上海现阶段主要沉降层及其变形特征分析   总被引：12，自引：0，他引：12  

张云  薛禹群  李勤奋 《水文地质工程地质》2003,30(5):6-11

以上海地质条件为基础，根据最近十几年分层标和含水层水位观测资料分析了上海地面沉降的主要沉降层，分析结果表明目前上海的主要沉降层是第五砂层。从第五砂层水位与时间的关系、变形与时间的关系和水位与变形的关系出发，结合室内实验的结果，指出第五砂层的变形特征是地下水位在一定范围内反复上升-下降时，变形以弹性为主、一般情况下则以塑性变形为主、应力应变关系为非线性以及存在蠕变变形。在建立地面沉降模型时必须考虑含水砂层的这些变形特点。  相似文献   

地下水资源特性及其合理开发利用   总被引：19，自引：3，他引：19  

张人权 《水文地质工程地质》2003,30(6):1-5

地下水资源具有以下重要特性:兼具可再生性与不可再生性,发育的系统性,以及随时间的变动性。可再生的补给资源,是理论上可持续利用的地下水资源;除了特定情况外,不可再生的储存资源只能借用而不能耗用。地下水资源发育的系统性,要求以含水系统或水文系统、而不是以含水层为单元进行地下水资源评价。由于土地利用方式的改变,地下水资源是随时间而变化的,需要根据变化情况进行再评价。根据可持续发展的理念,地下水资源评价应当遵循供水永续性和生态环境可承载性原则。地下水资源评价需要采用多种方法,相互校核,以提高其成果的信度。最后以河北平原为例,探讨了深层地下水的资源属性以及合理利用地下水的途径。  相似文献   

紫阳-岚皋地区碱中性岩地质特征及其含矿(铌钽)性研究   总被引：1，自引：0，他引：1  

邓盛波  王炜红  汪显均 《陕西地质》2003,21(2):19-26,32

陕西紫阳县至岚皋县一带，分布着东西长160余千米、南北宽20～40千米的古生代碱中性岩浆岩带。通过对碱中性岩浆岩的地质特征及其铌钽等稀有金属含矿性调查和研究，认为该岩浆岩带是本区重要的铌钽成矿区，碱中性岩浆岩是本区主要铌钽含矿岩体，碱中性岩具铌钽稀有金属矿化，伴镧铈稀土金属矿化。  相似文献   

老湾金矿床地球物理特征及找矿标志   总被引：4，自引：2，他引：4  

马长源  简新玲 《物探与化探》2003,27(2):83-87,100

老湾金矿是我国近年来探明的重要的大型构造蚀变岩型金矿床.金矿体(或矿脉群)、控矿构造、岩浆岩、赋矿地层、近矿热液蚀变带以及周围地质体之间存在某种物性差异,因而有明显的地球物理异常特征,构成了金矿床重要的地球物理找矿标志.作者试图在矿床地球物理特征研究的基础上,总结地球物理找矿标志,确定找矿勘查物探方法组合流程,以期配合、指导正在进行中的桐柏-大别山北坡金银成矿带的普查找矿工作.  相似文献   

基于遥感与GIS的20世纪90年代中国城镇用地时空特征   总被引：18，自引：1，他引：18  

田光进  刘纪远  庄大方  张增祥 《第四纪研究》2003,23(4):421-427

文章利用20世纪90年代初期、中期和末期全国1:100000土地利用动态变化数据提取城镇用地动态变化数据,利用单元自动机和人工神经网络模型对全国城镇用地进行了区划.在此基础上,研究了90年代两个阶段中国城镇用地时空格局.研究表明:90年代前5年东部沿海地区受经济高速发展和开放政策的影响,城镇用地扩展迅速,中西部地区城镇用地扩展较慢;90年代后5年国家加大了耕地资源保护力度,在政府宏观调控政策和耕地资源保护条例的影响下,东部沿海地区城镇用地扩展大幅回落,中部地区城镇扩展也有较大幅度回落,西部地区随着经济发展加快,城镇用地扩展回落较小.  相似文献   

中国西北叠合盆地的主要构造特征   总被引：7，自引：2，他引：7  

汤良杰  贾承造  金之钧  马宗晋 《地学前缘》2003,10(Z1):118-124

探讨了中国西北地区大型叠合含油气盆地的主要特征 ,研究表明 ,在中国西北叠合盆地发展演化过程中 ,构造变革和构造耦合起着主导作用。构造变革包括大地构造格局的转变、沉积区和剥蚀区的转换、盆地类型的转换、大型区域性不整合的出现以及发生盆地构造反转等 ,这种构造变革具有多期性。叠合盆地构造耦合的方式主要涉及深部和浅部构造的耦合和盆山耦合等。盆山转换、盆山过渡带深部浅部构造的耦合、盆地沉降与造山带隆升耦合以及不同方向构造的耦合 ,反映了盆山耦合的多样性和复杂性。中国西北叠合盆地构造特征主要表现为构造的分层性、分带性、分段性、交叉性以及区域构造应力场的多变性 ,喜马拉雅运动对于中国西北叠合盆地最后的构造改造以及构造定型起着重要的制约作用。  相似文献   

Changes in source parameters of foreshocks and aftershocks of the 2001 M_S=6.0 Yajiang, Sichuan, earthquake     

程万正  陈天长  魏娅玲  朱航 《地震学报(英文版)》2003,16(4)

Introduction An MS=6.0 earthquake occurred on February 23, 2001 in Yajiang county, Sichuan Province. The earthquake is located on the east of the southeast segment of the Litang-Dewu fault with strike of NW. Before the event, on February 14, an MS=5.0 earthquake took place nearly in the same place. In 1948 an MS=7.3 earthquake occurred on the northwestern segment of the Litang fault. The length of the surface rupture belt caused by the earthquake is 70 km, which extended from Litang to…  相似文献   

Recurrence characteristics of late-quaternary strong earthquakes on the major active faults along the northern border of Ordos block   总被引：1，自引：0，他引：1  

冉勇康  陈立春  杨晓平  韩竹军 《中国科学D辑(英文版)》2003,46(Z2)

Through study on trenches, analysis of recurrence characteristics and recurrence interval cluster/gap of strong earthquakes along the major active faults on the northern border of Ordos block, we found 62 paleoearthquakes that occurred in the late Quaternary, including 33 earthquakes occurring in the Holocene. The recurrence characteristics of the paleoearthquakes are different at three levels, segments, faults, and fault zones. The strong seismic sequence on the independent segments is mostly characterized by long- and short-interval recurrences, while that on the faults and in fault zone is characterized clearly by random and cluster recurrences. Results of the moving window test indicate that the probabilities of "temporal cluster or gap", caused by random coincidence as opposed to intersegment contagion, are 64% and 70% for the Serteng piedmont fault and for the south-border fault of Wula Mountains, respectively, no clear interaction among the segments of each fault; while the probability is 26.8% for the whole fault zone, suggesting a clear interaction among the faults of this fault zone. These recurrence characteristics may imply an effect of the entire block motion on the recurrence of strong earthquakes. Moreover, the elapsed time for the Wujumeng Pass-Dongfeng Village segment of Serteng piedmont fault and the Tuzuo Banner-Wusutu and the Hohhot segments of Daqingshan piedmont fault has exceeded the average recurrence interval, hence these three segments may be the possible places for future strong earthquakes.  相似文献   

Geomechanical Properties of Shear Zones in the Eastern Aar Massif,Switzerland and their Implication on Tunnelling     

S. Laws  E. Eberhardt  S. Loew  F. Descoeudres 《Rock Mechanics and Rock Engineering》2003,36(4):271-303

Summary ¶Rock zones containing a high fracture density and/or soft, low cohesion materials can be highly problematic when encountered during tunnel excavation. For example in the eastern Aar massif of central Switzerland, experiences during the construction of the Gotthard highway tunnel showed that heavily fractured areas within shear zones were responsible for overbreaks in the form of chimneys several metres in height. To understand and estimate the impact of the shear zones on rock mass behaviour, knowledge concerning the rock mass strength and deformation characteristics is fundamental. A series of laboratory triaxial tests, performed on samples from granite- and gneiss-hosted shear zones revealed that with increasing degree of tectonic overprint, sample strength decreases and rock behaviour shows a transition from brittle to ductile deformation. These trends may be explained by increasing fracture densities, increasing foliation intensity, increasing thickness of fine-grained, low cohesion fracture infill, and increasing mica content associated with the increasing degree of tectonic overprint. As fracture density increases and the influence of discrete, persistent discontinuities on rock mass strength decreases, behaviour of the test samples becomes more and more representative of rock mass behaviour, i.e. that of a densely fractured continuum. For the purpose of numerical modeling calculations, the shear zones may be subdivided with respect to an increasing fracture density, foliation intensity and mica content into a strongly foliated zone, a fractured zone and a cohesionless zone, which in turn exhibit brittle, brittle-ductile and ductile rock mass constitutive behaviour, respectively.Received December 17, 2001; accepted January 9, 2003 Published online April 29, 2003  相似文献   

Weather as a Chronic Hazard for Road Transportation in Canadian Cities   总被引：2，自引：1，他引：2  

Jean Andrey  Brian Mills  Mike Leahy  Jeff Suggett 《Natural Hazards》2003,28(2-3):319-343

Inclement weather creates a chronic hazard for Canadian travellers. Past studies indicate that road collision rates increase during precipitation, although the magnitude of theincrease varies from study to study, partly as a result of variations in weather and driving conditions,but also because of differences in methods. The goal of the current study is to improve ourunderstanding of the links between weather and travel risk in mid-sized Canadian cities by using astandardized method for analyzing data from six cities with different climates: Halifax-Dartmouth,Ottawa, Québec, Hamilton, Waterloo Region, and Regina. The study has four interrelated objectives: (1) Toconduct a sensitivity analysis to determine the extent to which risk estimates vary depending onthe criteria used to define precipitation events and `normal' conditions; (2) To compare therelative risk of collision and injury during precipitation relative to `normal' conditions; (3) Todetermine the extent to which weather-related risks vary fordifferent Canadian cities; and (4) To explore any differences in collision characteristics between events and controls, especially as theyvary from city to city. Results are based on a matched-pair analysis, using six-hour time blocks over afour-year period, 1995 to 1998. Results indicate only modest sensitivity to the criteria used to define precipitation events and `normal' conditions. On average, precipitation is associated with a 75 percentincrease in traffic collisions and a 45 percent increase in related injuries, as compared to `normal'seasonal conditions, but risk levels vary depending on the characteristics of the weather event.Both sensitivity to specific weather conditions and weather-related accident profiles vary from city tocity in ways that are not easily explained.  相似文献