Insights on the kinematics of deep-seated gravitational slope deformations along the 1915 Avezzano earthquake fault (Central Italy), from time-series DInSAR     

M. Moro  M. Saroli  C. Tolomei  S. Salvi 《Geomorphology》2009,112(3-4):261-276

Small meandering channels of about 1 m wide on an intertidal mudflat in the Westerschelde estuary the Netherlands) were studied with the aim to improve understanding of the effect of highly cohesive bed and bank sediment on channel inception and meander geometry and dynamics. The study is supported by experiments and modelling. The estuarine meandering channels are less dynamical than alluvial meandering rivers, and the dynamics are more localised. Moreover, the high thresholds for bed sediment erosion and for bank failure lead to two processes, uncommon in larger rivers, that cause most of the morphological change. First, the beds of the channels are eroded by backward migrating steps under hydraulic jumps, while the remainder of the bed surface along the channel is hardly eroded. Second, channel banks erode i) where eroding steps locally cause undercutting of otherwise stable channel banks and ii) in very sharp bends where the flow separates from the inner-bend channel boundary and impinges directly on the bank on the opposite side of the channel. Further morphological change is probably induced by rainfall splash erosion and by storm waves that weaken the mud, and by large mud fluxes from the estuary. The steps were successfully reproduced in laboratory flume experiments. An existing model for step migration predicted celerities consistent with field and laboratory observations and demonstrated a strong dependence on the threshold for erosion. Bank stability models confirm that banks and steps only fail when undercut and weakened by waves, rain or excess pore pressure in agreement with observations. The effects of a high threshold for bank erosion was implemented in an existing meander simulation model that reproduced the observed locations of bank erosion somewhat better than without the threshold, but flow separation and its effect on meander bends remains poorly understood.  相似文献   

Curvature analysis as a tool for subsidence-related risk zones identification in the city of Tuzla (BiH)   总被引：1，自引：0，他引：1  

Francesco Stecchi  Marco Antonellini  Giovanni Gabbianelli   《Geomorphology》2009,107(3-4):316-325

Shallow Miocene salt deposits located below the city of Tuzla (BiH) have been exploited during the last 60 years by means of wells extracting salt-saturated groundwater brines. The massive extraction activities have led to severe subsidence accommodated by collapse and strain localization. Surface topography and geomorphology have been influenced and modified by several faults and fractures.A series of sequential topographical survey data collected during the last 50 years have been used to obtain the total subsidence envelope surface. In order to analyze the salt dissolution-related morphological development of the Tuzla topography and to identify the location of faults and fractures in the deformed area, we applied curvature analysis to the subsidence surface by means of two different analytical methods: the directional, two-dimensional curvature and the analytic Gaussian curvature. The comparison of the curvature maps with those of surface fractures visible in the area shows a good spatial agreement between the directional curvature and fracture intensity, whereas the subsurface normal faults are more evident in the Gaussian curvature maps.  相似文献   

曲线坐标系下的块体运动与应变模型研究          下载免费PDF全文

汪建军  许才军 《地球物理学报》2009,52(11):2721-2728

本文建立了顾及地球扁率和局部切标架随点变化特性的椭球坐标系下的刚体运动模型和块体运动与应变模型,以及球坐标系下顾及局部切标架随点变化特性的严密的块体运动与应变模型,分析了球坐标系下块体运动与应变模型及椭球坐标系下的块体运动与应变模型间的差异;通过计算具体讨论了地球扁率和曲线坐标系的局部切标架随点变化特性对欧拉矢量与应变张量的影响.结果表明：地球扁率对刚体欧拉矢量和应变参数的影响甚小,具体计算时可以不予考虑,但曲线坐标系的局部切标架随点变化特性对两者的影响较大,在建模过程中需要顾及,常用的Savage模型需要修正.  相似文献   

The Dynamic Characteristics of Strain Fields and Crustal Movement before the Wenchuan Earthquake （ Ms = 8.0）     

Jiang Zaisen  Wu Yanqiang  Fang Ying  Li Peng  Wang Wuxing 《中国地震研究》2009,23(3):257-265

In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake (M_S=8.0) using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmenshan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain (2004～2007) is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone.  相似文献   

大步长单程波算子相位积分实现方式初探   总被引：3，自引：3，他引：0       下载免费PDF全文

武威  刘洪 《地球物理学进展》2009,24(1):137-144

大步长单程波算子是穿过厚层的单程波算子的积分,在理论上它可以通过频率波数域表达式和波数域到空间域变换来实现,目前,通过李代数积分和指数映射的研究,已经导出频率波数域表达式,需要研究波数域到空间域变换的实现方式,波数域到空间域的变换可以通过鞍点法和相位积分来实现,本文研究了相位积分的三种实现途径:分裂方法、相移加插值方法和佳格点方法,在相移加插值方法中提出一种波场"角度域插值"的插值方法.  相似文献   

Formative conditions and sedimentary structures of sandy 3D antidunes: an application of the gravel step‐pool model to fine‐grained sand in an experimental flume     

Miwa Yokokawa  Kazuyoshi Hasegawa  Satoru Kanbayashi  Noritaka Endo 《地球表面变化过程与地形》2010,35(14):1720-1729

Antidunes and their sedimentary structures can be useful in reconstructing paleo‐hydraulic conditions, especially for large discharge events. However, three‐dimensional (3D) antidunes in sand‐sized sediments have not yet been studied extensively, as compared to either two‐dimensional (2D) antidunes or antidunes in gravel‐sized sediments. In this study, we estimated formative conditions of gravel step‐pool morphologies and applied them to the formation of 3D antidunes over a sand bed. Formative conditions are expressed in terms of a relationship between the water discharge per unit width and the bed slope. Flume experiments demonstrated that 3D mound‐like antidune configurations and their associated internal sedimentary structures could be preserved. Internal sedimentary structures were characterized by shallow lens‐like structures whose bases were erosional. Although gently‐dipping concave‐upward lamination was dominant, convex‐upward lamination was occasionally observed. The dimensions of lenticular lamina‐sets can be used to estimate antidune geometry. Thus if 3D antidunes can be interpreted in the stratigraphic record, it is possible to estimate the paleo‐hydraulic parameters such as water discharge and bed slope more precisely than previously. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

海原台四分量钻孔应变观测的相对标定及资料应用   总被引：1，自引：0，他引：1  

吴立辛  张立强  李国斌  郭宏斌 《地震研究》2010,33(4)

宁夏海原台四分量钻孔应变观测的相对标定结果显示,标定后分量1、分量3之和与分量2、分量4之和的资料相关性显著增强,标准差明显减小,更加满足四分量应变仪的校核条件,表明该钻孔应变观测资料是可靠的。将各分量应变资料去趋势,计算出面应变1+3和2+4、差应变1-3和2-4,对面应变、差应变资料和相对标定系数在2008年4月6日固原3.8级、5月12日汶川8.0级、10月3日固原4.0级和11月24日固原3.8级地震前的异常变化进行了分析探讨。结果显示,钻孔应变观测的相对标定及资料应用有助于地震前兆异常的判定识别。  相似文献   

岩石非弹性应变恢复(ASR)地应力测试方法中柔度研究进展评述     

马秀敏  彭华  白金朋  李振  姜景捷 《地质力学学报》2017,23(4):526-530

本文通过分析国内外非弹性应变恢复(ASR)法地应力测量研究现状,并对ASR法中重要的柔度参数作了系统整理,认为该测量方法在理论上逐渐趋于成熟,在技术应用上有广阔的前景,但该地应力测量原理中,针对温度、应力环境(作用应力)对ASR岩石柔度影响的研究相对较少,还存在一些缺陷,为此提出了该地应力测试方法有待改进或补充的建议,为完善ASR法地应力测量原理指明了研究方向,对今后ASR地应力测量技术的完善和发展具有重要的意义。  相似文献   

ACMEG-TVP: A thermoviscoplastic constitutive model for geomaterials     

《Computers and Geotechnics》2017

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基桩极限承载力的改进变步长灰色预测模型研究     

曹文贵  张永杰  赵明华 《岩土力学》2006,27(Z1):774-778

在深入研究桩土相互作用机理及基桩极限承载力变步长灰色预测方法基础上,针对现有基桩极限承载力灰色预测模型之基桩Q-S曲线导数与背景值确定方法的局限性与不足,结合Q-S曲线发展规律,提出了基桩极限承载能力的改进变步长灰色预测模型与方法,并初步探讨了基桩极限承载力灰色预测方法的精度与可靠性。通过工程实例计算并与同类方法计算结果进行比较分析,表明了所建模型的合理性。  相似文献