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2007年
年月日： ２００７年 ２月１９、２０日 発表者： 福山英一 博士 （独立行政法人防災科学技術研究所） 題目： 地震破壊の構成法則と動的地震破壊過程
2006年
年月日： ２００６年１１月２７日 発表者： Dr. Rafael Benites （Institute of Geological and Nuclear Sciences, New Zealand） 題目： A ground motion transfer function matrix for two nearby rock and soil sites 概説： I attempt to compute local site effects based on a matrix transfer function that incorporates the coupling among the three components of motion of a soil and a rock (reference) sites. The matrix is obtained from a generalized inverse formulation, considering the records of many earthquakes incident from a wide range of azimuths and depths, at both sites. The formulation also incorporates the covariance among the three components for all the earthquakes. The method is applied to calculate the amplification factors of the strong ground motion network sites in the Wellington Region, New Zealand, showing the main features produced by the standard spectral ratios, the cross coupling effects, and the directions of maximum amplitude. 年月日： ２００６年１１月２７日 発表者： Dr. Luis Angel Dalguer （San Diego State University） 題目： Accuracy of Dynamic Rupture Models and their Potential Application to Study Different Aspects of Earthquakes Phenomena 概説： Contrary to kinematic models, dynamic rupture models investigate the physical processes involved in the fault rupture, incorporating conservation laws of continuum mechanics, constitutive behavior of rocks under interface sliding, and state of stress in the crust. These earthquake physic models have the potential to contribute to our understanding of the physical causes of the rupture process, and therefore to improve our capability for predicting source-dominated ground motion phenomena. But appropriate numerical model is important to avoid misleading conclusions, due to numerical bias, that may have significant implications when evaluating earthquake problems. Here we assess the accuracy of different fault representation methods and demonstrate that appropriate fault representation in a numerical scheme is crucial to reduce uncertainties in numerical simulations of earthquake source dynamics and ground motion, and therefore important to improving our understanding of earthquake physics in general. In addition to other potential applications of dynamic models, here we discuss the importance of high resolution models of large scale earthquake to study two open subjects of ongoing debate: (1) rupture at bimaterial interface in 3D and the mechanism for exciting the prefered-direction unilateral rupture, and (2) the difference of faulting and near source ground motion of surface and buried earthquakes. 年月日： ２００６年 ８月２、３日 発表者： 福山英一 博士 （独立行政法人防災科学技術研究所） 題目： 応力場と動的破壊過程
2005年
年月日： ２００５年 ３月１０日 発表者： 竹中博士 助教授 （九州大学大学院理学研究院） 題目： 弾性波動場の計算法＜上級編＞ 概説： 問題の本質を突いた超効率的解法2.5D，Quasi-cylindrical，Quasi-sphericalアプローチへのいざない
2004年
年月日： ２００４年 ３月２２日 発表者： 竹中博士 助教授 （九州大学大学院理学研究院） 題目： 弾性波動場の計算法＜中級編＞ 概説： 昨年度<初級編>では，水平成層構造における弾性波動を計算する方法の一つである Propagator Matrix法を扱いました。Propagator Matrix法は「周波数領域」における 平面波の表現をに基づいた半解析的な手法で，その定式化を通して波動理論と計算法 の両方の基礎をエンジョイされたと思います。今回<中級編>では，PropagatorMatrix 法で扱った水平成層構造（正確には，今回は１次元任意不均質構造）における平面波 入射問題を純粋な数値解法である「時間領域」の差分法（FDTD法）で解くことを考え ます。1次元構造の平面波入射問題を従来の３次元の差分法で解くとたいへん効率が 悪いので（美しくないので），専用の支配方程式を導くことから始めます。その作業 を通して，時間領域と周波数領域の波動の表現の違いを認識し，周波数領域の表現だ けでは見えてこなかった様々なことに気づきます。次にこの支配方程式をスタガード 格子差分を用いて離散化します。こうして得られたFDTD法の式は，本質的に空間１次 元なので単純そうに見えますが，差分解法に伴う種々の問題や現象を存分に体感でき る，絶好の題材です。最後に方法を実際の地震学的な問題に適用した例を紹介します。 年月日： ２００４年 ３月 ４日 発表者： Prof. Peter Moczo (Geophysical Institute, Slovak Academy of Sciences, Bratislava, Slovak Republic) 題目： Hybrid finite-difference and finite-element modeling of seismic motion 年月日： ２００４年 ３月 ４日 発表者： Dr. Rengin Gok (PD researcher, Lawrence Livermore National Laboratory Livermore) 題目： Source properties of the 1999 North Anatolian fault zone, Turkey, earthquakes 年月日： ２００４年 ２月１８日 発表者： Dr. Ali Oncel （独立行政法人産業技術総合研究所 活断層研究センター） 題目： Seismic source characterization defined by minima of local recurrence tim before the 2003 MJ8.0 Tokachi-Oki Earthquake 概説： We specify the most likely locations of asperities in the Tokachi-Oki rupture plane and compare their places, sizes and numbers to suggested asperities defined by strong-motion modelling. We used the technique of mapping local recurrence time (TL) based on the declustered microseismicity that is homogeneous for MJ8.0 during 1997-2003. We mapped TL in the rupture area bounded by 41.5°-42.8° latitude and 143°-144.9° longitude. TL is the probabilistic estimate of recurrence time, calculated from the a- and b-values.
2003年
年月日： ２００３年６月４、１１日 発表者： 関口春子 博士 （独立行政法人産業技術総合研究所 活断層研究センター） 題目： 震源過程の波形インバージョンの基礎 ６月４日 概説： 地震動波形記録から震源断層面上のすべりの時空間的な発展の様子を推定す る、波形インバージョン法の基礎的な考え方を説明します。また、実際の解析で避け て通れない、インバージョンの不安定を押さえる拘束条件と、非物理的な拘束条件を どのようにもっともらしく与えるか（ABICの考え方）について、紹介します。 題目： 震源過程の波形インバージョンの最近の話題 ６月１１日 概説： 波形インバージョン解析の最近の動向、震源モデルを使った震源の動力学や強震動の 研究など。
年月日： ２００３年 ３月１３日 発表者： Dr. Martin Mai (Institute of Geophysics, ETH Hoenggerberg, Zurich) 題目： Earthquake Source Modeling: From a Hydraulically Controlled Fault Model to Near-Field Ground Motion Simulation 概説： Most damage from large earthquakes occurs in close proximity to a fault, but our knowledge of the underlying physical processes of earthquake rupture is still limited. Studying earthquake source dynamics is therefore a critical task in order to improve rupture simulations for near-field ground motion prediction. Finite-fault rupture models have shown the spatio-temporal complexity of earthquake rupture, but what controls this source complexity? How can we efficiently generate physically self-consistent earthquake scenarios that capture the highly variable spatio-temporal slip evolution, as seen in dynamicrupture models? Moreover, near-source directivity effects are determined by the hypocenter position with respect to regions of high stress release on the fault. Which processes or geologic structures determine the location of these high-slip zones? What relates the point of rupture nucleation to the slip/stress distribution on the fault? In this presentation, we will show initial results on a hydraulically controlled fault model (Hillers & Miller, 2002) that may be used to generate earthquake source models within a long-term evolutionary tectonic system. Such source models serve as a starting point to compose rupture scenarios using the pseudo-dynamic source characterization (Guatteri, Mai, Beroza, 2002). The pseudo-dynamic source model provides physically self-consistent rupture realizations that have been shown to result in realistic near-source ground motion simulations. Within the framework of this earthquake source modeling, we will also analyze the rupture initiation, and investigate how the hypocenter position is related to the final slip distribution.
年月日： ２００３年 ３月１３日 発表者： Dr. Wojciech Debski (Visiting Researcher in Tono Geoscience Center) 題目： The Monte Carlo technique as a tool for solving seismological inverse problems 概説： Almost all geophysical inference about the Earth's structure and physical processes going on inside the Earth, like, for example, core-mantle interaction, thermal convection, earthquake raptures to name a few are carried out on the base of the surface made measurements. This type of inference where the required information are not directly measured but rather extracted from other data called inverse problemscan be carried out in various ways. The oldest, simplest and most popular approach is a search for a model which the best fits (in a given sense) to observed data. This casts the inverse problem to an optimization task easily managed numerically. Classical least squares approach is an example of this approach. However, this technique has a serious disadvantage, namely it can hardly provide (especially in nonlinear cases) a reliable estimation of an accuracy of thesolution found. This limitation is overcome by the Bayesian approach to inverse problems. The Bayesian method relies not on the search a single optimum model but rather constructs the posteriori probability density over the whole model space (space of all possible solutions) which expresses our knowledge that a given model is the true one. Simplifying matter one can say that the global maximum of the a posteriori probability corresponds to the optimum model found by optimization approach and additional information like width of the distribution, or generally its shape provides information on accuracy of the solution, correlation among parameters, existence of secondary solutions, etc. However, as the a posteriori distribution is usually a multi-parameter function its exploration requires very efficient numerical methods. Monte Carlo techniques are the most suitable methods that can be used nowadays for this purpose. In the first part of this talk I shortly present and compare both optimization and Bayesian approaches to inverse problems followed by a short presentation of the Monte Carlo Sampling techniques (Markov Chain Monte Carlo). In the second part I would like to illustrate previous theoretical considerations by three seismological examples (if time permits) namely seismic velocity tomography, estimation of the earthquake source time function, and finally advanced acoustic location for ocean geodesy.
2002年
年月日： ２００２年１２月２６、２７日 発表者： 竹中博士 助教授 （九州大学大学院理学研究院） 題目： 弾性波動場の計算法＜基礎編＞ On propagator matrix methods for calculating elastic wavefields 概説： 水平成層媒質における弾性波動を計算する方法の一つにPropagator Matrix法があります。この方法はやや古典的ではありすが，現在でも実用の場で広く 使われています。Propagator Matrix法の定式化の仕方には，数学的には等価な様々 なやり方がありますが，この講義では，数学的なエレガントさよりも，我々が地震波 について持っている直感的なイメージや実際の記録を解析する際の常識（習慣）にで きるだけ則した実用的な定式化を考えていきます。これは波動の理論が見え隠れする 楽しい作業です。この作業を通して波動理論と計算法の両方の基礎を学ぶことができ ます。 講義の1日目は平面波入射問題，2日目は震源問題を扱います。いずれも2次元波動場 の問題を考えます。一方的な講義ではなくできるだけディスカッションしながら皆さ んの理解を確かめながら進めて行きたいと思っています。
年月日： ２００２年９月１８、２５日 発表者： 関口春子 博士 （独立行政法人産業技術総合研究所 活断層研究センター） 題目： 地震の破壊過程解明のための波形インバージョン手法の新展開 ９月１８日 概説： 地震の断層破壊の時空間的発展のようすを調べる方 法（マルチタイムウィンドウ線形波形インバージョン法）の原理、 実際の解析上必要となる拘束条件などについて話します。 題目： 速度論的震源インバージョンから動力学震源破壊過程へ −新たなる震源像の構築− ９月２５日 概説： 震源インバージョンの結果を使って、断層破壊の動的 性質や将来の地震の震源像の予測などの研究がなされていま すが、その一端を紹介しようと思います。
年月日： ２００２年３月１１日 発表者： 井出 哲 博士 （東京大学地震研究所） 題目： 地震波動エネルギーのスケーリングと空間分布 Scaling and spatial distribution of seismic energy
年月日： ２００２年３月１１日 発表者： Dr. Mariagiovanna Guatteri （Stanford University） 題目： Improving strong ground motion prediction with stochastic-dynamic source models
年月日： ２００２年２月２５日 発表者： Prof. Xiaofei Chen （Dept. Geophysics, Beijing University） 題目： A hybrid inversion algorithm for retrieving earthquake source rupture process
2001年
年月日： ２００１年１２月１８、１９日 発表者： 宮武 隆 助教授 （東京大学地震研究所） 題目： 偏微分方程式の差分解法〜固体地球物理学・特に地震学への応用〜 １２月１８日 FDM for partial differential equations −Application to Seismology-, Dec. 18 断層近傍強震動パルスの成因 １２月１９日 Generation mechanisms of near-source strong ground motion pulses, Dec. 19
年月日： ２００１年９月２６日 発表者： 干場充之 博士 （気象庁松代精密地震観測室） 題目： 震源・サイト・パスをConvolution表現した時の振幅のバラツキとDirectivityの影響 Fluctuation of wave amplitude and directivity effects when assuming convolution of source, path and site factors
年月日： ２００１年９月３日 発表者： Dr. Norman A. Abrahamson (Pacific Gas and Electric Company) 題目： Incorporation of geologic data and source scaling models into seismic hazard analyses
年月日： ２００１年７月４、１１日 発表者： 関口春子 博士 （独立行政法人産業技術総合研究所 活断層研究センター） 題目： 震源破壊過程研究のための波形インバージョン法の基礎 ７月 ４日 概説： 地震の破壊が時空間的発展を推定する方法の一つに、 波形インバージョンがあり、この方法の理論的基礎、 解くべき連立方程式の組み方、観測記録の絶対的不足と 部分超過の問題とこれに対応するインバージョン法や 拘束条件、観測方程式と非物理的事前情報拘束条件との 折り合いをつけるABICという情報量基準について。 題目： 波形インバージョン、および、波形インバージョン＋αより 明らかになった震源破壊過程 ７月１１日 概説： 過去の地震の波形インバージョンからどんなことが わかったか。波形インバージョンより得られた震源モデルを 使って動的破壊のシミュレーションや地震動シミュレーションを 行う研究について。
年月日： ２００１年６月１２日 発表者： Prof. Gregory C. Beroza (Stanford University) 題目： Bringing Seismicity into Focus
年月日： ２００１年３月１６、１７日 発表者： 福山英一 博士 （防災科学技術研究所） 題目： 地震破壊伝播速度は何で決まるか？ ３月１６日 What is Rupture Velocity Controlled by? 断層の屈曲や分岐と強震動の発生 ３月１７日 Strong Motions Caused by Dynamic Rupture along Curved/Branched Fault 鳥取県西部地震の微細断層構造 Very Fine Fault Structure of the 2000 Westen Tottori Earthquake
年月日： ２００１年３月１６日 発表者： Dr. Ross Stein (USGS, Menlo Park) 題目： Looking Past Izmit's Fate to Istanbul's Future: An interaction-based probability calculation
年月日： ２００１年３月１６日 発表者： Dr. Susan Hough (USGS, Pasadena) 題目： Remotely Triggered Earthquakes
年月日： ２００１年３月９日 発表者： 干場充之 博士 （気象庁松代精密地震観測室） 題目： 震源・サイト・パスをConvolution表現した時の振幅のバラツキ Fluctuation of wave amplitude when assuming convolution of source, path and site factors. 概説： 観測される地震動のフーリエスペクトルは，震源の項，パスの項，およびサイトの増 幅特性の積で表現される場合が多い．上記の表現を用いて，相対的な震源の強さや， パスの影響（たとえばＱ値など），サイトの増幅特性の定量的な見積もりが行なわれ ているが、この表現の定量的な限界を考慮して議論されることは少ない．講演では， この表現を用いた時にどの程度，スペクトルの振幅に不安定性（バラツキ）があるの か，についての考察を行い，さらにその原因について議論する． Seismic wave spectrum are often represented by convolution of source, path and site amplification factors. Using the representation some authors have been estimating relative source powers, site amplification factors or attenuation (Q values) and discussing quantitative difference of them without consideration of uncertainty (fluctuation) of the representation. Is the uncertainty is really so small? The topic of the talk is how much uncertainty we should expect in this representation, and discussion of the reason of the uncertainty.
年月日： ２００１年３月９日 発表者： 中原 恒 博士 （東北大学大学院理学研究科） 題目： 高周波地震波形記録のエンベロープインバージョンに基づく断層破壊過程の研究 Study of the fault rupture process based on inversion analyses of high-frequency seismogram envelopes 概説： 断層破壊過程を明らかにする上で，特に周波数約１Hz以下の低周波数帯では波形イ ンバージョン法が成功をおさめ，近年では数多くの地震に対して断層面上のすべり量 分布が明らかにされている．しかし１Hz以上の高周波数帯では，地球のランダムな不 均質構造の影響によって波形が大きく乱され，波形インバージョン法の直接的な適用 は困難であった．そこで我々は，まず，位相情報を無視して波のエンベロープ形状 （包絡波形）に着目し，輻射伝達理論に基づいてランダム不均質構造中における多重 散乱過程を定式化した．さらに，これを基に，断層面上からのエネルギー輻射量分布 を求めるインバージョン法を構築し，近年発生した中・大地震について解析を行って きた．講演ではこれまでの解析結果をまとめて報告する．
年月日： ２００１年１月２９、３０日 発表者： 宮武 隆 助教授 （東京大学地震研究所） 題目： 強い揺れのメカニズム １月２９日 Mechanisms of strong ground motions, Jan 29 動力学モデルによる強震動シュミレーション １月３０日 Strong motion simulation based on dynamic models, Jan 30
2000年
年月日： ２０００年１０月２７日 発表者： Mr. P. Martin Mai (Dc. Student) (Department of Geophysics, Stanford University) 題目： Near-Source Strong Motion Prediction Using a Random-Field Earthquake SourceModel 概説： Prediction of strong ground motion in future earthquakes is the central challenge of engineering seismology. Attenuation relations have long been used to predict the behavior of simple characterizations of ground motion intensity (such as peak ground acceleration or spectral ordinates for given frequency and damping) as a function of earthquake size and distance. Several factors, such as permanent displacements and directivity effects, cause strong ground motion to be qualitatively different in the extreme near field than at somewhat larger distances. These factors act to make near-field ground motions for a particular intensity (e.g. PGA) substantially different from ground motions of the same intensity, observed at a greater distances from the fault. Although recent large earthquakes have added important new observations, there remains a scarcity of strong motion data in the extreme near field of large earthquakes. Simulations of strong ground motion for realistic earthquake scenarios will therefore play a central role in predicting the level and variability of strong motion in the near field of large earthquakes. We perform simulations that provide realistic strong motion synthetics. We characterize the earthquake source using a random-field model for the slip distribution on the rupture plane whose dimensions are constrained by source-scaling relations. The parameters for the random field description as well as for the source-scaling are derived from published finite source models. Our simulations for single-magnitude earthquake scenarios demonstrate the large variability of ground motions due to near-field effects that are not accounted for in standard attenuation relations. We extend our study to the multi-magnitude case in which we compute ground motions for a range of magnitudes and source sizes at various distances to the fault. We compare common measures of ground motion intensity (spectral acceleration, spectral displacement, peak ground acceleration) for the simulated strong motions against existing attenuation laws, demonstrating the usefulness of our method to capture the variability of strong ground motion in the near-field of large earthquakes.
年月日： ２０００年６月２１日 発表者： Dr. Nelson Pulido (EDM, RIKEN) 題目： Introduction of dynamic source process to strong motion seismology
年月日： ２０００年６月１４日 発表者： 関口春子 博士 (東京大学地震研究所) 題目： マルチタイムウィンドウ線形波形インバージョン法の、実地震への適用についてー 1999年トルコ・コジャエリ地震および1995年兵庫県南部地震の破壊過程 概説： 地震破壊の時空間的発展の様子を調べる方法の中でも最も広範に用いら れている、マルチタイムウィンドウ線形波形インバージョン法の、実地震への適用 について話をします。まず、実地震への適用を行う際に必要になってくる２つの事柄、 実地震記録の不充分であることから起こる逆問題の不安定性を抑える拘束条件4 のこと、そして、異質の式である観測方程式と拘束条件の式を一緒にしてインバ ージョンする際にこれらの間に妥当な釣り合いを見つける考え方について、 話をします。それから、1995年1月17日の兵庫県南部地震と1999年8月17日の トルコ、コジャエリ（イズミット）地震の破壊過程の解析に、適用した例を紹介 します。
年月日： ２０００年３月７日 発表者： 干場充之 博士 Dr. Mitsuyuki Hoshiba （気象研究所） (Meteorological Research Institute) 題目： 深さ依存性を持つ構造での散乱減衰と内部減衰の分離推定 Scattering Attenuation and Intrinsic Absorption Using Uniform and Depth Dependent Model 概説： Two seismic wave attenuation factors, scattering attenuation Qs-1 and intrinsic absorption Qi-1 are measured using the Multiple Lapse Time Window (MLTW) analysis method for three different frequency bands, 1-2, 2-4, and 4-8Hz. Data from 54 temporally deployed seismic stations located in northern Chile are used. This method compares time integrated seismic wave energies with synthetic coda wave envelopes for a multiple isotropic scattering model. In the present analysis, the wave energy is assumed to decay with distance in proportion to1/GSFoexp[-(Qs-1+Qi-1)ow r/v], where r,w and v are the propagation distance, angular frequency and S wave velocity, respectively, and GSF is the geometrical spreading factor. When spatial uniformity of Qs-1, Qi-1 and v is assumed, i.e. GSF=4pr2, the estimates of the reciprocal of the extinction length, Le-1 [=(Qs-1+Qi-1)ラw/v], are 0.017, 0.012 and 0.010km-1, and those of the seismic albedo, B0 [=Qs-1/(Qs-1+Qi-1)], are 0.48, 0.40 and 0.34 for 1-2, 2-4 and 4-8Hz, respectively, which indicates that scattering attenuation is comparable to or smaller than intrinsic absorption. When we assume a depth dependent velocity structure, we also find that scattering attenuation is comparable to or smaller than intrinsic absorption. However, since the quantitative estimates of scattering attenuation depend on the assumed velocity structure (strength of velocity discontinuity and/or Moho depth), it is important to consider differences in velocity structure models when comparing attenuation estimates.
年月日： ２０００年２月２５日 発表者： Prof. Niren N. BISWAS （Geophysical Institute, University of Alaska, Fairbanks） 題目： Investigation of soil class and site response in Anchorage, Alaska
年月日： ２０００年２月２５日 発表者： Prof. Apostolos PAPAGEORGIOU （University of New York, Buffalo） 題目： Modelling of earthquake ground motions for regions of moderate seismicity: a case study
1999年
年月日： １９９９年１１月５日 発表者： Dr. Kim B. Olsen (Institute for Crustal Studies, U.C. Santa Barbara) 題目： 1. Modeling dynamic rupture in a heterogeneous stress field 2. Ground motion amplification in Los Angeles from 3D modeling of wave propagation 概説： 1. Modeling dynamic rupture in a heterogeneous stress field by K.B. Olsen, E. Fukuyama, and R. Madariaga Abstract: We study the propagation of seismic ruptures along a fault surface subject to a heterogeneous stress distribution. When prestress is uniform, rupture propagation is simple but presents some non-trivial differences with the circular shear crack models of Kostrov. The best known difference is that rupture can start only from a finite initial patch. The other difference is that rupture is asymmetric with the rupture front elongated in the inplane direction. If the initial stress is sufficiently high, the rupture front makes a transition to super-shear speeds. For simple rectangular faults or asperities rupture propagation is clearly controlled by the width of the fault or asperity. When stress or strength are heterogeneous rupture propagation changes completely and is controlled by local length scales in the initial stress distribution as well as rupture resistance. Thus short rise times (Heaton pulses), rupture arrest, stopping phases, variations in rupture velocity, etc reflect the length scales of the stress and strength distributions. In particular, we have analysed the effects of variations of the initial stress on the rupture velocity. The rupture velocity tends to increase in areas where the ratio of initial stress to yield stress is high (low rupture resistance) and vice versa. This is also the case for areas with neighboring asperities of low rupture resistance. Through a number of numerical experiments we have identified a non- dimensional parameter that controls rupture. This parameter measures the ratio of local available strain energy to fracture energy derived from the friction law. A bifurcation occurs when this parameter is greater than a certain critical value that depends mildly on the geometry of the stress distribution on the fault. We have verified that the non-dimensional parameter, computed using frictional parameters determined by different studies for several recent earthquakes (e.g., the 1992 Landers event) are near the critical value. Our results suggest that earthquakes are critical phenomena controlled by a single local non-dimensional number. 2. Ground motion amplification in Los Angeles from 3D modeling of wave propa gation by K.B. Olsen Abstract: We have used 0-0.5 Hz finite-difference, finite-fault simulations to estimate the three-dimensional (3D) response of the Los Angeles basin to nine different earthquake scenarios. Amplification is quantified as the peak velocity obtained from the 3D simulation divided by that predicted using a regional one-dimensional (1D) crustal model. Average amplification factors are up to a factor of 4, with the values from individual scenarios typically differing by as much as a factor of 2.5. The average amplification correlates with basin depth, with values near unity at sites above sediments with thickness less than 2 km, and up to factors near 6 above the deepest (~ 9 km) and steepest-dipping parts of the basin. There is also some indication that amplification factors are greater for events located farther from the basin edge. If the 3D amplification factors are divided by the 1D vertical SH-wave amplification below each site, they are lowered by up to a factor of 1.7. The duration of shaking in the 3D model is found to be longer, by up to more than 60 seconds, relative to the 1D basin response. The simulation of the 1994 Northridge earthquake reproduce recorded 0-0.5 Hz particle velocities relatively well, in particular at near- source stations. The synthetic and observed peak velocities agree within a factor of two and the log standard deviation of the residuals is 0.37. This is a reduction of 45% compared to the overall regression value for pseudoacceleration response spectra obtained by Boore et al. (1997) at 0.5 Hz. This result suggests that long-period ground motion estimation can be improved considerably by including the 3D basin structure.
年月日： １９９９年１０月４、５日 発表者： 宮武 隆 助教授 （東京大学地震研究所） 題目： 震源過程と強震動のシミュレーション １０月４日 Faulting processes and strong ground motions Oct. 4 震源モデル：運動学と動力学 １０月５日 Source models: Kinematics and Dynamics Oct. 5
年月日： １９９９年７月７日 発表者： 福山英一 博士 （防災科学技術研究所） 題目： 断層破壊において、断層変位量、破壊伝播速度、すべり継続時間は何で決まるか？ What are fault slip, rupture velocity, and rise time controlled by ? 第1部 基礎編 2時ー3時 Part 1 Basic theory for earthquake source dynamics, 2.00 to 3:00 第2部 応用編 3時15分ー4時30分 Part 2 Application to earthquake ruputure process 概説： まず、境界積分方程式法の仕組みを２次元の簡単な定式化を例にとって説明します。 その方法を３次元に拡張し、１)断層変位量は応力降下量によって、一意に決まる事。 ２)破壊伝播速度は(応力降下量に関係する)局所的な歪みエネルギーと破壊エネルギ ー(破壊によって消費されるエネルギー)とのバランスで決められる事。３)すべり継 続時間は、臨界すべり量等の摩擦パラメータで決められる事。をなるべく分かりやす く話します。
年月日： １９９９年６月３０日、７月１日 発表者： 藤原広行 博士 （防災科学技術研究所） 題目： グリーン関数の基礎とその最先端 ６月３０日 Bases of Green's functions and their cutting-edge techniques Jun. 30 高速多重極展開法による地震波散乱問題の解法 ７月１日 Fast multipole method to solve elastic wave scattering problems Jul. 1
年月日： １９９９年６月１７日 発表者： Dr. Sri Widiyantoro （Department of Geophysics & Meteorology, Bandung Institute of Technology, Indonesia） 題目： Structure of subduction zones worldwide from P- and S-wave tomography
年月日： １９９９年４月１５日 発表者： Dr. PETUKHIN, Anatoly, G. （Kamchatka Experimental and Methodological Seismological Department GSRAS, Now： JSPS Fellow, DPRI, Kyoto Univ.） 題目： STUDY OF GROUND STRONG-MOTIONS ON KAMCHATKA, RUSSIA 概説： Petukhin A.G. (1) and A.A.Gusev(2) (1) Email： agp@egmdpri01.dpri.kyoto-u.ac.jp, (2) Institute of Volcanic Geology and Geochemistry FEB RAS First strong motion records on Kamchatka were obtained in 1960-70, first at station Petropavlovsk, and then at other stations of Kamchatka regional network. Observations that are more systematic started around 1980, when the network of 25 strong-motion stations was installed. At present, the archive of analog strong-motion records of KEMSD includes more than 1000 records of earthquakes with intensity up to 8 MSK. The standard processing procedure for these records includes their digitizing, estimation of instrument parameters from calibration data, correction of instrument errors and calculation of record parameters. The development of the complete Kamchatkan strong-motions database is in progress. Analysis of the digitized data enabled us to determine the specific Kamchatka average relationship between peak acceleration Amax, moment magnitude Mw and distance R; and also a preliminary version of average relationship of amplitude Fourier spectrum FSA vs Mw, R and site conditions. The mean level of these relationships, at the same values of Mw and R, is comparable with that for Japan and substantially greater than that for Western USA. There are prominent station anomalies (for Amax and FSA) for some stations. These anomalies are probably related with the site conditions. The most striking example is the station Kruglyi： peak acceleration of 0.99g has been recorded here in 1993, at the distance 70 km from Mw=7.5 event. This high frequency amplification is related with the pocket of hydrothermally altered rock that outcrops very near to the instrument pedestal.
年月日： １９９９年３月１日 発表者： Prof. Xiao-Fei Chen （Dept. of Geophysics, Beijing Univ., China） 題目： Seismic Surface waves in irregular multi-layered media 概説： Seismic Surface waves in irregular multi-layered media, in which I will present the new theory of surface waves in irregular multi-layered media. First, I will show briefly the derivation of surface wave fields in irregular media. Surprisingly, we will see some distorted modes, dispersion surface, ... etc. in laterally heterogeneous media, instead of the concepts of normal modes and dispersion curves we are familiar in the case of laterally homogeneous media. Also, I will show some interesting features of the wavefields in laterally heterogeneous media.
年月日： １９９９年３月１日 発表者： Prof. John N. Louie （Seism. Lab., University of Nevada, USA, Now visiting： School of Earth） 題目： Seismic Imaging of Faults in California and Nevada 概説： A key issue in estimating the earthquake hazard to the Los Angeles area is the hidden subsurface geometry of blind thrust faults. Competing thin- and thick-skinned compressional tectonic models propose very different thrust widths and thus maximum magnitudes. Recent developments in velocity inversion and reflection imaging make it possible to observe complex geometric relations among active crustal faults. I use forward- and back-scattered fault-plane reflections from earthquakes, recorded on seismic network stations, to image thrusts. This technique imaged a mid-crustal bright spot at the same location as a large active-source experiment. Images of the 1994 Northridge source zone establish the underlying thrust as a thick-skinned fault system cutting the Moho. In the Basin and Range extensional province, the earthquake risk may be low, but the mechanisms of Neogene tectonics are controversial. Active-source survey records there show reflections from normal- and oblique-slip faults. Simulated-annealing velocity optimization allows a prestack Kirchhoff migration to reconstruct these fault-plane reflections into true-dip sections. A unique image from Death Valley shows the listric geometry of a normal fault. The Dixie Valley fault plane, which ruptured in 1954, dips at only 28 degrees in 1998 survey results. Basin and Range extension may well follow more thin-skinned models.
年月日： １９９９年２月１５日 発表者： Prof. Steven M. DAY （Dept. Geological Sciences, San Diego State University, USA） 題目： Rupture dynamics of segmented faults
年月日： １９９９年２月１５日 発表者： Dr. Arben PITARKA （URS Greiner Woodward Clyde, USA） 題目： Synthesized near-fault ground motion using hybrid Green's function method
年月日： １９９９年２月１０日 発表者： Dr. Andreas Rietbrock （University of Potsdam, Germany, now JSPS Fellow, in DPRI） 題目： P-wave attenuation structure in the fault area of the 1995 Kobe earthquake 概説： Using aftershock records from the 1995 Kobe (Hyogo-ken Nanbu) earthquake the three dimensional P wave attenuation structure in the Kobe epicentral area is determined. Waveform data from both permanent seismic networks and portable stations, set up following the Kobe mainshock, were used. Using an w2-type source model the observed P-wave amplitude spectra were inverted for the spectral plateau value, the source corner frequency and a frequency independent t*-operator. The determined t*-operators were subsequently used for the computation of the 3D absorption structure using a 3D velocity model. For the estimation of reliable spectral parameters only high quality amplitude spectra were used, resulting in a final data set of about 4100 t*-operators. In the upper part of the crust two regions of high absorption were found. One is below the northern part of Awaji island and reaches down to a depth of 5 km. The other one, Northeast of Kobe city, is along the Arima-Takatsuki tectonic line and extends along the Rokko, Kashiodani, and Yamada Fault. To the north it reaches up to the Hokusetsu-Sanchi area. In both regions a high density of fault lineaations is mapped and also high Poisson ratios were determined. This suggests that partially saturated cracks are causing the observed high attenuation.
年月日： １９９９年２月４日 発表者： 干場充之博士 （気象研究所） 題目： 速度構造の小さな揺らぎによる最大振幅の大きなバラツキ −球面波の場合− Fluctuation of wave amplitude produced by fluctuation of velocity structure - For case of spherical wave - 概説： 地震波の速度構造は深さのみに依存する単純な階段関数的なものでモデル化 されることが多いが、実際の速度構造には小さな揺らぎが含まれていると考え られる。速度構造に揺らぎがあると、その中を通過する波は焦点効果、逆焦点 効果により振幅にバラツキが生じる。そこで、「速度構造にどの程度の揺らぎ があると、振幅はどの程度ばらつくのか？」 について考察を行う。なお、昨 年冬のセミナーで平面波が伝播する場合について紹介したので、今回は、さら に球面波の場合を考察し、両者の比較を行う。
1998年
年月日： １９９８年１２月２５日 発表者： Prof. Francisco J. SANCHEZ-SESMA （National Autonomous University of Mexico [UNAM], Mexico） 題目： Modeling 3D Seismic Response of Topographies and Basins using Boundary Elements: Strategies to Deal with Realistic Problems
年月日： １９９８年１２月 ８日 発表者： Prof. John G.Anderson （University of Nevada, Reno, U.S.A.） 題目： Uncertainties in the prediction of strong ground motions
年月日： １９９８年１２月 ８日 発表者： Prof. Peter Moczo （Slovak Academy of Sciences, Bratislava, Slovak Republic） 題目： Towards efficient finite-difference modeling of seismic ground motion
年月日： １９９８年１２月 ８日 発表者： Prof. Jacobo Bielak （Carnegie Mellon University, Pittsburgh, U.S.A.） 題目： Modeling and Forecasting of Earthquake Ground Motion in Large Basins
年月日： １９９８年１２月 ８日 発表者： Dr. Olivier Coutant （Universite Joseph Fourier, Grenoble, France） 題目： Contribution of Earthquake Doublet Analysis to the Characterization of Medium Properties Temporal Change and Site Effect
年月日： １９９８年１１月１８日 発表者： Dr. Alexei TUMARKIN （Univ. California, Santa Barbara (Now a visiting researcher of DPRI)） 題目： Seismic Energy Radiation from Earthquake Source Models
年月日： １９９８年１１月１０日 発表者： 纐纈一起 助教授 （東京大学地震研究所） 題目： 地震学における最小自乗法
年月日： １９９８年５月７日 発表者： Dr. Andreas Rietbrock （Free University of Berlin, Germany, now JSPS Fellow, DPRI） 題目： Velocity and Attenuation Tomography in the Central Andes (North Chile) 概説： Since the spatial distribution of seismic velocities is often insufficient for a detailed geological interpretation, it is necessary to extract as much information as possible from the recorded waveforms. Additionally to the velocity distribution we present a new technique for the determination of the 3D absorption structure. After the active seismic part of the ANCORP project a temporary seismological network was installed between Nov. 1996 and Mar. 1997 in the area between 20-23S and 67-70W. For the velocity and absorption tomography a data set of 620 events analyzed, which includes more than 11500 P-wave and 6500 S-wave travel times. Two different approaches calculating the t*-operators were considered. The determination of the 3D absorption structure was performed in the 3D velocity structure to incorporate accurately path effects. The main features of the 3D velocity distributions are very high P-wave velocities (> 8.5km/s) in the subducted slab and high Vp/Vs ratios directly above. In addition to results from the PISCO experiment the absorption tomography shows low attenuation in the forearc. A high absorption body can be seen beneath the recent magmatic arc extending from the top of the subducted slab up to upper crustal levels. The pattern of Vp/Vs ratios and Q can be interpreted to reflect dehydration processes in the lower plate and hydration and melting processes in the upper plate.
1997年
年月日： １９９７年１１月６、７日 発表者： 纐纈一起 助教授 （東京大学地震研究所） 題目： 地震波理論 ―地盤震動からグローバルまで―
年月日： １９９７年１０月２８日 発表者： Dr. Arben PITARKA （Woodward Clyde Co., USA） 題目： Ground Motion Amplification Pattern due to the Sedimentary Basin Response: Numerical experiments using 3D-FD techniques
年月日： １９９７年１０月２３日 発表者： Prof. David D．Jackson （UCLA） 題目： Characteristic earthquakes, seismic gaps, and really big earthquakes
年月日： １９９７年１０月２３日 発表者： Prof. Alexander A.Gusev （Russian Academy of Science） 題目： Non-Gaussian source-generated acceleration amplitudes as deduced from peak factors of Mexican accelerograms
年月日： １９９７年１０月２０日 発表者： Dr. David WALD （USGS, Pasadena, USA） 題目： The Los Angeles Basin Response in Simulated and Recorded Ground Motions
年月日： １９９７年１０月１５日 発表者： Prof. Peter MOCZO （Geophysical Institute, Slovak Academy of Science, Bratisclava, SLOVAK REPUBLIC, 防災研究所外国人研究員） 題目： Finite-Difference Modeling of Seismic Wave Propagation in Complex Media
年月日： １９９７年８月１１日 発表者： Dr. Paul G. Somerville （Woodward Clyde Co., USA） 題目： Seismological Characteristics and Engineering Quantification of Near-Fault Ground Motion
年月日： １９９７年８月１１日 発表者： Prof. Mostafa A. Foda （Univ. of California, Burkely, USA） 題目： Faraday Resonance in Soft Solids
年月日： １９９７年７月２９日 発表者： Prof. Yehua Zeng （Univ. of Nevada, RENO, USA） 題目： A composite earthquake source model - application to earthquake source imaging and strong motion simulation -
年月日： １９９７年７月１７日 発表者： Prof. Feng SU （Univ. of Nevada, RENO, USA） 題目： Site amplification and basin response on strong motion in Las Vegas
年月日： １９９７年４月１８日 発表者： Dr. John Haines （Institute of Geological and Nuclear Science, Nhquake ground motions by local site conditions） 題目： Representing distributed deformation of the Earth's surface using continuous velocity fields: an overview
年月日： １９９７年２月１９日 発表者： Prof. Francisco LUZON （Departamento de Fisica Aplicada,, Instituto Andaluz de Geofisica, Universidad de Almeria, ESPANA） 題目： The Seismic Response of 3D topographies with the IBEM: advantages and limitations
年月日： １９９７年２月４日 発表者： Dr. Michel Bouchon （University of Grenoble, France） 題目： Numerical Simulation of the Propagation of Rupture on faults with Complex Geometries
1996年
年月日： １９９６年８月７日 発表者： Prof. Yehuda Benzion （Geological Sciences, USC, USA, 東京大学地震研究所客員教授） 題目： Part 1. "Seismic radiation from laterally heterogeneous fault zones" Part 2. "Stress, slip and earthquakes in different fault systems"
年月日： １９９６年３月７、８日 発表者： 纐纈一起 助教授 （東京大学地震研究所） 題目： 地震学で見直す阪神大震災 ― 兵庫県南部地震の source, path, site ―
年月日： １９９６年３月６日 発表者： Dr. Xiao-fei Chen （Department of Earth Science of Univ. of Southern California, USA） 題目： Seismic waves (body waves & surface waves) excitation and propagation in the laterally heterogeneous media.
年月日： １９９６年３月１日 発表者： Dr. Paul Spudich （USGS Menlo Park, USA） 題目： The effects of topography, geology, and other factors on ground motions in recent Southern California earthquakes
1995年
年月日： １９９５年３月６日 発表者： Prof. Raul Madariaga （Departemant de Sismologie, Institut de Physique du Globe de Paris） 題目： Earthquake Source Dynamics. Friction and Complexity.
年月日： １９９５年２月９日 発表者： Prof. Francisco J. Sanchez-Sesma 題目： The Seismic Response of 3D Alluvial Basins using a Variational Method: Preliminary Results for Osaka Basin