灵武断裂晚第四纪活动特征及位移速率

灵武断裂是银川地堑南段的东侧构造边界,与灵武-吴忠地区的地震活动有密切的关系,以往研究程度较低.作者通过实际调查、探槽开挖、年代侧定、相关地貌年代测定、断错历史研究等方面的大量工作对该断层晚第四纪的活动性开展了比较系统的野外考察.本文以野外考察获得的资料为基础,论述了该断层晚第四纪的活动特征,估计了其垂直位移速率.     

灵武断裂晚第四纪活动特征及位称速率

灵武断裂是银川地堑南段的东侧构造边界,与灵一吴忠地区的地震活动有密切的关系,以往研究程度较低。作者通过实际调查、探槽开挖、年代侧定、相关地貌 年代测定、断错历史研究等方面的大量工作对该断层晚第四纪的活动性开展了比较系统的野外考察。本文以野外考察获得的资料为基础,论述了该以晚第四纪的活动特征,估计了其垂直位移速率。     

天山南缘北轮台断裂库尔楚段晚第四纪的最新活动和滑动速率

使用全站仪实测了天山南麓北轮台逆断裂库尔楚段阿克艾肯－喀腊萨喀腊阿塔木冲洪积扇断层崖地形地貌，采用^10Be测年方法测定了该冲洪积扇的形成年龄，得到该断裂段垂直位移滑动速率为0.48mm/a、0.85-1.0mm/a和1.52mm/a，并对该断裂段的水平缩短速率和天山第四纪水平缩短量进行了讨论。     

西南天山迈丹断裂东段晚第四纪活动的发现及构造意义

利用详细的遥感影像解译、实地调查、探槽开挖以及释光年代学测定的方法对西南天山山前的迈丹断裂东段进行研究,获得了该断裂晚第四纪以来活动的可靠证据。迈丹断裂东段是一条由多条次级断裂组成的复杂断裂带,最大宽度可达17km,晚第四纪以来的活动断错了山前各级地貌面和阶地。探槽开挖表明,断裂在全新世期间曾发生过断错地表的强震事件,造成的垂直位错量在2m以上。迈丹断裂晚第四纪以来活动表明,西南天山地区的构造变形并不完全集中在推覆体前缘新生的逆断裂-背斜带上,天山根部断裂也吸收了一部分构造变形。这一构造变形模式与已知的北天山前展式的构造变形样式具有明显差异,柯坪推覆体并不完全遵从断裂新活动不断向盆地方向扩展的特点,推覆体前缘新生断裂和根部断裂都有较强的活动,可能是一种无序或反序的构造变形样式。此类构造,其发震构造模型的建立及强震危险性预测给我们带来新的挑战。     

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。     

晚第四纪安宁河断裂的新活动与特征

由２０余条次级断层组成的晚第四纪安宁河断裂是一条以左旋走滑为主兼逆冲性质的断裂。它的发育，展布，组合结构特征都与先存的南北澳断裂紧相关，并表现出明显的分段活动特性。     

库车坳陷东秋里塔格断裂晚第四纪活动和滑动速率

东秋里塔格断裂是库车坳陷内活动最为强烈的断裂之一,断错了波斯坦托克拉克河两岸的各级阶地。利用全站仪对河西岸的阶地变形进行了精确测量,得到Ⅰ、Ⅱ、Ⅲ级阶地形成以来东秋里塔格断裂的垂直断错量分别为12.5 m、20 m和24.5 m,并根据前人资料和区域类比的方法对各级阶地年龄进行了估计,计算得到晚第四纪以来该断裂的平均垂直滑动速率为1 mm/a左右,所引起的地壳缩短速率为(1.97~2.13)mm/a。     

罗布泊捷山子断裂晚第四纪活动特征

位于罗布泊的捷山子断裂,在航、卫片上线性影像清晰,平面上由2-3条断层组成。罗布泊东台地以东,断裂在地貌上构成较宽阔的断裂谷地或断陷盆地的边界,同时也构成了元古界、花岗岩体与古近系、新近系以及第四系的分界。在罗布泊东台地断裂切割由中更新世—晚更新世湖积物构成的东台地（雅丹地貌）。在赛里克沙依断陷盆地,断裂断错了晚更新世晚期洪积扇及冲沟Ⅰ、Ⅱ级阶地,并形成长约40 km的断层陡坎。捷山子断裂的中、西段在晚更新世有过显著的活动。     

LATE-QUATERNARY ACTIVITY OF THE YALAHE FAULT OF THE XIANSHUIHE FAULT ZONE,EASTERN MARGIN OF THE TIBET PLATEAU

Complex geometrical structures on strike-slip faults would likely affect fault behavior such as strain accumulation and distribution, seismic rupture process, etc. The Xianshuihe Fault has been considered to be a Holocene active strike-slip fault with a high horizontal slip rate along the eastern margin of the Tibetan plateau. During the past 300 years, the Xianshuihe Fault produced 8 earthquakes with magnitude≥7 along the whole fault and showed strong activities of large earthquakes. Taking the Huiyuansi Basin as a structure boundary, the northwestern and southeastern segments of the Xianshuihe Fault show different characteristics. The northwestern segment, consisting of the Luhuo, Daofu and Qianning sections, shows a left-stepping en echelon pattern by simple fault strands. However, the southeastern segment(Huiyuansi-Kangding segment)has a complex structure and is divided into three sub-faults: the Yalahe, Selaha and Zheduotang Faults. To the south of Kangding County, the Moxi segment of the Xianshuihe Fault shows a simple structure. The previous studies suggest that the three sub-faults(the Yalahe, Selaha and Zheduotang Faults of the Huiyuansi-Kangding segment)unevenly distribute the strain of the northwestern segment of the Xianshuihe Fault. However, the disagreement of the new activity of the Yalahe Fault limits the understanding of the strain distribution model of the Huiyuansi-Kangding segment. Most scholars believed that the Yalahe Fault is a Holocene active fault. However, Zhang et al.(2017)used low-temperature thermochronology to study the cooling history of the Gongga rock mass, and suggested that the Yalahe Fault is now inactive and the latest activity of the Xianshuihe Fault has moved westward over the Selaha Fault. The Yalahe Fault is the only segment of the Xianshuihe Fault that lacks records of the strong historical earthquakes. Moreover, the Yalahe Fault is located in the alpine valley area, and the previous traffic conditions were very bad. Thus, the previous research on fault activity of the fault relied mainly on the interpretation of remote sensing, and the uncertainty was relatively large. Through remote sensing and field investigation, we found the geological and geomorphological evidence for Holocene activity of the Yalahe Fault. Moreover, we found a well-preserved seismic surface rupture zone with a length of about 10km near the Yariacuo and the co-seismic offsets of the earthquake are about 2.5~3.5m. In addition, we also advance the new active fault track of the Yalahe Fault to Yala Town near Kangding County. In Wangmu and Yala Town, we found the geological evidence for the latest fault activity that the Holocene alluvial fans were dislocated by the fault. These evidences suggest that the Yalahe Fault is a Holocene active fault, and has the seismogenic tectonic condition to produce a large earthquake, just like the Selaha and Zheduotang Faults. These also provide seismic geological evidence for the strain distribution model of the Kangding-Huiyuansi segment of the Xianshuihe Fault.     

二台断裂南段的第四纪活动

二台断裂南段在乌伦古河流域分叉、折尾,显示出破裂末端特征。据断层活动资料,自晚更新世中期以来南段有5次活动,主要为右旋逆走滑活动,末端为右旋正走滑。水平错动幅度达3个量级4个梯度,最大达350m。1984—1988年形变测量资料表明该段目前正以2.1mm/年的速率作左旋旷动。各种古地震活动标志表明南段大震平均复现期为3500±290年。     

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     

小江断裂带第四纪晚期左旋走滑速率及其构造意义

位于中国西南的小江 (Xiaojiang)断裂带作为康定 (Kangding)断裂带的南段 ,在青藏块体向SE方向挤出的过程中起着重要的作用。根据断错地貌以及这些断错地貌14 C年代或热释光年代 ,推算了小江断裂带第四纪晚期的左旋走滑速率。小江断裂带可以分为 3段 ,其中段由平行的两条断层组成。西支断层和东支断层的左旋走滑速率分别为 7.0～ 9.0mm/ yr和 6 .0～ 7.5mm/yr。简单相加 ,就可以推算出小江 (Xiaojiang)断裂带总的左旋走滑速率为 13 0～ 16 5mm/ yr,与康定断裂带北段的鲜水河 (Xianshuihe)断层的走滑速率大致相当 ,约等于康定 (Kangding)断裂带中段的安宁河 (Anninghe)断层及则木河 (Zemuhe)断层的两倍。这个结果可能暗示了在康定断裂带中段 ,可能存在着其他断层以解消另外一半的滑动速率。最有可能的断层是位于康定断裂带中段以东几十公里的普雄河 -布拖 (Puxionghe Butuo)断层     

抚顺城区段浑河断裂现今活动性研究的述评

对以往关于抚顺城区段浑河断裂现今构造活动性的主要文献所采用的地壳形变测量资料及其结论的科学性作了述评，认为得出的抚顺城区段浑河断裂现今构造活动明显或不明显的结论尚缺乏充分的依据，提出了进一步研究该断裂现今构造活动性的建议与方法。     

THE LATE QUATERNARY ACTIVITY FEATURES AND SLIP RATE OF THE YANGGAO-TIANZHEN FAULT

The Shanxi Graben System is one of the intracontinental graben systems developed around the Ordos Block in North China since the Cenozoic, and it provides a unique natural laboratory for studying the long-term tectonic history of active intracontinental normal faults in an extensional environment. Comparing with the dense strong earthquakes in its central part, no strong earthquakes with magnitudes over 7 have been recorded historically in the Jin-Ji-Meng Basin-and-Range Province of the northern Shanxi Graben System. However, this area is located at the conjunction area of several active-tectonic blocks(e.g. the Ordos, Yan Shan and North China Plain blocks), thus it has the tectonic conditions for strong earthquakes. Studying the active tectonics in the northern Shanxi Graben System will thus be of great significance to the seismic hazard assessment. Based on high-resolution remote sensing image interpretations and field investigations, combined with the UAV photogrammetry and OSL dating, we studied the late Quaternary activity and slip rate of the relatively poorly-researched Yanggao-Tianzhen Fault(YTF)in the Jin-Ji-Meng Basin-and-Range Province and got the followings: 1)The YTF extends for more than 75km from Dashagou, Fengzhen, Inner Mongolia in the west to Yiqingpo, Tianzhen, Shanxi Province in the east. In most cases, the YTF lies in the contact zone between the bedrock mountain and the sediments in the basin, but the fault grows into the basin where the fault geometry is irregular. At the vicinity of the Erdun Village, Shijiudun Village, and Yulinkou Village, the faults are not only distributed at the basin-mountain boundary, we have also found evidence of late Quaternary fault activity in the alluvial fans that is far away from the basin-mountain boundary. The overall strike of the fault is N78°E, but the strike gradually changes from ENE to NE, then to NWW from the west to the east, with dips ranging from 30° to 80°. 2)Based on field surveys of tectonic landforms and analysis of fault kinematics in outcrops, we have found that the sense of motion of the YTF changes along its strikes: the NEE and NE-striking segments are mainly normal dip-slip faults, while the left-laterally displaced gullies on the NWW segment and the occurrence characteristics of striations in the fault outcrop indicate that the NWW-striking segment is normal fault with minor sinistral strike-slip component. The sense of motion of the YTF determined by geologic and geomorphic evidences is consistent with the relationship between the regional NNW-SSE extension regime and the fault geometry. 3)By measuring and dating the displaced geologic markers and geomorphic surfaces, such as terraces and alluvial fans at three sites along the western segment of the YTF, we estimated that the fault slip rates are 0.12~0.20mm/a over the late Pleistocene. In order to compare the slip rate determined by geological method with extension rate constrained by geodetic measurement, the vertical slip rates were converted into horizontal slip rate using the dip angles of the fault planes measured in the field. At Zhuanlou Village, the T₂ terrace was vertically displaced for(2.5±0.4)m, the abandonment age of the T₂ was constrained to be(12.5±1.6)ka, so we determined a vertical slip rate of(0.2±0.04)mm/a using the deformed T₂ terrace and its OSL age. For a 50°dipping fault, it corresponds to extension rate of(0.17±0.03)mm/a. At Pingshan Village, the vertical displacement of the late Pleistocene alluvial fan is measured to be(5.38±0.83)m, the abandonment age of the alluvial fan is(29.7±2.5)ka, thus we estimated the vertical slip rate of the YTF to(0.18±0.02)mm/a. For a 65° dipping fault, it corresponds to an extension rate of(0.09±0.01)mm/a. Ultimately, the corresponding extensional rates were determined to be between 0.09mm/a and 0.17mm/a. Geological and geodetic researches have shown that the northern Shanxi Graben System are extending in NNW-SSE direction with slip rates of 1~2mm/a. Our data suggests that the YTF accounts for about 10% of the crustal extension rate in the northern Shanxi Graben System.     

THE LATE QUATERNARY ACTIVITY CHARACTERISTICS OF THE STRIKE-SLIP FAULTS IN THE TIANSHAN OROGENIC BELT: A CASE STUDY OF THE KAIDUHE FAULT

As the most active intracontinental orogenic belt in the world, the Tianshan orogenic belt has complex and diverse internal structural deformation patterns, and among them, the particularly striking is the linear straight U-type valley landscapes which cut inside the mountains by multiple NW-SE and ENE-WSW strike-slip faults. Many of the modern strong earthquakes in Tianshan orogenic belt are closely related to these strike-slip faults. Therefore, it is important to elaborate the activity characteristics of these faults to understand the deformation process inside the Tianshan Mountains belt. This paper focuses on one of the NW-SE right-lateral strike-slip fault (the Kaiduhe Fault), which lies inside the southeastern Tianshan. Typical offset landforms and scarp lineaments on the western segment of the Kaiduhe Fault can be used to study the activity characteristics and strike-slip rate. In particular, the fault cuts through the late Quaternary alluvial fans and a series of river gullies were right-laterally faulted, producing dextral offsets ranging from 3 to 248m. A digital elevation model (DEM)with resolution of 0.25m was established by using multi-angle photogrammetry technique to stripe about 12km linear tectonic landforms along the Kaiduhe Fault. Geological and geomorphic mapping in DEM with 22 high-resolution dextral offset measurements reveals that the dextral offsets can be divide into four groups of 3.5m, 7.0m, 11.8m and 14.5m. It is presumed from the approximately uniformly-spaced offsets that the coseismic offset was 3~4m. In addition, the exposure age of an older alluvial fan surface was about 235.7ka by in situ ¹⁰Be terrestrial cosmogenic nuclide method. Combining the exposure ages and the maximum dextral offset of 248m, we found that the strike-slip rate of the Kaiduhe Fault is about 1mm/a. It is found by this study that the Kaiduhe Fault plays an important role in regulating SN compression deformation within Tianshan Mountains, and it should also be the main stress-strain accumulation area which has the risk of occurrence of strong earthquake.     

新疆古牧地断裂全新世的断错活动

新疆古牧地断裂是一条全新世活动断裂,全新世以来有４ 次明显的断错活动,历次活动的ＴＬ时间分别为１１．０３±０．８９ ｋａＢ．Ｐ．,９．７３±０．７９ ｋａＢ．Ｐ．,８．３２±０．６７ ｋａＢ．Ｐ．和６．８２±０．５４～４．８７±０．３９ ｋａＢ．Ｐ．,断错活动间隔为１．３±０．１～２．０±０．１５ ｋａ。全新世时期累积垂直断距大于５．０３ｍ ,平均活动速率大于０．４１ ｍ ｍ ／ａ