Shrinkage and fragmentation of marshes in the West Songnen Plain,China, from 1954 to 2008 and its possible causes

Agricultural development under climatic variations has resulted in substantial loss of marshes in the West Songnen Plain in the past decades. In this paper, the shrinkage and fragmentation process of marshes and its possible causes in the West Songnen Plain from 1954 to 2008 were explored using historical topographic maps and remote sensing data. Results indicated that the West Songnen Plain underwent considerable shrinkage and fragmentation of marshes in that same period. Marshes occupied 6404 km² in 1954, but this area has decreased by 74% in the past 54 years. The average annual decrease rate of marshes was 88 km² per year. Meanwhile, the number of marsh patches decreased from 1411 to 514, and the mean patch size decreased from 454 to 320 ha. Cropland and salinized wasteland were the two main land use types into which marshes were converted. During the same period, grassland decreased by 54%, cropland increased by 22%, and salinized wasteland expanded by 612%. A significant increase in air temperature and index of dryness was found in the study region, along with decreased precipitation, thereby affecting the marsh systems through the changing hydrological regimes. On the other hand, population, gross domestic product, and livestock number increased considerably as marshes shrank and became fragmented. Governmental policy changes played a key role in land use transformations in the study region.     

基于井下摆天然地震数据测量首都圈近地表波速结构

收集了首都圈数字化地震遥测台网58个井下摆2003-2008年记录的102次M≥3.0地震的数据.通过鉴别直达波及对应地表反射波的波形,发现两者到时差与震中矩和方位角无关.基于斯涅尔定律,分析获得了这些台站上方厚约300 m浅地表土层P波和S波平均速度结构以及波速比.结果表明,首都圈区域近地表P波和S波平均速度分别约为...     

A Review of Seismicity in 2010

1 SURVEY OF GLOBE SEISMICITY IN 2010A total of 28 strong earthquakes with MS≥7.0 occurred in 2010 throughout the world according to the China Seismic Network (Table1).The strongest was the Chile earthquake     

2010年震情述评

1 全球地震活动概况 据中国地震台网测定,2010年全球共发生7级以上地震28次(表1),最大地震为2月27日智利8.8级地震(图1).与2009年相比,全球地震频次和能量释放明显增加.2010年全球7级以上地震活动有以下特点： 2010年全球共发生7级以上地震28次,明显高于1900年以来的平均水平(18次/年),与2009年(20次)相比,地震频次明显增加.2010年南美板块西边界和印度-澳大利亚板块活跃,全球28次7级以上地震中有16次分布在印度-澳大利亚板块的北边界和东边界上,5次在南美板块西边界,4次在菲律宾板块边界,2次在北美板块边界,1次在中国青藏块体边缘地区,显示出空间分布相对集中的特点(图1).     

Development and calibration of the Moon-based EUV camera for Chang'e-3

The process of development and calibration for the first Moon-based extreme ultraviolet(EUV) camera to observe Earth's plasmasphere is introduced and the design, test and calibration results are presented. The EUV camera is composed of a multilayer film mirror, a thin film filter, a photon-counting imaging detector, a mechanism that can adjust the direction in two dimensions, a protective cover, an electronic unit and a thermal control unit. The center wavelength of the EUV camera is 30.2 nm with a bandwidth of 4.6 nm. The field of view is 14.7° with an angular resolution of 0.08°, and the sensitivity of the camera is 0.11 count s-1Rayleigh-1. The geometric calibration, the absolute photometric calibration and the relative photometric calibration are carried out under different temperatures before launch to obtain a matrix that can correct geometric distortion and a matrix for relative photometric correction,which are used for in-orbit correction of the images to ensure their accuracy.     

中国西北地表能量分配影响因子及特征空间法适用性北大核心CSCD

利用2009年地面实测资料,分析中国西北地区不同气候区潜热、感热及其与净辐射之比随土壤体积含水量、土壤温度及入射辐射的变化特征,并结合2000—2018年中分辨率成像光谱仪(MODIS)产品讨论特征空间法在中国西北地区的适用性。结果表明:在以玛曲站为代表的高寒湿润区,入射能量始终是潜热的主导因素,用于潜热估算的斜率φ可直接取1.26,潜热估算精度依赖于净辐射的反演结果。在以兰州大学半干旱气候与环境监测站(SACOL,榆中站)和长武站为代表的半干旱、半湿润区,当入射能量充足时,土壤水分成为潜热的主导因子,这时候使用特征空间法估算的斜率φ值与实测值相关性显著,φ的估算精度将直接影响潜热估算结果。所以,特征空间法适用于以水分为潜热主导因子的地区和时段,且要满足植被指数与地表温度呈负相关。另外需要注意的是在选择特征空间法研究区时必须保证植被指数与地表温度的散点呈规则的“三角形”。     

In situ observation of crystal growth in a basalt melt and the development of crystal size distribution in igneous rocks

The speciation of CO₂ in dacite, phonolite, basaltic andesite, and alkali silicate melt was studied by synchrotron infrared spectroscopy in diamond anvil cells to 1,000 °C and more than 200 kbar. Upon compression to 110 kbar at room temperature, a conversion of molecular CO₂ into a metastable carbonate species was observed for dacite and phonolite glass. Upon heating under high pressure, molecular CO₂ re-appeared. Infrared extinction coefficients of both carbonate and molecular CO₂ decrease with temperature. This effect can be quantitatively modeled as the result of a reduced occupancy of the vibrational ground state. In alkali silicate (NBO/t = 0.98) and basaltic andesite (NBO/t = 0.42) melt, only carbonate was detected up to the highest temperatures studied. For dacite (NBO/t = 0.09) and phonolite melts (NBO/t = 0.14), the equilibrium CO₂ + O^2? = CO₃ ^2? in the melt shifts toward CO₂ with increasing temperature, with ln K = ?4.57 (±1.68) + 5.05 (±1.44) 10³ T ^?1 for dacite melt (ΔH = ?42 kJ mol^?1) and ln K = ?6.13 (±2.41) + 7.82 (±2.41) 10³ T ^?1 for phonolite melt (ΔH = ?65 kJ mol^?1), where K is the molar ratio of carbonate over molecular CO₂ and T is temperature in Kelvin. Together with published data from annealing experiments, these results suggest that ΔS and ΔH are linear functions of NBO/t. Based on this relationship, a general model for CO₂ speciation in silicate melts is developed, with ln K = a + b/T, where T is temperature in Kelvin and a = ?2.69 ? 21.38 (NBO/t), b = 1,480 + 38,810 (NBO/t). The model shows that at temperatures around 1,500 °C, even depolymerized melts such as basalt contain appreciable amounts of molecular CO₂, and therefore, the diffusion coefficient of CO₂ is only slightly dependent on composition at such high temperatures. However, at temperatures close to 1,000 °C, the model predicts a much stronger dependence of CO₂ solubility and speciation on melt composition, in accordance with available solubility data.     

Seismic-event-based methodology to obtain earthquake-induced translational landslide regional hazard maps

A seismic-event-based methodology to generate earthquake-induced translational landslide maps using Newmark method is proposed. The steps are: (1) to construct a GIS-based geotechnical database; (2) to identify those areas that are susceptible to the occurrence of translational landslides based on available geological information; (3) to compute a static safety factor; (4) to compute the critical acceleration that defines the threshold acceleration required to cause a displacement; (5) to characterize the seismic hazard as a set of stochastic events, collectively exhaustive and mutually exclusive, that fully describes the hazard spatial distribution and annual frequency of occurrence (in accordance with the earthquake location, depth and magnitude) with the appropriate ground-motion prediction equations; (6) to compute the Newmark displacement; and finally, (7) to carry out a probabilistic translational landslide hazard analysis to estimate an exceedance rate of a given displacement. This methodology is applied to Mexico, and maps for return periods of 150 and 500 years are presented. Results shown in maps are estimations of where translational landslides may occur and should be useful to carry out local studies to elaborate recommendations of site specific hazard reduction plans as well as to calculate insurance rates. In addition, these results are useful to identify civil protection actions, risk management at regional and local level, and land use planning, as well as for promoting more detailed vulnerability and risk studies at different scales.     

被动型原子频率标准体系内优势组合的研究

提出了被动型原子频率标准体系内优势组合的建议.扼要地介绍了以汽泡型铷原子频率标准为背景的体系内优势组合的研究情况及其初步结果.