Mine aftershocks and implications for seismic hazard assessment
Date
2011-03-31
Authors
Kgarume, Thabang Ephraim
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Abstract
A methodology of assessing the seismic hazard associated with aftershocks
is developed by performing statistical and deterministic analysis of seismic
data from two South African deep-level gold mines. A method employing
stacking of aftershocks is employed due to the small number of aftershocks
succeeding each mainshock. Mine tremor aftershocks were found to obey
statistical relations governing aftershocks (Gutenberg-Richter frequencymagnitude,
Modified Omori law and the density law, with the exception of
Båth’s law) as natural earthquake aftershocks do. This analysis was used to
approximate the time periods when the seismic hazard due to aftershocks has
decreased to background levels. These time periods can be used to draw
guidelines governing the re-entry periods to working areas following a larger
seismic event. Deterministic analysis revealed that aftershock productivity is
not strongly influenced by mining conditions (i.e. local stresses, strain rates,
and the proximity to geological features such as faults and dykes).