香山-天景山断裂活动时代的光释光测年

在青藏高原东北隅发育一系列向北东凸出的弧形断裂带．其中最主要的三条断裂带从北到南分别为牛首山-罗山断裂带、香山-天景山断裂带和天祝一海原断裂带。香山-天景山断裂带从上世新以来一直有过活动,并在1709年发生了中卫南7t／2级地震。近期,宁夏地震局在孟家湾村南开挖了一个探槽．揭露出石炭纪的煤系地层逆冲于晚更新世风成沙之上．根据风成沙光释光测年结果表明。此探槽显示的断裂活动时代在距今约26．14±1．08ka．极有可能为22．09±0．4ka与26．14±1．08ka之间．     

库布齐现代沙漠景观发育的沉积学及光释光年代学证据

通过对库布齐沙漠5条南北向断面上的12个探坑和剖面的考察,分析了现代库布齐沙漠景观及下伏地层结构,发现该沙漠风沙沉积直接覆盖于冲洪积相／湖相沉积地层之上．石英的双单片再生法（DoubleSAR）光释光（OSL）测年结果表明,库布齐沙漠的西北部和东部地区最迟分别在距今19和9ka前后开始风沙堆积,在距今7ka风沙活动显著增强,特别是在距今2ka以来,沙漠向南和北扩展,现代库布齐沙漠景观开始形成．库布齐地区距今19,9和7ka前后的风沙堆积可能受到亚洲夏季风衰退的影响,距今2ka前后现代库布齐沙漠地貌景观的形成则更多地受到人类活动的触发．     

临潼-长安断裂上断层崩积楔光释光测年的探讨

选择西安临潼-长安断裂带上韩峪乡范家村剖面的一个典型崩积楔样品进行测试.用3种不同的释光测试方法测出了9个不同的年龄数据.根据地层信息和矿物的释光生长曲线确定只有采用混合矿物简单多片再生法、纯石英矿物简单多片再生法以及纯石英矿物单片再生法的光释光测年法所得结果更接近于崩积楔的真实年龄.这些断层崩积楔年龄接近于围岩的形成...     

浑善达克沙地的光释光年代序列与全新世气候变化

浑善达克沙地具有对气候变化响应敏感和生态环境脆弱的特点,是研究环境变化的理想地区．相对于黄土而言,沙质沉积是近源、在沉积期堆积速率快,有可能记录了某些时间段千年时间尺度的干旱事件．应用光释光测年技术,对浑善达克沙地东北．西南断面上具代表性的10个沙丘和沙／黄土剖面进行了年代测试,获得了35个样品的光释光年龄;结合野外地层观察分析和粒度、磁化率等测试,得到了浑善达克沙地全新世干旱事件和相对湿润期的气候变化记录：在距今9．9～8．2ka期问,沙地发育厚层粗砂层,沙丘处于活动状态,气候干燥,植被覆盖度低;在距今8．0～2．7ka期间,沙地发育有多层浅灰一灰黑色砂质土壤,沙丘总体上处于固定．半固定状态（也含有短时段的沙丘活化的干旱事件）,指示气候较之前明显湿润,植被相对茂密;2．3ka以来,沙地沉积物以粗砂堆积为主,沙丘又重新活化,气候总体上为干旱．通过对沙丘沉积记录和沉积产状的分析,发现浑善达克沙地在全新世早期、8．2ka前后以及小冰期时期,气候较为干旱,植被盖度小,沙丘活化;在“隋唐暖期”和“中世纪温暖期”,气候较湿润,植被发育良好,沙丘固定．具有绝对释光年龄控制的沙丘沉积记录表明,全新世浑善达克沙地多次千年时间尺度的气候事件可能是全球气候变化的区域响应．     

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.     

北京延庆断层崩积物记录的古地震事件释光测年研究

对北京延庆西羊房古地震探槽西壁采集的10个崩积物和坡面沉积物样品进行了细颗粒（4－11μm）多测片的红外释光（IRSL）和绿光释光（GLSL）测年。其中4个样品既在中国地震局地质研究所用Daybreak仪器作了测量，也在澳大利亚Adelaide大学物理系用Risφ仪器作测量，其结构基本一致。该探槽剖面见4个断层崩积楔，可视为4次古地震事件的记录。释光测年表明，最新一个崩积楔有可能是公元294年延庆东居庸村6级地震的质记录，大约在1．7－20kaBP或1．724kaBP期间至不有两次强烈地震事件。本文还对比了细颗粒GLSL与IRSL的测年结果。     

大柴旦断裂中段晚第四纪活动特征

通过航卫片遥感数据解译、野外地质地貌调查,并结合差分GPS等测量手段,获取大柴旦断裂晚第四纪以来的地质地貌特征。结果显示：大柴旦断裂总长约135 km,整体上显示为一反“S”形,根据断裂走向的变化、地貌特征、活动强弱等,大致以温泉沟、塔塔棱河为分界点,可将大柴旦断裂分为三段。晚第四纪以来,该断裂北段和南段逆冲性质较为明显。本次工作集中在断裂中段,该段以右旋逆冲活动为主,逆冲量和右旋量在不同地貌面上是不同的,显示出明显的多期次活动特征。野外天然古地震剖面揭示出1次古地震事件,发生在(2 402.5±57.5) a.B.P之后,表明该断裂在全新世活动强烈,与该区域近年来频繁的强震活动相吻合。     

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     

LATE QUATERNARY FAULTED LANDFORMS AND FAULT ACTIVITY OF THE HUASHAN PIEDMONT FAULT

Based on the 1︰50000 active fault geological mapping, combining with high-precision remote imaging, field geological investigation and dating technique, the paper investigates the stratum, topography and faulted landforms of the Huashan Piedmont Fault. Research shows that the Huashan Piedmont Fault can be divided into Lantian to Huaxian section (the west section), Huaxian to Huayin section (the middle section) and Huayin to Lingbao section (the east section) according to the respective different fault activity. The fault in Lantian to Huaxian section is mainly contacted by loess and bedrock. Bedrock fault plane has already become unsmooth and mirror surfaces or striations can not be seen due to the erosion of running water and wind. 10~20m high fault scarps can be seen ahead of mountain in the north section near Mayu gully and Qiaoyu gully, and we can see Malan loess faulted profiles in some gully walls. In this section terraces are mainly composed of T₁ and T₂ which formed in the early stage of Holocene and late Pleistocene respectively. Field investigation shows that T₁ is continuous and T₂ is dislocated across the fault. These indicate that in this section the fault has been active in the late Pleistocene and its activity becomes weaker or no longer active after that. In the section between Huaxian and Huayin, neotectonics is very obvious, fault triangular facets are clearly visible and fault scarps are in linear distribution. Terrace T₁, T₂ and T₃ develop well on both sides of most gullies. Dating data shows that T₁ forms in 2~3ka BP, T₂ forms in 6~7ka BP, and T₃ forms in 60~70ka BP. All terraces are faulted in this section, combing with average ages and scarp heights of terraces, we calculate the average vertical slip rates during the period of T₃ to T₂, T₂ to T₁ and since the formation of T₁, which are 0.4mm/a, 1.1mm/a and 1.6mm/a, and among them, 1.1mm/a can roughly represent as the average vertical slip rate since the middle stage of Holocene. Fault has been active several times since the late period of late Pleistocene according to fault profiles, in addition, Tanyu west trench also reveals the dislocation of the culture layer of(0.31~0.27)a BP. 1~2m high scarps of floodplains which formed in(400~600)a BP can be seen at Shidiyu gully and Gouyu gully. In contrast with historical earthquake data, we consider that the faulted culture layer exposed by Tanyu west trench and the scarps of floodplains are the remains of Huanxian M_S8½ earthquake. The fault in Huayin to Lingbao section is also mainly contacted by loess and mountain bedrock. Malan loess faulted profiles can be seen at many river outlets of mountains. Terrace geomorphic feature is similar with that in the west section, T₁ is covered by thin incompact Holocene sand loam, and T₂ is covered by Malan loess. OSL dating shows that T₂ formed in the early to middle stage of late Pleistocene. Field investigation shows that T₁ is continuous and T₂ is dislocated across the fault. These also indicate that in this section fault was active in the late Pleistocene and its activity becomes weaker or no longer active since Holocene. According to this study combined with former researches, we incline to the view that the seismogenic structure of Huanxian M_S8½ earthquake is the Huashan Piedmont Fault and the Northern Margin Fault of Weinan Loess, as for whether there are other faults or not awaits further study.     

龙门山映秀-北川断裂带擂鼓探槽剖面古地震事件测年

2008年5月12日四川汶川发生MS8.0大地震,形成了200多km长的地震地表破裂带。破裂带的古地震研究对于认识龙门山断裂带的活动习性和大地震的发生规律具有重要的理论和现实意义。文中用光释光(OSL)测年中的校正感量简单多片再生法(SMAR),对映秀-北川地震地表破裂带擂鼓探槽样品进行了光释光测年,并对探槽中含有的炭屑进行了AMS14C测年。样品的光释光年龄和校正的AMS14C年龄吻合,该地区与汶川地震类似规模的上一次古地震事件发生在距今约(2.1±0.2)ka至(1.1±0.2)ka间     

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。     

山西峨嵋台地北缘断裂晚第四纪活动性

通过1/5万活断层地质填图,对山西峨嵋台地北缘断裂晚第四纪活动性进行了详细研究。以谭家庄、南柳附近的2个阶区为界,将断裂分为西、中、东3段。谭家庄以西该断裂中更新世早期有过活动,之后未见明显活动迹象。谭家庄至南柳之间断裂晚更新世以来活动强烈,全新世仍有活动,最新活动发生在(2.00~1.29)ka BP,晚更新世晚期以来滑动速率≥0.36mm/a。南柳至西彰坡段晚更新世以来活动明显,尚未发现全新世活动的直接证据,晚更新世以来断层滑动速率≥0.1mm/a。     

阿尔金断裂带东段晚更新世阶地沉积物红外释光测年及其构造意义

对流经阿尔金断裂带东段的段家沙河、疏勒河和踏实河的阶地沉积物进行了细颗粒多测片红外释光(IRSL)测年,初步确定了晚第四纪各级阶地的形成年代和构造抬升速率。疏勒河在昌马盆地南缘发育7级阶地,光释光测年结果显示这些总高度超过100m的阶地可能主要形成于数万年以内,抬升速率约为2.5mm/a;照壁山峡谷疏勒河保留有5级阶地,大致形成于20万年前,阶地的抬升速率约为0.7mm/a;段家沙河在红柳峡上形成4级阶地,形成于距今7万年以来,其抬升速率约为06mm/a     

北部湾涠洲岛南湾火山砂岩捕虏体光释光(OSL)测年结果

涠洲岛是北部湾内的一座火山岛,火山活动初步可以分为早-中更新世和晚更新世2期。晚期南湾火山是典型的射气岩浆喷发成因的火山,文中报道了南湾火山的上、下2层火山碎屑岩中砂岩捕虏体的光释光(OSL)测年结果,提出南湾火山喷发时代为距今约3万年左右的晚更新世末期     

安徽南部头坡断裂的活动性研究

对位于安徽南部的头坡断裂的野外调查表明,沿头坡断裂没有明显的水平或垂向错动的地貌现象;在取得的剖面中,上覆第四纪地层均未被断裂断错,表明断裂在中、晚更新世以来没有活动。对本区地貌、第四纪地层和断裂活动历史的调查分析表明,该断裂在燕山运动晚期(侏罗纪末—早白垩世)和喜马拉雅运动早期(晚白垩世—古近纪)有过2次强烈活动,前者表现为左旋走滑运动,后者以拉张活动为特征。新近纪以来全区处于长期隆升剥蚀状态,缺失新近系,第四系厚度不大,残坡积地层广泛发育,构造运动微弱。头坡断裂的活动历史及新活动性与其相邻的郯庐断裂带南段相似,前者可能受后者的控制     

新疆民丰县皮什盖-塔勒克勒格断裂带的第四纪活动特征

皮什盖-塔勒克勒格断裂将蓟县系逆掩于第四系之上，中更新世之前的西域变动显著，现今地震活动不强烈。其分支断裂帕西木断裂在中更新世之后，由正断层变为压性断层。     

EVIDENCE OF HOLOCENE ACTIVITY DISCOVERED IN ANHUI ZIYANGSHAN SEGMENT OF TANLU FAULT ZONE

Anqiu-Juxian Fault(F₅) is the latest active fault in the eastern graben of the middle segment of the Tanlu fault zone. In recent years, the research results of F₅ in Jiangsu Province are abundant, and it is found that Holocene activity is prevalent in different segments, and the movement pattern is dominated by dextral strike-slip and squeezing thrust. The Anhui segment and the Jiangsu segment of the Tan-Lu fault zone are bounded by the Huaihe River. Previous studies have not discussed the extension and activity of F₅ in the south of the Huaihe River in Anhui Province. This paper chooses the Ziyangshan segment of Tanlu fault zone in the south of the Huaihe River as the breakthrough point, which is consistent with the linear image feature of extension of F₅ in Jiangsu Province. Through the remote sensing image interpretation, geological and geomorphological investigation and trench excavation, we initially get the following understanding:(1)The linear structural features of the Ziyang segment are clear, and the fault is developed on the gentle slope of the Mesozoic red sandstone uplift along the Fushan-Ziyangshan, which is the southern extension of the Anqiu-Juxian Fault(F₅); (2)The excavation of the Zhuliu trench reveals that the late Pleistocene clastic layers are interrupted, and the late late Pleistocene to early Holocene black clay layers are filled along the fault to form black fault strips and black soil-filled wedges, indicating that the latest active age of the fault is early Holocene; (3)The excavation of Zhuliu trench reveals that there are at least 3 paleo-earthquake events since the Quaternary, the first paleo-seismic event is dated to the early and middle Quaternary, and the 2nd paleo-seismic event is 20.10~13.46ka BP, the age of the third paleo-seismic event is(10.15±0.05)~(8.16±0.05)ka BP. These results complement our understanding of the late Quaternary activity in the Anhui segment of the Tanlu fault zone, providing basic data for earthquake monitoring and seismic damage prevention in Anhui Province.