Details of the Researcher

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Yutaro Okada
Section
International Research Institute of Disaster Science
Job title
Assistant Professor

Research History 2

  • 2025/04 - Present
    Tohoku University　International Research Institute of Disaster Science　Assistant Professor

  • 2024/04 - 2025/03
    Tohoku University　International Research Institute of Disaster Science　JSPS postdoctoral researcher

Education 2

  • Kyoto University　Graduate School of Science　Division of Earth and Planetary Science

    2019/04 - 2024/03

  • Kochi University　Faculty of Science　Department of Applied Science

    2015/04 - 2019/03

Research Interests 5

  • Earthquakes

  • Slow Slip Events

  • Crustal Deformation

  • SAR

  • GNSS

Research Areas 2

  • Natural sciences / Solid earth science / Geodesy

  • Natural sciences / Solid earth science / Crustal Deformation

Awards 6

  1. 2025 Research Paper Award of the Seismological Society of Japan

    2025/10　Seismological Society of Japan　A review of shallow slow earthquakes along the Nankai Trough. Earth, Planets and Space, 75, 164

  2. EPS Young Researcher Award 2024

    2025/03　Earth, Planets and Space　Development of a detection method for short-term slow slip events using GNSS data and its application to the Nankai subduction zone

  3. 2023 Outstanding Student Presentation Award

    2023/05　Japan Geoscience Union　Comparison of slip distribution for four long-term slow slip events in southcentral Alaska

  4. DPRI Annual Meeting 2022 Excellent Presentation Award

    2022/02　Disaster Prevention Research Institute, Kyoto University

  5. Excellent Master Thesis Award FY2020

    2021/03　Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University　Development of the detection method for short-term slow slip events using GNSS data and its application to the Nankai subduction zone

  6. DPRI Annual Meeting 2020 Excellent Presentation Award

    2020/02　Disaster Prevention Research Institute, Kyoto University

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Papers 11

  1. Spatiotemporal Variations in the Interplate Slip Rate around Kodiak Island, Alaska

    Yutaro Okada, Takuya Nishimura, Jeffrey Todd Freymueller

    2026/02/03

    DOI： 10.22541/essoar.176087279.94521046/v2 　

  2. Recurrent earthquake swarms and transient crustal deformation off the Tokara Islands, southern Japan: Insights from the 2025 swarm sequence

    Yutaro Okada, Yusaku Ohta, Miku Ohtate, Yoshiaki Ito, Mako Ohzono, Hiroshi Yakiwara, Shigeru Nakao

    2026/01/14

    DOI： 10.21203/rs.3.rs-8399343/v1 　

  3. Machine-learning detection of slow slip events in western Shikoku, Japan, through joint analysis of seismic and geodetic data Peer-reviewed

    Kazuki Ohtake, Aitaro Kato, Yutaro Okada, Takuya Nishimura

    Earth, Planets and Space　2026/01/08

    DOI： 10.1186/s40623-025-02331-5 　

    ISSN： 1880-5981

    More details Close

    <jats:title>Abstract</jats:title> <jats:p>Over the past decade, short-term slow slip events (S-SSEs) have been detected along the entire Nankai Trough using Global Navigation Satellite System (GNSS) data. To enhance the detection of S-SSEs, we focused on the spatial and temporal coincidence of tremors and S-SSEs, a phenomenon known as episodic tremor and slip. We developed a machine learning-based method to detect S-SSEs directly from continuous seismic waveforms and applied it to seismic and geodetic data in western Shikoku, Japan. We trained a random forest regression model using statistical features extracted from continuous seismic waveforms as input variables and GNSS-derived displacement rates as target outputs. We predicted the GNSS displacement rate over a period of ~ 6 years and defined S-SSEs as periods when the predicted GNSS displacement rate increased sharply. We then estimated fault models for each detected S-SSE. The predicted displacement rates were correlated strongly with the observed displacement rates, and we identified a total of 23 S-SSEs, including 5 previously unrecognized events. The results demonstrate the effectiveness of machine learning using continuous seismic waveforms for improving S-SSE detection along the Nankai Trough.</jats:p> <jats:p> <jats:bold>Graphical Abstract</jats:bold> </jats:p>

  4. Characteristics of Observed Shallow Slow Earthquakes along the Nankai Trough Peer-reviewed

    Shunsuke TAKEMURA, Yutaro OKADA, Akemi NODA, Satoru BABA

    Zisin (Journal of the Seismological Society of Japan. 2nd ser.)　78　167-186　2025/10/08

    Publisher: Seismological Society of Japan

    DOI： 10.4294/zisin.2024-20 　

    ISSN： 0037-1114

    eISSN： 1883-9029 2186-599X

  5. Geodetic Evidence of Shallow Slow‐Slip Phenomena Beneath the Southern Ryukyu Forearc Peer-reviewed

    Chi‐Hsien Tang, Ya‐Ju Hsu, Yutaro Okada, Yusaku Ohta, Takeshi Sagiya, Pei‐Ru Jian, Yoshiaki Tamura, Takaaki Jike

    Geophysical Research Letters　2025/07/16

    DOI： 10.1029/2025GL114742 　

  6. Development of a seasonal adjustment technique STEL and its application to daily GNSS data Peer-reviewed

    Yutaro Okada, Taku Ueda

    Journal of the Geodetic Society of Japan　71　1-11　2025/07

    DOI： 10.11366/sokuchi.71.1 　

  7. Investigation on short-term slow slip events in the northeast Japan subduction zones using decadal GNSS data Peer-reviewed

    Yutaro Okada, Takuya Nishimura

    Earth, Planets and Space　2025/03/20

    DOI： 10.21203/rs.3.rs-5183966/v1 　

  8. A review of shallow slow earthquakes along the Nankai Trough Peer-reviewed

    Shunsuke Takemura, Yohei Hamada, Hanaya Okuda, Yutaro Okada, Kurama Okubo, Takeshi Akuhara, Akemi Noda, Takashi Tonegawa

    Earth, Planets and Space　2023/10/18

    DOI： 10.1186/s40623-023-01920-6 　

  9. Systematic Detection of Short‐Term Slow Slip Events in Southcentral Alaska Peer-reviewed

    Yutaro Okada, Takuya Nishimura

    Geophysical Research Letters　2023/09/16

    DOI： 10.1029/2023GL104901 　

  10. Development of a detection method for short-term slow slip events using GNSS data and its application to the Nankai subduction zone Peer-reviewed

    Yutaro Okada, Takuya Nishimura, Takao Tabei, Takeshi Matsushima, Hitoshi Hirose

    Earth, Planets and Space　74　(1)　2022/12

    Publisher: Springer Science and Business Media {LLC}

    DOI： 10.1186/s40623-022-01576-8 　

  11. Earthquake Swarm Detection Along the Hikurangi Trench, New Zealand: Insights Into the Relationship Between Seismicity and Slow Slip Events Peer-reviewed

    Tomoaki Nishikawa, Takuya Nishimura, Yutaro Okada

    Journal of Geophysical Research: Solid Earth　126　(4)　2021/04

    Publisher: American Geophysical Union ({AGU})

    DOI： 10.1029/2020JB020618 　

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Presentations 14

  1. Toward a comprehensive catalog of long-term slow slip events along the Nankai Trough using GNSS data

    Teruki Takahashi, Ryota Takagi, Ryota Hino, Yutaro Okada

    AGU 2025 Annual Meeting　2025/12/15

  2. 2025 年トカラ列島近海の群発地震に同期した過渡的な地殻変動

    岡田悠太郎, 太田雄策, 大舘未来, 伊藤嘉秋, 大園真子, 中尾茂

    日本測地学会第144回講演会　2025/10/29

  3. 深層学習による InSAR・GNSS データからの断層すべり起因の微小変位場の検出：2019 年 Mw 6.2 日向灘地震への適用

    岡田悠太郎, 福島洋

    日本測地学会第144回講演会　2025/10/29

  4. Toward a comprehensive catalog of long-term slow slip events along the Nankai Trough using GNSS data

    Teruki Takahashi, Ryota Takagi, Ryota Hino, Yutaro Okada

    Seismological Society of Japan 2026 Fall Meeting　2025/10/21

  5. Transient crustal deformation synchronous with the 2025 earthquake swarm off the Tokara Islands

    Yutaro OKADA, Yusaku Ohta, Miku Ohtate, Yoshiaki Ito, Mako Ohzono, Shigeru Nakao

    Seismological Society of Japan 2026 Fall Meeting　2025/10/21

  6. Detection of small displacements due to fault slip from InSAR and GNSS data by deep learning: Application to the 2019 Hyuga-nada earthquake

    Yutaro OKADA, Yo Fukushima

    Seismological Society of Japan 2026 Fall Meeting　2025/10/20

  7. Detection of slow slip events directly from continuous seismic waveforms along the Nankai Trough based on a random forest model

    Kazuki OHTAKE, Aitaro KATO, Yutaro OKADA, Takuya NISHIMURA

    Seismological Society of Japan 2026 Fall Meeting　2025/10/20

  8. Detection of slow slip events directly from continuous seismic waveforms based on random forest model

    Kazuki Ohtake, Aitaro Kato, Yutaro Okada, Takuya Nishimura

    International Joint Workshop on Slow-to-Fast Earthquakes 2025　2025/09/24

  9. Spatiotemporal change in the interplate slip rate around Kodiak Island, Alaska

    Yutaro Okada, Takuya Nishimura, Jeffrey T. Freymueller

    International Joint Workshop on Slow-to-Fast Earthquakes 2025　2025/09/25

  10. A long-term slow slip event beneath the southern Ryukyu forearc revealed by 25 years of GNSS observations Invited

    Chi-Hsien Tang, Ya-Ju Hsu, Yutaro Okada, Yusaku Ohta, Takeshi Sagiya, Pei-Ru Jian, Yoshiaki Tamura, Takaaki Jike

    Japan Geoscience Union Meeting 2025　2025/05/28

  11. Detection of slow slip events from continuous seismic waveforms in western Shikoku based on random forest model

    Kazuki Ohtake, Aitaro Kato, Yutaro Okada, Takuya NISHIMURA

    Japan Geoscience Union Meeting 2025　2025/05/27

  12. Preliminary analysis of common-mode errors at GNSS stations operated by SoftBank

    Yutaro Okada, Yusaku Ohta, Miku Ohtate, Yo Fukushima

    Japan Geoscience Union Meeting 2025　2025/05/26

  13. Attempt to extract three-dimensional displacement fields due to fault slip by deep learning technique using InSAR and GNSS data

    Yutaro Okada, Yo Fukushima

    Japan Geoscience Union Meeting 2025　2025/05/26

  14. Methodological development of fault slip detection from GNSS using deep learning and application to western Shikoku

    Ryo Nakagawa, Yo Fukushima, Masayuki Kano, Keisuke Yano, Yusuke Tanaka, Yutaro Okada, Kazuro Hirahara

    Japan Geoscience Union Meeting 2025　2025/05/26

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Research Projects 3

  1. Investigation on the causes of spatially correlated noise in GNSS data and development of its mitigation technique: Toward advanced analysis of small crustal deformation

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Research Activity Start-up

    Institution: Tohoku University

    2025/07/31 - 2027/03/31

  2. Comprehensive research of ongoing seismic activity in the sea near the Tokara Islands.

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Special Purposes

    Institution: Kagoshima University

    2025/08/01 - 2026/03/31

  3. スロースリップの世界的な広帯域検出：測地データによるその普遍性・地域性の考察

    岡田 悠太郎

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 京都大学

    2023/04 - 2025/03

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    2023年度は、継続期間が数日間から数週間である短期的スロースリップイベント（SSE）に主に着目して、SSE活動の地域間比較研究に取り組んだ。初めに、Okada et al. (2022)及びOkada & Nishimura (2023)で提案した系統的検出手法を改良し、西南日本、アラスカ中南部、東北日本のGNSS観測局に適用して、3地域で計440の短期的SSEを検出した。 また、アラスカ中南部では、継続期間が数か月間から数年間である長期的SSEについても、目視での検出とすべり分布推定を行った。その結果、長期的SSEが主に3つの領域で発生し、SSE発生域が1964年に発生したアラスカ地震の3つのアスペリティの深部延長に位置していること、及び長期的SSE発生期間中の短期的SSEの活動度に地域差があることが明らかになった。更に、アラスカ州コディアック島に設置されたGNSS観測局のデータに着目すると、これまでSSE期間とみなされてきた時期以外にも、プレート境界断層のすべり速度が変化している可能性が示唆された。 系統的検出により得られた短期的SSEのカタログと、本研究及び先行研究により得られた長期的SSEの分布を用いて、西南日本、アラスカ中南部、東北日本におけるSSE活動の地域間比較を行った。その結果、これら３地域では、SSEが巨大地震のすべり域の浅部もしくは深部延長に分布しており、SSE発生域は巨大地震の余効すべり域に重なるという共通点が見られた。また、3地域における短期的SSE発生数の海溝に平行な方向の違いが、海洋プレートの傾斜角や、海洋プレートと陸側プレートの組み合わせといった、沈み込み帯の環境的要素の違いと関連していることが明らかになった。 これらの研究結果について、国内学会や国際ワークショップで発表を行った。