【作者】 李恩泽；

【导师】 刘财；

【作者基本信息】 吉林大学 ， 固体地球物理学， 2012， 博士

【摘要】 伊通—舒兰断裂带是著名的郯庐地震带的一个分支，在长春市南部通过。该断裂带主要由东、西两条断层构成，规模巨大，地貌和地球物理特征明显，并严格控制第四系沉积。上世纪以来，该断裂带周边先后发生3次5级以上—6级以下地震，因此被认为是现代活动断裂。伊通—舒兰断裂带（长春段）的地震强度究竟能达到几级、潜在危险区究竟位于何处，对长春市的影响究竟有多大，这些问题始终受到社会各界的高度关注。同时，随着长春市的城市化进程，人口数量急剧增加，城区范围不断扩大，固定资产投资持续增长，使得地震安全问题日益突出。因此，开展伊通—舒兰断裂带（长春段）的地震活动性研究具有十分重要的意义。当前地震科学是世界性的难题，研究和探索地震活动规律存在很多困难。地震通常发生在地表以下数千米至数十千米深度，以人类当前的能力尚无法直观了解这一深度的地质结构和动力环境，因此借助于地球物理方法是唯一途径。地震是地质构造对构造应力场作用的一种响应，因此探索地震活动规律应以构造应力场研究和地质构造研究为主要内容。构造应力场研究属于地质力学的一个分支学科，超出了本文的专业范畴，因此本文依据前人的研究成果对东北地区的构造应力场进行简要分析。本文的核心内容是以长春市南部为研究区，对该区域的地球物理学资料进行处理和解释，并结合地质资料研究伊通—舒兰断裂带的形态、分布和活动特征。在此基础上，对伊通—舒兰断裂带在现代构造应力场背景下可能发生的强烈地震的震级上限和发震区域进行了初步判断，最后讨论强烈地震对长春市的影响，并提出灾害防御的思路和建议。NE向的伊通—舒兰断裂带贯穿研究区南部的华北板块北缘褶皱带和北部的松嫩微板块两大构造单元。两单元于古生代末—中生代初拼接于研究区中部的西拉木伦河—长春—延吉一线。因此伊通—舒兰断裂带南段的基底与华北板块太古代深变质结晶基底有关，而北段的基底则属于松嫩微板块早古生代浅变质结晶基底。该断裂带的长春段则可能是上述两种基底互相叠合的部位，具有复合基底的特征。统一大陆形成后，研究区经历了古太平洋、太平洋两期构造演化阶段，地质构造格局发生了很大变化，形成了由松辽盆地、大黑山条垒、伊通地堑和那丹哈达地体等构成的NE向和NNE向展布的盆—岭相间的格局。研究区地质和地球物理资料显示，大黑山条垒和伊通地堑的基底曾是那丹哈达地体的一部分，大黑山条垒的西北部边界延伸到松辽盆地内部并与四平—长春断裂带的位置基本吻合。大黑山条垒的隆升使松辽盆地东部边缘的中生代沉积地层发生掀斜，而该区域的NW向断层也显示了右旋平移的活动特征。综合上述证据，认为白垩纪末—古近纪初，松辽盆地发生强烈的地壳伸展运动，盆地东部大面积抬升，大黑山条垒隆升成岭。与此同时，NW向断层右行平移，导致大黑山条垒与那丹哈达地体进一步分离并使伊通地堑基底下沉，开始接受巨厚沉积，这一过程类似于转换断层的活动方式。地质证据显示，大黑山条垒、伊通地堑基底与那丹哈达地体的分离是沿着NW方位发生的，而沿着伊通—舒兰断裂带的延伸方位（NE向），三者并未发生相对位移，表明伊通—舒兰断裂带不具有明显的走滑性质。这一结论对伊通—舒兰断裂带（长春段）震级上限的判断构成制约。对研究区1:20万重磁资料进行了向上延拓、磁性化极、垂直方向导数和水平方向导数等常规处理，同时进行了欧拉反褶积、构造增强滤波和重磁对比分析等非常规处理。在此基础上，对研究区断裂构造的方位、分布、活动性等特征进行了解释和分析。结果表明，研究区存在形成时期不同、走向不同的各种断裂，其中NE向、EW向断裂规模较大，控制侵入岩的分布；NS向和NW向断裂则具有次生或伴生性质，规模较小，地球物理特征不明显。伊通地堑是新生代构造，沉积了以古近纪地层为主的巨厚新生代碎屑物，最大厚度可达6000m。伊通地堑是研究区NW向、NE向断层和基底活动共同作用的产物。沉积地层完整记录了研究区新生代以来各期地质运动的历史。研究区伊通地堑的人工地震剖面资料显示，地堑的沉积层内主要发育有NE向和EW向断层。两种不同走向的断层分布具有明显的空间分异性，即NE向断层分布于地堑内靠近东南缘断裂的一侧，且集中分布在莫里青断陷和孤店斜坡带两个构造单元内；EW向断层则集中分布于鹿乡断陷的2号断层两侧及其以北的岔路河断陷内。这种特征反映了基底和断裂活动的差异性以及构造应力场的局部特征，对伊通—舒兰断裂带构造活动性分段构成制约。地震解释剖面同时显示，伊通地堑的基底形态、断层分布、沉积样式以及断层活动性具有明显的分段特征。莫里青断陷、岔路河断陷的波—太凹陷具有先期稳定，后期活动的特点，表现为沉积层厚度大，产状舒缓；鹿乡断陷的基底和上覆盖层均遭受过强烈的褶皱反转，2号断层曾剧烈活动并控制两侧沉积地层近2000m的垂直落差。上述特征对伊通—舒兰断裂带的构造活动性分段形成制约。东北地区地质活动自新生代以来受太平洋板块向西正向俯冲作用的影响和调制。白垩纪末—古近纪初全球范围内板块构造格局发生重大调整，松辽盆地发生强烈构造伸展，大黑山条垒隆升，对伊通地堑开始形成；古近纪末—新近纪初全球范围内又发生一次板块构造格局的重大调整，伊通地堑处于挤压环境并发生构造反转，地堑的强烈沉积史结束。东北地区新近纪以来的新构造运动以断块的垂直升降运动为特征，表现在松辽分水岭的形成以及对松辽盆地水系流向的改变。除此之外，莫里青断陷以及舒兰地堑的火山非常发育，表明这两处单元构造活动的特殊性。东北地区现代构造应力场主要受太平洋板块俯冲作用产生的水平挤压力的影响，但东北地区的主压应力方向与太平洋板块的俯冲挤压方向存在30°左右的偏离，表明本区域同时存在一个近NS向挤压作用的叠加。按照近年来全球大地构造单元新的划分方案，这一挤压力可能来自于欧亚板块对“阿穆尔”微板块北缘的挤压。在两种应力场的联合作用下，东北地区的构造应力场存在发生急剧转折的可能性，并有可能导致地震活动强度和频度的较大变化。近年来伊通—依兰断裂带北部舒兰、通河一带发现全新世以来发生7级以上强烈地震地质证据，表明伊通—舒兰断裂带乃至整个东北地区的地震活动强度需要重新认识。据此认为伊通—舒兰断裂带存在发生7级以上强烈地震的地质条件，但现代构造应力场不利于7级以上地震的孕育，积累足以产生强烈地震的能量可能经历很漫长的周期。现代构造应力场方向有利于伊通—舒兰断裂带的走滑平移运动，但是伊通—舒兰断裂带的走滑平移属性非常有限，根据这两点制约条件，推测伊通—舒兰断裂带发生的剪切型地震不会具有太大能量，震级上限为6级。据地球物理、地质资料所提供的制约条件，确定伊通—舒兰断裂带的地震危险区位于西支断裂的乐山至奢岭一线。上世纪以来全球地震灾害呈日益加剧的趋势，其原因在于人口的急剧膨胀和人口密度的极度不平衡，人口密集的城市面临日趋严峻的地震安全问题。我国是世界上地震灾害最为深重的国家，地震死亡人数占全球的三分之一。其原因不在于我国强烈地震多，而在于基础设施抗震能力差，最根本的原因在于灾害防范意识薄弱。随着城市化进程的加快，长春市的地震安全问题也日益突出。通过初步评估认为，伊通—舒兰断裂带如果发生6.0级左右地震，长春将会遭受一定的人员伤亡和经济损失。对于灾害防御的认识和思维方式决定防灾决策。长春市的地震灾害防御，要结合本地区地质条件和地震活动水平以及经济条件等综合因素，合理搭配社会资源和自然资源，依靠科技、依靠法制、依靠全社会力量，科学地、有针对性地采取地震灾害防御措施。更多还原

【Abstract】 The Yitong-Shulan fault zone is a branch of the well-known Tanlu seismic zone crossing south ofChangchun city. The fault zone is mainly composed of two faults in the east and west, it islarge-scale, shows obvious geomorphological and geophysical characteristics, and strictlycontrols the Quaternary deposition. Since the last century, there happened three timesearthquakes between5-6level around the fault zone, which is considered to be a modern activefault.For the Yitong-Shulan fault zone (Changchun segment), what level the earthquake intensitywill reach, where the potential danger zone is exactly located, and how much impact onChangchun City are the issues that has always been the greatly concerned by the community.Meanwhile, along with the urbanization process in Changchun city, the population is quicklyincreasing, city boundary continues to expand, and fixed investments is continuing to grow, thusmakes seismic safety issues increasingly prominent. Therefore, it is significance to study seismicactivity of the Yitong-Shulan fault zone (Changchun segment).Now earthquake science is a worldwide problem, it is difficult to study and explore seismicactivity pattern. Earthquake usually occurs at the depth of a few kilometers to tens of kilometersbelow the surface, by the current limited capacity, human cannot intuitively understand thegeological structure and dynamic environment at this depth, therefore, geophysical methods isthe only way to solve.The earthquake is a response of the geological structure to the tectonic stress field, soexploring the laws of seismic activity should be based on the tectonic stress field and geologicalstructure. The study of tectonic stress field studies is a branch of Geomechanics, which is beyondthe current research scope, so this dissertation will analyze tectonic stress field of the Northeastbased on previous research results. The core content of this research will aim at the south ofChangchun City as the study area, process and interpret the geophysical data processing in thisarea, and study the morphology, distribution and activity characteristics of the Yitong-Shulanfault zone combined with the geological data. The paper also gives a preliminary judgment aboutthe upper limit of strong earthquake magnitude and seismogenic zone produced by theYitong-Shulan fault in the tectonic stress field. Finally I discuss the impact of the strongearthquake on Changchun City and propose some ideas and suggestions of disaster defense.The Yitong-Shulan fault zone with NE trend runs through the northern-margin fold belt ofthe North China plate in south of the study area and Songnen micro-plate in north of the studyarea. Two units located middle of the study area connect at Xar Moron River-Changchun-Yanjiline in the late Paleozoic-early Mesozoic. Therefore, the basement of southern Yitong-Shulanfault zone is related with deep Archean metamorphic crystalline basement of the North Chinaplate, while the northern basement belongs to early Paleozoic metamorphic crystalline basementof the Songnen microplate. Changchun section of the fault zone may be superimposed of these two kinds of basal parts, which has the characteristics of the composite substrate. After thereunification of the mainland, the study area has experienced two-stages evolution about theancient Pacific Ocean and the Pacific tectonic, the geological structure pattern has changedgreatly, it forms the basin-Ridge pattern with NE and NNE trend composed of the Songliao basin,Daheishan Horst, Yitong graben and Dan Hada terrane.The study of geological and geophysical data show that the basement of Daheishan Horstand Yitong Graben was part of the body Dan Hada terrane, the northwestern boundary of theDaheishan Horst extends to inside of the Songliao Basin and coincide with Siping-Changchunfault zone. The uplift of Daheishan Horst makes the eastern edge of the Mesozoic sedimentarystrata of the Songliao Basin tilted, while NW-trend faults in the region shows the activitiescharacteristics of dextral translation. The evidences show that in the late Cretaceous-earlyPaleogene, the Songliao Basin occurred strong crustal stretching, a large area of the eastern partof the basin uplifts, Daheishan Horst uplifts to be a ridge. At the same time, the NW-trend faultsrun right translation, which leads to the separation of Daheishan Horst from Dan Hada terraneand sinking of Yitong graben basement, it becomes the thick deposition, this process is similar tothe way of transform faults activities.Geological evidences show that the the separation of Daheishan Horst, the Yitong grabenbasement, and the Dan Hada graben is along the NW direction. Three parts did not occur relativedisplacement at the extension direction of the Yitong-Shulan fault zone (NE), it shows that theYitong-Shulan fault zone does not have the nature of the apparent slip. This conclusion limits thejudgment of the upper limit about earthquake magnitude of the Yitong-Shulan fault zone(Changchun segment).I studied1:200000gravity and magnetic data in the study area and processed the data byusing the upward continuation, magnetic to the pole, the derivative of vertical direction, and thederivative of horizontal direction. At the same time, the Euler deconvolution, structural-enhancedfiltering, and comparison and analysis of gravity and magnetic are used. Based on theseprocessing, the orientation, distribution, activity and other characteristics of the fault structure inthe study area are interpreted and analyzed. The results show that the study area exist a variety ofdifferent fault formed in different periods, the NE-and EW-trend faults has large scale, whichcontrol the distribution of intrusive rocks; the NS and NW-trend faults have secondary orassociated characteristics, which have small scale, geophysical characteristics are not obvious.Yitong graben is Cenozoic structure, which deposit thick Cenozoic clastic materialbelonging to Paleogene strata, it can reach the maximum thickness of up to6000m. YitongGraben is the joint product of NW-trend, NE-trend faults and the basement activities.Sedimentary strata completely record the history of geological movement since Cenozoic in thestudy area. Artificial seismic profile data of Yitong graben in the study area show that grabensediments mainly have NE-and EW-trend faults. Two different trend fault distribution hasobvious spatial opposite characteristics, that is, NE-trend faults locate near the southeasternmargin of the fractured inside the graben, and they are located in the two tectonic units ofMoliqing rift and Gudian slope, while EW-trend faults are located at both sides of LuXiangfaults and inside the north Chaluhe fault depression. This feature reflects the difference of basal, fault activities, and local features of the tectonic stress field, it piecewise limits tectonic activitiesof the Yitong-Shulan fault.The seismic interpreted sections show that the basement pattern, fault distribution,depositional style and faults activities of Yitong graben display segment features. Moliqing faultdepression and Bo-Tai depression of Chaluhe fault depression has initial stability and postactivities, it shows the thick deposition, soothing occurrence. The basement and cover ofLuXiang fault depression have suffered strongly fold reverse, No.2fault has vigorous activityand control vertical drop near2000m at both sides of the sedimentary strata. Thesecharacteristics limit tectonic activity of the Yitong-Shulan fault zone.Geological activities in Northeast of China is affected and controlled by the positivesubduction of the Pacific Plate from west direction since the Cenozoic. Worldwide pattern ofplate tectonics changes a lot in the late Cretaceous-early Paleogene, Songliao Basin appearsstrong tectonic stretching, Daheishan Horst uplifted, Yitong graben appeared its shape. Secondadjustment of worldwide pattern of plate tectonics happened in the end of the Paleogene-earlyNeogene, Yitong graben was located in squeeze the environment and suffered tectonic inversion,strong deposition of graben ended its history.Neotectonic movement in Northeast of China since Neogene is characterized by verticalmovement of the fault block, it shows the formation of Songliao watershed and changes in theSongliao Basin river flows. In addition, volcanic of Moliqing fault depression and Shulan grabenis well developed, thus indicates the particularity of these two units of tectonic activities.Modern tectonic stress field in Northeast of China is mainly affected by the horizontalsqueeze by the Pacific plate subduction, but the direction of principal compressive stress in theNortheast of China deviate the direction of subduction extrusion of Pacific plate about30degree,which shows that the region has additional near NS-trend compression. According to the newclassification scheme for global tectonic units in recent years, the extrusion pressure may comefrom extrusion of the Eurasian plate acting on the northern margin of the "Amur" micro-plate.Under the combined effects of two stress field, tectonic stress field in the Northeast regionexist the possibility of a dramatic turning point, and may lead to significant changes of theintensity and frequency of seismic activity. In recent years, Shulan and Tonghe area in northernof the Yitong-Yilang fault zone shows geological evidence of a strong earthquake more thanseven level since the Holocene. The evidence shows people need to re-recognize seismicactivities of Yitong-Shulan fault zone and the entire northeast region. Accordingly, I think thatthe Yitong-Shulan fault zone exist geological conditions, which can occur strong earthquakemore than seven levels, but the modern tectonic stress field does not suit for the breeding ofearthquakes more than seven levels. Accumulating enough energy to produce a strongearthquake may need a very long cycle. The direction of tectonic stress field is good forstrike-slip translational motion in Yitong-Shulan fault zone, but strike-slip translation property ofthe Yitong-Shulan fault zone is very limited. According to these two constraints, I suggest theresults that shear earthquake from the Yitong-Shulan fracture zone will not have too much energy,the magnitude of earthquake has a maximum of six levels. From the constraints provided bygeophysical and geological data, one can determine that the earthquake risk zone of the Yitong-Shulan fault is located at Leshan to extravagance Ridge line in the Xizhi fault depression.Since last century, global earthquake disaster shows a trend of increasing, the reason lies inthe population explosion and the extreme imbalance of the population density, densely populatedcities are facing increasingly serious earthquake safety issues. China is deeply influenced byearthquake disaster in the world, the earthquake death accounts to one third of that of the world.The reason is not that our country always appears strong earthquakes, but that we have badearthquake-resistant structure, the most fundamental reason is the weak awareness of disasterprevention. With the acceleration process of urbanization, the seismic safety issues ofChangchun city increasingly become prominent Preliminary assessment shows that Changchunwill suffer some casualties and economic losses if the Yitong-Shulan fault zone occur earthquakeabout6.0.Disaster prevention strategies depend on awareness and ways of thinking. Earthquakedisaster prevention in Changchun City need to combine with integrated factors includinggeological conditions, the level of seismic activity, and economic conditions etc. The city need touse reasonable social and natural resources, depend on science and technology, rely on the ruleof law, rely on the strength of the whole society, and scientifically provide disaster preventionmeasures.更多还原