藏东拉荣斑岩钨钼矿床辉钼矿Re- Os定年及地质意义   总被引：3，自引：0，他引：3  

刘俊  祝向平  李文昌  王保弟  董宇  杨富成  杨后斌  吴江华 《地质学报》2019,93(7):1708-1719

拉荣钨钼矿床位于类乌齐-左贡成矿带的东南部,是藏东地区发现的首例大型斑岩型钨钼矿床。其成矿地质背景尚缺乏成矿年龄制约。本文对拉荣矿床含矿石英脉中的辉钼矿进行Re-Os定年,6件样品的模式年龄集中于91.5±1.3～92.3±1.3 Ma,其加权平均年龄为91.8±0.5 Ma,等时线年龄为90.6±2.1 Ma,表明拉荣钨钼矿床成矿时代为晚白垩世。辉钼矿样品的Re含量为53.0×10~(-6)～86.1×10~(-6),表明成矿物质具有壳幔混源的特征。拉荣钨钼矿床成矿年龄指示了班公湖-怒江构造带北东侧类乌齐-左贡成矿带内存在一期晚白垩世的钨多金属成矿事件,成矿作用发生于拉萨-羌塘地体碰撞造山阶段。  相似文献   

Evaluation of displacement‐based vulnerability assessment methodology using observed damage data from Christchurch          下载免费PDF全文

S. R. Uma  Rajesh P. Dhakal  Mostafa Nayyerloo 《地震工程与结构动力学》2014,43(15):2319-2339

On 22 February 2011, Christchurch City experienced a destructive magnitude (Mw) 6.2 aftershock following the main event of magnitude (Mw) 7.1 on the 4 September 2010. Severe damage was inflicted on the building stock, particularly within the central business district (CBD) of Christchurch. The strong motion stations around the CBD region and extensive building damage survey information from the Christchurch City Council provided a unique opportunity to calibrate a theoretical regional vulnerability assessment model developed and refined to be applicable for New Zealand (NZ) buildings. In this study, data from the building safety evaluation survey conducted by Christchurch City Council are synthesised and processed to extract details on building typologies in the CBD region and the colour tagging assigned to each building depending on the degree of damage. A displacement‐based framework is used to carry out vulnerability assessment for Christchurch buildings to estimate damage sustained under the recorded ground motions in the February event. As the damage survey indicators were ‘colour tags’, a mapping scheme has been explored to link the observed colour tagging damage statistics with ‘drift‐based damage limit states’ adopted in the theoretical approach. A sensitivity analysis is carried out to calibrate the mapping scheme, which can provide estimates of proportions of buildings likely to fall in different colour regimes when used in conjunction with the proposed vulnerability assessment methodology. It is shown that the methodology is reasonably robust, thereby increasing the confidence in using this approach to predict seismic vulnerability of building stock in NZ. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Impacts of post‐glacial rebound on landslide spatial distribution at a regional scale in northern Iceland (Skagafjörður)          下载免费PDF全文

Etienne Cossart  Denis Mercier  Armelle Decaulne  Thierry Feuillet  Helgi Páll Jónsson  Þorsteinn Sæmundsson 《地球表面变化过程与地形》2014,39(3):336-350

In de‐glaciated areas, para‐glaciation (i.e. the conditioning of landscapes by prior glaciation) has often been considered a major predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). Hitherto, the relative impacts of para‐glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically. We examine Skagafjörður area (northern Iceland) where landslides are widespread (at least 108 were mapped in an area of c. 3000 km²). We compare the role of para‐glaciation (debuttressing, influence of post‐glacial rebound) with that of classic factors (topography, lithology, etc.) in landslide occurrence and location, using a spatial analysis based on a chi‐square test. On the one hand, the results highlight that landslides are over‐represented in areas where post‐glacial rebound was at its maximum, with a stronger concentration of landslides in the northern part of the fjord. On the other hand, the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing. Tschuprow coefficient highlights that the influence of post‐glacial rebound on landslide location is higher than the combined influence of slope gradient, curvature or geological structure. This result is supported by our initial evidence for the timing of landslides in the area: most landslides occurred during the first half of the Holocene, and a period of hillslope instability was initiated when the post‐glacial uplift was at its maximum. Finally, the mechanisms that link post‐glacial rebound and landsliding as well as the geomorphic impacts of landslides, are discussed. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Seismic performance evaluation of high‐voltage disconnect switches using real‐time hybrid simulation: II. Parametric study          下载免费PDF全文

Selim Günay  Khalid M. Mosalam 《地震工程与结构动力学》2014,43(8):1223-1237

This paper presents the results of a parametric study that consists of real‐time hybrid simulation tests of electrical insulator posts on a smart shaking table. A companion paper presents the details of the development and validation of the real‐time hybrid simulation system used for conducting the tests of this parametric study. The purpose of the parametric study presented in this paper is to evaluate the effect of support structure damping and stiffness on the response of disconnect switches with two different insulator materials, namely porcelain and polymer insulator posts. Various global and local response parameters including accelerations, forces, displacements, and strains are considered in this evaluation. The data obtained from the conducted tests show that the maximum insulator response corresponds to the case where the support structure frequency is close to the insulator frequency. An incorporated evaluation of all the response parameters indicates that the stiff support structures constitute the most suitable configuration for both material types of the tested insulator posts. It is also observed that support structure damping has an effect on the response of both insulator types. However, this effect is secondary compared with the effect of support structure stiffness. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

全球早古生代造山带(Ⅰ):碰撞型造山   总被引：6，自引：0，他引：6  

李三忠  杨朝  赵淑娟  李玺瑶  郭玲莉  余珊  刘鑫  索艳慧  兰浩圆 《吉林大学学报(地球科学版)》2016,46(4):945-967

自新元古代罗迪尼亚超大陆裂解以来,早古生代是板块构造运动活跃时期,具有板块运动速度较快、构造格局不稳定、块体之间相互作用复杂多变等特征,造山带演化极其复杂,导致全球早古生代古大陆重建现今仍较模糊。特别是,早古生代末450~400 Ma存在全球性准同时的造山运动,已经出现俯冲增生、碰撞、陆内3种类型的全球尺度造山带。本文侧重论述全球早古生代碰撞类型造山带的特征,总结典型碰撞造山带最新的年代学、变质、变形和岩浆作用特征及其时空分布。早古生代全球碰撞型造山带主要分布在南半球的泛非造山带和北半球的加里东期造山带,分别与南方冈瓦纳大陆和北方劳俄古陆的初步集结密切相关,早古生代碰撞造山主要体现在大陆块之间的碰撞作用为特征。这些早古生代碰撞造山带具有近似的碰撞年龄,大致相同的演化过程。其中,南方大陆主体碰撞完成于540 Ma,而北方大陆主体集结完成于420 Ma,从全球构造意义上可能意味着全球一个420~400 Ma的超大陆初步形成。  相似文献   

Retrofit of reinforced concrete frames with buckling‐restrained braces          下载免费PDF全文

Christoph Mahrenholtz  Pao‐Chun Lin  An‐Chien Wu  Keh‐Chyuan Tsai  Shyh‐Jiann Hwang  Ruei‐Yan Lin  Muhammad Y. Bhayusukma 《地震工程与结构动力学》2015,44(1):59-78

Damage to buildings observed in recent earthquakes suggests that many old reinforced concrete structures may be vulnerable to the effects of severe earthquakes. One suitable seismic retrofit solution is the installation of steel braces to increase the strength and ductility of a building. Steel bracings have some compelling advantages such as their comparatively low weight, their suitability for prefabrication, and the possibility of openings for utilities, access, and light. The braces are typically connected to steel frames that are fixed to the concrete structure using post‐installed concrete anchors along the perimeter. However, these framed steel braces are not without some disadvantages such as heavier steel usage and greater difficulties during the installation. Therefore, braces without steel frames appear to be an attractive alternative. In this study, braces were connected to gussets furnished with anchor brackets, which were fixed by means of a few post‐installed concrete anchors. The clear structural system and the increased utilization of the anchors allowed the anchorage to be designed precisely and economically. The use of buckling‐restrained braces (BRBs) provides additional benefits in comparison with conventional braces. BRBs improve the energy dissipation efficiency and allow the limitation of the brace force to be taken up by the highly stressed anchorage. Cyclic loading tests were conducted to investigate the seismic performance of BRBs connected with post‐installed anchors used to retrofit reinforced concrete frames. The tests showed that the proposed design method is feasible and increases strength as well as ductility to an adequate seismic performance level. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)          下载免费PDF全文

Aurélia Hubert‐Ferrari  Meriam El‐Ouahabi  David Garcia‐Moreno  Ulaş Avşar  Sevgi Altınok  Sabine Schmidt  Nathalie Fagel  M. Namık Çağatay 《Sedimentology》2017,64(5):1322-1353

Deltas contain sedimentary records that are not only indicative of water‐level changes, but also particularly sensitive to earthquake shaking typically resulting in soft‐sediment‐deformation structures. The Kürk lacustrine delta lies at the south‐western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re‐evaluates water‐level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic‐reflection profiles and side‐scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water‐level changes provides a temporal framework for the depositional record. In addition to the common soft‐sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake‐induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (¹³⁷Cs and ²¹⁰Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X‐ray imagery, X‐ray diffraction, loss‐on‐ignition, grain‐size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post‐seismic sediment reworking of earthquake‐triggered landslides.  相似文献   

Post‐repair effect of column jackets on aftershock fragilities of damaged RC bridges subjected to successive earthquakes          下载免费PDF全文

Jong‐Su Jeon  Reginald DesRoches  Do Hyung Lee 《地震工程与结构动力学》2016,45(7):1149-1168

In light of recent earthquakes, structures damaged during an initial seismic event (mainshock) may be more vulnerable to severe damage and collapse during a subsequent event (aftershock). In this paper, a framework for the development of aftershock fragilities is presented; these aftershock fragilities define the likelihood that a bridge damaged during an initial event will exhibit a given damage state following one or more subsequent events. The framework is capable of (i) quantifying the cumulative damage of unrepaired bridges subjected to mainshock–aftershock sequences (effect of multiple earthquakes) and (ii) evaluating the effectiveness of column repair schemes such as steel and fiber‐reinforced‐polymer jackets (post‐repair effect of jackets). To achieve this aim, the numerical model of repaired columns is validated using existing experimental results. A non‐seismically designed bridge is chosen as a case study and is modeled for three numerical bridge models: a damaged (but unrepaired) bridge model, and two bridge models with columns repaired with steel and fiber‐reinforced polymer jackets. A series of back‐to‐back dynamic analyses under successive earthquakes are performed for each level of existing damage. Using simulated results, failure probabilities of components for multiple limit states are computed for each bridge model and then are used to evaluate the relative vulnerability of components associated with cumulative damage and column repair. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

桩端后注浆浆液上返高度的理论研究   总被引：1，自引：0，他引：1  

张忠苗  邹健  刘俊伟  贺静漪 《岩土力学》2010,31(8):2535-2540

在幂律型浆液平板窄缝流动模型的基础上,推导出了桩端后注浆浆液上返高度的计算公式。并对上返高度随注浆压力、桩埋深、桩径、泥皮厚度的变化情况进行计算分析,分析结果表明,在其他条件一定时,变形模量越大的土层,浆液上返高度越小;注浆压力越大,浆液上返高度越大;桩埋深越大,浆液的上返高度越小;桩侧泥皮越厚,浆液的上返高度越大。通过工程实例验证了本文计算结论的适用性。  相似文献   

The postal-geographical location: the notion and measurement algorithm (exemplified by the postal network of Siberia in the early 20th century)     

V.I. Blanutsa 《Geography and Natural Resources》2010,31(4):308-316

An analysis is made of the problems, approaches and methods in the study of the economic-geographical location. The term “postalgeographical location” is suggested. The concept of the location of a settlement in the postal network is formulated. The algorithm has been developed for measuring the postal-geographical location. Results from assessing the location of settlements in Siberia's postal network are presented for the year 1910.  相似文献