Multidisciplinary monitoring of preparation and generation of earthquakes at M2 sources in South African gold mines

2013 Fiscal Year Final Research Report

• Project/Area Number: 21224012
• Research Category: Grant-in-Aid for Scientific Research (S)
• Allocation Type: Single-year Grants
• Research Field: Solid earth and planetary physics
• Research Institution: Ritsumeikan University
• Principal Investigator: OGASAWARA Hiroshi 立命館大学, 理工学部, 教授 (40213996)
• Co-Investigator(Kenkyū-buntansha): NAKATANI Masao 東京大学, 地震研究所, 准教授 (90345174) ; YABE Yasuo 東北大学, 理学研究科, 准教授 (30292197) ; KAWAKATA Hironori 立命館大学, 理工学部, 教授 (80346056)
• Co-Investigator(Renkei-kenkyūsha): ISHII Hiroshi (公財)地震予知総合研究振興会, 東濃地震科学研究所, 所長 (30004386) ; NAKAO Shigeru 鹿児島大学, 理学部, 准教授 (90237214) ; OKUBO Makoto (公財)地震予知総合研究振興会, 東濃地震科学研究所, 主任研究員 (50462940) ; IDE Satoshi 東京大学, 理学研究科, 教授 (90292713) ; IIO Yoshihisa 京都大学, 防災研究所, 教授 (50159547) ; KANO Yasuyuki 京都大学, 防災研究所, 助教 (30447940) ; KAME Nobuki 東京大学, 地震研究所, 准教授 (90304724) ; SATOH Takashi (独)産業技術総合研究所, 主任研究員 (90357161) ; LEI Xinglin (独)産業技術総合研究所, 主任研究員 (70358357) ; KATO Aitaro 名古屋大学, 環境学研究科, 准教授 (20359201) ; IGARASHI Toshihiro 東京大学, 地震研究所, 助教 (10334286) ; IMANISHI Kazutoshi (独)産業技術総合研究所, 研究員 (70356517) ; MORIYA Hirokazu 東北大学, 工学研究科, 准教授 (60261591)
• Project Period (FY): 2009-05-11 – 2014-03-31
• Keywords: 南アフリカ金鉱山 / 誘発地震 / 至近距離観測 / 微小破壊 / 準静的ひずみ変化 / 動的破損過程 / 絶対応力 / 断層強度

Research Abstract

Drilling > 80 holes with a total length > 2.8 km in earthquake prone areas, conducted were multi-disciplinary studies at sites (at depths > 3km or with equivalent stress) at six South African gold mines in ever-larger scale. Microfracturing associated with a magnitude (M) 2 event as well as those in highly stressed rock mass at 1.0km depth at another mine were finely delineated and seismologically analyzed in ever-greater detail. A hole intersecting an M2 hypocenter allowed the constraint of stress. A technology was introduced that allowed to measure stress at ever-larger depths or in ever-larger magnitudes, which calibrated elastic stress modelling. Pre-seismic strain change was observed for a M0 event, which was one of the other outcomes that can be obtained only from our monitoring at the closest proximity of hypocenters.

Research Products

• [Journal Article] BX CCBO in-situ stress measurements at earthquake prone areas in South African gold mines ? a summary of mini-workshop on 13 Feb 2014 (2014)
  • Author(s): Ogasawara, H., H. Kato, G. Hofmann, D. Roberts, P. Piper, T. Clements, A.K. Ward, Y. Yabe, H. Yilmaz, and R.J. Durrheim
  • Journal Title: Proceedings of ARMA2014 (Minesota University, Minneapolis) Volume: (CD-ROM) Pages: 11
  • Peer Reviewed
• [Journal Article] In situ stress measurement at earthquake prone areas in South African gold mines (2014)
  • Author(s): Ogasawara, H., H. Kato, G. Hofmann, D. Roberts, T. Clements, P. Piper, and Y. Yabe
  • Journal Title: Proceedings of 6th South African Rock Engineering Symposium SARES, Southern African Institue of Mining and Metallurgy, Johannesburg Pages: 349-358
  • Peer Reviewed
• [Journal Article] In-situ monitoring of rock mass response to mining in South African gold mines using the Ishii strainmeters (2014)
  • Author(s): Ogasawara, H., T. Katsura, G. Hofmann, Y. Yabe, M. Nakatani, M. Naoi, H. Ishii, D. Roberts, S. Nakao, M. Okubo, J. Wienand, P. Lenegan, and A.K. Ward
  • Journal Title: Proceedings of 6th South African Rock Engineering Symposium SARES, Southern African Institute of Mining and Metallurgy, Johannesburg Pages: 21-34
  • Peer Reviewed
• [Journal Article] Frequency -magnitude distribution of -3.7 < Mw <1 mining-induced earthquakes around a mining front and b value invariance with post-blast time (2013)
  • Author(s): Naoi, M., M. Nakatani, S. Horiuchi, Y. Yabe, J. Philipp, T. Kgarume, G. Morema, S. Khambule, T. Masakale, L. Ribeiro, K. Miyakawa, A. Watanabe, K. Otsuki, H. Moriya, O. Murakami, H. Kawakata, N. Yoshimitsu, A. Ward, R. Durrheim, and H. Ogasawara
  • Journal Title: Pure and Applied Geophysics
  • DOI: 10.1007/s00024-013-0721-7.
  • Peer Reviewed
• [Journal Article] Estimation of the stress state around the fault source of a Mw 2.2 earthquake in a deep gold mine in South Africa based on borehole breakout and core discing (2013)
  • Author(s): Yabe, Y., M. Nakatani, M. Naoi, T. Iida, T. Satoh, R. Durrheim, G. Hofmann, D. Roberts, H. Yilmaz, G. Morema, and H. Ogasawara
  • Journal Title: Proceedings of 6th International Symposium on In-Situ Rock Stress (Sendai, Japan) Pages: 604-613
• [Journal Article] Detection of mining-induced fractures around a stope in Ezulwini gold mine, South Africa, by using AE events with similar waveforms (2012)
  • Author(s): Moriya, H., M. Naoi, M. Nakatani, O. Murakami, T. Kgarume, A.K. Ward, R. Durrheim, J. Philipp, Y. Yabe, H. Kawakata, and H. Ogasawara
  • Journal Title: Proceedings of 21th International Acoustic Emission Symposium, Jap. Soc. for Non-Destructive Inspection, Tokyo Pages: 181-186
  • Peer Reviewed
• [Journal Article] Temporal changes in attenuation of S waves through a fault zone in a South African gold mine (2012)
  • Author(s): Yoshimitsu, N., H. Kawakata, A. Yamamoto, H. Ogasawara, and Y. Iio
  • Journal Title: Geophysical Journal International Volume: Vol.191 Pages: 1317-1324
  • DOI: 10.1111/j.1365-246X.2012.05678.x.
  • Peer Reviewed
• [Presentation] Microfractures on natural faults stressed by mining (2013)
  • Author(s): Nakatani, M
  • Organizer: The International Summer School on Earthquake Science "Diversity of Earthquakes" organized by the Earthquake Research Institute of the University of Tokyo and the Southern California Earthquake Center
  • Place of Presentation: Laforet Gora, Kanagawa, Japan
  • Year and Date: 2013-09-25
• [Presentation] A provisional plan of multiple stress measurements at a seismic source at great depth at South African gold mines (2013)
  • Author(s): Ogasawara, H., H. Kato, Y. Yabe, G. Hofmann, D. Roberts, and K. Sakaguchi
  • Organizer: "Workshop on Earthquake and Stress" in association with 6th International Symposium on In-situ Rock Stress
  • Place of Presentation: Sendai International Center, Miyagi, Japan
  • Year and Date: 2013-08-19
• [Remarks] 2013年8月26日、朝日新聞、朝刊、科学面「震源直近、動き探る 南アの金鉱、日本人チーム挑戦」。
• [Remarks] 2010年11月22日、読売新聞 とれたて!科学Monday 「南ア鉱山地震を観測-地下3000メートル超震源断層に迫る」
• [Remarks] 2010年1月12日(火)、「地震を掘り出す」、東京新聞・東京中日新聞朝刊。2009年10月31日(土)、「南アとの共同予知研究」、読売新聞朝刊
• [Remarks]
  • URL: http://www.mineseis.se.ritsumei.ac.jp/JSPS/JSPS-HOME.html