0308号强热带风暴天鹅路径和降水分析   总被引：5，自引：1，他引：5  

许向春  郝丽清  翁小芳 《气象》2004,30(11):14-18

详细分析了0308号热带气旋天鹅在南海中部加强为强热带风暴后云系的演变以及对路径和降水产生的影响，结果表明：强对流云团的“吸附”作用是天鹅登陆后路径南折的主要原因；垂直速度场对热带气旋路径短期偏折方向有较好的预报指示意义，热带气旋有向强上升运动区偏折的趋势；中尺度暴雨出现在强对流云团中小涡旋的螺旋云带上或云顶亮温的梯度密集区与地面风向辐合区重叠处。  相似文献   

山西断陷带北部块体构造活动样式及强震构造背景   总被引：3，自引：0，他引：3       下载免费PDF全文

于慎谔 《地震学报》2004,26(4):379-386

应用地块构造几何学方法和原理，系统研究了山西断陷带北部构造区地块构造类型、结构和运动特征. 运用断块多米诺模型，通过断裂构造地貌分析对比，系统地讨论了断块变形、断陷盆地伸展运动特点，及其区域分布特征. 分析结果显示:① 以北西向断裂划分，由西向东分为西区段、中区段和东区段，相应的地壳伸展量分别为4.46 km, 2.80 km和1.86 km.。断块平均伸展量约为1 km. 计算结果与实际测量数据大致相同; ② 以恒山断块为界，山西断陷带北部构造区可分为南北两区， 两区地震活动水平不同，分别为M7和6M   相似文献   

Rhythmic Layering in the Apatite (-Magnetite) Deposit in the Fanshan Complex, North China   总被引：1，自引：0，他引：1  

Chun Cheng    Shihua Sun  Qian Mao 《Resource Geology》2004,54(2):167-175

Abstract. The Fanshan complex consists of three (First- to Third-) Phases of intrusion. The First-Phase Intrusive is composed of rhythmic layers. The Fanshan apatite (-magnetite) deposit is situated near the top of no. 6 rhythmic Unit of the First-Phase Intrusive. Two sketch maps were drawn through the deposit along no. 25 cross-cut on 425 mL and no. 1 crosscut on 491 mL in the Fanshan mine. Through this mapping, a small-scaled rhythmic layering (called sub-rhythmic layering) was newly found. The sub-rhythmic layering consists of five typical rocks: biotite clinopyroxenite, biotite rock, biotite-apatite rock, alternation biotite-apatite rock and apatite rock. The thickness of layers varies from four millimeters to several meters. Six units of sub-rhythmic layering were distinguished. Each unit consists of biotite clinopyroxenite (or biotite rock and biotite-apatite rock) layer at the bottom and apatite rock layer at the top.
Major element compositions of biotite and clinopyroxene were analyzed. The trends of Mg/(Mg+Fe*+Mn) atomic ratio (Fe*: total iron) of biotite and clinopyroxene indicate that the magma evolved markedly from relatively magnesian bottom layer to less magnesian top layer in each sub-rhythmic unit. A general trend, however, through the whole sub-rhythmic layering sequence shows that the both minerals become relatively magnesian upwards. The hypotheses of liquid immiscibili-ty, gravitational settling and magma mixing are against with the results obtained in the present study. This study suggests that the apatite (-magnetite) deposit is formed through fractional crystallization process.  相似文献   

Modelling Two-Phase Incompressible Flow in Porous Media Using Mixed Hybrid and Discontinuous Finite Elements     

D. Nayagum  G. Schäfer  R. Mosé 《Computational Geosciences》2004,8(1):49-73

In this paper, we present a numerical model for simulating two-phase (oil–water and air–water) incompressible and immiscible flow in porous media. The mathematical model which is based on a fractional flow formulation is formed of two nonlinear partial differential equations: a mean pressure equation and a water saturation equation. These two equations can be solved in a sequential manner. Two numerical methods are used to discretize the equations of the two-phase flow model: mixed hybrid finite elements are used to treat the pressure equation, h-based Richards' equation and the diffusion term in the saturation equation, the advection term in the saturation equation is treated with the discontinuous finite elements. We propose a better way to calculate the nonlinear coefficients contained in our equations on each element of the discretized domain. In heterogeneous porous media, the saturation becomes discontinuous at the interface between two porous media. We show in this paper how to use the capillary pressure–saturation relationship in order to handle the saturation jump in the mixed hybrid finite element method. The two-phase flow simulator is verified against analytical solutions for some flow problems treated by other authors.  相似文献   

Analysis of the reliability and resolution of the earthquake source history inferred from waveforms, taking the Chi-Chi earthquake as an example   总被引：1，自引：0，他引：1  

Shiyong Zhou  Kojiro Irikura  Xiaofei Chen 《Geophysical Journal International》2004,157(3):1217-1232

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地质特征轨迹的出露概率研究     

周小文 《岩土力学》2004,25(Z2):89-92

将地质特征的发展轨迹视为Brown运动.基于Brown运动理论,在裂隙穿越矩形区域概率公式的基础上,推导了单条裂隙轨迹和多条裂隙轨迹穿越任意区域的概率公式,并用算例进行了演算,从结果可知,如果通过一些实际工程的考察,确定出合理的轨迹运动参数,则用Brown运动有可能较好地模拟岩体裂隙(或其它地质特征轨迹)的运动规律.利用得到的概率公式,研究了矩形区域(边长为a,b)内裂隙的穿越概率与归一化距离b/a之间的关系.结果表明,如果地质特征轨迹符合Brown运动,则在0≤b/a≤1范围内,穿越概率随b/a的增加急剧降低;当b/a>1时,随着b/a的增加,概率减小比较缓慢.  相似文献   

Comparing the adequacy of alternative ground motion intensity measures for the estimation of structural responses     

Paolo Giovenale  C. Allin Cornell  Luis Esteva 《地震工程与结构动力学》2004,33(8):951-979

Practical methods for the probability‐based seismic assessment of structures make use of estimates of demands produced by earthquakes of different intensities. The uncertainties associated with these estimates are highly dependent on the variable adopted as the intensity measure (IM, e.g., PGA, spectral acceleration, etc.). This generates the need to compare the efficiency of an originally adopted IMwith that of a new candidate. This implies comparing the dispersion of the demand measure (DM, e.g., maximum interstorey drift ratio, ductility demand, etc.) conditional to each of the two IMs. In order to obtain the demand estimates in a conventional way, a full set of dynamic response analyses should be performed for each IM under scrutiny, i.e., multiple records scaled at several fixed values of each IM. The procedure developed here serves to accelerate this comparison avoiding the effort required to evaluate the dynamic responses of the structure for all the ground motion time histories considered every time that a new IM is adopted. For this purpose, use is made of available results of analyses performed for a different (i.e., the original) IM. Two methods are proposed: the direct method involves performing a regression of the results obtained from the original analyses, taking the candidate IM as the independent variable. The indirect method involves rebuilding the probability density function of the DM given a defined value of the candidate IM by means of the total probability theorem, using the results of the original analyses and certain data relating the two IMs. The proposed methods have been tested by application to several SDOF systems with different periods and different cyclic‐response backbone curves. The conditions affecting their approximation are explored, and some criteria to improve them are identified. The procedure can also be used to determine the optimum value of a parameter to be used in a parameter‐based IM. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Simulation of the seismic performance of the Bolu Viaduct subjected to near‐fault ground motions     

S. W. Park  H. Ghasemi  J. Shen  P. G. Somerville  W. P. Yen  M. Yashinsky 《地震工程与结构动力学》2004,33(13):1249-1270

The seismic performance of the Bolu Viaduct in the Duzce, Turkey, earthquake of November 1999 was studied via a non‐linear, time‐history analysis of a multi‐degree of freedom model. The viaduct had a seismic isolation system consisting of yielding‐steel energy dissipation units and sliding pot bearings. The Duzce earthquake caused a surface rupture across the viaduct, which resulted in excessive superstructure movement and widespread failure of the seismic isolation system. The effect of the rupture was modeled by a static, differential ground displacement in the fault‐parallel direction across the rupture. The ground motions used in the analysis contain common near‐fault features including a directivity pulse in the fault‐normal direction and a fling step in the fault‐parallel direction. The analysis used a finite element package capable of modeling the mechanical behavior of the seismic isolation system and focused on the structural response of a 10‐span module of the viaduct. This analysis showed that the displacement of the superstructure relative to the piers exceeded the capacity of the bearings at an early stage of the earthquake, causing damage to the bearings as well as to the energy dissipation units. The analysis also indicated that shear keys, both longitudinal and transverse, played a critical role in preventing collapse of the deck spans. Published in 2004 by John Wiley & Sons, Ltd.  相似文献   

A study on characteristics of tectonic block motion and tectonic setting of strong earthquakes in northern part of the Shanxi fault depression zone     

于慎谔 《地震学报(英文版)》2004,17(4):417-425

Introduction Shanxi fault depression zone (SFDZ) is one of important Cenozoic fault basin zones and strong earthquake belts in Chinese mainland. Its northern part has aroused wide research interests due to the complicated tectonics and high activity of strong earthquakes there. Early researches on this depression zone were carried out since 60s of last century (DENG, et al, 1973; DENG, YOU, 1985; LU, DING, 1985; XU, 1990; XU, et al, 1996, 2002). In 90s of last century, the geologica…  相似文献   

A series solution for surface motion ampli-fication due to underground group cavities: Incident P waves     

梁建文  张浩  Vincent W Lee 《地震学报(英文版)》2004,17(3):296-307

Introduction In recent years some big cities in China commonly build subways in central urban areas to improve crowded surface transportation, and the subways usually are large-scale group cavities composed by two parallel cavities. Construction of large-scale group cavities will certainly affect the design ground motion near the cavities, and further affect seismic safety of the existing build-ings nearby. So it is of significance to estimate this effect on seismic design of the buildings. H…  相似文献