Ⅲ.Chemistry

東京大学Editor : Tazaki, Kazue |田崎, 和

An investigation of the attenuation characteristics of distant ground motions in Peninsular Malaysia by comparing Values of recorded with estimated PGA and PGV

The development of a design motion requires some input on ground motion characteristics. For a country such as Malaysia, where historical data is lacking and seismic activities are low, the information on characteristics of ground motion may be obtained by utilizing established attenuation relationships. This study aims to investigate the characteristics of distant ground motions in Peninsular Malaysia, which originated from the active tectonic plate of Sumatra, by comparing recorded peak ground acceleration (PGA) and peak ground velocity (PGV) values with those estimated using four attenuation models. Selected attenuation models are the Atkinson and Boore (1995), the Taro et al. (1997), the Dahle et al. (1990), and the Si and Midorikawa (1999) models. The analysis for comparison was made by employing a maximum of 46 horizontal component accelerograms, recorded at 14 seismic stations. These are data derived from 15 interplate earthquakes between May 2004 and July 2007. Recorded PGA and PGV values were plotted on respective attenuation curves to examine ground motion attenuation characteristics. Results indicated that attenuation models, established for stable tectonic regions, provide good estimation of PGA and PGV for Sumatran earthquakes for magnitude range of 5.9 to 9.0. The study shows that the Dahle et al. (1990) model best represents the characteristics of ground motions in terms of PGA, while the Atkinson and Boore (1995) model gives appropriately estimate ground motions in tenus ofPGY

Conserved quantity of elastic waves in multi-layered media: 2D SH case — Normalized Energy Density

We introduce a new conserved quantity, Normalized Energy Density (NED), alternative to the conventional definition of energy for a layered structure in a 2D SH problem. NED is defined by the average of power of a half transfer function multiplied by the impedance, and the conservation across the material interface is analytically proved for a two-layered case. For three, four, and ten-layered cases, the conservation is examined by applying the Monte Carlo simulation method, and then NED is supposed to be conserved through the layers

地震活動度を考慮したマレーシアの耐震設計に関する提案

耐震設計の高度化をはかるためには、地域の地震動に関する様々な情報が重要である。PGAやPGVのような具体的な観測値が対象地域で十分に得られていれば、統計的に処理をすることでハザードを定量的に的に評価できるが、マレーシアのように地震活動度の低い地域では観測値が不十分なために直接評価することは難しい。そこで、他の地域に対して構築されている距離減衰式のうち、適切なものを選定して援用することを試みる。また、マレーシア全域で過去に発生した最大規模のマグニチュードの地震を想定し、比較的地震活動度の低いマレー半島に対してもこれに対応するPGAやPGDなどを評価するものとする。The development of a design motion for seismic resistant design requires ample information on the characteristics of ground motions. This information may be found by analyzing important time-domain parameters, such as the peak ground acceleration (PGA) and peak ground velocity (PGV). However, this is not a straight-forward task for a low seismicity region such as Malaysia because historical data is scarce due to low seismic activities. Thus, alternatively, the characteristics of ground motion at a site may be determined by utilizing established attenuation models. This entails the selection of appropriate attenuation models, which may best represent the seismicity of Malaysia. Another useful method of estimating possible ground motions in Malaysia is by predicting the maximum magnitude earthquakes from available historical data. The maximum magnitude earthquakes can then be used to determine the maximum acceleration and displacement that are expected to occur within inland Malaysia.耐震設計の高度化をはかるためには、地域の地震動に関する様々な情報が重要である。PGAやPGVのような具体的な観測値が対象地域で十分に得られていれば、統計的に処理をすることでハザードを定量的に的に評価できるが、マレーシアのように地震活動度の低い地域では観測値が不十分なために直接評価することは難しい。そこで、他の地域に対して構築されている距離減衰式のうち、適切なものを選定して援用することを試みる。また、マレーシア全域で過去に発生した最大規模のマグニチュードの地震を想定し、比較的地震活動度の低いマレー半島に対してもこれに対応するPGAやPGDなどを評価するものとする。The development of a design motion for seismic resistant design requires ample information on the characteristics of ground motions. This information may be found by analyzing important time-domain parameters, such as the peak ground acceleration (PGA) and peak ground velocity (PGV). However, this is not a straight-forward task for a low seismicity region such as Malaysia because historical data is scarce due to low seismic activities. Thus, alternatively, the characteristics of ground motion at a site may be determined by utilizing established attenuation models. This entails the selection of appropriate attenuation models, which may best represent the seismicity of Malaysia. Another useful method of estimating possible ground motions in Malaysia is by predicting the maximum magnitude earthquakes from available historical data. The maximum magnitude earthquakes can then be used to determine the maximum acceleration and displacement that are expected to occur within inland Malaysia

S-wave impedance measurements of the uppermost material in surface ground layers: Vertical load excitation on a circular disk

S-wave impedance is one of the most effective parameters used to study the ground motion amplification of soil deposits. We propose a new approach to measure the S-wave impedance of the uppermost material in surface ground layers. First, a circular disk is set on the ground surface, and it is vertically loaded by sinusoidal wave excitation. When the time series of the loading velocity is synchronized with the reaction force, the ratio of the reaction force to the loading velocity is proportional to the S-wave impedance. We then estimate the proportionality coefficient from numerical experiments and check its accuracy. The measurement error is estimated to be within 1% for the homogeneous half-space case. We also discuss the applicability of this new approach and its limitations on the basis of numerical experiments for inhomogeneous media: a two-layered medium and a one-dimensional (1-D) random medium. The proposed approach is effective for both cases if we select the appropriate circular disk size