Application of the microtremor measurements to a site effect study

Earthquake has left much life and property damages. The occurrence of such events necessitates the execution of plans for combating the earthquakes. One of the most important methods for combating earthquakes includes assessing dynamic characteristics of soil and site effect. One of the methods by which one can state dynamic characteristics of the soil of an area is the measurement of microtremors. Microtremors are small-scale vibrations that occur in the ground and have an amplitude range of about0.1–1 microns. Microtremor measurement is fast, applicable, cost-effective. Microtremor measurements were taken at 15 stations in the Babol, north of Iran. Regarding H/V spectral ratio method, peak frequency and amplification factor were calculated for all microtremor stations.According to the analysis, the peak frequency varies from0.67 to 8.10 Hz within the study area. Also, the authors investigated the validity of the results by comparing them with SESAME guidelines and geotechnical conditions of study area. The microtremor analysis results are consistent with SESAME guidelines and geotechnical condition of study area. The results show that the microtremor observations are acceptable methods for assessing dynamic characteristics of soil and site effect in the Babol City.     

基于微动H/V谱比法的土石分界面探测研究——以济南中心城区为例

土石分界面对城市抗震设防和地下工程建设具有重要意义.城市中复杂的干扰限制了常规地球物理勘探方法的使用,本文选用环境友好且抗干扰能力强的微动H/V谱比法对济南中心城区的土石分界面展开研究.在济南中心城区开展三分量微动测量,得到了400多个测点的微动数据,计算了对应的H/V谱比曲线.将得到的H/V曲线划分成单峰、宽峰、双峰和无峰四种类型,分析了不同类型曲线与地质结构的关系.根据基岩性质不同,将研究区的基岩划分为灰岩和岩浆岩两种类型,总结出了基岩为灰岩时的深度-频率关系式,同时发现当基岩为岩浆岩时无法得到可靠的关系式.根据关系式计算得到了济南部分测线的土石分界面深度分布,另外,关系式的计算结果与钻孔资料十分吻合,能满足工程探测的精度要求.本方法为在城市强干扰环境中确定土石分界面深度提供了快速准确的解决方案.     

Point source identification using a simple permutation test: a case study of elevated PCDD/F levels in ambient air and soil and their relation to the distance to a local municipal solid waste incinerator

A point source for environmental pollution may be identified by the spatial association of samples collected in the vicinity of the emission source. In this study, we used a simple permutation test to explore the spatial correlations between the ambient air and soil polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) congener profile concentrations and their distances to a municipal solid waste incinerator (MSWI) in northern Taiwan. Kendall’s τ was applied for the correlation between the PCDD/F concentrations of a total of 9 airborne and 12 soil sampling sites and their distances to the incinerator. The results showed that the correlation was highly negatively associated for soil PCDD/Fs (τ = −0.515, p-value = 0.011) and was marginal for airborne PCDD/Fs (τ = −0.667, p-value = 0.055), conditional on the seasonal wind attributions. For the 17 individual congener profiles, most of the air and soil samples had a negative association, with 7 and 10 reaching statistical significance (p-value < 0.05) or borderline significance (0.05 < p-value < 0.10), respectively. The permutation test provides a simple and robust statistical method for the identification of a potential pollution source from a limited sample size. Our analytical results show that dioxin emissions from the investigated MSWI had a definite environmental impact on the surrounding area.     

Point source identification using a simple permutation test: a case study of elevated PCDD/F levels in ambient air and soil and their relation to the distance to a local municipal solid waste incinerator

A point source for environmental pollution may be identified by the spatial association of samples collected in the vicinity of the emission source. In this study, we used a simple permutation test to explore the spatial correlations between the ambient air and soil polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) congener profile concentrations and their distances to a municipal solid waste incinerator (MSWI) in northern Taiwan. Kendall’s τ was applied for the correlation between the PCDD/F concentrations of a total of 9 airborne and 12 soil sampling sites and their distances to the incinerator. The results showed that the correlation was highly negatively associated for soil PCDD/Fs (τ = −0.515, p-value = 0.011) and was marginal for airborne PCDD/Fs (τ = −0.667, p-value = 0.055), conditional on the seasonal wind attributions. For the 17 individual congener profiles, most of the air and soil samples had a negative association, with 7 and 10 reaching statistical significance (p-value < 0.05) or borderline significance (p-value < 0.10), respectively. The permutation test provides a simple and robust statistical method for the identification of a potential pollution source from a limited sample size. Our analytical results show that dioxin emissions from the investigated MSWI had a definite environmental impact on the surrounding area.     

The importance of ambient and forced vibration measurements for the results of seismic performance assessment of buildings obtained by using a simplified non-linear procedure: case study of an old masonry building

The seismic performance assessment of existing masonry buildings involves many uncertainties, whose impact can be reduced to some extent by using non-destructive in-situ tests of such buildings, at least when destructive in-situ tests, which can provide more reliable results, cannot be performed. In this paper the extent of the potential beneficial effects achievable by calibration of a structural model of a building to its experimentally estimated vibration periods has been investigated. This was done by performing measurements of ambient and forced vibrations on an old two-storey masonry building, and by then assessing its seismic performance using a simplified nonlinear method. The results of numerical investigations revealed that the natural vibration periods of such buildings can be reproduced with sufficient accuracy, although it is possible that they will be overestimated or underestimated by analysts by up to around 40 %. This means that the accuracy of the prediction of the intermediate results of the seismic performance assessment of any particular building can be significantly increased by calibration of the structural model. Additionally, the beneficial effects of such calibration were observed even in the case of the final outcome of the nonlinear analysis, which is expressed through the near-collapse limit state capacity in terms of the peak ground acceleration.