eprintid: 1385 rev_number: 16 eprint_status: archive userid: 2 dir: disk0/00/00/13/85 datestamp: 2015-03-02 08:12:43 lastmod: 2017-02-08 12:21:39 status_changed: 2015-04-27 12:10:48 type: article metadata_visibility: show creators_name: Naoi, Makoto creators_name: Ogasawara, Hiroshi creators_name: Takeuchi, Junichi creators_name: Yamamoto, Akihito creators_name: Shimoda, Naoyuki creators_name: Morishita, Ken creators_name: Ishii, Hiroshi creators_name: Nakao, Shigeru creators_name: van Aswegen, Gerrie creators_name: Mendecki, Aleksander J. creators_name: Lenegan, Patrick creators_name: Ebrahim-Trollope, Rookshana creators_name: Iio, Yoshihisa corp_creators: Graduate School of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan corp_creators: Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan corp_creators: National Instrument Corporation, Tokyo, 105-0011, Japan corp_creators: Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan corp_creators: Graduate School of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan corp_creators: Graduate School of Science and Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan corp_creators: Tono Research Institute of Earthquake Science, Mizunami, 509-6132, Japan corp_creators: Faculty of Science, Kagoshima University, Kagoshima, 892-0871, Japan corp_creators: ISS International Ltd., Stellenbosch, 7600, South Africa corp_creators: ISS International Ltd., Stellenbosch, 7600, South Africa corp_creators: ISS International Ltd., Stellenbosch, 7600, South Africa corp_creators: Geohydroseis CC, Klerksdorp, 2571, South Africa corp_creators: Disaster Prevension Research Institute, Kyoto University, Uji, 611-0011, Japan title: Small slow-strain steps and their forerunners observed in gold mine in South Africa ispublished: pub subjects: RR subjects: SMU subjects: SS divisions: EPOS-P full_text_status: none abstract: The Research Group for Semi-controlled Earthquake-generation Experiments in South African deep gold mines (SeeSA) has continuously monitored strain changes with a resolution of 24 bit 25 Hz at the Bambanani mine near Welkom. An Ishii borehole strainmeter was installed at a depth of 2.4 km near the potential M ∼ 3 earthquake source area. Instantaneous strain steps of ∼10^−4 strains associated with two M2 events were observed within a length of seismic fault. These steps were followed by significant post-seismic creep-like drift, but not preceded by forerunners. Analysis of the continuous 25 Hz data reveals many smaller steps with much longer durations (100 ms ∼ 100 s) than seen in normal earthquakes (−1 < M < 2) with source durations of 1 ms∼50 ms. Some of the especially slow steps were preceded by accelerations in strain, the maximum being as large as one-third of the step. date: 2006-04 date_type: published publication: Geophysical Research Letters volume: 33 number: 12 publisher: Wiley id_number: doi:10.1029/2006GL026507 refereed: TRUE issn: 0094-8276 official_url: http://dx.doi.org/10.1029/2006GL026507 access_IS-EPOS: limited owner: Publisher citation: Naoi, Makoto and Ogasawara, Hiroshi and Takeuchi, Junichi and Yamamoto, Akihito and Shimoda, Naoyuki and Morishita, Ken and Ishii, Hiroshi and Nakao, Shigeru and van Aswegen, Gerrie and Mendecki, Aleksander J. and Lenegan, Patrick and Ebrahim-Trollope, Rookshana and Iio, Yoshihisa (2006) Small slow-strain steps and their forerunners observed in gold mine in South Africa. Geophysical Research Letters, 33 (12). DOI: https://doi.org/10.1029/2006GL026507