Effects and removal of systematic errors in crosshole georadar attenuation tomography     

Hansruedi Maurer  Martin Musil 《Journal of Applied Geophysics》2004,55(3-4):261-270

We have developed an algorithm that allows crosshole georadar amplitude data contaminated with systematic errors to be tomographically inverted. The effects of the errors, which may due to variable antenna-borehole coupling, the groundwater table, and 3-D heterogeneities in the vicinity of one or more boreholes, are included in a series of transmitter and receiver amplitude-correction factors. Tests with synthetic georadar sections demonstrate that the new approach is capable of producing reliable attenuation information, even when large systematic errors are present in the amplitude data. Standard inversions of crosshole georadar data acquired within a highly complex alpine rock glacier yield distorted tomograms. In contrast the new approach results in geologically useful images.  相似文献   

北祁连玉石沟蛇绿岩形成于晚震旦世的SHRIMP年龄证据   总被引：45，自引：5，他引：45  

史仁灯  杨经绥  吴才来  J.WOODEN 《地质学报》2004,78(5):649-657

玉石沟蛇绿岩位于青藏高原东北缘的北祁连山中部 ,由地幔橄榄岩、堆晶辉长岩、辉绿岩、枕状熔岩以及夹杂在其中的硅质岩组成。地幔橄榄岩主要是方辉橄榄岩 ,其主要氧化物成分较为单一 ,具 L REE富集、Eu亏损的 U形 REE配分模式 ,亏损强不相容元素 ;枕状熔岩具典型 MORB特征 ,在构造判别图解上位于 MORB和 IAT区域 ,指示蛇绿岩可能形成于类似于洋中脊的构造环境 ,并受到火山弧岩浆作用的影响。堆晶辉长岩具明显的 Eu正异常 ,其锆石离子探针 (SHRIMP) 2 0 6 Pb/2 38U加权平均年龄为 5 5 0± 17Ma,Th/U值为 0 .5 3～ 1.85 ,大于0 .2 3,为岩浆成因锆石 ,其年龄代表辉长岩的成岩时代 ,推断玉石沟蛇绿岩形成于晚震旦世。  相似文献   

新疆博格达山分段及深浅构造转换关系   总被引：15，自引：1，他引：15  

李涛  王宗秀  周高志  柳永清  李寅 《地学前缘》2004,11(3):103-114

研究表明 ,天山及邻区自中生代以来一直处于热衰减状态 ,博格达山新生代再造山具有“冷隆升”性 ,盆山边界断裂多限于上地壳内 ,而非直通中地壳低速体甚至上地幔的“深大断裂”。造山带内的韧性剪切带是在古生代形成的 ,而不是再造山期的断裂 ,它对造山带隆升及盆山耦合无贡献 ,博格达山的隆升为复式背斜构造所支持。博格达山与准东的关系为背斜北翼与盆地平缓基底构成的挠曲构造 ,而不是被深大断裂分隔的断块。博格达山具有独特鲜明的分段性 ,造山带的两个弧形构造与新生代再生前陆盆地构成独特的“斜方对称”分布样式。以板条观点为指导 ,从盆山单元的平面配置关系和深浅构造转换关系入手 ,探讨了博格达山板内造山阶段的几何学和运动学分段性的成因 ,构建了盆山耦合模式  相似文献   

内蒙古"宝音图隆起"的归属讨论   总被引：5，自引：0，他引：5  

沈存利  陈志勇  常忠耀 《华北地质》2004,27(1):18-23

对比研究表明，内蒙古“宝音图隆起”和狼山地区的古元古代宝音图岩群与新太古代色尔腾山岩群都是由中低级变质的各种片岩、大理岩组成，一致的岩石组合和变质相暗示二者可能是等同物而不是两个岩群。以物探资料为据的构造研究也证实，“宝音图隆起”与狼山地区之间并无槽一台级的大型断裂构造分开，二者实为统一的构造整体而不是分属槽台，只因两侧被两条近于平行的NE向断裂围限，使其总构造线方向呈NE或NNE向而与色尔腾山的构造线不同。结论认为，“宝音图隆起”仍是华北陆块的一部分，不属于内蒙古一大兴安蛉地槽褶皱系。  相似文献   

贡嘎山东坡亚高山不同林地土壤水分特性与生态环境效应   总被引：2，自引：0，他引：2  

张保华  何毓蓉  周红艺  程根伟 《山地学报》2004,22(2):207-211

森林土壤水分特性，包括水分的渗透与蒸发、保持与贮存等对森林生态环境都有重要意义。本文研究了长江上游贡嘎山亚高山不同森林类型土壤的水分特征及其生态环境作用，结果表明：成熟林、过熟林土壤在储水、渗透、容水、蒸发和持水特性等多数方面利于保持和改善生态环境，次生或林分单一森林类型次之，林木皆伐后最差。研究区以成熟林和过熟林为主，生态环境保护较好。尽管该区与长江上游其它地区一样同具自然地理条件差、生态环境脆弱的特征，但由于该区森林植被和环境得到了有效保护，土壤水分特性好，促进了森林生态系统的良性循环，生态环境问题得到进一步改善。  相似文献   

Multifield coupling model and its applications for pile foundation in permafrost   总被引：2，自引：0，他引：2  

WU Yaping    ZHU Yuanlin  GUO Chunxiang  SU Qiang & MA Wei . School of Civil Engineering  Lanzhou Jiaotong University  Lanzhou  China  . State Key Laboratory of Frozen Soil Engineering  Cold  Arid Regions Environmental  Engineering Research Institute  Chinese Academy of Sciences  Lanzhou  China 《中国科学D辑(英文版)》2005,48(7)

In the construction of Qinghai-Tibet railway,to avoid diseases caused by frost heave and thaw col-lapse of frozen ground,besides the normal bridges over the rivers,a lot of dry bridge structures have been built to replace subgrade in the regions of high tem-perature and high ice content frozen soil.So,the problems on forming mechanism of bearing capacity of pile foundation in cold regions already become one of hot spot problems in frozen soil engineering.Freezing force and frost heave force ar…  相似文献   

Channel geometry of mountain streams in New Zealand     

Ellen E. Wohl  Andrew Wilcox 《Journal of Hydrology》2005,300(1-4):252-266

A dataset of 21 study reaches in the Porter and Kowai rivers (eastern side of the South Island), and 13 study reaches in Camp Creek and adjacent catchments (western side of the South Island) was used to examine downstream hydraulic geometry of mountain streams in New Zealand. Streams in the eastern and western regions both exhibit well-developed downstream hydraulic geometry, as indicated by strong correlations between channel top width, bankfull depth, mean velocity, and bankfull discharge. Exponents for the hydraulic geometry relations are similar to average values for rivers worldwide. Factors such as colluvial sediment input to the channels, colluvial processes along the channels, tectonic uplift, and discontinuous bedrock exposure along the channels might be expected to complicate adjustment of channel geometry to downstream increases in discharge. The presence of well-developed downstream hydraulic geometry relations despite these complicating factors is interpreted to indicate that the ratio of hydraulic driving forces to substrate resisting forces is sufficiently large to permit channel adjustment to relatively frequent discharges.  相似文献   

Geochemical Information Indicating the Water Recharge to Lakes and Immovable Megadunes in the Badain Jaran Desert   总被引：1，自引：0，他引：1  

CHEN Jiansheng  ZHAO Xi  SHENG Xuefeng  Wang Jiyang  GU Weizu  and CHEN Liang State Key Laboratory of Hydrology-Water Resources  Hydraulic Engineering  Hohai University  Nanjing  Jiangsu  E-mail: jschen@hhu.edu.cn Institute of Isotope Hydrology Research  Hohai University  Nanjing  Jiangsu Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing 《《地质学报》英文版》2005,79(4):540-546

1 Introduction The Badain Jaran Desert, located in western Inner Mongolia, China, has a unique landscape containing 144 lakes (72 of which are still watery) with a total water area of about 23 km2, and the world’s highest stationary sand dunes with a height between 200 m and 500 m. Much attention has been paid to the water recharge of the desert in the past decade. Investigations on the resources of water system there have been performed continuously since the early 1990s, which lead to th…  相似文献   

Analysis of village accessibility and its impact on land use dynamics in a mountainous province of northern Vietnam   总被引：5，自引：0，他引：5  

Jean-Christophe Castella  Pham Hung Manh  Suan Pheng Kam  Lorena Villano  Nathalie Rachel Tronche   《Applied geography (Sevenoaks, England)》2005,25(4):308-326

Surveys carried out in mountainous areas of northern Vietnam at research sites selected across a gradient of market integration, revealed strong relationships between the location of the village with respect to the national road network and the nature of its land-use systems, its poverty level and more generally its potential for development. We developed and tested in Bac Kan province a method to give an objective and quantitative definition of accessibility over a large geographic area. Accessibility maps integrated in a provincial GIS showed that despite recent improvements to the road network, some remote areas do not benefit from recent development.  相似文献   

贵州喀斯特山区墓地利用管理与耕地保护   总被引：1，自引：1，他引：1  

莫世江 《云南地理环境研究》2005,17(3):31-34

通过对贵州亮岩峰丛山地的墓地进行随机抽样调查和统计分析,显示出墓地在一定坡度上的特定地段有集中趋势;在对墓地选址与土层厚度进行显著性检验后表明:喀斯特地区土层厚度著性影响墓地分布。以至于绝大多数墓地集中分布在日照较好、排水畅通、土层较厚的阳坡山麓地带,以占用土层较厚的优质耕地为主。在现实的墓地利用管理实践中,实施统一规划、集中管理,建立有偿使用制度、严格用地指标,加强墓地绿化,实行墓地园林化建设等措施,以期综合性多元化开发利用墓地,有效保护耕地资源。  相似文献