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Seismicity and neotectonic uplift in the Augrabies Falls National Park,Namaqualand,Northern Cape,South Africa 
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下载免费PDF全文 Kakaba Madi 《地震科学（英文版）》2016,29(5):281-289
Gneissic rocks in the Augrabies Falls National Park are part of the Proterozoic Namaqua-Natal mobile belt. Finding neotectonic evidence in old terranes is always not an easy task. In South Africa, the mid-Miocene is believed to be the beginning of neotectonics. This study investigated the occurrence and recurrence of earthquake activity, occurrence of faulting, jointing, uplift, and potholes in the gneisses cropping out around the Augrabies Falls area that may account for neotectonics. A historic seismic event obtained from the United States Geological Survey(USGS), and seismic epicenters downloaded in October 2015 from IRIS earthquake browser and overlaid on a satellite image with digitised faults and lineaments,indicates that the area is seismically active and is a zone of seismic risk. Potholes occurring today on a dry surface at approximately 613 m above sea level are a direct consequence of the Griqualand-Transvaal neotectonic uplift,which generated a major fault along which water flows continuously. It is concluded that the Augrabies Falls National Park area is a zone of neotectonics. This zone should not be considered for the storage of nuclear wastes. 相似文献
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H profiles of a rosette region consisting of several bright and dark mottles were obtained with the Multichannel Subtractive Double Pass (MSDP) spectrograph mounted on the 50 cm 'Tourelle' refractor of the Pic du Midi Observatory. These profiles have been analysed in terms of the classical cloud model which assumes a constant source function and holds only for optically thin structures. A new technique is also described which enables the determination of various physical parameters of chromospheric features taking into account the variation of the source function with the optical depth. This method can be applied, in contrast to the classical cloud model, to all lines whether optically thin or optically thick and gives a good fit to the entire profile from the core to the wings. A comparison of the results given by the two different methods is also performed. 相似文献
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Modified DRASTIC assessment for intrinsic vulnerability mapping of karst aquifers: a case study 总被引：4，自引：1，他引：3
Groundwater in karstic aquifers can be dangerously sensitive to contamination. In this paper, DRASTIC assessment was modified
and applied, for the first time, to address the intrinsic vulnerability for karst aquifers. The theoretical weights of two
of DRASTIC’s parameters (aquifer media and hydraulic conductivity) were modified through sensitivity analysis. Two tests of
sensitivity analyses were carried out: the map removal and the single parameter sensitivity analyses. The modified assessment
was applied for the karst aquifers underlying Ramallah District (Palestine) as a case study. The aquifer vulnerability map
indicated that the case study area is under low, moderate and high vulnerability of groundwater to contamination. The vulnerability
index can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality.
The modified DRASTIC assessment has proven to be effective because it is relatively straightforward, use data that are commonly
available or estimated and produces an end product that is easily interpreted. 相似文献
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Kakaba Madi Peter K. Nyabeze Oswald Gwavava Matome Sekiba Baojin Zhao 《Acta Geophysica》2016,64(4):943-962
Finding productive boreholes in the Karoo fractured aquifers has never been an easy task. Fractured Karoo aquifers in the neotectonic zones in the Eastern Cape Province can be targeted for groundwater exploration. The Polile Tshisa hot spring is located in a seismo-tectonic region beset by neotectonics. Hot springs are indicative of circulation of groundwater at great depths along fault zones, and accordingly of neotectonics. The characterisation of hot springs by means of magnetic and electromagnetic methods can help infer the occurrence of structures which are favourable for groundwater potential. The Polile Tshisa hot spring is characterised by faults, fractures, and dolerite dykes. All these structures make the hot spring a good case study for groundwater exploration. 相似文献
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