拟建哈—佳铁路工程地震安评抗断参数研究——以依兰-伊通断裂为例

在对依兰-伊通断裂通河段晚第四纪活动参数获取的基础上,对该断裂的几何学特征和晚第四纪活动特征及有关拟建铁路地震安全的设防参数进行了探讨.研究结果表明,依兰-伊通断裂通河段总体走向N30-40°E,由3条断层组成,中支最新活动时代为全新世.该断裂未来发生7级地震时的水平位移量可能达2.2m左右,垂直位错量约为1.1m左右.该断裂全新世以来的活动性质表现为右旋走滑为主,兼具逆冲活动.根据探槽结果和野外地震地质调查得出断裂垂直位错约（1.0±0.2）m,右旋位错量约为（2.7±0.1）m,（1730-30）aB.P.以来的垂直滑动速率和水平滑动速率分别约为（0.57±0.11）mrn/a和（1.57±0.06）mm/a.未来100年内若遭遇地震,其最大水平位错量约2.87m,垂直位错值为1.04m.断层影响带宽度约为8m.该研究结果为拟建哈—佳铁路工程可能遭受的断层影响和抗震设防提供了一定的数据基础,也为地震安评中线状工程的抗断评价问题提供了一定的参考.     

RZB型深井宽频带地形变综合观测系统的垂向应变测量单元

目前钻孔应变观测一般为水平应变,使用无限岩石平板中的钻孔应力集中模型,可反演出水平应力场分布及变化.如果在此基础上加上垂向应力测量,就可反演出三维应力场分布.本文介绍的RZB型深井宽频带地形变综合观测系统的垂向应变测量单元,外钢筒为波纹管结构,并通过螺旋刻丝、热处理等技术,其垂向等效弹性模量比耦合水泥低一个数量级,同时垂向应变钢筒的水平向等效弹性模量高于垂向弹性模量一个数量级.垂向应变探头的力学结构可以被形象地看成是一个螺旋柱形弹簧,其轴向极易产生弹性形变,而水平向的硬度却得到了极大的加强,因此可在竖井中较为准确地测量轴向应变.     

发展钻孔应变观测的战略构想

钻孔应变观测正在成为一种与测震和GPS相提并论的地壳形变观测。曾经处于领先地位的我国钻孔应力一应变观测的发展需要回顾历史,面对现实,借鉴国外,放眼长远。建立比测基地、实验场和完善国家前兆监测网,三位一体,应该成为发展我国钻孔应变观测的基本方针。     

Landscape pattern evolution processes of alpine wetlands and their driving factors in the Zoige Plateau of China

Zoige Plateau wetlands are located in the northeastern corner of the Qinghai-Tibet Plateau.The landscape pattern evolution processes in the Zoige Plateau and their driving factors were identified by analyzing the dynamic changes in landscape modification and conversion and their dynamic rates of alpine wetlands over the past four decades.The results showed that the landscape conversion between wetlands and non-wetlands mainly occurred during the period from 1966 to 1986.The marsh wetland area converted from lake and river wetlands was larger because of swamping compared to other wetland landscapes.Meanwhile,the larger area of marsh wetlands was also converted to lake wetlands more than other types of wetlands.The modification processes mainly occurred among natural wetland landscapes in the first three periods.Obvious conversions were observed between wetland and nonwetland landscapes(i.e.,forestland,grassland,and other landscapes) in the Zoige Plateau.These natural wetland landscapes such as river,lake and marsh wetlands showed a net loss over the past four decades,whereas artificial wetland landscapes(i.e.,paddy field and reservoir and pond wetlands) showed a net decrease.The annual dynamic rate of the whole wetland landscape was 0.72%,in which the annual dynamic rate of river wetlands was the highest,followed by lake wetlands,while marsh wetlands had the lowest dynamic rate.The integrated landscape dynamic rate showed a decreasing trend in the first three periods.The changes in wetland landscape patterns were comprehensively controlled by natural factors and human activities,especially human activities play an important role in changing wetland landscape patterns.     

A generalized limit equilibrium method for the solution of active earth pressure on a retaining wall

In this paper, a generalized limit equilibrium method of solving the active earth pressure problem behind a retaining wall is proposed. Differing from other limit equilibrium methods, an arbitrary slip surface shape without any assumptions of pre-defined shapes is needed in the current framework, which is verified to find the most probable failure slip surface. Based on the current computational framework, numerical comparisons with experiment, discrete element method and other methods are carried out. In addition, the influences of the inclination of the wall, the soil cohesion, the angle of the internal friction of the soil, the slope inclination of the backfill soil on the critical pressure coefficient of the soil, the point of application of the resultant earth pressure and the shape of the slip surface are also carefully investigated. The results demonstrate that limit equilibrium solution from predefined slip plane assumption, including Coulomb solution, is a special case of current computational framework. It is well illustrated that the current method is feasible to evaluate the characteristics of earth pressure problem.     

华北地区地震环境噪声特征研究

利用华北流动地震台阵观测的垂直分向连续波形数据, 通过计算功率谱密度和相应的概率密度函数, 对华北地区地震环境噪声特征进行了分析研究. 结果表明, 东部平原和沉积盆地2 Hz以上的高频环境噪声水平与全球新高噪声模型（NHNM）相近, 周期3——18 s的平均噪声水平低于NHNM和新低噪声模型（NLNM）的平均值; 山区及西部高原的高频噪声水平明显低于NHNM, 周期1——18 s的噪声水平大多明显低于NHNM和NLNM的平均值; 不同区域18 s以上周期的噪声水平差异相对较小. 流动地震台阵部分台站的环境噪声存在明显的昼夜变化, 个别台站噪声水平明显高于周边台站, 表明这些台站受人类活动干扰较大. 不同台站的噪声水平分析表明, 将台站布设在摆坑内, 能在一定程度上降低高频和低频段的噪声水平. 台站环境噪声特征的研究结果可为流动地震台阵观测数据质量的定量评估, 观测期间的台站优化调整等提供重要依据.      

Fauna and standing crop of freshwater mussels in Poyang Lake, China

Freshwater mussels are a major component of the zoobenthos and they therefore play an important role in freshwater ecosystems. The community composition and the standing crop of freshwater mussels in Poyang Lake, the largest freshwater lake in China and one of two lakes connected to the Changjiang (Yangtze) River, were investigated from February 2008 to May 2009. Mussels were sampled in hydrologically and geographically distinct sampling areas. A total of 42 species and 13 genera were identified, of which 32 species were endemic to China. Two species, Unio douglasiae and Lamprotula caveata, dominated all sampling areas. The number of genera and species, and the number of species within each genus, differed significantly among sampling areas. Freshwater mussels were very abundant, with an overall density of 0.28 ± 0.22 ind./m2 and biomass of 4.08 ± 3.96 g/m2. Significant variation observed among sampling areas and among genera was probably due to the variety of habitats among the areas sampled and to the adaptability of different freshwater mussels to environments. This study suggests that Poyang Lake and other freshwater lakes in the region are important sites of freshwater mussel biodiversity and conservation.     

西格陵兰Disko湾表层沉积硅藻组合研究

本文分析了西格陵兰Disko湾的表层沉积物硅藻,发现并统计了分属于39个属的78个硅藻种及其变种。应用对应分析方法,对Disko湾表层沉积硅藻组合进行了分类:组合Ⅰ为Fragilariopsis cylindrus-Fragilariopsis oceanica组合,主要分布在西格陵兰Disko湾南部的近岸和外海处;组合Ⅱ为Detonula confervaceae休眠孢子-Thalassiosira nordenskioeldii组合,都分布在Dis-ko湾北部海域。其中,根据海流等环境要素的不同,组合Ⅰ又可进一步划分为两个亚区:组合Ⅰa为F.cylindrus-F.oceanica-Pauliella taeniata组合,主要分布于沿岸海区;组合Ⅰb为F.cy-lindrus-F.oceanica-Thalassiosira antarcticavar.borealis休眠孢子-Thalassiosiracf.antarcticavar.borealis组合,分布于外海区域。     

萨拉乌苏河流域萨拉乌苏组砂丘砂沉积特征

The Salawusu Formation of Milanggouwan section in Salawusu River Valley includes 7 layers of paleo-mobile dune sands, and 4 layers of paleo-fixed and semi-fixed dune sands. Their structures have been observed and their grain size, surface textural features and several main chemical elements have been analyzed. The results showed that： 1） Some of the aeolian structural characteristics of these dune sands are similar to that of the recent dune sands. 2） They are also similar to the recent dune sands in grain size components, and parameters of Mz,σ, Sk and Kg, as well as in several main chemical components. 3） The scattergrams of Mz-σ and SiO2-Al2O3＋TOFE and the probability curves of grain size showed that these paleo-dune sands are different from paleosols and fluvio-lacustrine facies, but are consistency with recent dune sands. 4） Quartz sands have well roundness and surface textural features such as dish-shaped pits, crescent-shaped pits, pockmarked pits, upturned cleavage plates, siliceous precipitates and siliceous crevasses, indicating that they had been carried for a long time by the wind. As the 11 layers of paleo-dune sands possess the aeolian characteristics in structure, grain size, surface textural features and chemical elements, the origin of their formation should be attributed to eolation.     

内蒙古白乃庙铜-金-钼矿床成矿机制——来自流体包裹体和He-Ar同位素的证据

白乃庙铜-金-钼矿是华北板块北缘中段一个重要矿床,其矿化特征既显示斑岩型蚀变特征,同时又表现出明显的后期造山作用改造的特点。本次研究通过系统的流体包裹体显微测温、激光拉曼和气液相色谱分析揭示其成矿流体为中—低温、中低盐度的CO_2(CO)-H_2O-CH_4(C_2H_2+C_2H_4)-NaCl-CaCl_2体系,流体混合作用和CO_2逃逸为成矿主要因素。富还原性流体的存在可能促使气相流体携带大量的Cu、Au等成矿元素迁移至较远点的白乃庙群地层,沿着片理或裂隙沉淀成矿。对不同成矿阶段矿石中黄铁矿的He-Ar同位素组成测试结果显示白乃庙矿床黄铁矿流体包裹体的~3He/~4He比值在0.06~0.71Ra之间,~(40)Ar/~(36)Ar比值为375.5~1436.3,指示成矿体系由不同性质和组成的两个端元流体混合而成,即混入了类似于MORB型地幔端元的高温高盐度流体和富含地壳放射成因氦但具有空气氩同位素组成特征的低温大气降水。白乃庙矿床属受后期造山作用改造的斑岩型铜-金-钼矿床,形成于古亚洲洋板块持续向南俯冲背景。