地震波场的复射线展开

利用复射线理论将惠更斯原理推广到复空间,发展出一种简便的波场计算方法.本文以均匀柱面波在平界面上的反射场为例,用复射线展开法计算了时谐地震波及瞬变地震波在部分反射、全反射和临界角过渡区的场分布,并与平面波谱积分结果进行了比较.结果表明,用复射线展开法可以自动平滑过渡区反射场的奇异性,因而该方法可直接处理焦点、焦散线和全反射过渡区等复杂的波场分析与综合问题,并可简化数值计算过程.     

冀西北尚义黄土窑地区尚义杂岩和红旗营子群的锆石SHRIMP U-Pb定年及地质意义

尚义杂岩是冀西北地区有代表性的变质地质体,由变质表壳岩和侵入岩组成。其中的变质表壳岩曾认为是新太古代晚期蛇绿岩洋壳残片。该区也有红旗营子群存在。我们对尚义黄土窑地区尚义杂岩和红旗营子群不同类型岩石进行了锆石SHRIMP U-Pb定年。含石榴黑云斜长片麻岩(HB1410)核部锆石年龄为310~2500Ma,边部变质锆石年龄为255Ma左右。黑云片麻岩(HB1411)和石英岩(HB1415)碎屑锆石年龄都为2.5Ga左右。辉长岩(HB1518)和石英闪长岩(HB1519)岩浆锆石年龄为278~279Ma。根据这些资料和前人研究,该地区的原红旗营子群和尚义杂岩变质表壳岩主体可能不是新太古代地质作用产物,而是形成于晚古生代,由不同时代地质体组成的构造杂岩。不存在所谓的太古宙蛇绿岩残片。晚古生代时期,中亚造山带对华北克拉通北缘的影响十分强烈。     

Formation and performance of collaborative disaster management networks: Evidence from a Swedish wildfire response

Natural disasters present a multitude of entangled societal challenges beyond the realms and capacities of single actors. Prior research confirms that effective collaboration is of critical significance to address such complex collective action problems. Yet, studies rarely investigate if patterns of collaboration are appropriately aligned (‘fit’) with how different challenges (tasks) are interdependent, or how levels of fit influence collective action performance. We develop a set of hypotheses specifying what constitutes a good fit between collaborative networks and task interdependency. Using unique empirical data from the response to a major wildfire in Sweden, we examine how individual actors select collaboration partners and tasks during the formation the collaborative crisis response network. Then we test if levels of fit in the established network influence performance. We show that patterns of actor and task interdependency influence the formation of collaborative networks and that a good fit seems to be associated with more effective collaboration. Our data even suggest that a good fit is more important for performance than actors’ prior crisis management experience and level of professionalization. Further, we show that actors only partially engage in actor-task configurations conducive to high performance. Our study probes the limitations of simplified accounts of collaborative disaster management by enabling more precise and theoretically informed empirical inquiries regarding the mechanisms that shape the structure and performance of collaborative networks.     

赞皇杂岩翁城地区长城系常州沟组砂岩碎屑锆石U-Pb-Hf同位素研究

常州沟组是华北克拉通太古宙-古元古代变质基底上最早的沉积盖层之一,其碎屑锆石U-Pb年代学与Hf同位素特征分析对探讨长城系形成时代、源区特征以及基底演化均具有重要的研究意义。本文对华北克拉通中部赞皇杂岩瓮城地区长城系常州沟组底部砂岩样品进行了LA-ICP-MS碎屑锆石 U-Pb定年和LA-MC-ICP-MS碎屑锆石Lu-Hf同位素分析。砂岩样品中碎屑锆石主要年龄峰值约为2500 Ma,推断其碎屑物质主要来自于华北克拉通新太古代晚期变质基底,而最年轻的碎屑锆石年龄为1822 Ma,结合赞皇杂岩变质基底普遍经历了1850~1800 Ma变质作用以及区域上上覆大红峪组火山岩中1635 Ma结晶锆石年龄,限定瓮城地区长城系常州沟组沉积时代为1 800~1 635 Ma。砂岩样品中碎屑锆石的εHf(t)值变化于-6.8~+5.2之间,相应的两阶段模式年龄峰值约为2820 Ma,结合赞皇杂岩已发表的2900~2700 Ma岩浆锆石和碎屑锆石Hf同位素结果,进一步表明2900~2700 Ma为赞皇杂岩地壳生长最主要的时期。综合太行山中南部地区已发表的长城系常州沟组的沉积学与新的年代学数据,推测赞皇杂岩瓮城地区长城系常州沟组沉积于陆内裂谷盆地。     

中国近百年雨量与大气环流因子的关系

研究了近百年南方涛动年指数,北半球西风带大气环流Ｗ．Ｃ．环流型年频数对中国大范围年降水量有旱涝的影响,探讨了大气环流因子影响的空间分布变化规律及影响的复杂性,非线性及南北环流不同配置多因子相互作用造成的综合影响特征,发现：（１）ＳＯＩ、Ｗ、Ｗ．Ｃ．Ｅ环流因子对中国降雨的影响不是局地的,而 大范围普遍存在的,只不过对越靠近海洋的地方越显著;（２）并不是单个环流因子的变化就可完全解释清楚雨量的变化,多     

复杂地形低风速气象特征分析

利用13个地面站和1个100 m气象塔的全年实测资料分析湖南中北部丘陵地区中尺度范围的低风速气象特征。结果表明：（1）该区域低风速出现频率高,小于15 m/s的风速出现频率年均达416%;（2）低风速与地形情况密切相关,区域内西部山地的低风速出现频率明显高于东部平原地区;（3）低风速的出现具有日变化特点,典型出现时间段是夜间至次日上午;（4）低风速条件下10 min平均风向多出现大角度变化的情况,60°以上的风向变化频率可达20%～30%。（5）水平风向标准差在低风速情况下明显增大,但观测仪器性能会对小风结果产生影响。     

Local Log-Law-of-the-Wall in Neutrally-Stratified Boundary-Layer Flows

It is well known that in a neutrally-stratified turbulent flow in a deep constant-stress layer above a flat surface,the horizontal mean velocity varies logarithmically with height (the so-called `log-law-of-the-wall').More recently, the same logarithmic law has also been foundin the presence of non-flat surfaces, where it governs thedynamics of the areally-averagedvelocity and involves renormalized effective parameters.Here, we analyze wind profiles over two-dimensional sinusoidal hillsobtained both from numerical simulations performed with a primitiveequation model and from wind-tunnel measurements. We showthat also the local velocity profiles behave to a verygood approximation logarithmically, for a distance from the surface of the order of the maximum hill height almost to the top of the boundary layer. Such alocal log-law-of-the-wall involves effective parameters smoothly depending on theposition along the underlying topography.This dependence looks very similar to the topography itself.     

不同下垫面上近地层湍流的多尺度属性研究

文中利用统计和多尺度分析方法分析了几种复杂下垫面情况下的风、温湍流脉动观测资料 ,结果表明 :下垫面结构的差异明显地影响湍流量 ,如 :戈壁地区的热力作用明显大于雪面和城郊面 ,表现在湍流时间尺度上也明显地大于雪面和城郊面。但复杂下垫面下的湍谱在惯性区仍满足“- 23”次律 ;多尺度方法研究湍流 ,可以更简捷地分析湍流的多尺度结构及其在湍流输送中的作用。由此可看出 ,多尺度方法是发展湍流统计理论的一种有效工具。     

沪宁高速公路一次复杂性大雾过程的数值模拟试验

为探明高速公路大雾天气的成因和演变规律,揭示雾影响交通能见度的机理,本文根据布设于我国沪宁高速公路沿线的环境气象自动监测系统(AWMS)实测资料和覆盖公路周边地区的常规气象台站观测资料,筛选出2009年11月7日发生在沪宁高速公路上的一次典型复杂性大雾天气过程.在分析天气实况的基础上,应用高时空分辨率的非静力中尺度数值预报模式WRF3.1,结合NCEP 0.5°×0.5°气象再分析资料,对该过程进行了数值模拟;利用实测资料对模拟结果进行了验证,并剖析了此次复杂性大雾过程形成的动力、水汽和热力条件.研究表明:(1)本次大雾前后的天气形势相对稳定,江苏地区主要受入海反气旋西南侧东南气流影响,整个大雾过程中地面风力始终微弱,为大雾形成提供了有利的动力条件;(2)模式模拟的由大气液态含水量条件判别的成雾区分布与实测雾区范围基本吻合;(3)模式模拟的能见度与AWMS实测能见度十分接近;(4)本次大雾过程最初是团雾雏形,在夜间辐射冷却作用下,转为辐射雾,之后,来自东南海上的暖湿空气平流进入江苏陆地后,所产生的平流雾雾体与原有辐射雾雾体结合发展为范围更大的辐射平流混合雾;(5)日出后短波辐射增温是此次复杂性大雾雾体得以快速消散的主要原因.     

Geochemistry of mafic rocks of the Karakaya complex,Turkey: evidence for plume-involvement in the Palaeotethyan extensional regime during the Middle and Late Triassic

The Karakaya Complex within the Early Mesozoic Cimmerian Orogeny in northern Turkey represents the remnants of the Palaeotethys. It includes slivers and/or mega-blocks of slightly metamorphic basic volcanic rocks associated with fossiliferous sediments as well as hypabyssal and intrusive rocks with basaltic-andesitic to ultramafic compositions. They display two distinct compositional groups; namely alkaline and variably tholeiitic. The alkaline basalt samples are more akin to oceanic-island basalts (OIB) with relatively enriched trace element characteristics together with strong partitioning in HREE ([La/Yb]_N = 5.8–16.2), suggesting that garnet is present as a residual phase in the source of those basalts. The variably tholeiitic samples apart from diabases display E-MORB characteristics; being relatively depleted compared to the alkaline counterparts and less fractionated REE patterns ([La/Yb]_N = 2.1–3.6). The diabases, on the other hand, are distinctively different with a significant negative Nb anomaly (Zr/Nb = 28.9–43.4) and flat REE patterns ([La/Yb]_N = 0.8–1.4), suggesting their generation above a supra-subduction zone, probably a back-arc basin. These results may suggest that a mantle plume-related magmatism associated with extensional oceanic system should have been installed within Palaeotethys during Middle-Late Triassic time, which was then incorporated into subduction–accretion prism forming the final picture, that is, “the Karakaya Complex”.