龙门山南段及其前缘地区构造特征与变形机制

发布时间：2018-03-13 23:49

本文选题：龙门山南段　切入点：平衡剖面　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：2013年4月20日,在龙门山南段的雅安市芦山县发生了M7.0级地震,引起了人们对龙门山南段构造变形的关注。本文以相关基金课题为支撑,通过平衡剖面、砂箱物理模拟等手段,基于典型地震剖面、地层展布等资料,结合历史地震数据,对龙门山南段及其前缘地区进行构造带划分,并计算三叠世以来不同时期的各构造带缩短量,讨论了龙门山南段及其前缘地区构造动力学机制。主要得到以下几点认识和结论:(1)龙门山造山带具有地层复杂多样、构造上分带分段、地貌上分界的特点。龙门山南段及其前缘地区在构造和地貌上不同于中、北段。该区晚新生代变形强烈,地形起伏度较大,发育一系列断层相关褶皱。(2)龙门山南段及其前缘地区可以划分为龙门山冲断带和龙门山前缘扩展变形带。龙门山南段前缘地区的构造样式具有明显的垂向分层的变形特点,其间发育至少三个滑脱层,可分浅部滑脱层、中部滑脱层和深部滑脱层。在浅部滑脱层滑脱层之上,从双石断裂向东至龙泉山构造带,发育数排平行排列或斜列的断层相关褶皱,它们均以中下三叠统富膏盐岩层为底部滑脱面。在该滑脱层之下,则很好地保存了先期的垒-堑式张性构造。(3)龙门山构造带断裂的活动生长产生的部分位移通过滑脱层向山前传递,遇到盲断坡的阻挡,则向相邻断层-滑脱褶皱带传递,穿过背斜核部沿主滑脱面继续向山前和盆地方向传递,缩短量的递减规律指示了构造应力的传递与衰减。(4)砂箱物理模拟实验可以直观再现大尺度区域构造和小尺度局部构造的原型及其发育过程,反映了不同性质的滑脱层或相同性质的滑脱层埋深不同所形成的构造样式的不同,一般为有无滑脱层、滑脱层粘性、滑脱层埋深等均可影响构造样式的差异。(5)芦山地震与汶川地震之间存在一定的联系,汶川地震对芦山地震具有诱发作用。两次地震机制不同,反映了龙门山地震带不同段、带的不同地震模式。(6)对比平衡剖面恢复结果和砂箱物理模拟实验,可以直观的再现四川盆地西南部变形构造的时空演化规律。由早期到晚期构造样式存在一定的演化顺序:宽缓褶皱期、冲起构造期、三角构造期、叠瓦冲断期;由盆地边缘向盆地内部构造样式也存在一定的变化规律:盆缘叠瓦逆冲断层带、盆内断层三角构造带、盆内凸起构造带、中央宽缓褶皱带。
[Abstract]:In April 20th 2013, an M 7.0 earthquake occurred in Lushan County, Ya'an City, south of Longmen Mountain, which aroused people's attention to structural deformation in the southern section of Longmen Mountain. Based on the data of typical seismic section and stratigraphic distribution and historical seismic data, the structural zones in the south section of Longmen Mountain and its front edge are divided, and the shortening amounts of each tectonic belt in different periods since Triassic are calculated. This paper discusses the tectonic dynamic mechanism of the south segment of Longmen Mountain and its leading area. The main conclusions are as follows: the Longmenshan orogenic belt has complex strata and is divided into zones. The characteristics of geomorphological demarcation. The south segment of Longmen Mountain and its leading area are different in structure and geomorphology from the middle and north segment. The late Cenozoic deformation in this area is strong, and the relief degree of topography is large. A series of fault-related folds. 2) the south segment of Longmen Mountain and its leading area can be divided into Longmen Mountain thrust belt and Longmen Mountain front spreading deformation zone. There are at least three layers of slippage, which can be divided into shallow layer, middle layer and deep layer. Several rows of parallel or oblique fault-related folds are developed, all of which take the Middle and Lower Triassic gypsum rich rock formations as the bottom slip surface. The partial displacement generated by the active growth of the faults in the Longmenshan tectonic belt is transferred to the front of the mountain through the slip layer, and when the blind fault slope is blocked, the displacement is transferred to the adjacent fault-slip fold belt. Passing through the core of the anticline along the main slip surface continues to pass towards the front of the mountain and in the direction of the basin. The decreasing law of shortening indicates that the physical simulation experiment of sand box can directly reproduce the prototype and development process of large scale regional structure and small scale local structure. It reflects the different structural styles formed by the different properties of the slippage or the different buried depth of the same kind of slippage, usually whether there is a slippage or not, and whether the slippage is viscous. There is a certain relationship between the Lushan earthquake and the Wenchuan earthquake, and the Wenchuan earthquake can induce the Lushan earthquake. The mechanism of the two earthquakes is different, which reflects the different segments of the Longmenshan seismic belt. The different seismic models of the belt are compared with the balance section recovery results and the sand box physical simulation experiments. The temporal and spatial evolution of deformed structures in southwestern Sichuan Basin can be visualized. There are certain order of evolution from early to late period: wide and slow fold period, thrust tectonic period, triangle tectonic period, imbricate thrust period; From the margin of the basin to the interior of the basin, there are also some changes in the structural style of the basin: the brick-thrust zone in the basin margin, the fault triangle structural belt in the basin, the protruding structural belt in the basin, and the wide and gentle central fold zone in the center.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.2

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