2002年6月13日重庆区域大暴雨分析

通过对重庆西部“6 1 3”区域大暴雨的分析 ,发现此次天气过程是一次典型的高原涡与西南涡耦合 ,结合地面弱冷空气条件下产生的 ,同时对ECMWF和T2 1 3数值预报产品进行了简要的分析 ,发现ECMWF和T2 1 3的形势预报能力都比较好 ,但T2 1 3的部分物理量要素和降水量预报能力还有待提高。     

鹤壁市雷暴短时监测和临近预报流程

利用卫星云图数字化资料、雷达探测和雷电定位探测资料对雷暴天气进行短时监测 ,并与多种短期预报方法集成 ,建立时效为 3～ 6小时的雷暴临近预报流程 ,从而达到预测强对流天气之目的。     

Soil moisture potential and water content in the unsaturated zone within the arid Ejina Oasis in Northwest China

Three soil profiles were selected in the Ejina Oasis, northwest China, to determine water content profiles and evolution of soil moisture potentials in the unsaturated zone within the arid area. The total soil moisture potentials have been monitored for about 3 months in 2001 at different depths in the soil profiles. The occurrence and movement of water in the unsaturated zone was analyzed using the zero flux plane (ZFP) method. It is shown that convergent ZFPs and divergent ZFPs may occur at depths between 0.5 and 3.0 m, and that the depth of the ZFPs was controlled by the root zone of plants growing on the land surface. Profiles of the total soil moisture potentials were observed to be coincident with those of the water contents at the three experimental sites. The total soil moisture potential showed a slight increasing trend and the ZFPs tend to vanish from summer to winter as the water extraction by roots decreased. Evapotranspiration through vegetation has an important bearing on the water content and the total potential in the unsaturated zone.     

Focal mechanism dependence of static stress triggering of earthquakes

We perform a global statistical investigation into the problem of Coulomb stress triggering of earthquakes by using the Harvard CMT catalogue of shallow earthquakes from 1976 to 2001. We consider ‘earthquake pairs’, i.e., pairs of successive earthquakes occurring near each other with similar focal mechanisms, and address the problem of whether or not the change of the Coulomb failure stress (CFS) produced by the first earthquake of the pair ‘encourages’ the occurrence of the second one. An interesting feature is that such a Coulomb stress-triggering phenomenon has an apparent focal mechanism dependence: for thrust earthquakes, a more evident triggering effect can be observed.     

Late-Stage Ductile Deformation in Xiongdian-Suhe HP Metamorphic Unit, North-Western Dabie Shan, Central China

New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shun, central China. The finegrained symplectic amphibolite-facies assemblage and coronal structure enveloping eclogite-facies garnet,omphacite and phengite etc., representing strain-free decompression and retrogressive metamorphism,are considered as the main criteria to distinguish between the early-stage deformation under HP metamorphic conditions related to the continental deep subduction and collision, and the late-stage deformation under amphibolite to greenschist-facies conditions occurred in the post-eclogite exhumation processes.Two late-stages of widely developed, sequential ductile deformations D3 and D4, are recognized on the basis of penetrative fabrics and mineral aggregates in the Xiongdian-Suhe HP metamorphic unit, which shows clear, regionally, consistent overprinting relationships. D3 fabrics are best preserved in the Suhe tract of low post-D3 deformation intensity and characterized by steeply dipping layered mylonitic amphibolites associated with doubly vergent folds. They are attributed to a phase of tectonism linked to the initial exhumation of the HP rocks and involved crustal shortening with the development of upright structures and the widespread emplacement of garnet-bearing granites and felsic dikes. D4 structures are attributed to the main episode of ductile extension (D^24) with a gently dipping foliation to the north and common intrafolial, recumbent folds in the Xiongdian tract, followed by normal sense top-to-the northductile shearing (D^24) along an important tectonic boundary, the so-called Majiawa-Hexiwan fault (MHF), the westward continuation of the Balifan-Mozitan-Xiaotian fault (BMXF) of the northern Dabie Shan. It is indicated that the two stages of ductile deformation observed in the Xiongdian-Suhe HP metamorphic unit, reflecting the post-eclogite compressional or extrusion wedge formation, the subhorizontal ductile extension and crustal thinning as well as the top-to-the north shearing along the high-angle ductile shear zones responsible for exhumation of the HP unit as a coherent slab, are consistent with those recognized in the Dabie-Sulu UHP and HP metamorphic belts, suggesting that they were closely associated in time and space. The Xiongdian-Suhe HP metamorphic unit thus forms part of the Triassic(250-230 Ma) collision orogenic belt, and can not connect with the South Altun-North Qaidam-North Qinline UHP metamorphic belt formed durin~ the Early Paleozoic (500-400Ma).     

巧用CASIO fx-4800P计算器测设线路复合曲线

应用地面点与线路中线相对关系的统一数学模型，使用CASIO fx-4800P程序型计算器编制的适合野外测设线路各种复合曲线(包括直线、缓和曲线、圆曲线的任意组合)的实用程序。     

常州市数字化测绘工程及GIS建库概述

数字化地形图和地籍图是城市规划、建设和管理及国土资源管理的重要基础资料．也是开展数字城市和信息化建设的最基础平台。通过对系统总体结构的设计和应用成果介绍，分析了目前基础地理数据生产、管理和应用的现状，介绍了基于GIS的常州市数字化地形图、地籍图测绘工程总体目标及基础地理信息系统总体设计．并概述了整个数字化测绘工程的实施过程和特点。     

Application of Characteristics of Seismogenic Structures in the Determination of Parameter of Potential Seismic Source Areas

INTRODUCTIONThe method of probabilistic seismic risk analysis was proposed by Cornell in1968(Cornell,1968).After more than30years development,it has become the main method for seismic riskassessment of engineering sites and seismic zonation,and has been u…     

Analytic expressions for the velocity sensitivity to the elastic moduli for the most general anisotropic media

For non‐linear kinematic inversion of elastic anisotropy parameters and related investigations of the sensitivity of seismic data, the derivatives of the wavespeed (phase velocity and group velocity) with respect to the individual elastic moduli are required. This paper presents two analytic methods, called the eigenvalue and eigenvector methods, to compute the derivatives of the wavespeeds for wave propagation in a general anisotropic medium, which may be defined by up to 21 density‐normalized elastic moduli. The first method employs a simple and compact form of the eigenvalue (phase velocity) and a general form of the group velocity, and directly yields general expressions of the derivatives for the three wave modes (qP, qS₁, qS₂). The second method applies simple eigenvector solutions of the three wave modes and leads to other general forms of the derivatives. These analytic formulae show that the derivatives are, in general, functions of the 21 elastic moduli as well as the wave propagation direction, and they reflect the sensitivity of the wavespeeds to the individual elastic moduli. Meanwhile, we give results of numerical investigations with some examples for particular simplified forms of anisotropy. They show that the eigenvalue method is suitable for the qP‐, qS₁‐ and qS₂‐wave computations and mitigates the singularity problem for the two quasi‐shear waves. The eigenvector method is preferable to the eigenvalue method for the group velocity and the derivative of the phase velocity because it involves simpler expressions and independent computations, but for the derivative of the group velocity the derivative of the eigenvector is required. Both methods tackle the singularity problem and are applicable to any degree of seismic anisotropy for all three wave modes.     

当前国际水文学科技术领域的研究方向

根据联合国有关机构发布的公报和世界各国近年来的学术研究情况，整理出了近期水文学科在地表水、地下水、水质、水资源系统、大气～土壤～植被、大陆侵蚀、冰雪、遥感技术和示踪技术等领域的热门研究课题，在一定程度上反映了当前国际上水文学科的研究和发展方向，对国内同行有一定的参考价值。