汶川地震中建筑震害衰减特征及抗震性能分析

通过对汶川地震中170个调查点的震害指数进行统计分析,得到了从Ⅵ度到Ⅺ度中各个烈度区内的平均震害指数值和方差,结果表明在Ⅶ到X度区平均震害指数与烈度表基本相符,分析了Ⅵ度区和Ⅺ区内平均震害指数偏高和偏低的原因,指出前者主要因为调查点分布的原因,而后者则可能还受到该烈度区大小划分的影响.在断层距50 km内震害指数高、离...     

2020年1月19日新疆伽师MS6.4地震烈度分布及房屋震害特征

以2020年1月19日伽师M S6.4地震现场烈度调查结果为基础,综合余震分布、发震构造及仪器烈度值等研究成果,确定了本次地震的烈度分布。此次地震极震区烈度为Ⅷ度(8度),Ⅵ度(6度)区及以上总面积为7599 km 2。分析各个烈度区内不同结构房屋的震害,结果表明,震害较重房屋主要是由于这些房屋年久失修,施工质量不高,缺乏必要的抗震措施等自身原因造成的,其中没有抗震措施的砖木结构房屋是震害主体。随着新疆地区农村房屋的抗震性能提高,在以后的地震烈度调查中,需要现场调查人员依据不同结构房屋的破坏等级及平均震害指数等参数综合判定调查点的烈度值,在没有明显震害的低烈度区,仪器烈度值将会成为烈度图绘制的重要依据。     

四川康定6.3级地震灾害分布特点及结构震害简析

康定县地处我国四川西北部,藏族人口约占70%,康定地区抗震设防烈度为IX度。该地区有大量的藏式片石房屋、穿斗木结构,同时,有砌体房屋和框架(剪)房屋。在四川康定6.3级地震中不同结构类型房屋破坏程度差异巨大。通过对震区3个区域17个居民点的调查,本文统计了震区不同结构类型房屋的比例及分布,并对各种结构类型建筑的构造方式、造价、震害特点以及平均震害指数进行调查和统计分析。结果表明,藏式居民因地理条件所限就地取材,多采用片石和木构架混合承重的片石结构的抗震性能较差,在不同烈度区都有程度不同的震害。穿斗木结构、设防砌体结构和框架(剪)结构在此次地震中表现出了良好的抗震性能。本文在分析不同建筑震害特点的同时对今后藏式房屋的建造方式给出了初步建议。     

不同烈度区农村自建砖砌体房屋震害特征研究

农村自建砖砌体房屋通常没有正规的设计和施工导致该类房屋抗震性能较差。文中以汶川8.0级地震为例,在不同烈度区选择具有代表性地区的农村自建砖砌体房屋为研究对象,分析了该类型房屋不同烈度区的震害特征。通过使用数量化术语的震害描述,对在不同烈度区的农村自建砖砌体房屋的墙体、楼板屋盖、附属结构的破坏进行了震害分析,得到了地震作用下仅考虑结构振动破坏时该类型房屋的破坏特征。最后也给出了降低农村自建砖砌体房屋震害的一些建议。     

甘肃省农村各种结构类型房屋的地震破坏机理

地震造成房屋倒塌是我国农村地区的主要震害和人员伤亡重大的直接原因。本文基于对甘肃省农村民房的调查结果,按不同结构对农村房屋进行了分类,分述了各种结构类型房屋的地震破坏机理。对今后农村房屋的改造与新建具有一定的借鉴意义。     

西北地区农村民房现状及抗震技术研究

在对西北地区农村民房实地调研的基础上,根据承重结构、建筑材料和工艺的不同,将其划归为生土墙体承重房屋、砖砌墙体承重房屋、木构架承重房屋和混合承重房屋.研究表明.不同类型房屋分布具有明显的区域性和年代特征,抗震性能差异较大,但均存在不同程度的地震安全问题;提高西北地区农村民房的抗震能力,需要加快实施农居地震安全工程,加快...     

辽宁彰武4.8级地震的烈度与震害

1988年2月25日13时59分辽宁彰武发生Ms:4.8级的地震,宏观震中位于彰武县马尾村(42°15′N、122°31′E)震中烈度为Ⅵ度。本文叙述了这次地震的烈度分布与震害。这次地震震害总的特点是房屋破坏不严重,但有裂缝的房屋在Ⅴ度和Ⅵ度区内广泛分布,震害有一定的隐蔽性。     

2020年云南巧家5.0级地震烈度评定及房屋震害特征

2020年5月18日巧家县发生5.0级地震,结合震区背景信息和现场调查,详细阐述此次地震烈度分布和房屋震害特征,并计算各类结构房屋的震害指数和破坏比。调查发现,本次地震的最高烈度为Ⅵ度,长轴呈NW向,与灾区地震地质构造背景、仪器烈度分布具有较好的一致性。对比分析本次地震与昭通地区、云南其他地区近年来大小相近的历史地震Ⅵ度区震害指数,结果表明,本次地震房屋震害指数相较于昭通其他地区明显偏低,但比云南其他地区偏高。分析认为,近年来巧家县各项房屋改造工程切实提高了当地房屋抗震水平,但仍需加强房屋改造建设,尤其是加快推进老旧房屋拆除及新房建设工作,进一步提升房屋抗震能力。     

续发性地震震害损失评估方法探讨

通过伽师地震震害损失评估的实践总结,认为对续发性地震的损失评估,尤其对量大面广的建筑物的损失评估采用震害损失率相减的方法,其结果与前面的地震损失率具有可比性,通过对不同评估方法的比较,认为震害损失率相减法快速,准确,易于操作,给出了新疆地区不同烈度下土木结构房屋的震害损失率,其取值范围为：Ⅺ度区为７０－４６％;Ⅷ度区为４５－２９％;Ⅶ度区为２８％－１３％;Ⅵ度区为１２－６％,Ⅴ度区为５％以下。     

甘肃夏河MS5.7地震烈度评定及震害特征分析

在预评估地震影响范围的基础上,通过对2019年10月28日夏河5.7级地震进行现场震害调查、灾情分析,绘制出地震烈度图并得出此次地震的震害特征。结果表明:此次地震最高烈度为Ⅶ度(7度),该区面积为193 km~2,Ⅵ度(6度)区面积为1 398 km~2;震区范围内,房屋类型大多数为木构架承重的土木结构,极震区多数房屋外层土墙开裂、坍塌较为严重,但承重木构架出现轻微倾斜和局部破坏现象,无完全倒塌房屋;震区内大多数寺庙基本完好,个别寺庙部分墙体有轻微裂缝;沿着断裂带展布方向,灾情呈现带状分布特征;震区半山腰上的建筑物灾情较为严重,山体放大效应和边坡效应明显。根据对地震灾害特征的分析,提出了增强房屋抗震性能、合理选址,加强防震减灾知识宣传教育等建议。     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.