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Yoshizawa Kazunori

Faculty of Science　Earth and Planetary Sciences　Earth and Planetary DynamicsProfessor

Researcher basic information

■ Degree
  • Ph.D., The Australian National University (Australia)
■ URL
researchmap URLホームページURL■ Various IDs
J-Global ID■ Research Keywords and Fields
Research Keyword
  • asthenosphere
  • lithosphere
  • anisotropy
  • tomography
  • surface waves
  • 地球内部構造
  • 地震学
  • Seismic Tomography
  • Earth Structure
  • seismology
  • Physics of Earth's Interior
Research Field
  • Natural Science, Solid earth sciences, seismology
■ Educational Organization

Career

■ Career
Career
  • Feb. 2023 - Present
    Hokkaido University, Faculty of Science, Professor, Japan
  • Apr. 2016 - Present
    NIED, Visiting Researcher
  • May 2007 - Jan. 2023
    Hokkaido University, Faculty of Science, Associate Professor
  • Apr. 2022 - Sep. 2022
    Hiroshima University, Graduate School of Advanced Science and Engineering, Visiting Associate Professor, Japan
  • Oct. 2018 - Oct. 2018
    Tohoku University, Graduate School of Science, Part-time Lecturer
  • Apr. 2015 - Mar. 2016
    The University of Tokyo, Earthquake Research Institute, Visiting Associate Professor
  • Aug. 2015 - Aug. 2015
    Kobe University, Graduate School of Science, Part-time Lecturer
  • Apr. 2012 - Mar. 2013
    The University of Tokyo, Earthquake Research Institute, Visiting Associate Professor
  • Jun. 2011 - Jul. 2011
    The Australian National University, Research School of Earth Sciences, Visiting Fellow
  • Feb. 2008 - Feb. 2010
    Columbia University, Lamont-Doherty Earth Observatory, Visiting Scientist
  • Apr. 2007 - Apr. 2007
    Hokkaido University, Faculty of Science, Assistant Professor
  • Apr. 2006 - Mar. 2007
    Hokkaido University, Faculty of Science, Instructor
  • Apr. 2002 - Mar. 2006
    Hokkaido University, Graduate School of Science, Instructor
  • Apr. 1998 - Dec. 1998
    JSPS Research Fellow (DC1)
Educational Background
  • 1999 - 2002, Australian National University, Research School of Earth Sciences (Ph.D. course), Australia
  • 1996 - 1998, Hiroshima University, Graduate School of Science, Department of Earth and Planetary Systems Science (Master course), Japan
  • Apr. 1993 - Mar. 1996, Hiroshima University, Faculty of Science, Department of Earth and Planetary Systems Science (Skipped)
  • Apr. 1992 - Mar. 1993, Osaka Prefecture University, Faculty of Engineering
Committee Memberships
  • Apr. 2021 - Present
    Seismological Society of Japan, IASPEI subcommittee, Society
  • Jan. 2021 - Present
    Science Council of Japan, Committee on Earth & Planetary Sciences, IUGG subcommittee, IASPEI subcommission, Government
  • Apr. 2010 - Present
    Seismological Society of Japan, Board of Representatives, Society
  • Apr. 2021 - Mar. 2023
    Seismological Society of Japan, Meetings Program Committee, Society
  • Jan. 2018 - Aug. 2022
    Earth, Planets and Space, Editor, Others
  • Apr. 2018 - Mar. 2020
    東京大学地震研究所, 共同利用委員会委員, Others
  • 2016 - 2020
    日本地球惑星科学連合, 広報普及委員会委員, Society
  • 2013 - 2020
    日本地球惑星科学連合, 地球内部科学小委員会委員, Society
  • 2014 - 2017
    日本地震学会, 表彰委員会委員, Society
  • 2005 - 2009
    日本地震学会, 代議員, Society
  • 2002 - 2008
    Seismological Society of Japan, Local Liaison Committee, Society
  • 2002 - 2003
    国際測地学・地球物理学連合 (IUGG), 将来検討ワーキンググループメンバー(IASPEI代表), Society

Research activity information

■ Awards
  • May 2007, Seismological Society of Japan, Young Investigator Award
    「表面波の波形解析と有限波長トモグラフィー法に関する理論的・実践的研究」
    Kazunori Yoshizawa, Japan society
  • Dec. 2001, American Geophysical Union, Outstanding Student Paper Award
    「Surface Wave Tomography: A Three-Stage Approach」
    International society
■ Papers
■ Other Activities and Achievements
■ Books and other publications
  • 図説地球科学の事典
    鳥海 光弘; 入船 徹男; 岩森 光; Wallis Simon; 小平 秀一; 小宮 剛; 阪口 秀; 鷺谷 威; 末次 大輔; 中川 貴司; 宮本 英昭, 7.8章 大陸マントル [吉澤和範]
    朝倉書店, 2018, 9784254160727, Japanese, [Contributor]
  • Physics of the Earth
    Honda S; Iwamori H; Utada H; Okubo S; Kurita K; Tsuchiya T; Nakai S; Hiraga T; Miyatake T; Yoshizawa K, Chap 16-17
    Asakura Publishing Co. Ltd., Jul. 2013, [Joint translation]
  • 自然科学実験
    北海道大学自然科学実験編集委, 地学第5章：地震計で測る大地の震動
    学術図書出版社, 2012, [Contributor]
■ Lectures, oral presentations, etc.
  • Eikonal tomography of North American upper mantle using multi-mode surface waves
    Kazunori Yoshizawa; Hitoshi Matsuzawa; Fan-Chi Lin
    IAGA-IASPEI Joint Scientific Assembly 2021, 25 Aug. 2021, English, Poster presentation
  • The influence of multi-scale stochastic heterogeneity on surface-wave phase speeds and apparent radial anisotropy
    Yunao Xu; Kazunori Yoshizawa; Takashi Furumura
    IAGA-IASPEI Joint Scientific Assembly 2021, 22 Aug. 2021, English, Oral presentation
  • Radially anisotropic 3-D shear wave structure of the upper mantle beneath North America by multi-mode eikonal tomography
    Hitoshi Matsuzawa; Kazunori Yoshizawa; Fan-Chi Lin
    JpGU Meeting 2021, 04 Jun. 2021, English, Oral presentation
  • Three dimensional shear wave structure in the upper mantle beneath the oldest Pacific plate
    Takehi Isse; Hitoshi Kawakatsu; Shiobara Hajime; Nozomu Takeuchi; Hiroko Sugioka; YoungHee Kim; Hisashi Utada; Sang-Mook Lee; Kazunori Yoshizawa
    AGU Fall Meeting 2020, Dec. 2020, English
  • Radially anisotropic 3-D S-wave model using multi-mode surface waves: Comparisons of linearized and nonlinear Bayesian approaches
    Kazunori Yoshizawa; Toru Taira
    AGU Fall Meeting 2020, Dec. 2020, English, Poster presentation
  • Multi-mode phase speed distribution in North America using eikonal tomography
    Hitoshi Matsuzawa; Kazunori Yoshizawa; Fan-Chi Lin
    AGU Fall Meeting 2020, Dec. 2020, English, Poster presentation
  • Multi-mode surface wave tomography with trans-dimensional hierarchical Bayesian inversion: application to Australia
    Kazunori Yoshizawa; Toru Taira
    JpGU-AGU Joint Meeting 2020, Jul. 2020, English, Poster presentation
  • Mapping azimuthal anisotropy in the Australasian upper mantle with multi-mode surface waves
    Kazunori Yoshizawa; Yuka Nishimura
    JpGU-AGU Joint Meeting 2020, Jul. 2020, English, Poster presentation
  • Multi-mode surface wave phase speed distribution in North America
    Hitoshi Matsuzawa; Kazunori Yoshizawa; Fan-Chi Lin
    JpGU-AGU Joint Meeting 2020, Jul. 2020, English, Poster presentation
  • Radially Anisotropic S-wave Structure of Australian Upper Mantle: Trans-dimensional Hierarchical Bayesian Inversions of Receiver Functions and Multi-mode Surface Waves
    Toru Taira; Kazunori Yoshizawa
    American Geophysical Union 2019 Fall Meeting, 11 Dec. 2019, English, Poster presentation
  • Phase speed mapping of multi-mode surface waves with eikonal tomography using mode-branch waveforms
    H. Matsuzawa; K. Yoshizawa; F.-C. Lin
    Fall Meeting, Seismological Society of Japan, Sep. 2019, Japanese, Poster presentation
    [Domestic Conference]
  • Azimuthal anisotropy in the upper mantle using multi-mode surface waves: Application to the Australian regio
    Y. Nishimura; K. Yoshizawa
    Fall Meeting, Seismological Society of Japan, Sep. 2019, Japanese, Oral presentation
    [Domestic Conference]
  • Effects of laminated random heterogeneity on surface wave propagation and apparent radial anisotropy
    Y. Xu; K. Yoshizawa; T. Furumura
    Fall Meeting, Seismological Society of Japan, Sep. 2019, English, Oral presentation
    [Domestic Conference]
  • Comparisons of anisotropic 3D S wave speed models derived from linearized and non-linear inversions of multi-mode surface waves
    K. Yoshizawa; T. Taira
    Seismological Society of Japan, Sep. 2019, Japanese, Poster presentation
    [Domestic Conference]
  • Multi-mode Phase Speed Measurements of Surface Waves with a Hybrid Array-based Method: Application to USArray
    H. Matsuzawa; K. Yoshizawa
    IUGG General Assembly, Jul. 2019, English, Poster presentation
    [International presentation]
  • Trans-dimensional Bayesian Inversions for Australian Lithosphere and Asthenosphere Using Multi-mode Surface Waves and Receiver Functions
    T. Toru; K. Yoshizawa
    IUGG General Assembly, Jul. 2019, English, Poster presentation
    [International presentation]
  • Radial and Azimuthal Anisotropy in the Australian Upper Mantle: Tectonic Implications for Tasman Line and Suture Zone
    Y. Nishimura; K. Yoshizawa; B.L.N. Kennett
    IUGG General Assembly, Jul. 2019, English, Poster presentation
    [International presentation]
  • Quantitative Estimation of Apparent Radial Anisotropy in the Lithosphere and Asthenosphere: Effects of Multi-scale Heterogeneity
    K. Yoshizawa; Y. Xu; T. Fukumura
    IUGG General Assembly, Jul. 2019, English, Poster presentation
    [International presentation]
  • Fine-scale random heterogeneity and apparent radial anisotropy of S-waves in the lithosphere and asthenosphere
    YOSHIZAWA Kazunori
    Seismological Society of Japan 2018 Fall Meeting, 10 Oct. 2018, Japanese, Oral presentation
    [Domestic Conference]
  • Mapping the upper mantle beneath North American continent with joint inversion of surface-wave phase and amplitude
    K. Yoshizawa; K. Hamada
    American Geophysical Union 2017 Fall Meeting, 14 Dec. 2017, English, Oral presentation
    [International presentation]
  • Seismic Tomography and Tectonics
    YOSHIZAWA Kazunori
    Summer School of Seismology, 12 Sep. 2017, Japanese, Public discourse
    [Invited], [Domestic Conference]
  • A seismological constraint on the asthenosphere: mapping radial anisotropy with multi-mode surface waves
    YOSHIZAWA Kazunori
    JpGU-AGU Joint Meeting 2017, 20 May 2017, English, Invited oral presentation
    [Invited], [International presentation]
  • Lithosphere-asthenosphere transition, mid-lithosphere discontinuity and radial anisotropy from multi-mode surface wave tomography
    YOSHIZAWA Kazunori
    American Geophysical Union 2015 Fall Meeting, Dec. 2015, English, Invited oral presentation
    [Invited], [International presentation]
  • Mapping the upper mantle with multi-mode surface waves: Lithosphere-ashtenosphere transition and radial anisotropy
    YOSHIZAWA Kazunori
    The 14th International Symposium on Study of the Earth's Deep Interior, 04 Aug. 2014, English, Invited oral presentation
    the Shonan Village Center, Kanagawa, Japan, [Invited], [International presentation]
  • The Lithosphere-Asthenosphere Transition and Radial Anisotropy Beneath Australian Continent
    YOSHIZAWA Kazunori
    Asia and Oceania Geoscieces Society 11th Annual Meeting, 30 Jul. 2014, English, Invited oral presentation
    Royton Sapporo Hotel, Japan, [Invited], [International presentation]
  • Radially anisotropic shear wave model of North America from multi- mode surface tomography using USArray
    YOSHIZAWA Kazunori
    JpGU Meeting 2010, May 2010, English, Invited oral presentation
    [Invited], [International presentation]
■ Syllabus
  • 地球惑星科学実験Ⅱ, 2024年, 学士課程, 理学部
  • 地震学, 2024年, 学士課程, 理学部
  • 現代地球惑星科学概論２, 2024年, 学士課程, 理学部
■ Affiliated academic society
  • Society of Exploration Geophysicists
  • Japan Geosciences Union
  • Seismological Society of America
  • American Geophysical Union
  • Seismological Society of Japan
■ Research Themes
  • 世界中の大規模爆発的噴火の規模をリアルタイム推定するシステムの開発
    科学研究費助成事業
    01 Apr. 2025 - 31 Mar. 2029
    高橋 浩晃; 吉澤 和範; 青山 裕; 山中 悠資
    日本学術振興会, 基盤研究(B), 北海道大学, 25K01074
  • 大陸プレート底面の高精度イメージングの研究：ベイズ推定による地震学的アプローチ
    科学研究費助成事業
    01 Apr. 2023 - 31 Mar. 2026
    吉澤 和範
    日本学術振興会, 基盤研究(C), 北海道大学, 23K03539
  • Evolution, Deformation and Dynamics of the Indo-Australian Plate: A New Seismological Approach
    Grants-in-Aid for Scientific Research
    08 Mar. 2023 - 31 Mar. 2025
    吉澤 和範; MOHANTY DEBASIS
    本研究では，インド・オーストラリアプレート下の種々の地震波解析研究を通じて，当該地域下の高精度な上部マントル構造モデルの構築と，プレートの進化・変形やダイナミクスの解明を目指している．本年度は，新しいマルチモード表面波トモグラフィーモデルの構築に必要となる，高次モードを含む表面波位相速度の解析に向けて，インド洋周辺域の地震観測点（定常観測点や臨時観測点を含む）の大量の波形データの収集とそれらの解析に向けた作業を行った．さらに，3次元トモグラフィーモデルの構築とは独立に当該地域下の地震学的構造とダイナミクスについて精査するために，インド・オーストラリアプレート系の一部であるインド・ビルマ地域（IBR）でのＳ波スプリッティング解析を行い，地殻・マントルの運動や変形と地震学的構造との関連性について検証した．その結果，IBRの地下では，地殻とマントルが分離して運動している可能性を示唆する結果が得られた．当該地域下の地殻は，プレート沈み込みに伴う圧縮応力の影響を受けている一方，マントル側はインド亜大陸リソスフェアの沈み込みに伴うアセノスフェア内の引きずりの影響を受けていると考えられる．この研究成果は現在，国際学術誌への投稿に向けて準備を進めている．また，本研究で必要となる大量の地震波形データおよび解析処理後のデータの保存のため，既存のファイルサーバーを増強するためのハードディスクや円滑な解析作業のための新しいコンピューター等を購入した．
    Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 22KF0012
  • ベイズ推定による上部マントル不連続面の高精度マッピングの研究
    科学研究費助成事業 基盤研究(C)
    01 Apr. 2020 - 31 Mar. 2023
    吉澤 和範
    本研究では，マルチモード表面波や実体波レシーバ関数等の複数の観測情報を用いて，ベイズ推定に基づく非線形インバージョン法に適用することで，上部マントル内部に存在するMLD (Mid-Lithosphere Discontinuity）やLAB (Lithosphere-Asthenosphere Boundary)，Lehmann面等の主要な不連続面の空間分布を含む，高精度なリソスフェア－アセノスフェア構造の推定法の確立を目指している．本年度はその基礎となるP波レシーバ関数とマルチモード表面波の同時インバージョンを行う手法を豪州大陸の複数観測点に適用した結果を国際学術誌に発表した．この手法により，豪州の安定大陸下に複数のMLDが観測されると共に，LABやその下のレーマン面（アセノスフェアの底に相当すると考えられる）も検出された．今後，より高密度な観測網に適用するすることで，高精度な空間マッピングへの実用化が期待される．また，ベイズ推定法による表面波トモグラフィーの研究も行い，既存の線形インバージョンモデルとの比較も行った．ベイズ推定モデルでは，データ誤差の空間変化を考慮することができ，より精度の高い3次元構造解析が可能となることが示された．さらに，S波速度モデルの高精度復元に不可欠なマルチモード表面波の新しい位相速度マッピング法（稠密アレイを用いたeikonal tomography法）の北米大陸への応用も行った．また，上部マントル内のマルチスケールのランダム不均質性が，特に中～長周期表面波の波動場や内部境界面・鉛直異方性の推定に与える影響の定量的検証も進めた．一方，内部不連続面の更なる高精度推定に向け，S波レシーバ関数の活用に向けた波形解析法の基礎研究も行い，次年度以降の応用に向けて準備を進めている．これら一連の研究成果の一部は，国内外の主要学会にて成果発表を行った．
    日本学術振興会, 基盤研究(C), 北海道大学, 20K04096
  • Study on the mechanism of continental breakup at the eastern margin of Gondwanaland by numerical simulations
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    01 Apr. 2018 - 31 Mar. 2021
    Yoshida Masaki
    We performed numerical simulations of 3D global mantle convection to investigate the mantle convection pattern and surface tectonic condition at ca. 100 Ma. We found that an extensive subduction zone developed preferentially along the eastern margin of Gondwanaland when the temperature anomaly of the lower mantle was considered at the initial state of the simulation. In addition, we performed a series of 2D numerical experiments of visco-elasto-plastic thermo-chemical convection to investigate the localization of strain in the extending continental lithosphere. We found that the time taken for seafloor subsidence and subsequent continental breakup under extensional stress is less than ca. 20 million years. During continental rifting, high-shear zones developed under the base of the deforming continental lithosphere. The present results supported one of the proposed hypotheses, where the breakup at the eastern margins of Gondwanaland occurred via trench retreat.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Japan Agency for Marine-Earth Science and Technology, Competitive research funding, 18K03811
  • High-resolution imaging of lithospohere and asthenosphere incorporating fine-scale heterogeneity
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    01 Apr. 2017 - 31 Mar. 2020
    Yoshizawa Kazunori
    The effects of fine-scale quasi-laminate heterogeneity in the upper mantle on surface wave phase speeds are investigated through numerical simulations of seismic wavefields. The results indicated that Rayleigh wave phase speeds could be reduced depending on the horizontal scale of the quasi-laminate heterogeneity and the strength of their velocity fluctuations. This indicates that the quasi-laminate heterogeneity can cause non-negligible apparent anisotropy in the lithosphere. We also developed a new method of trans-dimensional Bayesian inversion for high-resolution imaging of the upper mantle structure, incorporating multi-mode surface waves and P-wave receiver functions. The method has been applied to major permanent seismic stations in the Australian continent, and we could successfully detect multiple discontinuities in the upper mantle, including Mid-Lithosphere Discontinuities, Lithosphere-Asthenosphere Boundary and the Lehmann Discontinuity.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, Competitive research funding, 17K05623
  • Pacific Array
    Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Apr. 2015 - Mar. 2018
    Kawakatsu Hitoshi; SHIOBARA Hajime; ISSE Takehi; NISHIDA Kiwamu; UTADA Hisashi; SUETSUGU Daisuke; SUGIOKA Hiroko; YOSHIZAWA Kazunori
    We have proposed a next generation large-scale array experiment in the ocean called Pacific Array. Recent advances in ocean bottom broadband seismometry, together with advances in the seismic analysis methodology, have enabled us to resolve the regional 1-D structure of the entire lithosphere/asthenosphere system, including seismic anisotropy, with deployments of ~15 broadband ocean bottom seismometers. Having ~15 BBOBSs as an array unit for a ~1-year deployment, and repeating such deployments in a leap-frog way or concurrently (an array of arrays) for a decade or so would enable us to cover a large portion of the Pacific basin. With this JSPS support, we took a leadership to organize international collaborations; as a result, three array deployments are funded so far in various countries (US, Japan, and Korea).
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, The University of Tokyo, Coinvestigator not use grants, 15K13558
  • Geodynamics in Far East
    Grants-in-Aid for Scientific Research
    2013 - 2017
    Takahashi Hiroaki; ICHIYANAGI Masayoshi; YAMAGUCHI Teruhiro; GORDEEV Evgeny; BYKOV Victor; GERASIMENKO Mikhail; SHESTAKOV Nikolay; VASILENKO Nikolay; PRYTKOV Alexandr; LEVIN Yuri; VALENTINE Mikhaylov; KOSTYLEV Dmitrii; CHEBROV Danila; SEROVETNIKOV Sergey
    Seismic and GNSS observation had been carried out in northeastern Asia with Russian institutions. Significant regional post-seismic crustal deformation has been detected. Postseismic displacements exceeded co-seismic one in Prymorie stations. Detailed seismic tomographic image using broadband seismograms clearly detected seismic velocity structure beneath Japan Sea. Viscoelastic structure estimation using geodetic and seismic information was performed. Misfit between calculated and observed postseismic displacements might request to construct more complex structure. Our model allow to estimate regional postseismic signals due to historical past great earthquakes in Japan Islands. Estimated viscoelastic parameters had predicted great subduction earthquakes around Japan generated regional and long-term deformation in northeast Asia. This fact suggested current crustal deformation field in continent has been strongly affected by distant subduction earthquakes.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Competitive research funding, 25257204
  • High-resolution mapping of the lithosphere-asthenosphere boundary with seismic wave analysis
    Grants-in-Aid for Scientific Research
    2014 - 2016
    Yoshizawa Kazunori; Kennett Brian L. N.; HAMADA KOUTA; NARITA RYOU; MATSUZAWA HITOSHI
    Lithosphere-asthenosphere boundaries beneath continental and oceanic regions are estimated from high-resolution 3-D S wave speed models derived from simultaneous inversions of multi-mode Love and Rayleigh waves. We also investigated the effects of arbitrary selection of independent parameters for radial anisotropy of shear waves. New radial anisotropy models in Australia and Pacific regions exhibit conspicuous radial anisotropy with SH>SV in the asthenosphere, indicating the effects of strong shear at the base of the fast drifting lithosphere. We also found that the estimated depths of Mid-Lithosphere Discontinuity (MLD) in the continental lithosphere from S-wave receiver functions coincide well with the inflection point of vertical profiles of radial anisotropy, which is likely to be related to the existence of fine-scale laminated random heterogeneities in the lithosphere.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, Competitive research funding, 26400443
  • A study on the lithosphere-asthenosphere boundary using multi-mode surface waves
    Grants-in-Aid for Scientific Research
    2012 - 2013
    YOSHIZAWA Kazunori
    We developed a new method for estimating the lithosphere-asthenosphere boundary (LAB) from a 3-D shear wave model and its vertical velocity gradient, derived from multi-mode surface waves. The method is applied to a new anisotropic model of Australia, and the 3-D distribution of LAB, including its depth and thickness, has been estimated successfully. The estimated LAB beneath Australia has been discussed in detail in comparison with the radial anisotropy and earlier results from body-wave receiver functions. We have also developed a new technique for measuring inter-station phase and amplitude of surface waves based on a fully nonlinear waveform fitting. The new method has been applied to USArray, and a preliminary high-resolution phase speed models of North America was constructed. The new method allows us to collect a large number of short inter-station paths (less than 1000km), which can be of great help to enhance the horizontal resolution of shear wave models.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, Principal investigator, Competitive research funding, 24740298
  • Renewing of tectonic frame in northeastern Asia by geophysical observation data
    Grants-in-Aid for Scientific Research
    2009 - 2012
    TAKAHASHI Hiroaki
    Characteristics of crustal deformation due to Amur plate motion and seismological structure of crust and upper mantle in far eastern Russia, Japan Sea and northwestern Pacific had been clarified from original geophysical data from international GPS and seismological observation network operated by this research project. Clear coseismic and postseismic deformation associated with the 2011 M9.0 Tohoku earthquake was recognized. These facts suggested that geodynamic effects related to subdution process along Kuril, Japan trenches and Nankai trough should be examined for detection of Amur plate motion and building tectonic frame in northeastern Asia.
    Ministry of Education, Culture, Sports, Science and Technology, Grant-in-Aid for Scientific Research (A), Hokkaido University, Competitive research funding, 21253005
  • Challenges for a 3-D anelastic attenuation structure from multi-mode surface waves with nonlinear waveform analysis
    Grants-in-Aid for Scientific Research
    2010 - 2011
    YOSHIZAWA Kazunori
    For the reconstruction of high-resolution attenuation structure of the upper mantle, surface wave phase and amplitude data are collected using recent high-density seismic networks in continental regions. A preliminary surface-wave attenuation model of North America revealed the high attenuation beneath western US(incl. hotspot and rift zone), whereas low attenuation is seen beneath stable cratons and plateau, suggesting clear correlation between the velocity and attenuation structures on a large scale. Furthermore, refined shear velocity models in continental regions revealed anomalously strong radial anisotropy beneath LAB of central Australia, which is likely to be caused by the strong shear beneath the fast moving Australian plate.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, Principal investigator, Competitive research funding, 22654053
  • Investigation of fine-structure of stagnant slab using by a new broad-band seismic network in the Far Eastern Siberia
    Grants-in-Aid for Scientific Research(特定領域研究)
    2004 - 2008
    Minoru KASAHARA; Kiyoshi YOMOGIDA; Hiroki MIYAMACHI; Yuuichiro TANIOKA; Hiroaki TAKAHASHI; Kazunori YOSHIZAWA; Rak Se SEN; Vladimir BORMOTOV
    潜り込んだ太平洋プレートのスタグナント(滞留)しているロシア極東地域に、8箇所の広帯域地震観測点の新設を目標に進めてきたが、3年目に完成し、さらに1箇所追加で、カムチャッカに設置できた。観測は、ロシア科学アカデミー・地球物理局・サハリン支所の定常観測点を利用できており、それぞれの観測点での維持管理は、順調にすすみ、全地球で発生するM5.5以上の地震データと、M4.5以上の千島海溝付近の地震データは、日本側に提供されて、日本側のデータセンターに保存され、研究に供されている。これらのデータは、世界の地震コミュニティに公開する予定である。
    Ministry of Education, Culture, Sports, Science and Technology, 特定領域研究, 北海道大学, Coinvestigator not use grants, Competitive research funding, 16075201
  • 表面波の有限波長トモグラフィー法を用いた3次元上部マントル異方性構造の研究
    科学研究費補助金(若手研究(B))
    2005 - 2006
    吉澤 和範
    本研究では,研究代表者がこれまで開発を進めてきた表面波の有限波長トモグラフィー法を,異方性媒体の場合にまで拡張し,高分解能な上部マントル内部の3次元異方的不均質構造を復元することを目的としている.今年度は,高密度な広帯域地震観測網が展開されている北西太平洋地域の地震波形データに対して独自のトモグラフィー手法を適用し,この地域直下の上部マントルの方位異方性分布の復元を行った.同時に,比較的観測点密度が低く,これまでトモグラフィーモデルの分解能に限界のあった北海道北部(苫前町)に,新たな広帯域地震観測点を設置し連続観測も行った.これまで進めてきた地震波解析により,北西太平洋地域を通過するレイリー波の位相速度データを十分収集することができたので,これらを用いて,日本列島及びその周辺域を含む北西太平洋の位相速度分布及び方位異方性分布の復元を行った.この結果,周期約100秒以下の基本モードレイリー波位相速度(深さ約150km以浅のS波速度構造に相当)の方位異方性分布が,GPS観測から判明しているユーラシアプレート東縁部の運動方向と整合的であることや,北海道北西部のユーラシアプレート及び北米プレートの境界を境にして方位異方性の方向が急激に変化すること等が分かった.これらの観測事実は,ユーラシアプレート東縁部の移動方向に沿った流れ場がその直下の上部マントル内部に存在することや,二つのプレー...
    文部科学省, 若手研究(B), 北海道大学, Principal investigator, Competitive research funding, 17740283
  • 短周期マルチモード表面波の散乱・回折効果を考慮した次世代トモグラフィー法の研究
    科学研究費補助金(若手研究(B))
    2003 - 2004
    吉澤 和範
    本研究では,より詳細かつ正確な上部マントル内部の3次元不均質構造を探るために,不均質媒体を伝播する表面波の散乱・回折といった複雑な効果を考慮した新しいインバージョン法の開発と応用を主な目的としている.昨年度に引き続き,新手法の新しい理論とその数値計算手法の開発を行い,その成果は既に主要国際誌に投稿している.この方法では,波線周辺領域からの散乱波の影響も考慮するため,従来の波線理論に基づく手法に比べて膨大な計算量が必要となる.今年度は,計算効率の向上を図るために,昨年度購入した高速PCクラスタサーバーに,さらにメモリとCPUの増設を行い,より高速な大規模計算を可能とした.これを活用しオホーツク海からオーストラリア大陸までにいたる西太平洋地域の地震波形データの解析を行い,初期的な3次元不均質モデルの復元を行った.また,新しい有限波長トモグラフィー法による分解能に関するテストも行い,従来の方法に比べて分解能と信頼性の高いモデルが得られることが明らかとなった.さらに海洋研究開発機構の研究者と共同で,本研究に関連した有限波長トモグラフィー法を応用して,フィリピン海プレートの3次元S波速度構造の復元を行った.これら本研究に関連する研究成果は,AGU秋季大会(米国・サンフランシスコ)や,日本地球惑星科学関連合同大会(幕張),日本地震学会秋季大会(福岡)において発表を行った.さらに,本研究に...
    文部科学省, 若手研究(B), 北海道大学, Principal investigator, Competitive research funding, 15740266
  • 表面波偏向面異常を用いた波形インバージョンによる上部マントル3次元構造
    科学研究費助成事業 特別研究員奨励費
    1998 - 1998
    吉澤 和範
    日本学術振興会, 特別研究員奨励費, 広島大学, Principal investigator, Competitive research funding, 98J00623
■ Academic and Social Contribution Activities/Other
Industrial Property Rights
  • 2022 Fall Meeting, Seismological Society of Japan
    23 Oct. 2022 - 26 Oct. 2022
    Planning etc
    Competition etc
    Seismological Society of Japan
  • 地震学夏の学校2007世話人（代表）
    Sep. 2007
    Planning etc, Panel chair etc
    Academic society etc
  • IUGG Working Group (Geosciences: The Future) Member (IASPEI representative)
    Feb. 2002 - Jul. 2003
    Planning etc, Panel chair etc, Academic research planning
    Review
    International Union of Geodesy and Geophysics (IUGG)