Faculty Profiles - TAKENAKA Hiroshi

MISC - TAKENAKA Hiroshi

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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.

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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

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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

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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

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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 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

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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

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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

Reduction of the Memory Consumption in the Aki-Larner Method

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

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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

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