Temporal changes in attenuation ofSwaves through a fault zone in a South African gold mine

Abstract

SUMMARY We investigated the temporal changes in the seismic attenuation of a fault zone using near‐source recordings of S waves from repeating microearthquakes that occurred both before and after M ∼ 2 earthquakes in the Bambanani gold mine, South Africa. Because the source locations and the mechanisms of repeating earthquakes can be regarded as identical, the attenuation change can be estimated using the spectral ratios for repeating earthquake pairs. We found an increase in the S‐wave attenuation parameter on the vertical component which is positively correlated with frequency, corresponding to times before and after the M ∼ 2 earthquakes. This increase can be explained by scattering attenuation, with a typical scale of damage in the fault zone of ∼3 m.

Evaluation of Anti-Burst Performance in Mining Roadway Support System

“…Therefore, it is difficult to identify the PPV value representing the propagation of dynamic load from the source to the roadway surface [ 30 ]. Fortunately, with the rapid advancement of computer technology and numerical techniques, numerical modeling is becoming an irreplaceable and indispensable method for investigating seismic wave propagation [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Therefore, this paper adopts the numerical simulation method to determine the critical PPV value of roadway failure by applying dynamic loads of different amplitudes.…”

Unexpectedly frequent occurrence of very small repeating earthquakes (−5.1 ≤ Mw ≤ −3.6) in a South African gold mine: Implications for monitoring intraplate faults

“…The magnitude of the repeaters was in the range −5.1 ≤ M w ≤ −3.6. To date, they are the smallest repeating earthquakes identified as such on a geological fault, including repeaters found in mines [ Yamamoto , ; Yoshimitsu et al , ; Naoi et al , ]. Figure a shows waveforms of the 10 AE sensors that were used in the repeater identification for all the 16 events belonging to the largest repeater group, showing the very high similarity of waveforms among events belonging to the same group, though the similarity become lower for more distant stations owing to low S/N ratios.…”