汕头市历史地震影响烈度的分析

本文将所论地震事件视为随机事件。按全概率定理分析了地震对场地的地震动影响(A)和超越给定值的概率P:对地震烈度序列进行了极值统计分析,得到汕头市地震平均重现期及其对应的烈度值。     

中国3000年疫灾流行的时空特征及其影响因素

疫灾是人类灾害链网中的顶级灾害.利用历史疫灾史料,建立疫灾时间序列,使用历史断面分析、因子相关分析、时间序列分析等方法,对中国过去2720年疫灾流行的时空特征及其影响因素进行研究.结果 表明:①中国疫灾流行的频度和强度有长期上升趋势,温暖期形成疫灾低谷,寒冷期形成疫灾高峰.②中国疫灾流行总体以夏、秋季为主,但有阶段性差...     

“7·22”云南盐津地震房屋震害分析

本文根据地震现场的考查情况,介绍了2006年7月22日云南盐津5.1级地震的灾害概况,归纳和分析了灾区生土墙结构、石结构、钢筋混凝土框架结构和木构架结构房屋的震害特征及其破坏原因,并对我国村镇房屋的防震减灾研究提出了若干建议。     

Three‐dimensional modal pushover analysis of buildings subjected to two components of ground motion,including its evaluation for tall buildings

The modal pushover analysis (MPA) procedure, presently restricted to one horizontal component of ground motion, is extended to three‐dimensional analysis of buildings—symmetric or unsymmetric in plan—subjected to two horizontal components of ground motion, simultaneously. Also presented is a variant of this method, called the practical modal pushover analysis (PMPA) procedure, which estimates seismic demands directly from the earthquake response (or design) spectrum. Its accuracy in estimating seismic demands for very tall buildings is evaluated, demonstrating that for nonlinear systems this procedure is almost as accurate as the response spectrum analysis procedure is for linear systems. Thus, for practical applications, the PMPA procedure offers an attractive alternative whereby seismic demands can be estimated directly from the (elastic) design spectrum, thus avoiding the complications of selecting and scaling ground motions for nonlinear response history analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

An improved building detection approach using L-band POLSAR two-dimensional time-frequency decomposition over oriented built-up areas

The objective of this study is to efficiently extract detailed information about various man-made targets in oriented built-up areas using polarimetric synthetic aperture radar (POLSAR) images. This paper develops an improved approach for building detection by utilizing Two-Dimensional Time-Frequency (2-D TF) decomposition. This method performs outstandingly in distinguishing between man-made and natural targets based on the isotropic behaviors, frequency-sensitive responses, and scattering mechanisms of objects. The proposed method can preserve the spatial resolution and exploit the advantages of TF decomposition; specifically, the exact outlines of buildings can be effectively located, and more types of features (e.g., flat roofs, roads, and walls that are oblique to the radar illumination) can be distinguished from forests in complex built-up areas by 2-D TF decomposition. The coarser-resolution subaperture images that are produced in the azimuth direction, which correspond to different looking angles, are beneficial for detecting man-made structures with main scattering centers oriented at oblique angles with respect to the radar illumination. In the range direction, the obtained subaperture images, which correspond to various observation frequencies, can be helpful in distinguishing flat roofs and roads from forests. This method was successfully implemented to analyze both NASA/JPL L-band AIRSAR and L-band EMISAR data sets. The building detection results of the proposed method exhibit a significant improvement over those of other methods and reach an overall accuracy over 80%, with approximately 20% higher than the accuracies of K-means clustering and the entropy/alpha-Wishart classifier and approximately 10% higher than the accuracy of the support vector machine method. Moreover, building details can be precisely detected, obliquely oriented buildings can be identified, and the distinction between buildings and forests is significantly improved, as both visually and statistically indicated. This method is highly adaptable and has substantial application value.     

Bayesian estimation of seismic hazard for two sites in Switzerland

Seismic hazard analysis is based on data and models, which both are imprecise and uncertain. Especially the interpretation of historical information into earthquake parameters, e.g. earthquake size and location, yields ambiguous and imprecise data. Models based on probability distributions have been developed in order to quantify and represent these uncertainties. Nevertheless, the majority of the procedures applied in seismic hazard assessment do not take into account these uncertainties, nor do they show the variance of the results. Therefore, a procedure based on Bayesian statistics was developed to estimate return periods for different ground motion intensities (MSK scale).Bayesian techniques provide a mathematical model to estimate the distribution of random variables in presence of uncertainties. The developed method estimates the probability distribution of the number of occurrences in a Poisson process described by the parameter . The input data are the historical occurrences of intensities for a particular site, represented by a discrete probability distribution for each earthquake. The calculation of these historical occurrences requires a careful preparation of all input parameters, i.e. a modelling of their uncertainties. The obtained results show that the variance of the recurrence rate is smaller in regions with higher seismic activity than in less active regions. It can also be demonstrated that long return periods cannot be estimated with confidence, because the time period of observation is too short. This indicates that the long return periods obtained by seismic source methods only reflects the delineated seismic sources and the chosen earthquake size distribution law.     

诗歌中物候记录的基本特征及用于历史气候重建的处理方法

历史物候记录对过去气候变化研究弥足珍贵。诗歌作为历史文献的重要体裁之一,其中的历史物候记录已得到了一定程度的整编和利用。但对诗歌物候记录的特征和处理方法仍缺乏系统的梳理和探讨。本文首先介绍了诗歌中物候记录的内容、特征及其在季节指示和反映农时中的应用,发现诗歌中的物候记录主要包括动物物候、植物物候和周期性气象、水文现象等3种,并呈现出距今越近,经济、社会越发达,记录越多的时空特点。然后,从物候记录筛选、物种鉴别、物候事件发生时间识别、物候期确定等方面总结了历史气候研究中诗歌物候记录的处理方法：①从诗歌的创作背景、文学成分、地理环境分异规律和人为影响等几个方面进行筛选,以保证其中物候记录的有效性;②区分古今动、植物名差异,并将物种鉴定到种;③针对年、月、日缺记的不同情况,依据物候规律和背景资料确定物候事件的发生时间;④根据现代物候观测标准,对诗歌中的文字描述进行归类定级,确定所包含的物候期。以期为诗歌物候记录的提取及其在历史气候研究中的应用提供理论和方法上的借鉴。     

研究季风区历史时期湖泊环境演化的意义

本文首先讨论了历史时期季风区湖泊环境演化研究在古全球变化研究中的地位及其意义,着重强调人与自然相互作用研究以及进行定量研究是该领域的关键所在。综合中国近年来在湖泊沉积与古全球变化研究中取得的成果,提出在该领域研究的一些新的认识与亟待解决的问题。     

建筑物沉降观测技术方法探讨

随着城市建设的迅猛发展,城市规模越来越大,建筑物越来越高,由此带来的安全隐患越来越大,由于高层建筑一般采用桩基基础,且荷载较大,对高层建筑的内部基础和设备的位置关系有很高的精度要求,其施工安装阶段将给高层建筑本身及周边建筑群体带来复杂的形变影响。为了保障建筑物施工和运营的安全,就必须对其进行沉降观测。本文结合笔者多年的实际工作经验,并结合具体的实例,对高层建筑物沉降原因、沉降观测前的准备工作及沉降观测的实施过程和观测数据的处理方法等进行了论述,最后指出如何通过沉降观测技术准确地反映出高层建筑物的沉降情况。