Researcher basic information

• Ph. D, The University of Tokyo, Mar. 2010

• https://researchmap.jp/7000009543?lang=en

• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=201401019213405943
• https://orcid.org/0000-0001-9488-9266

• https://orcid.org/0000-0001-9488-9266

• 201401019213405943

• Natural Science, Solid earth sciences

• Bachelor's degree program, School of Science
• Master's degree program, Graduate School of Science
• Doctoral (PhD) degree program, Graduate School of Science

Research activity information

• Mar. 2025, Earth, Planets and Space, Excellent Reviewers
• 2015年度 岩の力学連合会 フロンティア賞
• 2016年度 日本地震学会若手学術奨励賞

• DiallelX: a modern fortran code for calculating network cross-correlation
  Shiro Hirano; Makoto Naoi
  Progress in Earth and Planetary Science, 12, 1, Springer Science and Business Media LLC, 08 May 2025, [Peer-reviewed]
  English, Scientific journal, Abstract
  
  In this paper, we develop a modern Fortran code to approximate network cross-correlation coefficients for seismic event detection. The code is available via an online repository. The algorithm exhibits efficient memory usage, small output size, and amenability to parallelization. Although exact NCC values are not calculated, the accuracy is deemed to be sufficient based on statistical investigation. A benchmark and practical application are also presented, suggesting the viability of performing matched filter analysis of years-long continuous multi-channel seismic data and thousands of template events on a workstation within a runtime extending from a few hours to a few days.
• Creating multidirectional fractures through particle jamming
  Yusuke Mukuhira; Ryota Goto; Noriaki Watanabe; Kazumasa Sueyoshi; Kohei Takuma; Rongchang Zhang; Tongfei Tian; Vladimir Sokolovski; Makoto Naoi; Yuko Arai; Takaaki Tomai; Masaoki Uno; Takatoshi Ito
  International Journal of Rock Mechanics and Mining Sciences, 188, 106051, 106051, Elsevier BV, Apr. 2025, [Peer-reviewed]
  English, Scientific journal
• High-resolution monitoring of hydraulically induced acoustic emission activities using neural phase picking and matched filter analysis
  Makoto Naoi; Shiro Hirano; Youqing Chen
  Progress in Earth and Planetary Science, 12, 1, Springer Science and Business Media LLC, 21 Mar. 2025, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal, Abstract
  
  Monitoring the activities of very small seismic events or acoustic emissions (AEs) by estimating their hypocenters is useful in investigating fracturing processes in laboratory experiments. Here, we proposed an analysis procedure to develop high-quality AE event catalogs using deep learning and similar waveform searches from the continuous records of AE sensors. The proposed routine comprised the following five steps: 1) automatically developing catalogs using a conventional procedure, where the short-term average-to-long-term average ratio detects transient signals, and arrival times are identified using an autoregressive model and the Akaike information criterion; 2) training a deep learning model for arrival time reading (neural phase picker) using datasets based on the Step 1 catalog; 3) reproducing the AE catalog by applying the trained neural phase picker to continuous waveform records; 4) applying template matching to continuous waveform records based on the template events listed in the catalog in Step 3; and 5) determining the precise hypocenters of template events and newly detected events in Step 4 using a relative location method based on the cross-correlation travel time reading technique. We applied this procedure to continuous AE waveforms recorded at 10 MHz sampling during hydraulic fracturing experiments, resulting in a catalog with 10 times the number of events compared to the Step 1 catalog. This reproduced catalog revealed new aspects of the fracturing process, such as the propagating fracture front and tremor-like AE activity. The proposed procedure eliminates the need for manual labeling, thereby facilitating a fully automated analysis of the observed continuous records. This technique is expected to enhance our understanding of AE sensor records in laboratory experiments.
• Neural phase picker trained on the Japan meteorological agency unified earthquake catalog
  Makoto Naoi; Koji Tamaribuchi; Kengo Shimojo; Shinya Katoh; Shukei Ohyanagi
  Earth, Planets and Space, 76, 1, Springer Science and Business Media LLC, 22 Nov. 2024, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal, Abstract
  
  As Japan is one of the most seismically active countries, seismic data from various institutions are shared in real time and made accessible via the Web to promote research. The Japan Meteorological Agency (JMA), in collaboration with the Ministry of Education, Culture, Sports, Science, and Technology, processes these data to compile a 'unified earthquake catalog' for use in the development of strategies for disaster prevention and public safety. Based on manual arrival-time measurements provided by the JMA, we retrained PhaseNet, the deep-learning phase picker, known as neural phase picker that has gained prominence in recent years, to promote the development of high-quality seismic catalogs in Japan. We utilized the PhaseNet architecture for our model and trained it using 6.1 million three-component seismic waveforms collected in 2014–2021. The performance of the original PhaseNet model, trained with data from California, was suboptimal when applied to routine Japanese data, particularly ocean-bottom seismometer records. Retraining the model with the JMA unified catalog and corresponding waveforms significantly enhanced its performance in picking the arrival times of regular and low-frequency earthquakes. Compared with the original PhaseNet, the dependency of the model on the type of seismic station was reduced by retraining and its performance for waveforms was improved even from stations not included in the training data set. The model performance varied with earthquake magnitude, highlighting the reliance on extensive data for small events in the training set. Compared with the conventional procedure, the model identified numerous events, particularly smaller ones with undetermined magnitudes when integrated into the routine automatic processing of the JMA. Furthermore, leveraging approximately ten times more training data than the California data set, we developed and trained PhaseNetWC, doubling the number of filter channels in each convolutional layer in comparison with those of the original PhaseNet. This modified phase picker surpassed the performance of its predecessor. The dissemination of these models is anticipated to enhance the analysis of routine observational data sets in Japan.
  
  Graphical Abstract
• Recent advances in earthquake seismology using machine learning
  Hisahiko Kubo; Makoto Naoi; Masayuki Kano
  Earth, Planets and Space, 76, 1, Springer Science and Business Media LLC, 28 Feb. 2024, [Peer-reviewed]
  English, Scientific journal, Abstract
  
  Given the recent developments in machine-learning technology, its application has rapidly progressed in various fields of earthquake seismology, achieving great success. Here, we review the recent advances, focusing on catalog development, seismicity analysis, ground-motion prediction, and crustal deformation analysis. First, we explore studies on the development of earthquake catalogs, including their elemental processes such as event detection/classification, arrival time picking, similar waveform searching, focal mechanism analysis, and paleoseismic record analysis. We then introduce studies related to earthquake risk evaluation and seismicity analysis. Additionally, we review studies on ground-motion prediction, which are categorized into four groups depending on whether the output is ground-motion intensity or ground-motion time series and the input is features (individual measurable properties) or time series. We discuss the effect of imbalanced ground-motion data on machine-learning models and the approaches taken to address the problem. Finally, we summarize the analysis of geodetic data related to crustal deformation, focusing on clustering analysis and detection of geodetic signals caused by seismic/aseismic phenomena.
  
  Graphical Abstract
• Efficient similar waveform search using short binary codes obtained through a deep hashing technique
  Makoto Naoi; Shiro Hirano
  Geophysical Journal International, Oxford University Press (OUP), 16 Feb. 2024, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal, Summary
  
  A similar waveform search plays a crucial role in seismology for detecting seismic events, such as small earthquakes and low-frequency events. However, the high computational costs associated with waveform cross-correlation calculations represent bottlenecks during the analysis of long, continuous records obtained from numerous stations. In this study, we developed a deep-learning network to obtain 64-bit hash codes containing information on seismic waveforms. Using this network, we performed a similar waveform search for ∼35 million moving windows developed for the 30 min waveforms recorded continuously at 10 MHz sampling rates using 16 acoustic emission transducers during a laboratory hydraulic fracturing experiment. The sampling points of each channel corresponded to those of the 5.8-year records obtained from typical seismic observations at 100 Hz sampling rates. Of the 35 million windows, we searched for windows with small average Hamming distances among the hash codes of 16 channel waveforms against template hash codes of 6057 events that were catalogued using conventional autoprocessing techniques. The calculation of average Hamming distances is 1430–1530 times faster than that of the corresponding network correlation. This hashing-based template matching enabled the detection of 23,462 additional events. We also demonstrated the feasibility of the hashing-based autocorrelation analysis, where similar event pairs were extracted without templates, by calculating the average Hamming distances for all possible pairs of the ∼35 million windows. This calculation required only 15.5 h under 120 thread parallelisation. This deep hashing approach significantly reduced the required memory compared with locality-sensitive hashing approaches based on random permutations, enabling similar waveform searching on a large-scale dataset.
• Characteristics of carbon dioxide fracturing in comparison to conventional water hydraulic fracturing: Evidence from acoustic emission monitoring of small-scale field experiments
  Tsuyoshi Ishida; Yoshinobu Kishimoto; Shuich Desaki; Makoto Naoi; Kenichiro Suzuki; Hirokazu Fujii
  International Journal of Rock Mechanics and Mining Sciences, 172, 105604, 105604, Elsevier BV, Dec. 2023, [Peer-reviewed]
  English, Scientific journal
• Source parameter estimation of acoustic emissions induced by hydraulic fracturing in the laboratory
  Makoto Naoi; Keiichi Imakita; Youqing Chen; Kazune Yamamoto; Rui Tanaka; Hironori Kawakata; Tsuyoshi Ishida; Eiichi Fukuyama; Yutaro Arima
  Geophysical Journal International, 231, 1, 408, 425, Oxford University Press ({OUP}), 21 Jun. 2022, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Stress State in the Source Region of Mw2.2 Earthquake in a Deep Gold Mine in South Africa Determined from Borehole Cores
  Yasuo Yabe; Shuhei Abe; Gerhard Hofmann; Dave Roberts; Halil Yilmaz; Hiroshi Ogasawara; Takatoshi Ito; Akio Funato; Masao Nakatani; Makoto Naoi; Raymond Durrheim
  PURE AND APPLIED GEOPHYSICS, Apr. 2022, [Peer-reviewed]
  English, Scientific journal
• Acoustic emission monitoring of hydraulic fracturing using carbon dioxide in a small-scale field experiment
  Tsuyoshi Ishida; Shuich Desaki; Yoshinobu Kishimoto; Makoto Naoi; Hirokazu Fujii
  International Journal of Rock Mechanics and Mining Sciences, 141, 104712, 104712, Elsevier BV, May 2021, [Peer-reviewed]
  English, Scientific journal
• Preparatory acoustic emission activity of hydraulic fracture in granite with various viscous fluids revealed by deep learning technique
  Rui Tanaka; Makoto Naoi; Youqing Chen; Kazune Yamamoto; Keiichi Imakita; Naofumi Tsutsumi; Akihiro Shimoda; Daiki Hiramatsu; Hironori Kawakata; Tsuyoshi Ishida; Eiichi Fukuyama; Hiroyuki Tanaka; Yutaro Arima; Shigehiro Kitamura; Daisuke Hyodo
  Geophysical Journal International, 226, 1, 493, 510, 09 Mar. 2021, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• The effect of a gouge layer on rupture propagation along brittle shear fractures in deep and high-stress mines
  S.B. Mngadi; A. Tsutsumi; Y. Onoe; M.S.D. Manzi; R.J. Durrheim; Y. Yabe; H. Ogasawara; S. Kaneki; N. Wechsler; A.K. Ward; M. Naoi; H. Moriya; M. Nakatani
  International Journal of Rock Mechanics and Mining Sciences, 137, 104454, 104454, Elsevier BV, Jan. 2021, [Peer-reviewed]
  English, Scientific journal
• Tensile-dominant fractures observed in hydraulic fracturing laboratory experiment using eagle ford shale
  Makoto Naoi; Youqing Chen; Kazune Yamamoto; Yuya Morishige; Keiichi Imakita; Naofumi Tsutumi; Hironori Kawakata; Tsuyoshi Ishida; Hiroyuki Tanaka; Yutaro Arima; Shigehiro Kitamura; Daisuke Hyodo
  Geophysical Journal International, 222, 2, 769, 780, 01 Aug. 2020, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Moment tensor analysis of acoustic emissions induced by laboratory-based hydraulic fracturing in granite
  Kazune Yamamoto; Makoto Naoi; Youqing Chen; Kengo Nishihara; Shunsuke Yano; Hironori Kawakata; Takashi Akai; Isao Kurosawa; Tsuyoshi Ishida
  Geophysical Journal International, 216, 3, 1507, 1516, 01 Mar. 2019, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• Integration of underground mapping, petrology, and high-resolution microseismicity analysis to characterise weak geotechnical zones in deep South African gold mines
  S. B. Mngadi; R. J. Durrheim; M. S.D. Manzi; H. Ogasawara; Y. Yabe; H. Yilmaz; N. Wechsler; G. Van Aswegen; D. Roberts; A. K. Ward; M. Naoi; H. Moriya; M. Nakatani; A. Ishida; SATREPS Team; ICDP DSeis Team
  International Journal of Rock Mechanics and Mining Sciences, 114, 79, 91, Feb. 2019, [Peer-reviewed]
  English, Scientific journal
• In-situ acoustic emission monitoring in mines
  G. Manthei; K. Plenkers; J. Philipp; M. Naoi; H. Moriya; M. Nakatani
  53rd U.S. Rock Mechanics/Geomechanics Symposium, 2019
  International conference proceedings
• Crack Expansion and Fracturing Mode of Hydraulic Refracturing from Acoustic Emission Monitoring in a Small-scale Field Experiment
  T. Ishida; W. Fujito; H. Yamashita; M. Naoi; H. Fuji; K. Suzuki; H. Matsui
  Rock Mechanics and Rock Engineering, Jan. 2019, [Peer-reviewed]
  English, Scientific journal
• Emergence and disappearance of very small repeating earthquakes on a geological fault in a gold mine in South Africa
  Junya Yamaguchi; Makoto Naoi; Masao Nakatani; Hirokazu Moriya; Toshihiro Igarashi; Osamu Murakami; Yasuo Yabe; Raymond Durrheim; Hiroshi Ogasawara
  Tectonophysics, 747-748, 318, 326, Nov. 2018, [Corresponding author]
  English, Scientific journal
• Method for visualizing fractures induced by laboratory-based hydraulic fracturing and its application to shale samples
  Youqing Chen; Makoto Naoi; Yuto Tomonaga; Takashi Akai; Hiroyuki Tanaka; Sunao Takagi; Tsuyoshi Ishida
  Energies, 11, Aug. 2018, [Peer-reviewed]
  English, Scientific journal
• Monitoring hydraulically-induced fractures in the laboratory using acoustic emissions and the fluorescent method
  Makoto Naoi; Youqing Chen; Kengo Nishihara; Kazune Yamamoto; Shunsuke Yano; Shota Watanabe; Yuta Morishige; Hironori Kawakata; Takashi Akai; Isao Kurosawa; Tsuyoshi Ishida
  International Journal of Rock Mechanics and Mining Sciences, 104, 53, 63, Elsevier Ltd, 01 Apr. 2018, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Hybrid focal mechanism determination: Constraining focal mechanisms of injection induced seismicity using in situ stress data
  Y. Mukuhira; K. Fuse; M. Naoi; M. C. Fehler; H. Moriya; T. Ito; H. Asanuma; M. O. Häring
  Geophysical Journal International, 215, 2, 1427, 1441, 2018, [Peer-reviewed]
  English, Scientific journal
• 南アフリカ大深度金鉱山での微小破壊観測による震源の物理の研究
  直井 誠
  地震 第2輯, 71, 0, 公益社団法人 日本地震学会, Jan. 2018, [Peer-reviewed], [Lead author, Corresponding author]
  Japanese, Scientific journal
• 講演 水圧破砕フラクチャーの可視化技術 (開発・生産部門シンポジウム プロジェクト価値最大化に向けて : フィールドライフを通じての技術的アプローチ)
  陳 友晴; 直井 誠; 石田 毅; 赤井 崇嗣; 黒澤 功; 高木 是
  石油技術協会誌 = Journal of the Japanese Association for Petroleum Technology, 82, 6, 石油技術協会, Jan. 2017, [Peer-reviewed]
  Japanese, Scientific journal
• Features of CO2 fracturing deduced from acoustic emission and microscopy in laboratory experiments
  Tsuyoshi Ishida; Youqing Chen; Ziad Bennour; Hiroto Yamashita; Shuhei Inui; Yuya Nagaya; Makoto Naoi; Qu Chen; Yoshiki Nakayama; Yu Nagano
  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 121, 11, 8080, 8098, Nov. 2016, [Peer-reviewed]
  English, Scientific journal
• Acoustic Emission Monitoring for Mitigating Seismic Risks in Deep Gold Mines in South Africa
  Makoto Naoi; Masao Nakatani; Hirokazu Moriya; Yasuo Yabe
  International Journal of the JSRM, 12, 1, 19, 22, Japanese Society of Rock Mechanics, Jun. 2016, [Lead author, Corresponding author]
  English, Scientific journal, Gold mines in South Africa have mining depths of up to ~4 km. Mining in such depths under high-stress conditions induces many earthquakes, which pose serious hazard to mine workers. To mitigate seismic risks and to understand the role ofmicroearthquakes in earthquake generation processes, we have conducted ultra-sensitive seismic observations, which allow acoustic emissions (AEs) to be detected down to M_W −5 (typical rupture size ~ several centimeters), at two South African gold mines. We have found out various modes of AE activity previously unknown from conventional seismic networks (detectability only down to M_W ~ −1): AE activity before and after an M_W 2.2 earthquake, AE activity likely reflecting damage accumulation processes ahead of an advancing mining front, and AEs occurring steadily along geological faults. This paper summarizes these findings, which received the fiscal 2016 frontier award of the Japanese Society for Rock Mechanics (JSRM).
• Unexpectedly frequent occurrence of very small repeating earthquakes (-5.1 <= M-w <=-3.6) in a South African gold mine: Implications for monitoring intraplate faults
  Makoto Naoi; Masao Nakatani; Toshihiro Igarashi; Kenshiro Otsuki; Yasuo Yabe; Thabang Kgarume; Osamu Murakami; Thabang Masakale; Luiz Ribeiro; Anthony Ward; Hirokazu Moriya; Hironori Kawakata; Shigeru Nakao; Raymond Durrheim; Hiroshi Ogasawara
  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 120, 12, 8478, 8493, Dec. 2015, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Delineation of large localized damage structures forming ahead of an active mining front by using advanced acoustic emission mapping techniques
  Hirokazu Moriya; Makoto Naoi; Masao Nakatani; Gerrie van Aswegen; Osamu Murakami; Thabang Kgarume; Anthony K. Ward; Raymond J. Durrheim; Joachim Philipp; Yasuo Yabe; Hironori Kawakata; Hiroshi Ogasawara
  INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 79, 157, 165, Oct. 2015, [Peer-reviewed]
  English, Scientific journal
• Nucleation process of an M2 earthquake in a deep gold mine in South Africa inferred from on-fault foreshock activity
  Yasuo Yabe; Masao Nakatani; Makoto Naoi; Joachim Philipp; Christoph Janssen; Takayoshi Watanabe; Taishi Katsura; Hironori Kawakata; Dresen Georg; Hiroshi Ogasawara
  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 120, 8, 5574, 5594, Aug. 2015, [Peer-reviewed]
  English, Scientific journal
• Steady activity of microfractures on geological faults loaded by mining stress
  Makoto Naoi; Masao Nakatani; Kenshiro Otsuki; Yasuo Yabe; Thabang Kgarume; Osamu Murakami; Thabang Masakale; Luiz Ribeiro; Anthony Ward; Hirokazu Moriya; Hironori Kawakata; Raymond Durrheim; Hiroshi Ogasawara
  TECTONOPHYSICS, 649, 100, 114, May 2015, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Quasi-static slip patch growth to 20 m on a geological fault inferred from acoustic emissions in a South African gold mine
  Makoto Naoi; Masao Nakatani; Thabang Kgarume; Sifiso Khambule; Thabang Masakale; Luiz Ribeiro; Joachim Philipp; Shigeki Horiuchi; Kenshiro Otsuki; Koji Miyakawa; Atsushi Watanabe; Hirokazu Moriya; Osamu Murakami; Yasuo Yabe; Hironori Kawakata; Nana Yoshimitsu; Anthony Ward; Raymond Durrheim; Hiroshi Ogasawara
  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 120, 3, 1692, 1707, Mar. 2015, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Frequency-Magnitude Distribution of-3.7 <= M-W <= 1 Mining-Induced Earthquakes Around a Mining Front and b Value Invariance with Post-Blast Time
  Makoto Naoi; Masao Nakatani; Shigeki Horiuchi; Yasuo Yabe; Joachim Philipp; Thabang Kgarume; Gilbert Morema; Sifiso Khambule; Thabang Masakale; Luiz Ribeiro; Koji Miyakawa; Atsushi Watanabe; Kenshiro Otsuki; Hirokazu Moriya; Osamu Murakami; Hironori Kawakata; Nana Yoshimitsu; Anthony Ward; Ray Durrheim; Hiroshi Ogasawara
  PURE AND APPLIED GEOPHYSICS, 171, 10, 2665, 2684, Oct. 2014, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Twenty Thousand Aftershocks of a Very Small (M 2) Earthquake and Their Relation to the Mainshock Rupture and Geological Structures
  Makoto Naoi; Masao Nakatani; Yasuo Yabe; Grzegorz Kwiatek; Toshihiro Igarashi; Katrin Plenkers
  BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, 101, 5, 2399, 2407, Oct. 2011, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• Observation of numerous aftershocks of an Mw 1.9 earthquake with an AE network installed in a deep gold mine in South Africa
  Yasuo Yabe; Joachim Philipp; Masao Nakatani; Gilbert Morema; Makoto Naoi; Hironori Kawakata; Toshihiro Igarashi; Georg Dresen; Hiroshi Ogasawara
  Earth, Planets and Space, 61, 10, e49, e52, Oct. 2009, [Peer-reviewed]
  English, Scientific journal
• Small slow-strain steps and their forerunners observed in gold mine in South Africa
  M Naoi; H Ogasawara; J Takeuchi; A Yamamoto; N Shimoda; K Morishita; H Ishii; S Nakao; G van Aswegen; AJ Mendecki; P Lenegan; R Ebrahim-Trollope; Y Iio
  GEOPHYSICAL RESEARCH LETTERS, 33, 12, Jun. 2006, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal

• Hackathon on Large Language Model and Earthquake Research
  Hisahiko KUBO; Stephen WU; Masayuki KANO; Shinya KATOH; Atsuko OANA; Tomohisa OKAZAKI; Nozomi OKADA; Nobuki KAME; Yuki KODER; Dye SK SATO; Takahiro SHIINA; Kengo SHIMOJO; Koji TAMARIBUCHI; Makoto NAOI; Ryuichi NISHIYAMA; Kazuro HIRAHARA; Takashi MIYAMOTO; Masumi YAMADA, Proceedings of the Annual Conference of JSAI, JSAI2025, 2K1-OS-6-01, Jul. 2025, [Domestic magazines]
  The Japanese Society for Artificial Intelligence, Japanese, Summary national conference
• Constraint on the range of the focal mechanism of microseismicity with in-situ stress information
  椋平祐輔; 直井誠; 森谷祐一; 伊藤高敏; 浅沼宏; HAERING Markus O., 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集(CD-ROM), 2020, 2020
• Constraint on the range of the focal mechanism of microseismicity with In-situ Stress Information
  椋平祐輔; 直井誠; 森谷祐一; 伊藤高敏; 浅沼宏; HAERING Markus O., 石油技術協会誌(CD-ROM), 85, 1-6, 2020
• Waveform feature extraction and similar waveform detection by Locality Sensitive Hashing
  駒形亮太; 平野史朗; 川方裕則; 直井誠, 日本地球惑星科学連合大会予稿集(Web), 2020, 2020
• Source parameter estimation of hydraulically-induced acoustic emissions in the laboratory
  直井誠; 今北啓一; CHEN Youqing; 田中塁; 山本和畝; 川方裕則; 石田毅; 福山英一; 有馬雄太郎, 日本地球惑星科学連合大会予稿集(Web), 2020, 2020
• Determination of P-wave first motion polarities and moment tensors for hydraulically-induced AEs using CNN technique
  田中塁; 直井誠; CHEN Youqing; 山本和畝; 今北啓一; 堤直史; 下田晃嘉; 平松大樹; 川方裕則; 石田毅; 福山英一; 田中浩之; 有馬雄太郎; 北村重浩; 兵藤大祐, 日本地震学会秋季大会講演予稿集(CD-ROM), 2020, 2020
• In-situ stress constraints on the focal mechanisms of induced seismicity
  Y. Mukuhira; T. Ito; M.C. Fehler; M. Naoi; H. Moriya; H. Asanuma; M. O. Häring, Proc. ISRM2019, 1380, 1387, Sep. 2019, [Peer-reviewed]
  English
• 地殻応力情報を用いた微小地震の断層面解範囲絞り込み
  椋平祐輔; 直井誠; FEHLER Michael C.; 森谷祐一; 伊藤高敏; 浅沼宏; HAERING Markus O., 日本地熱学会学術講演会講演要旨集, 2019, 2019
• 真三軸圧縮応力状態室内水圧破砕実験により頁岩中に造成されるき裂観察
  堤直史; CHEN Youqing; 直井誠; 森重有矢; 今北啓一; 山本和畝; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎, 資源・素材学会春季大会(Web), 2019, 2019
• 水圧破砕によって頁岩供試体中に造成された亀裂とその周辺領域の顕微鏡観察
  CHEN Youqing; 直井誠; 堤直史; 森重有矢; 平松大樹; 山本和畝; 今北啓一; 下田晃嘉; 田中塁; 川方裕則; 石田毅; 田中浩之; 北村重浩; 有馬雄太郎; 兵藤大祐, 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集, 2019, 2019
• 異なる岩種の供試体を用いた室内水圧破砕実験
  山本和畝; 山本和畝; 直井誠; CHEN Youqing; 下田晃嘉; 今北啓一; 田中塁; 堤直史; 平松大樹; 森重有矢; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 兵藤大祐, 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集, 2019, 2019
• AE活動及びモーメントテンソル解析による破砕流体粘度が水圧破砕に及ぼす影響の検討
  田中塁; 直井誠; CHEN Youqing; 山本和畝; 今北啓一; 堤直史; 下田晃嘉; 平松大樹; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 北村重浩; 兵藤大祐, 日本地震学会秋季大会講演予稿集(CD-ROM), 2019, 2019
• 室内水圧破砕実験時に生じるAcoustic Emissionの絶対規模とコーナー周波数の推定
  今北啓一; 直井誠; CHEN Youqing; 山本和畝; 森重有矢; 堤直史; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 北村重浩; 兵藤大祐, 日本地震学会秋季大会講演予稿集(CD-ROM), 2019, 2019
• 水圧破砕亀裂可視化研究のための真三軸水圧破砕実験システムの構築(第2報)
  CHEN Youqing; 堤直史; 平松大樹; 直井誠; 山本和畝; 今北啓一; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎, 日本材料学会学術講演会講演論文集, 68th, 2019
• 南アフリカ大深度金鉱山における微小破壊観測
  直井誠; 中谷正生; 矢部康男; 森谷祐一, 地盤工学研究発表会発表講演集(CD-ROM), 53rd, 2018
• イーグルフォード頁岩供試体に対する,AE計測と蛍光観察による水圧破砕造成亀裂の観察
  今北啓一; 直井誠; CHEN Youqing; 山本和畝; 森重有矢; 堤直史; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 兵藤大祐, 資源・素材学会春季大会(Web), 2018, 2018
• 水圧破砕亀裂可視化研究のための真三軸水圧破砕実験システムの構築
  CHEN Youqing; 森重有矢; 堤直史; 直井誠; 山本和畝; 今北啓一; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎, 日本材料学会学術講演会講演論文集, 67th, 2018
• イーグルフォード頁岩供試体を用いたAE計測と蛍光観察による水圧破砕造成き裂の観察
  今北啓一; 直井誠; CHEN Youqing; 山本和畝; 森重有矢; 堤直史; 石田毅; 川方裕則; 田中浩之; 有馬雄太郎; 兵藤大祐, 石油技術協会誌, 83, 4, 2018
• 水圧破砕によって頁岩供試体中に発達する亀裂の可視化と顕微鏡観察
  CHEN Youqing; 森重有矢; 堤直史; 直井誠; 山本和畝; 今北啓一; 石田毅; 川方裕則; 田中浩之; 有馬雄太郎; 兵藤大祐, 石油技術協会誌, 83, 4, 2018
• 水圧破砕亀裂の可視化研究
  CHEN Youqing; 直井誠; 川方裕則; 石田毅; 赤井崇嗣; 田中浩之; 有馬雄太郎; 高木是, 資源・素材(Web), 2018, 2018
• 水圧破砕によって頁岩供試体中に発達する亀裂の可視化と顕微鏡観察
  CHEN Youqing; 森重有矢; 堤直史; 直井誠; 山本和畝; 今北啓一; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 兵藤大祐, 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集, 2018, 2018
• イーグルフォード頁岩供試体を用いたAE計測と蛍光観察による水圧破砕造成き裂の観察
  今北啓一; 直井誠; CHEN Youqing; 山本和畝; 森重有矢; 堤直史; 川方裕則; 石田毅; 田中浩之; 有馬雄太郎; 兵藤大祐, 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集, 2018, 2018
• 室内水圧破砕実験中に生じるAEの絶対規模推定
  直井誠; 今北啓一; 山本和畝; 川方裕則; CHEN Youqing; 森重有矢; 堤直史; 石田毅; 田中浩之; 有馬雄太郎; 兵藤大祐, 日本地球惑星科学連合大会予稿集(Web), 2018, 2018
• Observational studies in South African mines to mitigate seismic risks
  Durrheim, R.J; Ogasawara, H; M. Nakatani; Y. Yabe; M. Naoi; H. Moriya; A. Cichowicz; T. Satoh; H. Kawakata; A. Milev; T. Kgarume; V.Z. Brink; A.K. Ward; L. Ribeiro; M.S.D. Manzi; S. Mngadi; the SATREPS Team, Proc. Afrirock Symposium 2017 (ISRM), 2017-October, 175-186, 188, Sep. 2017
• 室内水圧破砕実験におけるき裂造成メカニズムのモーメントテンソル解析による検討
  山本和畝; 直井誠; 西原健吾; CHEN Youqing; 藤戸航; 川方裕則; 赤井崇嗣; 黒澤功; 石田毅, 石油技術協会誌, 82, 4, 2017
• 室内水圧破砕実験におけるき裂造成メカニズムのモーメントテンソル解析による検討
  山本和畝; 直井誠; 西原健吾; CHEN Youqing; 藤戸航; 川方裕則; 赤井崇嗣; 黒澤功; 石田毅, 石油技術協会特別講演会・春季講演会(シンポジウム・個人講演)要旨集, 2017, 2017
• P波速度異方性の卓越方向が異なる花崗岩を用いた室内水圧破砕実験
  山本和畝; 直井誠; 西原健吾; CHEN Youqing; 渡邉翔太; 森重有矢; 藤戸航; 川方裕則; 赤井崇嗣; 黒澤功; 石田毅, 資源・素材学会春季大会(Web), 2017, 2017
• 室内水圧破砕実験時に発生するAcoustic Emissionに対するモーメントテンソル解析の試み
  直井誠; 西原健吾; 山本和畝; 矢野俊介; 藤戸航; CHEN Youqing; 石田毅; 川方裕則; 赤井崇嗣; 黒澤功, 日本地球惑星科学連合大会予稿集(Web), 2017, 2017
• Injection of Supercritical Carbon Dioxide into Granitic Rock and its Acoustic Emission Monitoring
  Tsuyoshi Ishida; Shuich Desaki; Hiroto Yamashita; Shuhei Inui; Makoto Naoi; Hirokazu Fujii; Tatsuo Katayama, ISRM EUROPEAN ROCK MECHANICS SYMPOSIUM EUROCK 2017, 191, 476, 482, 2017, [Peer-reviewed]
  English
• 南アフリカCooke4金鉱山地下1kmの切羽沿いに密集する微小破壊の空間分布詳細構造
  山形直毅; 直井誠; 中谷正生; 森谷祐一; 大槻憲四郎; KGARUME Thabang; PHILIPP Joachim; 村上理; MASAKALE Thabang; RIBEIRO Luiz; 矢部康男; 川方裕則; WARD Anthony; 石田毅; DURRHEIM Ray; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2016, 2016
• 南アフリカ金鉱山地表下1kmにおける薄板状鉱脈の採掘で誘発されるアコースティック・エミッションの観測
  直井誠; 中谷正生; 森谷裕一; KGARUME Thabang; 村上理; 大槻憲四郎; PHILIP Joachim; MASAKALE Thabang; RIBEIRO Luiz; 矢部康男; 川方裕則; WARD Anthony; DURRHEIM Raymond; DURRHEIM Raymond; 小笠原宏, 資源・素材学会春季大会(Web), 2016, 2016
• 南アフリカ大深度金鉱山の地質断層上で観測されたRepeating Earthquakeの出現と消失
  山口純弥; 直井誠; 中谷正生; 森谷祐一; KGARUME Thabang; 五十嵐俊博; 村上理; MASAKALE Thabang; 矢部康男; 大槻憲四郎; 川方裕則; 石田毅; WARD Anthony; DURRHEIM Ray; DURRHEIM Ray; 小笠原宏, 日本地球惑星科学連合大会予稿集(Web), 2016, 2016
• Monitoring of microseismicity in deep gold mines in South Africa
  Yabe, Y; M. Nakatani; M. Naoi; H. Moriya; J. Philipp; C. Janssen; H. Kawakata; R. Durrheim; G. Dresen; H. Ogasawara, Schatzalp Induced Seismicity workshop, 10 Mar. 2015, [Peer-reviewed], [Invited]
  English
• 南アフリカCooke4金鉱山1km深における,Mw≧0の地震に先行する時期に起こったAcoustic Emissionの活動度
  北代雅明; 直井誠; 中谷正生; 森谷祐一; 大槻憲四郎; KGARUME Thabang; PHILIPP Joachim; 村上理; MASAKALE Thabang; RIBEIRO Luiz; 矢部康男; 川方裕則; WARD Anthony; 石田毅; DURRHEIM Ray; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2015, 2015
• 南アフリカ金鉱山地下1kmの採掘空洞前方で観察された板状分布を示すAE活動のb値と空間相関長の時間変化
  山形直毅; 直井誠; 中谷正生; 森谷祐一; 大槻憲四郎; KGARUME Thabang; PHILIPP Joachim; 村上理; MASAKALE Thabang; RIBEIRO Luiz; 矢部康男; 川方裕則; WARD Anthony; 石田毅; DURRHEIM Ray; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2015, 2015
• 南アフリカ大深度金鉱山での地震被害低減のための震源至近距離観測研究-SATREPS等6カ年の活動のまとめ-
  小笠原宏; 加藤春實; HOFMANN Gerhard; 矢部康男; CICHOWICZ Artur; 堀内茂木; 大久保慎人; 中谷正生; 直井誠; 森谷祐一; 村上理; 佐藤隆司; 川方裕則; 吉光奈奈; DURRHEIM Ray; DURRHEIM Ray; WARD Anthony; MILEV Alex; 山口照寛; 中尾茂; 伊藤高敏; VAN ASWEGEN Gerrie, 日本地震学会秋季大会講演予稿集, 2015, 2015
• 南アフリカCooke 4金鉱山における微小破壊観測-SATREPS計画5カ年のまとめ-
  直井誠; 中谷正生; 森谷祐一; 大槻憲四郎; KGARUME Thabang; PHILIPP Joachim; 村上理; MASAKALE Thabang; RIVEIRO Luiz; 矢部康男; 川方裕則; WARD Anthony; DURRHEIM Ray; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2015, 2015
• Observational studies of the rock mass response to mining in highly stressed gold mines in South Africa
  Ogasawara, H; M. Nakatani; R.J. Durrheim; M. Naoi; Y. Yabe; H. Moriya; G.F. Hofmann; C. Stander; D.P. Roberts; P. de Bruin; J. Oelofse; H. Kato; A. Cichowicz; D. Birch; D. Ngobeni; A. Milev; T. Kgarume; T. Satoh; S. Horiuchi; H. Kawakata; O. Murakami; N. Yoshimitsu; A.K. Ward; J. Wienand; P. Lenegan; H. Yilmaz; S. Mngadi; P.S. Piper; T.N. Clements; S. Nakao; M. Okubo; H. Ishii; A.V. Visser, Proceedings of 7th International Congress on Deep and High Stress Mining, Sudbury, Canada, 16-18 September 2014, 123-137, Sep. 2014
• Acoustic Emissions Down to Magnitude Mw = −5 Delineating Damages Around Mining Stopes and Pre-existing Faults: Spatial Distribution, Temporal Change and Source Parameters
  Makoto Naoi; Masao Nakatani; Hirokazu Moriya; Kenshiro Otsuki; Yasuo Yabe; Osamu Murakami; Hironori Kawakata; Hiroshi Ogasawara, Institute of Mine Seismology 24th Seminar on Monitoring & Modelling the Seismic Rock Mass Response to Mining, 05 May 2014, [Peer-reviewed]
  English
• In-situ monitoring of rock mass response to mining in South African gold mines using the Ishii strainmeters
  Ogasawara, H; T. Katsura; G. Hofmann; Y. Yabe; M. Nakatani; M. Naoi; H. Ishii; D. Roberts; S. Nakao; M. Okubo; J. Wienand; P. Lenegan; A.K. Ward, Proceedings of the Sixth South African Rock Engineering Symposium 2014, 21-34, May 2014
• Observational studies in South African mines to mitigate seismic risks: a mid-term review of the five-year SATREPS project
  Durrheim, R.J; H. Ogasawara; M. Nakatani; Y. Yabe; A.M. Milev; A. Cichowicz; H. Kawakata; H. Moriya; M. Naoi; T. Kgarume; O. Murakami; A.V.Z Brink; G. Ferreira; G. Henry; R. Teleka; J. Kuijpers; S. Mngadi; A Ward; J. Wienand; the SATREPS; Research Group, Proceedings of the Sixth South African Rock Engineering Symposium 2014, 241-250, May 2014
• Observational studies in South African mines to mitigate seismic risks: implications for mine safety and tectonic earthquakes
  Raymond Durrheim; Hiroshi Ogaswara; Masao Nakatani; Yasuo Yabe; Alexander Milev; Artur Cichowicz; Hironori Kawakata; Hirokazu Moriya; Makoto Naoi; Thabang Kgarume; Osamu Murakami; Siyanda Mngadi, European Geosciences Union General Assembly 2014, EGU2014-13713, 29 Apr. 2014, [Peer-reviewed]
  English
• 断層透過波モニタリングで観測された透過弾性波の変化-南アフリカEzulwini鉱山
  川方裕則; 吉光奈奈; 吉光奈奈; 中谷正生; PHILIPP Joachim; 直井誠; WARD Anthony; 土井一生; MASAKALE Thabang; DURRHEIM Raymond; RIBEIRO Luiz; MOREMA Sylvester; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2014, 2014
• コーダ波スペクトル比法を用いた南アフリカEzulwini鉱山採掘前線における微小破壊の応力降下量推定
  村上理; 川方裕則; 佐々木裕哉; 直井誠; 中谷正生; PHILIPP Joachim; MASAKALE Thabang; KGARUME Thabang; RIBEIRO Luiz; 矢部康男; 森谷祐一; WARD Anthony; DURRHEIM Raymond; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2014, 2014
• Acoustic Emission Monitoring in South African Deep Gold Mines
  直井 誠, 水曜会誌, 24, 7, 830, 834, Jan. 2014
  京都大学工学部水曜会, Japanese
• 南アフリカ金鉱山地下1km深において,載荷される断層上で観察された-5.1≦Mw≦-3.6の繰り返し地震
  直井誠; 中谷正生; 大槻憲四郎; KGARUME Thabang; PHILIPP Joachim; MASAKALE Thabang; RIBEIRO Luiz; 森谷祐一; 村上理; 矢部康男; 川方裕則; WARD Anthony; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2013, 7, 01 Oct. 2013
  Japanese
• In-situ monitoring and modelling of the rock mass response to mining: Japanese-South African collaborative research
  Ogasawara, H; H. Moriya; M. Naoi; Y. Yabe; 目; 研究協力, Proc. 8th Int. Symp. Rockburst and Induced Seismicity in Mines, 51-60, Sep. 2013
• 能動震源を用いた南アフリカ金鉱山微小破壊観測網のセンサー特性の時間変化の推定
  村上理; 川方裕則; 吉光奈奈; 吉光奈奈; 中谷正生; 直井誠; PHILIPP Joachim; MASAKALE Thabang; KGARUME Thabang; RIBEIRO Luiz; 森谷祐一; 矢部康男; WARD Anthony; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2013, 2013
• 断層透過弾性波のモニタリング-南アフリカCooke4金鉱山
  川方裕則; 吉光奈奈; 吉光奈奈; 中谷正生; PHILIPP Joachim; 土井一生; 直井誠; 村上理; WARD Anthony; MOREMA Gilbert; VISSER Vlok; KHAMBULE Sifiso; MASAKALE Thabang; MILEV Alex; DURRHEIM Ray; RIBEIRO Luiz; WARD Mike; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2013, 2013
• コーダ波を用いた坑道検出の試み-南アフリカCooke4鉱山観測サイト
  今川祥太; 川方裕則; 土井一生; 吉光奈奈; 吉光奈奈; 村上理; 中谷正生; 直井誠; PHILLIPP Joachim; WARD Anthony; MOREMA Gilbert; VISSER Vlok; KHAMBULE Sifiso; MASAKALE Thabang; MILEV Alex; DURRHEINR Ray; RIBEIRO Luiz; WARDMike; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2013, 2013
• Detection of mining-induced fractures associated with stress perturbation around a stope in Ezulwini gold mine, South Africa, by using AE events.
  Hirokazu Moriya; Makoto Naoi; Masao Nakatani; Osamu Murakami; Thabang Kgarume; Anthony K. Ward; Ray Durrheim; Joachim Philipp; Yasuo Yabe; Hironori Kawakata; Hiroshi Ogasawara, Proc. 6th International Symposium on In-Situ Rock Stress, 598, 603, 2013
  We applied advanced mapping techniques to more than 290,000 acoustic emission (AE) events recorded by a monitoring network around a stope in the Cooke 4 shaft pillsr in South Africa (previously known as Ezulwini gold mine) during mining in July–September 2011. We first applied the joint hypocenter determination (JHD) method to compensate for systematic recording station errors. Next, we applied the collapsing method to the output of the JHD method, which revealed steeply dipping planar seismic structures with dip dimensions of 9.5–23 m. The results of our study demonstrate that advanced AE mapping techniques can be used to delineate the fracture zones that develop in rock masses ahead of the mining face during mining., English
• 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
  Yabe, Y; M. Nakatani; M. Naoi; T. Iida; T. Satoh; R. Durrheim; G. Hofmann; D. Roberts; H. Yilmaz; G. Morema; H. Ogasawara, Proc. 6th Int. Symp. on In-Situ Rock Stress, 604, 613, 2013
  To constrain the stress state around the fault source, we drilled a hole penetrating the source area of a Mw 2.2 earthquake that occurred at a depth of about 3.5 km in a deep gold mine in South Africa. The hypocenters of the mainshock and aftershocks were located in a gabbroic dyke, called the Pink and Green (PG) dyke, that had intruded the quartzite host rock. The aftershocks clearly delineated the fault plane of the mainshock. The 90 m long hole was drilled from an access tunnel in the footwall of the fault. It intersected with the fault about 70 m from the borehole collar and about 8 m from the mainshock hypocenter. The borehole had a shallow incline of 22 ̊. The angle between the hole and the fault plane determined from the aftershock distribution was 49 ̊. We used a video camera to film the borehole wall and logged core samples. Compression along the borehole axis (Sz) and the maximum (Sx) and the minimum (Sy) compressions in the plane normal to the borehole were constrained by the existence or absence of borehole breakouts and/or core discings. The estimated stresses in the quartzite were Sx~110 MPa, Sy~100 MPa and Sz~42 MPa. In PG dyke in the footwal, English
• Quasi-static fault growth in a gabbro sample retrieved from a South African deep gold mine revealed by multi-channel AE monitoring
  Satoh, T; X. Lei; M. Nakatani; Y. Yabe; M. Naoi; G. Morema, Proc. 8th Internat. Symp. Rockburst and Seismicity in Mines, 61, 66, 2013
  Using a gabbro sample retrieved from the Mponeng gold mine, South Africa, at about 3 km depth, a triaxial compression experiment was conducted and the space-time distribution of acoustic emission (AE) events was investigated in detail. The sample was cored from a dyke of about 30 m thick where a mining induced earthquake of magnitude M = 2 occurred on 27 December, 2007. Little changes in P-wave velocity and almost linear strain response during hydrostatic compression to the pre-determined confining pressure (75 MPa) suggest that the sample contains few pre-existing microcracks. Microscope image of thin section of this rock shows strong foliation structures. The sample was loaded to fracture under a constant confining pressure of 75 MPa, and fractured in a brittle manner with a steeply inclined fracture plane. We could locate hypocenters of sufficient number of AE events until the final dynamic rupture started. From the space-time distribution of AE events, we clearly found that the fault nucleated in an upper part of the sample and extended quasi-statically downward along the final fracture plane. Growth rate of the fault increased with time, and its area had reached to 20×50 mm2, English
• Magnitude-frequency distributions of AEs associated with the mining front and pre-existing faults – cases from SATREPS array operating in a South African gold mine
  Makoto Naoi; Masao Nakatani; Joachim Philipp; Shigeki Horiuchi; Kenshiro Otsuki; Thabang Kgarume; Gilbert Morema; Sifiso Khambule; Thabang Masakale; Koji Miyakawa; Atsushi Watanabe; Moriya Hirokazu; Osamu Murakami; Yasuo Yabe; Hironori Kawakata; Nana Yoshimitsu; Hiroshi Ogasawara, Proc. European Center for Geodynamics and Seismology Workshop, 01 Nov. 2012, [Peer-reviewed]
  English
• 南アフリカ金鉱山における微小破壊(-3.7≦Mw≦1.3)の規模別頻度分布と採掘発破前後のb値の安定性
  直井誠; 中谷正生; PHILIPP Joachim; 堀内茂木; 大槻憲四郎; KGARUME Thabang; MOREMA Gilbert; KHAMBULE Sifiso; MASAKALE Thabang; 宮川幸治; 渡邉篤志; 森谷祐一; 村上理; 矢部康男; 川方裕則; 吉光奈奈; WARD Tony; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2012, 169, 01 Oct. 2012
  Japanese
• 南アフリカ金鉱山地下1km深で観察された,クラックが準静的に20mまで成長したことを示唆するAE活動
  直井誠; 中谷正生; PHILIPP Joachim; 堀内茂木; 大槻憲四郎; KGARUME Thabang; MOREMA Gilbert; KHAMBULE Sifiso; MASAKALE Thabang; 宮川幸治; 渡邉篤志; 森谷祐一; 村上理; 矢部康男; 川方裕則; 吉光奈奈; WARD Tony; DURRHEIM Ray; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2012, 26, 01 Oct. 2012
  Japanese
• Establishment of SATREPS experimental sites in South African gold mines to monitor phenomena associated with earthquake nucleation and rupture
  Durrheim, R.J; H. Ogasawara; M. Nakatani; Y. Yabe; A.M. Milev; A. Cichowicz; H. Kawakata; O. Murakami; M. Naoi; N. Yoshimitsu; T. Kgarume; the SATREPS Research Group, Proceedings of the sixth International Seminar on Deep and High Stress Mining, 23-30 March 2012, Perth, Australia (ed. Yves Potvin), 173-187, Mar. 2012
• コーダ波を用いた坑道検出の試み-南アフリカEzulwini金鉱山観測サイト-
  今川祥太; 川方裕則; 土井一生; 吉光奈奈; 村上理; 中谷正生; 直井誠; PHILIPP Joachim; WARD Tony; MEREMA Gilbert; VISSER Vlok; KHAMBULE Sifiso; MASAKALE Thabang; MILEV Alex; DURRHEIM Ray; RIBEIRO Luiz; WARD Mike; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2012, 2012
• Detection of mining-induced fractures around a stope in Ezulwini gold mine, South Africa, by using AE events with similar waveforms
  Moriya, H; M. Naoi; M. Nakatani; O. Murakami; T. Kgarume; A.K. Ward; R. Durrheim; J. Philipp; Y. Yabe; H. Kawakata; H. Ogasawara, Progress in Acoustic Emission, XVI, 181, 186, 2012
  The ability to predict rock failure is desirable for the prevention of disasters in mines. The acoustic emission (AE) method is a well-known tool for monitoring fracture growth in rock masses that is used to help ensure safety during excavations. In mines, AE can indicate the location of fractures and damage zones. If AE could be used to detect the initiation and extension of fractures in rock masses and determine their precise source locations, that information would be helpful in forecasting the locations of rock failure. A study of AE in the Ezulwini gold mine in South Africa has been conducted under the Japan–South Africa collaborative project titled “Observational studies to mitigate seismic risks in mines” [1, 2], in which a large number of events have been detected around the mining front. In this paper, we report on the determination of the source location of AE by the joint hypocenter method and multiplet analysis, and we delineate structures in the AE cloud., English
• Observational Studies of Earthquake Preparation and Generation to Mitigate Seismic Risks in Mines
  H. Ogasawara; R. Durrheim; M. Nakatani; Y. Yabe; A. Milev; A. Cichowicz; H. Kawakata; O. Murakami; M. Naoi; H. Moriya; T. Satoh; SATREPS research group, Proc. IUGG, in press, 28 Jun. 2011, [Peer-reviewed]
  English
• M~2の鉱山地震の発生が見込まれる断層を透過する弾性波のモニタリング-南アフリカEzulwini金鉱山
  川方裕則; 吉光奈奈; 中谷正生; PHILIPP Joachim; 土井一生; 直井誠; WARD Tony; MOREMA Gilbert; VISSER Vlok; KHAMBULE Sifiso; MASAKALE Thabang; MILEV Alex; DURRHEIM Ray; RIBEIRO Luiz; WARD Mike; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2011, 2011
• 南アフリカ金鉱山の断層近傍における地震波干渉法により推定したグリーン関数と透過弾性波記録の比較
  吉光奈奈; 川方裕則; 中谷正生; PHILIPP J.; 直井誠; 土井一生; WARD T.; VISSER V.; MOREMA G.; KHAMBULE S.; MASAKALE T.; MILEV A.; DURRHEIM R.J.; RIBEIRO L.; WARD M.; 小笠原宏, 日本地震学会秋季大会講演予稿集, 2011, 2011
• コーダ波スペクトル比法による極微小地震(-3
  和田直也; 川方裕則; 村上理; 小笠原宏; 土井一生; 吉光奈奈; 中谷正生; 矢部康男; 直井誠; 宮川幸治; 三宅弘恵; 井出哲; 五十嵐俊博; MOREMA G.; PINDER E., 日本地震学会秋季大会講演予稿集, 2010, 2010
• 2台の歪計から約100mで続発したMw~2の震源メカニズムと周辺領域の長期的な応力変化-南アフリカMponeng金鉱山
  桂泰史; 小笠原宏; 川方裕則; 中谷正生; 直井誠; 矢部康男; 安武剛太; 山本覚仁; 石井紘; PINDER E.; MOREMA G., 日本地震学会秋季大会講演予稿集, 2010, 2010
• Aftershock activity of a M2 earthquake in a deep South African gold mine-spatial distribution and magnitude-frequency relation-
  NAOI MAKOTO; NAKATANI MASAO; KWIATEK GRZEGORZ; PLENKERS KATRIN; YABE YASUO, 日本地震学会秋季大会講演予稿集, 2009, 27, 01 Oct. 2009
  English
• 南アフリカ金鉱山M2震源域における高周波数サンプリングでの至近距離3Dアレー観測
  和田直也; 中谷正生; 矢部康男; 直井誠; 宮川幸治; 小笠原宏; 川方裕則; 安武剛太; 吉光奈奈; 三宅弘恵; 井出哲; 五十嵐俊博; MOREMA G.; PINDER E., 日本地震学会秋季大会講演予稿集, 2009, 2009
• 歪計から20mで発生したM2の断層滑り方向延長部で続発したM~2地震に関連する歪変化-南アフリカMponeng金鉱山
  桂泰史; 小笠原宏; 安武剛太; 川方裕則; 山本覚仁; 中谷正生; 直井誠; 矢部康男; 石井紘; PINDER E.; MOREMA G., 日本地震学会秋季大会講演予稿集, 2009, 2009
• 超高周波AE(<200kHz)・微小地震観測と,弾性波透過試験による観測網評価―南アフリカ半制御地震発生実験―
  直井誠; 中谷正生; 五十嵐俊博; 新谷陽一郎; 永田広平; 桑野修; 吉田真吾; 佐野修; 山田卓司; 矢部康男; 小笠原宏; 川方裕則; 安武剛太; 山本覚仁; 飯尾能久; STANCHITS S; DRESEN G; PHILIPP J; MOREMA G; WARD T; NORTIJE T; CARSTENS R; PRETORIUS J; VAN ASWEGEN G; PINDER E; MILEV A, 日本地震学会秋季大会講演予稿集, 2007, 96, 01 Oct. 2007
  Japanese
• M2級鉱山地震群の中で観測された小さなSlow strain step(2)
  直井誠; 小笠原宏; 川方裕則; 竹内淳一; 山本覚仁; 下田直之; 森下健; 石井紘; 中尾茂; 飯尾能久; VAN ASWEGEN G; MENDECKI A. J; LENEGAN P; EBRAHIM‐TROLLOPE R, 日本地震学会秋季大会講演予稿集, 2006, 199, 01 Oct. 2006
  Japanese
• （南アフリカ金鉱山で発見された小さな遅い歪ステップ）
  直井 誠; 小笠原宏; 竹内淳一; 山本覚仁; 下田直之; 森下 健; 石井 紘; 中尾 茂・A.J. Mendecki; G. van Aswegen; R. Ebrahim-Trollope; 飯尾能久, 日本地震学会ニュースレター, vol.18 no.1,表紙, May 2006
• 南アフリカBambanani金鉱山における複数の地震群に対するb値の時間変化
  椛花剛; 小笠原宏; 川方裕則; 下田直之; 森下健; 直井誠; 山本覚仁; 飯尾能久; MENDECKI A. J.; VAN ASWEGEN G.; EBRAHIM-TROLLOPE R., 日本地震学会秋季大会講演予稿集, 2006, 2006
• 南アフリカBambanani金鉱山M2級震源極近傍での相似地震活動
  山本覚仁; 小笠原宏; 川方裕則; 下田直之; 直井誠; 飯尾能久; MENDECKI A. J.; VAN ASWEGEN G.; EBRAHIM-TROLLOPE R., 日本地震学会秋季大会講演予稿集, 2006, 2006
• 南アフリカMponeng金鉱山地下約3km,約2.5年間の歪モニタリング
  安武剛太; 小笠原宏; 川方裕則; 森下健; 直井誠; 山本覚仁; 飯尾能久; 中谷正生; 加藤愛太郎; 石井紘; 中尾茂; 山内常生; WARD A. K.; VAN ASWEGEN G.; MENDECKI A. J.; LENEGAN P.; MCGILL R.; CARSTENS R., 日本地震学会秋季大会講演予稿集, 2006, 2006
• 南アフリカ金鉱山震源極近傍での歪変化に見えるもの(4:Bambanani:震源距離数10m以内で見える震源域の挙動)
  直井誠; 小笠原宏; 竹内淳一; 下田直之; 森下健; 山本覚仁; 石井紘; 中尾茂; VAN ASWEGEN G; MENDECKI A J; LENEGAN P; EBRAHIM‐TROLLOPE R, 日本地震学会秋季大会講演予稿集, 2005, 218, 01 Oct. 2005
  Japanese
• 南アフリカ金鉱山の至近距離歪観測で見える震源変動
  小笠原宏; 竹内淳一; 下田直之; 森下健; 直井誠; 山本覚仁; 糀谷剛; 石井紘; 中尾茂; 山内常生; VAN ASWEGEN G.; MENDECKI A. J.; LENEGAN P.; DU PLESSIS F.; EBRAHIM-TROLLOPE R.; WARD A. K.; MCGILL R.; 川方裕則; 飯尾能久; 中谷正生; 加藤愛太郎; 佐藤隆司; 楠瀬勤一郎, 日本測地学会講演会要旨, 104th, 2005

• 地震学特論, 2024年, 修士課程, 理学院
• 地球惑星科学実験Ⅱ, 2024年, 学士課程, 理学部

• Advancing Earthquake Catalog Development with AI Technology and Exploring the Physics of Foreshocks
  Grants-in-Aid for Scientific Research
  01 Apr. 2025 - 31 Mar. 2029
  直井 誠; 平野 史朗; 下條 賢梧
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 25K01083
• Acoustic emission analysis to reveal the process of slow earthquakes caused by fluid Injection
  Grants-in-Aid for Scientific Research
  01 Apr. 2024 - 31 Mar. 2026
  直井 誠
  Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), Hokkaido University, 24H01027
• Understanding the physics of foreshocks based on dense seismic observation and seismicity model
  Grants-in-Aid for Scientific Research
  01 Apr. 2021 - 31 Mar. 2024
  直井 誠; 岩田 貴樹; 飯尾 能久; 平野 史朗; 中谷 正生
  本研究の目的は，独自の稠密観測データから小さな地震を徹底的に探索して超高品質の地震カタログを作成し，大地震発生前に見られる前震活動が本質的な意味での前兆かを，現実の複雑性を適切に反映した地震活動モデルで検証することである．本年度は，高効率・高精度の地震カタログを作成する手法の開発を目指し，イベント検出・走時検測・P波初動極性読み取り・震源決定などにおいて深層学習の利用を試みた．構築した手法を利用し，長野県西部・山陰・近畿地方に展開している稠密地震観測網および周辺の定常観測点のデータを統合処理して，広域にわたる多点のイベント波形データセットおよび自動震源・読み取りデータセットを構築した．また，室内水圧破砕実験で得られたAEデータに深層学習によるP波初動極性読み取りを行い，10供試体の実験，５万個ほどのAEイベントのモーメントテンソル解を評価し，結果を出版した．連続波形の中から地震による類似波形を自動検出する手法の改良も試み，波形相関法を従来より1万倍程度高速化することにも成功した．同手法により1ヶ月程度の連続波形であれば相関係数を計算可能であることを示した．
  中規模の地震活動がETASによる予想に比べ明瞭に静穏化した事例が1970年代から多く報告されている．この傾向が有意なものかを検証するため，客観的ルールを設定して成績を評価したところ，ルールのパラメタを調節すると偶然では説明しがたい良い成績が得られた．ただし，パラメタの調整において過学習が起きている可能性を考慮し，学習と成績評価に使うデータ期間を別期間にするクロスバリデーションを試みたところ，サンプル数が少なく，明瞭な結論は得られなかった．しかしながら，本手続きは一般性があり，静穏化に限らず前震等さまざまな現象の先行性評価に用いることができる．
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Kyoto University, 21H01191
• Development of hydraulic fracture evaluation by laboratory experiments and AE analysis
  Grants-in-Aid for Scientific Research
  01 Apr. 2016 - 31 Mar. 2019
  Naoi Makoto; Moriya Hirokazu; Mukuhira Yusuke
  We conducted hydraulic fracturing experiments in order to investigate the relationship between hydraulic fractures and induced microearthquakes. We monitored acoustic emissions during the experiments and compared the hypocenter distributions to fluid penetration regions that observed after the experiments. Fluid pressure history, fluid penetration region, acoustic emission activities, and their dominant mechanism significantly depended on the kind of rocks and dominant direction of preexisting fractures, revealing many important points that should be considered when estimating influence regions by microseismic activities.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Kyoto University, 16H04614
• A Study on Prediction of Rock Failure Scale and its Timing by Observation of Acoustic Emission at Africa Deep Mine
  Grants-in-Aid for Scientific Research
  01 Apr. 2014 - 31 Mar. 2018
  Moriya Hirokazu
  We observed around 300 thousand of AE (Acoustic Emission) events by a high-resolution monitoring network close to the active front of a tabular mining stope being advanced northward at 1 km depth in the Cooke 4 Gold Mine in South Africa. The application of the double-difference relative location algorithm resolved seemingly continuous, dense cloud of AEs that extend about 20 m ahead of the stope front into several discrete, steeply dipping tabular clusters a few meters thick and 10-30 m in dip extent, separated by quiet intervals a few meters thick. The tabular clusters had a strike parallel to the stope face and a dip of around 65°, resembling commonly observed large shear fractures along the plane of maximum shear. These observations suggest that discrete tabular clusters of AEs represent macroscopically localized damage structures that formed in the highly stressed intact rock ahead of the stope face and may culminate in dynamic shear events.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Tohoku University, 26249137
• Small scale in situ experiments to inject supercritical and liquid carbon dioxide into rock mass
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2017
  Ishida Tsuyoshi
  In the underground sequestration of CO2 (carbon dioxide), large amount of CO2 is injected into rock mass. Since CO2 becomes supercritical state in the deep underground and it is very slick, it is necessary to access effect of the injection on stability of surrounding rock mass. In our study, we injected CO2 into a hole drilled around 10 m long from the floor of a tunnel in a mountain with monitoring of AE (Acoustic Emission: elastic wave radiated with rock fracturing). The results indicated that the AE sources with the CO2 injection distributed larger than those with the water injection. However, with time elapsing after the CO2 injection, AE events that seemed to be caused by crack closing started to be observed. Since these AE events are most likely associated with degassing in the cracks without rock fracturing, it seems that they never bring instability to the surrounding rock mass even if they distribute large.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Kyoto University, 25249131
• Risk evaluation of mining induced earthquakes by analyzing AE activity patterns on faults in deep gold mines in South Africa
  Grants-in-Aid for Scientific Research
  29 Aug. 2014 - 31 Mar. 2016
  Naoi Makoto
  We investigated AE activities in deep gold mines in South Aftica, where many earthquakes are induced by mining. We made an AE-event catalog by using data obtained by more than 1-year observation, and found many interesting activities which have not been known in previous studies: steady AE activities on geological faults, very small repeating earthquakes, and AEs likely delineating macroscopic damage zone that newly emerged in front of the mining front.
  Japan Society for the Promotion of Science, Grant-in-Aid for Research Activity Start-up, Kyoto University, 26887022
• 超至近距離多点観測による様々な時定数を持つ断層破壊現象の統一的理解
  科学研究費助成事業
  2007 - 2009
  直井 誠
  200kHzまでの弾性波を感知できるAEセンサを用いた微小破壊観測を南アフリカ金鉱山内に展開し,観測網内で発生した100mサイズの破壊(M2地震)に伴い記録された20000個以上の余震の解析を行った.2008年度までは観測網周囲の岩盤の弾性波速度解析.観測点の座標修正・走時検測システムの構築といった予備的解析を行っていたが,2009年度は余震カタログの構築(手動検測による震源決定と,AEセンサ記録に適用可能な新たな決定手法によるモーメントマグニチュードの決定)を行い,本格的な余震活動解析や余震発生モデルの検証を行うことができた.余震分布と本震波形解析結果から,M2級破壊面の形成にも,室内実験で確認されているクーロン破壊基準が有効に働くことがはっきりと確認できた.この余震系列は,空間的に明瞭な5つのクラスタを形成していたが,各クラスタで全く異なるサイズ分布を持っていることが分かった.基本的に,余震のサイズ分布は岩盤のダメージのそれを反映していると予想されるが,5つのクラスタのうち,本震破壊面を描き出すような2次元的な分布を示した余震クラスタにおいては,その統計的性質が本震破壊の不均質構造を表すと予想し,破壊面周辺の短波長応力擾乱によってこれらの余震が発生するという最近提唱された余震モデルから予想されるものと,今回観測された余震の統計的性質が調和的であることを確認した.このことは,余震の統計的性質を調べることで,本震破壊の特性を支配すると考えられている,本震断層の不均質性を調べられる可能性を示唆する.
  日本学術振興会, 特別研究員奨励費, 東京大学, 07J09904