大盈江断裂西南段晚第四纪活动研究

根据断裂地质、地貌特征和卫星影象资料,阐述了大盈江西南段晚第四纪的活动特征和运动方式.结果表明:大盈江西南段主要表现为左旋走滑运动,为晚更新世活动断裂,沿断裂历史上发生过6级左右地震.     

天山内部博罗可努断裂精河--阿拉山口段晚更新世以来的活动特征

通过对博罗可努断裂河－阿拉山口段微地貌的实地调查,发现该断裂错情河东南到阿拉山口之间的晚更新世冲洪积扇,地表留下了冲沟和山脊同步右旋位错、断层陡坎、断层鼓包、拉分盆地等与断层活动有关的微地貌。精河东南冲洪积扇上大冲沟的最大右旋位移为５００ｍ,平均４００ｍ,断层陡坎上的纹沟右旋位移为２．６～４．０ｍ,较大级别的纺沟位移可分为５．７ｍ,８．３ｍ和１５．３ｍ３组,它们大致为３的整数倍。实测断层陡坎的高度     

晚第四纪以来巴塘断裂的活动特征及滑动速率

青藏高原东南缘是现今陆内地壳形变最为强烈的地区之一,一系列长度和力学性质不同的活动断裂将岩石圈分割为多个活动块体。川滇块体是其中构造活动最为显著的区域之一,其西边界由多条互相平行的断裂组成,巴塘断裂是其中的一条主干断裂。了解该断裂晚第四纪以来的变形特征和速率对于认识川滇块体强震的空间分布及变形模式具有重要意义。巴塘断裂整体走向NNE,全长115km,是一条全新世右旋走滑活动断裂。该断裂基本控制了基岩山体边界,其中坡中槽、三角面、断层陡崖等地貌沿断裂呈线性分布,并在黄草坪及巴塘县城2处区域保存了丰富的晚第四纪活动证据。文中利用无人机摄影测量手段建立了黄草坪及巴塘县城分辨率达亚米级的数字地形数据,并对被断错的洪积扇、冲沟等地貌标志物进行了精确测量。在黄草坪地区,巴塘断裂活动造成的山前冲沟水平偏转量为(46±9) m,同时在巴塘县城断裂活动使莫曲河洪积扇边缘被右旋断错(40±5) m。文中利用单个砾石宇宙成因核素法及深度剖面法分别确定了黄草坪最老一级地貌面和莫曲河洪积扇的年龄,分别为(12.5±0.5) ka和(16.4+3.9/-5.6) ka,据此可以得到巴塘断裂晚第四纪以来的右旋走滑速...     

天山内部博罗可努断裂精河—阿拉山口段晚更新世以来的活动特征

通过对博罗可努断裂精河—阿拉山口段微地貌的实地调查 ,发现该断裂错断精河东南到阿拉山口之间的晚更新世冲洪积扇 ,地表留下了冲沟和山脊同步右旋位错、断层陡坎、断层鼓包、拉分盆地等与断层活动有关的微地貌。精河东南冲洪积扇上大冲沟的最大右旋位移为 50 0m ,平均4 0 0m。断层陡坎上的纹沟右旋位移为 2 6～ 4 0m ,较大级别的纹沟位移可分为 5 7m ,8 3m和 15 3m3组。它们大致为 3的整数倍。实测断层陡坎的高度分别为 1 2m ,2 51m和 3 6 3m ,大致是 1 2的整数倍 ,阿拉山口西南断层的水平位移为 1～ 1 7m ;垂直位移可分为两组 ,一组为 0 55m ,另一组为 1 2～ 1 5m。这些数据可能揭示了该断裂段的特征地震水平位移为 3m ,垂直位移为 1 2m。区域地貌对比和年代学分析得出 ,精河东南冲洪积扇的最后形成时代为距今 7万a左右 ,右旋滑动速率为4 7mm/a。     

阿拉善地块南缘北大山断裂的晚第四纪构造活动证据

阿拉善地块南缘地处青藏高原东北缘地壳扩展前锋带的北侧,对该地区活动断裂晚第四纪的运动性质、滑动速率等开展研究,有助于理解阿拉善地块的晚第四纪构造变形特征及其对青藏高原向N扩展的响应。文中结合遥感影像解译与野外地质地貌考察,对阿拉善地块南缘的北大山断裂进行了分段和活动性研究。结果表明,北大山断裂左旋走滑断错晚第四纪洪积扇和阶地等地貌,形成显著的位错阶地坎、冲沟以及断层陡坎。通过对断错地貌线等标志的测量、复原、统计分析等,发现断裂的地貌位移值分布于3～20m,发育新鲜断层自由面的断层陡坎和左旋错动的纹沟指示了断层的最新一次活动。基于同期洪积扇年龄估算得到北大山断裂晚更新世以来的左旋滑动速率为0.3～0.6mm/a。北大山断裂的运动学特征与区域NE向应力场一致,可能受到了青藏高原NE向扩展的影响。     

孟连断裂晚第四纪活动特征

孟连断裂是滇西南地区的1条区域性活动断裂。本文通过地形地貌、断裂剖面及地震活动等对断裂的空间展布及晚第四纪活动性进行分析和研究,获得了断裂活动时代和活动速率等参数。研究表明:孟连断裂晚第四纪期间仍在活动,最新活动时代为全新世,运动性质以左旋走滑为主,晚第四纪以来的平均水平滑动速率为3.8—5.1mm/a;该断裂控制着孟连、勐阿等第四纪盆地的发展及演化,沿断层发生了1995年7月12日中缅边境7.3级地震。     

晚更新世末期仙女山断裂带和天阳坪断裂带活动的最新证据

依据野外槽探实测的仙女山断裂带和和天阳坪断裂带的地质剖面，通过研究断层堆积与构造岩，新老构造岩变形，断层破裂有其几何特征，断层充填物采样年代鉴定等，获得了两断裂带晚更新世末期活动和古地震的最新证据。     

安宁河断裂带北段晚更新世以来的分段活动特征

本文据断裂带的断层几何形态、组合型式、断错地貌及地震活动资料,讨论了安宁河断裂带北段(西昌-石棉田湾段)在晚更新世以来的活动性状。根据该段活动程度的差异,从南至北将其分为三个活动段,即西昌-冕宁段;冕宁-紫马垮段;紫马垮-田湾段。上述三个活动段除南段具备发生大震背景外,中段和北段分别具有发生强震和中强震的背景。根据断层泥中石英碎屑表面扪描电子显微(SEM)结构特征,讨论了安宁河断裂带北段的运动性质,指出西昌-紫马垮段具粘滑运动方式;紫马垮-麂子坪段具粘滑、蠕滑兼有的运动方式;麂子坪以北至田湾段具以蠕滑为主的运动方式。     

白龙江断裂西段晚第四纪构造活动特征研究

白龙江断裂位于青藏高原东缘,东昆仑断裂的北侧。白龙江断裂西段的展布及其活动性对研究东昆仑断裂速率向东衰减的机制有重要科学意义。本文根据遥感解译、地质地貌调查、探槽和地质剖面研究白龙江断裂西段的几何展布和断层活动性。白龙江断裂西段分为3支,包括郎木寺断裂、阿米塘断裂和热尔-旺藏断裂组成的中支、崩巴村断裂构成的南支和下山-迭部断裂构成的北支。这些断裂皆为左旋走滑断层,其中下山-迭部断裂、郎木寺断裂和热尔-旺藏断裂为全新世断层,崩巴村断裂为晚更新世断层。白龙江断裂西段沿袭了前第四纪断裂展布,其分支的几何形态上属于一种典型的尾端构造样式：同向分支断层。研究结果表明白龙江断裂地表上未与东昆仑断裂直接相接,而在深部与之相接,可能分解吸收了东昆仑断裂的部分滑动速率,使得塔藏断裂的滑动速率低于其西侧的玛曲断裂。     

THE ACTIVITY OF WESTERN LISHAN FAULT SINCE THE LATE PLEISTOCENE

Along the northern piedmont of Mt. Lishan, the characteristics and locations of the active normal Lishan fault in west of Huaqing Pool provide important evidences for determining the seismotectonic environment, seismic stability evaluation of engineering in the eastern Weihe Basin. After reviewing the results from high-density resistivity method, seismic profile data, geological drillhole section and trenching in west of the Huaqing Pool, it is found that the strike of western normal Lishan Fault changes from EW direction at the eastern part to the direction of N60°W, and the fault consists of two branches, dipping NE with a high dip angle of~75°. The artificial shallow seismic profile data reveals that the attitude of strata near Lishan Fault mainly dips to south, which is presumed to be related to the southward tilt movement of Mt. Lishan since the Cenozoic. The section of geological drillhole reveals that since the late middle Pleistocene, the displacement of the paleo-soil layer S₂ is about 10m. And the maximum displacement of western Lishan Fault recorded in the paleo-soil layer S₁ reaches 7.8m since the late Pleistocene. In addition, evidences from trench profile show that the western Lishan Fault was active at least 3 times since Malan loess deposition with ¹⁴ C dating age(32 170±530)Cal a BP. The multiple activities of the Lishan Fault result in a total displacement about 3.0m in the Malan loess layer L₁. The latest activity of the western Lishan Fault produced a displacement of about 0.9m in the early Holocene loess layer L₀((8 630±20)Cal a BP)and caused obvious tensile cracks in the Holocene dark leoss layer S₀((4 390±20)Cal a BP). Briefly, we have obtained a vertical movement rate of about 0.11~0.19mm/a since the Holocene((8 630±20)Cal a BP)in the western extension of the Lishan Fault, the recurrence interval of earthquakes on the fault is about(10.7±0.5)ka, and the co-seismic surface rupture in a single event is inferred to be about 0.9m.     

阿尔金主断裂东端第四纪左行走滑的新证据

通过对阿尔金主断裂东端早更新世冲积相砾岩的追踪,发现疏勒河古冲积扇沉积的西边界距现今疏勒河河口约 10km,由此提出了阿尔金主断裂东端第四纪以来左行走滑错动 10km的沉积学新证据。通过对疏勒河河口阶地的分析,认为疏勒河河道沿阿尔金主断裂 2 8km的肘状弯曲除主要反映了断裂的左行走滑外,可能还包含了河流弯折段侧向侵蚀因素的影响。对阿尔金主断裂东端第四纪期间的位错量和走滑速率进行了讨论     

郯庐断裂带重岗山—王迁段晚更新世以来的活动习性

活动断裂最新错动与地震事件的关系是重要的基础研究课题。文中选定郯庐断裂带泗洪县重岗山—王迁段,开挖大型探槽,识别编录晚第四纪以来变形和史前地震事件,分析其活动期次和特性。结果表明,郯庐断裂带重岗山—王迁段晚第四纪以来曾发生强烈的挤压逆冲活动,在重岗山表现为晚白垩世砖红色砂岩向西高角度逆冲于晚更新世黄褐色黏土之上,在王迁则表现为黄白色上新世砂岩向西逆覆于晚第四纪沉积之上,且存在部分张裂现象。通过14C测年分析,得到重岗山—王迁段的2次古地震事件,其年代依次为(11 755±45)~(10 525±45)a BP与(10 135±50)a BP。郯庐断裂带重岗山—王迁段晚更新世以来逆冲活动强烈,而且一直持续到全新世初期。     

晚第四纪以来香山-天景山断裂左旋走滑量研究

香山-天景山断裂是青藏高原东北缘弧形断裂带中一条重要的活动断裂,长期以来活动强烈,早期以挤压逆冲为主,可能在第四纪早期转变成以左旋走滑为主兼具逆冲性质的断裂.黄河在夜明山前缘穿过此断裂,在沙坡头大弯一带形成一个完美的“几”形拐弯.文中对沙坡头大弯一带黄河地貌、阶地特征、样品年龄进行了探查和分析测试,结果表明,距今170ka以来,香山-天景山断裂左旋位移量最大不超过880m,滑移速率＜5.18mm/a.     

右江断裂带晚更新世活动的若干地质地貌证据及位移速率

右江断裂带地处桂西断块区,有记载以来沿带曾发生40～50级地震15次,属中强地震带。笔者在室内卫片、航片、大比例尺地形图解译和分析的基础上,经野外实地调查,获得了断裂带晚更新世活动的若干地质地貌证据,实测了断裂的左旋位移数据。文中介绍了有关证据,并根据年龄数据,计算了断裂中、晚更新世以来的水平和垂直位移速率。断裂带在平面上分3大段,即百色以西段、百色—思林段、思林—坛洛段,各大段又可进一步分为若干个小段。断裂断错了距今(328±025)×104a～(1016±079)×104a的阶地堆积物和残坡积物,控制着百色—田东晚第四纪盆地的发育,地貌上形成断层谷和槽地、断层崖和陡坎,横穿断裂的水系发生同步左旋位移,其活动性质以左旋走滑为主,兼有张性差异运动。晚更新世不同时段以来断裂的水平位移速率为147～198mm/a,中更新世以来的垂直位移速率为074～076mm/a,晚更新世以来为01～035mm/a。该断裂的位移速率明显低于其西的川滇断块内部断裂,更低于川滇断块周边断裂     

晚更新世以来黄土塬区临潼-长安断裂的活动性研究

黄土塬区晚更新世风成黄土分布广、特征明显,与断裂关系直接.通过小鲍陂、桥沟、冢底村3个典型晚更新世断层剖面的仔细观察、测量和年代学工作,获得了白鹿塬、少陵塬、横岭塬3个黄土台塬上临潼-长安断裂晚更新世以来的活动性参数和区域地层的年代序列.研究结果表明,晚更新世以来临潼-长安断裂在白鹿塬段活动性最强,明显错断了黄土L1-2地层,而其两侧的少陵塬和横岭塬上,同时期断裂的活动性相对弱些.剖面中黄土L1-2及其以上地层被裂缝穿切的现象有可能说明,晚更新世中晚期以来临潼-长安断裂仍在活动,仅是强度有所减弱.     

GEOLOGICAL AND GEOMORPHIC EXPRESSIONS OF LATE QUATERNARY STRIKE-SLIP ACTIVITY ON JINTA NANSHAN FAULT IN NORTHERN EDGE OF QING-ZANG BLOCK

Jinta Nanshan Fault is an important fault in northeast front of Qing-Zang Plateau, and it is crucial for determining the eastern end of Altyn Tagh Fault. However, there is still debate on its significant strike-slip movement. In this paper, we study the Late Quaternary activity of Jinta Nanshan Fault and its geological and geomorphic expressions by interpreting aerial photographs and high-resolution remote sensing images, surveying and mapping of geological and geomorphic appearances, digging and clarifying fault profiles and mapping deformation characteristics of micro-topographies, then we analyze whether strike-slip activity exists on Jinta Nanshan Fault. We get a more complete fault geometry than previous studies from most recent remote sensing images. Active fault traces of Jinta Nanshan mainly include 2 nearly parallel, striking 100°~90° fault scarps, and can be divided into 3 segments. West segment and middle segment form a left stepover with 2~2.5km width, and another stepover with 1.2km width separates the middle and east segment. We summarize geomorphic and geologic evidence relating to strike slip activity of Jinta Nanshan Fault. Geomorphic expressions are as follows:First, fault scarps with alternating facing directions; second, sinistral offset of stream channels and micro-topographies; third, pull-apart basins and compressive-ridges at discontinuous part of Jinta Nanshan Fault. Geologic expressions are as follows:First, fault plane characteristics, including extremely high fault plane angle, unstable dip directions and coexistence of normal fault and reverse fault; second, flower structures. Strike-slip rate was estimated by using geomorphic surface age of Zheng et al.(2013)and left-lateral offset with differential GPS measurements of the same geomorphic surface at field site in Fig. 4e. We calculated a strike-slip rate of (0.19±0.05)mm/a, which is slightly larger than or almost the same with vertical slip rate of (0.11±0.03)mm/a from Zheng et al.(2013). When we confirm the strike-slip activity of Jinta Nanshan, we discuss its potential dynamic sources:First, eastern extension of Altyn Tagh Fault and second, strain partitioning of northeastward extension of Qilian Shan thrust belt. The first one is explainable when it came to geometric pattern of several E-W striking fault and eastward decreasing strike slip rate, but the former cannot explain why the Heishan Fault, which locates between the the Altyn Tagh Fault and Jinta Nanshan Fault, is a pure high angle reverse fault. The latter seems more explainable, because oblique vectors may indeed partition onto a fault and manifest strike-slip activity.     

SLIP RATES OF THE RIYUE MT. FAULT AT DEZHOU SEGMENT SINCE LATE PLEISTOCENE

The Riyue Mt. Fault is a secondary fault controlled by the major regional boundary faults (East Kunlun Fault and Qilian-Haiyuan Fault). It lies in the interior of Qaidam-Qilianshan block and between the major regional boundary faults. The Riyue Mt. fault zone locates in the special tectonic setting which can provide some evidences for recent activity of outward extension of NE Tibetan plateau, so it is of significance to determine the activity of Riyue Mt. Fault since late Pleistocene to Holocene. In this paper, we have obtained some findings along the Dezhou segment of Riyue Mt. Fault by interpreting the piedmont alluvial fans, measuring fault scarps, and excavating trenches across the fault scarp. The findings are as follows:(1) Since the late Pleistocene, there are an alluvial fan f_p and three river terraces T₁-T₃ formed on the Dezhou segment. The abandonment age of f_p is approximately (21.2±0.6) ka, and that of the river terrace T₂ is (12.4±0.11) ka. (2) Since the late Pleistocene, the dextral strike-slip rate of the Riyue Mt. Fault is (2.41±0.25) mm/a. In the Holocene, the dextral strike-slip rate of the fault is (2.18±0.40) mm/a, and its vertical displacement rate is (0.24±0.16) mm/a. This result indicates that the dextral strike-slip rate of the Riyue Mt. Fault has not changed since the late Pleistocene. It is believed that, as one of the dextral strikeslip faults, sandwiched between the the regional big left-lateral strike-slip faults, the Riyue Mt. Fault didn't cut the boundary zone of the large block. What's more, the dextral strike-slip faults play an important role in the coordination of deformation between the sub-blocks during the long term growth and expansion of the northeast Tibetan plateau.     

肃北野马河北侧断裂地貌特征及其晚第四纪活动性

阿尔金活动断裂带东段的滑动速率由西向东逐渐减小,而肃北是阿尔金断裂东段滑动速率的"突变点"之一。在肃北以东分布多条分支断裂,野马河北侧断裂便是其中的一条。野马河北侧断裂长约30km,总体走向NEE,该断裂沿野马河盆地北侧山前洪积扇延伸,沿断裂具有大量的左旋走滑和逆冲等地貌现象,多处冲沟出露有断层剖面。野外调查结果表明该断裂是一条左旋走滑兼逆冲断裂,错断了晚更新世时期形成的洪积扇或冲沟阶地。通过实测得到地貌面左旋、垂直错动数据,并采集样品测试相关地貌面的年龄,估算该断裂晚更新世以来的平均水平滑动速率为(1.27±0.18)mm/a,平均逆冲速率为(0.4±0.07)mm/a,该断裂分解了阿尔金断裂东段的部分运动量     

阿尔金构造系晚更新世中晚期以来的逆冲活动

在阿尔金构造系中,阿尔金走滑断裂具有逆冲分量。文中将阿尔金构造系的逆冲活动分为西、中、东3段描述。西段从阿依耐克至车尔臣河河口,阿尔金南缘断裂具有逆冲活动迹象,在山前发育了规模较小的逆冲断层,有较新的地貌面被错动;中段从车尔臣河河口至拉配泉一带,在阿尔金山北缘发育大规模的逆冲断层,有较新的地貌面被错动;东段从拉配泉至宽滩山,逆冲断层有2种形式,此段阿尔金北缘断裂有逆冲分量,同时在阿尔金山北缘及山前冲洪积扇上发育逆冲断裂。自晚更新世中晚期以来,中段及东段逆冲速率<2mm/a。中段西部江尕拉萨依地区自16kaBP以来逆冲速率约为0.33mm/a,中部米兰桥一带自32kaBP以来的逆冲速率约为1.42mm/a。东段最大的逆冲速率在近中部的团结乡,自约5.31kaBP以来达到约1.81mm/a,向东西两端有减小的趋势,在西部柳城子自约72.36kaBP以来的逆冲速率为0.57mm/a,而东端的红柳沟自约8.99kaBP以来仅为0.05mm/a。团结乡地区约自19kaBP以来,逆冲活动有增强的趋势