【作者】 徐岳仁；

【导师】 邓起东； 何宏林；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2013， 博士

【摘要】 霍山山前断裂带是山西断陷盆地带中部重要的边界活动断裂带之一，是我国依据历史文献记载确定的第一个8级大地震（1303年洪洞M=8大地震）的发震断层。围绕该断裂带的晚第四纪活动，包括断裂带的几何展布特征、构造地貌、活动方式、古地震等的深入研究，不仅对系统认识山西断陷盆地带晚第四纪活动历史具有重要理论意义，还对山西省的防震减灾工作具有重要的应用价值。本论文利用野外地震地质调查、遥感综合解译和多探槽古地震分析等研究方法以及AMS14C测年、DGPS测量、GIS的空间分析等技术手段，对山西霍山山前断裂带的晚第四纪活动特征进行研究：（1）揭示霍山山前断裂带作为霍山山脉的主控边界断层在新生代以来的强烈活动，其南段（霍州-洪洞一带）和北段（介休-灵石一带）在新生代以来具有一致的构造活动特征；（2）5个探槽的古地震事件分析和35个AMS14C年代结果，确认断裂带南段在晚更新世晚期以来的4次古地震事件，其中，最新一次事件对应1303年洪洞大地震，全新世中晚期以来的3次事件具有约2000年的复发间隔；（3）沿断裂带连续展布的不同层次的断层三角面、跨断裂带的河流地貌定量参数揭示了霍山山前断裂带的晚第四纪以来的强烈倾向活动特征，野外调查获取的断层产状、断层面擦痕产状及构造微地貌均显示该断裂带的活动方式以倾向滑动为主；（4）结合研究区所在的黄土高原的区域气候环境特点，分析了跨断层水系沿断裂带发生水平变位的可能成因；（5）初步讨论了霍山山前断裂带的动力学模式。本论文主要取得以下四个方面的研究结果：（1）霍山山前断裂带的几何结构特征利用高分辨率的IRS-P5和CBERS-02B卫星影像和航空照片立体像对数据，对霍山山前断裂带进行了综合遥感解译，并开展了详细的野外调查验证。该断裂带由南向北自洪洞县苏堡镇开始，经广胜寺、兴旺峪、石门峪、柏亭、兴唐寺等地，延霍州市的沙窝、观堆、李曹、三教乡、梨湾等地的山前通过，穿过仁义河后，沿霍山山脉与灵石凸起之间的断层槽谷继续往北近SN向延伸，在霍口一带逐渐转为NE向沿静升盆地东边界展布，穿过龙凤河，消失在介休市的洪山山前黄土台地一带，断裂带总长度116km，整体走向NE、NNE，倾向NW，局部产状有变化。根据断裂带的几何结构特点，将霍山山前断裂带划分为南、北2个段落，各段内又可细分为3个次级段落，分别是南段的A次级段（苏堡至广胜寺段）、B次级段（广胜寺至观堆段）、C次级段（观堆至杨家庄段）和北段的D次级段（梨湾至南车腰段）、E次级段（南车腰至霍口段）和F次级段（霍口至龙凤段），其中B、D、E次级段断层走向以NNE为主，C、F次级段走向以NE为主，A次级段受霍山主山脉高度的自北向南迅速降低和洪洞凹陷的深断陷影响，地表断层迹线并不清晰，以大量的地震形变遗迹为特征；B次级段的线性特征最为显著、也是断层构造地貌现象最为集中的段落，成为本论文探槽开挖的集中段落。（2）霍山山前断裂带的构造地貌特征①霍山山脉主山脊NNE向展布，南北两端分别止于洪洞的苏堡镇和介休龙凤镇，霍山山前断裂带发育于霍山山脉西麓，是山前松散沉积物与基岩间的分界断层，地形上该断裂带位于山前地形坡度陡变部位。②霍山山前断裂带下盘基岩山体自南向北共识别出17个一级断层三角面，和近100个次级三角面，形成时代较新的断层三角面发育在一级断层三角面中；形成时代相近的三角面形态特征也相似，其顶点高程和底边高程相近；断层三角面的形态特点显示霍山断裂带上新世以来强烈的构造抬升过程；与断层三角面相对应的断层上盘上，近断层处分布有以风成黄土为主的山前丘陵地貌，地表侵蚀活动受断层三角面流域规模限制，其水动力条件较弱，河流发育规模较小。多层次断层三角面的形态特点反映了霍山山前断裂带在新生代以来的强烈倾向活动特点。③通过跨越断裂带400余条不同规模水系的平面形态特征分析，发现南段和北段一样，在断层位置，无论是源头位于霍山主山脊的主河流还是源头在断层三角面上的次级河流均未形成系统性的的水平偏转，尽管有的河流在断层破碎带上发育横向槽谷，部分次级河流受水动力条件和山前黄土丘陵沉积的影响，表现出似左旋或似右旋的偏转，但是根据跨断层水系的偏转统计，发生右旋或左旋水平偏转的河流数量总体上不具有统计优势，不能将其作为判断断裂带发生水平走滑运动的证据。④利用30m分辨率的ASTER GDEM数据，提取了霍山地区的48条河流纵剖面，并计算它们的定量地貌参数，包括Hack剖面、河长坡降指标SL、均一化河长坡降指标SL/K和面积高程积分值HI及积分曲线。结果显示29条横跨霍山山前断裂的河流的纵剖面在断层两侧的形态显示出明显的差异，表现出明显的受断层活动控制的特征，其它没有被霍山山前断裂断错的河流，除极少部分在上游河段存在局部陡变外，纵剖面形态表现为近似下凹的指数曲线形态，显示其处于近均衡状态；48条河流的HI值及积分曲线显示了霍山地区新生代以来处于强抬升弱侵蚀状态，即所有河流均处于幼年期或壮年期。⑤48条河流的Hack剖面呈现一致的上凸形态，但上凸形态存在明显差异：未跨越霍山山前断裂的河流Hack剖面形态呈现光滑的近圆弧状；而跨越霍山山前断层的大部分河流的Hack剖面表现为一段较平缓下降后的突然陡降。一致的上凸表明了霍山地区处于构造抬升状态，且抬升速率较快；而Hack剖面的形态差异，反映了研究区内不同区域间构造活动的显著差异，跨断层河流Hack剖面上出现形态陡降特征印证了霍山山前活动断裂带作为这一区域的主干断裂在新生代以来的强烈构造活动，圆弧状的Hack剖面反映其它河流基本没有受到断裂活动的干扰。（3）霍山山前断裂带的古地震事件及1303年洪洞地震的地表破裂带霍山断裂带南段5个探槽（Tc01-Tc05）揭露的古地震事件分析表明：①研究区的地层以基岩山地和更新世以来的黄土堆积及坡麓堆积为主。区域地层对比发现，临汾盆地与太原盆地的边缘地带以黄土堆积及坡麓堆积为主，晚更新世晚期至全新世以来发育有古土壤层，特别是全新世大暖期的气候适宜期。古土壤层无论在黄土台地还是盆地沉积中都存在，具有区域性沉积特点，全新世古土壤层是探槽揭露地层中的标志地层之一。②晚更新世晚期以来至少发生4次地震事件，事件以倾向滑动为主。其中晚更新世晚期事件发生在距今12520~26380a之间，全新世中晚期以来的三次事件，分别发生在距今2650~3465a、5370~5808a和709a（1303年洪洞8级历史地震）。全新世中晚期以来的三次强震重复间隔时间约2000a。③根据构造楔规模和倾向滑动量的对比分析，全新世中晚期以来的三次古地震事件具有相近的破裂强度。④霍山山前活动断裂带以倾向滑动为主，1303年洪洞8级地震的地震形变遗迹集中发生在断裂带的南段，以砂土液化、地震滑坡、崩塌及张裂缝为主，根据野外确认的大量断层剖面及其活动时代，估计历史地震的地表破裂带的长度116m，其规模与根据历史文献得到的等震线的X度的长轴接近一致，断裂带南段的5个探槽剖面也均揭示了这次地震。沿断裂带分布的地震陡坎是断层多次活动形成的累积位移量，集中在6~10m，依据探槽剖面标志古土壤层位错量，平均单次事件的垂直位错量为2.0m，1303年洪洞地震的离逝时间距2012年已709年，形成的地表形变遗迹被人类活动和侵蚀过程破坏殆尽，野外难以与更早之前的古地震事件形成的变形区分，因此，探槽地震事件分析成为本论文恢复断裂带强震活动历史的主要手段。（4）霍山山前断裂带的活动方式、滑动速率及动力学特征①霍山山前断裂带全新世以来的活动方式以倾滑为主，兼有一定量的水平滑动分量。24组最新断层擦痕的侧伏角，集中在75°-85°之间，由此计算出倾滑分量是水平分量的3-10倍，与前人认为的以右旋走滑为主的不同，过去的研究是通过分析有限的跨断层水系（冲沟）的水平右偏转，得出以右旋走滑运动为主的认识的。实际上，跨越断裂带400余条不同规模水系的统计分析显示，发生右旋或左旋水平偏转的河流实际上不具有统计优势。②根据探槽揭示的标志古土壤层的垂直位错量，以及该古土壤层的年代数据，计算断裂带南段全新世中晚期的垂直滑动速率为0.76~1.49mm/a。③霍山山前断裂带的活动特征与区域活动构造图像具有较好的一致性。鄂尔多斯周缘断裂系的形成和发展与下地壳以下软流圈物质的上涌关系密切，软流圈上涌是各断陷盆地发展及边界断裂的活动的主要动力来源，被多种地球物理资料所证实。地震学和地球物理资料也证实临汾盆地及周边确实存在着上地幔物质上涌的现象，是造成霍山山前断裂带运动发展的主要动力。更多还原

【Abstract】 The Huoshan piedmont fault zone, lying on the west slope of the Mts.Huoshan, is animportant boundary active fault in the middle of the Shanxi faulted basin belt (also named theShanxi graben system or Shanxi rift system). It is the seismogenic fault of the1303HongdongMs8.0earthquake, the first event of M≥8.0in historical documents in China. The quantitativestudy of its geometry, tectonic geomorphology, faulting features, and paleo-earthquakes, is veryimportant to understanding the active history of the Shanxi faulted basin belt in the lateQuaternary as well as the earthquake disaster mitigation efforts in Shanxi Province.This thesis focuses on applications of field investigations, comprehensive remote sensinginterpretation, the paleo-earthquake method, AMS14C dating and DGPS survey, GIS technologyto research on the Huoshan piedomont fault zone in the late Quaternary. The purposes are:1) toreveal the intense normal faulting in the Cenozoic as the northeastern margin of the Linfen basin,of which the southern section located in Hongdong county and Huozhou city and northernsection located in Lingshi County and Jiexiu city have consistent active features, and2) showthat the fault is mainly characterized by at least four paleo-earthquake events during latePleistocene, of which, the latest event corresponding to the1303Ms8.0Hongdong earthquakebased on5combined trench analysis and35AMS14C dating ages providing constraints on thegiant-earthquake recurrence interval of about2000a,3) describe continuous distribution ofdifferent levels of fault triangles, quantitative river geomorphic parameters in the surroundingMts. Huoshan areas and fault plane occurrence and scratches collected during field work tosupport the intensive normal faulting of the fault with a dip-slip characteristics during lateQuaternary,4) analyze the main causes for horizontal displacements along and across faultdrainages combining the arid and semi-arid climate factors and loess hilly geomorphology, and5)discuss the dynamic model based on field data and previous studies. The major research resultsof this thesis are presented below.(1) Geometic characteristics of the Huoshan piedmont fault zoneThe Huoshan piedmont fault zone, a normal faulting from Pliocene as a Basin and Rangeboundary, located in the northeastern Linfen basin, can be recognized by significant terraindifferences between the mountains and basins. Based on comprehensive remote sensinginterpretation using high resolution satellite images such as IRS-P5and CBERS-02B data, aerial photographs and fieldwork investigations, this fault has a northeast trend, dipping northwest,extends for more than116km, along the west foot slope of the Mts. Huoshan. Starting from thesouth, it extends by Subu town, Guangshengsi temple, Xingwangyu village, Shimenyu Village,Baiting village in Hongdong county, continues along the Shawo village, Guandui village, Licaotown, Sanjiao town, and Liwan village in Huozhou City, through the Renyi river, along the westfoot slope of the mountain in the Lingshi county, and terminates at Longfeng town in Jiexiu city.According to the geometric distribution characteristics, the Huoshan piedmont fault zonecan be divided into2sections, the north section and the south section, each section can bedivided3segments further, that is A segment (Subu-Guangshengsi section), B segment(Guangshengsi-Guandui section), C segment (Guandui-Yangjiazhuang section) of south part, andD segment (Liwan-Nancheyao section), Esegment (Nancheyao-Huokou section), and F segment(Huokou-Longfeng section) of north part. In all of6segments, B, D, and E strike in NNE, C andF has strike in NE, A segment has sand liquefactions and giant landslides triggered by the1303history earthquake, but with little buried fault planes, B segment shows a significant linearfeature on images and aerial photos, with the characteristic of cutting all geomorphic units bothsides, and geomorphology such as fault scarps, trough valley, fault triangular ridges, which is theright place for trench work.(2) Tectonic geomorphology characteristics of the Huoshan piedmont fault zoneUsing aerial stereo image pair, DEM data, fieldwork investigations, spatial datingprocessing softwares, on the basis of previous research results, the tectonic geomorphologyfeatures along the fault zone such as terrain, geology, crossing-fault river system distribution,quantitative river geomorphic parameters, fault triangle shape and etc. have been studied andmany geomorphology maps were prepared in order to understand the interaction betweentectonic activity and geomorphology features.1. The main ridge of Mts. Huoshan strikes in north-northeast, its southern end is locatednear Subu town in Hongdong County, and north end located near Longfeng town in Jiexiu city.The Huoshan piedmont fault zone on the west slope of the mountain, constitutes the boundarybetween bedrock and unconsolidated sediments, and lies at the position of highly variablerange-front terrian gradients.2. This work identified a total17first level fault triangles and nearly100sub-fault trianglesfrom south to north. Each first level fault triangle is split by the main river basins. The differentscale fault triangles can be characterized as the newer and smaller ones nested in the older ones,those with similar forming eras have similar morphology and almost same vertex elevation andbase elevation, showing a regular distribution from south to north. The features of the trianglesalso show that intense tectonic uplift of the Mts. Huoshan and normal faulting of the fault sincePliocene. There are many loess hills nearby the fault, where surface erosion is limited by thescale of triangles, indicative of weak hydrodynamic conditions. It can provide an importantcandidate sites to combined trench excavating for paleo-earthquake identification.3. Analysis of planar forms of more than400crossing-fault rivers of different scales shows that that all river from south to north are not consistency offset (right-laterally or left-laterally)by the faulting. In other words, river channel features in the study area does not support theobvious horizontal movement of the fault. The main river channels with source near the Mts.Huoshan ridge are all not offset by lateral faulting movement. Some of them, the channelsections near fault traces run along the trough valleies. The flat distribution of the othersecondary rivers located at the different levels fault triangles is complicated by relative weakerhydrodynamic conditions, loess hill deposition, some of which can be seen as right-offset, someof them can also be seen like left-offset, and the rest has no lateral offsets. Its cause is the naturaldevelopment process of river basins of different scales, and can not serve as the evidence for thedextral movement of the Huoshan piedmont fault zone.4. This work selected48rivers around the Mts. Huoshan. These rivers are divided into fourgroups according to their tectonic settings: rivers north of, across and south of the Huoshanpiedmont fault zone on the west of the Mts. Huoshan, and rivers on the east slope of themountains. Based on the ASTER GDEM of30m resolution, this work calculated a series ofquantitative fluvial geomorphic parameters, such as the longitudinal profile style, streamlength-gradient index (SL index), standard stream length-gradient index (SL/K index), Hackprofile, hypsometric integral curves and its values (HI). There is a significant correlation betweenthese parameters and tectonic environment. To the rivers across the Huoshan piedmont fault zone,the longitudinal profiles of upstream and downstream, divided by the fault, show significantlydifferent features from each other, demonstrating obvious characteristics controlled by faultactivity. Along the rivers in other tectonic domains, the longitudinal profiles performance anapproximate exponential curve, indicative of a near-equilibrium. The HI values and Hypsometricintegral curves of all river basins indicate that all the rivers are in the prime of life or childhood,that is, Mts. Huoshan is in the state of strong uplift and weak erosion overall in Cenozoic era.5. Convex Hack profiles of all rivers also show that Mts. Huoshan is in the stage of intensetectonic uplift in the Cenozoic, while there exist significant differences among Hack profiles ofrivers in different tectonic domains reflecting different tectonic activities. The river segmentswith abnormally high SL/K values usually corresponded to the normal faulting, while randomappearance of high SL/K values on some rivers without fault-cut corresponds to the bedrock withlittle effect of weathering.(3) Paleo-earthquake events of the fault and surface rupture zone of the1303Hongdong M8.0earthquakeFrom analysis to trenches Tc01-Tc05in south section of B segment, this work obtains thefollowing knowledge:1. According to regional stratigraphic correlation, the strata formation in the edge of theLinfen basin and Taiyuan basin constituted by loess and talus accumulated since Pleistocene, anddeveloped paleosoil in loess strata, especially during the Holocene with suitable climate. Thelatest paleosoil layeres in the top loess deposit can be identified in the edge or center of thebasins, which reflect the regional deposit characteristics. 2. There are at least four paleo-earthquakes identified during late Pleistocene and Holocenetimes, every event is characterized by normal faulting of the main fault and/or accompanied bysecondary sub-faults activities on the hanging wall. In the four events, the oldestpaleo-earthquake occurred at12520~26380a B.P., the other three events occurred at5370-5808aB.P.,2650-3465a B.P., and709a B.P., respectively. The three events in late Holocene show theearthquake recurrence interval of about2000a.3. Among the three paleo-earthquake events occurred at late Holocene, i.e. E1:1303a, E2:2650-3465y B.P., and E3:5370-5808y B.P., the E2and E3events have the similar seismicintensity with the E1earthquake based on comparative analysis of the paleoseismic wedges anddip slip amounts.4. The Huoshan piedmont fault zone is dominated by dip slip, and its deformation traces bythe1303giant earthquake concentrated in the south section, such as earthquake landslides, sandliquefaction, collapses, and tension fissures etc. Based on the latest displacement and faultprofiles of the fault, the surface rupture zone of the1303Hongtong M8.0earthquake is116kmin length, approximating length of isoseimal long axis of X degree area. From the Subu inHongtong County in south section, end at the northern Longfeng town in Jiexiu city, the latestsurface rupture can be traced by latest wedge and14C dating ages in every trenches. The heightof the fault scarps is mostly between6-10m reflecting accumulated vertical displacements bymany earthquake events, with the average vertical displacement of about2m by every earthquake.The elapsed time of the history earthquake is709year to2012A.D. The surface rupture zoneproduced by the earthquake has been completely ruined by human activities and erosionprocesses, thus it is difficult to confirm and distinguish from the earlier events’ displacement. Sotrench paleoevent analysis was as the primary means to resume faulting history in this thesis.(4) Active faulting manner, slip rate and dynamic characteristics of the Huoshanpiedmont fault1. As previously mentioned, the Huoshan piedmont fault zone is dominated by dip-slip witha small amount of the horizontal component. Using24groups of data of fault scratches on freshfault planes from south to north, with the side rake angles concentrating in75°-85°, and thiswork calculated that the vertical component is3-10times than the horizontal component. Thisview is different from previous studies. In fact, statistical analysis to more than400streamsacross the fault indicates that most rivers with right-or left lateral.2. Based on vertical dislocation of key layers exposed on trench Tc01, Tc03and Tc04profiles and their forming ages by AMS14C dating, the vertical slip rate is0.76-1.49mm/a duringthe late Holocene.3. The Cenozoic faulting of the Huoshan piedomont fault zone is consistent with the patternof regional tectonic activity. The formation and development of the active zone systems aroundthe Ordos block are closely related to asthenospheric upwelling, which has been confirmed by alarge number geophysical data. Asthenospheric upwelling is a major dynamic source fordevelopment of all faulted basins and boundary fault activities. Previous geophysics also have confirmed the upwelling of deep materials beneath the Linfen basin and surrdounding, and theupwelling is also the main source of the normal faulting of the Huoshan piedmont fault zone.更多还原