Site effects at Euroseistest—I. Determination of the valley structure and confrontation of observations with 1D analysis

This paper describes the process of construction of the 2D model of Volvi's geological structure and results of empirical and theoretical approaches to the evaluation of site response at Euroseistest. The construction of the 2D model is based on a re-interpretation of the available geophysical and geotechnical data in an effort to improve the definition of the subsoil structure at Euroseistest in terms of the most important parameters needed to model site response. The results of this re-interpretation are compared with a previous published 2D model of the same alluvial valley. Different analysis of the measurements and different criteria in the synthesis of data have led to a different model, even if both studies had access to the same field measurements. This underscores the fact that a model results of an interpretation and is not uniquely determined by the data, no matter how detailed they are. The well known subsoil structure opened the possibility to correlate the geometry and the dynamic properties of the 2D model with the results of site response determined from a detailed analysis of two events in frequency and time domains and 1D numerical modeling. The study of site response shows the important effect of the lateral variations on the ground motion and suggests that the contribution of locally generated surface waves to the resonant peak may be important. In the case of Volvi's graben, the limitations of the 1D approximation to simulate ground motion under complex soil conditions in both frequency and time domains are also shown. This paper lays the ground for a companion article dealing with 2D site effects in this basin.     

随机地震动模拟的时间序列法及其工程应用

系统研究了AR和ARMA时间序列方法生成给定加速度功率谱人工地震波的新方法，根据相应理论编制了程序，并生成了人工地震加速时程曲线，然后用生成的人工地震波进行结构动力时程分析，与实际地震波分析的结果进行了对比，计算结果表明，本文用于合成人工地震波的方法是可行的，生成的人工波可以用于实际结构的地震反应分析。     

波浪能电站潜在社会经济效益多层次灰色评价

对海洋波浪能电站的潜在社会经济效益进行评价,旨在为电站选址和可行性分析提供参考。多层次灰色评价方法通过建立评价指标体系,采用专家评分法确定指标的权重和分值,定性与定量相结合得到综合评价值。其结果表明了电站建设对社会经济影响的程度。案例分析验证了综合评价方法具有可行性。     

Second-Order Wave Diffraction Around 3-D Bodies by A Time-Domain Method

A time-domain method is applied to simulate nonlinear wave diffraction around a surface piercing 3-D arbitrary body. The method involves the application of Taylor series expansions and the use of perturbation procedure to establish the corresponding boundary value problems with respect to a time-independent fluid domain. A boundary element method based on B-spline expansion is used to calculate the wave field at each time step, and the free surface boundary condition is satisfied to the second order of wave steepness by a numerical integration in time. An artificial damping layer is adopted on the free surface for the removal of wave reflection from the outer boundary. As an illustration, the method is used to compute the second-order wave forces and run-up on a surface-piercing circular cylinder. The present method is found to be accurate, computationally efficient, and numerically stable.     

华北地区地壳上地幔三维P波速度结构

利用华北地震科学台阵和首都圈地震台网记录的4511次近震和625次远震的P 波到时数据,采用纬度和经度方向分别为0.5deg;times;0.5deg;的网格划分,反演得到了华北北部地区（111deg;E——120deg;E,37deg;N——42deg;N）深至400km 的地壳上地幔三维P 波速度结构.层析成像结果表明,研究区的速度存在明显的横向不均匀性,随着深度增加横向不均匀性总体呈现减弱趋势.燕山隆起带在60——120km 深度内存在明显的高速异常,这与较大的岩石圈厚度有关;山西裂陷盆地、华北平原下方60km 深度存在明显低速异常,与软流圈的出现有关.燕山隆起带岩石圈厚度在120km 以上,明显比太行山隆起的岩石圈厚度大,与稳定大陆地区的岩石圈厚度一致.太行山山前断裂已切穿莫霍面,贯入岩石圈.研究区上地幔顶部大范围的低速异常反映了软流圈上隆的特点.在华北平原及燕山隆起下方200——300km 存在高速异常可能与太古代大陆板块岩石圈的残留体有关.     

简单的热带海气耦合波——Rossby和Kelvin波的相互作用

本文分析了当大气和海洋中未经耦合前的自由波分别为Kelvin波和Rossby波,经相互作用后所产生的耦合波的性质。结果表明,不管大气的自由波为Kelvin波或Rossby波,而海洋的自由波为Rossby波或Kelvin波,经相互作用后的耦合波可以分成两类。一类耦合波的色散关系接近自由的Kelvin波;另一类则由不同经圈模的Rossby波经相互作用后的耦合波。这两类波都具有不稳定性。文中讨论了耦合波的传播和不稳定的物理机制,并指出这类不稳定的热带耦合波,对研究ENSO事件中的某些现象有一定的参考意义。     

Derivation of a curve number and kinematic-wave based flood frequency distribution

Abstract

The physically-based flood frequency models use readily available rainfall data and catchment characteristics to derive the flood frequency distribution. In the present study, a new physically-based flood frequency distribution has been developed. This model uses bivariate exponential distribution for rainfall intensity and duration, and the Soil Conservation Service-Curve Number (SCS-CN) method for deriving the probability density function (pdf) of effective rainfall. The effective rainfall-runoff model is based on kinematic-wave theory. The results of application of this derived model to three Indian basins indicate that the model is a useful alternative for estimating flood flow quantiles at ungauged sites.     

热带大洋对纬向和经向风应力的联合响应

考虑了经向风应力和纬向风应力联合作用下热带大洋的响应问题.结果表明,只有一阶的经向风应力或具有辐合辐散的经向风应力才对最后的速度场和位势场造成影响.零阶的扰动温跃层和纬圈流受风应力的直接驱动和Kelvin波、Rossby短波的影响,而Rossby短波由经向风应力直接造成;二阶模则受风应力的直接驱动和Rossby短波的作用,同时经向风应力也产生了附加的Rossby短波.另外,在西边界处存在很强的暖水补充到赤道的现象,经向风应力有使暖水向赤道输送的作用,而西风应力使西边界处的暖水向东输送.     

The fracture characteristic of the 1989 Datong-Yanggao earthquake sequence

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拟合水工设计反应谱的人工地震波的生成与Huang变换校正

根据非平稳输入下建立的功率谱与均值反应谱之间的关系,合成基于水工设计反应谱的人工地震波,并对其幅值进行修正,降低了高频区误差作用.为了解决加速度时程积分后的速度、位移时程的零线漂移现象,利用Huang变换得到加速度时程的固有模态函数,这种最低频率固有模态函数分量通常情况下代表原始信号的趋势或均值;再对去掉均值后的加速度时程进行积分,得到的速度、位移时程不存在零线漂移问题.