REPORT ON THE 26/08/2014 EARTH TREMOR RECORDED IN WINDHOEK. INTRODUCTION The Geological Survey of Namibia confirms that on the 26th of August 2014 at 02:52:05 GMT, Tuesday (03:52 local time), an earth tremor of unknown magnitude was recorded at the Windhoek seismic station. The tremor was only recorded by this station. Analysis from the available waveform data indicate a tremor that lasted approximately 15 - 20 seconds. No significant aftershocks can be identified in the recorded data immediately after the event. From the above waveform, the compressional (P-wave), shear (S-wave) and surface waves arriving at the stations are clearly visible. DATA Phase readings were analysed by the Geophysics Division at the Geological Survey for KJAB (Kamanjab), WIN (Windhoek), AUSN (Aus) , RUDU (Rundu), GOB (Gobabis) and stations in South Africa, KOMG (Komagas), UPI (Upington) and AUGR (Augrabies) for location and magnitude calculations. The main event has been recorded at the WIN station and the . magnitude could not be determined as only the Windhoek station recorded the event. A minimum of three seismic stations is needed to make a determination of the location and depth of the epicentre and the associated magnitude. As can be seen from the recorded phase readings above the WIN station, the recorded seismic activity across the country does not correlate well with the measurement at the Windhoek station. This makes it tricky and difficult to characterize the event. We therefore conclude at this stage that the event was extremely local. m order to find an explanation for the tremor, the public is urged to contact the Geophysics Division at 061 -284-8142/8144 at the Geological Survey as soon as possible and provide detailed accounts of their experiences in addition to the location where they were at the time of the event. This will allow the Geophysics Division to study this event further and provide a reasonable explanation on the cause of the tremor in due course. Namibia is not earthquake prone and the seismic activity in the country is considered low. It is normal that people will experience slight tremors at times and this indicates that energy is released through the earths crust. The magnitudes of these tremors are low and will need to be two or three orders of magnitude higher to potentially cause damage to property. Such strong quakes are extremely rare in Namibia. The country is located in the middle of the African plate relatively far away from the seismically active plate boundaries .
Posted on: Fri, 29 Aug 2014 11:00:00 +0000
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