班公湖-怒江带中段构造性质探讨

西起班公湖,向东大体沿黑(河)阿(里)公路,经改则、尼玛、东巧—那曲,再向东,大体与怒江上游相连接的一条超基性岩带逐渐引起人们的注意。经几次考察,已初步被认为是一条重要的构造界线,甚至可与南面的雅鲁藏布江带相对比。然而,由于过去工作的较少,对该构造带的研究尚很不够。     

A two-layer model of soil hydrology

A two-layer model of soil hydrology is developed for applications where only limited computer time and complexity are allowed. Volumetric soil water is computed in a thin upper layer for use in calculation of surface evaporation. Storage of water is computed for an underlying deeper layer.In an effort to identify the influence of significant asymmetric truncation errors in the two-layer model, this model is compared with the 100-level model of Boersma et al. (1983). Comparisons are made for modelled soils with clay, loam and sand properties for various time dependencies of potential evaporation and precipitation. Truncation errors in the resulting two-layer model appear to be modest, at least compared to errors associated with difficulty in estimation of the hydraulic diffusivity and its strong dependence on soil water content.Minimization of the influence of truncation errors requires: (1) choosing the upper layer to be sufficiently thin, (2) allowing the soil water gradient to control surface evaporation directly and (3) using suitable numerical implementation of the evaluation of internal soil water flux.

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Résumé On propose un modèle d'hydrologie du sol à deux couches, spécialement élaboré pour des applications où le temps de calcul et la complexité doivent être aussi réduits que possible. Le contenu en eau du sol dans la mince couche de surface est utilisé pour évaluer l'évaporation, tandis que la réserve en eau est calculée pour la couche profonde, beaucoup plus épaisse.Afin d'estimer les erreurs de troncature et leurs effets dans le modèle à deux couches, des comparaisons sont faites avec le modèle à 100 niveaux de Boersma et al. (1983). Ces comparaisons portent sur des sols de natures variées (argile, terres végétales et sable) et incluent divers taux d'évaporation potentielle et de précipitation. Les effets des erreurs de troncature dans le modèle à 2 couches semblent peu importants par rapport à ceux associés à la mauvaise connaissance de la diffusivité hydraulique et de sa dépendance à l'égard du contenu en eau du sol.La réduction de l'influence de ces erreurs de troncature nécessite: (1) le choix d'une couche supérieure suffisamment fine; (2) le contrôle direct de l'évaporation vers l'atmosphère à partir de la répartition verticale du contenu en eau du sol; (3) l'utilisation d'une procédure particulière pour évaluer le flux d'eau entre les deux couches du sol.

     

Study on the characteristics of earthquake’s impact on cities

Firstly, the impact of historical earthquakes on 34 China province-level capital cities is evaluated by using historical earthquake catalog. The distribution of affected intensity shows, about 53% of cities have even not been affected by earthquake intensity VI, and 44% of cities have been hit by earthquake intensity VII to IX. For most of the cities, occurrence frequency of affected intensity VI is usually higher than that of affected intensity larger than VI, and the value of affected intensity with maximal occurrence frequency may be very different among cities. So both the maximal affected intensity and the affected intensity with maximal occurrence frequency should be taken into account when the prevention seismic intensity needs to be determined. Secondly, considering the incompleteness of records of historical earthquakes, a method of earthquake catalog computer simulation is introduced to study the features of affected intensity of big cities. 69 county-level cities of Fujian Province are selected to be statistical objects. The statistical result shows, for different risk levels the seismic intensity changes greatly among cities, the seismic intensity of 2% probability of exceedance in 50 years can be regarded as the characteristic affected intensity of city, and can be the basis of determining the city special earthquake prevention level and a proper indicator of future earthquake’s impact on cities. Foundation item: A Public Benefit Foundation of the Ministry of Science and Technology of China. Contribution No. 04FE1005, Institute of Geophysics, China Earthquake Administration.     

城镇土地定级估价信息系统的设计与实现

在分析城镇土地定级、基准地价评估、宗地评估、基准地价更新中所涉及的各种信息及其处理方法的基础上，从系统设计原则、功能模块设计、数据库设计、系统类设计等几个方面对面向对象的城镇土地定级估价信息系统的设计进行了详细的阐述。     

Evaluation of vertical seismic response for a large‐scale beam‐supported aqueduct

By the theories of potential flow and structural vibration, the formulae for evaluating the ‘wet’ (with water) frequencies and mode shapes of the beam‐supported aqueduct are derived through a simplified fluid‐structure interaction analysis. The time‐history formulae of structural responses to the vertical seismic excitation are obtained. Applying the response‐spectrum principle, the equivalent vertical earthquake load exerted on the beam and the corresponding effects are also derived. Several illustrative examples are conducted. The analytical results show that: (i) The ‘wet’ frequencies of the structure are lower than the corresponding ‘dry’ (without water) frequencies due to the participating water mass, but the ‘wet’ mode shapes are identical to the corresponding ‘dry’ ones. (ii) The water mass plays an important role in the vertical seismic response, which varies with the different geological sites. For the different seismic inputs, the deeper the water is, the greater are the structural responses. (iii) The vertical seismic effects on the beam are generally not too small to be neglected and should be considered in the structural designs of a beam‐supported aqueduct. Copyright © 2002 John Wiley & Sons, Ltd.     

System identification of linear structures based on Hilbert–Huang spectral analysis. Part 1: normal modes

Based on the Hilbert–Huang spectral analysis, a method is proposed to identify multi‐degree‐of‐freedom (MDOF) linear systems using measured free vibration time histories. For MDOF systems, the normal modes have been assumed to exist. In this method, the measured response data, which are polluted by noises, are first decomposed into modal responses using the empirical mode decomposition (EMD) approach with intermittency criteria. Then, the Hilbert transform is applied to each modal response to obtain the instantaneous amplitude and phase angle time histories. A linear least‐square fit procedure is proposed to identify the natural frequency and damping ratio from the instantaneous amplitude and phase angle for each modal response. Based on a single measurement of the free vibration time history at one appropriate location, natural frequencies and damping ratios can be identified. When the responses at all degrees of freedom are measured, the mode shapes and the physical mass, damping and stiffness matrices of the structure can be determined. The applications of the proposed method are illustrated using three linear systems with different dynamic characteristics. Numerical simulation results demonstrate that the proposed system identification method yields quite accurate results, and it offers a new and effective tool for the system identification of linear structures in which normal modes exist. Copyright © 2003 John Wiley & Sons, Ltd.     

2003年6月5日青岛崂山4.1级震群概述

2003年6月5日青岛崂山区发生4．1级震群。这次震群是青岛历史上少有的，青岛市普遍有感，造成了一定的社会影响。文章从地震影响、地质构造、历史及现代地震、序列特点及性质判定、地震应急等方面概述了本次震群。     

城市活断层的抗干扰高分辨率浅层地震勘探研究

首先，简要介绍了城市活断层探测的意义及世界各国开展城市活断层探测的基本情况。在简述抗干扰高分辨率浅层地震勘探基本原理的基础上，重点论述了城市活断层的抗干扰高分辨率浅层地震勘探的震源激发、数字地震仪性能、接收方式与接收条件、观测系统以及数据处理与资料解释等。研究表明，对于城市活断层的抗干扰高分辨率浅层地震勘探，在数据采集环节应采用具有线性或非线性变频扫描功能的可控震源和与其相匹配的地震仪器，以及小道间距、小偏移距、多接收道、短排列和高频检波器接收的工作方法；在数据处理与解释环节，要重视折射静校正技术、噪声压制技术、高精度速度分析技术、子波压缩技术、子波零相位化技术和叠前偏移技术等的应用。最后，给出了城市活断层的抗干扰高分辨率浅层地震勘探实例。     

贵州赫章土法炼锌导致的重金属积累

贵州省赫章县的土法炼锌不仅导致植被的破坏,而且使附近土壤和溪流沉积物中重金属有不同程度的积累,土壤中w(Pb)达到37.24×10~(-6)～30100×10~(6),w(Zn)为162.23×10~(-6)～31625×10~(-6),w(Cd)为0.50×10~(-6)～113×10~(-6),大大超过了当地的土壤背景值;沉积物中w(Pb)达到325.00×10~(-6)～21850×10~(-6),w(Zn)为1250.00×10~(-6)～30425×10~(-6),w(Cd)为25×10~(-6)～97×10~(-6)。土壤和沉积物中Pb、Zn含量与Fe_2O_3有极显著的正相关性;土壤中重金属Pb、Zn含量与Al_2O_3有极显著的正相关性,而沉积物中Pb、Zn含量与Al_2O_3则没有相关性。土壤和沉积物中铁矿物(铁氧化物和氢氧化物)对重金属的强烈固定作用。连续提取法对化学形态研究表明,Pb、Zn在土壤中主要表现为铁锰氧化物结合态与残渣态,而在沉积物中则主要为碳酸盐结合态、残渣态和铁锰氧化物结合态。土壤中可交换态Pb、Zn所占的比例很小,但其绝对含量变化较大,w(Pb)从最低2.75×10~(-6)到最高310.41×10~(-6),w(Zn)4.94×10~(-6)～321.10×10~(-6)。沉积物中w(Pb)7.42×10~(-6)～98.91×10~(-6);w(Zn)9.97×10~(-6)～72.67×10~(-6)。土壤中重金属Pb、Zn的有效性程度明显高于溪流沉积物,对生态环境的潜在危害更大。     

两种典型河谷应力场应力分布特征对比分析

地应力作为工程建设的基础地质条件之一，已得到较高重视，许多大型工程都开展了地应力的测试分析研究。本文选取两种典型的深切峡谷，运用三维有限元软件模拟河流下切、河谷形成过程，得到了现今的峡谷应力场。在此基础上，详细分析各自应力场的空间分布特征，并将两者进行了对比分析。得出高山峡谷应力场分布的一般规律。