Abstract

Earth tremors originating at a single Witwatersrand mine were recorded by six vertical seismometer stations all within about 10,000 ft. (3.0 km.) of the foci. A triggered system of recording permitted the first arrivals to be timed to 5 milliseconds, giving a location accuracy of about 250 ft. (75 m.). All the 100 foci determined were in close proximity to the position of active mining, or slightly above it, and had a mean depth of 7,500 ft. (2.3 km.). Eighty per cent of the first movements observed were downward, i.e., cataseismic. The implications of these results are discussed.

First Page Preview

First page PDF preview
You do not currently have access to this article.