Improved site-dependent statistical relationships of VS and resonant frequency versus bedrock depth in Japan

Journal of Seismology - Combining both processing techniques of horizontal-to-vertical spectral ratio (HVSR) and surface-to-borehole spectral ratio (SBR), using the KiK-net and K-NET database in...     

非线性有效压力计算

根据Robin关于有效压力的定义,结合Bernabé推测的孔隙压pp和围压pc图中的渗透率等值线变化形态,提出了一种新的非线性渗透率有效压力计算方法.用新方法和Bernabé切线有效压力计算方法对以往和本次实验的12块低渗岩芯的实验数据进行了处理分析,结果表明新方法和Bernabé方法计算得到的有效压力在pp和pc图中的渗透率等值线为直线时才相等.当等值线为曲线时,二者计算得到的有效压力不一样.新方法计算出的测试点的有效压力与渗透率的关系表现出更好的一一对应关系.为了进一步验证文章计算有效压力方法的有效性,用指数和乘幂两种函数分别拟合二种有效压力计算方法得到的有效压力与渗透率之间的关系.拟合结果表明,新方法得到的有效压力与渗透率的拟合效果优于用Bernabé方法计算得到的有效压力与渗透率拟合效果.     

Numerical study of non-linear storm-surges

Summary The problem of storm-surges is investigated in a rectangular basin, setting up a numerical hydrodynamical model using the shallow-water equations. The forcing exerted by the atmosphere is given in the idealized form of a constant wind blowing over a section of the basin. The case in which the window of wind is moving is considered and for a basin that has the same dimensions of the Adriatic Sea. The conditions that give the maximum surge at one edge of the basin are investigated.

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Riassunto Il problema relativo alle storm-surges viene studiato in un bacino rettangolare, costru endo un modello idrodinamico numerico ed usando le equazioni relative ad acqua poco profonda. Lo stress esercitato dall'atmosfera è dato nella forma idealizzata di un vento costante che soffia sopra una sezione del bacino. Si considera il caso in cui la finestra di vento è in moto e per un bacino che ha le medesime dimensioni del mare Adriatico. Si studiano le condizioni che provocano il massimo dell'innalzamento ad un estremo del bacino.

     

Determination of first mode ground period and site-dependent design response spectrum for Taiwan High Speed Rail

The objective of this paper is to identify the first mode ground period T_g, at each interesting site along Taiwan High Speed Rail (THSR) route, and further, to determine the site-dependent design response spectrum for particular sites with T_g larger than 1 s. In this paper, a linear model of shear wave propagating in a multi-layered half-space is developed to identify the first mode ground period T_g of an interesting site on the basis of the field bore hole data. Furthermore, for each one of the strong ground motion observation stations within the Chiayi-Tainan area, the first mode ground period T_g was identified by either coda waves or pre-event ambient vibrations from the seismograms. In addition, the site-specific parameter C_v in defining the normalized response spectrum was also determined based on the observed strong ground motions at the specified observation station, and hence the empirical function between T_g and C_v can be regressed for this interesting area. Therefore, for a particular site along THSR route within the Chiayi-Tainan area, the site-specific parameter C_v can be determined from the regressed empirical function by the identified first mode ground period T_g, and further, used to develop the site-dependent design response spectrum.     

Estimating inelastic response spectra from elastic spectra

Inelastic displacement response spectra are determined for a broad class of single-degree-of-freedom hysteretic structures. Based on these spectra, effective linear period and damping parameters are defined as a function of ductility. A simple empirical formula is derived which may be used to estimate the mid-period range inelastic response spectrum of a general hysteretic structure given the linear response spectrum of the excitation. The estimates obtained from this formula are compared with those obtained by the Newmark-Hall method, the substitute–structure method and the ATC–3 tentative procedure. It is found that the empirical formula not only gives good estimates of the average behaviour of the inelastic spectrum, but also reproduces some of the details of the spectrum.     

Stochastic linearization of multi-degree-of-freedom non-linear systems

An equivalent linearization technique to obtain the response of non-linear multi-degree-of-freedom dynamic systems to stationary gaussian excitations is developed. The non-linearities are assumed to be single-valued functions of accelerations, velocities and displacements. Using a property of gaussian vector processes, the closed forms of the coefficients of the equivalent linear system are obtained by the direct application of partial differentiation and expectation operators to the non-linear terms. It is shown that when the non-linearities possess potentials, the linear system has symmetric coefficient matrices. A geometrical interpretation of the linear coefficients, in connection with the original non-linearities, is presented. The accuracy is investigated by means of examples.     

非线性反演方法的新进展

线性方法在许多具体反演问题中遇到困难的情况下，人们提出了非线性方法，同时，计算技术的发展为非线性方法的应用提供了基础。最近几年，人们对非线性方法又进行了改进和发展，例如：Vasco(1993)提出了集合推论的思想；Sambridge(1995)基于Voronoi单元的思想，提出了自然相邻对不规则数据参数化和插值的方法，相邻算法正是基于以上思想和理论，以及其他非线性方法的实践而提出的一种新的非线性反演方法。     

Equivalent linearization of non-linear soil-structure systems

The concept of equivalent linearization, in which the actual nonlinear structure is replaced by an equivalent linear single-degree-of-freedom (SDOF) system, is extended for soil-structure systems in order to consider the simultaneous effects of soil-structure interaction (SSI) and inelastic behavior of the structure on equivalent linear parameters (ELP). This is carried out by searching over a two-dimensional equivalent period–equivalent damping space for the best pair, which can predict the earthquake response of the inelastic soil-structure system with sufficient accuracy. The super-structure is modeled as an elasto-plastic SDOF system whereas the soil beneath the structure is considered as a homogeneous half-space and is replaced by a discrete model. An extensive parametric study is carried out for a wide range of soil-structure systems subjected to a suite of 59 ground motions. The effect of SSI on ELP is studied through introducing a set of non-dimensional key parameters, which define the soil-structure system. It is shown that ELP of soil-structure systems result from a trade-off between SSI effect and nonlinear behavior of the structure. The contribution of each of these two factors depends on the characteristics of the soil-structure system which, in turn, are defined by the introduced non-dimensional key parameters. Moreover, the reliability of the predicted response of soil-structure systems and its sensitivity to deviation from optimal ELP is studied in detail, which sheds light on the consequences of using improper pairs of ELP for interacting systems in the framework of performance-based design of structures. Copyright © 2012 John Wiley & Sons, Ltd.     

Probabilistic Seismic Hazard Assessment for Japan

A probabilistic seismic hazard assessment was performed for the Japanese islands and surrounding areas. Seismic hazard parameters characteristic of the seismic history of the regions were obtained. The probability of occurrence of a large M ≥ 7 earthquake within a 10- and 50-year period was also calculated. Regions of very high levels of hazard occur where the Pacific, Phillipine and Eurasian Plates meet. High probabilities of occurrence of a large M ≥ 7 earthquake within a 10- and 50-year period occur within the region where the Pacific Plate subducts with the Eurasian Plate.     

Probabilistic Regularities in Unfavorable Hydrochemical Phenomena

The balance equation for a substance washed out in a river basin is analyzed under the assumption that the runoff of this substance and its reserves in the watershed are directly proportional. The proportionality factor is perturbed by a random component, which accounts for the effect of atmospheric precipitation. The balance equation is transformed into a stochastic differential equation with a multiplicative white noise, which is used to construct a Fokker-Plank equation for the probability density of chemical flow. A stationary solution containing a power function is found for this equation. Because of the proportionality of the concentration and chemical flow, the concentration distribution also obeys the power law. Statistical treatment of empirical data on some water quality characteristics and water flow showed that the power law adequately describes the probability of unfavorable hydrochemical events. The parameters of this law for turbidity, color index, permanganate oxidability, and ammonia concentration are evaluated.__________Translated from Vodnye Resursy, Vol. 32, No. 4, 2005, pp. 452–458.Original Russian Text Copyright © 2005 by Dolgonosov, Korchagin.     

Probabilistic seismic hazard analysis in Nepal

The seismic ground motion hazard for Nepal has been estimated using a probabilistic approach. A catalogue of earthquakes has been compiled for Nepal and the surrounding region （latitude 26% N and 31.7% N and longitude 79° E and 90° E） from 1255 to 2011. The distribution of catalogued earthquakes, together with available geological and tectonic information were used to delineate twenty-three seismic source seismic source information and probabilistic earthquake hazard prediction relationship, peak ground accelerations （PGAs） have zones in Nepal and the surrounding region. By using the parameters in conjunction with a selected ground motion been calculated at bedrock level with 63%, 10%, and 2% probability of exceedance in 50 years. The estimated PGA values are in the range of 0.07-0.16 g, 0.21 0.62 g, and 0.38-1.1 g for 63%, 10%, and 2% probability of exceedance in 50 years, respectively. The resulting ground motion maps show different characteristics of PGA distribution, i.e., high hazard in the far-western and eastern sections, and low hazard in southern Nepal. The quantified PGA values at bedrock level provide information for microzonation studies in different parts of the country.     

Probabilistic sinkhole modelling for hazard assessment

A method for quantitatively assessing sinkhole susceptibility (spatial probability) and hazard (spatio‐temporal probability) has been developed and independently tested in a 50 km² sector of the Ebro Valley evaporite karst. Three genetic types of sinkholes have been mapped in the floodplain and a terrace surface: 947 small cover‐collapse sinkholes (type 1, terrace), large collapse sinkholes (type 2, floodplain) and large subsidence depressions (type 3, floodplain). The type 1 sinkhole inventory includes two temporal populations: 447 sinkholes formed before 24 November 2005, and 500 between that date and 2 November 2006. Sinkhole susceptibility models have been elaborated analysing the statistical relationships between the sinkholes of the 2005 inventory and a set of potential conditioning factors. The independent evaluation (validation) of the susceptibility models by means of several strategies (random, sequentially excluded, and temporal) has allowed us to select the most significant variables for each sinkhole type and assess quantitatively the quality of models; which are reasonable for the three sinkhole types. Validation has also provided information on the contribution of specific variables and the effect of changing their accuracy to the prediction capability of models. Susceptibility models for type 3 sinkholes have been validated satisfactorily with the 2006 sinkhole inventory (temporal validation). The best susceptibility model has been transformed into a hazard map considering the frequency of sinkholes that occurred in each susceptibility class between 2005 and 2006, as well as their average size. The susceptibility and hazard models obtained could be used as an objective basis for the application of mitigation measures, either of preventive or corrective nature. Copyright © 2008 John Wiley & Sons, Ltd.     

Probabilistic seismic hazard assessment for Thailand

A set of probabilistic seismic hazard maps for Thailand has been derived using procedures developed for the latest US National Seismic Hazard Maps. In contrast to earlier hazard maps for this region, which are mostly computed using seismic source zone delineations, the presented maps are based on the combination of smoothed gridded seismicity, crustal-fault, and subduction source models. Thailand’s composite earthquake catalogue is revisited and expanded, covering a study area limited by 0°–30°N Latitude and 88°–110°E Longitude and the instrumental period from 1912 to 2007. The long-term slip rates and estimates of earthquake size from paleoseismological studies are incorporated through a crustal fault source model. Furthermore, the subduction source model is used to model the megathrust Sunda subduction zones, with variable characteristics along the strike of the faults. Epistemic uncertainty is taken into consideration by the logic tree framework incorporating basic quantities, such as different source modelling, maximum cut-off magnitudes and ground motion prediction equations. The ground motion hazard map is presented over a 10 km grid in terms of peak ground acceleration and spectral acceleration at 0.2, 1.0, and 2.0 undamped natural periods and a 5% critical damping ratio for 10 and 2% probabilities of exceedance in 50 years. The presented maps give expected ground motions that are based on more extensive data sources than applied in the development of previous maps. The main findings are that northern and western Thailand are subjected to the highest hazard. The largest contributors to short- and long-period ground motion hazard in the Bangkok region are from the nearby active faults and Sunda subduction zones, respectively.     

人口损失的概率预测模型

本文在论述用死亡度来描述强震破坏合理性的基础上，利用与目前震害资料现状相一致的概率模型和相关资料，计算得到了中国各分区在未来不同的时间发生不同死亡度的概率曲线；并以动态系统模型为基础，处理了历史的人口损失资料。最后，对两种资料的结果进行了分析和讨论。     

Probabilistic solution of floodplain inundation equation

Uncertainty in bed roughness is a dominant factor in providing a sufficiently accurate simulation of floodplain flows. This study describes a method to compute the transition probability density distribution of time-varying water elevations where the evolutionary process is based on a conventional one-dimensional storage cell model with governing stochastic differential equation. By including the random inputs (or noise terms) of bed roughness and initial water depth, time-dependent and spatially varying probability density function of the water surface leads to a Fokker–Planck equation. The model’s performance is evaluated by applying it to shallow water flow with a horizontal bed. Sensitivity of model predictions to variations in the bed friction parameters is shown. By comparing the result of the proposed method with that of conventional Monte Carlo simulation, the advantage of the former as a method for density function prediction is confirmed.     

Probabilistic Visibility Forecasting Using Neural Networks

Statistical methods are widely applied in visibility forecasting. In this article, further improvements are explored by extending the standard probabilistic neural network approach. The first approach is to use several models to obtain an averaged output, instead of just selecting the overall best one, while the second approach is to use deterministic neural networks to make input variables for the probabilistic neural network. These approaches are extensively tested at two sites and seen to improve upon the standard approach, although the improvements for one of the sites were not found to be of statistical significance.     

A non-linear regularized constrained impedance inversion

Inversion for seismic impedance is an inherently complicated problem. It is ill‐posed and band‐limited. Thus the inversion results are non‐unique and the process is unstable. Combining regularization with constraints using sonic and density log data can help to reduce these problems. To achieve this, we developed an inversion method by constructing a new objective function, including edge‐preserving regularization and a soft constraint based on a Markov random field. The method includes the selection of proper initial values of the regularization parameters by a statistical method, and it adaptively adjusts the regularization parameters by the maximum likelihood method in a fast simulated‐annealing procedure to improve the inversion result and the convergence speed. Moreover, the method uses two kinds of regularization parameter: a ‘weighting factor’λ and a ‘scaling parameter’δ. We tested the method on both synthetic and field data examples. Tests on 2D synthetic data indicate that the inversion results, especially the aspects of the discontinuity, are significantly different for different regularization functions. The initial values of the regularization parameters are either too large or too small to avoid either an unstable or an over‐smoothed result, and they affect the convergence speed. When selecting the initial values of λ, the type of the regularization function should be considered. The results obtained by constant regularization parameters are smoother than those obtained by adaptively adjusting the regularization parameters. The inversion results of the field data provide more detailed information about the layers, and they match the impedance curves calculated from the well logs at the three wells, over most portions of the curves.