渭南塬前断裂晚第四纪古地震研究

渭南塬前断裂是渭南市南侧一条重要的全新世活动断裂,也是1556年华县81/4级大地震的发震断裂之一。通过对渭南市南侧的蒋家村剖面的详细研究,揭示出了两次古地震事件,发生时间分别在41.58±1.72ka与14.43±0.59ka之间,0.73±0.03ka之后,黑垆土被错断0.3m,通过钻孔剖面获得T2阶地砾石层被断错了17.4m,利用T2阶地砾石层的最大年龄为60.36±3.16ka,可获得渭南塬前断裂晚第四纪以来平均滑动速率为0.29mm/a。     

华山山前断裂中段晚第四纪活动的地貌表现及响应

调查了华山山前断裂中段（石堤峪-杜峪）晚更新世以来,尤其是全新世以来的断层构造地貌,讨论了它们的成因、特点及对断裂活动的响应关系。断层构造地貌主要包括：断层三角面、断层陡坎、洪积阶地、埋藏型洪积扇以及冲沟裂点。对各大沟峪峪口的洪积阶地进行了大比例尺微地貌测量,并在部分沟峪两侧沿断层崖陡坎及冲沟沟床布置了测线。结合T1、T2级洪积阶地位错测量结果及其14C年龄计算得到,华山山前断裂中段6000a-2000aB.P.的垂直滑动速率为1.485mm/a;2000aB.P.以来的垂直滑动速率为3.73mm/a。最后结合野外调查与理论认识,建立了正断层作用下洪积阶地与埋藏型洪积扇的演化模式。本研究结果支持华山山前断裂是1556年华县814级地震发震构造的观点。     

DISTRIBUTION CHARACTERISTICS OF THE AD 1556 HUAXIAN EARTHQUAKE TRIGGERED DISASTERS AND ITS IMPLICATIONS

A complete understanding to the disasters triggered by giant earthquakes is not only crucial to effectively evaluating the reliability of existing earthquake magnitude, but also supporting the seismic hazard assessment. The great historical earthquake with estimated magnitude of M8.5 in Huaxian County on the 23^rd January 1556, which caused a death toll of more than 830 000, is the most serious earthquake on the global record. But for a long time, the knowledge about the hazards of this earthquake has been limited to areas along the causative Huashan piedmont fault(HSPF) and within the Weihe Basin. In this paper, we made a study on earthquake triggered landslides of the 1556 event along but not limited to the HSPF. Using the high-resolution satellite imagery of Google Earth for earthquake-triggered landslide interpretation, we obtained two dense loess landslides areas generated by the 1556 earthquake, which are located at the east end and west end of the HSPF. The number of the interpreted landslides is 1 515 in the west area(WA), which is near to the macro-epicentre, and 2 049 in the east area(EA), respectively. Based on the empirical relationship between the landslide volume and area, we get the estimated landslide volume of 2.85~6.40km³ of WA and EA, which is equivalent or bigger than the value of ~2.8km³ caused by Wenchuan earthquake of M_W7.9 on 12^th May 2008. These earthquake triggered landslides are the main cause for the death of inhabitants living in houses or loess house caves located outside of the basin, such as Weinan, Lintong, Lantian(affected by WA) and Lingbao(affected by EA). Our results can help deeply understand the distribution characteristics of coseismic disaster of the 1556 Huaxian earthquake to the south of Weihe Basin, and also provide important reference for the modification of the isoseismals.     

Paleoseismic indications along ‘aseismic’ fault segments in the guadalentín depression (SE Spain)

The Guadalentín Depression, located in SE Spain (Murcia Region), is bounded by two of the main NE-SW master faults of the Eastern Betics Cordilleras: The Lorca-Alhama and the Palomares left-lateral strike-slip faults. Available earthquake data indicate that, in the last 600 years, some sectors of the Lorca-Alhama Fault and the entire sector of the Palomares Fault have not been associated with significant historical seismicity. However, they show a wide range of diagnostic features of earthquake surface displacements on late Pleistocene and Holocene alluvial and colluvial surfaces. Aside from the left-lateral offsets recorded along 045–050 ° master fault strands of the Lorca-Alhama Fault, major paleoseismic surface displacements show different kinematics in relation to the broad orientation of the fault strands: (1) vertical normal displacements along 010–020 ° trending faults mainly preserved as degraded fault scarps of 2.5-1.8 m high (Aljibejo site); and (2) vertical reverse displacements, with average offsets of 0.2 – 1 m, along 065–080 ° subsidiary faults. In this last group, the younger one (Carraclaca Baths site) remains as a fault scarp of 0.8 m height affecting a cascade tufa which was active until the Spanish Roman Period (2nd Century B.C. to 6th Century A.D.). In other cases, reverse offsets resulted in smaller displacements (0.26 m) of paleosols, but show a recurrent behaviour (La Escarihuela site). The strongest earthquakes recorded in the study area did not exceed more than Mb 4.5 or MSK Intensity VIII (historical) with no evidence of coseismic rupture. Therefore, the preliminary data presented here seem to indicate that the paleoseismic activity on both faults is capable of producing coseismic surface displacements, probably reaching magnitudes of at least 6.5. These data show that paleoseismic studies based on geomorphological analyses are a useful tool in the assessment of the relative degree of activity of apparently ‘aseismic’ fault traces.     

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.     

GEOMETRIC DISTRIBUTION AND CHARACTERISTICS OF THE SURFACE RUPTURE OF TWO HISTORICAL EARTHQUAKES IN THE BARKOL BASIN,XINJIANG

Surface rupture zone of historical earthquake is the most intuitive geomorphological response to fault activity. The rupture pattern, coseismic displacement and its geometric spatial distribution are important for determining segmentation and long-term movement behaviors of active fault. In the Barkol Basin of Xinjiang, according to the comprehensive result from remote sensing image interpretation, field surgery, high-resolution small unmanned aerial vehicles photography, terrain deformation measurements and trench excavation on geomorphological points, not only the new surface ruptures of the two M7 1/2 historical earthquakes in Barkol in 1842 and 1914 were found and defined between Xiongkuer and the southwest of Barkol County in southwestern part of the basin, but also the latest deformation evidence of the EW fold-up faults in the eastern part of the Basin was identified. Combined with the ancient document analysis of the two historical earthquakes, we finally conclude that the surface rupture zone in the western segment on the southern margin of the Barkol Basin is the seismogenic structure of the M7 1/2 earthquake in 1842. The surface rupture zone is mainly characterized by left-lateral strike-slip, roughly with en echelon arrangement spreading from Xiongkuer to the south of Barkol County. The length of the surface rupture zone determined by field investigation is at least about 65km, and the maximum horizontal displacement appears around the Xiongkuer Village. At the same time, the surface rupture zone gradually shows more significant thrust extrusion from west to east, and has a tendency of extension towards the central of the Barkol Basin. The average observed displacement of the entire surface rupture obtained by counting the coseismic offsets of multiple faulted gullies is(4.1±1.0)m, with the coseismic characteristic displacement of ~4m. The epicenter position should appear at the place with the largest horizontal dislocation amount near Xiongkuer Village. In addition, the length of the fold-blind fault zone in the vicinity of the Kuisu Town and the eastward extension to the Yanchi Township of the Yiwu Basin, which was discovered in the center of the Barkol Basin, is about 90km. The folded blind fault causes significant fold deformation in the latest sedimentary strata such as floodplain, and in addition, as shown on many outcrop sections, the bending-moment faults associated with the coseismic fold deformation have ruptured the surface. Therefore, the location of the epicenter should be located at the maximum fold deformation, which is near the Kuisu Town. The new research results not only further improve the understanding of the epicenter location and seismogenic faults of the two historical earthquakes in the Barkol Basin, but also provide an important reference for analyzing regional seismic hazards.     

云南中甸-大具断裂马家村-大具段古地震初步研究

中甸-大具断裂马家村-大具段位于哈巴雪山北麓及玉龙雪山以北的大具盆地内,总体走向310°～320°,根据卫星影像解译和详细的野外地质地貌调查,认为中甸-大具断裂马家村-大具段自第四纪以来长期活动,横跨断裂的水系右旋位错量可分为8.5～12m、22m左右、47m左右、200～280m、500～510m和1000m左右6个等级。在大具盆地内发现了长约600m的地震地表破裂带,这是该断层段在全新世活动的直接地质证据,在破裂带南东端附近开挖的探槽揭示出自晚更新世以来断裂存在三期活动,可能对应3次地震事件,结合前人在该断裂段获得的地质剖面和断错地貌面测年结果,分析认为马家村-大具段自晚更新世以来至少发生了3次古地震事件,发生时间分别为4910～45 a BP、7000 a BP左右和32.93～19.96ka BP,利用垂直同震位移值估算了水平同震位移量,最终得出每次地震事件的震级为7.5级左右。     

日本横手盆地东缘陆羽逆断层系的同震地表破裂特征及其分段性

通过对陆羽逆断层系上１８９６年同震地表破裂特征、长期活动习性和断错地貌等的研究，给出了可识别的逆断层型段落边界的标志，它们是断层崖形态持久性变化的过渡地段、断层抬升盘山地分水岭高程明显变化的转折部位、剖面几何结构转换区和断层下降盘盆地内的隐伏横向基岩脊等；指出逆断层上公里量级的空缺和阶区不能有效地终止或延缓逆断层型同震地表破裂的横向扩展，因此，不能作为逆断层型段落的边界，最后对陆羽逆断层系的千屋段和横手段的地震危险性进行了简要评估     

1556年陕西华县大地震形变遗迹及华山山前断裂古地震研究

华山山前断裂带晚第四纪以来具有明显的新活动,沿断裂带及其两侧分布有最新断层崖,基岩裂缝、黄土裂缝、山体崩(滑)塌体等众多的地震形变和破坏遗迹,华山山前断裂带应是1556年华县8级地震的发震断层。 从本文提供的一个古地震剖面分析,华山山前断裂带全新世以来可能发生过四次大地震,其重复间隔约2000—2500年     

LATE QUATERNARY ACTIVITY OF THE CENTRAL SEGMENT OF THE DARI FAULT AND RESTUDY OF THE SURFACE RUPTURE ZONE OF THE 1947 M73/4 DARI EARTHQUAKE,QINGHAI PROVINCE

Bayan Hara Block is one of the most representative active blocks resulting from the lateral extrusion of Tibet Plateau since the Cenozoic. Its southern and northern boundary faults are characterized by typical strike-slip shear deformation. Its eastern boundary is blocked by the Yangze block and its horizontal movement is transformed into the vertical movement of the Longmen Shan tectonic belt, leading to the uplift of the Longmen Shan Mountains and forming a grand geomorphic barrier on the eastern margin of the Tibet Plateau. A series of large earthquakes occurred along the boundary faults of the Bayan Hara Block in the past twenty years, which have attracted attention of many scholars. At present, the related studies of active tectonics on Bayan Hara Block are mainly concentrated on the boundary faults, such as Yushu-Ganzi-Xianshuihe Fault, East Kunlun Fault and Longmen Shan Fault. However, there are also some large faults inside the block, which not only have late Quaternary activity, but also have tectonic conditions to produce strong earthquake. These faults divide the Bayan Hara Block into some secondary blocks, and may play important roles in the kinematics and dynamics mechanism of the Bayan Hara Block, or even the eastern margin of the Tibet Plateau. The Dari Fault is one of the left-lateral strike-slip faults in the Bayan Hara Block. The Dari Fault starts at the eastern pass of the Kunlun Mountains, extends eastward through the south of Yalazela, Yeniugou and Keshoutan, the fault strike turns to NNE direction at Angcanggou, then turns to NE direction again at Moba town, Qinghai Province, and the fault ends near Nanmuda town, Sichuan Province, with a total length of more than 500km. The fault has been considered to be a late Quaternary active fault and the 1947 M73/4 Dari earthquake was produced by its middle segment. But studies on the late Quaternary activity of the Dari Fault are still weak. The previous research mainly focused on the investigation of the surface rupture and damages of the 1947 M73/4 Dari earthquake. However, there were different opinions about the scale of the M73/4 earthquake surface rupture zone. Dai Hua-guang(1983)thought that the surface rupture of the earthquake was about 150km long, but Qinghai Earthquake Agency(1984)believed that the length of surface rupture zone was only 58km. Based on interpretation of high-resolution images and field investigations, in this paper, we studied the late Quaternary activity of the Dari Fault and the surface rupture zone of the 1947 Dari earthquake. Late Quaternary activity in the central segment of the Dari Fault is particularly significant. A series of linear tectonic landforms, such as fault trough valley, fault scarps, fault springs and gully offsets, etc. are developed along the Dari Fault. And the surface rupture zone of the 1947 Dari earthquake is still relatively well preserved. We conducted a follow-up field investigation for the surface rupture zone of the 1947 Dari earthquake and found that the surface rupture related to the Dari earthquake starts at Longgen village in Moba town, and ends near the northwest of the Yilonggounao in Jianshe town, with a length of about 70km. The surface rupture is primarily characterized by scarps, compressional ridges, pull-apart basins, landslides, cleavage, and the coseismic offset is about 2~4m determined by a series of offset gullies. The surface rupture zone extends to the northwest of Yilonggounao and becomes ambiguous. It is mainly characterized by a series of linear fault springs along the surface rupture zone. Therefore, we suggest that the surface rupture zone of the 1947 Dari earthquake ends at the northwest of Yilonggounao. In summary, the central segment of the Dari Fault can be characterized by strong late Quaternary activity, and the surface rupture zone of the 1947 Dari earthquake is about 70km long.     

INTERPRETATION AND ANALYSIS OF THE FINE FAULT GEO-METRY BASED ON HIGH-RESOLUTION DEM DATA DERIVED FROM UAV PHOTOGRAMMETRIC TECHNIQUE: A CASE STUDY OF TANGJIAPO SITE ON THE HAIYUAN FAULT

Fault-related tectonic geomorphologic features are integrated expressions of multiple strong seismological events and long-term surface processes, including crucial information about strong earthquake behavior of a fault. It's of great significance to identify the strong seismic activity information from faulted landscapes, which include the date and sequence of the seismic activities, displacements, active fault features, for studying the seismic rupture process, predicting the future seismic recurrence behavior and evaluating the seismic hazard of the fault. However, due to the restriction of measuring techniques and the subsequent poor quality of the acquired data, it has been difficult to accurately extract such information from complex tectonic landforms to study active faults for a long time. Recently, "small Unmanned Aerial Vehicle(sUAV)" photogrammetric technique based on "Structure from Motion(SfM)" provides a cost-efficient and convenient access to high-resolution and high-accuracy "digital elevation models(DEMs)" of tectonic landforms. This paper selects the Tangjiapo area at the Haiyuan Fault to conduct data collection, in which the structural and geomorphic features are well preserved. Using a small quadrotor unmanned aerial vehicle(Inpire 2), we collect 1598 aerial photographs with a coverage area of 0.72km². For calibrating the accuracy of the aerial data, we set 10 ground control points and use differential-GPS to obtain the spatial coordinates of these control points. We use model software Agisoft PhotoScan to process these digital pictures, obtaining high-resolution and high-accuracy DEM data with the geographic information, in which data resolution is 2.6cm/pix and the average density of point cloud is 89.3 point/m². The data with these accuracy and resolution can fully show the real geomorphic features of the landform and meet the requirements for extracting specific structural geomorphic information on the surface. Through the detailed interpretation of the tectonic landforms, we identify a series of structures associated with the strike-slip fault and divide the alluvial fan into four stages, named s₁, s₂, s₃, and s₄, respectively.Wherein, the s₁ is the latest phase of the alluvial fan, which is in the extension direction of the Haiyuan Fault and there isn't any surface fracture, indicating that the s₁ was formed after the M8.5 Haiyuan earthquake in 1920. The rupture zone on the s₂ fan is composed of varied kinds of faulting geomorphologic landforms, such as a series of en echelon tension-shear fractures trending 270°~285°, fault scarps and seismic ridges caused by the left-lateral motion of the seismic fault. In addition, a number of field ridges on the s₂ fan were faulted by the 1920 Haiyuan M8.5 earthquake, recording the co-seismic displacements of the latest earthquake event. Relatively speaking, the surface rupture structure of the s₃ fan is simple, mainly manifested as linear fault scarp with a trend of 270°~285°, which may indicate that multiple earthquakes have connected the different secondary fractures. And a small part of s₄ fan is distributed in the southwest of the study area without fault crossing. Furthermore, we measured the horizontal displacements of river channels and vertical offsets of fault scarps. The faulted ridge on the s₂ fan and faulted gully on the s₃ fan provide good linear markers for obtaining the fault left-lateral dislocation. We used the graphical dislocation measurement software LaDiCaoz developed based on Matlab to restore the gully position before the earthquake by comparing the gully morphology on both sides of the fault, and then determined the horizontal offset of s₂, which is(4.3±0.4)m and that of s₃ is(8.6±0.6)m. In addition, based on the DEM data, we extracted the fault scarp densely along the fault strike, and obtained the vertical offset of s₂, which is(4.3±0.4)m and that of s₃ is(1.79±0.16)m. Moreover, we detect slope breaks in the fault scarp morphology. For compound fault scarps generated by multiple surface rupture earthquakes, there are multiple inflection points on the slope of the topographic section, and each inflection point represents a surface rupture event. Therefore, the slope break point on the scarp becomes an important symbol of multiple rupture of the fault. The statistical result shows that the slope breaks number of s₂ is 1 and that of s₃ is 2. Based on the analysis of horizontal displacements of river channels and vertical offsets of fault scarps as well as its slope breaks, two surface rupturing events can be confirmed along the Tangjiapo area of the Haiyuan Fault. Among them, the horizontal and vertical displacements of the older event are(4.3±0.95)m and(0.85±0.22)m, respectively, while that of the latest event are(4.3±0.4)m and(0.95±0.14)m, which are the coseismic horizontal and vertical offsets of the 1920 Haiyuan earthquake. These recognitions have improved our cognitive level of the fine structure of seismic surface rupture and ability to recognize paleoearthquake events. Therefore, the high-resolution topographic data obtained from the SfM photogrammetry method can be used for interpretation of fine structure and quantitative analysis of microgeomorphology. With the development of research on tectonic geomorphology and active tectonics toward refinement and quantification, this method will be of higher use value and practical significance.     

5·12汶川地震地表破裂基本参数的再论证及其构造内涵分析

地震地表破裂基本参数是反演地震破裂过程的基本约束条件和预测其他活动断层地震危险性不可缺少的物理量.以野外地表破裂带重要观测点全站仪或差分GPS仪实测数据为基础,结合高分辨率遥感资料解译、先存断层陡坎构造地貌标志的识别、以及地形测绘资料的考证等,重新论证了5·12汶川地震地表破裂带展布样式、长度、最大同震位移值等基本参数.结果表明,地震地表破裂带长度可达240 km,最大垂直位移为6.5±0.5 m,最大右旋走滑位移4.9 m,基于倾角向下变缓逆断层模型推测汶川地震在龙门山推覆构造带中段产生了最大~7 m的地壳缩短量,说明青藏高原东缘横向逆断层为将高原内部东向水平运动转换为高原隆升的转换构造,这一研究结果有助于深化认识青藏高原东缘隆升机理.     

玛多—甘德断裂甘德段晚第四纪活动特征

玛多—甘德断裂是巴颜喀拉块体内部的一条活动断裂。 通过野外调查发现, 在玛多-甘德断裂的甘德段保留有一条较好的地震地表破裂带。 破裂带整体走向NW向, 长约为50 km。 野外获得的最大左旋水平位移7.6 m, 最大垂直位移4 m。 沿破裂带有大量地震活动的遗迹, 地表破裂类型十分丰富。 通过对各种地质地貌现象的调查与分析, 认为该破裂带形成时代较新。 断裂带在地貌上发育有线性排列的垭口、 断层三角面、 断层陡坎、 断层泉、 断错水系、 山脊扭错、 断塞塘、 鼓包等现象。 根据野外考察并结合现有资料分析, 该破裂带可能是该区域内历史上一次较为强烈地震的产物。 据此推断, 巴颜喀拉块体内部的玛多—甘德断裂晚第四纪以来可能有过强烈的活动并至今活跃。     

四川西昌1850年地震地表破裂特征研究

本文对则木河断裂带上各种地震地表破裂现象作了调查和时代方面的研究,结果表明,1850年西昌地震在西昌北的李金堡至宁南的松新间形成了长达90km的地震形变带。地震位错的最大水平位移为7m,垂直位移一般为0.5～2m,对地震形变带中的各种变形遗迹和地震地表破裂特征的研究表明,则木河断裂是这次地震的发震构造,震中位于大箐梁子一带,震中烈度达Ⅹ～Ⅺ。地震破裂的力学性质为左旋扭张,与则木河断裂晚第四纪以来的活动一致。地震破裂具有向南突出发展的不对称特点     

断层横向构造在逆冲型地震破裂中的作用——以汶川地震小鱼洞断层为例

大地震破裂大多由横向构造(如阶区、弯曲和分叉)所分割的多个段落组成.2008年5·12汶川地震破裂沿北东走向上穿过了多个横向构造部位,特别在震中北东45 km的位置,小鱼洞断层、北川断层和彭灌断层三者之间呈现复杂的断裂切割相交关系.复杂断层几何结构对破裂的扩展是有抑制还是促进的作用？在相交的断裂段之间是否存在最优的破裂顺序？本文以库仑应力分析为手段,探讨在汶川同震破裂初始30 s内,破裂在多分支断裂中选择扩展路径时的可能应力相互作用.库仑应力分析显示:如果北川断层先发生破裂,其滑动对小鱼洞断层和彭灌断层均产生强烈负应力的抑制作用,而彭灌断层的滑动却反而对小鱼洞断层和北川断层浅部有强烈正应力的促进作用.因此,从准静态应力分析角度,彭灌断层先于北川断层发生破裂的可能性较大,这一破裂顺序与小鱼洞断层参与同震破裂过程的事实相符.此外,小鱼洞断层在链接北川和彭灌断层的同震位移中可能起到桥梁作用,但非静态应力的影响.横向构造在逆冲型地震破裂扩展过程中起到的牵引作用使得逆冲型地震破裂能够比走滑型地震跨越更宽的阶区.横向构造是逆冲断裂带内广泛发育的构成单元,因此在地震危险性分析的最大潜在震级测算中应该考虑其作用.     

光学遥感影像阴影与2008年汶川地震同震地表变形的影像识别

遥感影像数据在2008年汶川地震抗震救灾和灾后恢复重建中发挥了重要的作用,充分利用遥感技术进行同震地表变形的快速识别与地震地质研究具有重要的现实意义。通过分析震后光学遥感影像的阴影、纹理等特征,以及野外获得的地表破裂变形的地质与地貌特征,总结了汶川地震同震地表变形的光学遥感影像识别特点。从遥感成像的光学原理深入解析了汶川地震断层陡坎在遥感影像上的阴影形成与识别特征,明确了成像时刻和断坎产状对影像阴影的形成和断层陡坎识别能力的约束。结合影像成像特征与汶川地震同震地表破裂特征的应用分析,客观地认识了现有遥感影像在同震地表变形应用中的局限性,可为今后的应急航空遥感方案设计提供参考     

2014年新疆于田MS7.3地震同震位移及位错反演研究

利用于田震中300 km范围内的1个GPS连续站和12个GPS流动站数据,解算得到了2014年新疆于田M_S7.3地震地表同震位移,并反演了发震断层滑动分布,探讨此次地震对周边断裂的影响.地表同震位移结果显示,GPS观测到的同震位移范围在平行发震断裂带的北东-南西向约210 km,垂直发震断裂带的北西-南东方向约为120 km,同震位移量大于10 mm的测站位于震中距约120 km以内;同震位移特征整体表现为北东-南西方向的左旋走滑和北西-南东方向的拉张特征,其中在北东-南西方向,I069测站位移最大,约为32.1 mm,在北西-南东方向,XJYT测站位移最大,约为28.1 mm;位错反演结果表明,最大滑动位于北纬36.05°,东经82.60°,位于深部约16.6 km,最大错动量为2.75 m,反演震级为M_W7.0,同震错动呈椭圆形分布,以左旋走滑为主并具有正倾滑分量,两者最大比值约为2.5：1,同震错动延伸至地表,并向北东方向延伸,总破裂长度约50 km,地表最大错动约1.0 m;同震水平位移场模拟结果显示贡嘎错断裂、康西瓦断裂和普鲁断裂等不同位置主应变特征具有差异性,这种差异特征是否影响断裂带以及周围区域的应力构造特征,值得关注.     

HORIZONTAL MOVEMENT CHARACTERISTICS OF THE ACTIVE SANWEISHAN FAULT AND ITS MECHANISM: CONSTRAINTS ON THE GROWTH OF THE NORTHERN QINGHAI-TIBETAN PLATEAU

The northern margin of the Qinghai-Tibet Plateau is currently the leading edge of uplift and expansion of the plateau. Over the years, a lot of research has been carried out on the deformation and evolution of the northeastern margin of the Qinghai-Tibet Plateau, and many ideas have been put forward, but there are also many disputes. The Altyn Tagh Fault constitutes the northern boundary of the Qinghai-Tibet Plateau, and there are two active faults on the north side of the Altyn Tagh Fault, named Sanweishan Fault with NEE strike and Nanjieshan Fault with EW strike. Especially, studies on the geometric and kinematic parameters of Sanweishan Fault since the Late Quaternary, which is nearly parallel with the Altyn Tagn Fault, are of great significance for understanding the deformation transfer and distribution in the northwestward extension of the Qinghai-Tibet Plateau. Therefore, interpretation of the fault landforms and statistical analysis of the horizontal displacement on the Sanweishan Fault and its newly discovered western extension are carried out in this paper. We believe that the Sanweishan Fault is an important branch of the eastern section of the Altyn Tagh fault zone. It is located at the front edge of the northwestern Qinghai-Tibet Plateau and is a left-lateral strike-slip and thrust active fault. Based on the interpretation of satellite imagery and microgeomorphology field investigation of Sanweishan main fault and its western segments, it's been found that the Sanweishan main fault constitutes the contact boundary between the Sanweishan Mountain and the alluvial fans. In the bedrock interior and on the north side of the Mogao Grottoes, there are also some branch faults distributed nearly parallel to the main fault. The main fault is about 150km long, striking 65°, mainly dipping SE with dip angles from 50° to 70°. The main fault can be divided into three segments in the spatial geometric distribution:the western segment(Xizhuigou-Dongshuigou, I), which is about 35km long, the middle segment(Dongshuigou-Shigongkouzi, Ⅱ), about 65km long, and the east segment(Shigongkouzi-Shuangta, Ⅲ), about 50km long. The above three segments are arranged in the left or right stepovers. In the west of Mingshashan, it's been found that the fault scarps are distributed near Danghe Reservoir and Yangguan Town in the west of Minshashan Mountain, and we thought those scarps are the westward extension of the main Sanweishan Fault. Along the main fault and its western extension, the different levels of water system(including gullies and rills)and ridges have been offset synchronously, forming a series of fault micro-geomorphology. The scale of the offset water system is proportional to the horizontal displacement. The frequency statistical analysis of the horizontal displacement shows that the displacement has obvious grouping characteristics, which are divided into 6 groups, and the corresponding peaks are 3.4m, 6.7m, 11.4m, 15m, 22m and 26m, respectively. Among them, 3.4m represents the coseismic displacement of the latest ancient earthquake event, and the larger displacement peak represents the accumulation of coseismic displacements of multi-paleoearthquake events. This kind of displacement characterized by approximately equal interval increase indicates that the Sanweishan Fault has experienced multiple characteristic earthquakes since the Late Quaternary and has the possibility of occurrence of earthquakes greater than magnitude 7. The distribution of displacement and structural transformation of the end of the fault indicate that Sanweishan Fault is an "Altyn Tagh Fault"in its infancy. The activities of Sanweishan Fault and its accompanying mountain uplift are the result of the transpression of the northern margin of the Qinghai-Tibet Plateau, representing one of the growth patterns of the northern margin of the plateau.     

基于库仑应力变化分析2015年尼泊尔MS8.1地震对中国大陆的影响

本文采用分层黏弹性介质模型, 模拟了2015年4月25日尼泊尔M_S8.1地震产生的同震和震后地表位移场, 计算了尼泊尔大地震引起的青藏高原及其周缘主要断裂上的同震和震后库仑应力变化。 地表位移场结果显示, 此次尼泊尔8.1级地震对中国大陆的影响区域主要是拉萨地块和羌塘地块, 对拉萨块体的影响主要表现为水平向南朝喜马拉雅构造带的汇聚作用, 垂直同震位移以下降为主, 震后以上升为主。 静态库仑破裂应力变化的计算结果显示, 尼泊尔大地震对青藏块体中南部的拉张性断层影响最为显著, 其中, 使尼泊尔地震北部的拉张断层的库仑应力显著增加, 个别断层库仑应力增加量超过0.01MPa, 而使其两侧的拉张断层库仑应力明显降低; 对青藏块体中部的走滑断裂则以正影响为主; 另外, 对南北地震带主要以负影响为主, 但量值微小。     

利用GPS观测资料分析2008年于田Ms7.3地震的同震位移及震后形变

2008年3月21日新疆于田发生Ms7.3级地震.本文通过处理、分析GPS数据,得到破裂断层北侧100 km附近的同震位移及震后形变信息.在观测区域GPS点监测到10 mm左右的同震位移,其中最大为南向14 mm,东向5 mm.同震位移呈现一致性的东南向运动特征,证实于田地震存在显著的左旋走滑分量.震后台站向西南方向运...