Regional scale strain variations in Banded Iron Formations of Eastern India: results from anisotropy of magnetic susceptibility studies     

A. Mukherji  A. K. Chaudhuri  M. A. Mamtani   《Journal of Structural Geology》2004,26(12):2175-2189

Anisotropy of magnetic susceptibility (AMS) data are used as a tool to determine strain variations in different parts of the Banded Iron Formations (BIFs) of the Bonai Synclinorium, eastern India. AMS data of 88 cylindrical cores drilled from 29 samples collected from the limb and hinge parts of mesoscopic scale folds as well as different parts of the entire synclinorium are presented. It is found that the samples from limbs of small-scale folds and also from limbs of the regional scale synclinorium have higher degrees of anisotropy than the hinges. This is inferred to indicate that the limbs accommodated higher strain than the hinges. AMS orientation data are analysed in conjunction with field data. It is concluded that the magnetic fabric developed in the limbs as well as hinges of the BIFs of the study area is related to deformation and is not a manifestation of sedimentary fabric.  相似文献   

Seismic strain rates and distributed continental deformation in the northern Andes and three-dimensional seismotectonics of northwestern South America   总被引：1，自引：0，他引：1  

Freddy Corredor 《Tectonophysics》2003,372(3-4):147-166

Remote sensing and field studies of several extensional basins along the northern margin of the Gulf of Aden in Yemen show that Oligocene–Miocene syn-rift extension trends N20°E on average, in agreement with the E–W to N120°E strike of main rift-related normal faults, but oblique to the main trend of the Gulf (N70°E). These faults show a systematic reactivation under a 160°E extensional stress that we interpret also as syn-rift. The occurrence of these two successive phases of extension over more than 1000 km along the continental margin suggests a common origin linked to the rifting process. After discussing other possible mechanisms such as a change in plate motion, far-field effects of Arabia–Eurasia collision, and stress rotations in transfer zones, we present a working hypothesis that relates the 160°E extension to the westward propagation since about 20 Ma of the N70°E-trending, obliquely spreading, Gulf of Aden oceanic rift. The late 160°E extension, perpendicular to the direction of rift propagation, could result from crack-induced extension associated with the strain localization that characterises the rift-to-drift transition.  相似文献   

新马德里地震带的岩石圈强度与板内形变          下载免费PDF全文

刘澜波  MarhD．Zoback 《地球物理学报》1998,41(Z1):1-14

提出一个简单的假说来解释为什么在相对稳定的板块内部地区会存在高地震活动区与高构造形变区．首先,对于大多数板内地区而言,特别是大陆地盾地区与老的海洋盆地,下地壳与上地幔的温度相当低,那里的岩石相对坚硬在这些地区不可能发生明显的岩石圈变形,因为岩石图累积强度大大超过板块驱动力．相反,如果下地壳与上地幔温度相对较高,板块驱动力则主要由上地壳承受,因为下地壳与上地幔相对软弱在这种地区,由于岩石圈累积强度与板块驱动力大小相当,构造形变相对较快．本文将这种假说应用在位于美国中部的新马德里地震带与周围地区．地震带内部热流密度值约为60mw／m2,略高于本区背景热流密度值45mW／m2．计算得到的地温梯度与实验室结果所揭示的延性流动定律表明,在地震带内下地壳与上地幔相当软弱,板内应力主要由上地壳传递．那里的形变速率相对较高．与此相反,在周围地区热流值相对较低,岩石四累积强度大大超过板块驱动力,构造应力由地壳与上地幔共同承受热流值的大小和下地壳上地幔的受力状态是决定地震活动性在地震带内与周围地区强烈对比的主要因素．  相似文献   

变形分解作用研究综述     

陈桂华  徐锡伟 《华南地震》2004,24(4):11-20

变形分解作用是描述总的构造应变变形如何分解到一定意义分量的一个运动学概念。变形分解作用形成的构造应变变形分量之间的分解可以是表现在应变场的不均一性，也可以是同一应变场的，还可以是表现在构造力学性质、变形机制等的差异。因此，作为一种运动学概念，它涉及多个构造应用领域，研究者建立了多种不同的变形分解作用运动学模型并讨论其控制因素。为构造变形分解作用的研究提供了一种系统思维的研究思路，有利于更系统的认识相关地质构造之间存在的联系。综述了国内外学者对变形分解作用的研究。  相似文献   

山西晋城市的地震与断裂活动     

李小壮 《山西地震》2004,(3):35-38

收集了晋城地区的地震活动情况。分析了晋城市地震活动特征与断裂活动的特征。得出了晋城市的地震活动主要与晋获断裂带的活动有关的结论。  相似文献   

昆仑山口西8.1级地震前高台钻孔应变异常特征   总被引：6，自引：1，他引：6  

尹亮  李兴坚  陈兰新  武银  刘晓明  陈建军  刘鸿斌  许玉红  李东生  雷登学 《高原地震》2002,14(1):83-86

研究分析了2001年11月14日昆仑山口西Ms8．1级地震前高台钻孔应变资料的异常特征，通过对资料长趋势异常和短临异常的探讨，总结了本台钻孔应变的映震能力。  相似文献   

川滇地区应变强度比动态图像分析   总被引：5，自引：0，他引：5  

张希  江在森  王双绪  陈兵 《高原地震》1999,(3)

利用从跨断层形变资料中获取应变强度比动态图像的方法,结合震例对川滇地区８０年代以来跨断层形变资料选择方法不同所获得的应变强度比分布动态图像的２种结果进行分析,并给出中短期强震危险区判定指标  相似文献   

Experimental Study on the Stick-slip Phenomenon of Intact Granite under Solid Confining Pressure     

Cheng Haixu  Wu Kaitong  Zhang LiuCenter for Analysis  Prediction  SSB  Beijing  China Institute of Geology  SSB  Beijing  China 《中国地震研究》1995,(2)

In this paper,compression tests of intact granite samples have been made in a triaxial testing machine with solid confining pressure.From the tests,the influences of confining pressure and loading rate(axial strain rate)on the deformation and fracture process of rock samples,on the stress drop and recurrence interval of stick-slip events,and on the geometric distribution of the main fracture have been studied.The experimental results show that the loading rate influences the stress drop and recurrence interval of stick-slip events greatly.At lower loading rates,the stress drop of stick-slip events is greater,their recurrence interval is longer and shows no regularity in distribution.When the loading rate goes higher,the stress drop will become smaller and the recurrence interval will tend to be constant and stick-slip events show a quasi-periodicity.At lower confining pressures and strain rates,the main fracture may evolve into 2 X-shaped conjugate shear faults; whereas at higher confining pressures and  相似文献   

Gravity interpretation of nonoutcropping sedimentary basins in which the density contrast decreases parabolically with depth     

V. Chakravarthi 《Pure and Applied Geophysics》1995,145(2):327-335

The decrease in density contrast of sedimentary rocks with depth in many sedimentary basins can be approximated by a parabolic density function. Analytical gravity expression of an outcropping two-dimensional vertical step along which the density contrast decreases parabolically with depth is derived in the space domain. A modification ofBott's (1960) method of gravity interpretation is proposed by considering two outcropping vertical steps on either side of the first and last observation points in addition toN outcropping vertical prisms in order to interpret the gravity anomalies of nonoutcropping basins. The thicknesses of the two outcropping vertical steps are made equal to the thicknesses of the two outcropping vertical prisms placed below the first and last observation points. The initial depth estimates of the sedimentary basin are calculated by the infinite slab formula ofVisweswara Rao et al. (1993). The gravity effects of theN outcropping prisms and the two outcropping vertical steps are calculated at each anomaly point and the depth to the floor of the basin are adjusted based on the differences between the observed and calculated anomalies. A gravity anomaly profile of Los Angeles basin, California is interpreted.  相似文献   

5°拐折构造变形物理场的实验研究与数值模拟          下载免费PDF全文

《地震地质》1995,17(4):318

以实验方法和数值模拟方法研究了含５°拐折的断层在变形过程中物理场的时空演化。结果表明在一次事件序列中拐折部位的声发射往往发生在序列开始时和结束时，震级虽不大，但却有重要意义。在断层错动中拐折部位两侧的断层交替地作为变形主体构造，拐折部位则起了错动阀的作用  相似文献