmetric uplift of the subcontinent, large westward tilting of the interior land surface, monoclinal deformation along southern and eastern coastal margins Post African Surface Formation 1.
The Global Seismic Hazard Assessment Program, (GSHAP), Annali di Geofisica Hazard mapping in risk evaluation for engineering structures. Seismotectonics of the Lwandle-Nubia Plate Boundary between South Africa and the Southwest Indian Ridge, European Geosciences Union General Assembly 2013, Vienna, Austria. Pn traveltime tomography of the paleo-continental collision and rift zone around Korea and Japan, Bulletin of the Seismological Society of America.
Lower crustal shear wave velocity structure in southern Africa: Evidence for compositional heterogeneity within Archean and Proterozoic terranes, J. Seismotectonic zoning in east-central Italy inferred from a Neogene analysis to represent deformation and related fields. the stress. Report on the Geology of the North Coast Natal Region from the mouth of the Umvoti River to Port Edmund.
Seismotectonic modeling of the KZN province, SA using the SOM algorithm, BSc Hons thesis, University of KwaZulu Natal, unpublished. Crustal structure beneath southern Africa and its implications for the formation and evolution of the Cape Vaal and Zimbabwe cratons. A Physiographic Subdivision for Earth and Environmental Scientists, Transactions of the Royal Society of South Africa, Vol.
African Geodynamics from the Precambrian to the Present, SAGA, 13th Biennial Conference, Skukuza, South Africa, 5-6 October. Structure of the Transkei Basin and Natal Valley, southwestern Indian Ocean, from seismic reflection and potential field data, Tectonophysics. Durban CBD, SA Seismic Vulnerability Database Development and Seismic Risk Assessment. Incorporating descriptive metadata into models of earthquake source areas for seismic hazard assessment: a case study of the Azores–Western Iberia region.
Acknowledgements
Anomalous seafloor mounds in the northern Natal Basin, southwest Indian Ocean: Implications for the East African rift system.
DISCUSSION AND CONCLUSION
Earthquake Displacement in KZN Province for Seismotectonic Analysis, Seismotectonics Project Meeting, University of Kwa-Zulu Natal, November 2013. Structural Geological Analysis of Fault Lines and Traces and Dikes in KwaZulu-Natal Province, School of Geological Sciences, University of KwaZulu - Natal.
APPENDICES – PEER-REVIEWED AND NON PEER-REVEIWED CONTENTS
EGU 2012 Abstract: Seismotectonic Analysis for the KZN region of South Africa
2013), Combining Structural Domains, Geomorphological Provinces and GPS Data for Seismotectonic Modeling of the KZN Province, SAGA-AEM Conference, July 2013, Kruger National Park, SA. A study of the seismic catalog (Singh et al 2013) reveals that the region in question has a high level of seismic activity. A study of the seismic catalog reveals that the region in question has a high level of seismic activity, so ground motion parameters should be included in the design of critical structures.
These assessments are critical for the construction of modern critical facilities such as hazardous and high-rise buildings. In this study, the following datasets are presented: the seismic history of the region, the regional geology and the regional geophysics. The phenomenon of site effects was clearly shown in the observations of the after effects of this event.
Changing rock types in the area also had a strong influence on the attenuation of the seismic wave. The older rock units outcrop towards the northern extent of the province towards the Swaziland border. This boundary also falls in the same vicinity of the EW trending fault mapped through the province.
Visual correlations of seismic catalog locations show parallel NE-SW coast patterns of seismic occurrences. This pattern correlates with the geology of the NMP and the NGS outcrop in a similar coast-parallel orientation. From the regional geophysical datasets the boundaries of the KC Akean and NNMB basement geologic provinces can be established.
![Fig. 1: Isoseismal maps of significant earthquakes that have occurred within the province (from [2])](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10639283.0/89.892.106.394.746.1073/fig-1-isoseismal-maps-significant-earthquakes-occurred-province.webp)
