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381.
Ordos block was squeezed by the Qinghai-Tibetan block and North China block, and the tectonic activity was intense. In the periphery of Ordos block, there was a series of folds zones and compressed faults with complicate structures. This paper used three-phase data of 1980,1990 and 2014 to calculate vertical velocity of Northwestern margin of Ordos and the analytical results indicated that ① the Hetao basin between the rise of Yinshan fault block and Ordos fault block showed relatively subsidence, in which Linhe basin was the most evident and the subsidence rate was about 2-4mm/a. The subsidence rate of Jartai -Yinchuan rift zone on the western margin of Ordos block was about 2mm/a; ② the whole testing zone exhibited the evident inherited movement characterized by mountain rise and basin subsidence; ③the two leveling section through the northern margin fault and Dengkou-Benjing fault showed that the difference between vertical velocities on two sides of the fault was less than 0.5mm/a. 相似文献
382.
利用双差定位方法,对2013年10月—2016年12月乳山震群进行重定位,并计算乳山震群中地震集中活动区域b值,分析其深度分布变化。结果显示:地震重定位后表现为近NW向集中分布;b值在震源深度7.4 km上下最小,反映该深度处应力最强;乳山震群b值并不随震源深度增大而呈系统性减小变化,且深度10.2 km以下无有效b值,进一步证实该震群近NW向发震断裂的存在。根据b值随深度的变化特征,推测断裂活动的高应力区域集中在6.5—10.2 km深度范围内,断裂活动在深度7.4 km处应力最强,且水平分布最广;相比上下两侧地壳介质b值在5.5—6.2 km深度层位明显增大,反映该深度层位介质性质存在明显差异。 相似文献
383.
Hsin-Ting?Su Sai?Hung?CheungEmail author Edmond?Yat-Man?Lo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):1147-1162
In flood risk management, the divergent concept of resilience of a flood defense system cannot be fully defined quantitatively by one indicator and multiple indicators need to be considered simultaneously. In this paper, a multi-objective optimization (MOO) design framework is developed to determine the optimal protection level of a levee system based on different resilience indicators that depend on the probabilistic features of the flood damage cost arising under the uncertain nature of rainfalls. An evolutionary-based MOO algorithm is used to find a set of non-dominated solutions, known as Pareto optimal solutions for the optimal protection level. The objective functions, specifically resilience indicators of severity, variability and graduality, that account for the uncertainty of rainfall can be evaluated by stochastic sampling of rainfall amount together with the model simulations of incurred flood damage estimation for the levee system. However, these model simulations which usually require detailed flood inundation simulation are computationally demanding. This hinders the wide application of MOO in flood risk management and is circumvented here via a surrogate flood damage modeling technique that is integrated into the MOO algorithm. The proposed optimal design framework is applied to a levee system in a central basin of flood-prone Jakarta, Indonesia. The results suggest that the proposed framework enables the application of MOO with resilience objectives for flood defense system design under uncertainty and solves the decision making problems efficiently by drastically reducing the required computational time. 相似文献
384.
Oceanic plate subduction history in the western Pacific Ocean: Constraint from late Mesozoic evolution of the Tan-Lu Fault Zone 总被引:4,自引:0,他引:4
Guang Zhu Cheng Liu Chengchuan Gu Shuai Zhang Yunjian Li Nan Su Shiye Xiao 《中国科学:地球科学(英文版)》2018,61(4):386-405
The NE- to NNE-striking Tan-Lu Fault Zone (TLFZ) is the largest fault zone in East China, and a typical representative for the circum-Pacific tectonics. Its late Mesozoic evolution resulted from subduction of the Paleo-Pacific Plate, and can be used for indication to the subduction history. The TLFZ reactivated at the end of Middle Jurassic since its origination in Middle Triassic. This phase of sinistral motion can only be recognized along the eastern edge of the Dabie-Sulu orogenis, and indicates initiation of the Paleo-Pacific (Izanagi) Plate subduction beneath the East China continent. After the Late Jurassic standstill, the fault zone experienced intense sinistral faulting again at the beginning of Early Cretaceous under N-S compression that resulted from the NNW-ward, low-angle, high-speed subduction of the Izanagi Plate. It turned into normal faulting in the rest of Early Cretaceous, which was simultaneous with the peak destruction of the North China Craton caused by backarc extension that resulted from rollback of the subducting Izanagi Plate. The TLFZ was subjected to sinistral, transpressive displacement again at the end of Early Cretaceous. This shortening event led to termination of the North China Craton destruction. The fault zone suffered local normal faulting in Late Cretaceous due to the far-field, weak backarc extension. The late Mesozoic evolution of the TLFZ show repeated alternation between the transpressive strike-slip motion and normal faulting. Each of the sinistral faulting event took place in a relatively short period whereas every normal faulting event lasted in a longer period, which are related to the subduction way and history of the Paleo-Pacific Plates. 相似文献
385.
Slip boundary condition is commonly utilized to model elastic wave propagation through layered earth media. The same approach is used here to characterize acoustic wave propagation along a cased borehole with various cement bond conditions. By modeling the cement layer between casing and formation as a viscoelastic slip interface with complex coupling rigidity parameters, one can not only reduce the complexity in the classical elastic wave modeling of the problem, but also efficiently model various complicated wave phenomena that are difficult for the existing modeling. More specifically, the new theory can well describe the effect of the cement bond condition change and the location of the change (i.e., whether it is in the first interface between casing and cement, or the second interface between cement and formation) on the acoustic waves, demonstrating the good modeling capability and predicting power. Application of the theory to field data shows that the theory can correctly model the acoustic wave characteristics and interpret the cement bond condition, thus providing a useful fundament theory for casing bond evaluation using acoustic logging. 相似文献
386.
387.
Prediction of 3D size and shape descriptors of irregular granular particles from projected 2D images
Acta Geotechnica - Macroscopic mechanical properties of granular materials are closely related to particle morphology. For practical reasons, the morphological features are commonly examined from... 相似文献
388.
对山东及邻区中强以上地震的双震现象进行了研究,结果是:M4.0现象以上中等地震双震,主要集中在渤海海峡和邢台地区及其构造附近;M5.0级以上中强震双震,主要分布在渤海海峡、邢台、临沂、菏泽这些历史和现今7级以上强震震中区附近。分析认为:双震现象可能主要与上地幔隆起、断层发育、构造复杂和高应力背景有关。 相似文献
389.
The drainage evolution and valley development of the Jinsha River is an important issue constantly concerned by researchers in geology and geomorphology. Despite hundreds of years of research, there is a big dispute on the formation time and the evolution process of the fluvial valley. Fluvial terraces are very important geomorphic markers for studying the formation and evolution of the fluvial valley. Through field investigation combined with Electron Spin Resonance (ESR) dating, we confirmed that 5 fluvial terraces were formed, and then preserved, along the course of the Jinsha River near the Longjie, which are all strath terraces. Among them, T5 developed on the base rock, with an age of (78±12) ka; all T4~T1 developed on the lacustrine sediments, named Longjie Group by Chinese, with an age of (29±1.4) ka, (26±2.4) ka, (23±1.4) ka, (18±1.7) ka, respectively. Compared with the global and regional climate change history, the terraces are all the result of the river responding to the climate change. T5 formed at MIS 5/4, and T4~T1 formed at the period of regional climate fluctuation. The relationship of terraces and the Longjie Formation, combined with sedimentary characteristics analysis demonstrate that the Longjie Formation is landslide dammed lake sediment. The landslide and blocking events.seriously influenced the valley evolution, inhibiting the river incising, and making the valley evolution defer to the mode of “cut-landside-damming-fill-cut” in the period of Late Pleistocene. Synthesized studies of the terraces and the correlative sediments indicate that the formation of the Jinsha River valley may have begun in the late Early Pleistocene. 相似文献
390.
为探讨松辽盆地北部林西组地球化学特征、沉积环境及构造背景,对该区黑富地1井所钻遇的上二叠统林西组暗色泥质板岩进行主量元素、微量元素和稀土元素测试分析,结果表明:样品主量元素平均质量分数SiO2为65.05%、Al2O3为17.23%、CaO为2.58%、Na2O为2.84%、K2O为3.29%,K2O/Na2O值为0.20~3.48,A12O3/(CaO+Na2O)值为0.41~8.01;稀土元素w(∑REE)值介于80.68×10-6~215.59×10-6之间,平均值为173.41×10-6,δEu值介于0.61~0.88之间,平均值为0.70,表现为Eu的负异常,δCe值介于0.91×10-6~1.01×10-6之间,为微弱的Ce负异常,LREE富集,HREE亏损;微量元素以亏损Nb、Ta、Sr,相对富集Rb、Ba、La、Ce、Pb、Nd、Sm为特征。样品元素分析和物源w(TiO2)-w(Ni)、La/Th-w(Hf)等判别图解表明,林西组沉积物源具有多样性,主要来源于上地壳长英质物源,还有少量来自中、基性岩火成岩物源区。样品微量元素标准化蛛网图,稀土元素球粒陨石标准化配分模式图,K2O/Na2O-w(SiO2)、Th-Co-Zr/10、F2-F1构造背景判别图及地球化学参数对比结果表明,松辽盆地北部林西组物源构造背景主要为活动大陆边缘和大陆岛弧,可能形成于靠近大陆岛弧的活动大陆边缘构造背景。林西组应形成于海陆过渡相到陆相环境,水体由半咸水逐渐转变为淡水。 相似文献