Quantitative relationship between pollen and vegetation in northern China

205 surface pollen samples from different communities in Northern China were analyzed to understand the quantitative relationship between pollen and its original vegetation. Pollen analysis and vegetation investigation show that the pollen assemblages differ a lot in different vegetation regions. Arboreal pollen account for more than 30% in temperate broad-deciduous forests region. In temperate steppe regions, herb pollen percentages are more than 90%, where Artemisia and Chenopodiaceae are domi- nant pollen types with Artemisia percentages more than 30%. In temperate desert, Chenopodiaceae pollen percentages are more than Artemisia, where ferns are rare. Cyperaceae pollen percentages are more than 20% in sub-alpine or cold meadows. The relations between pollen percentages and vegeta- tion cover indicate that most arboreal pollen shows a close relationship with parent plant covers, most shrubby pollen types have more or less correlations, but most herbs do not show clear correlations. For arboreal pollen types, Picea pollen shows the closest correlation with spruce trees coverage, then is Quercus and Carpinus. Betula, Larix and Juglans have also high correlation coefficients with their plants coverage, but Betula pollen is of overrepresented pollen type and more than 40% in birch forest, while Larix and Juglans pollen is underrepresented and pollen percentages are more than 10% in Larix or Juglans pure forests. Pinus is of overrepresented pollen type, and pollen percentages have some relations with plants cover. Pine forest might present when Pinus pollen percentages are more than 30%. The relations between Ulmus and Populus pollen percentages and vegetation cover are not close, where they are mixed with other arbors, they cannot be recorded easily, but if their pollen percentages are more than 1%, Ulmus or Populus trees should exist. For shrubby pollen types, the correlation be- tween Vitex pollen percentages and vegetation cover is the highest, then is Corylus, Tamariaceae and Nitraria, and their pollen percentages are less than 1% where original plant are absent. Caragana and Spiraea pollen percentages have some relations with vegetation cover. The relations between pollen percentages and vegetation cover are not clear for Rosaceae and Saxifragaceae. For herb pollen types, Cyperaceae pollen has the closest correlation with vegetation cover, where pollen percentages are more than 20% when Cyperaceae are constructive or dominant species in vegetation, and pollen per- centages are less than 5% where Cyperaceae are not constructive or dominant species (cover less than 30%). Artemisia and Chenopodiaceae pollen percentages mainly have close relations with ecological regions. The relations between pollen percentages and cover are not clear for Gramineae, Legumi- nosae and Compositae.     

Study on the relationship between geothermal exploitation and seismic activity in Xi’an region

Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi’an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi’an region belong to the solitary-type and they spread outside Xi’an city where the wells are concentrated but no earthquake happens. The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi’an because of its specially geological condition. Foundation item: Project sponsored by the Landslide Office of Shaanxi Province and Society of Disaster Reduction of Shaanxi Province.     

River flow mass exponents with fractal channel networks and rainfall

An important problem in hydrologic science is understanding how river flow is influenced by rainfall properties and drainage basin characteristics. In this paper we consider one approach, the use of mass exponents, in examining the relation of river flow to rainfall and the channel network, which provides the primary conduit for transport of water to the outlet in a large basin. Mass exponents, which characterize the power-law behavior of moments as a function of scale, are ideally suited for defining scaling behavior of processes that exhibit a high degree of variability or intermittency. The main result in this paper is an expression relating the mass exponent of flow resulting from an instantaneous burst of rainfall to the mass exponents of spatial rainfall and that of the network width function. Spatial rainfall is modeled as a random multiplicative cascade and the channel network as a recursive replacement tree; these fractal models reproduce certain types of self-similar behavior seen in actual rainfall and networks. It is shown that under these modeling assumptions the scaling behavior of flow mirrors that of rainfall if rainfall is highly variable in space, and on the other hand flow mirrors the structure of the network if rainfall is not so highly variable.     

Inelastic spectra for displacement-based seismic design

In recognition of the emergence of displacement-based seismic design as a potentially more rational approach than force-based techniques, this paper addresses derivation of inelastic displacement spectra and associated topics. A well-constrained earthquake strong-motion dataset is used to derive inelastic displacement spectra, displacement reduction factors and ductility–damping relationships. These are in a format amenable for use in design and assessment of structures with a wide range of response characteristics.     

新疆北部降水的气候分布特片及其对ENSO的响应

分析研究了新疆北部地区近50年（1951-2000年）全年各月降水的气候分布特征和各季降水的年际变化规律，重点揭示了北疆多雨季节（4-7月）及其各月降水量对赤道东太平洋的海温SST和南方涛动指数SOI的显著响应关系，并用前期SST和SOI作为预报因子，建立了北疆地区雨季水量的预报方程。该方程可用于北疆地区雨季降水量的长期预报。     

关于震磁关系"综合解释"层次的初步分析

从系统分析的角度出发,提出以磁报震的实质是综合预报,而综合预报的基础则是综合解释。作为一个认识系统,以磁报震的综合解释主要由４个层次（４个要素）组成,即地磁场异常变化（层次Ｉ）,构造环境及应力场的变化（层次Ⅱ）,系统相关要素的变化（层次Ⅲ）,外部环境要素的变化等（层次Ⅳ）。以磁报震不应简单归结为完全以地磁异常变化为基点的地震预报,而应是由多要素（层次）组成的有机分析系统,即在以层次Ｉ为核心的认识基     

上海环球金融中心大厦整体结构振动台试验设计

同济大学土木工程防灾国家重点实验室对上海环球金融中心大厦进行了整体结构模型的振动台试验.该大厦101层,结构高度492m,拟建成为世界上结构主体最高的建筑物.本文详细介绍了大厦结构体系、振动台试验模型材料的选取、动力相似关系的确定以及试验方案的设计.针对超高层整体结构小比例模型施工困难的特点,提出了模型的简化方法,并利用ANSYS对简化模型进行了计算,计算结果表明模型简化对结构自振特性和地震反应影响很小,验证了简化方法的可行性.本文提供的模型和试验的设计思路对今后有关的试验工作有一定的借鉴作用.     

影响地震活动性因素的非均匀细胞自动机模拟研究

基于细胞自动机模型,构建了由81×81个细胞单元组成非均匀二维单断层介质样本,研究了断层结构细观非均匀性以及相关模型参数变化对模拟输出结果和强度分布特征的影响。研究结果表明：结构非均匀性是影响地震活动性的控制性参量,随着非均匀程度的增强,地震事件数量增多,震级分布变得越来越均匀,破裂演化模式由相对“脆性”向“塑性”变化;介质结构的初始条件和应力加载的随机性对地震活动演化过程基本不产生影响。此外,应力降分配系数减小使b值主体线性段向大震级延伸;随着局部摩擦损耗系数增大,模拟地震事件的数量有所增加,大震级事件数量和震级衰减增强,b值主体线性区间变窄,使断层的变形破坏方式由相对“脆性”向“塑性”变化。这些对我们理解孕震过程的复杂性是有帮助的。     

内蒙古达里诺尔湖流域地表水和地下水环境同位素特征及补给关系

为了探明达里诺尔湖流域地表水与地下水的氢(H)、氧(O)同位素的变化特征及相互补给关系,于2013年对达里诺尔湖及其周围的河水、井水、泉水中H、O同位素进行了取样分析,并结合总溶解性固体悬浮物(TDS)和区域水文地质对达里诺尔湖流域的补给关系进行讨论分析.结果表明:1)河水、泉水、井水中H、O同位素的值基本落在全球雨水线上,湖水H、O同位素落在全球雨水线的右下方,说明河水、井水、泉水没有发生蒸发分馏,而湖水则发生较大程度的蒸发分馏;对达里诺尔湖流域地表水与地下水的H、O同位素进行回归模拟,得出该区域的蒸发趋势线方程:δD=4.8753δ18O-20.139(n=32,R2=0.9968).蒸发线表明,这些水样具有相同水源的特征.2)从实地考察发现,泉水补给河水,泉水和河水补给湖水,同时井水、泉水和河水有相似的δD、δ18O和TDS值,且不随季节变化而变化,推断达里诺尔湖附近地下水补给湖水;区域水文地质条件亦证明达里诺尔湖周边地下水补给湖水.