Adsorption behaviour of dibutyl phthalate on marine sediments

Laboratory experiments were carried out to investigate the adsorption behaviour of dibutyl phthalate (DBP) on marine sediments collected from five different sites in Victoria Harbour, Hong Kong. DBP adsorption can be well described by the Langmuir isotherm. The maximum DBP adsorption capacity (Q(max)) of the marine sediments ranges from 53 to 79 mg g(-1), which has a positive correlation with their organic content. Around 90% of the organic can be removed from the sediments with treatment by H(2)O(2) oxidation, and the Q(max) then decreases to a range between 13 and 22 mg g(-1). The black carbon content of the sediments has a much greater DBP adsorption capacity than does the natural organic matter of the sediments. The amount of DBP adsorbed on the sediments increases as the salinity of the marine water increases.     

Numerical analysis of seismic wave amplification in Nice (France) and comparisons with experiments

The analysis of site effects is very important since the amplification of seismic motion in some specific areas can be very strong. In this paper, the site considered is located in the centre of Nice on the French Riviera. Site effects are investigated considering a numerical approach (Boundary Element Method) and are compared with experimental results. The experimental results are obtained thanks to real earthquakes (weak motion) and microtremor measurements. The investigation of seismic site effects through numerical approaches is interesting because it shows the dependency of the amplification level on such parameters as wave velocity in surface soil layers, velocity contrast with deep layers, seismic wave type, incidence and damping.In this specific area of Nice, experimental measurements obtained for weak motion lead to strong site effects. A one-dimensional (1D) analytical analysis of amplification does not give a satisfactory estimation of the maximum reached levels. A boundary element model is then proposed considering different wave types (SH, P, SV) as the seismic loading. The alluvial basin is successively assumed as an isotropic linear elastic medium and an isotropic linear viscoelastic solid with Zener type behaviour (standard solid). The influence of frequency and incidence is analysed. The thickness of the surface layer, its mechanical properties, its general shape as well as the seismic wave type involved have a great influence on the maximum amplification and the frequency for which it occurs. For real earthquakes, the numerical results are in very good agreement with experimental measurements for each motion component. The boundary element method leads to amplification values very close to the actual ones and much larger than those obtained in the 1D case. Two-dimensional basin effects are then very strong and are well reproduced numerically.     

Site effects at Euroseistest—II. Results from 2D numerical modeling and comparison with observations

This paper presents results of numerical modeling of site response for Euroseistest. Ground motion across a very detailed model of the subsoil of this valley has been simulated for vertically incident SH waves. The predominance of locally generated surface waves is very clear in the synthetic seismograms. These results are then compared with published studies of observed site effects at this basin and with a detailed analysis of two events in the time domain. It is discussed in which sense it is possible to obtain a good fit between observations and 1D models, even though the real behavior involves locally generated Love waves. For this reason, it can be misleading to rely on an incomplete observation such as empirical transfer functions. Finally, it is stressed that in order to predict ground motion in alluvial valleys the information contained in the phase cannot be neglected.     

Influence of water saturation on horizontal and vertical motion at a porous soil interface induced by incident SV wave

Recent field observations have indicated that water saturation of soils may strongly affect the vertical ground motion. A study is therefore carried out to investigate the effect of saturation on horizontal and vertical motion at an interface of porous soils with potential contributions directed to site evaluation based on field observations of both the horizontal and vertical motion. The problem described in this paper corresponds to an SV wave incident at the interface between the overlying soil and the underlying rock formation. The soils are modeled as partially water-saturated porous material with a small amount of air inclusions, while the rock are approximately regarded as ordinary one-phase solid. Theoretical formulation is developed for the computation of amplitudes of horizontal and vertical interface motion, which are expressed as functions of the degree of saturation, the angle of incidence as well as the frequency. Numerical results are given for a typical sand to illustrate the influence of saturation on the interface motion in two directions and their ratios. The present study demonstrates that the effect of water saturation may be substantial on both the horizontal and vertical motion as well as on their ratios, implying the importance of such effects in the interpretation of field observations.     

强震地面运动的理论地震学研究

本文从理论地震学的角度概述了强震地面运动研究中关于震源过程、场地效应和地面运动预测等方面的研究进展,提出了一些进一步的研究课题.     

Effects of surface topography on seismic ground response in the Egion (Greece) 15 June 1995 earthquake

The Greek coastal town of Egion on 15 June 1995 was shaken by a strong, small epicentral distance, earthquake that caused heavy damages to buildings and loss of life. The damages were concentrated in the central elevated part of the town whereas the flat coastal region remained almost intact. This non-uniform distribution of damage is studied in this article in terms of surface topography effects by conducting seismic response analyses of a simplified 2-D profile of the town. A dynamic finite element code implementing the equivalent-linear soil behavior (FLUSHPLUS) was used for the analyses and it was found that the step-like topography amplified greatly the intensity of motion without affecting its frequency content. The analyses showed that the motion recorded by an accelerograph installed at the center of the town is in agreement with the computed values; they also indicated a particularly intense amplification close to the crest of the steep slope, where a multi-story RC residential building partially collapsed. In contrast, the level of motion was found to be low at the flat coastal zone of the town where the earthquake damages were insignificant. It is concluded that the characteristic surface topography of the town played an important role in modifying the intensity of base motion.     

Dissolved and particulate trace metal fluxes through the central English Channel, and the influence of coastal gyres

Measurements of dissolved Cd, Co, Cu, Mn, Ni, Pb, and Zn have been made on a seasonal basis at five stations on a north–south transect across the central English Channel between Cherbourg and the Isle of Wight. Vertical and horizontal distributions of dissolved Cd, Pb, Cu and Zn are relatively uniform except for sampling sites near the English coast. Dissolved Mn and Co show increased concentrations in the English coastal waters, and for Mn the seasonal trend in concentration follows the pattern seen in the Strait of Dover with higher values in the late summer. Ni and Cu are higher in concentration on the English side, which reflects mainly riverine sources. Measurements were also made of particulate forms of the metals above plus particulate Al, Ca, Fe, Mg, Sr and Ti. Water column concentrations of particulate metals broadly follow the distribution of suspended particulate matter, with highest concentrations near the UK coast. Trace metal concentrations have been integrated with modelled data on fluxes of water to provide estimates of fluxes for these elements into the eastern Channel, and an initial comparison is made with data for fluxes of metals through the Strait of Dover obtained during an earlier study. A major influence on the fluxes of particulate metals through the Isle of Wight-Cherbourg transect is the gyre system to the South east to the Isle of Wight, which has important east to west as well as west to east transport components. For those elements where the dissolved form of the metal dominates, the large flow of water in the central Channel waters leads to major fluxes of the metals towards the east and the Strait of Dover. However, the high suspended particulate matter loadings in the coastal waters and impact of the gyre system lead to net east to west fluxes of particulate Al, Fe, Mn and Ti. Comparison of these fluxes with data on the net west to east transport of these materials through the Strait of Dover infers that there must be a significant supply of these particulate metals to the eastern Channel.     

考虑俯冲带潜在震源区的地震危险性算法研究及在中国海域的应用

本文研究了俯冲带潜在震源区离散化方法及考虑俯冲带高震级地震震源破裂面和震源深度的场点地震动计算方法,推导了俯冲带潜在震源区地震危险性计算公式,并使用中国海域及邻区地震危险性模型进行地震危险性试算。结果表明,本文建立的考虑俯冲带潜在震源区的地震危险性算法能够实现场点地震危险性计算时对俯冲带高震级地震震源破裂面和震源深度的考虑。     

新区划图双参数调整对剪力墙结构土建成本的影响

考虑到《中国地震动参数区划图》（GB 18306—2015）（中华人民共和国国家质量监督检验检疫总局等,2016）,提出了双参数调整原则,即对场地地震动峰值加速度和反应谱特征周期进行同时调整,以确定设计地震动反应谱,这势必会增加结构的土建成本。因此,基于Ⅱ类场地,对抗震设防烈度7度（0.15 g）的剪力墙结构在不同场地类别下的地震动参数进行推导。采用单一控制变量法,对某12层剪力墙结构按不同抗震设防烈度和不同场地类别进行设计,使其满足规范最低标准,计算相应的钢筋和混凝土材料用量;根据现时市场定额,比较分析单一地震动参数变化时的土建成本,研究结果可为工程实践提供一定参考。