TY - JOUR
T1 - Emergence and disappearance of very small repeating earthquakes on a geological fault in a gold mine in South Africa
AU - Yamaguchi, Junya
AU - Naoi, Makoto
AU - Nakatani, Masao
AU - Moriya, Hirokazu
AU - Igarashi, Toshihiro
AU - Murakami, Osamu
AU - Yabe, Yasuo
AU - Durrheim, Raymond
AU - Ogasawara, Hiroshi
N1 - Funding Information:
We thank Sibanye Gold Ltd., operator of the Cooke 4 mine, for approving our publication, and personnel at the mine and at the Institute of Mine Seismology for facilitating our project. We also thank Sylvester Morema, Sifiso Khambule, Joachim Philipp, Koji Miyakawa, Atsushi Watanabe, and late Gilbert Morema for their contribution to the observation. This project was funded by JSPS KAKENHI grants 21224012 , 21246134 , 26249137 , and 26887022 . It was also funded by JST/JICA, SATREPS , the MEXT 's Earthquake and Volcano Hazards Observation and Research Program, the Earthquake Research Institute The University of Tokyo cooperative research program, the Arai Science and Technology Foundation , and the Maeda Engineering Foundation . R.J.D. acknowledges support from the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation.
Funding Information:
We thank Sibanye Gold Ltd., operator of the Cooke 4 mine, for approving our publication, and personnel at the mine and at the Institute of Mine Seismology for facilitating our project. We also thank Sylvester Morema, Sifiso Khambule, Joachim Philipp, Koji Miyakawa, Atsushi Watanabe, and late Gilbert Morema for their contribution to the observation. This project was funded by JSPS KAKENHI grants 21224012, 21246134, 26249137, and 26887022. It was also funded by JST/JICA, SATREPS, the MEXT's Earthquake and Volcano Hazards Observation and Research Program, the Earthquake Research Institute The University of Tokyo cooperative research program, the Arai Science and Technology Foundation, and the Maeda Engineering Foundation. R.J.D. acknowledges support from the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/11/13
Y1 - 2018/11/13
N2 - We investigated the activities of very small (−5.10 ≤ MW ≤ −2.35) repeating earthquakes that occurred during 14 months on a geological fault at a 1 km depth in the Cooke 4 gold mine in South Africa. Out of 4214 acoustic emissions occurring on the fault, 1785 (42.36% of the total) were identified as repeaters on the basis of the waveform similarity and the proximity of hypocenters. Quite a few large groups, having up to 57 members, were recognized. Activities of some groups certainly continued throughout the 14 months, but we also found some repeater groups that newly emerged or disappeared during this period. Both types often coexisted within a distance as small as ~0.5 m, within which background fault creep should be coherent. Some disappearing groups showed a decrease in the event magnitude with time. These temporal changes of repeater activities may imply the formation and dissipation of topographical asperity contacts on the fault. Our results suggest that ultrasensitive observation of acoustic emissions can reveal the physical evolution of asperities.
AB - We investigated the activities of very small (−5.10 ≤ MW ≤ −2.35) repeating earthquakes that occurred during 14 months on a geological fault at a 1 km depth in the Cooke 4 gold mine in South Africa. Out of 4214 acoustic emissions occurring on the fault, 1785 (42.36% of the total) were identified as repeaters on the basis of the waveform similarity and the proximity of hypocenters. Quite a few large groups, having up to 57 members, were recognized. Activities of some groups certainly continued throughout the 14 months, but we also found some repeater groups that newly emerged or disappeared during this period. Both types often coexisted within a distance as small as ~0.5 m, within which background fault creep should be coherent. Some disappearing groups showed a decrease in the event magnitude with time. These temporal changes of repeater activities may imply the formation and dissipation of topographical asperity contacts on the fault. Our results suggest that ultrasensitive observation of acoustic emissions can reveal the physical evolution of asperities.
KW - Acoustic emissions
KW - Geological faults
KW - Gold mine in South Africa
KW - Mining-induced earthquakes
KW - Repeating earthquakes
KW - Topographical asperities
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U2 - 10.1016/j.tecto.2018.10.014
DO - 10.1016/j.tecto.2018.10.014
M3 - Article
AN - SCOPUS:85054839040
SN - 0040-1951
VL - 747-748
SP - 318
EP - 326
JO - Tectonophysics
JF - Tectonophysics
ER -