新疆古牧地断裂全新世的断错活动

新疆古牧地断裂是一条全新世活动断裂,全新世以来有４ 次明显的断错活动,历次活动的ＴＬ时间分别为１１．０３±０．８９ ｋａＢ．Ｐ．,９．７３±０．７９ ｋａＢ．Ｐ．,８．３２±０．６７ ｋａＢ．Ｐ．和６．８２±０．５４～４．８７±０．３９ ｋａＢ．Ｐ．,断错活动间隔为１．３±０．１～２．０±０．１５ ｋａ。全新世时期累积垂直断距大于５．０３ｍ ,平均活动速率大于０．４１ ｍ ｍ ／ａ     

青海省湟水盆地全新世活动断裂分布及其活动特征研究

在详细的航卫片解译地震地质调查,古地震与历史地震研究的基础上,向人们展示了湟水构造盆地全新世断层的活动图像,对地震活动作出趋势性预测,并且发现,盆地东部为一地壳稳定性较差的活动构造块体,应引起地震工作的足够重视。     

依兰-伊通断裂全新世活动的新发现及其意义

郯庐断裂带东北段依兰-伊通断裂历史上没有发生过6级以上地震,一般认为是第四纪早期活动断裂,为中强地震发震构造.通过高分辨率卫星影像解译和野外调查,在该断裂多个段落发现断错河流Ⅰ级阶地等全新世地貌面、高1～2m的地表陡坎.其中,在通河县附近的最新地表陡坎长约70km,舒兰附近的最新地表陡坎长约10km.分别对黑龙江通河县...     

中条山北麓断裂中南段全新世地震事件的初步研究

通过对中条山北麓断裂进行探槽研究,揭露了全新世以来,断裂中段和南段的3次古地震事件,包括1次发生在8 570~8 010a BP、贯通断裂中段和南段的8级以上特大地震,以及4 800~6 010a BP和2 110~320a BP发生的2次7级左右的大地震,地震复发间隔约为3 500a。研究表明,中条山北麓断裂的南段和中段在全新世发生过多次活动,活动性较强。     

全新世断层活动的不均匀性

中国内陆一些活断层在全新世发生的破裂活动表现出明显的不均匀性。在时间上的不均匀性主要表现在断层活动的间歇性、强度的变化及破裂事件的群集性上;在空间上的不均匀性主要表现在断层活动的分段差异性上。断层破裂活动的区域或段落又是迁移变换的。因之必须研究活断层的破裂分段,进行对活断层的合理分段,确定断层的间歇活动及古地震破裂事件的群集、平静的具体情况以及活动段迁移变化的过程,建立破裂事件的时间序列并确定当今所处的位置,判别断层破裂活动的复发类型。深入阐明这些断层活动习性的具体状况对克服在判定强震复发间隔中的简单化倾向,为地震危险性分析提供更合理的参数,提高地震危险性评估及概率分析的水平都是具有重要意义的。     

德钦—中甸断裂北西段全新世地震活动证据

在高分辨率遥感解译基础上,沿德钦—中甸断裂开展野外地质地貌调查和断错地貌无人机测绘等工作,并在断裂北西段德钦县北的贡卡湖附近线性断层槽谷内开挖了一个大型探槽,探槽剖面揭露出多条断裂信息。结合多个¹⁴C样品年代学分析发现,断裂明确错断了全新世地层,且揭露出一次明确地震事件E1:(1 140±30)—(1 010±30)a BP,一次可能事件E2:(570±30)—(410±30)a BP。结果表明：德钦—中甸断裂北西段全新世以来有过活动,水平方向以右旋走滑为主,垂向上具有倾滑分量,总体表现为正走滑特征。     

华北平原周边北西向强震地表地震断层及全新世断裂活动特征

讨论了华北平原周边１９７５年海城地震，１９３７年荷泽地震及１８３０年磁县地震３次强震的地表地震破裂特征以及这３个地区北西向断裂的全新世活动。研究结果表明，尽管这３次强震地表破裂显示较弱，断续分布，仍反映了存在北西向地表破裂带，活动方式呈左旋走滑兼正倾滑。     

罗山东麓断裂全新世活动特征的初步研究

本文着重研究了罗山东麓断裂的空间展布及全新世以来的活动特征。根据作者在该断裂上首次发现的第四纪断层面擦痕、冲沟右旋及断层快速错动遗迹等资料,认为它是一条与强震活动有关的全新世右旋走滑断层,其最后一次破裂事件的发生可能距今只有几百年。     

天山全新世活动断裂及古地震研究

横亘亚洲腹地的天山山脉近代构造活动十分强烈。规模较大的全新世活动断裂有２０多条，多为近东西走向的倾滑型逆断裂，常与活动褶皱相伴生。活动褶皱为无根的断裂扩展褶皱和滑脱褶皱，它的生长是受地下活动的盲断裂所控制，往往是褶皱地震潜在的地区。天山古地震活动遗迹很多，归纳其标志有：多重断层陡坎、古断塞塘、崩积楔、填充楔、推覆楔、地震断错台地和断裂扩展褶皱等。近几年对１０条全新世活动断裂进行开挖研究，已取得大地     

贺兰山东麓断裂南段套门沟-榆树沟段全新世活动与古地震

贺兰山东麓断裂是银川地堑西侧的重要构造,控制着银川地堑的西侧边界,其最新活动特征是评价未来银川市地震危险性的重要依据。文中在贺兰山东麓断裂南段套门沟—榆树沟段断裂两侧1km范围内1:10000地质填图的基础上,选择在大石头沟两侧进行探槽研究,获得该段断裂在14ka以来共发生了3次古地震事件,分别距今13.8ka、7.9ka和3.0ka,重复周期约为6ka和5ka左右     

新疆北天山江南庙断层陡坎及其形成机制

在北天山中段第一排构造外围的宁家河－三个泉河之间,有一由北倾断裂形成的反向陡坎。该陡坎应为断裂多次错动的结果,陡坎形成初期,坎南为断塞塘,沉积物年龄为５０００ａ。在宁家河剖面可见河谷阶地砾石向上游倾斜;Ⅱ级阶地错动３￣４ｍ。依断裂模式归类,江南庙断裂为后逆冲断裂。这类断裂中否能发生７级以上地震,断裂坎是否是古地震造成,目前尚不能确定。     

郯庐断裂带中段全新世活断层的特征滑动行为与特征地震

郯庐断裂带中段全新世活断层由３个独立的破裂段组成。从各破裂段的运动性质、位移分布看，断层的运动属特征地震型滑动。地震活动以强震活动为主，强震具有周期性原地重复发生的特点，且其强度基本相同；中强地震缺失或很少发生；ｂ值在高震级范围内具低ｂ值的非线性关系。这些特点正是特征地震的典型表现．根据郯庐断裂带中段活断层全新世以来的活动特点看，未来该区仍然以特征地震方式活动．按郯庐带的强震复发间隔和各段的最新一次活动时代推算，未来一段时期内新沂－宿迁段复发大震的可能性较大，安丘段次之，莒县－郯城段复发大震的可能性则很小。     

郯庐断裂带潍坊—嘉山段全新世活断层的活动方式与发震模式

郯庐断裂带潍坊－嘉山段全新世活断层由三个独立的破裂段组成。从各段的断错地貌，松散堆积物特征，断层本身的特点以及断层泥的显微构造标志看，各段具有共同的特点，就是主要粘滑运动为主，并在震后有蠕滑调整运动，各段具有断层闭锁→粘滑发震→震后调整→断层再次闭锁的发震模式，目前莒县－郯城段仍处于震后调整阶段，而安丘段和新沂－泗洪段由已处于断层闭锁的后期阶段，面临粘滑发震的危险。     

龙门山山前大邑断裂活动时代与最新构造变形样式初步研究

通过野外地质填图、3D扫描仪以及全站仪测量等技术手段,取得了大邑断裂活动时代与最新构造变形样式的初步证据。大邑断裂所在地区白垩纪和新近纪地层的褶曲变形时代应在新近纪末—早更新世,而断裂的最新活动时代是全新世,其最新构造变形样式主要表现为全新世地层的褶皱,在地貌上表现为多个山前鼓丘。这些鼓丘单个平面形态呈椭圆形,沿山前呈雁列状分布,延伸长度为2.5km。根据鼓包的剖面形态,推测大邑断裂为一条全新世活动的盲断裂     

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.     

A NEW DISCOVERY OF ACTIVITY OF FUSHAN SECTION OF THE TAN-LU FAULT ZONE IN THE LATE QUATERNARY

The east branch fault of Tan-Lu fault zone extends from Fengshan Town of Sihong County on the north shore of the Huaihe River in Jiangsu Province, into Fushan Town of Mingguang City on the south shore of Huaihe River in Anhui Province. The landform changes from Subei plain on the north of Huaihe River to Zhangbaling uplift area on the south of Huaihe River. The terrain rises gradually with larger relief amplitude. The Fushan section of the Tan-Lu fault zone is located in Ziyang to Fushan area of Mingguang City. The fault is shown in the satellite image as a clear linear image, and the fault extends along the east side of a NNE-trending hillock. In this section the Quaternary strata are unevenly distributed, which causes some difficulties in the study of recent fault activity.In recent years, the author has found that the fault of the Fushan section of the Tan-Lu fault zone on the south of the Huaihe River still has a certain control effect on the landform and the Quaternary strata. Based on satellite imagery and geological data, we select the appropriate location in the Fushan section to excavate the Santang trench Tc1 and Fushannan trench Tc2, and clean up the Fushannan profile Pm, which reveals rich phenomena of recent fault activity. Santang trench reveals three faults, and the faulting phenomenon is obvious. One of the faults shows the characteristic of right-lateral strike-slip normal faulting; Fushannan profile reveals one fault, with the same faulting behavior of right-lateral strike-slip normal fault. Comprehensive stratigraphic sample dating results indicate that the fault dislocated the middle Pleistocene strata, late Quaternary strata and early Holocene strata. All our work shows that the fault of Fushan section has intensive activity since late Pleistocene, and the latest active age can reach early Holocene. The latest earthquake occurred at(10.6±0.8)~(7.6±0.5)ka BP. The faults exposed by trenches and profiles show the characteristics of right-lateral strike-slip normal faulting, which reflects the complexity of the tectonic stress field in the area where the fault locates.