%A Grzegorz Kwiatek
%A Yehuda Ben-Zion
%J Journal of Geophysical Research: Solid Earth
%T Assessment of Pand Swave energy radiated from very small shear-tensile seismic events in a deep South African mine
%X We discuss requirements for reliable estimates of radiated seismic energy in S and P phases and derive ratios of S-to-P radiated energy (ES/EP) of 539 seismic events with local magnitudes − 5.23 ≤ ML ≤ − 2.41 (subdecimeter size) recorded by high-frequency acoustic emission (AE) sensors of the JAGUARS seismic network in the Mponeng deep gold mine, South Africa. The analyzed events are aftershocks of a MW1.9 earthquake, and the recording AE sensors are located within about 40 m of the events. A shear-tensile model is used to simulate the radiation pattern of P and S phases from a family of rupture models ranging from pure shear to pure tensile failure. The calculations include correction factors for energy estimates associated with given source-receiver geometries and expected focal mechanism with possible tensile component. Synthetic calculations are used to assess the effects of limited observed frequency band and attenuation on the estimated ES/EP ratios. The model calculations provide guidelines on when different approximations may be used. The obtained ES/EP ratios for the analyzed events are relatively low (median value < 5) for the full range of model parameters tested, suggesting that significant number of the events display a tensile component. Events with very small ratios (e.g., <1) may reflect enhanced P radiation associated with rock damage in the source volumes.
%N 7
%K radiated energy, tensile faulting, non-DC components
%P 3630-3641
%V 118
%D 2013
%I John Wiley & Sons, Ltd.
%R doi:10.1002/jgrb.50274
%L epos1251