Residual strength of slip zones of large landslides in the Three Gorges area, China

Slip zones of the large landslides in the Three Gorges area are commonly composed of fine-grained soils with substantial amount of coarse-grained particles, particularly gravel-sized particles. In this study, residual strength of the soils from slip zones of these landslides were examined in relation to their index properties based on a survey of 170 landslides. It was found that laboratory-determined residual friction angle using gravel-free fraction of the disturbed soils from the slip zones was closely related to clay content, liquid limit and plasticity index. On the other hand, in-situ residual friction angle of these soils (i.e. including gravel fraction) showed very weak correlations with clay content and Atterberg limits, but was largely dependent on gravel and fines (clays + silts) contents, increasing with gravels and decreasing with fines, and displayed strong linear correlation with the ratio of gravel to fines contents. These observations indicate that among the index properties, clay content and Atterberg limits can be used to estimate residual strength of the soils finer than 2 mm, but they are not appropriate evaluate the residual strength of the soils containing considerable amount of gravel-sized particles. For the latter, particle size distribution (particularly the ratio of gravel to fines contents) appears to be a useful index. Additionally, it was found that there was no identifiable correlation between relative abundance of individual major clay minerals and residual friction angles of both gravel-free fraction of disturbed and in-situ soils, suggesting that influence of clay minerals on residual strength of these soils can not be simply evaluated based on their abundance.     

A 48-kyr-long slip rate history for the Jordan Valley segment of the Dead Sea Fault

We investigate the late Quaternary active deformation along the Jordan Valley segment of the left-lateral Dead Sea Fault and provide new insights on the behaviour of major continental faults. The 110-km-long fault segment shows systematic offsets of drainage systems surveyed at three sites along its southern section. The isotopic dating of six paleoclimatic events yields a precise chronology for the onset of six generations of gully incisions at 47.5 ka BP, 37.5 ka BP, 13 ka BP, 9 ka BP, 7 ka BP, and 5 ka BP. Additionally, detailed mapping and reconstructions provide cumulative displacements for 20 dated incisions along the fault trace. The individual amounts of cumulative slip consistently fall into six distinct classes. This yields: i) an average constant slip rate of 4.7 to 5.1 mm/yr for the last 47.5 kyr and ii) a variable slip rate ranging from 3.5 mm/yr to 11 mm/yr over 2-kyr- to 24-kyr-long intervals. Taking into account that the last large earthquake occurred in AD 1033, we infer 3.5 to 5 m of present-day slip deficit which corresponds to a Mw  7.4 earthquake along the Jordan Valley fault segment. The timing of cumulative offsets reveals slip rate variations critical to our understanding of the slip deficit and seismic cycle along major continental faults.     

慢滑移及相关脉动和慢地震研究的历史和现状

观测表明,慢滑移事件通常发生在活动断裂带内,为发震层之下的短暂滑移,能够造成地表的瞬态运动。与慢滑移密切相关的慢地震能够发射出频率在一定范围内的脉动信号,但不造成灾害性事件。慢滑移和慢地震很可能是断裂带上形变能释放的基本方式,其观测有可能为人们更深入地了解断裂带的动力学过程提供基础和依据。本文重点介绍近10年来关于慢地震和慢滑移事件的研究历史和现状。目前对慢滑移引发的地表形变和慢地震发射的脉动信号特征有了深入细致的研究,开展了对慢滑移的数值模拟和慢地震定位的研究;但对慢地震和慢滑移发生的位置、两者的关系以及物理机制等方面还存在很多争论和问题。     

多频数据组合在周跳探测和修复上的应用

利用模拟的L5观测数据，结合传统的伪距／载波组合法，对周跳的探测与修复进行了实例计算，并与双频组合观测值的周跳探测方法进行了比较。结果证明，不管对大周跳还是小周跳，该方法均能在单历元间准确地探测出各个频率上发生的周跳，较之双频组合观测值的探测方法具有更大的优越性。     

基于三差解检测与修复GPS载波相位周跳新方法

对飞行中初始化载波相位整周模糊度ＧＰＳ的动态差分定位而言,如果在整周模糊度初始化过程中发生载波相位周跳,将严重影响整周模糊度的确定,本文对已有的ＧＰＳ静态差分定位中通过三差解检测与修复周跳的方法进行了推广,提出了一种适合于解决Ｏｎ－Ｔｈｅ－Ｆｌｙ整周模糊度初始化过程中周跳问题的新方法。新方法保持了静态情况下原有方法的特点,分析和利用实采数据进行的检验表明,新方法是有效和实用的。     

湘赣边区NNE向走滑断裂-流体-铀成矿动力学分析

以湘赣边区ＮＮＥ向走滑断裂系统构造解析及其演化和动力学分析为主线,结合含矿流体的运动学过程研究,进行热液铀成矿动力学分析,以探讨成矿作用的动力来源、作用机制和演化过程。     

1976年唐山地震发震断裂的活动性研究

震后野外考察及航空摄影发现的地裂缝带,说明唐山断裂与１９７６年唐山７．８级大地震的发震构造有密切关系。用卫星遥感信息和浅层地震勘探结果对唐山断裂的活动性做了新的研究。卫星图像解释结果表明：震前一年多时间内,ＮＥ向的唐山断裂被ＮＮＷ向断裂截切而ＮＷＷ向断裂受到牵引,因而显示出右旋走滑的活动形迹。浅层地震勘探结果则证明,唐山断裂是倾向ＮＷ,高倾角的右旋走滑正断层,它断错了全新统（Ｑ４）、晚更新统（Ｑ３）、中更新统（Ｑ２）和早更新统（Ｑ１）地层     

走滑断裂带中挤压阶区内部剪切构造初探

野外地质调查和航片立体镜下解译发现,小江断裂带北段蒙姑和东支大营盘两个挤压阶区内部发育有剪切构造,它们在地表主要表现为断裂槽地、断层陡坎、地裂缝等。挤压阶区内部剪切构造和拉张阶区内部剪切构造一样,是阶区形成后,随着走滑断裂的进一步活动而形成的新生性构造     

走滑拉分断块对沉积的控制作用——准噶尔盆地东部侏罗系中下统沉积主控因素新认识

通过在南缘露头剖面相构型识别,北部地震剖面解释的沉积体侧向迁移特征,建立了走滑拉分构筑的可容空间变化型式。此沉积对构造的响应模式,不仅可以很好的解释拼合砂体的分布,古流向偏转等问题,而且对于预测盆内沉积体走向也是一个很有用的工具。