Synthetic body wave seismograms for laterally varying media containing thin transition layers     

V. &#;ervený 《Geophysical Journal International》1989,99(2):331-349

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湖北麻城金罗家遗址古文化层的正构烷烃分布及其古植被意义     

邹胜利  朱俊英  熊北生  李仁成  金芳  谢树成 《海洋地质与第四纪地质》2007,27(3):119-125

利用气相色谱-质谱联用仪(GC-MS)对湖北麻城金罗家遗址古文化层样品进行了系统分析,检测出丰富的类脂物分子,包括正构烷烃、一元正脂肪酸、一元正脂肪醇和α-正构脂肪酮等,主要讨论正构烷烃类脂物的分布特征。正构烷烃的分布在各文化层不同,其中,在生土层以C17为主峰;西周文化层F2和F4两样品以C17和C31为双主峰,F3样品以C17为主峰;东周文化层主要以C17和C31为双主峰,而F 7以C31为主峰,F9以C17为主峰;唐宋文化层以C17和C31为双主峰;明清文化层以C31为主峰,现代耕植土层以C29为主峰。而正构烷烃高碳数C27/C31比值的变化反映出遗址域中木本植物与草本植物的相对变化,正构烷烃高碳数ACL值反映遗址域中的草本植物与木本植物之间的转变,有机δ13C表现为C3和C4植物,它们在本剖面上表现出多阶段的变化。因此,正构烷烃在不同的人类古文化层具有不同的分布特征,除了反映当时的微生物活动、植物属种的相互取代或分子沉积后的改造作用外,还可能蕴藏着当时的气候变化和古人类活动的信息,有待进一步研究。  相似文献   

Long-term dispersion in unsteady skewed free surface flow     

John M. Hamrick 《Estuarine, Coastal and Shelf Science》1986,23(6)

An analysis of two-dimensional horizontal plane shear dispersion in steady, periodic, almost-periodic and randomly forced skewed free surface flow is presented. A two-time scale perturbation analysis of the advection-diffusion equation is used to derive the two-dimensional advection-dispersion equation and the horizontal dispersion coefficient tensor. For combinations of steady, periodic and almost-periodic flow, the time dependent dispersion coefficient tensor contains steady terms and periodic terms at frequencies associated with the forcing frequencies and their sums and differences. For combinations of steady, periodic, almost-periodic and stationary random forcings, the expected value dispersion coefficient tensor contains terms associated with the steady forcings and terms associated with the unsteady forcings represented by the spectral density functions of the unsteady forcings. Estimates of the magnitude of the expected value dispersion coefficient tensor are presented for representative estuarine and continental shelf conditions.  相似文献   

Coupling characteristics of stress and strain at different layers of different sub-regions in Yunnan and its adjacent areas     

马宏生  张国民刘杰  江在森华卫王辉  王新岭 《地震学报(英文版)》2007,20(2):133-146

In this paper,we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regionalseismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005.By using thecross-correlation method,64 splitting events of 16 stations are processed.We also collect the splitting results ofeight earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas.The orientations of maximum principal compressive stress of three sub-regions in this area are derived from theCMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axisazimuth-averaging method.The principal strain rate at each observatory is deduced from the observations ofCrustal Movement Observation Network of China during the period from 1999 to 2004.In addition,the data of Pnaniso-tropy and SKS splitting of Yunnan and its adjacent areas are also collected.We have discovered from thisstudy that the continental lithosphere,as a main seismogenic environment for strong earthquake,can be dividedinto blocks laterally;the mechanical behavior of lithosphere varies with depth and can be divided into differentlayers in the vertical orientation;the information of crustal deformation obtained from GPS might be affected bythe type of blocks,since there are different types of active blocks in Yunnan and its adjacent areas;the shear wavesplitting in this region might be affected mainly by the upper crust or even the surface tectonics.  相似文献   

天然荒漠植物干旱期根区土壤贮水量的确定   总被引：1，自引：0，他引：1  

朱永华  任立良  吕海深 《水文》2007,27(1):14-16,13

在土壤-植物-大气连续统中,植物根区土壤贮水量是一个重要水源。对植物根区贮水量的研究是对该连续统研究的一个重要内容。准确估计植物根区土壤贮水量将为估计灌溉水量、生态需水量及环境的可持续发展提供科学的依据。特别是在中国干旱内陆河下游地区,由于水量减少造成植物根区贮水量减少而产生植物死亡．由此引起一系列生态环境问题。本文基于在一定边界条件下Richard方程的解,利用地表测值(0～10cm土层容积含水量——遥感方法可确定的值)及根系分布密度来确定黑河下游地区天然荒漠植物根区土壤贮水量,从而证明了利用遥感方法可以确定中国荒漠天然植物根区土壤贮水量。为今后从面上确定根区贮水量提供了科学基础。  相似文献   

Electrical Structure and Fault Features of Crust and Upper Mantle beneath the Western Margin of the Qinghai-Tibet Plateau： Evidence from the Magnetotelluric Survey along Zhada-Quanshui Lake Profile   总被引：1，自引：0，他引：1  

金胜叶高峰  魏文博邓明 景建恩 《中国地质大学学报(英文版)》2007,18(4):326-333

The magnetotelluric (MT) survey along the Zhada (札达)-Quanshui (泉水) Lake profile on the western margin of the Qinghai (青海)-Tibet plateau shows that the study area is divided into three tectonic provinces by the Yalung Tsangpo and Bangong (班公)-Nujiang (怒江) sutures. From south to north these are the Himalayan terrane, Gangdise terrane, and Qiangtang (羌塘) terrane. For the study area, there are widespread high-conductivity layers in the mid and lower crust, the top layers of which fluctuate intensively. The high-conductivity layer within the Gangdise terrane is deeper than those within the Qiangtang terrane and the Himalaya terrane, and the deepest high-conductivity layer is to the south of the Bangong-Nujiang suture. The top surface of the high-conductivity layer in the south of the Bangong-Nujiang suture is about 20 km lower than that in the north of it. The high-conductivity layer within the Gangdise terrane dips toward north and there are two high-conductivity layers within the crust of the southern Qiangtang terrane. In the upper crust along the profile, there are groups of lateral electrical gradient zones or distortion zones of different scales and occurrence indicating the distribution of faults and sutures along the profile. According to the electrical structure, the structural characteristics and space distribution of the Yalung Tsangpo suture,Bangong-Nujiang suture, and the major faults of Longmucuo (龙木错) and Geerzangbu are inferred.  相似文献   

中太平洋WM1和WX海山富钴结壳元素相关性及其层间变化研究   总被引：2，自引：0，他引：2  

佟景贵王吉中  初凤友李胜荣  方念乔吴敏 牛花朋 《岩石矿物学杂志》2007,26(2):155-163

在结壳矿物学等基本特征分析的基础上,对中太平洋WM1和WX海山富钴结壳中的主量元素、微量元素、稀土元素和铂族元素含量、层间变化及其相关性进行了研究,结果表明:本区结壳从下层到上层,粘土矿物和石英等碎屑矿物逐渐增多,很可能与青藏高原的隆升和剥蚀以及亚洲季风演化有关;TFe/Fe2 从结壳下层到上层逐渐增高,反映了结壳的氧化性由下层到上层增强,海山的沉降可能是造成结壳生长后期环境氧化性增强的重要原因;Ti、Co、Pb、As、Mn、TFe等元素与TFe/Fe2 呈正相关,反映结壳中这些元素的富集与氧化环境有关,而Ca、P、Pt和∑REE等元素与TFe/Fe2 呈负相关,反映结壳中这些元素的富集与还原环境有关;Fe与Co显著正相关是本区结壳的重要特点;结壳的Co与(Fe Mn)的相关性大于Co与Fe的相关性及Co与Mn的相关性;P含量小于1%时,Co与P相关性不明显,当P含量大于1%时,Co与P呈明显负相关,磷酸盐化的过程对铁锰结壳吸附Co的能力起到抑制作用。聚类分析将Pt、∑REE与P和Ca分为一组,说明在结壳中Pt和∑REE主要赋存在碳氟磷灰石中,结壳的磷酸盐化的过程对Pt和∑REE的富集起到了重要的作用。  相似文献   

对RIEMS模式中陆面过程的一个改进   总被引：7，自引：5，他引：7  

赵鸣 《气象科学》2006,26(2):119-126

中尺度区域气候模式RIEMS中陆面过程使用BATS模式,其缺点是土壤内部过程较为简单,本文把10层土壤模式引入BATS,代替原来的二层土壤模式,并采用了TOPMODEL水文模式中的一些处理方法,使土壤温度、水文的计算更为合理,模拟二个个例,每个例均为夏季一个月的模拟,表明在降水、气压场、流场上均较原RIEMS模式为优,因而是对原RIEMS模式一个改进。  相似文献   

空间数据库引擎关键技术剖析   总被引：18，自引：3，他引：18  

李滨  王青山等 《测绘学院学报》2003,20(1):35-38

解决用户应用系统与空间数据库间的数据传输成为空间数据库能否得以充分利用的关键问题。在众多解决方案中，空间数据库引擎备受关注。文中介绍了空间数据库引擎的概念和基本功能，并着重对空间数据模型的建立、空间查询语言、空间数据索引、多用户编辑的数据一致性问题等空间数据库引擎的关键技术进行了剖析。  相似文献   

运用自相关谱计算薄互层砂岩厚度     

周志才  何樵登  金抒辛  李崇灿 《吉林大学学报(地球科学版)》2003,33(1):96-100

在分析以往“计算薄互层砂岩厚度”技术基础上，通过大量的正演模型及提取多种特征参数等工作，优选出对薄互层砂岩厚度表征良好的一类特征参数－自相关谱。在自相关谱中着重研究了3种规律性较好的特征参数，即自相关谱振幅（Amax)，第一零交叉时（t01)及三间隔逢迟振幅比（A3／Amax)。阐述了3个特征参数与薄层砂岩厚度（小于λ/4）的关系，给出了反演的计算方法，并利用关系函数进行了定量的反演计算，得到了较高精度的结果。  相似文献