海进体系域碳氧同位素地球化学响应——以黔西南地区三叠系为例

层序地层研究表明，位于扬子地块西南缘的黔西南地区在中三叠世末期（相当于Ladinian-Carnian期）出现了一次与全球同步的大规模海侵，形成了一个向上变深的碳酸盐岩台地淹没沉积层序。垄头组顶部和竹竿坡组分别是海进体系域（TST）的下、上部分。碳、氧同位素研究表明，垄头组顶部自下而上δ（^18O）持续增大，而δ（^13 C）先逐渐增大，后在顶部界面附近快速下降，反映了垄头组顶部在暴露环境下氧化作用的结果。竹竿坡组δ（^13 C）自下而上逐渐增大，δ（^13 C）总体呈现逐渐减小趋势，反映了海平面变化特征。研究认为，海进体系域的δ（^13 C）和δ（^18 O）演化不但反映了海平面和沉积环境变化，同时对密集段（CS）、层序界面和古暴露面等也有很好的识别作用，在层序地层研究中具有重要的意义。     

Change of Gas Hydrate Reservoir and Its Effect on the Environment in Xisha Trough since the Last Glacial Maximum

In this article, Milkov and Sassen’s model is selected to calculate the thickness of the gas hydrate stable zone (GHSZ) and the amount of gas hydrate in the Xisha (西沙) Trough at present and at the last glacial maximum (LGM), respectively, and the effects of the changes in the bottom water temperature and the sea level on these were also discussed. The average thickness of the GHSZ in Xisha Trough is estimated to be 287 m and 299 m based on the relationship between the GHSZ thickness and the water depth established in this study at present and at LGM, respectively. Then, by assuming that the distributed area of gas hydrates is 8 000 km2 and that the gas hydrate saturation is 1.2% of the sediment volume, the amounts of gas hydrate are estimated to be ~2.76×1010 m3 and ~2.87×1010 m3, and the volumes of hydrate-bound gases are ~4.52×1012 m3 and ~4.71×1012 m3 at present and at LGM, re- spectively. The above results show that the thickness of GHSZ decreases with the bottom water tem- perature increase and increases with the sea level increase, wherein the effect of the former is larger than that of the latter, that the average thickness of GHSZ in Xisha Trough had been reduced by ~12 m, and that 1.9×1011 m3 of methane is released from approximately 1.1×109 m3 of gas hydrate since LGM. The released methane should have greatly affected the environment.     

Analysis on the noises from continuously monitoring GPS sites

In this paper,we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered bythe Crustal Movement Observation Network of China over the whole country.The data are obtained in the periodfrom the beginning of the observation to the November of 2005.On the basis of data processing,we analyze thepower spectrum density of coordinate component noise at each site and calculate the spectral indexes manifestingthe noise property of each component.The spectral indexes indicate that for most sites,the noise of time series ofeach coordinate component can be addressed by the model of white noise flicker noise;and for a small amountof sites,it can be described by the model of white noise flicker noise random walk noise.We also quantita-tively estimate each noise component in the model by using the criterion of maximum likelihood estimation.Theresult shows that the white noise in the time series of GPS site coordinates does not constitute the main part ofnoise.Therefore,the error estimation of site movement parameters is usually too small,or too optimistic if weconsider the white noise only.Correspondingly,if this factor is not fully considered in explaining these movementparameters,it might mislead the readers.     

武汉台形变观测与降雨参数之间的定量分析与研究

基于“前兆台网(站)观测数据跟踪分析平台”,对武汉台形变观测资料进行了系统分析,提取出观测曲线受降雨干扰影响的事件,采用降雨总量、初始驱动降雨量和瞬时降雨量最大值等降雨参数对降雨干扰事件进行统计分析。结果表明:降雨总量达40 mm、初始驱动降雨量为0.3 mm或瞬时降雨量最大值达0.6 mm时,DSQ型水管倾斜仪易受降雨干扰;SSY型铟瓦棒伸缩仪当降雨总量超60 mm或瞬时降雨量最大值大于0.5 mm时易受降雨干扰;VS型垂直摆倾斜仪受降雨干扰与降雨总量、初始驱动降雨量和瞬时降雨量最大值无显著相关关系;降雨总量对形变仪器观测物理量的影响基本呈现线性;而形变仪器观测物理量与初始驱动降雨量、瞬时降雨量最大值无显著相关关系。认为武汉台形变观测受降雨影响主要来自降雨渗透影响和周边水体荷载变化影响两个方面。     

地幔对流及其对地壳表层拉张盆地的影响

回顾近十年来在地幔对流方面的最新研究进展,阐述了板块俯冲后在地幔中的演化特征,以及地幔上升流即地幔柱的驱动机制和地质效应。特别介绍了地幔柱对地壳表层拉张盆地形成和充填过程的影响。进一步探讨了地幔柱活动在济阳坳陷的地质表现及其引发的火山岩浆活动、碎屑充填特征。认为盆地演化的阶段性间接反映了地幔对流的阶段性。     

青海省最高、最低气温不对称性变化的诊断分析

利用青海省１３个站逐月最高、最低气温资料,分析了月、季、年平均最高、最低气温的变化。结果表明最高、最低气温存在明显不对称变化趋势,尤其是３、４月存在明显的反向变化趋势。同时分析了西宁城市效应对最高、最低气温的影响。     

At‐a‐station hydraulic geometry relations, 1: theoretical development

This paper, the first of two, hypothesizes that: (1) the temporal variation of stream power of a river channel at a given station with varying discharge is accomplished by the temporal variation in channel form (flow depth and channel width) and hydraulic variables, including energy slope, flow velocity and friction; (2) the change in stream power is distributed among the changes in flow depth, channel width, flow velocity, slope, and friction, depending on the boundary conditions that the channels has to satisfy. The second hypothesis is a result of the principle of maximum entropy and the theory of minimum energy dissipation or its simplified minimum stream power. These two hypotheses lead to families of at‐a‐station hydraulic geometry relations. The conditions under which these families of relations can occur in the field are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

在Zebiak-Cane模式中观测MJO强迫对ENSO可预报性的影响, 第1部分:对最大预报误差的影响

With the observational wind data and the Zebiak-Cane model, the impact of Madden-Julian Oscillation (MJO) as external forcing on El Ni(n)o–Southern Oscillation (ENSO) predictability is studied. The obs...     

Application of a Delay-difference model for the stock assessment of southern Atlantic albacore (Thunnus alalunga)

Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-difference model was applied to fit catch and catch per unit effort(CPUE) data(1975–2011) of the southern Atlantic albacore(Thunnus alalunga) stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises(CVs) were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters α and β in Ricker stock-recruitment model and the catchability coefficient q. α is more sensitive to CV than β and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield(MSY, 21756 t to 23408 t; median 22490 t) with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122 t, and the estimated ratios of catch against MSY for the past seven years were approximately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed delay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.     

基于高分二号卫星数据的农作物分类方法研究

针对目前高分二号卫星数据(GF-2)有较高的空间分辨率而在农业领域应用较少和农作物分类普遍存在"同谱异物"和"同物异谱"的现象,以辽宁省沈阳市苏家屯区以西的新开河村周边为试验基地,利用最佳波段组合指数法(OIF)对所选取的高分二号(GF-2)卫星数据的纹理特征和植被指数以及波段信息进行筛选,选取最佳的波段组合,以增加分类信息、减少数据冗余。最后,针对筛选后的数据,使用最大似然法进行分类,得到农作物的分类结果。结果表明,利用该方法对农作物进行分类,分类精度得到了一定程度的提高,为目前大规模农作物种植面积的精确、迅速统计提供了一套可行的方案。