著者

小笠原 宏 川方 裕則 石井 紘 中谷 正生 矢部 康男 飯尾 能久 南アフリカ金鉱山における半制御地震発生実験国際共同研究グループ

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.61, no.Supplement, pp.563-573, 2009-07-31 (Released:2013-11-21)

参考文献数

54

被引用文献数

2 3

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Experimental sites with potential earthquakes up to M ∼ 3 in coming few years are known beforehand from mining schedule at 2-3 km depths in South African gold mines, which allows us to deploy various borehole instruments including Ishii strainmeters, geophones, accelerometers and AE sensors. Deployment of these wide-dynamic-range and high-resolution observations in the past 15 years has led to many findings about the earthquake rupture and its preparation stage. High-sampling seismograms obtained at close proximity of M > 1 earthquakes have demonstrated similarities of these earthquakes to natural, greater earthquakes in many aspects, including stress drop, energy efficiency, and complexity of rupture propagation. Some of larger mine earthquakes are preceded by perceivable abnormal seismicity. However, no immediate precursors for earthquakes with M ∼ 2 were observed by our high-resolution strain and AE sensors installed within the dimension of mainshock rupture. In contrast, aseismic strain-step events that we had recently discovered were sometimes preceded by further slower forerunners. Ongoing projects bring in novel technologies such as field-scale AE monitoring and fast-response strainmeters, and novel targets including mines being flooded for closing operation.