龙门山构造带深部动力学过程与地表地质过程的耦合关系   总被引：1，自引：0，他引：1       下载免费PDF全文

颜照坤  王绪本  李勇  罗威  杨宜海  王兴建  邵崇建  闫亮 《地球物理学报》2017,60(7):2744-2755

发生在地球浅层的2008年汶川地震驱动了龙门山及前陆地区的地表同震垂向位移.根据冲断带-前陆盆地弹性挠曲模型理论,在进行弹性挠曲模拟反演的基础上,结合对深部地球物理特征(泊松比、电性结构)的分析,发现龙门山前陆盆地现今岩石圈有效弹性厚度(T_e)具有自东向西逐渐减薄的趋势,自川中地区的30~40 km减至龙门山地区的10~20 km.在对晚三叠世以来前陆盆地各阶段盆地结构进行刻画的基础上,进行弹性挠曲模拟反演,推断龙门山前陆盆地的前渊地区(四川盆地西部)岩石圈的T_e值自晚三叠世以来具有逐渐减薄的趋势.这可能与松潘一甘孜地块下方广泛存在的软流圈热物质对四川盆地西部岩石圈下部的长期加热而导致的熔融有关,反映了地球深部动力学过程与地球表层盆地演化之间的耦合关系.  相似文献   

Collapse risk of controlled rocking steel braced frames with different post‐tensioning and energy dissipation designs          下载免费PDF全文

Taylor C. Steele  Lydell D. A. Wiebe 《地震工程与结构动力学》2017,46(13):2063-2082

Controlled rocking steel braced frames (CRSBFs) are low‐damage self‐centring lateral force resisting systems. Previous studies have shown that designing the energy dissipation (ED) and post‐tensioning (PT) in CRSBFs using a response modification factor of R=8 can prevent collapse of structures during earthquakes beyond the design level. However, designers have unique control over the hysteretic behaviour of the system, even after the response modification factor is selected. Additionally, recent studies have suggested that CRSBFs could also be designed using R>8 while still satisfying performance limits. This paper examines how the response modification factor and the design of the ED and PT influence the collapse performance of CRSBFs with three and six storeys where collapse occurs because of over‐rotation of the base rocking joint. In addition, the influence of using an additional rocking joint above the base to mitigate higher‐mode forces is evaluated for a 12‐storey frame. A total of 18 different designs are considered for the three buildings using different ED and PT design parameters, including different response modification factors. A suite of 44 ground motions is scaled until at least 50% of the records cause collapse, and fragility curves are generated using the truncated incremental dynamic analysis curves. The results from two different assessment methodologies show that the parameters selected have a marked influence on the collapse performance of a CRSBF. Nevertheless, even CRSBFs designed using R>8 or without supplemental ED can have acceptably low probabilities of collapse, provided that the frame members are designed to remain elastic. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

贵州万人洞金矿电性特征及金矿找矿规律研究     

张西君  蒙应华  刘俊  屈念念  李家斌 《中国地质调查》2020,7(2):39-44

为探索万人洞金矿与物探电性特征之间的规律,拓宽万人洞金矿找矿思路,通过介绍万人洞金矿区地质、物性特征及可控源音频大地电磁测深法(controlled source audio magnetotelluric method,CSAMT)工作原理,利用CSAMT及物性测量方法,对万人洞金矿区电性结构特征进行综合研究,查明了研究区与金矿相关的地质体、构造、矿化蚀变等空间分布特征,总结出金矿物探找矿规律: 金矿产出部位位于物探低阻异常带,或高、低阻过渡渐变带上,经后期钻孔验证,方法有效可靠。研究成果为万人洞金矿区或相关矿区金矿找矿提供物探方案。  相似文献   

EFFECTS OF BIOKARSTIC PROCESSES ON THE DEVELOPMENT OF SOLUTIONAL RILLENKARREN IN LIMESTONE ROCKS     

Ll. FIOL  J. J. FORN S  A. GINS 《地球表面变化过程与地形》1996,21(5):447-452

  相似文献   

Accelerated sediment delivery to continental margins during post-orogenic rebound of mountain ranges     

Thomas Bernard  Hugh D. Sinclair 《Basin Research》2023,35(2):642-661

Changes in sediment flux to continental margins are commonly interpreted in terms of tectonic growth of topography or climatic change. Here, we show that variations in sediment yield from orogenic systems, previously considered as resulting from climate change, drainage reorganisation or mantle processes can be explained by intrinsic mechanisms of mountain belt/foreland basin systems naturally evolving during post-orogenic decay. Numerical modelling indicates an increase of sediment flux leaving the orogenic system synchronous with the cessation of deposition in the foreland basin and the transition from late syn- to post-orogenesis. Experiments highlight the importance of lithospheric flexure that causes the post-orogenic isostatic rebound of the foreland basin. Erosion of the rebounding foreland basin combined with continued sediment flux from the thrust wedge drives an acceleration in sediment outflux towards continental margins. Sediment budget records in natural settings such as the Northern Pyrenees or Western European Alps also indicate accelerated post-orogenic sediment delivery to the Bay of Biscay and Rhône Delta respectively. These intrinsic processes that determine sediment yield to continental margins must be accounted for prior to consideration of additional external tectonic or climatic controls.  相似文献   

The Deccan tholeiite lavas and dykes of Ghatkopar–Powai area,Mumbai, Panvel flexure zone: Geochemistry,stratigraphic status,and tectonic significance     

《Journal of Asian Earth Sciences》2014

Mumbai City, situated on the western Indian coast, is well known for exposures of late-stage Deccan pillow basalts and spilites, pyroclastic rocks, rhyolite lavas, and trachyte intrusions. These rock units, and a little-studied sequence of tholeiitic flows and dykes in the eastern part of Mumbai City, constitute the west-dipping limb of a regional tectonic structure called the Panvel flexure. Here we present field, petrographic, major and trace element and Sr–Nd isotopic data on these tholeiitic flows and dykes, best exposed in the Ghatkopar–Powai area. The flows closely resemble the Mahabaleshwar Formation of the thick Western Ghats sequence to the east, in Sr–Nd isotopic ratios and multielement patterns, but have other geochemical characteristics (e.g., incompatible trace element ratios) unlike the Mahabaleshwar or any other Formation. The flows may have originated from a nearby eruptive center, possibly offshore of Mumbai. Two dykes resemble the Ambenali Formation of the Western Ghats in all geochemical characteristics, though they may not represent feeders of the Ambenali Formation lavas. Most dykes are distinct from any of the Western Ghats stratigraphic units. Some show partial (e.g., Sr–Nd isotopic) similarities to the Mahabaleshwar Formation, and these include several dykes with unusual, concave-downward REE patterns suggesting residual amphibole and thus a lithospheric source. The flows and dykes are inferred to have undergone little or no contamination, by lower continental crust. Most dykes are almost vertical, suggesting emplacement after the formation of the Panvel flexure, and indicate considerable east–west lithospheric extension during this late but magmatically vigorous stage of Deccan volcanism.  相似文献