平成22年度第1回総合防災セミナーのご案内

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日時：

平成22年5月7日（金）15:00-18:00

場所：

京都大学宇治キャンパス　京都大学宇治おうばくプラザ　セミナー室１・２（アクセスマップ）（構内地図）

プログラム：

講演１

講演者：

Prof. Francisco J. Sanchez-Sesma
（社会防災研究部門国際防災共同研究領域客員教授）

講演タイトル：

Some contributions of Professor F. J. Sanchez-Sesma to understand the effects of surface geology on seismic ground motion

講演概要：

Surface geology can generate significant changes on earthquake ground motion, thus producing concentrated damage. This is due to the very efficient trapping of energy (in basins) and/or to focusing of seismic waves by irregular interfaces and topographical features.These phenomena may lead to significant spatial variations of ground motion in both amplitude and duration.

In many circumstances site effects can be accounted for using the simple 1D shear model and therefore, many practical procedures to assess site effects use this model. However, lateral heterogeneity may complicate things as it produces locally generated surface waves that can increase both amplitudes and duration of ground motion. By means of ray theory and the discovery of families of solutions that do not produce diffraction S-S was able to find analytical solutions for wedges that account in simple manner for 2D effects. This is the basis of the so called origami method. The method allowed S-S and co workers computations for realistic sedimentary basins. Later S-S discovered a set of canonical examples of topographical amplifications at wedges. As part of the various attempts to understand the response of Mexico City Valley after the Great 1985 MIchoacan (M8.1) earthquake S-S discovered in recorded seismograms the Rayleigh wave and this allowed a more complete description of that event. This was made in cooperation with K Aki, M Campillo and J C Gariel.

In order to deal with 2D and 3D models of alluvial basins and topographies S-S developed first a very simplified indirect boundary method with sources away of the boundary. This made the method very popular in some engineering applications. Such an approach was applied in 2D scalar and vector cases. These findings were made with E Rosenblueth and others.

A variant of this idea lead S-S to use complete families to solve for the first time some problems of diffraction of elastic waves by irregularities in 3D. This was made in cooperation with I Herrera, J Aviles, S Chavez-Perez, L E Perez-Rocha among others. A simplified model that takes its ground on an analytic solution for 1D response and surface waves for an antiplane case was proposed for 2D and 3D models in cooperation with J L Rodriguez-Zuniga and L E Perez-Rocha.

In order to make more rigorous the boundary method the sources were placed at the boundary itself and the indirect boundary element method (IBEM) was generated for many applications in 2D, 2.5D and 3D. All this was possible thanks to cooperation with M Campillo, H Pedersen, J Ramos-Martinez, F Luzon, R Vai and others. In an attempt to extend the IBEM to inhomoheneous materials, S-S developed an analytical approximation of the elastodynamic Green function in 2D and it is being extended to 3D cases. This in cooperation with R Madariaga and K Irikura and recently with F Luzon, L Ramirez-Guzman and M Arellano.

In order to undertand the nature of diffraction S-S studied wedges and Sommerfeld solution for a semi-infinite crack and discovered a way to use their components to find the analytical solution of a finite crack. In this colaborated with U. Iturraran and R Vai. Recently S-S explored other implications of Green functions and has contributed to understand and explain the relationship between avearage correlations of ambient vibrations and the Green function. S-S has discovered various analytical solutions of canonical examples. His coworkers are M Campillo, A Rodriguez-Castellanos, M Perton, R L Weaver and F Luzon among others.

講演２

講演者：

賀　斌　特定准教授
（学際融合教育研究推進センター・極端気象適応社会教育ユニット）

講演タイトル：

気候変動及び人間活動を考慮した広域水・物質循環に関する研究
Study on large scale water and material cycle considering climate change and human activity

講演概要：

水循環は、水・物質移動とともに潜熱としてエネルギーの移動も担っており、地表面の大規模な土地利用変化は、グローバルな気候変動にまで関わっている。今後予想される途上国での人口増大や人間活動の拡大、特に農業拡大などに伴う水需要と環境負荷増加に対して、水環境はどのように変動するだろうか？そうした問題に対して客観的な資料を提示することは、科学技術の緊急かつ重要な役割である。さらに、近年、窒素の増大による地下水の深刻な硝酸汚染や湖沼の富栄養化についての報告も数多く見られる。しかし、広域における窒素負荷に関しては、水質汚濁のプロセスの全容はいまだ明らかになっていない。本研究では、こうした評価や予測を行うことができ、広域スケールの水循環および大気・植物・土壌の窒素フローをモデル化し、世界の大河川流域スケールで窒素負荷流出量を推定する。