Continental accretion and incremental deformation in the thermochronologic evolution of the Lesser Caucasus     

《地学前缘(英文版)》2019,10(6):2189-2202

Apatite fission-track analysis and thermochronologic statistical modeling of Precambrian-Oligocenc plutonic and metamorphic rocks from the Lesser Caucasus resolve two discrete cooling episodes.Cooling occurred during incremental crustal shortening due to obduction and continental accretion along the margins of the northern branch of the Neotethys.(1) The thermochronometric record of a Late Cretaceous(Turonian-Maastrichtian) cooling/exhumation event,coeval to widespread ophiolite obduction,is still present only in a relatively small area of the upper plate of the Amasia-Sevan-Akera(ASA) suture zone,i.e.the suture marking the final closure of the northern Neotethys during the Paleogene.Such area has not been affected by significant later exhumation.(2) Rapid cooling/exhumation occurred in the Early-Middle Miocene in both the lower and upper plates of the ASA suture zone,obscuring previous thermochronologic signatures over most of the study area.Miocene contractional reactivation of the ASA suture zone occurred contemporaneously with the main phase of shortening and exhumation along the Bitlis suture zone marking the closure of the southern branch of the Neotethys and the ensuing ArabiaEurasia collision.Miocene collisional stress from the Bitlis suture zone was transmitted northward across the Anatolian hinterland,which was left relatively undeformed,and focused along preexisting structural discontinuities such as the eastern Pontides and the ASA suture zone.  相似文献   

基于时空不确定性的对流尺度集合预报效果评估检验   总被引：3，自引：0，他引：3  

马申佳  陈超辉  智协飞  何宏让  吴丹 《气象学报》2018,76(4):578-589

针对对流尺度天气系统的高度非线性特征和高分辨率模式预报结果存在时、空不确定性现象,以及当前邻域概率法主要考虑高分辨率预报结果的空间位移误差,而不能有效解决预报结果存在时间超前与滞后问题,将时间因素引入到邻域概率法中,结合一次强飑线过程进行对流尺度集合预报试验,并基于改进后的新型邻域概率法与分数技巧评分,对降水预报进行了不同时、空尺度的效果评估检验。结果表明:（1）邻域集合概率法和概率匹配平均法在极端降水的分数技巧评分远高于传统集合平均,弥补了集合平均对极端降水预报能力偏低的缺陷。（2）对于此类飑线过程的对流尺度天气系统而言,邻域半径为15—45 km的空间尺度能够改善降水位移误差的空间不确定性,并使其预报效果达到最优,其中15—30 km的邻域半径对于尺度更小的大量级降水事件预报能力更强。（3）对流尺度降水预报考虑时间尺度与降水强度存在着对应关系,不同时间尺度可以捕获到不同量级降水的时间不确定性。同时,时间尺度与空间尺度对于降水预报效果的影响是相互关联的。（4）改进的邻域概率法能够同时体现高分辨率模式预报结果在对流尺度降水事件上存在的时、空不确定性,实现了对流尺度降水在时、空尺度上的综合评估,并能为不同量级降水提供与其时、空尺度相匹配的概率预报结果。   相似文献   

Elastic response of catamaran wetdeck to liquid impact     

Alexander Korobkin 《Ocean Engineering》1998,25(8):687-714

The impact of an elastic plate onto the compressible fluid without free surface deformation is considered. The ability of the liquid volume to be deformed is geometrically limited which leads to severe impact conditions. The present analysis is focused on the stresses in the plate and the hydrodynamic loads under the impact. The motivation for this research comes from ship hydrodynamics, where the hulls of a catamaran restrict the liquid outflow and the water impacts onto the wetdeck. The influence of the air on the impact process is investigated. The analysis did not reveal any great advantage of utilizing the air-cushion effect or ejection of air into the water near the impact region to prevent high stresses in the elastic plate. It was found that in the problem considered, the stress peaks far from the plate centre and the one-mode approximation does not provide correct information about the stress level.  相似文献   

Significant load and green water on deck of offshore units/vessels     

B. Hamoudi  K.S. Varyani 《Ocean Engineering》1998,25(8):715-731

In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling.  相似文献   

Economics of a Baltic Sea sustainability approach     

Jrg Khn 《Limnologica》1999,29(3):346

Politics, economics and science interpret the concept of sustainability differently. The discussion distinguishes between economic, environmental and social sustainability. While advocates of economic sustainability assume that natural capital is substitutable by humanmade capital, policies for a sustainable development are questionable. The paper therefore highlights a regional case to show that sustainability is indivisible. Moreover, economics and policies serving Baltic sustainability need a new institutional network to manage the multispecies resource with participation of the social players and by addressing targets step by step. The findings are based on a simple ecological-economic model providing insights for the negotiation game for all players. In addition, multispecies resource management shows a strong hierarchy in both social actions and targets. Since sustainable development is an on-going, dynamic process, policy implementation and funding must also be continuous. Sustainable development therefore challenges the institutional sets for the process and its relations to local, regional and national policies.  相似文献   

Experimental evidence for flexibility of a building foundation supported by concrete friction piles     

M. D. Trifunac  S. S. Ivanov  M. I. Todorovska  E. I. Novikova  A. A. Gladkov 《Soil Dynamics and Earthquake Engineering》1999,18(3):375

This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (M_L=6.6, R=22 km), 1987 Whittier–Narrows (M_L=5.9, R=41 km), 1992 Landers (M_L=7.5, R=186 km), 1992 Big Bear (M_L=6.5, R=149 km), and 1994 Northridge (M_L=6.4, R=1.5 km) earthquake and its aftershocks (20 March: M_L=5.2, R=1.2 km; 6 December, 1994: M_L=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake.  相似文献   

节理岩体中地下洞室超挖预测   总被引：10，自引：2，他引：8  

吴继敏 《工程地质学报》1999,7(1):3-8

本文着重于岩体中洞室超挖-不稳定楔形体的预测。首先,论述洞室超挖的基本概念、主要原因及评价方法;其次分析和比较目前现有的针对洞室超挖的计算软件及其特征;然后介绍本文作者的计算软件;最后,简单介绍一个计算实例,即从野外地质调查着手,应用数理统计理论评价构成不稳定楔形体的主要地质参数及其模型,推导岩体中洞室超挖预测的一般公式;最后评价构成不稳定楔形体主要地质参数中的主要因素及次要因素,为节理岩体洞室防止超挖及其处理提供依据。  相似文献   

非规则网带断层地震数据的网格化   总被引：4，自引：0，他引：4  

张美根  乌达巴拉 《地球物理学进展》1999,14(1):69-77

非规则网地震勘探中,由解释人员解释出来的层位信息包括大量不规则分布的高程数据和断层构造的断点数据,因而其构造图成图的网格化是一件相当复杂而又难度较大的工作,本文较全面地研究了非规则网带断层地震数据的网格化过程（本文针对是正断层情况）,提出了一种快速实用的正方形网格化方法,经对实际资料处理证明,它能够适用于非常复杂的情况,并且处理效果理想。  相似文献   

基态位涡径向分布对浅水涡旋系统动力稳定性的影响分析          下载免费PDF全文

刘爽  钟玮  刘宇迪 《地球物理学报》2018,61(6):2207-2219

本文基于正压浅水模型,分析基态位涡（Potential Vorticity：PV）结构对热带气旋（Tropical Cyclone：TC）类涡旋系统稳定性及其波动特征的影响.通过引入基态PV结构参数：宽度δ（眼墙内外边界涡度发生陡变的半径长度之比）和中空度γ（眼心相对涡度与内核区域平均相对涡度之比）,设计具有相同基流最大切向风速和最大风速半径的170组不同基态PV环结构的敏感性试验,并讨论了不同基态PV结构下涡旋系统最不稳定波数（the most unstable wavenumber：MUWN）和系统最不稳定模态（the most unstable mode of System：MUMS）的特征频率及其不稳定增长率的大小.结果指出：当PV环较宽,系统表现为低波数最不稳定,相应的MUMS为低频波且增长率小;当PV环较窄,系统表现为高波数不稳定,且PV环越实最不稳定波数越高;当PV环窄且空时,MUMS均为中高频波动,且不稳定增长率随PV环的宽度变窄和中空度变空而明显增大.分析典型PV结构下系统演变特征可知,当PV环较宽,MUMS表现为具有平衡约束的低频波动的线性不稳定特征;当PV环趋向窄且空时,MUMS的平衡性约束趋向弱化,同时不稳定增长表现为明显的指数型增长.进一步讨论系统内部非对称结构的形成和传播机制发现,对于弱不稳定的PV环来说,低波数波最不稳定的特征波动具有典型涡旋Rossby波特征;而对于强不稳定的PV环来说,高波数不稳定的特征波动混合波性质明显.  相似文献   

文莱-沙巴盆地深水褶皱冲断带构造变形特征及成因机制          下载免费PDF全文

唐武  赵志刚  张功成  谢晓军  刘世翔  王一博  宋双  王龙  孙瑞  郭佳 《地球物理学报》2018,61(10):4281-4295

为揭示活动陆缘深水褶皱冲断带的特征及成因,本文利用地震和区域地质资料的综合分析,系统阐述了文莱—沙巴盆地深水褶皱冲断带的构造变形特征,并结合盆地演化动力学特点,探讨其构造变形机制及其对深水区油气成藏的影响.研究结果表明,文莱—沙巴盆地深水褶皱冲断带具有"垂向分期、平面分段"的特点,垂向上,以中中新统底界面为界可划分为下部（始新世-早中新世）和上部（中中新世-现今）两套逆冲褶皱冲断体系,其中下部逆冲褶皱冲断带的形成与古南海的俯冲作用密切相关,上部逆冲褶皱冲断带是中中新世以来三角洲前缘重力滑动与苏禄海扩张造成的区域挤压应力远程效应共同作用的结果,且苏禄海扩张造成的远程挤压效应主控平面上南北段褶皱冲断带变形的差异性,导致北段褶皱变形强度大于南段,具有背斜褶皱数量多、褶皱间距离短、逆冲断层倾角陡的特点,南段反之;且晚上新世以来北段深水区地层缩短量大于陆架区伸展量,两者之差为2~6 km,而南段两者相当,仅受三角洲前缘重力滑动影响.整个褶皱冲断带发育断弯、断展、断滑褶皱等3种断层相关褶皱以及叠瓦扇和冲起构造2种逆冲构造组合,是多期NW向挤压应力作用下形成的大型逆冲推覆构造,以前展式向盆地扩展.此外,由于中中新世以来逆冲断层的持续活动,研究区深水褶皱冲断带发育众多构造圈闭,油气成藏条件优越,且南段优于北段,靠近陆坡的近端优于远端,可作为勘探部署重点.  相似文献