30 April 2008
Windhoek — An earthquake struck twice in the vicinity of Omaruru in the Erongo region on Saturday. The tremors were less than two hours apart.
The first earthquake measuring 5.6 on the Richter scale occurred at about 15h50 about 50 kilo-metres east of Omaruru, according to the Directorate of Geological Survey.
Senior Geophysicist, Manfred Muundjua, told Nampa yesterday that the earthquake was 10 kilo-metres below the surface. The national seismological network with recording stations at Aus, Ariamsvlei, Windhoek, Kamanjab, Tsumeb and Rundu recorded the earthquake.
"The coordinate of the epicentre (position of earthquake in terms of latitude and longitude) is 21.383S and 16.449E. For local earthquakes, depth is assumed to be 10 kilometres below the surface. We have established that the epicentre is located on a major geological feature called the Aretarages lineament. This particular lineament starts from west of Windhoek and it terminates at the Waterberg thrust (it is a major regional fault, associated with the East African rifting, a claim held by some workers within the geological community)," he explained.
Muundjua said a magnitude of 5.6 is quite substantial and should arouse interest within the scientific community, particularly if future events within the area produce earthquakes of similar magnitude. A second earthquake (aftershock) was also felt at Omaruru around 17h12. "This one was substantially weaker than the first," he added. No injuries or damages were reported. Namibia's seismicity is regarded as moderate because since 1910 until now, tremors have been felt but the country has not recorded a major earthquake. Areas with geological faults that are active (areas that have recorded a seismic event) are Opuwo, Windhoek, Waterberg, Khorixas and Bethanie.
An earthquake is the result of a sudden release of energy in the earth's crust that creates seismic waves. At the earth's surface, earthquakes manifest themselves by a shaking and sometimes displacement of the ground. When a large earthquake epicentre is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami.
The shaking in earthquakes can also trigger landslides, and occasionally volcanic activity.
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