模拟倾斜界面情况下区域地震范围内的长周期Pnl波

中国大陆地壳厚度的特点是东部地区薄西部地区厚,因此在计算Pnl波的Green函数时进一步考虑了莫霍界面倾斜的影响.本文将广义射线理论推广到倾斜层结构模型,该方法的计算结果与有限差分的计算结果有很好的一致性.理论计算表明,在同一个倾斜结构模型中沿相反方向传播的Pnl波有明显的差异.因此当地壳厚度的变化不能忽略时,根据水平层模型的理论计算结果拟合Pnl波记录时效果不够理想.对菏泽、门源地震资料的处理结果表明,用一个更接近实际地壳的倾斜层模型来拟合Pnl波比用等效厚度平行层模型来拟合要更为合理.     

石灰岩细观力学特性的颗粒流模拟

岩体地区地质灾害的发生和发展取决于岩石细观组分的运动学行为。研究岩石运动学行为时通常将岩石作为整体研究对象较多,而直接以细观组分为对象的研究较少。以石灰岩为例,根据室内试验获得的岩石力学性质指标,使用基于非连续介质理论的颗粒流方法,将材料离散成刚性颗粒组成的模型,把颗粒细观变化与宏观力学特性联系起来,建立了石灰岩的细观结构模型,获得了颗粒接触力、颗粒接触模量、接触连接强度和连接刚度比等细观力学参数。由于文中直接以细观成分为研究对象、反映了岩石和岩体组成的本质特点,所得结论不仅对含裂隙岩石本构关系研究具有广阔的应用前景,而且对岩体工程性质和地质灾害机制研究也具有重要的理论意义。     

Nutrient composition and distributions in coastal waters impacted by the Changjiang plume

Four cruises were conducted during 2002--2003 in the Changjiang Estuary and adjacent coastal areas. The data presented show a clear coast to open sea gradient in nutrients related to the river inputs. Maximum values of chlorophyll a were typically observed at intermediate salinities at surface water and coincided with non-conservative decreases in nutrients along the salinity gradient, indicating that removal of nutrients was related to phytoplankton uptake. The seasonal variations of nutrient concentrations were just opposite to those of chlorophyll a, indicating that the seasonal variations of nutrients were mainly controlled by phytoplankton uptake, whereas riverine inputs merely weakened or balanced its extent. During the estuarine mixing, phosphate demonstrated some remobilization during all the four cruises; whereas both conservative and non-conservative behaviors for dissolved inorganic nitrogen and silicate were observed in the study area, indicating that both biotic and abiotic events may affect their behaviors during the estuarine mixing. Under the influence of freshwater inputs with high value of ratio of nitrogen to phosphorus, the estuarine and coastal waters impacted by the Changjiang plume were high （ 〉 30） in ratio of nitrogen to phosphorus, but rates of primary production were apparently not constrained by any kind of nutrient elements. However, the low （ 〈 1 ） ratio of silicate to nitrogen in most of the study area might be linked with the rapidly increasing frequency of harmful algal bloom （HAB） incidents in recent years in the coastal waters impacted by the Changjiang plume.     

微波消解-电感耦合等离子体质谱法测定土壤和沉积物中痕量稀土元素

建立了微波消解-电感耦合等离子体质谱法测定土壤和沉积物中15种痕量稀土元素的分析方法。研究了溶样试剂、微波消解程序、标准溶液配制、质谱干扰与内标元素对稀土元素测定的影响。加入氢氟酸能有效打开样品,以HNO₃-HF-H₂O₂混合酸溶解样品,稀土元素的溶出率较高。采用模拟土壤、沉积物中稀土元素天然组成比值的校正溶液,对稀土元素间的干扰具有明显的抑制作用。通过测定单个La、Ce、Pr、Nd和Ba的氧化物及氢氧化物产率,计算出等效干扰浓度,进而校正多原子离子干扰。利用¹⁰³Rh内标校正系统,有效地抑制了分析信号的动态漂移。方法检出限为1.2~7.1 ng/g,精密度(RSD)≤5.3%(n=6),加标回收率为86.1%~110.1%。使用土壤、沉积物标准物质进行验证,测定结果与标准值相符。建立的方法样品处理程序简单快速、线性范围宽、分析重现性好、结果准确,适用于大批量地质样品的分析。     

浅析数字摄影测量在1∶500地形图测绘中的应用

数字摄影测量,应用计算机技术、数字影像处理、影像匹配、模式识别等理论与方法,以计算机视觉代替人眼的立体观测,其产品与中间数据的记录以及处理的原始资料均是数字的,较之常规的(传统的)数字产品的生产方法,具有自动化程度高、速度快、成果多样化等优点。两次外业和两次内业,是∶地形图数字摄影测量的主要作业流程,第二次外业调绘作为1500数字摄影测量的主要外业工作与常规调绘方法有一定的区别。∶地形图数字摄影测量适合于1500大面积数字化测图。     

Record Low Sea-Ice Concentration in the Central Arctic during Summer 2010

The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration(SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic(CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements.Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector,which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water,increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.     

西藏羌塘盆地东部中-上侏罗统沉积特征及沉积相划分

详细野外剖面测量基础上,对羌塘盆地东部中-上侏罗统剖面主要岩类的宏观特征(颜色和构造)、物质组分、结构及磁化率等特征进行系统研究,研究区碎屑岩主要为砾岩、砂岩、粉砂岩和泥岩等岩类,磁化率值呈现低→高→低→高→低(雀莫错组→布曲组→夏里组→索瓦组→雪山组)的规律性变化。综合沉积特征显示雀莫错组和雪山组主要为河流相-河控三角洲相沉积,布曲组为碳酸盐缓坡相沉积为主,夏里组主要为潮坪-泻湖相沉积,索瓦组主要为混积陆棚-泻湖-潮坪相沉积,中-晚侏罗世羌塘盆地古水深在下降的总趋势中呈现浅→深→浅→深→浅的升降旋回,盆地沉积中心由东向西迁移,区域构造演化和全球海平面变化共同控制了盆地沉积面貌。     

不同强度冷空气对太湖水热交换的定量影响

作为冷季主要的天气事件,冷空气过境会改变湖泊上方的气团性质,对湖泊的水热通量产生影响,进而影响湖泊的生物物理和化学过程.以亚热带大型浅水湖泊——太湖为研究对象,基于2012-2017年5个冷季（11月-翌年3月）的太湖中尺度通量网观测数据,量化不同强度冷空气（寒潮、强冷空气和较强冷空气）对太湖水热通量的影响.结果表明：在5个冷季中,寒潮、强冷空气和较强冷空气发生的总次数分别为4、11和33次,累积持续天数分别为14、31和78天.冷空气过境显著增强太湖的水热通量,3种冷空气过境使太湖的感热通量分别增至无冷空气时的10.3、6.0和4.3倍,潜热通量分别增至无冷空气时的4.0、2.1和2.7倍.虽然冷空气影响天数仅占冷季天数的16.4%,但对整个冷季的潜热和感热通量贡献分别为34.9%和51.7%,以较强冷空气贡献最大.冷空气影响时,水-气界面的温度梯度是太湖感热通量的主控因子,而潜热通量的主控因子为风速.与深水湖泊相比,太湖等浅水湖泊对冷空气过境的响应更快,寒潮过境时尤为明显.     

近30a龙羊峡水库周边地区沙漠化遥感监测

在RS和GIS支持下,选取4期遥感数据,采用室内解译和野外检验修正的方法,获得龙羊峡水库周边地区不同时期土地沙漠化数据库.结果显示,在过去30 a中,龙羊峡水库周边地区土地的沙漠化在时间上经历了一般发展到正在逆转两个阶段;2000年以后,极重度沙漠化土地和重度沙漠化土地变化最为明显,均呈现逆转趋势,其中极重度沙漠化逆转为其他类型的总面积为145.90 km2,重度沙漠化土地逆转为中度沙漠化面积为146.44km2;在沙漠化土地的空间分布上,过去30 a里,沙漠化土地主要集中分布在龙羊峡两岸的塔拉滩和木格滩地区;研究区内沙漠化的逆转主要是由重度和极重度沙漠化土地转变为中度和轻度沙漠化土地.1975-1989年,研究区的降水呈增加趋势,但是由于这一时期人为因素的影响,沙漠化呈不断加剧的态势;1989-2000年,研究区的气候趋向于暖干化,加上过度放牧等人为因素,重度和极重度沙漠化土地持续发展;2000年以后,研究区的气候趋向于暖湿化,政府实施了一系列生态环境保护、恢复计划,沙化土地呈现逆转的态势.     

不同大气强迫作用下陆面模式CAS-LSM多年 冻土活动层厚度模拟与不确定性研究

冻土在气候系统中起重要作用,研究并揭示冻土时空变化对于增加陆气相互作用的理解具有重要意义.本研究利用包含土壤冻结融化界面动态变化的陆面过程模式CAS-LSM(Chinese Academy of Sciences Land Surface Model),采用0.9°(纬度)×1.25°(经度)分辨率,结合4种大气强迫数...