A study of seismicity in the Damara Province

Abstract

Abstract provided by author:

Magnitudes were calculated from either peak trace amplitudes or coda durations, the latter method being necessary for saturated recordings. The magnitudes ranged from -1. to 3. and the values agreed well with the magnitudes obtained from the Windhoek records

First motion data was inadequate to yield focal mechanism solutions for individual events; however, composite focal mechanisms were established for two groups of events close to the profile. These solutions indicated normal faulting with a northeast striking tension axis

Previous work on the seismicity of SWA/Namibia indicates that tremors occur along the length of the escarpment and throughout the area where the folded Damara System is exposed. The seismic activity has been variously attributed to upwarping of the highland areas, or connected with rifting in the central parts of Southern Africa

The evidence from the tremors studied here, favours the former hypothesis of a broad upwarping of the region, parallel to the escarpment giving rise to an easterly to northeasterly tension axis