海城7．3级地震前地震波动力学特征量的异常变化

本文给出对海城７．３级地震前地震波动力学特征量变化的一些最新研究结果。所研究的地震波包括体波（Ｐ，Ｓ波）、尾波和短周期地脉动三类。特征量有：体波与地脉动的波形时间线性度和空间线性度，平均半周期，频谱的峰值频率、拐角频率、相对频带宽度、相对频谱峰值、高频段的谱线斜率绝对值；尾波的时间熵、振幅比、持续时间、观测与计算持续时间差及其二阶差分、Ｑ＿ｃ值、反映介质混浊度与震源特性的系数ａ＿ｃ等。所得结果表明，三类地震波的上述动力学特征量大都在震前一至半年左右出现、有的在６－１０天乃至一天以内出现过不同形态的阶段性异常变化，因而可看作海城地震的中短期和临震的地震波前兆异常指标。     

Surface conductivity in rocks: a review

Electrical properties of rocks depend on composition (i.e. bulk properties of the constituents), micro structure (i.e. geometrical arrangement of the constituents) and interfacial effects. We consider here a rock as a three component system — grains, pores, and interfaces — in order to account for the observed behaviour. We review first the main results relative to DC. conductivity. Surface conductivity effects show up clearly in the case of shaly formations or at low salinities. Although Archies' law (1942) and Waxman and Smits model (1968) are widely used, a more physically based model is that of Johnson and Sen (1988). We review also the variable frequency conductivity (complex conductivity) data and models. The important effect in that case is the enhancement of the dielectric constant at low frequencies (Knight and Nur, 1987) which can be interpreted as a geometrical effect although electrochemical interactions may also play an important role at low frequencies, depending on the rock type.     

西藏日喀则群昂仁组时代问题新资料

昂仁组是一套复理石和类复理石沉积,含晚白垩世土伦期的菊石Mammites^[1,2],但因未发现直接的上覆地层和化石稀少而不能肯定是否还包括晚于土伦期或至早第三纪的沉积^[1,3]。1980年,笔者在昂仁、萨噶一带的昂仁组中采到瓣鳃、腹足化石;我局区调队在仲巴县错江顶一带,发现连续沉积于昂仁组之上,整合于下第三系之下一套含Masstrichtian期菊石(Sphenodiscus)的杂色地层。本文报道这一发现和对昂仁组时代问题的认识(图1)。     

我国核电站选址的区域稳定性研究

核能是重要的能源之一。利用核能发电在世界能源构成中占有愈来愈重要的地位。 修建核电站,要求严格的安全和环境条件,必须绝对保证核电站在各种可能遭遇的自然和人为事件情况下,均不致发生造成放射性物质外泄的事故。因此,除了要求核电站建筑物和各种装置本身安全可靠并拥有周密而充分的安全措施外,特别要求在选择厂址时,必须充分查明和预测各种可能遭受的自然灾害。在各种能危及核电站安全的自然灾害中,与工程地质直接有关的问题有许多方面,本文仅就核电站选址中,厂址地区的区域稳定问题作一简要探讨。     

Simultaneous iterative time-domain sparse deconvolution to teleseismic receiver functions

In this paper, we present a new approach to estimate high-resolution teleseismic receiver functions using a simultaneous iterative time-domain sparse deconvolution. This technique improves the deconvolution by using reweighting strategies based on a Cauchy criterion. The resulting sparse receiver functions enhance the primary converted phases and its multiples. To test its functionality and reliability, we applied this approach to synthetic experiments and to seismic data recorded at station ABU, in Japan. Our results show Ps conversions at approximately 4.0 s after the primary P onset, which are consistent with other seismological studies in this area. We demonstrate that the sparse deconvolution is a simple, efficient technique in computing receiver functions with significantly greater resolution than conventional approaches.     

Potential impacts of aerosol–land–atmosphere interactions on the Indian monsoonal rainfall characteristics

Aerosols can affect the cloud-radiation feedback and the precipitation over the Indian monsoon region. In this paper, we propose that another pathway by which aerosols can modulate the multi-scale aspect of Indian monsoons is by altering the land–atmosphere interactions. The nonlinear feedbacks due to aerosol/diffuse radiation on coupled interactions over the Indian monsoon region are studied by: (1) reviewing recent field measurements and modeling studies, (2) analyzing the MODIS and AERONET aerosol optical depth datasets, and (3) diagnosing the results from sensitivity experiments using a mesoscale modeling system. The results of this study suggest that the large magnitude of aerosol loading and its impact on land–atmosphere interactions can significantly influence the mesoscale monsoonal characteristics in the Indo-Ganges Basin.     

A simplified approach for vulnerability assessment in moderate-to-low seismic hazard regions: application to Grenoble (France)

Due to the moderate seismic risks in France, the building vulnerability assessment methods developed for high seismic risk countries could not easily be used here because of their cost and the low-risk perception among the public and officials. A light vulnerability assessment method is proposed and tested in Grenoble (France), based on classes and scores provided in the GNDT method but simplified in terms of visual screening and number of structural parameters used. Compared to the RiskUE method, the damage obtained by our approach shows that 90% of buildings have residuals smaller than 0.2, i.e. one grade of the EMS98 damage scale. A large scale survey is devised and conducted among the inhabitants of Grenoble in order to collect the main structural parameters. By comparing the results from the survey to the historical urbanization of Grenoble and to expert surveys performed in two urban districts, the information useful for the light method of vulnerability assessment can be rapidly collected by non-experts reducing substantially the estimate cost. The average damage is then computed using the GNDT formula considering the probable intensities which could be observed in Grenoble (VII and VIII). The average damage reaches 0.4 in the oldest part of Grenoble mainly made of masonry buildings and 0.2 in reinforced concrete suburbs where reinforced concrete predominates. The results are a relative vulnerability assessment that provides useful initial information for the urban zones of Grenoble where the vulnerability is higher. This method can be used to classify the seismic vulnerability in wide seismic-prone regions to a fair degree of accuracy and at low cost.     

“9.18”川西北暴雨过程的数值预报与试验

利用成都区域中心ETA坐标模式，对2001年9月18－21日发生在四川盆地西北部的暴雨过程作数值预报试验，显示出对大暴雨过程的预报能力。模式预报对此降水过程雨区的移动、稳定、减弱趋势有较好的反应，但降水强度预报偏弱，且落区有偏差。数值试验揭示了降水前期对流层中、低层的西南、东南气流对降水的重要作用，而北方冷空气的强弱对此影响不明显。     

一次MCS过程的卫星云图和数值模拟分析

本文应用卫星云图与数值模拟结果对2000年6月2日发生的一次影响江苏的江淮气旋暴雨过程进行研究分析，阐述了这次暴雨过程表现的MCS基本特征。分析表明：MCS的形成可以由几个中β尺度对流云或对流带开始，在特定的环境场中汇合成合并；在其发展过程中必须维持湿度平流，低层到中层有暖平流，骨强偏南风急流伸向形成区，同时在其东北方向有一支高空西风急流相耦合；低层的辐合、整层凝结潜热的释放、垂直运动的增强、高层的辐散引起的正反馈机制是MCS发展的动因。     

应用K指数和TOT指数作江苏中期降水预报的试验

用国家气象中心的T63和T106中期数值预报产品，计算所划定区域的K指数和TOT指数作为预报因子，并统计与江苏省9个代表站降水的相关。用逐步回归方法建立了江苏省4－7月第4－6天的PP降水预报方程36个、MOS降水预报方程108个，多级判别临界值144组。在此基础上经统计制作江苏省降水概率预报。