临潼-长安断裂带构造变形及分段特征

对临潼-长安断裂带1970～1996年跨断裂水准资料、1983-2004年跨断层场地水准资料和1992～2004年重力段差资料进行了定量计算与分析。分析结果表明：①临潼-长安断裂是近期非常活跃的断裂，断裂带中主次断裂具有对称活动特点，江伊-鲍坡断裂在该断裂带整体活动中居主动地位；②跨临潼-长安断裂带的麻街和沣峪口两场地在地震前，垂直形变均不同程度地出现准同步快速下降的异常变化，但震后区域应力场的调整过程中两场地的影响存在差异；③临潼-长安断裂带的活动具有明显的分段性特点，形变测量资料分析表明，其南段活动比较稳定，而北段的活动则很活跃；④场地水准与跨断裂水准资料有较好的一致性，重力段差变化与场地垂直形变有较好的相关性。     

临潼—长安断裂带构造形变

本文在对临潼—长安断裂带挽近构造特点进行分析研究的基础上,重点分析了其垂直形变监测资料,指出它是一条可以提供前兆性信息的敏感性断裂,其主次断裂带具有对称活动的特点,其中主断裂,特别是其北段尤为活跃,应重点监测。断裂带形变趋势表明,其形变尚处于稳态阶段,近年内不会发生大震。     

临潼-长安断裂带晚第四纪以来的活动性

对临潼-长安断裂带进行了详细的野外调查,以期掌握其最新活动年代和第四纪以来的活动特征。该断裂总体走向NE,以张性垂直运动为主,断面明显错断了黄土中的第1层古土壤S1,说明其晚更新世以来仍在活动,并且北段和中段的活动性比南段强,但是错距大多<2m,滑动速率较小,考虑到临潼-长安断裂带由多条次级断层组成,其整体活动性应该比我们计算得到的局部断层滑动速率大得多。断层错距自上而下成递增趋势,并且根据不同地层年代计算出的滑动速率基本一致,因此该断裂带自中更新世晚期以来极可能以垂向蠕滑活动为主     

临潼-长安断裂带古地震及地震危险性评价

长安二中探槽是在地面地质调查、浅层地震和钻探的基础上开挖的,探槽中有丰富的砂土液化现象,根据液化砂脉的切割关系,判断有4次古地震事件的发生。根据探槽中地层没有明显错动和临潼-长安断裂带在晚更新世晚期和全新世早期活动较弱,以及历史上无6级以上地震活动记录的特点,本文认为4次古地震事件与临潼-长安断裂带无关,该断裂未来发生强震的危险性不大。     

临潼-长安断裂带晚更新世时期的活动特征

对野外大量断层露头及探槽剖面分析所作表明,临潼—长安断裂带错断晚更新世第一古土壤层0.2~6.0m,平均1.1m,最大活动速率为0.047mm/a。在晚更新世晚期断裂表现为裂缝形式,地层没有明显的错动,断裂活动较弱。晚更新世白鹿塬段断裂活动相对较强。     

临潼-长安断裂活动性研究

临潼—长安断裂是渭河盆地内部骊山凸起和西安凹陷之间一条重要的分界性断裂,前人研究表明该断裂在全新世有强烈活动。通过对该地区钻孔资料的收集整理、跨断裂阶地测量分析以及晚更新世古土壤标志层错距的量测,分析了早更新世后期以来断裂的活动性特征,认为临潼-长安断裂在中更新统以前有过强烈活动,中更新世以来断裂活动性明显减弱,活动形式表现为张裂或小的位错。     

临潼-长安断裂带(FN )西段走向研究

临潼-长安断裂是渭河盆地内西安凹陷与骊山凸起的分界断裂,该断裂东北段位置和走向清楚,但西南段(神禾塬以西)的推测走向并无实证资料。在临潼-长安断裂西南方向延伸区域内,通过对3条总长近27km的人工地震勘探剖面解译,发现均存在北倾断裂异常,在其中1处异常布置的地质钻探剖面显示,上更新统和中更新统地层存在错断现象。这些勘探异常点被认为是临潼-长安断裂带中的最北侧断裂FN,其连线基本在1条线上,以大约SW240°的方向,延续了临潼-长安断裂带中段走向,继续向西南方向延伸。     

临潼-长安断裂错距及其分布特征

临潼-长安断裂是渭河盆地内部骊山凸起与周至-户县凹陷之间一条重要的边界性断裂。通过大范围自然冲沟、人工取土场、道路开挖边坡和路堑的野外观察,新发现临潼-长安断裂露头40余处。基于各露头不同年代古土壤标志层错距的量测,获得了晚始新世以来该断裂的位移分布。第四纪以来的断层位移分布显示出该断裂中段断距较大,活动较为强烈     

长安—临潼断裂的活动与西安地区地震危险性探讨

阐述了西安地区最大规模的长安-临潼断裂带的展布、构造形迹、运动特征。指出了它是西安地区地震活动的主要发震构造。根据其地震活动特征等分析,对断裂带未来危险性作了评估。     

西影深井水位变化与临潼—长安断裂活动

把消除掉气压、固体潮效应后的西影井水位值与临潼——长安断裂带上的垂直形变值进行相关分析,发现二者有一定的相关性。可以看出,西影深井水位变化在某种程度上反映着井位附近的断层活动。最后作者对其形成原因进行了粗浅的分析。     

Geometric structure and formation mechanism of Lintong-Chang’an fault zone

The results from investigation of large quantity of fault outcrops and artificial earthquakes suggest that the Lin-tong-Chang’an fault zone mainly consists of two faults. One is the Majie-Nianwan fault that separates a branch of Wangjiabian-Houjiawan fault on the right bank of the Bahe River; the other is the Hujiagou-Shoupazhang fault that separates a branch of Zhongdicun-Tangjiazhai fault in Tongrenyuan and Shaolingyuan. As tensional dip-slip normal faults, the faults distribute with approximately parallel equal intervals in local regions and the profiles drop in a step-like form to the northwest, presenting a Y-shape combination. The result from deep seismic reflection indicates that the fault is about 5~8 km in depth, which is not only a basement fault, but also a listric normal fault in the deep stratum. The Lintong-Chang’an fault is a typical outstretching rift system under the NS-trending ten-sion stress field. At the same time, affected by the sinistral strike slip of the Yuxia-Tieluzi fault, the fault extends like a broom from the northeast to the southwest.     

Characteristics of the Activity of the Lintong-Chang＇an Fault in the Late Pleistocene

Analysis of fault outcrops and trench sections indicates fault displacements of 0.2m - 6.0 m on the bottom paleosol layer of the Epipleistocene with the maximum rate of 0.047 mm/a and an average displacement of 1.1 meters. The activity appears as fissures on the fault surface in the late Epipleistocene and there is no obvious displacement. The fault activity is weak and the most active segment is the Bailuyuan segment.     

Geometric form of Haiyuan fault zone in the crustal interior and dynamics implications

Introduction The deep faults in the crust have direct relation to the occurrence of earthquakes and the dis-tribution of active seismic zones, so the researches on the geometric form and physical parametersof deep crustal faults are always an important problem in seismology. The researches are not onlysignificant to knowledge the deep tectonic background of strong earthquake and seismogenicmechanism, but also play a very important role in earthquake hazard estimation and earthquakeprevent…     

Geometric form of Haiyuan fault zone in the crustal interior and dynamics implications

The deep seismic reflection data on profile HY2 are reprocessed by the method of simultaneous inversion of velocity distribution and interface position. By the travel-time inversion with the data of the diving wave Pg and fault plane reflection wave, we determine the geometric form and velocity of Haiyuan fault zone interior and surrounding rock down to 10 km depth. The measured data show that the amplitudes have strong attenuation in the range of stake number 37–39 km, suggesting the fault zone has considerable width in the crustal interior. The results of this paper indicate that to the north of the fault zone the crystalline basement interface upheaves gradually from southwest to northeast and becomes shallow gradually towards northeast, and that to the south of the fault zone, within the basin between Xihua and Nanhua mountains, the folded basement becomes shallow gradually towards southwest. The obliquity of the fault zone is about 70° above the 3 km depth, about 60° in the range of the 3–10 km depths. From the results of this paper and other various citations, we believe that Haiyuan fault zone is in steep state from the Earth’s surface to the depth of 10 km. Foundation item: Joint Seismological Science Foundation of China (201001) and State Key Basic Research Development and Programming Project (95-13-02-02). Contribution No. RCEG200308, Exploration Geophysical Center, China Earthquake Administration.     

丽江-小金河断裂带现今断层运动特征

本文利用GPS观测对丽江—小金河断裂带的现今断层运动和变形状态进行了分析和探讨.丽江—小金河断裂带两侧地块地壳变形差异显著,GPS速度剖面结果显示断裂带两侧存在地壳变形不连续现象;进一步以GPS速度场为约束,基于负位错模型反演的丽江—小金河断裂带的断层闭锁空间分布结果显示,以木里为界,北东段断层强闭锁从地表向深部延伸至15 km左右,西南段断层闭锁程度较高的区域位于5~15 km范围内,浅层表现为弱闭锁的状态;滑动亏损速率结果显示,两闭锁段的滑动亏损速率相差近4 mm·a^-1,说明丽江—小金河断裂带西南段的背景滑动速率明显高于北东段.基于数值模拟分析了西南段浅层蠕滑运动对周边断层的影响,结果表明西南段的浅层左旋滑动对北东段闭锁区和西南段深部强闭锁区均为正影响.

     

Structural analysis of the Brigham City-Weber segment boundary zone,Wasatch normal fault,Utah: Implications for fault growth and structure

We investigate the history, kinematics, principal stress orientations and geometry of deformation at the end of a bent normal fault segment of the Wasatch fault zone, Utah. Three fault types, developed in Archean crystalline rocks, reflect progressive uplift of fault-related footwall rocks. Chlorite-breccias and phyllonites reflect deep-level, reaction-assisted plastic deformation along the north-striking part of the segment. Planar, fretted faults which formed by cataclasis cut the phyllonites and breccias and are developed throughout the footwall of the segment. Youngest faults are hematitecoated, extremely narrow polished surfaces. Slip vectors and kinematic analyses of small faults developed in the footwall indicate oblique normal slip along the north-striking portion of the segment. Slip vectors and fault orientation along the northwest-striking portion of the segment reflect complexly oriented slip on faults which strike subparallel and at high angles to the main fault trace, yet slip is confined to a broad fault-parallel zone. Small faults at the southernmost tip of the segment indicate a strong influence of the north-striking Weber segment to the south. Inversion of fault data for principal stress orientations document complexly oriented principal stresses through the segment boundary zone and suggest that ₃ may have reoriented approximately 60° over the life of the segment. Subsurface structure combined with small fault data indicate the segment boundary is comprised of a southwest-plunging bedrock high which is reflected by a sharp bend in the Brigham City segment. The southern end of the Brigham City segment may have started, as a straight, north-striking fault which has bent due to changes in stress orientations and/or interaction with the adjacent Weber segment.     

龙门山断裂带地壳精细结构与汶川地震发震机理

利用2001年1月至2008年6月四川固定地震台网和临时地震台站记录到的大量P波到时资料,反演了龙门山断裂带及周边地区的地壳精细三维P波速度模型. 结果表明,汶川主震以北和以南地区的结构存在较大差异,以北地区的龙门山断裂带具有很强地壳不均匀性,这与该区发生了大量汶川地震的余震相一致. 这些结果有意义地改进了前人对龙门山断裂带仅为不同块体过渡带的认识. 汶川主震震源区下方存在有明显低波速异常体,表明流体可能存在于龙门山断裂带内. 这些流体可能直接影响汶川大震的形成. 本文的成像结果为下地壳流沿龙门山断裂带上浸提供了可靠的地震学证据.     

沂沭断裂带内部的差异活动及其成因分析

郯庐断裂带在山东境内被称为沂沭断裂带的部分是其新构造活动最为强烈的一段.许多学者对沂沭断裂带做过大量研究工作,指出沂沭带活动存在差异性,但较少关于差异活动的原因分析.本文在前人研究工作基础上,较为深入地分析了沂沭带5条断裂的主要活动规律及其特点,对沂沭带进行了新的分段,并归纳了沂沭带不同断裂之间、同一断裂不同段落之间的活动差异及其差异的基本特征.在此基础上,从地貌、断裂结构、断裂空间组合、现代运动、深部构造环境等几个方面,分析阐述了造成沂沭带差异活动的可能原因,为更深入地研究沂沭带提供了新鲜的启示和思路.     

龙门山断裂带形成过程及其地应力状态模拟

以龙门山附近区域运动特征以及深部岩体力学特性为基本条件,采用FLAC模拟软件计算模拟分析了龙门山断裂形成过程和塑性区分布的几何特征.研究结果认为：汶川—茂县断裂F1、映秀—北川断裂F2和灌县—安县断裂F3是从中部开始发育,塑性区上侧逐渐发展至地表;F1断层首先出现,以后才依次形成F2和F3断层.这些塑性区的发育方向与水平面的夹角大致呈40°左右,并出现了各自的共轭断层,与实际的龙门山断裂大致吻合,说明区域构造运动是龙门山断层产生的主因.论文还揭示了区域构造运动过程中区块内主应力的变化规律,主要分为2个阶段,一是在区块挤压初期,主应力随着区块位移量的增大而增大;二是主应力相对稳定阶段,区块岩体内的主应力保持相对稳定的状态,达到临界破坏岩体的最大最小主应力比值一般介于3.31~4.39.