1992年福建南日岛地震及其前兆初探

研究了1992年福建省南日岛5.2级地震序列特征,认为这是一次孤立型地震,震前存在多学科的前兆异常,异常群体特征具有长、中、短临阶段性及形态复杂性.地震学异常持续时间长,前兆学科短临异常突出,可能是少震区地震前兆的特点。     

CDP mapping in tilted transversely isotropic (TTI) media. Part I: Method and effectiveness

Transverse isotropy with a tilted axis of symmetry (TTI) causes image distortion if isotropic models are assumed during data processing. A simple anisotropic migration approach needs long computational times and is sensitive to the signal-to-noise ratio. This paper presents an efficient, general approach to common-depth-point (CDP) mapping to image the subsurface in TTI media from qP-wave seismic data by adding anisotropic and dip parameters to the velocity model. The method consists of three steps: (i) calculating traveltimes and positions of the CDP points; (ii) determining CDP trajectories; (iii) CDP imaging. A crucial step is the rapid computation of traveltimes and raypaths in the TTI media, which is achieved by the Fermat method, specially adapted for anisotropic layered media. The algorithm can image the subsurface of a given model quickly and accurately, and is suitable for application to a bending reflector. The effectiveness of the method is demonstrated by comparing the raypaths, the traveltimes and the results of CDP mapping, when assuming isotropic media, transversely isotropic media with a vertical axis of symmetry (TIV), and TTI media.     

Application of extended distinct element method with lattice model to collapse analysis of RC bridges

This paper proposes a simple lattice model for collapse analysis of RC bridges subjected to earthquakes by using the extended distinct element method (EDEM). In the model, a concrete element consists of lumped masses connected to one another by springs, and a reinforcement bar is represented by a discrete model or an integrated model. The proposed lattice model is simple but its parameters are reasonably defined. It has fewer element nodes and connecting springs, which will be of benefit by shortening the CPU time. The processes to determine the initial stiffness of concrete and steel springs, the parameters of the constitutive model and the fracture criteria for springs are described. A re‐contact spring model is also proposed to simulate the re‐contact of the concrete after fracture of springs; and a general grid searching method is used to decrease the CPU time for judging re‐contact after fracture. The lattice model is assessed by numerical simulations and experiments. As an application, a damaged single‐column pier subjected to the Kobe Earthquake in 1995 is analysed by EDEM with the proposed model. The simulation results indicate that the proposed model predicts well qualitatively the collapse process of RC bridges. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis of the influence of Taihu Lake and the urban heat islands on the local circulation in the Yangtze Delta

The influences of human activities on regional climate and weather are tremendous. The re-gional temperature and the distributing of wind field are influenced, whereas the precipitation in-tensity and the spatial and temporal distribution of the precipita…     

美国城市搜索与救援体系的组成及运作模式概述

美国城市搜索与救援体系是世界上最完善的体系之一，多年来在城市救灾和应对突发事件中发挥了重要作用，减轻了生命和财产的损失。文章概述了美国城市搜索与救援体系的组成、任务、运作原则和管理机构及支援机构。     

Disector自动测量及其三维可视化系统

本文介绍了自行开发的解决Diseetor应用问题的计算机图像处理软件系统及关键技术、算法。本系统能依照Disector原理对多层组织细胞的电镜及光镜图像中的目标进行正确的分割,各层之间图像的人工交互及自动配准。针对每个目标的上下层关系实现目标的Disector自动计数及参数计算,并对每个目标进行体数据的提取和三维重建显示,通过切片级表面重建出曲面表面,再借助OpenGL的显示功能把曲面显示出来。使用Disector分析系统对多种粒子(细胞等)进行三维分析,可以简化寻找新出现粒子的过程,克服切片采集过程中的形变,在统计分析之后,立体地观察粒子结构,能够使操作者从繁琐的手工操作中解脱出来。自动统计新出现的粒子。文中同时还给出了用该系统对小白鼠神经细胞个数的Disector分析,肾小球个数统计分析和三维重建显示实例。     

武定地震序列剪应力场的时空分布特征

根据陈培善和Ｄuda提出的具有3模型的谱衰减模式,利用云南武定M ＝6.5地震序列的近场数字化记录资料,研究了近场地面运动峰值位移dm、峰值加速度am参数与环境应力t0值的依赖性．一个新的考虑是假定峰值参数与介质犙的相关性,并由此导出了用３种地面运动峰值参数测定环境应力t0值的３个关系式．用这些关系式计算了武定地震序列的环境应力t0值．结果表明,３个关系式计算的t0 值基本一致,绝大多数地震的平均t0值在5.0～35MPa的范围,属高应力值地震序列;高应力值被限制在紧靠主震震中附近的较小范围内,环境应力值的等值线的精细结构分布与强余震密切相关．对t0值的时空特征分析表明,该地震序列是在特定的地震构造交汇部位和高应力背景下发生的地震破裂过程．     

大同遥测地震台网小震群活动与大同-阳高中强地震预报讨论

根据大同遥测地震台网记录到的小震群资料，用组合模式理论［１］对本区的小震群时空演化规律进行了分析研究。结果表明，对于１９８９年１０月１８日在本区发生的大同—阳高５．８级地震，利用震前小震群资料得出的预报震中与实际震中有较好的一致性。另外，通过震群与外因相关性的分析，对发震时间的预报也取得了较好的效果     

陆水水库的浮游生物及营养类型

报道了１９９１￣１９９５年对面积为１６９３ｈｍ＾２的黑龙滩水库渔业利用优化模式研究的结果,主要内容有：水生生物种类组成和现存量调查、浮游植物初级生产力测定、渔获物统计和鱼产力估算;水体理化性状和水位变化对鱼产量和浮游生物群落结构的影响,网箱养殖鲤、草鱼的高产试验结果;多功能水库生态系统的渔业利用优化模式初步探讨。经三年努力,水库鱼产量由６２２ｔ上升到１２５５．１ｔ,平均单产７５０ｋｇ／ｈｍ＾２。为     

腾冲火山区剪切波和尾波衰减初步研究

用云南腾冲火山地区观测的地震数字化记录进行了尾波和剪切波的衰减测量。用AkiandChouet和Sato单次散射模型获得 5 2秒和 18秒流逝时间尾波的品质因子分别为Qc (f) =5 7×f- 0 94和Qc (f) =2 6×f- 0 95 ,表明地壳上部和地壳上地幔的地震波衰减频率变化率一致。两者均未显示出活火山地区尾波衰减的异常特征。尾波掠过空间椭球的平均半轴 ,前者约为 80km ,大大超出了腾冲火山分布的地理范围 ,后者约为 30km ,在腾冲火山分布的地理范围之内。用尾波规一双台S波振幅比法进一步缩小所用地震波掠过的空间 ,最后获得了S波随频率的衰减有类似于前人报导的活火山地区尾波频率衰减的特征 :相对于低频 (1 5～ 6Hz) ,高频 (6～2 0Hz)的Q- 1s 变化很小。从地表位置看 ,腾冲最年青的全新世的马鞍山和老龟坡火山就在S波掠过范围内 ,打鹰山火山也在近旁。这一结果表明在这三座火山体之下存在低速高衰减体。火山或处于休眠状态 ,或在消亡过程之中。