%0 Journal Article
%@ 1343-8832
%A Yabe, Yasuo
%A Philipp, Joachim
%A Nakatani, Masao
%A Morema, Gilbert
%A Naoi, Makoto
%A Kawakata, Hironori
%A Igarashi, Toshihiro
%A Dresen, Georg
%A Ogasawara, Hiroshi
%A Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan,
%A GMuG Gesellschaft für Materialprüfung und Geophysik, Dieselstraße 9, 61231, Bad Nauheim, Germany,
%A Earthquake Research Institute, the University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan,
%A SeismoGen cc, PO Box 1177, Carletonville, 2500, South Africa,
%A Earthquake Research Institute, the University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan,
%A Faculty of Science and Engineering, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, 525-8577, Japan,
%A Earthquake Research Institute, the University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan,
%A Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany,
%A Faculty of Science and Engineering, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, 525-8577, Japan,
%D 2009
%F epos:1308
%I Terra Scientific Publishing Company
%J Earth, Planets and Space
%K Semi-controlled earthquake generation experiment,         acoustic emission, mining-induced earthquake, deep South African gold mines         aftershocks         main shock rupture plane
%N 10
%P e49-e52
%T Observation of numerous aftershocks of an M w 1.9 earthquake with an AE network installed in a deep gold mine in South Africa
%U https://episodesplatform.eu/eprints/1308/
%V 61
%X This is the first report from the JAGUARS (JApanese-German Underground Acoustic Emission Research in South Africa) project, the overall aim of which is to observe ultra-small fracturing in a more or less natural environment. We installed a local (∼40-m span) network of eight acoustic emission (AE) sensors, which have the capability to observe up to 200 kHz at a depth of 3.3 km in a South African gold mine. Our specific objective was to monitor a 30-m thick dyke that remains as a dip pillar against active mining ∼90 m above our network. An M w 1.9 earthquake whose hypocenter was ∼30 m above the network occurred in the dyke. Although the mineowned geophone (4.5 Hz) network detected only five earthquakes in the surrounding 200×200×150-m3 volume within the first 150 h following the main shock, our AE network detected more than 20,000 earthquakes in the same period. More than 13,000 of these formed a distinct planar cluster (∼100×80 m2) on which the main shock hypocenter lay, suggesting that this cluster delineates the main shock rupture plane. Most of the aftershocks were presumably very small, probably as low as M ∼ −4. The aftershock cluster dipped ∼60°. This is consistent with normal faulting under a nearly vertical compression field, as indicated by nearly horizontal breakouts found in a borehole crossing the rupture plane.