Faculty Profiles - TAKENAKA Hiroshi

MISC - TAKENAKA Hiroshi

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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

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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.

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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

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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

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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

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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

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