History of Paleoseismic Activity Along the Hohhot Segment of Daqingshan Piedmont Fault in the Late Quaternary

INTRODUCTIONTheDaqingshanpledmont扭nit Is an irllt,oltant active normal tsult In the active fault－depressionzone——Hetao ault－depression zone In the northern part of Ordos Block,North China．It lies in ENEdirection long the southern pledmont of Daqingshan Mountain,dips to south,and extends for 200 kmor。。The fault was formed In the Eocene and strongly activated In the Cenozolc．Its verticaldlspl。ement exceeds 2400 m since the Quaternary(Rese。h Group on Ordos Block,State…     

Characteristics of Late Quaternary Activity of the Gadê Segment in the Madoi-Gadê Fault Zone

Madoi-Gadê fault is an active fault in the Bayan Har block.According to field investigation,there is an earthquake surface rupture fairly well preserved on the Gadê segment of the Madoi-Gadê fault zone.The length of the rupture is approximately 50km,with a general strike of NW.The maximum horizontal sinistral displacement is about 7.6m and the maximum vertical displacement is about 4m.A large number of earthquake traces are to be found along the rupture zone,and the phenomena on the surface rupture are also...     

Characteristics of Paleoseismic Activity Along the TianqiaogouHuangyangchuan Fault on the Eastern Section of the Qilian Mountains

1INTRODUCTION TheTianqiaogou Huangyangchuanfault(alsocalledGulangfault)isanimportantpartofanactivefaultzoneontheeasternsectionofthenorthernQilianMountains.Therecentactivityofthefaulthasbeenstudiedtodifferentdegrees(WanFuling,1987;InstituteofGeology,StateS…     

Activity Feature of Kazkeaerte Fault Zone in the Late Quaternary

ＩＮＴＲＯＤＵＣＴＩＯＮＫａｚｋｅａｅｒｔｅｆａｕｌｔｚｏｎｅａｂｏｕｔ 1 0 0ｋｉｌｏｍｅｔｅｒｓｌｏｎｇ (Ｆｉｇ .1 ) ,ｉｓｔｈｅｅａｓｔｅｒｎｌｉｍｂｏｆｔｈｅｌａｔｅｓｔｄｅｆｏｒ ｍａｔｉｏｎｂｅｌｔｏｆｔｈｅｎｏｒｔｈｅｒｎｍａｒｇｉｎｏｆＰａｍｉｒｓ (ＣｈｅｎＪｉｅ ,ｅｔａｌ,1 997) .Ｍａｎｙｍｏｄｅｒａｔｅｌｙｓｔｒｏｎｇｅａｒｔｈ ｑｕａｋｅｓｏｃｃｕｒｒｅｄａｌｏｎｇｔｈｉｓｚｏｎｅ (ＦｅｎｇＸｉａｎｙｕｅ ,ｅｔａｌ,1 987) .ＴｈｅｌａｔｅＱｕａｔｅｒｎａｒｙｄｅｆｏｒｍａｔｉｏｎ…     

The Feature of Segmentation Activity on the Northern Segment of the Anninghe Fault Zone Since Late Pleistocene

Based on fault geometric features,composite pattern,faulting land-forms and seismic data,this paper discussed the activity behavior along the northern segment of the Anninghe fault(from Xichang to Shimian)since the Late Pleistocene.The fault can be divided into three active segments by discrepancies of their activity:the segment from Xichang to Mianning,the segment from Mianning to Zimakua,and the segment from Zimakua to Tianwan.The southern segment has the background of occurrence of great earthquakes,but the middle and the northern segments can generate strong and moderate events respectively.According to the features of quartz from fault gouges by scanning electron microscopy(SEM),this paper discussed the movement features along the fault and indicated the stick-slipping feature on the segment from Xichang to Zimakua,the creeping feature on the segment from Jiziping to Tianwan and the transitional feature on the segment in between.     

Active Fault and Volcanic Activity in the Longhai-Zhangpu Coastal Area, Fujian Province

INTRODUCTION TheLonghai ZhangpucoastalareaofFujianProvinceliesonthesouthernsideoftheoutletofthe JiulongjiangRiver.Tectonically,itislocatedonthesouthernsegmentoftheChangle Zhao’anfault zone.Previously,alotofseismogeologicresearchworkhasbeencarriedoutinthi…     

A Preliminary Study of Palaeoearthquakes on the Maqu Fault of East Kunlun Fault Zone

INTRODUCTIONThe east Kunlun active fault is an important NWWtrending boundary fault on the northeasternmargin of the Qinghai-Xizang(Tibet)Plateau.The fault extends fromthe northside of the Qiangtangmassif in the west,runs eastward through the Kusai Lake,Dongdatan,Xidatan,Tuosuo Lake andMaqu to the north of Zoig毢(Van Der Woerd,et al.,2002;Ma Yinsheng,et al.,2005;Seismological Bureau of Qinghai Province,et al.,1999;Li Chunfeng,et al.2004).The intenseleft-lateral strike-slip move…     

Geometry and Late Quaternary Kinematic Characteristics of the Huoshan Fault in Shanxi Province

The Huoshan fault is an important fault controlling the boundary of the Linfen basin at the middle transtensional segment of the Shanxi graben system.In this paper a discussion is made emphatically on the tectonic segmentation of the Huoshan fault,its internal geometric structures and characteristics of its activities since the late Quaternary on the basis of 1:10,000 scale geological mapping.Our investigations indicate that the Huoshan fault can be divided into 3 segments with different behaviors and structures.Among these 3,the shear segment with dextral movement is composed of a number of second-order shear faults in right-lateral stepover or left-lateral stepover arrangement.It has a maximum dextral displacement up to 9.83 km since the Pliocene,a dextral slip rate of 2.0 mm/a; a maximum vertical differential displacement of 3.44 km,and a differential oscillatory movement rate of 0.69 mm/a.The lower limit of dextral Holocene slip rate is about 5 mm/a.     

Research on Present Activity Characteristics of Heizi Fault and Discussion of Its Relative Problems

Based on other previous researches,we recalculate the micro-displacement along the Heizi fault with recent deformation data of the Heizi reservoir.The result shows that activity characteris-tics of Heizi fault has changed greatly since 1973 and have experienced four phases.The third phase is characteristics of normal fault, and others characteristic of reverse faults.Construct-ing the reservoir dam and reservoir sluice has important effect on present activity of the fault, even changed the activity characteristics of faults in some phases.Seismicity has some effect on deformation data and fault activity.     

Discussion of the Horizontal Intensity of Late Quaternary Fault Activity Along the Tianjingshan Fault Zone in Different Time Intervals and Fault Segments

By computing and classifying the data of gully offset obtained from field surveys along the Tianjingshan fault zone and estimating the ages of three types of gullies,the strike-slip rates along the fault zone are discussed in different time intervals and fault segments.The results suggest that the intensity of activity along the fault zone is not strong,but the differences between different time intervals and fault segments since the late Pleistocene have been obvious.The average rates range from 0.23 mm/a to 1.62 mm/a.The largest average rate is 1.40 mm/a,which occurred in the early and middle of late Pleistocene along the western segment of the fault zone.Since the late stage of the late Pleistocene,the center of faulting activity of the fault zone has shifted to the middle segment,and the average slip rates range have changed from 1.30 mm/a to 1.63 mm/a.     

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。     

郯庐断裂带五河-明光段晚更新世活动的地质证据及活动特征

作为中国东部影响最大的走滑断裂,郯庐断裂因其强烈的地震活动性及沿断裂带一系列的大地震而备受学者关注。然而,大部分的调查研究都是针对郯庐断裂山东省境内及渤海湾内部分段落。并且,一般认为淮河以南的段落晚更新世以来不活动,也不具备孕育大震或强震的条件。然而,近期我们针对郯庐断裂的工作对这些认识提出了质疑,这些工作基于高分辨率卫星遥感影像解译和在安徽北部明光市、五河县附近的详细的野外调查。我们的研究认为郯庐断裂在淮河以南的五河-明光段包括四支断裂,并且至少一支在晚更新世以来活动。此段在晚第四纪以来主要以右旋走滑为主。不同于常常在基岩及第四纪沉积物中观察到的断层,在未固结的第四纪粘土中的断层形迹不清,但是能够被微观构造分析所确认。鉴于我们最近的工作和前人研究,我们认为年轻沉积物中的隐形断层更加值得注意,同时我们认为郯庐断裂淮河以南的“平静”段需要更深入的研究。     

香港地区晚更新世的构造活动性

河沥背西北走向的断层最近期的构造活动发生于晚更新世时期,至全新世已经完全停止.晚更新世后期香港地区(如河沥背、黄竹洋、南山和贝澳)滑坡、泥石流和巨型滚石等重力地质事件频繁发生,而且还有原地重复的情况.按照地面地质破坏现象的分布范围、规模和数量等指针综合分析,在晚更新世后期香港地区可能曾经遭受过强烈地震的袭击,其烈度估计可达Ⅸ-Ⅹ度,而且在数万年之内曾经多次发生.1万年以来,构造运动减弱,地震活动降低,地面运动的最大强度相应减小.     

鄂尔多斯北缘断裂托克托段晚第四纪活动特征

鄂尔多斯北缘断裂作为河套断陷带和鄂尔多斯地块的边界断裂,研究其晚第四纪活动特征,对于科学评价黄河流域内蒙古河套段的地震危险性具有重要意义。本文利用野外地质调查、微地貌测量、浅层人工地震勘探及钻孔联合剖面探测相结合的方法,综合地层年代样品测试结果,确定了该断裂托克托段的准确位置和最新活动特征。研究结果表明,鄂尔多斯北缘断裂托克托段沿线构造地貌不发育,推测断裂的最新活动可能尚未达到地表,地表的地貌陡坎应为河流侵蚀成因。断裂在深、浅地震反射剖面上表现为“Ｙ”字形的张性断裂系,主断裂倾向北,分支断裂倾向南,整体上陡下缓,具有多个地堑式分布的特点。跨断裂钻孔联合剖面上显示,单个分支断裂的同震垂直位移量为2～2.5 m,最新活动时代为43.5～70 ka。鄂尔多斯北缘断裂是一条晚更新世活动的深大断裂,具有一定的地震危险性。     

白鹿塬中更新世以来的黄土—古土壤序列及断层活动特征分析

通过对白鹿塬高家沟内两套黄土—古土壤序列及断层错距的观察、测量和分析,获得了中更新世以来白鹿塬黄土—古土壤序列的地层划分和断层的部分活动性参数。结果表明:高家沟内S2和S3地层均由两层古土壤夹一层黄土复合而成,L7地层由两层黄土中间夹一层弱发育古土壤组成;中更新世以来,白鹿塬段一直存在断层活动,且断层活动具有空间差异性。     

嫩江断裂带北段的第四纪活动特征初步研究

嫩江断裂带是松辽盆地的西边界断裂,但受第四系强覆盖等研究条件的限制,前人对该断裂第四纪构造活动的研究较少。本文针对该断裂带北段开展了野外地质调查,并综合大地电磁测深和纵波速度结构等结果,初步研究了嫩江断裂带北段的第四纪活动特征。调查发现,该断裂北段主要发育地貌陡坎、基岩滑坡、地层揉皱变形、近垂直擦痕、基岩崩塌与线性断塞塘等特征。探槽古地震研究揭示断裂带北段在（80.9±4.6）—（62.9±2.3）ka BP曾发生1次古地震事件,运动方式为正断,垂直位移量约1.5m,震级约为M_S 7.1—7.3,断裂在晚更新世曾发生过强烈活动。研究结果有助于认识了解该断裂和松辽盆地的第四纪构造变形过程,并为评价该断裂及邻区的地震活动潜势提供参考。     

新疆阜康—吉木萨尔断层晚第四纪活动与变形特征的新认识

阜康—吉木萨尔断层是博格达山体与山前冲洪积平原的分界断层，全新世以来仍在活动，山前的冲洪积平原和河流低级阶地均发生了不同程度的拱曲变形，断层剖面揭示了该断层晚更新世末期有3次古地震事件。断层近地表后倾角变缓，地表的陡坎地形主要是由地层的拱曲变形形成的，反映了断层近地表位错的消减和分配规律。     

郯庐断裂带赤山段中晚更新世之交的史前地震遗迹

Chishan is located in Sixian County of Anhui Province, and the west branch fault of Tancheng-Lujiang fault zone passes through here. According to previous research, the Chishan segment of Tancheng-Lujiang fault zone has been obviously active since the Quaternary. Trenches excavated perpendicular to the Chishan segment for this study have revealed many prehistoric earthquake ruins-the multi-phase reverse faulting colluvial wedge, which is represented as the western brick-red sandstone of the late Cretaceous or maize gravel stratum of the mid Pleistocene of the hanging wall of the fault overlapping eastward the mid-late Pleistocene brown clay. In the base of the wedges, steep NW-dipping faults were found, and the steep fault planes turned upward to gently dipping collapse planes. As revealed by the trenches, the connection line of the breaking points strikes NNE in general. Heaving landforms are preserved at most parts of the tailing edge of the hanging wall where the fault passes through, and some EW-trending gullies were offset by right-lateral faulting. The two walls of several trenches have consistently shown that the collapse of traces have been pushed by a west-to-east force. Among them, Tc1~Tc4 show that the brick red limestone(K2)overthrust and collapsed on the yellow-brown clay containing ferro-manganese nodules (Q2-3P); Tc5 reveals that the yellowish-white gravel (Q2P) and the sandstone (K2) and overthrust and collapsed on the aforementioned clay. Reverse faulting colluvial wedges are found on both walls of each of the 8 trenches, but the number of wedges revealed in different trenches is different: there is 1 wedge, and 2 wedges in Tc1 and Tc3. 3 wedges in Tc2, Tc4 and Tc5, and in individual trenches, few wedges are revealed. This may be related to the trench’s location, depth and height of the remaining denudation. From the analysis of the trenches and the thermoluminescence dating results, we can preliminarily conclude that multiple large-scale reverse faulting stick events have taken place on the Chishan segment of the Tancheng-Lujiang fault zone during the mid-late Pleistocene, that is to say, many pre-historic strong earthquakes have occurred.     

Late Quaternary Activity and Paleoearthquakes along the Nanyukou Segment of the Northern Piedmont Fault of Wutai Mountain

The northern piedmont fault of Wutai Mountain is located at the north of the Shanxi Graben system,which is the dominating fault of the south boundary of the Fanshi-Daixian depression. This paper discusses the fault activity and paleoearthquakes around the Nanyukou segment of the northern piedmont fault of Wutai Mountain during the late Quaternary through field investigation along the fault,measuring geomorphic deformation and excavating trenches at some important sites. From Nanyukou to the southwest of Shanhui,we find obviously dislocated alluvial fans,with strong neotectonic movement at these sites. Since nearly 20ka,the vertical average slip rate is 1. 55mm /a to 2. 0mm /a. However,since nearly 6ka,it has reached as high as 2. 3mm /a,which is twice that on other segments. 2 trenches were excavated around Nanyukou with 6 events discovered. The referenced ages of the events are before 7600a,6700a ～ 7600a,5321a ～ 5575a,4400a ～ 5400a,4200a ～ 4400a and after 1600a B. P. with approximate recurrence interval 1400a. The latest event is likely to be the earthquake occurring at 512 A. D. ,so it is necessary to do further work to verify this in the future.