Faculty Profiles - TAKENAKA Hiroshi

Synthetic nearfield seismograms at a subsurface position in a horizontally layered half-space

Okayama University Earth Science Report 27 ( 1 ) 29 - 38 2021.3

Authorship：Lead author Language：Japanese Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)

We extend the computational code of Takenaka and Sasatani (2000) for synthetic nearfield seismograms for horizontally layered elastic media, based on the reflection/transmission matrices and the discrete wavenumber summation method, to calculate seismic motion and its spatial derivatives at a subsurface position in the attenuative media. In this paper we describe the theory of this extension and show some numerical examples to verify the extended code.

DOI： 10.18926/ESR/61956

北海道南西沖地震に伴う津波 : 小樽から礼文島まで (復刻北海道南西沖地震と津波 : 2部津波(1))

後藤章夫, 高橋浩晃, 宇津木充, 小野忍, 西田泰典, 大島弘光, 笠原稔, 竹中博士, 斉田智治

月刊地球 = Chikyu monthly 42 ( 4 ) 214 - 219 2020.4

Theoretical analysis of the long-period velocity pulses observed in the 2016 Kumamoto Earthquake Sequence

垂水洸太郎, 渡邉禎貢, 小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2020 2020

CMT solutions of earthquakes around Okinawa island from strong-motion records by using a land-ocean unified 3D structure model

小松正直, 小割啓史, 渡邉禎貢, 岡元太郎, 中村武史, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2020 2020

Initial rupture process of the 2018 Hokkaido Eastern Iburi earthquake inferred from 2D/3D source imagings

藤本怜, 小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2020 2020

Analytical solution of near-field term, intermediate term, far-filed term, and quasi-static displacement due to rectangular fault in a homogeneous whole space

垂水洸太郎, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2020 2020

CMT solutions of the 2016 central Oita earthquakes using near-field strong motion records

小割啓史, 小松正直, 竹中博士, 岡元太郎, 中村武史, 吉見雅行, 林田拓己

日本地球惑星科学連合大会予稿集(Web) 2020 2020

Estimation of seismic motion at depth from records at a ground surface station without assumption of plane wave incidence

渡邉禎貢, 竹中博士, 小松正直, 大島光貴, 中村武史

日本地球惑星科学連合大会予稿集(Web) 2020 2020

Source process of the 14 April 2016 earthquake (M6.5) in Kumamoto area estimated by back-projection analysis

大島光貴, 竹中博士, 松原誠

日本地球惑星科学連合大会予稿集(Web) 2020 2020

Signal detection by amplitude distribution and Kullback-Leibler divergence

大島光貴, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2020 2020

Early rupture process of the 2019 Off Yamagata earthquake

藤本怜, 小割啓史, 小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2020 2020

Efficient New Schemes for Solving the 2D Dispersive Tsunami Equations

( 2 ) 9 - 17 2020

Computation of non-linear site response by the time-domain finite-difference method

Okayama University Earth Science Report 26 ( 1 ) 1 - 17 2019.12

Authorship：Last author Language：Japanese Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)

We have developed a time-domain staggered-grid finite-difference code for modeling non-linear response of a one-dimensionally inhomogeneous subsurface structure to a SH plane-wave incidence. It employs the velocity-stress formulation of elastodynamic equation for the linear part, and adopts a elastoplastic rheology model for the non-linear relation between the stress and strain. In this paper, we apply this code to four constitutive models from linear-elastic to nonlinear: (1) linear elastic model, (2) linear viscoelastic model, (3) elastoplastic model, and (4) viscoelastoplastic model, which simulate shallow sand and clay structures and are vibrated by a vertically incident SH plane-wave of Ricker wavelet, to compare the linear and the non-linear soil behaviors including low strains damping (viscoelastic effect) and/or hysteretic attenuation (non-linear effect). We also apply it to a local strong-motion record of the 2000 Western-Tottori earthquake (MW6.8). We then simulate characteristics of non-linear site response such as reduction of the spectral amplitude in the high frequency band and shift of the peak frequencies to lower frequencies.

DOI： 10.18926/ESR/58574

Exploration of S-wave velocity structure of Kita-Daito Island

地震波形の振幅の確率密度関数を用いたP波・S波到着時刻の読み取りのための最適な階級数の検討

大島光貴, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

平面波入射を仮定しないで,地表地震動から地中の入射波を算定する方法

竹中博士, 小松正直, 渡邉禎貢, 大島光貴, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

3次元不均質構造モデルを用いた2016年大分県由布の誘発地震の余震のCMTインバージョン

小割啓史, 小松正直, 竹中博士, 岡元太郎, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

岡山県全域の地盤構造の推定

畝岡歩, 畝岡歩, 小松正直, 藤田高壮, 竹中博士, 西村敬一, 大島光貴, 川瀬博

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

ソース・イメージング法を用いた2019年山形県沖の地震における初期段階の破壊過程の推定

藤本怜, 小割啓史, 小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

南西諸島におけるP波・S波減衰構造

小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

東北沖の陸海統合3次元構造モデルに基づく波形トモグラフィーの試み

岡元太郎, 竹中博士, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2019 2019

3次元理論地震波形計算によるグリーンランド氷床のQ値の推定

豊国源知, 竹中博士, 小松正直, 高木涼太, 金尾政紀, 坪井誠司

日本地震学会秋季大会講演予稿集(CD-ROM) 2018 2018

中小規模の島嶼部における深部地盤S波速度構造モデル(奄美諸島・吐喇列島編)

山田伸之, 竹中博士, 小松正直

日本地震工学シンポジウム論文集(CD-ROM) 15th 2018

3次元不均質構造モデルを用いた2016年大分県由布で発生した地震のCMTインバージョン

小割啓史, 小松正直, 竹中博士, 岡元太郎, 中村武史

日本地球惑星科学連合大会予稿集(Web) 2018 2018

遠地津波のための線形分散波方程式を効率的に解く新しい方法

秦真平, 竹中博士, 小松正直, 中村武史

日本地球惑星科学連合大会予稿集(Web) 2018 2018

岡山県内の震度観測網,K-NET,KiK-netの観測点におけるサイト増幅特性の抽出

畝岡歩, 小松正直, 大島光貴, 竹中博士, 西村敬一, 川瀬博

日本地球惑星科学連合大会予稿集(Web) 2018 2018

南西諸島における震源スケーリング

小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2018 2018

スペクトル・インバージョンに基づく岡山県内の強震観測点におけるサイト増幅特性

畝岡歩, 小松正直, 竹中博士, 大島光貴, 西村敬一, 川瀬博

日本地震学会秋季大会講演予稿集(CD-ROM) 2018 2018

地球の曲率を考慮した3次元構造モデルに基づく地震動・地殻変動・津波統合シミュレーション

竹中博士, 小松正直, 中村武史, 豊国源知, 岡元太郎

日本地震学会秋季大会講演予稿集(CD-ROM) 2018 2018

津波の非線形分散波方程式を効率的に解く新スキームの開発

秦真平, 竹中博士, 小松正直, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2018 2018

137 241 - 244 2017

強震動計算のための大分県域の3次元速度構造モデル

吉見雅行, 松山尚典, 鈴木晴彦, 谷田貝淳, 林田拓己, 松島信一, 竹中博士, 三宅弘恵, 竹村恵二

日本地球惑星科学連合大会予稿集(Web) 2017 2017

地震波減衰トモグラフィから見る2016年熊本地震震源域下の流体分布

竹中博士, 小松正直, 小田仁

日本第四紀学会講演要旨集 47 2017

2次元線形分散津波方程式の効率的な計算:スキーム編

竹中博士, 秦真平, 小松正直, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

陸海統合3次元構造モデルにもとづく日本海溝の浅い地震のFAMT解析

岡元太郎, 竹中博士, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

S-wavevectorレシーバ関数解析による南西諸島の地震学的構造の推定

村越匠, 竹中博士, 小松正直, 山田伸之

日本地球惑星科学連合大会予稿集(Web) 2017 2017

地震波干渉法を用いた別府湾周辺地域における深部地盤構造モデルの検証

林田拓己, 吉見雅行, 小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2017 2017

2016年熊本地震の強震記録を用いた岡山県内のサイト特性の評価

畝岡歩, 小松正直, 竹中博士, 西村敬一

日本地球惑星科学連合大会予稿集(Web) 2017 2017

アレイ解析による2016年4月16日大分誘発地震の震源の推定

土井原健太, 小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2017 2017

吐か喇(トカラ)列島中之島および宝島の深部地盤S波速度構造

山田伸之, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

2次元線形分散津波方程式の効率的な計算:計算編

秦真平, 竹中博士, 小松正直, 中村武史

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

南西諸島における連続地動記録を用いた雑微動の相互相関解析

QIU Dongchen, 小松正直, 豊国源知, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

バックプロジェクション法による2017年熊本地震の破壊過程の推定

大島光貴, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

別府湾周辺における微動の連続観測記録を用いた深部地盤構造の検証

林田拓己, 吉見雅行, 小松正直, 竹中博士

日本地震学会秋季大会講演予稿集(CD-ROM) 2017 2017

グリーンランド地殻浅部の経年的地震波速度変化

豊国源知, 竹中博士, 高木涼太, 金尾政紀, 坪井誠司, 東野陽子

日本地震学会秋季大会講演予稿集 2016 2016

陸海統合3次元構造モデルにもとづく2016年薩摩半島西方沖地震のシミュレーション

岡元太郎, 竹中博士, 中村武史

日本地震学会秋季大会講演予稿集 2016 2016

南西諸島の広帯域地震波形データを用いたS-wavevectorレシーバ関数解析

村越匠, 竹中博士, 小松正直, 山田伸之

日本地震学会秋季大会講演予稿集 2016 2016

焼きなまし法を用いた初動発震機構解の決定

小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2016 2016

南西諸島の広帯域地震波形データを用いたレシーバ関数解析

村越匠, 竹中博士, 小松正直, 山田伸之

日本地球惑星科学連合大会予稿集(Web) 2016 2016

3次元及び2次元震源イメージングから推定した2014年伊予灘稍深発地震の初期段階の破壊過程

宇佐美貴政, 小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2016 2016

2015年大分県南部地震(Mj5.7)における大分県周辺の長周期地震動シミュレーションと地下構造モデルの検討

奥仲達也, 小松正直, 竹中博士, 吉見雅行, 中村武史, 岡元太郎

日本地球惑星科学連合大会予稿集(Web) 2016 2016

2016年熊本地震震源域周辺の三次元地震波減衰構造

小松正直, 小田仁, 竹中博士

日本地震学会秋季大会講演予稿集 2016 2016

2016年熊本地震初期破壊過程のイメージング

宇佐美貴政, 小松正直, 竹中博士

日本地震学会秋季大会講演予稿集 2016 2016

沖縄本島における深部地盤のS波速度構造

山田伸之, 竹中博士, 小松正直

物理探査学会学術講演会講演論文集 135th 2016

Application of simulated annealing to focal mechanism determination

Okayama University Earth Science Report 22 ( 1 ) 9 - 23 2015.12

Language：Japanese

Simulated annealing (SA) is known as one of the efficient methods for global optimization. It allows for getting an optimal solution by jumping out of local minimum. In this paper, we apply the simulated annealing to determination of focal mechanism solution. To investigate the feasibility of the application, we determine focal mechanism solution of the 14 March 2014 Iyo-Nada intermediatedepth earthquake. The computation of SA method is then 1278 times faster than that of the grid search method.

DOI： 10.18926/ESR/54116

Proposal of new seismic phases "Le" and "Re", generated by ice sheet

37 ( 11 ) 463 - 473 2015.11

沖縄島中部から奄美群島南部におけるS波速度構造探査

山田伸之, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2015 2015

紀伊半島周辺における陸上及び海底地すべりによる波動伝播シミュレーション

中村武史, 竹中博士, 岡元太郎, 金田義行

日本地球惑星科学連合大会予稿集(Web) 2015 2015

2011年東北地方太平洋沖地震の不均質構造モデルを用いた破壊過程解析(5):相互相関係数による考察

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2015 2015

八重山・宮古諸島島嶼部における深部地盤のS波速度構造~地下構造モデルの性能評価~

山田伸之, 竹中博士

日本地震学会秋季大会講演予稿集 2015 2015

グリーンランド氷床における広帯域連続地震波形記録を用いた地震波干渉法解析

豊国源知, 竹中博士, 金尾政紀, 坪井誠司, 東野陽子

日本地震学会秋季大会講演予稿集 2015 2015

南海トラフ域における長周期地震動成分の伝播特性と震源メカニズム解析に与える影響の評価

中村武史, 岡元太郎, 竹中博士

日本地震学会秋季大会講演予稿集 2015 2015

南西諸島における三次元地震波減衰トモグラフィ

小松正直, 竹中博士

日本地震学会秋季大会講演予稿集 2015 2015

2014年3月14日伊予灘稍深発地震の初期段階の破壊過程

齋藤衛, 小松正直, 竹中博士

日本地球惑星科学連合大会予稿集(Web) 2015 2015

南海トラフにおけるやや長周期地震動の観測とシミュレーションによる再現

中村武史, 竹中博士, 岡元太郎, 大堀道広, 坪井誠司

日本地球惑星科学連合大会予稿集(Web) 2015 2015

長大距離地震波動伝播シミュレーションのための地球の曲率を考慮した計算スキーム

竹中博士, 豊国源知, 中村武史, 小松正直, 岡元太郎

日本地球惑星科学連合大会予稿集(Web) 2015 2015

大分平野における稠密小半径アレイ微動探査

吉見雅行, 林田拓己, 松島信一, 川瀬博, 竹中博士, 山田伸之, 徳丸哲義, 杉山長志

日本地震学会秋季大会講演予稿集 2015 2015

グリーンランド氷床モデルを用いた地震波伝播モデリング

豊国源知, 竹中博士, 金尾政紀, 坪井誠司, 東野陽子

日本地球惑星科学連合大会予稿集(Web) 2015 2015

Strong Motion Prediction for Large Inland Earthquakes

49 ( 11 ) 598 - 603 2014.11

地震波から推定される2011年東北地方太平洋沖地震の破壊過程:不均質構造モデルにもとづくグリーン関数を用いたインバージョン解析

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震工学シンポジウム論文集(CD-ROM) 14th 2014

沖縄先島諸島におけるP波減衰構造

小松正直, 竹中博士, 小田仁

日本地震学会秋季大会講演予稿集 2014 2014

不均質構造モデルによる地震波グリーン関数波形を用いた2011年東北地方太平洋沖地震の破壊過程(4)

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2014 2014

八重山・宮古諸島島嶼部における深部地盤S波速度構造モデル

山田伸之, 竹中博士

日本地震学会秋季大会講演予稿集 2014 2014

簡便なコーナ周波数f_cの推定法と減衰量t^*の決定

小松正直, 竹中博士, 小田仁

日本地震学会秋季大会講演予稿集 2014 2014

月と火星の全球地震波伝播シミュレーション

豊国源知, 竹中博士, 趙大鵬, 石原吉明

SENAC : 東北大学大型計算機センター広報 46 ( 3 ) 1 - 12 2013.7

基盤内S-wavevectorレシーバ関数を用いた九州下の地震学的構造の推定

上田拓哉, 竹中博士, 村越匠

物理探査学会学術講演会講演論文集 129th 2013

桜島火山におけるACROSS震源位置で励起された弾性波の伝播シミュレーション

竹中博士, 藤岡慧, 中村武史, 岡元太郎, 宮町宏樹, 八木原寛, 山岡耕春, 國友孝洋, 渡辺俊樹, 井口正人, 為栗健, 三ケ田均, 清水洋

日本火山学会講演予稿集 2013 2013

準円筒座標系2.5次元波動モデリング(3)-非弾性減衰-

豊国源知, 竹中博士, 岡元太郎, ZHAO Dapeng

日本地震学会秋季大会講演予稿集 2013 2013

奄美大島でのS波速度構造探査-島の地震動評価のために-

山田伸之, 竹中博士

日本地震学会秋季大会講演予稿集 2013 2013

3次元グリーンテンソル波形による2011年東北地方太平洋沖地震の破壊過程の推定(2):グリーンテンソル波形の違いの影響

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2013 2013

グリーンランド氷床上での地震波形観測に氷床が与える影響について

豊国源知, 金尾政紀, 東野陽子, 姫野哲人, 坪井誠司, 竹中博士

極域科学シンポジウム講演予稿集(CD-ROM) 4th 2013

S-wave velocity structure of Fukuoka area

YAMADA Nobuyuki, TAKENAKA Hiroshi

127 258 - 259 2012.11

Global modeling of seismic wave propagation considering the effect by the Antarctic ice sheet

34 ( 8 ) 471 - 475 2012.8

GPU-Accelerated Large-Scale Simulation of Seismic-Wave Propagation

Tsubame ESJ. : e-science journal 6 11 - 16 2012.7

青い地球と白い大陸の地震学-固体地球振動特性と不均質構造・ダイナミクスの解明-南極氷床の効果を考慮した全地球地震波伝播モデリング

豊国源知, 竹中博士, 金尾政紀

月刊地球 34 ( 8 ) 2012

2011年東北地方太平洋沖地震の破壊過程解析のための3次元近地グリーンテンソル波形計算

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2012 2012

南大東島における地盤震動調査-島の地震動評価のために-

山田伸之, 立川真太郎, 竹中博士

日本地震学会秋季大会講演予稿集 2012 2012

地中観測網のS-wavevectorレシーバ関数で見る九州の地殻及び最上部マントルの地震学的構造

上田拓哉, 村越匠, 竹中博士

日本地震学会秋季大会講演予稿集 2012 2012

近地地震における地震動・津波統合3次元数値シミュレーションの新スキーム

竹中博士, 中村武史, 蔵本稔大, 岡元太郎, 豊国源知

日本地震学会秋季大会講演予稿集 2012 2012

海底地震観測網で観測された地震動の3次元波動伝幡シミュレーションによる再現-構造モデルにおける海水層の導入の重要性

中村武史, 竹中博士, 岡元太郎, 金田義行

日本地震学会秋季大会講演予稿集 2012 2012

南西諸島における地震動シミュレーションのための三次元地下構造モデルの構築

藤岡慧, 竹中博士, 山田伸之, 中村武史, 岡元太郎, 村越匠, 藤原広行

日本地震学会秋季大会講演予稿集 2012 2012

深井戸観測記録と深部地盤構造モデルを用いたS-wavevectorレシーバ関数解析による関東平野下のプレート構造の推定

村越匠, 竹中博士

日本地震学会秋季大会講演予稿集 2012 2012

モーメントテンソル点震源を用いた準円筒座標系2.5次元波動モデリング

豊国源知, 竹中博士, 岡元太郎, ZHAO Dapeng, 伊藤喜宏, 長谷川昭

日本地震学会秋季大会講演予稿集 2012 2012

ACROSSを用いた桜島における能動監視

宮町宏樹, 八木原寛, 山岡耕春, 渡辺俊樹, 國友孝洋, 井口正人, 為栗健, 三ケ田均, 清水洋, 松島健, 竹中博士

日本火山学会講演予稿集 2012 2012

筑紫平野北東部における微動アレイ探査

奥平良太, 竹中博士, 山田伸之

日本地震学会秋季大会講演予稿集 2011 2011

2011年駿河湾で起こった地震における初期段階の震源過程

後藤史紀, 竹中博士, 中村武史

日本地震学会秋季大会講演予稿集 2011 2011

喜界島における微動探査-島の地震動評価のために-

山田伸之, 竹中博士, 奥平良太

日本地震学会秋季大会講演予稿集 2011 2011

S-wavevectorレシーバ関数解析による関東平野のフィリピン海スラブ・太平洋スラブの形状

村越匠, 竹中博士

日本地震学会秋季大会講演予稿集 2011 2011

2011年東北地方太平洋沖地震の破壊過程と近地全波形モデリング

岡元太郎, 竹中博士, 原辰彦, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2011 2011

時間領域差分法による地震波動としての近地地震津波の数値計算

竹中博士, 藏本稔大, 中村武史, 岡元太郎, 豊国源知

日本地震学会秋季大会講演予稿集 2011 2011

全地球地震波伝播モデリングを用いた北極における地震波形記録の解釈

豊国源知, 竹中博士, 金尾政紀

極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM) 2011 2011

アクロスによる桜島火山のマグマ移動検出に向けた能動的アプローチ

宮町宏樹, 井口正人, 山岡耕春, 渡辺俊樹, 八木原寛, 為栗健, 三ケ田均, 竹中博士, 清水洋

日本火山学会講演予稿集 2011 2011

月表面地形・表層構造を考慮した月の地震波伝播モデリング

岡元太郎, 小林直樹, 竹中博士

日本惑星科学会秋季講演会予稿集(Web) 2011 2011

Incorporation of anelastic attenuation effects in synthetic seismograms for transversely isotropic media

TAKENAKA Hiroshi, NAKAMURA Takeshi

Geophysical bulletin of Hokkaido University ( 73 ) 185 - 194 2010.3

自己重力の効果を考慮した球座標系2.5次元地震波伝播モデリング(1):カウリング近似

豊国源知, 竹中博士

日本地震学会秋季大会講演予稿集 2010 2010

GPUを用いた地震波伝播シミュレーション(3):地形・流体層と非弾性減衰効果の導入

岡元太郎, 竹中博士, 中村武史, 青木尊之

日本地震学会秋季大会講演予稿集 2010 2010

レシーバー関数解析のための深井戸観測記録の料理法

竹中博士, 村越匠

日本地震学会秋季大会講演予稿集 2010 2010

先島諸島におけるS波速度構造探査

山田伸之, 竹中博士, 奥平良太, 後藤史紀, 蔵本稔大

日本地震学会秋季大会講演予稿集 2010 2010

福岡県震度計観測点におけるサイト増幅特性の抽出

大島光貴, 竹中博士, 川瀬博

日本地震工学シンポジウム論文集(CD-ROM) 13th 2010

自己重力を考慮した全地球地震波動場の計算と極域波形データの比較

豊国源知, 竹中博士, 金尾政紀

極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM) 2010 2010

陸上地形・海底地形を考慮した3次元差分法による長周期地震動シミュレーション

竹中博士, 中村武史, 岡元太郎, 金田義行

日本地震工学シンポジウム論文集(CD-ROM) 13th 2010

GPUによる地震波伝播シミュレーション

岡元太郎, 竹中博士, 中村武史

情報処理学会シンポジウム論文集 2010 ( 5 ) 2010

GPGPUを用いた地震波伝播計算の試み

岡元太郎, 竹中博士

日本地震学会秋季大会講演予稿集 2009 2009

3次元不均質構造における平面波斜め入射問題を解く新しい方法:支配方程式と差分法による解法

竹中博士, 岡元太郎, 中村武史

日本地震学会秋季大会講演予稿集 2009 2009

地球中心も含めた精度と効率のよい全地球地震波伝播モデリング

豊国源知, 竹中博士

日本地震学会秋季大会講演予稿集 2009 2009

2009年8月11日駿河湾で発生した地震の3次元HOT-FDMによる波動伝播シミュレーション

中村武史, 竹中博士, 岡元太郎, 金田義行

日本地震学会秋季大会講演予稿集 2009 2009

海底火山活動に伴って発生する地震波動の海域伝播シミュレーションに有効な差分コードの開発

竹中博士, 中村武史, 金田義行

日本火山学会講演予稿集 2008 2008

2008年岩手・宮城内陸地震における開始5秒間の破壊過程のイメージング

竹中博士, 山本容維

日本地震学会秋季大会講演予稿集 2008 2008

2005年福岡県西方沖地震における高精度すべり時空間分布の推定とその検証

大島光貴, 竹中博士

日本地震工学会大会梗概集 6th 2008

近地P波記録のイメージングから得られた2008年岩手・宮城内陸地震における最初の5秒間の震源過程

竹中博士, 山本容維

日本地震工学会大会梗概集 6th 2008

鉛直方向不均質粘弾性媒質におけるtau-p領域の波動方程式と時間領域差分法計算

竹中博士, JAFARGANDOMI Arash

物理探査学会学術講演会講演論文集 117th 2007

近地P波記録から推定した2007年能登半島地震の第2震源・初期破壊・主破壊とアスペリティ

山本容維, 竹中博士

日本地震学会秋季大会講演予稿集 2007 2007

近地P波記録のバックプロジェクションによるアスペリティー分布の推定:リアルタイム・イメージングに向けた検討

竹中博士, 山本容維

日本地震学会秋季大会講演予稿集 2007 2007

標準地球モデルのための解析的な実効差分格子パラメータの計算

豊国源知, 竹中博士

日本地震学会秋季大会講演予稿集 2007 2007

2007年新潟県中越沖地震における初期破壊・主破壊・アスペリティー:柏崎における大震動との関係

山崎寛一, 山本容維, 竹中博士

日本地震学会秋季大会講演予稿集 2007 2007

近地P波記録から推定した新潟県中越沖地震の震源過程:最初の5秒間と強震動生成

竹中博士, 山崎寛一, 山本容維

日本地震工学会大会梗概集 5th 2007

近地P波記録から推定した能登半島地震の震源過程:最初の5秒間と強震動生成

山本容維, 竹中博士

日本地震工学会大会梗概集 5th 2007

福岡県西方沖地震における強震動記録と地盤増幅効果

栗林健太郎, 竹中博士, 川瀬博

日本建築学会学術講演梗概集B-2 構造2 2007 2007

地球深部を伝播する地震波の効率的モデリング--準球座標系アプローチ (フロンティア地震学の最前線)

豊国源知, 竹中博士

月刊地球 28 ( 9 ) 607 - 611 2006.9

準球座標系差分法(5)

豊国源知, 竹中博士, WANG Yanbin

日本地震学会秋季大会講演予稿集 2006 2006

アスペリティを考慮したStochastic finite-fault modelingによる2005年福岡県西方沖地震の強震動の再現

大島光貴, SAYED Moustafa, 竹中博士, 川瀬博

日本地震学会秋季大会講演予稿集 2006 2006

P波を用いたアスペリティーのリアルタイム・イメージング:リアルタイム強震動予測/推定へ向けて

竹中博士, 山本容維

日本地震学会秋季大会講演予稿集 2006 2006

ジャワ海溝の微細地殻構造モデルと2.5次元差分法を用いた2006年7月17日ジャワ島沖地震の震源過程解析

岡元太郎, 竹中博士

日本地震学会秋季大会講演予稿集 2006 2006

遠地地震波形記録の平面波近似による九州地方直下におけるモホ面イメージング

大財綾子, 竹中博士, 村越匠

日本地震学会秋季大会講演予稿集 2005 2005

2.5次元差分法で探る2005年宮城県沖の地震の震源過程

岡元太郎, 竹中博士

日本地震学会秋季大会講演予稿集 2005 2005

準球座標系差分法(4)

豊国源知, 竹中博士, WANG Yanbin

日本地震学会秋季大会講演予稿集 2005 2005

断層帯周辺における異方性速度構造推定のための地震波動場の計算:茂住-祐延断層における適用

中村武史, 竹中博士, 西上欽也

日本地震学会秋季大会講演予稿集 2005 2005

(3)地震動予測地図作成手法の研究及び強震動・震災被害予測システムの開発((3)地震による被害軽減に資する地震調査研究の推進, 1プロジェクト研究)

藤原広行, 青井真, 河合伸一, 功刀卓, 森川信之, 本多亮, 小林京子, 大井昌弘, 八十島裕, 先名重樹, 神野達夫, 石井透, 奥村俊彦, 早川譲, 渡辺基史, 福島美光, 竹中博士, 水谷守, 篠塚正宣, 久田嘉章, 市村強

防災科学技術研究所年報 15 "I - 20"-"I-22" 2004.9

Language：Japanese Publisher：独立行政法人防災科学技術研究所

地震調査研究推進本部地震調査委員会による地震動予測地図作成に資するため、各種地震計による観測網からのデータを最大限に活用し、ある一定期間内にある地域が強い地震動に襲われる確率を予測した確率論的地震動予測地図や、特定の断層を想定し、それが活動した場合をモデル化して震源断層周辺域の地盤の揺れの分布を予測したシナリオ地震による地震動予測地図を作成する。また、高精度の強震動予測を行い、地震のメカニズムや断層面などを推定するとともに、断層面上での詳細な破壊過程を分析する。さらに、地震災害を引き起こす強震動を予測し、震災被害予測を行う。これらの成果は、地震調査研究推進本部委員会において進めている「全国を概観した地震動予測地図」の作成(平成16年末を目途)に活用されている。

Research Report of the Crust and Upper Mantle Structure in the Okinawa Trough, off West Kyushu by Using Ocean Bottom Seismometer

Science reports, Department of Earth and Planetary Sciences, Kyushu University 21 ( 3 ) 69 - 107 2004.1

Language：Japanese

The Okinawa Trough is located in the・ back-arc region of the Ryukyu Island arc, and is considered to be an active spreading area. In fall of 1999, seismic survey using ocean bottom seismometers was conducted to obtain the detailed seismic structure in the northernmost part of the Okinawa Trough. The total crust thickness is 25 km including a sedimentary layer. The velocity of the upper crust changes from 5.7-6.0 km/s in the upper part to 6.1-6.2 km/s in the lower part. And its thickness changes from 3 km to 9 km. The lower crust of which velocity slightly changes from 6.5-6.7 km/sin the upper part to 6.8-6.9 km/sin the lower part has uniform thickness of about 15 km. The Pn velocity is determined to be 7.7-7.8 km/s. The seismic structure suggests that the northernmost part of the Okinawa Trough is in the incipient stage of a backarc rifting.

DOI： 10.15017/4493142

Other Link： http://hdl.handle.net/2324/4493142

Discontinuity of the Mozumi-Sukenobu fault low-velocity zone, central Japan, inferred from 3-D finite-difference simulation of fault zone waves excited by explosive sources

Y Mamada, Y Kuwahara, H Ito, H Takenaka

TECTONOPHYSICS 378 ( 3-4 ) 209 - 222 2004.1

Language：English Publisher：ELSEVIER SCIENCE BV

We delineate shallow structures of the Mozumi-Sukenobu fault, central Japan, using fault zone waves generated by near-surface explosions and detected by a seismometer array. Two explosive sources, S1 and S2, were placed at a distance of about 2 km from the array, and the other two, S3 and S4, were at a distance of about 4 km. Fault zone head waves and fault zone trapped waves following direct P wave arrivals were clearly identified in the seismograms recorded by a linear seismometer array deployed across the fault in a research tunnel at a depth of 300 in. Synthetic waveforms generated by a 3-D finite-difference (3-D FD) method were compared with observed fault zone waves up to 25 Hz. The best fitting model indicates a 200-m-wide low-velocity zone extending at least to shot site S1 located 2 kin east of the seismic array with a 20% decrease in the P wave velocity relative to the wall rock. The width of the low-velocity zone is consistent with the fault zone defined by direct geological observation in the research tunnel. However, the low-velocity zone should disappear just to the east of the site S1 to explain the observed fault zone waves for shot S3 and S4 located 4 km east of the seismometer array. Yet the observation and the simulation show notable trapped wave excitation even though shots S3 and S4 are outside the fault zone. These results indicate that (1) the effective waveguide for seismic waves along the fault does not exist east of source site S1 although the surface traces of the fault are observed in this region, and (2) considerable trapped waves can be excited by sources well outside the fault zone. These results highlight the along-strike variability in fault zone structure. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2003.09.008

時間・空間的に連続なすべり速度関数を用いた1997年鹿児島県北西部地震の強震動シミュレーション

藤井雄士郎, 竹中博士

日本地震学会秋季大会講演予稿集 2004 2004

レシーバ関数解析によるインドネシアの地殻構造の推定

村越匠, 竹中博士

日本地震学会秋季大会講演予稿集 2004 2004

準球座標系差分法 (2)

豊国源知, 竹中博士, WANG Y

日本地震学会秋季大会講演予稿集 2004 2004

レシーバ関数インバージョンによって推定した松代直下の地殻及び最上部マントルのS波速度構造

安藤利彦, 竹中博士, 村越匠, 高山博之, 小河原隆広, 仲底克彦

日本地震学会秋季大会講演予稿集 2003 2003

グリッドモデルを用いた運動学的震源インバージョン

竹中博士, 藤井雄士郎

日本地震学会秋季大会講演予稿集 2003 2003

人工地震探査のための準円筒座標系2.5次元波動モデリング

竹中博士, 田中宏樹, 岡元太郎, KENNETT B L N

日本地震学会秋季大会講演予稿集 2003 2003

(42) 地震素過程と地球内部構造の解明に関する総合的研究(5 共同研究,I 研究活動)

石田瑞穂, 井上公, 堀貞喜, 関口渉次, 福山英一, 笠原稔, 勝俣啓, 石井紘, 佃為成, 橋本信一, 渡辺茂, 山田功, 山岡耕春, 山内常生, 山田守, 宮島力男, 奥田隆, 根元謙次, 田中寅夫, 渡辺晃, 平原和朗, 許斐直, 澁谷拓郎, 鈴木貞臣, 竹中博士, 清水洋, 角田寿喜, 後藤和彦, 平野舟一郎, 宮町宏樹

防災科学技術研究所年報 13 150 - 150 2002.10

(6) 強震動・震災被害予測システムに関する研究(1 プロジェクト研究,I 研究活動)

藤原広行, 河合伸一, 青井真, 功刀卓, 神野達夫, 森川信之, 小林京子, 竹中博士, 久田嘉章

防災科学技術研究所年報 13 20 - 21 2002.10

Estimation of coda-wave attenuation in the vicinity of metropolitan Cairo, Egypt (共著)

MOUSTAFA Sayed S.R., TAKENAKA Hirohsi, MAMADA Yutaka

Mem. Fac. Sci., Kyushu Univ., Ser. D, Earth Planet. Sci. 31(2), 71-79 ( 2 ) 71 - 79 2002

Source process of the largest aftershock (M5.5) of the 1997 Kagoshima earthquakes, Kyushu, Japan (共著)

Mem. Fac. Sci., Kyushu Univ., Ser. D, Earth Planet. Sci. 31(2), 59-70 2002

3-D finite-difference simulation of seismic fault zone waves - Application to the fault zone structure of the Mozumi-Sukenobu fault, central Japan

Y Mamada, Y Kuwahara, H Ito, H Takenaka

EARTH PLANETS AND SPACE 54 ( 11 ) 1055 - 1058 2002

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

Fault zone waves have the potential to be a powerful tool to reveal the fine structure of a fault zone down to the seismogenic depth. Seismic fault zone waves include head waves, trapped waves and direct body waves propagating in the fault zone. 3-D numerical simulation is necessary to interpret the waveforms in the presence of low-velocity zones with relatively complex fault structure. We computed finite difference (FD) synthetic seismograms to fit the seismograms of explosions, which contain frequencies up to 25 Hz, recorded by a linear seismometer array across the Mozumi-Sukenobu fault, central Japan. We find fault zone head waves, direct P waves propagating within the low-velocity zone and wave trains following the direct P waves associated with the fault for both observed and synthetic waveforms. Thus, modelling of fault zone waves is expected to determine details of complex fault zone structure.

DOI： 10.5636/eps.54.11_1055

地震波散乱問題における積分方程式のウエーブレットを用いた解法の検討：大規模積分作用素行列の圧縮（共著）

Estimation of Coda-Wave Attenuation in the Vicinity of Metropolitan Cairo, Egypt

MOUSTAFA Sayed S.R., TAKENAKA Hirohsi, MAMADA Yutaka

Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences 31(2), 71-79 ( 2 ) 71 - 79 2002

MPIを用いた時間領域差分法による3次元地震波動場の並列計算（共著）

竹中博士

九州大学情報基盤センター広報 2 ( 1 ) 85 - 94 2002

2000年鳥取県西部地震の震源域における余震観測（共著）

九州大学大学院理学研究院研究報告（地球惑星科学） 21(2), 49-59 2002

Source Process of the Largest Aftershock (M5.5) of the 1997 Northwestern Kagoshima Earthquakes, Kyushu, Japan

FUJII Yushiro, TAKENAKA Hiroshi

Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences 31(2), 59-70 ( 2 ) 59 - 70 2002

竹中博士, 藤原広行

九州大学大学院理学研究院研究報告（地球惑星科学） 21(2), 61-68 ( 2 ) 61 - 66 2002

従来の震源インバージョンの結果から時間空間的に連続なすべり時間関数を抽出する方法

竹中博士, 藤井雄士郎, 川瀬博, 宮腰研, 岩田知孝

日本地震学会秋季大会講演予稿集 2002 2002

2000年鳥取県西部地震の断層直上アレーで観測されたS波偏向異方性

中村武史, 安藤利彦, 田中宏樹, 竹中博士, 桑原保人, 侭田豊, 今西和俊

日本地震学会秋季大会講演予稿集 2002 2002

2000年鳥取県西部地震の震源域におけるS波偏向異方性 (2)

中村武史, 竹中博士, 鈴木貞臣

日本地震学会秋季大会講演予稿集 2002 2002

A multidomain approach of the Fourier pseudospectral method using discontinuous grid for elastic wave modeling

YB Wang, H Takenaka

EARTH PLANETS AND SPACE 53 ( 3 ) 149 - 158 2001

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

Pseudospectral method is an efficient and high-accuracy numerical modeling technique that has been applied to the simulation of seismic wavefields in realistic models with complex structures such as sedimentary basin. However, if the sedimentary layers are included in the model, high velocity contrasts arise because of the very low S-wave velocities of the sediments as compared with the bedrock. The grid spacing then has to be very small, which leads to spatial oversampling in regions with higher velocities. As a result, we also have to use very small time interval for time marching, so that the computation requires much CPU time. A treatment of this problem is use of a multidomain approach that can employ different grid spacings in different regions, i.e. "discontinuous grid". In this study, we propose a scheme for the Fourier pseudospectral method using discontinuous grid, which uses an interpolation by the FFT. This scheme can reduce the computation time and the required computer memory as compared with the conventional one. The accuracy and efficiency of this approach are demonstrated in the present paper through examples of 2-D elastic wave modeling.

DOI： 10.5636/eps.53.149

Small scale heterogeneities in the focal region of the 1997 northwestern Kagoshima earthquakes, Japan(共著)

Proceedings of the 5th SEGJ International Symposium 147-151 2001

Modelling seismic wave propagation in a two-dimensional cylindrical whole-earth model using the pseudospectral method

Yanbin Wang, Hiroshi Takenaka, Takashi Furumura

Geophysical Journal International 145 ( 3 ) 689 - 708 2001

Language：English

We present a method for modelling seismic wave propagation in a whole-earth model by solving the elastodynamic equations in 2-D cylindrical coordinates (r, 0) using the Fourier pseudospectral method (PSM). In solving the 2-D cylindrical elastodynamic equations for a whole-earth model, a singularity arises at the centre (r = 0) of the earth. To avoid the singularity, we develop a scheme that uses extension of field variables in the radial direction, with which computation of the wavefield at the centre is avoided, so that the wave propagation through the centre can be calculated. The time interval used in the calculation is determined by the smallest lateral grid spacing around the centre in the model. In a cylindrical coordinate system, the smallest lateral grid spacing is generally so small that the calculation is too time-consuming to be realistically carried out even on a supercomputer. We adopt a multidomain scheme to increase the smallest lateral grid spacing and avoid the oversampling of the physical domain around the centre of the earth. A smoothing scheme in the wavenumber domain is also proposed, which enables us to use a large enough time interval to allow the calculation for the whole-earth model on a desktop workstation. The waveforms calculated by the present method are compared with those obtained by the Direct Solution Method (DSM) to demonstrate their high accuracy. This method significantly reduces the computer memory and computation time required and makes it possible to study the effects of small-wavelength heterogeneities that can be approximated as azimuthally symmetric on wave propagation in the earth. We apply the present method to study the effects of local heterogeneity in the earth by adding a low-velocity perturbation above the core-mantle boundary (CMB) to the IASP91 earth model.

DOI： 10.1046/j.1365-246X.2001.01413.x

A multidomain approach of the Fourier pseudospectral method using discontinuous grid for elastic wave modeling

YB Wang, H Takenaka

EARTH PLANETS AND SPACE 53 ( 3 ) 149 - 158 2001

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

DOI： 10.5636/eps.53.149

Installation Experiment of Broadband Seismometers in Shallow Vaults

Small scale heterogeneities in the focal region of the 1997 northwestern Kagoshima earthquakes, Japan(共著)

Proceedings of the 5th SEGJ International Symposium 147-151 2001

太平洋西縁沈み込み帯のマントル遷移層構造（共著）

大滝壽樹, 斉田智治, 末次大輔

月刊地球 23(27), 455-458 ( 7 ) 455 - 458 2001

YOSHIDA Yasuhiro, KANJO Kenji, HARADA Satoshi, FUJIWARA Kenji, OHTAKI Toshiki, TANAKA Akiko, KANESHIMA Satoshi, SUETSUGU Daisuke, KAMIYA Shin'cihiro, ISHIHARA Yasushi, TAKENAKA Hiroshi, SAITA Tomoharu, FUJII Yushiro

Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 54, 9-16 ( 1 ) 9 - 16 2001

Language：Japanese Publisher：SEISMOLOGICAL SOCIETY OF JAPAN

The needs for installing broadband seismometers in inconvenient places are increasing. A simple and easy installation method is necessary for this purpose because it is difficult to make seismic observatory consuming much time and money. However only a few researches have been done for this purpose. In this paper we try to find the best way to install seismometers in inconvenient places. To decrease background noises under simple installation, we tested several ways to install broadband seismometers in shallow vaults. We made two vaults with concrete blocks whose sizes are about 1.5m³ and install a broadband seismometer in it. One block was set on the ground, and the other was settled below the ground. We checked background noise level of vertical component for three cases of insulation stuff: sand, styrofoam, and none. The noise level of the seismometers below the ground is lower than that on the ground for all three cases. The noise level is the lowest when the seismometer is installed in the underground vault filled with sand. The order of the amplitude of noise level is in proportion to the temperature fluctuation near the seismometer. Noise levels show higher correlation with temperature than wind speed, precipitation and atmospheric pressure. These suggest that the inhibition of temperature change near seismometers is the key to decrease background noise level. Therefore the installation of seismometer in the underground vault filled with sand achieves the lowest noise level, though the level is about 10dB higher than that in deep tunnel at permanent observatory near the vault.

DOI： 10.4294/zisin1948.54.1_9

Modelling seismic wave propagation in a two-dimensional cylindrical whole-earth model using the pseudospectral method

Yanbin Wang, Hiroshi Takenaka, Takashi Furumura

Geophysical Journal International 145 ( 3 ) 689 - 708 2001

Language：English

DOI： 10.1046/j.1365-246X.2001.01413.x

レシーバ関数インバージョンによる九州の地殻構造の推定

村越匠, 竹中博士

日本地震学会秋季大会講演予稿集 2001 2001

3次元差分法による断層トラップ波のシミュレーション茂住祐延断層への適用

侭田豊, 桑原保人, 伊藤久男, 竹中博士

日本地震学会秋季大会講演予稿集 2001 2001

Tomographic low-velocity anomalies in the uppermost mantle around the northeastern edge of Okinawa trough, the backarc of Kyushu

H Sadeghi, S Suzuki, H Takenaka

GEOPHYSICAL RESEARCH LETTERS 27 ( 2 ) 277 - 280 2000.1

Language：English Publisher：AMER GEOPHYSICAL UNION

A simultaneous inversion for three-dimensional velocity structure and hypocentral parameters is used to determine the tomographic images of the backarc of Kyushu, southwestern Japan. The data used in the imaging are the first arrival times of 2736 local earthquakes recorded at 305 stations in a wide region from western Japan to eastern China. Additional data are provided by including arrival times of 357 teleseismic earthquakes. We got the high resolution of the uppermost mantle images for P waves at least in the depth range to 150 km, the latitude range of 30 degrees-34 degrees N and the longitude range of 128 degrees-132 degrees E. Results of inversion reveal a major zone of strong low velocity under west off Kyushu Island in the depth from 40 km to 100 km. This feature may result from partially melting in relation to the upwelling of hot mantle around the northeastern edge of the extending Okinawa trough.

DOI： 10.1029/1999GL008385

Tomographic low-velocity anomalies in the uppermost mantle around the northeastern edge of Okinawa trough, the backarc of Kyushu

H Sadeghi, S Suzuki, H Takenaka

GEOPHYSICAL RESEARCH LETTERS 27 ( 2 ) 277 - 280 2000.1

Language：English Publisher：AMER GEOPHYSICAL UNION

DOI： 10.1029/1999GL008385

Seismic Waves in a horizontally layered half-space with a general point source

TAKENAKA Hiroshi, SASATANI Tsutomu

Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences 31 ( 1 ) 19 - 28 2000

Seismograph orientation at K-NET obsevatories(2) : Oita Prefecture.(共著)

Zisin 53 ( 2 ) 185 - 192 2000

A hybrid PSM/FDM parallel simulation for large-scale 3-D seismic(acoustic)wavefield(共著)

53 ( 4 ) 294 - 308 2000

A scheme for estimating the location and tangential plane of a reflector

Hiroshi Takenaka

Earth, Planets and Space 52 ( 4 ) 299 - 303 2000

Language：English Publisher：Springer Berlin

Magmatic reflectors have been detected beneath some volcanic regions by analysing some reflection phases of seismograms. In this letter we consider a problem to determine the location and tangential plane of such a reflector from the ray parameter, back-azimuth and travel time of a reflection phase, and present a scheme to solve it. It is then shown that the problem is essentially a one-dimensional root-finding problem whose independent variable is only the depth of the reflection point, and thus it can be solved by a line search method such as the one-dimensional grid search. While homogeneous velocity structure models have been used in the conventional analyses, the present scheme employs a vertically inhomogeneous one and can also easily treat converted phases at the reflector.

DOI： 10.1186/BF03351639

Seismic Waves in a horizontally layered half-space with a general point source(共著)

Mem. Fac. Sci., Kyushu Univ., Ser. D, Earth Planet. Sci. 31 ( 1 ) 19 - 28 2000

Effect of vertical velocity gradient on ground motion in a sediment-filled basin due to incident SV wave

YB Wang, H Takenaka, T Furumura

EARTH PLANETS AND SPACE 52 ( 1 ) 13 - 24 2000

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

The natural sedimental deposits in basins show strong vertical heterogeneity in their material parameters. The aim of this paper is to investigate the effects of such vertical heterogeneity, especially vertical velocity gradient, inside basin on the seismic ground motion through the parametric study on the response of a two-dimensional semi-cylindrical sediment-filled basin to a vertical incidence of plane SV wave using the pseudospectral method. This numerical study has tried to find the effects caused by vertical velocity gradient through the use of synthetic seismograms, wavefield snapshots and surface amplitude distribution. Simulation results clearly demonstrate the derailed character of wave propagation phenomena in basins with vertical velocity gradient, which produces characteristic amplification pattern of the surface motion caused mainly by the generation of strong Rayleigh wave induced at the basin edge associated with large lateral velocity change across the basin edge. Amplification pattern at the surface strongly depends on both the vertical velocity gradient in the basin and the predominant frequency of the incident wave. Although similar phenomena on wave propagation and surface motion found in previous studies for homogeneous basin models have also been observed in this study, it has been found that the vertical velocity gradient enhances such phenomena. The results suggest that it is important to represent the vertical velocity profiles accurately when we construct a structural model for realistic modelling of ground motion.

DOI： 10.5636/eps.52.13

Effect of vertical velocity gradient on ground motion in a sediment-filled basin due to incident SV wave

YB Wang, H Takenaka, T Furumura

EARTH PLANETS AND SPACE 52 ( 1 ) 13 - 24 2000

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

DOI： 10.5636/eps.52.13

An imaging technique for subsurface faults using Teleseismic-Wave Records II - Improvement in the detectability of subsurface faults

T Murakoshi, H Takenaka, D Suetsugu

EARTH PLANETS AND SPACE 52 ( 1 ) 3 - 11 2000

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

We have developed an imaging algorithm for subsurface faults on the basis of the steepest descent method in our previous paper. In this paper we introduce two new techniques, the multi-event stacking and multi-master stacking, to improve detectability for subsurface faults. The multi-event stacking is a technique using data from plural earthquakes with different incident angles. The multi-master stacking is a technique using data of a single earthquake, in which the images obtained by employing different master receiver are stacked. We examined the feasibility of our approach using several trial models and synthetic data with different signal to noise ratios, different pulse durations and different incident angles in the two dimensional SH cases. In the numerical experiments, we could recover the image of the subsurface fault for all the trial models used, which indicates our method has a potential for sensing real subsurface faults.

DOI： 10.5636/eps.52.3

An imaging technique for subsurface faults using Teleseismic-Wave Records II - Improvement in the detectability of subsurface faults

T Murakoshi, H Takenaka, D Suetsugu

EARTH PLANETS AND SPACE 52 ( 1 ) 3 - 11 2000

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

DOI： 10.5636/eps.52.3

A Hybrid PSM/FDM parallel simulation for large-scale 3-D seismic (acustic) wavefield

FURUMURA Takashi, KOKETSU Kazuki, TAKENAKA Hiroshi

Geophysical exploration 53 ( 4 ) 294 - 308 2000

Numerical experiments for seismic tomography using the Singular Value Decomposition (SVD) technique(共著)

21 ( 1 ) 9 - 18 2000

特異値分解法を用いたサイスミック・トモグラフィの検討（共著）

中村めぐみ, 林田智宏, 竹中博士

九州大学大学院研究報告, 地球惑星科学 21 ( 1 ) 9 - 18 2000

Seismograph Orientation at K-NET Observatories (2): Oita Prefecture

WATANABE Atsushi, TAKENAKA Hiroshi, FUJII Yushiro, FUJIWARA Hiroyuki

Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 53 ( 2 ) 185 - 192 2000

A scheme for estimating the location and tangential plane of a reflector

H Takenaka

EARTH PLANETS AND SPACE 52 ( 4 ) 299 - 303 2000

Language：English Publishing type：Rapid communication, short report, research note, etc. (scientific journal) Publisher：TERRA SCIENTIFIC PUBL CO

DOI： 10.5636/eps.52.299

レシーバ関数法を用いたインドネシア地域下のマントル遷移層の厚さの推定

斉田智治, 末次大輔, 竹中博士, 大滝寿樹, 神定健二

日本地震学会秋季大会講演予稿集 2000 2000

地震波散乱問題における積分方程式のウエーブレットを用いた解法

竹中博士, 藤原広行

日本地震学会秋季大会講演予稿集 2000 2000

A reflection/transmission matrix formulation for seismoacoustic scattering by an irregular fluid-solid interface

T Okamoto, H Takenaka

GEOPHYSICAL JOURNAL INTERNATIONAL 139 ( 2 ) 531 - 546 1999.11

Language：English Publisher：BLACKWELL SCIENCE LTD

The seismoacoustic scattering due to an irregular fluid-solid interface (i.e. the ocean bottom) must be considered when modelling seismic wave propagation in oceanic regions. In this paper, we present an accurate method to treat this problem. The method is an extension of the reflection/transmission matrix approach that was developed to model scattering due to an irregular interface between two elastic solids. This approach uses the discrete wavenumber representation of the wavefield and the Rayleigh ansatz; the wavefield is decomposed into a set of plane waves, and: we assume that the scattered wavefield due to an incident plane wave can be expanded in terms of only the waves moving away from the interface. The plane waves at:both sides of the interface are then connected to each other based on this hypothesis and proper boundary conditions. The elements of the reflection/transmission matrices describe these connection coefficients.
As the fluid-solid interface, the direct application of the above method is difficult because the tangential displacement at the interface is not necessarily continuous. To avoid this problem, we use pressure as the variable inside,the fluid layer. The reflection/transmission matrices between the pressure wave (i.e. the acoustic wave) and the elastic waves are then developed by using the standard boundary conditions at the fluid-solid interface (i.e. normal stress continuity, zero tangential stress, and normal displacement continuity) and the Rayleigh ansatz.
To demonstrate the validity acid feasibility of our method, we compare the results of our method with those of other methods. First, we examine the reflection of plane elastic waves by a periodic sinusoidal interface for a single frequency. The interface profile is characterized by its periodicity or wavelength (D) and peak to trough height (h). The behaviour of the reflection calculated by our method shows almost complete agreement with that calculated by a boundary element method (BEM) up to a relatively steep interface whose height to wavelength ratio (h/D) is 0.5.
Second, we calculate the synthetic time domain waveforms for a plane vertically incident P wave into basin-like fluid layers. We compare the waveforms calculated by the present method with those calculated by the finite difference method (FDM). In general, the waveforms calculated by the two methods match well. A quantitative study shows that the degree of agreement indicated by the RMS residuals between the waveforms of the two methods becomes better when we use a smaller grid interval in the FDM calculation. For the models treated here, the cases of 30 grid-points per wavelength results in RMS residuals less than about 10-15 per cent. This grid interval is smaller than that usually applied (more than 5-10 grid-points per wavelength). Since, in general, the accuracy of the FDM calculation becomes better as the grid interval decreases, these results indicate the validity of the present method.

DOI： 10.1046/j.1365-246x.1999.00959.x

A reflection/transmission matrix formulation for seismoacoustic scattering by an irregular fluid-solid interface

T Okamoto, H Takenaka

GEOPHYSICAL JOURNAL INTERNATIONAL 139 ( 2 ) 531 - 546 1999.11

Language：English Publisher：BLACKWELL SCIENCE LTD

DOI： 10.1046/j.1365-246x.1999.00959.x

A two-point, three-dimensional seismic ray tracing using genetic algorithms

H Sadeghi, S Suzuki, H Takenaka

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 113 ( 1-4 ) 355 - 365 1999.6

Language：English Publisher：ELSEVIER SCIENCE BV

Ray tracing between two fixed points is a boundary value problem. An initial path connecting two points, the source and the receiver, is algorithmically perturbed until it converges to a solution giving a minimum travel-time path. In multi-pathing cases, it is quite possible for an algorithm to converge to a ray path with local minimum travel time. Furthermore, when the velocity structure has discontinuities, there is another serious problem, i.e., how to determine the correct intersection between the ray and the surface of discontinuity. In this paper, a new approach for two-point ray tracing is presented, which uses genetic algorithms (GAs) to overcome these problems. Since GAs are efficient global search techniques, the proposed method guarantees to find a global minimum travel-time path and also the correct intersections. A micro-GA implementation is adopted to further enhance computational efficiency. This approach is suitable for tracing the first arriving seismic waves through a 3-D heterogeneous medium with discontinuities. The method can also find the minimum time paths of later arrivals, such as reflected and refracted waves, by constraining the ray to hit a prescribed interface. The accuracy of the method is demonstrated on the numerical examples. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0031-9201(99)00011-4

A two-point, three-dimensional seismic ray tracing using genetic algorithms

H Sadeghi, S Suzuki, H Takenaka

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 113 ( 1-4 ) 355 - 365 1999.6

Language：English Publisher：ELSEVIER SCIENCE BV

DOI： 10.1016/S0031-9201(99)00011-4

Broadband strong-motion observation on the hard rock site at Kushikino.

Synthetic seismograms by using the pseudosepctral method(6) : An efficient differentiation operator for large scale 3D parallel computing

FURUMURA Takashi, KOKETSU Kazuki, TAKENAKA Hiroshi

100 103 - 107 1999.6

20 ( 3 ) 89 - 98 1999

鹿児島県串木野市の岩盤上における広帯域強震観測(共著)

九大理学部研究報告(地球惑星) 20 ( 3 ) 79 - 88 1999

地震トモグラフィによる九州背弧のマントル・アップウエリング構造と九州の張力場(共著)

月刊地球 ( 号外27 ) 211 - 216 1999

速度-応力型スタガード格子差分法を用いた2次元及び3次元地震波動計算コードの作成(共著)

九州大学理学部研究報告(地球惑星科学) 20 ( 3 ) 99 - 110 1999

Seismograph orientation at K-NET observatories (1) : Western Kagoshima region

TAKENAKA Hiroshi, WATANABE Atsushi, FUJIWARA Hiroyuki

Sci. Repts., Dept. Earth & Planet. Sci., Kyushu Univ. 20 ( 3 ) 89 - 98 1999

Broadband strong-motion of observation on hard rock site at Kushikino

Atsushi Watanabe, Yushiro Fujii, Hayato Futamure, Nobuki Kame, Hiroshi Takenaka, Sadaomi Skuzuki, Kenji Uehira, Takeshi Matsushima

Sci. Repts., Dept. Earth & Planet. Sci., Kyushu Univ. 20 ( 3 ) 79 - 88 1999

In 1997, two moderate earthquakes occurred in the northwestern part of Kagoshima Prefecture (Mjma 6.5 on March 26 and Mjma 6.3 on May 13), and a large number of aftershocks occurred in the southern part of the second event focal region. We started the observation of the aftershocks from April 1, 1998, at Kushikino. We used a broadband strong-motion velocity-type seismograph and an accelerograph in order to record the full waveforms of the strong ground motions. Up to April 25, 1999, we observed 74 events, and 3 events were recorded by both seismographs. In this paper, we report the detail of observational conditions and show some waveforms we obtained.

Simulating seismic wave propagation in transversely isotropic media by using pseudo-spectral method(共著)

Northwestern Seismological Journal 21 ( 2 ) 212 - 224 1999

Development of 2D and 3D codes of the velocity-stress staggered-grid finite-difference method for modeling seismic wave propagation

HAYASHIDA T.

Science Reports, Department of Earth and Planetary Sciences, Kyushu University 20 ( 3 ) 99 - 110 1999

Simulating seismic wave propagation in transversely isotropic media by using pseudo-spectral method(共著)

Northwestern Seismological Journal 21 ( 2 ) 212 - 224 1999

An efficient approach of the pseudospectral method for modelling of geometrically symmetric seismic wavefield

H Takenaka, YB Wang, T Furumura

EARTH PLANETS AND SPACE 51 ( 2 ) 73 - 79 1999

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

The pseudospectral method is a high-accuracy numerical modelling technique that requires less computer memory and computation time than the traditional techniques such as the finite-difference method. These advantages of the pseudospectral method have enabled us to practically apply this method to modelling realistic problems that have complex structure and source models. However, a major drawback of such numerical schemes for discrete grid models is that even for rather a simple structural model they require as much computational requirements (e.g. computation time and memory) as for an entirely complex structural model with the same size of the simple one. We actually need to employ idealised simple models, such as a model with geometrical symmetry, to investigate basic phenomena of seismic waves, to develop new techniques, or to choose optimal values of some computational parameters for more complex modelling. In this paper we propose an efficient approach of an economical pseudospectral method for calculation of wavefields in models symmetric with respect to a vertical plane or two orthogonal vertical planes. Using this approach, the wavefields only need to be computed in a half or quarter domain of the models, so that the computer memory and computation time can be reduced ideally by half or quarter, respectively, as compared with the calculation of the entire models.

DOI： 10.5636/eps.51.73

An efficient approach of the pseudospectral method for modelling of geometrically symmetric seismic wavefield

H Takenaka, YB Wang, T Furumura

EARTH PLANETS AND SPACE 51 ( 2 ) 73 - 79 1999

Language：English Publisher：TERRA SCIENTIFIC PUBL CO

DOI： 10.5636/eps.51.73

1995年兵庫県南部地震余震の地震核 (総特集地震発生に伴う物理現象--地震発生の場と物理過程(2))

マルチバンドパスフィルターを用いたS波最大振幅解析による地震波放射特性の周波数依存に関する考察

侭田豊, 二牟礼勇人, 竹中博士

日本地震学会秋季大会講演予稿集 1999 1999

PSM/FDMハイブリッド型並列計算による地震波動の3次元数値シミュレーション

古村孝志, こうけつ一起, 竹中博士

日本地震学会秋季大会講演予稿集 1999 1999

スタガード格子差分法を用いた3次元弾性波動モデリングにおける新しい自由表面条件の適用

林田智宏, 竹中博士, 岡元太郎

日本地震学会秋季大会講演予稿集 1999 1999

Calculation of Seismic Wave Propagation in a Transversely Isotropic Cylindrical Earth Model by the Pseudospectral Method

WANG Yanbin, TAKENAKA Hiroshi, FURUMURA Takashi

1998 ( 2 ) 1998.10

奥村貴史, 鈴木貞臣, 竹中博士

月刊地球 20 ( 10 ) 648 - 653 1998.10

Parallel 3-D pseudospectral simulation of seismic wave propagation

T Furumura, BLN Kennett, H Takenaka

GEOPHYSICS 63 ( 1 ) 279 - 288 1998.1

Language：English Publisher：SOC EXPLORATION GEOPHYSICISTS

Three-dimensional pseudospectral modeling for a realistic scale problem is still computationally very intensive, even when using current powerful computers. To overcome this, we have developed a parallel pseudospectral code for calculating the 3-D wavefield by concurrent use of a number of processors. The parallel algorithm is based on a partition of the computational domain, where the field quantities are distributed over a number of processors and the calculation is concurrently done in each subdomain with interprocessor communications. Experimental performance tests using three different styles of parallel computers achieved a fairly good speed up compared with conventional computation on a single processor: maximum speed-up rate of 26 using 32 processors of a Thinking Machine CM-5 parallel computer, 1.6 using a Digital Equipment DEC-Alpha two-CPU workstation, and 4.6 using a cluster of eight Sun Microsystems SPARC-Station 10 (SPARC-10) workstations connected by an Ethernet. The result of this test agrees well with the performance theoretically predicted for each system. To demonstrate the feasibility of our parallel algorithm, we show three examples: 3-D acoustic and elastic modeling of fault-zone trapped waves and the calculation of elastic wave propagation in a 3-D syncline model.

DOI： 10.1190/1.1444322

Parallel 3-D pseudospectral simulation of seismic wave propagation

T Furumura, BLN Kennett, H Takenaka

GEOPHYSICS 63 ( 1 ) 279 - 288 1998.1

Language：English Publisher：SOC EXPLORATION GEOPHYSICISTS

DOI： 10.1190/1.1444322

Observation and waveform modeling of the aftershocks of the 1997 Northwestern Kagoshima earthquake

Sensing of faults by waveform data of intermediate-depth earthquakes(共著)

Proceedings of the 4th SEGJ International Symposium 199 - 204 1998

Pseudo-spectral modeling of seismic waves in transversely isotropic media with an arbitrary direction of symmetrical axis(共著)

Proceedings of the 4th SEGJ International Symposium 117 - 122 1998

Recent developments in numerical methods for ground motion simulation(共著)

The Effect of Surface Geology on Seismic Motion, Irikura, Kudo, Okada & Sasani(eds. ), Balkema, Rotterdam(ISBN : 90 5809 030 2) 1 91 - 101 1998

Sensing of faults by waveform data of intermediate-depth earthquakes(共著)

Proceedings of the 4th SEGJ International Symposium 199 - 204 1998

鹿児島県北西部地域の地震波減衰特性〜Qc^-1の測定-(共著)

自然災害西部地区部会報・論文集 ( 22 ) 139 - 143 1998

Pseudo-spectral modeling of seismic waves in transversely isotropic media with an arbitrary direction of symmetrical axis(共著)

Proceedings of the 4th SEGJ International Symposium 117 - 122 1998

Programming for time-frequency analysis of transient seismic signals by multiple filter technique and running spectrum technique and its application (共著)

WANG Yanbin, TAKENAKA Hiroshi

Mem. Fac. Sci. , Kyushu Univ. , Ser. D, Earth Planet. Sci. 30 ( 1 ) 45 - 57 1998

1995年兵庫県南部地震の余震の地震核(共著)

月刊地球 ( 232 ) 648 - 653 1998

Programming for Time-frequency Analysis of Transient Seismic Signals by Multiple Filter Techniqeu and Running Spectrum Technique and Its Application

WANG Yanbin, TAKENAKA Hiroshi

Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences 30 ( 1 ) 45 - 57 1998

1997年鹿児島県北西部地震余震の広帯域強震観測 (共著)

九大理学部研究報告(地球惑星) 20 ( 1 ) 25 - 46 1998

Recent developments in numerical methods for ground motion simulation(共著)

The Effect of Surface Geology on Seismic Motion, Irikura, Kudo, Okada & Sasani(eds. ), Balkema, Rotterdam(ISBN : 90 5809 030 2) 1 91 - 101 1998

第16章(シミュレーション)3.1 弾性波探査

物理探査学会編「物理探査ハンドブック」 851 - 862 1998

Measurement of stress drop for the aftershocks of the 1997 Northwestern Kagoshima earthquakes.

二牟礼勇人, 竹中博士, 藤井雄士郎, 松島健, 馬越孝道, 侭田豊, 鈴木貞臣

地球惑星科学関連学会合同大会予稿集 1998 1998

Observation and waveform modeling of the aftershocks of the 1997 Northwestern Kagoshima earthquake. (2).

藤井雄士郎, 竹中博士, 松島健, 馬越孝道, 二牟礼勇人, 鈴木貞臣

地球惑星科学関連学会合同大会予稿集 1998 1998

Source process of the largest aftershock of the 1997 Northwestern Kagoshima earthquakes.

藤井雄士郎, 竹中博士, 松島健, 馬越孝道, 鈴木貞臣

日本地震学会秋季大会講演予稿集 1998 1998

The velocity-structure analysis of upper mantle using he receiver function.

斉田智治, 末次大輔, 竹中博士

地球惑星科学関連学会合同大会予稿集 1998 1998

Decay rate of coda waves and attenuation of S waves around northwestern region of Kagoshima prefecture.

侭田豊, 竹中博士, 藤井雄士郎, 松島健, 馬越孝道, 二牟礼勇人

地球惑星科学関連学会合同大会予稿集 1998 1998

South Pacific Broadband Seismic Network. SPANET.

末次大輔, 神定健二, 吉田康宏, 井上公, 関口渉次, 竹中博士, 斉田智治, 藤井雄士郎

日本地震学会秋季大会講演予稿集 1998 1998

A recursive algorithm on the new basis for elastic waves in horizontally layered media. (II).

斉田智治, 竹中博士

地球惑星科学関連学会合同大会予稿集 1998 1998

Shear-wave anisotropy in the aftershock waveforms of the 1997 Northwestern Kagoshima earthquake. (1).

藤井雄士郎, 竹中博士, 松島健, 馬越孝道

地球惑星科学関連学会合同大会予稿集 1998 1998

FUJII Y, FUTAMURE H, TAKENAKA H, MATSUSHIMA T, UMAKOSHI K, TASHIRO K, SUZUKI S

日本地震学会講演予稿集 = Programme and abstracts, the Seismological Society of Japan 1997 ( 2 ) 145 1997.9

Teleseismic waveform synthesis for ocean-bottom stations using a new, very effective 2.5-D finite difference technique(共著)

Proceedings of International Workshop on Scientific Use of Submarine Cables(Feb. 25-28,1997, Okinawa Japan) 23 - 26 1997

Comparison of Q(C)(-1) estimates from coda envelopes constructed from one- and multi-component seismograms

Y Mamada, H Takenaka

JOURNAL OF PHYSICS OF THE EARTH 45 ( 6 ) 455 - 466 1997

Coda Q(-1) in Awaji Island estimated from the aftershock records of the 1995 Hyogo-ken Nanbu earthquake

Y Mamada, T Okumura, H Takenaka, S Suzuki, S Saito, M Furumura, T Sasatani, T Matsushima, T Furumura

JOURNAL OF PHYSICS OF THE EARTH 45 ( 2 ) 147 - 154 1997

Waveform analysis of the felt-earthquakes associated with the endogenous growth of the lava dome at Unzen Volcano

OKAMATSU N.

Unzen International workshop: decade volcano and scientific drilling, Proceedings 37 - 39 1997

Comparison of Q(C)(-1) estimates from coda envelopes constructed from one- and multi-component seismograms

Y Mamada, H Takenaka

JOURNAL OF PHYSICS OF THE EARTH 45 ( 6 ) 455 - 466 1997

Modelling of Strong Motion at Kikai Island due to Aftershocks of the 1995 Amami-Oshima-Kikai Earthquakes

TAKENAKA Hiroshi, FUJII Yushiro, OKUMURA Takashi, SUZUKI Sadaomi

Journal of Geography (Chigaku Zasshi) 106 ( 4 ) 525 - 536 1997

Language：Japanese Publisher：Tokyo Geographical Society

Twin earthquakes (the Amami-Oshima-Kinkai Earthquakes) occurred at the southeast from Kikai Island on October 18 (M_JMA 6.6) and 19 (M_JMA 6.5), 1995. We observed the aftershocks at Kikai Island from October 21, 1995 to February 18, 1996 using the broadband strong-motion seismometer (VSE11C/12C). After all, we observed 40 events that include the second largest aftershock, the event of November 1 (M_JMA 5.6). In this paper we model the strong-motion records of six events among the observed aftershocks, which have large amplitudes and rather simple waveforms to estimate their focal parameters (focal depth, strike, dip, rake, seismic moment and rise time), by try and error. The results suggest the following : (1) The strikes of the mainshocks of October 18 (the first mainshock) and 19 (the second mainshock) might be about N230°E and N185°E, respectively; (2) The hypocenter of the first mainshock might locate near the north edge of the fault which was ruptured from north to south along the fault strike, while the hypocenter of the second one might locate near the south edge of the fault which was ruptured from south to north.

DOI： 10.5026/jgeography.106.4_525

Waveform analysis of the felt earthquakes associated with the endogenous growth of the lava dome at Unzen volcano (共著)

Proceedings of Unzen International Workshop : Decade Volcano and Scientific Drilling 37 - 39 1997

Coda Q(-1) in Awaji Island estimated from the aftershock records of the 1995 Hyogo-ken Nanbu earthquake

Y Mamada, T Okumura, H Takenaka, S Suzuki, S Saito, M Furumura, T Sasatani, T Matsushima, T Furumura

JOURNAL OF PHYSICS OF THE EARTH 45 ( 2 ) 147 - 154 1997

Teleseismic waveform synthesis for ocean-bottom stations using a new, very effective 2.5-D finite difference technique(共著)

Proceedings of International Workshop on Scientific Use of Submarine Cables(Feb. 25-28,1997, Okinawa Japan) 23 - 26 1997

Sensing of faults by teleseismic waveform data. III. Improvement in the detectability of subsurface faults.

村越匠, 竹中博士, 末次大輔

地球惑星科学関連学会合同大会予稿集 1997 1997

A time-domain FDM for 2.5-D elastic plane-wave incidence problems.

竹中博士, 岡元太郎, KENNETT B L N

地球惑星科学関連学会合同大会予稿集 1997 1997

A ”simple” estimation method for VP/VS of a sedimentary layer by amplitudes of S and SP phases.

竹中博士, 斉田智治, 藤井雄士郎

地球惑星科学関連学会合同大会予稿集 1997 1997

A new 2.5D method for far-field body waves. Application to the 1992 Nicaraguan tsunami earthquake.

岡元太郎, 竹中博士

日本地震学会秋季大会講演予稿集 1997 1997

A very effective 2.5-D method for teleseismic body-wave synthesis.

竹中博士, 岡元太郎, KENNETT B L N

日本地震学会秋季大会講演予稿集 1997 1997

Simultaneous Observation using Broadband Seismometers. (II).

吉田康宏, 神定健二, 金嶋聡, 大滝寿樹, 田中明子, 末次大輔, 神谷真一郎, 石原靖, 竹中博士

日本地震学会秋季大会講演予稿集 1997 1997

Comparison Qc estimated from S coda envelope of vector amplitude with that of 1 component amplitude.

侭田豊, 竹中博士

地球惑星科学関連学会合同大会予稿集 1997 1997

A 2.5-D time-domain elastodynamic equation for a general anisotropic medium

H Takenaka, BLN Kennett

GEOPHYSICAL JOURNAL INTERNATIONAL 127 ( 2 ) F1 - F4 1996.11

Language：English Publisher：OXFORD UNIV PRESS

In order to provide a quantitative analysis of real seismic records from complex regions we need to be able to calculate the wavefields in three dimensions. However, full 3-D modelling of seismic-wave propagation is still computationally intensive. An economical approach to the modelling of seismic-wave propagation which includes many important aspects of the propagation process is to examine the 3-D response of a model where the material parameters vary in two dimensions. Such a configuration, in which a 3-D wavefield is calculated for a 2-D medium, is called the '2.5-D problem'. Recently, Takenaka & Kennett (1996) proposed a 2.5-D time-domain elastodynamic equation for seismic wavefields in models with a 2-D variation in structure but obliquely incident plane waves in the absence of source. This approach is useful even for non-plane waves. In the presence of source a new 2.5-D elastodynamic equation for general anisotropic media can be derived in the time domain based on the Radon transform over slowness in the direction with constant medium properties. The approach can also be formulated in terms of velocity-stress, a representation which is well suited to the use of numerical techniques for 2-D time-domain problems such as velocity-stress finite-difference or velocity-stress pseudospectral techniques.

DOI： 10.1111/j.1365-246X.1996.tb04716.x

A 2.5-D time-domain elastodynamic equation for a general anisotropic medium

H Takenaka, BLN Kennett

GEOPHYSICAL JOURNAL INTERNATIONAL 127 ( 2 ) F1 - F4 1996.11

Language：English Publisher：OXFORD UNIV PRESS

DOI： 10.1111/j.1365-246X.1996.tb04716.x

Elastic finite-difference modeling of strong motion in Ashigara Valley for the 1990 Odawara, Japan, earthquake

A Pitarka, D Suetsugu, H Takenaka

BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 86 ( 4 ) 981 - 990 1996.8

Language：English Publisher：SEISMOLOGICAL SOC AMER

Finite-difference seismograms are calculated for the 1990 Odawara earthquake to model transverse and radial components of strong-motion data. Using a basin structure derived from a geotechnical survey and double-couple solution determined from P first-motion data and SH/SV amplitude ratio, two-dimensional SH and P/SV finite-difference calculation, along with correction for soft surface layers, reproduces the observed spatial variation in amplitude and waveform of the transverse and radial records at the Ashigara Valley blind prediction sites for frequencies up to 2 Hz. Comparison of the synthetic and the observed seismograms suggests that the observed spatial variation in the SH amplitude is attributed to the source radiation and amplification due to the soft surface layers, while the SV amplitude variation is controlled by the amplification due to the sedimentary basin as well as the source and surface-layer effects.

A 2.5-D time-domain elastodynamic equation for plane-wave incidence

H Takenaka, BLN Kennett

GEOPHYSICAL JOURNAL INTERNATIONAL 125 ( 2 ) F5 - F9 1996.5

Language：English Publisher：OXFORD UNIV PRESS

Full 3-D modelling of seismic wave propagation is still computationally intensive. Recently, as a compromise between realism and computational efficiency, two-and-a-half-dimensional (2.5-D) methods for calculating 3-D elastic wavefields in media varying in two dimensions have been developed. Such 2.5-D methods are an economical approach for calculating 3-D wavefields, and require a storage capacity only slightly larger than those of the corresponding 2-D calculations.
In this paper, a 2.5-D elastodynamic equation in the time domain is constructed for seismic wavefields in models with a 2-D variation in structure but obliquely incident plane waves. The approach does not require wavenumber summation, and as a result requires much less computation time than in previous techniques. The modelling of such seismic wavefields for a 2.5-D situation with an incident plane wave is of considerable practical importance: for example, this approach can be applied to the modelling of the local response of an irregular basin structure, or to teleseismic body waveforms from shallow earthquakes occurring in subduction zones, where the laterally heterogeneous medium can have a large effect on the waveform.
All the variables in the 2.5-D time-domain elastodynamic equation are real-valued, so the propagation characteristics can be efficiently calculated using 2-D time-domain numerical techniques such as the finite-difference method or the pseudospectral method with less computation time and memory than for other implementations.

DOI： 10.1111/j.1365-246X.1996.tb00001.x

A 2.5-D time-domain elastodynamic equation for plane-wave incidence

H Takenaka, BLN Kennett

GEOPHYSICAL JOURNAL INTERNATIONAL 125 ( 2 ) F5 - F9 1996.5

Language：English Publisher：OXFORD UNIV PRESS

DOI： 10.1111/j.1365-246X.1996.tb00001.x

An efficient approach to the seismogram synthesis for a basin structure using propagation invariants

H Takenaka, M Ohori, K Koketsu, BLN Kennett

BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 86 ( 2 ) 379 - 388 1996.4

Language：English Publisher：SEISMOLOGICAL SOC AMER

The Aki-Larner method is one of the cheapest methods for synthetic seismograms in irregularly layered media. In this article, we propose a new approach for a two-dimensional SH problem, solved originally by Aki and Larner (1970). This new approach is not only based on the Rayleigh ansatz used in the original Aki-Larner method but also uses further information on wave fields, i.e., the propagation invariants. We reduce two coupled integral equations formulated in the original Aki-Larner method to a single integral equation. Applying the trapezoidal rule for numerical integration and collocation matching, this integral equation is discretized to yield a set of simultaneous linear equations. Throughout the derivation of these linear equations, we do not assume the periodicity of the interface, unlike the original Aki-Larner method. But the final solution in the space domain implicitly includes it due to use of the same discretization of the horizontal wavenumber as the discrete wavenumber technique for the inverse Fourier transform from the wavenumber domain to the space domain.
The scheme presented in this article is more efficient than the original Aki-Larner method. The computation time and memory required for our scheme are nearly half and one-fourth of those for the original Aki-Larner method. We demonstrate that the band-reduction technique, approximation by considering only coupling between nearby wavenumbers, can accelerate the efficiency of our scheme, although it may degrade the accuracy.

An efficient approach to the seismogram synthesis for a basin structure using propagation invariants

H Takenaka, M Ohori, K Koketsu, BLN Kennett

BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 86 ( 2 ) 379 - 388 1996.4

Language：English Publisher：SEISMOLOGICAL SOC AMER

Effect of 2-D topography on the 3-D seismic wavefield using a 2.5-D discrete wavenumber-boundary integral equation method

H Takenaka, BLN Kennett, H Fujiwara

GEOPHYSICAL JOURNAL INTERNATIONAL 124 ( 3 ) 741 - 755 1996.3

Language：English Publisher：BLACKWELL SCIENCE LTD

A full treatment of topographic effects on the seismic wavefield requires a 3-D treatment of the topography and a 3-D calculation for the wavefield. However, such full 3-D calculations are still very expensive to perform. An economical approach, which does not require the same level of computational resources as full 3-D modelling, is to examine the 3-D response of a model in which the heterogeneity pattern is 2-D (the so-called 2.5-D problem). Such 2.5-D methods can calculate 3-D wavefields without huge computer memory requirements, since they require storage nearly equal to that of the corresponding 2-D calculations.
In this paper, we consider wave propagation from a point source in the presence of 2-D irregular topography, and develop a computational method for such 2.5-D wave-propagation problems. This approach is an extension to the 2.5-D case of the discrete wavenumber-boundary integral equation method introduced by Bouchon (1985) and Gaffet & Bouchon (1989) to study 2-D topographic problems. One of the most significant advantages of the 2.5-D calculations is that calculations are performed for a point source and so it is possible for us to take into account the 3-D radiation pattern from the source. We demonstrate that this discrete wavenumber-boundary integral equation procedure, coupled with a Green's function decomposition into P-and S-wave contributions, provides a flexible and effective means of evaluating the wavefield.

DOI： 10.1111/j.1365-246X.1996.tb05635.x

2.5-D modelling of elastic waves using the pseudospectral method

T Furumura, H Takenaka

GEOPHYSICAL JOURNAL INTERNATIONAL 124 ( 3 ) 820 - 832 1996.3

Language：English Publisher：BLACKWELL SCIENCE LTD

The pseudospectral method is a high-accuracy numerical modelling technique which requires less memory and CPU time than traditional numerical modelling techniques, such as finite difference. However, full 3-D modelling is still computationally intensive. As we must compromise between realism and computational efficiency, we have developed a 2.5-D pseudospectral scheme for calculating 3-D elastic wavefields in media varying in two dimensions. To demonstrate the feasibility of the scheme described in this paper, we use data from a refraction survey carried out in 1984 by the Explosion Seismology Group in the southeastern foothills of the Hidaka Mountains, Hokkaido, Japan.

DOI： 10.1111/j.1365-246X.1996.tb05640.x

2.5-D modelling of elastic waves using the pseudospectral method

T Furumura, H Takenaka

GEOPHYSICAL JOURNAL INTERNATIONAL 124 ( 3 ) 820 - 832 1996.3

Language：English Publisher：BLACKWELL SCIENCE LTD

DOI： 10.1111/j.1365-246X.1996.tb05640.x

Effect of 2-D topography on the 3-D seismic wavefield using a 2.5-D discrete wavenumber-boundary integral equation method

H Takenaka, BLN Kennett, H Fujiwara

GEOPHYSICAL JOURNAL INTERNATIONAL 124 ( 3 ) 741 - 755 1996.3

Language：English Publisher：BLACKWELL SCIENCE LTD

DOI： 10.1111/j.1365-246X.1996.tb05635.x

Imaging of Subsurface Faults Using Teleseismic Waveform -Numerical Experiments-

MURAKOSHI Takumi, TAKENAKA Hiroshi, SUETSUGU Daisuke, SAITA Tomoharu

Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 49 ( 3 ) 389 - 401 1996

Language：Japanese Publisher：SEISMOLOGICAL SOCIETY OF JAPAN

We develop a method for imaging subsurface faults using teleseismic waveform data. The target of our method is not an entire velocity structure, but location and size of a subsurface fault. The method consists of the following steps: (1) pre-processing of observed records, (2) selection of trial model (initial model of structure), (3) estimation of incident wavefield from the bottom of the studied region, (4) forward calculation, (5) calculation of the steepest descent direction of the model parameters, (6) image analysis and identification of faults. The idea of the method has been originally proposed by TAKENAKA et al. (1996). In the present paper we examine the feasibility of the approach using the synthetic data and several trial models in the two dimensional SH cases. We also here propose a practical technique to estimate the incident wavefield from the observed data. In the numerical examination, we could recover the image of the subsurface fault for all trial models we used, which indicates our method has potentiality for sensing real subsurface faults and encourages further development of the method.

DOI： 10.4294/zisin1948.49.3_389

Imaging of subsurface faults using teleseismic waveform -Numerical experiments-(共著)

MURAKOSHI Takumi, TAKENAKA Hiroshi, SUETSUGU Daisuke, SAITA Tomoharu

Zisin(J. Seism. Soc. Japan) 49 ( 3 ) 389 - 401 1996

Language：Japanese Publisher：SEISMOLOGICAL SOCIETY OF JAPAN

DOI： 10.4294/zisin1948.49.3_389

An imaging technique for subsurface faults using teleseismic-wave records - SH case

H Takenaka, T Murakoshi, D Suetsugu, T Furumura

JOURNAL OF PHYSICS OF THE EARTH 44 ( 5 ) 529 - 541 1996

Language：English Publisher：CENTER ACADEMIC PUBL JAPAN

It is important for disaster prevention and public safety design to know whether subsurface faults exist, not only in Kobe, which was heavily damaged by the 1995 Hyogo-ken Nanbu earthquake, but also in any urban area which is tectonically active. However, there is still little information on subsurface faults. In this paper, we propose a new approach for sensing subsurface faults using teleseismic-wave array records. Our new method employs an imaging technique similar to the reflection method, but is much less expensive and can be used in urban areas. The target of our method is not the velocity structure itself, but rather the position and size of a subsurface fault. The imaging algorithm is based on the steepest descent method, which is also used in waveform inversion of reflection data. However, since iteration is not required by our approach, only one forward computation together with reverse-time computation of the wavefield is required. The method proposed in this paper consists of the following steps: 1) pre-processing observed records, 2) forward calculation, 3) calculation of the steepest descent direction of the model parameters, and 4) image analysis and identification of faults. The feasibility of the method is demonstrated using SH synthetic data.

DOI： 10.4294/jpe1952.44.529

An imaging technique for subsurface faults using teleseismic-wave records - SH case

H Takenaka, T Murakoshi, D Suetsugu, T Furumura

JOURNAL OF PHYSICS OF THE EARTH 44 ( 5 ) 529 - 541 1996

Language：English Publisher：CENTER ACADEMIC PUBL JAPAN

DOI： 10.4294/jpe1952.44.529

Numerical 3-D modeling of seismic waves by the pseudospectral method(共著)

Butsuri-Tansa(J. SEGJ) 49 ( 6 ) 536 - 548 1996

1995年奄美大島近海地震余震の喜界島における広帯域震観測（共著）

九州大学理学部研究報告(地球惑星科学) 19 ( 2 ) 173 - 189 1996

Pseudospectral法による地震波動の3次元計算（共著）

物理探査 49 ( 6 ) 536 - 548 1996

Broadband strong-motion observation in Kikai Island for aftershocks of the 1995 Amamioshima-Kinkai earthquake(共著)

Science Reports, Department of Earth and Planetary Sciences, Kyushu University 19 ( 2 ) 173 - 189 1996

Sensing of subsurface faults based on an imaging technique for teleseismic waveform data II-Feasibility study for application to oblique incidence, multi-event and noise data.

村越匠, 竹中博士, 末次大輔, 斉田智治, 古村孝志

物理探査学会学術講演会講演論文集 94th 1996

A reflection/transmission matrix formulation for elastic-wave scattering by an irregular fluid-solid interface.

岡元太郎, 竹中博士

地球惑星科学関連学会合同大会予稿集 1996 1996

Surface-layer correction for numerical solutions of seismic waves.

斉田智治, 竹中博士, PITARKA A, 末次大輔

地球惑星科学関連学会合同大会予稿集 1996 1996

Broadband strong-motion observation of aftershocks of ’95 Amamioshima-kinkai earthquake in Kikai Island.

藤井雄士郎, 奥村貴史, 竹中博士, 鈴木貞臣

地球惑星科学関連学会合同大会予稿集 1996 1996

An extended profile of the explosion seismic observation in Unzen volcano, Kyushu.

鈴木貞臣, 勝俣啓, 山崎義典, 三浪俊夫, 石原和彦, 竹中博士

地球惑星科学関連学会合同大会予稿集 1996 1996

Sensing of faults for teleseismic wave form data. Feasibility study for application to multi-event and noise data.

村越匠, 竹中博士, 末次大輔

日本地震学会秋季大会講演予稿集 1996 1996

3.9.1.6 地震波伝播の3次元数値シミュレーションに関する研究(3.9.1 関係機関との共同研究,3.9 共同研究,3. 研究業務)

藤原広行, 竹中博士

防災科学技術研究所年報 5 57 - 57 1995.3

3.4.2(2) 不均質媒質における地震波伝播の理論並びにその地下構造推定への応用に関する研究(3.4.2 科学技術特別研究員,3.4 科学技術振興費による研究,3. 研究業務)

竹中博士

防災科学技術研究所年報 5 40 - 40 1995.3

A WRAPAROUND ELIMINATION TECHNIQUE FOR THE PSEUDOSPECTRAL WAVE SYNTHESIS USING AN ANTIPERIODIC EXTENSION OF THE WAVE-FIELD

T FURUMURA, H TAKENAKA

GEOPHYSICS 60 ( 1 ) 302 - 307 1995.1

Modeling seismic wave propagation in complex media

H Takenaka

JOURNAL OF PHYSICS OF THE EARTH 43 ( 3 ) 351 - 368 1995

Language：English Publishing type：Book review, literature introduction, etc. Publisher：CENTER ACAD PUBL JAPAN

We review the studies on modeling seismic wave propagation in complex media, which were carried out during the past 10 years by researchers at Japanese institutions. Special emphasis is placed on those works which are perceived as important but had little exposure outside Japan. We can say that the fundamental development of method for seismogram synthesis in the (3, 1) dimension was completed, where the first and second numbers in parentheses are the space dimensions of the wavefield and the heterogeneity of the medium. However, seismologists have been eager to model seismic propagation in the (2, 2), (3, 2), and (3, 3) dimensions during the last 10 years. Modeling seismic wave propagation in a full (3, 3) dimension is now limited to simple small-scale problems because of the extensive computation and large memory, even when using a supercomputer. Nevertheless, in laterally and vertically heterogeneous media, we have to calculate 3-dimensional wavefields in order to analyze real seismic records quantitatively. There exist two potential breakthroughs. One is to assume the medium is axisymmetric and the other to model(3, 2) dimensional wave propagation (the so-called 2.5 dimensional problem). Numerical methods have the potential to simulate seismic wave propagation in realistic environments of substantial spatio-temporal extent. Since we are not used to processing such an abundance of information, we have to investigate methods for analyzing and interpreting large volumes of computational data. These studies may well challenge our conception of seismic wave propagation.

DOI： 10.4294/jpe1952.43.351

Aftershock observation of the 1995 Hyogo-ken Nanbu earthquake in Awaje Island : strong motion and broad band observation(共著)

T. Okumura, H. Takenaka, S. Suzuki, T. Sasatani, M. Furumura, S. Saito, T. Matsushima, T. Furumura

Sci. Repts. , Dept. Earth & Planet. Sci. , Kyushu Univ. 19 ( 1 ) 103 - 123 1995

The 1995 Hyogo-ken Nanbu earthquake occurred on January 17 1995. The maximum seismic intensity was seven in Kobe city and a part of Awaji island. The aftershocks were observed at three stations in Awaji island using three strong-motion seismometers and a broad-band seismometer from January 19 to April 4. During this period, 89 events were oberved. In these events, nine events were observed at all of the three stations. Among the nine events, three events were analysed using integration of velocity in the time domain and amplitude spectrum of S-wave for 5 seconds. Amplitude spectral ratios of two events occurring in Kobe side for 20 seconds from P-wave arrival, for 20 seconds from S-wave arrival, and S-wave part for 5 seconds were also analysed. Those amplitude spectra showed predominant frequency around 1-4 Hz for IWY and ABK stations, but TSM predominant frequency around 4-7 Hz. The spectral ratio shows 3-10 times amplification, around 1-2 Hz and 4-7 Hz for TSM/IWY, and around 0.9-2 Hz and 4-7 Hz for ABK/IWY. For TSM/IWY, 2-5 times attenuation was observed around 2-3 Hz.

A wraparound elimination technique for the pseudospectral wave synthesis using an antiperiodic extension of the wavefield(共著)

T. Furumura, H. Takenaka

Geophysics 60 ( 1 ) 302 - 307 1995

A simple but effective technique for wraparound elimination called antiperiodic extension is proposed. This technique is based on a simple modification of the wavefield. A brief description of the Fourier differentiation and wraparound phenomenon are given. Two methods for elimination of wraparound are then compared. The first is based on Cerjan's method, and the second on the concept of Fourier differentiation for an antiperiodically extended wavefield as developed in this note. To demonstrate the validity of the present technique, it is applied to 2-D elastic modeling (P-SV case) of a syncline structure where an explosive-type source is considered. -from Authors

DOI： 10.1190/1.1443760

淡路島における1995年兵庫県南部地震の余震観測-強震動及び広帯域余震観測-（共著）

九州大学理学部研究報告(地球惑星科学) 19 ( 1 ) 103 - 123 1995

TREATMENT OF AN INFINITELY EXTENDED FREE-SURFACE FOR INDIRECT FORMULATION OF THE BOUNDARY-ELEMENT METHOD

T YOKOI, H TAKENAKA

JOURNAL OF PHYSICS OF THE EARTH 43 ( 1 ) 79 - 103 1995

Language：English Publisher：CENTER ACADEMIC PUBL JAPAN

A new approach which uses the full-space Green's function is proposed to eliminate the influence of the finitude of the segmented free surface in the indirect formulation of the Boundary Element Method. The absence of a contribution from the far parts of the free surface that are neglected in the computation is compensated for, assuming that the wave field along flat parts of the surface far from the localized irregularity can be substituted by the reference solution, i.e., the wave field in the half space with a completely flat free surface which is given analytically. The nonphysical waves radiated at the two ends of the segmented model of the free surface are eliminated efficiently by this approach. This reduces the amount of computer main memory required and the CPU time consumed for calculation. Moreover, physical consideration of the relation to existing approaches shows clearly that our approach gives a more precise approximation, in particular for high frequency problems. The capacity of the indirect formulation of the Boundary Element Method therefore is bettered by this approach.

DOI： 10.4294/jpe1952.43.79

Modeling seismic wave propagation in complex media

Hiroshi Takenaka

Journal of Physics of the Earth 43 ( 3 ) 351 - 368 1995

Language：English

We review the studies on modeling seismic wave propagation in complex media, which were carried out during the past 10 years by researchers at Japanese institutions. Special emphasis is placed on those works which are perceived as important but had little exposure outside Japan. We can say that the fundamental development of method for seismogram synthesis in the (3, 1) dimension was completed, where the first and second numbers in parentheses are the space dimensions of the wavefield and the heterogeneity of the medium. However, seismologists have been eager to model seismic propagation in the (2, 2), (3, 2), and (3, 3) dimensions during the last 10 years. Modeling seismic wave propagation in a full (3, 3) dimension is now limited to simple small-scale problems because of the extensive computation and large memory, even when using a supercomputer. Nevertheless, in laterally and vertically heterogeneous media, we have to calculate 3-dimensional wavefields in order to analyze real seismic records quantitatively. There exist two potential breakthroughs. One is to assume the medium is axisymmetric and the other to model (3, 2) dimensional wave propagation (the so-called 2.5 dimensional problem). Numerical methods have the potential to simulate seismic wave propagation in realistic environments of substantial spatio-temporal extent. Since we are not used to processing such an abundance of information, we have to investigate methods for analyzing and interpreting large volumes of computational data. These studies may well challenge our conception of seismic wave propagation. © 1995, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan. All rights reserved.

DOI： 10.4294/jpe1952.43.351

Treatment of an infinitely extended free surface for indirect formulation of the boundary element method(共著)

Toshiaki Yokoi, Hiroshi Takenaka

J. Phys. Earth 43 ( 1 ) 79 - 103 1995

A numerical generator of low-frequency earthquakes.

竹中博士, 後藤章夫

日本火山学会講演予稿集 1995 1995

Synthetic seismograms by using the Pseudospectral method. (9). The possibility of parallel computation for three-dimensional modeling.

古村孝志, 竹中博士

地球惑星科学関連学会合同大会予稿集 1995 1995

A recursive algorithm on the new basis for elastic waves in horizontally layered media.

斉田智治, 竹中博士, GELLER R J, 羽鳥友彦

地球惑星科学関連学会合同大会予稿集 1995 1995

A numerical generator of monochromatic events.

竹中博士, 後藤章夫

日本地震学会秋季大会講演予稿集 1995 1995

Sensing of faults for teleseismic wave form data. Numerical experiments.

村越匠, 竹中博士, 末次大輔, 古村孝志

日本地震学会秋季大会講演予稿集 1995 1995

Seismic Activities Associated with Ground Deformation at the Summit of Unzen Volcano.

清水洋, 松尾のり道, 馬越孝道, 松島健, 竹中博士

地球惑星科学関連学会合同大会予稿集 1995 1995

Sensing of subsurface faults based on an imaging technique for teleseismic wave form data. numerical experiments.

村越匠, 竹中博士, 末次大輔, 古村孝志

物理探査学会学術講演会講演論文集 92nd 1995

A recursive algorithm on the new basis for elastic waves in horizontally layered media.

斉田智治, 竹中博士, 羽鳥友彦, GELLER R J

物理探査学会学術講演会講演論文集 92nd 1995

MODELING STRONG-MOTION IN THE ASHIGARA VALLEY FOR THE 1990 ODAWARA, JAPAN, EARTHQUAKE

AS PITARKA, H TAKENAKA, D SUETSUGU

BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 84 ( 5 ) 1327 - 1335 1994.10

Language：English Publisher：SEISMOLOGICAL SOC AMER

Finite-difference seismograms are calculated for the 1990 Odawara earthquake. Using a basin structure derived from a geotechnical survey and a double-couple solution determined from the P first-motion data, a two-dimensional SH finite-difference calculation reproduces the observed spatial variation in amplitude and waveform of the transverse records at the Ashigara Valley Blind Prediction Sites for frequencies lower than 2 Hz. Comparison of the synthetics and the observed seismograms suggests that the observed amplitude variation of the transverse records in the Ashigara Valley is mainly due to the source radiation pattern rather than the basin structure. Several different double couples are used in the waveform modeling to show the sensitivity of ground motion to the source mechanism. We thus conclude that it is important to use an appropriate focal mechanism to model near-field ground motion.

MODELING STRONG-MOTION IN THE ASHIGARA VALLEY FOR THE 1990 ODAWARA, JAPAN, EARTHQUAKE

AS PITARKA, H TAKENAKA, D SUETSUGU

BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 84 ( 5 ) 1327 - 1335 1994.10

Language：English Publisher：SEISMOLOGICAL SOC AMER

CALCULATION OF SURFACE-WAVES FOR A THIN BASIN STRUCTURE USING A DIRECT BOUNDARY-ELEMENT METHOD WITH NORMAL-MODES

H FUJIWARA, H TAKENAKA

GEOPHYSICAL JOURNAL INTERNATIONAL 117 ( 1 ) 69 - 91 1994.4

Language：English Publisher：BLACKWELL SCIENCE LTD

An efficient method to synthesize surface waves in a thin sedimentary basin exhibiting lateral heterogeneities is proposed. This method is based on the direct boundary element method; that is, it represents the wavefield by integral equations along boundaries. The excitation and propagation of surface waves by lateral heterogeneities are incorporated into the numerical scheme by using propagation operators and superposition, where the Green's function is computed by the summation of normal modes when the horizontal distance between the source and receiver is large, which reduces computation costs. Using the properties of the surface-wave part of Green's function, the number of elements needed for discretization can be reduced. This formulation can be effective for both the physical interpretation of certain observed phases and for numerical calculations, In this paper, only 2-D SH problems are considered, and the extension to 2-D P-SV problems and 3-D problems is discussed briefly.

DOI： 10.1111/j.1365-246X.1994.tb03304.x

CALCULATION OF SURFACE-WAVES FOR A THIN BASIN STRUCTURE USING A DIRECT BOUNDARY-ELEMENT METHOD WITH NORMAL-MODES

H FUJIWARA, H TAKENAKA

GEOPHYSICAL JOURNAL INTERNATIONAL 117 ( 1 ) 69 - 91 1994.4

Language：English Publisher：BLACKWELL SCIENCE LTD

DOI： 10.1111/j.1365-246X.1994.tb03304.x

竹中博士

防災科学技術研究所年報 4 41 - 41 1994.3

北海道南西沖地震に伴う津波-小樽から礼文島まで-(共著)

月刊海洋号外 ( 7 ) 153 - 158 1994

Surface waves in a sedimentary basin(共著)

469 - 474 1994

堆積盆地内で発生する表面波（共著）

第9回日本地震工学シンポジウム(1994)論文集,第1分冊 469 - 474 1994

Visualization of the wavefield synthesized by using a numerical simuration method.

古村孝志, 竹中博士, 岡部成玄

情報処理学会夏のプログラミング・シンポジウム報告集 1993 1994

Source Characteristics of the Ashio Earthquake Swarm.

木下繁夫, 藤原広行, 池田隆司, 竹中博士, 吉本和生, 佐藤春夫

地球惑星科学関連学会合同大会予稿集 1994 1994

Non-linear Elastic Waveform Inversion for Heterogeneous Earth Structure. A Numerical Test.

末次大輔, PITARKA A S, 竹中博士

日本地震学会秋季大会講演予稿集 1994 1994

Synthetic seismograms by using the Pseudospectral method. (8). Free-surface boundary condition and its stability of the computation.

古村孝志, 竹中博士

日本地震学会秋季大会講演予稿集 1994 1994

Synthetic seismograms by using the Pseudospectral method. (7). High-frequency noise reduction for the stabilization of the computation.

古村孝志, 竹中博士

地球惑星科学関連学会合同大会予稿集 1994 1994

THE INTEGRAL OPERATOR REPRESENTATION OF PROPAGATION INVARIANTS FOR ELASTIC-WAVES IN IRREGULARLY LAYERED MEDIA

H TAKENAKA, BLN KENNETT, K KOKETSU

WAVE MOTION 17 ( 4 ) 299 - 317 1993.8

Language：English Publisher：ELSEVIER SCIENCE BV

The reflection and transmission of elastic waves in irregularly layered media can be represented in terms of a set of propagation invariants for elastic wavefields. There are a number of such invariants depending on different integral operators acting on the displacement and traction fields. By exploiting different classes of invariants, representations for reflection and transmission operators at an irregular interface can be derived which are easier to compute than previous forms.
In a similar way, a simplified representation for the surface amplification factor for incident waves on a free surface can be constructed. This is particularly useful for calculating theoretical seismograms on the surface of a body.

DOI： 10.1016/0165-2125(93)90010-D

THE INTEGRAL OPERATOR REPRESENTATION OF PROPAGATION INVARIANTS FOR ELASTIC-WAVES IN IRREGULARLY LAYERED MEDIA

H TAKENAKA, BLN KENNETT, K KOKETSU

WAVE MOTION 17 ( 4 ) 299 - 317 1993.8

Language：English Publisher：ELSEVIER SCIENCE BV

DOI： 10.1016/0165-2125(93)90010-D

Reduction of the Memory Consumption in the Aki-Larner Method

3.4.2(3) 不均質媒質における地震波伝播の理論並びにその地下構造推定への応用に関する研究(3.4.2 科学技術特別研究員,3.4 科学技術振興費による研究,3. 研究業務)

竹中博士

防災科学技術研究所年報 3 50 - 50 1993.3

不整型地盤における地震波動の数値計算法

竹中博士

地震2 42 391 - 403 1993

OHORI Michihiro, TAKENAKA Hiroshi, KOKETSU Kazuki, MINAMI Tadao

Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 45 ( 4 ) 357 - 363 1993

Language：Japanese Publisher：SEISMOLOGICAL SOCIETY OF JAPAN

Aki-Larner method (ALM) is a very powerful technique to calculate the seismic responses of layered media having irregular interfaces. However, it is necessary to solve complex simultaneous equations with very large full matrices so that it takes very long time and consume much memory. Recently, Ohminato et al. (1990) proposed a Galerkin method and suggested that wavenumber coupling between far separated elements in the submatrices of the full matrices are very week if the lateral irregurality is gentle. Their idea seems to be applicable to the analyses of ALM, too. Therefore, in this paper, we estimated possible reduction of the memory consumption in the ALM by neglecting most of non-diagonal elements of the submatrices. Through the 2-dimensional (2-D) analyses, we calculated responses due to vertically incident plane SH-wave and studied the effect of the neglect of non-diagonal submatrix elements on the accuracy of results. Six types of alluvial valleys with different shape were used and the error caused by the neglect was evaluated in comparison with results obtained by the conventional ALM. As a result, we can treat submatrices as band matrices with 1/4 or 1/6 width if the lateral irregularity is gentle, and this leads to reduction of the memory consumption in the Aki-Larner method for the simulation in high frequencies or 3-D problems.

DOI： 10.4294/zisin1948.45.4_357

Is the fast Hartley transform more efficient than FFT? (共著)

Furumura Takashi, Takenaka Hirosi, Ninomiya Ichizo

Transactions of the Japan Society for Industrial and Applied Mathematics 3 ( 3 ) 245 - 255 1993

Language：Japanese Publisher：The Japan Society for Industrial and Applied Mathematics

This paper discusses the effectiveness of the fast Hartley transform(FHT) when it is applied to some signal processing problems. FHT is a real-valued transform and is quite similar to the fast Fourier transform(FFT) except the properties such as the reciprocity of the transform. In the last decade, more than dozens of papers have been published with the assertion that FHT offers an alternative to FFT with the advantage of its time and memory-space. In the present paper, we discuss that FHT has no explicit advantage over real-valued FFT in terms of the computation based on our comparative experiment.

DOI： 10.11540/jsiamt.3.3_245

Reduction of the memory consumption in the Aki-Larner method(共著)

Computational methods for seismic wave propagation in complex subsurface structures

TAKENAKA H.

Zisin 46 ( 2 ) 191 - 205 1993

不整形地盤における波動伝播の数値計算法

地震 46 ( 2 ) 191 - 205 1993

OHORI Michihiro, TAKENAKA Hiroshi, KOKETSU Kazuki, MINAMI Tadao

Zisin 45 ( 4 ) 357 - 363 1993

Language：Japanese Publisher：SEISMOLOGICAL SOCIETY OF JAPAN

DOI： 10.4294/zisin1948.45.4_357

高速ハートレ変換は高速フーリエ変換を越えるか?（共著）

日本応用数理学会論文誌 3 ( 3 ) 245 - 255 1993

A Field Survey of Tsunami Generated by the Hokkaido-Nansei-Oki Earthquake. From Otaru to Rebun Island.

後藤章夫, 高橋浩晃, 宇津木充, 小野忍, 西田泰典, 大島弘光, 笠原稔, 竹中博士, 斉田智治

日本地震学会秋季大会講演予稿集 1993 1993

Visualization of reciprocity by using a numerical simulation method.

古村孝志, 竹中博士

日本地震学会秋季大会講演予稿集 1993 1993

Calculation of three-dimentional elastic wave field in two dimensional structure using BEM.

藤原広行, 竹中博士

日本地震学会秋季大会講演予稿集 1993 1993

Near-field Observation of Small Earthquakcs Occurring in the Dome of Unzen Volcano

Goto Susumu, Suzuki Sadaomi, Takenaka Hiroshi, Shimizu Hiroshi

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 1993 63 - 63 1993

端に不連続を持つデータのためのFourier微分法-対称法-(共著)

FURUMURA T.

物理探査 45 ( 4 ) 303 - 309 1992

Numerical simulation and visualization of seismic wavefield(共著)

FURUMURA T.

Rep. Cent. Infor. Process. Educ., Center for Information Processing Education, Hokkaido Univ. 11 ( 11 ) 25 - 34 1992

地震動の数値シミュレーションの波動場の可視化（共著）

北海道大学情報処理教育センター広報 ( 11 ) 25 - 34 1992

Effect of 2-D Mountain Topography on the 3-D Seismic Wavefield : Isotropic P-wave Source

Takenaka H., Kennett B. L. N.

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 1992 35 - 35 1992

2-D REFLECTIVITY METHOD AND SYNTHETIC SEISMOGRAMS FOR IRREGULARLY LAYERED STRUCTURES .2. INVARIANT EMBEDDING APPROACH

K KOKETSU, BLN KENNETT, H TAKENAKA

GEOPHYSICAL JOURNAL INTERNATIONAL 105 ( 1 ) 119 - 130 1991.4

Language：English Publisher：BLACKWELL SCIENCE LTD

Laterally varying interfaces cause coupling between wavenumbers so that seismograms in two-dimensionally layered media can be synthesized by means of 'supermatrices', which include the coupled contributions of all the wavenumbers. We introduce reflection and transmission 'supermatrices' in order to eliminate numerical problems arising from loss of precision for evanescent waves in the seismogram synthesis. An interface is assumed to be such that the reflected and transmitted wavefields on its two sides can be represented as purely upgoing and downgoing waves, i.e. the Rayleigh ansatz is imposed. The computational demands of this method can be kept to a minimum by exploiting propagation invariants in the coupled wavenumber domain.
The superior performance of this 'invariant embedding' approach when compared to propagator or finite difference schemes is illustrated by application to the response of sedimentary basins to excitation by an incident plane wave or a line force. The results are in good general agreement with the other methods, but show greater numberical stability and computational efficiency. In the case of a single interface the 'invariant embedding' procedure for P-SV-waves takes 45 per cent less computation time and 29 per cent less memory than the propagator method of Koketsu (1987a, b). The gains are reduced in a multilayer case because of the level of computation required to calculate the addition rules for the large reflection and transmission supermatrices.

2-D REFLECTIVITY METHOD AND SYNTHETIC SEISMOGRAMS FOR IRREGULARLY LAYERED STRUCTURES .2. INVARIANT EMBEDDING APPROACH

K KOKETSU, BLN KENNETT, H TAKENAKA

GEOPHYSICAL JOURNAL INTERNATIONAL 105 ( 1 ) 119 - 130 1991.4

Language：English Publisher：BLACKWELL SCIENCE LTD