六盤山東麓斷裂帶晚第四紀活動性研究
[Abstract]:The eastern foot fault zone of the Liupanshan Mountain is an important part of the northern section of the north-south structure. The geological structure pattern and the current GPS velocity profile are very similar to the Longmen Mountain structure. The occurrence of the Wenchuan earthquake indicates that we can not ignore the weak changes of the velocity gradient on both sides of the fault zone. It is not possible to underestimate the seismic risk of such a fracture. Therefore, the research on the activity of the fault zone in the eastern foot of the Liupanshan Mountain can provide the basic data and the basis for the research and analysis of the regional seismic risk. The main work of this thesis is: (1) to establish the time-space sequence of the layered geomorphic surface of the Liupanshan region; (2) to find the latest active evidence of the fault, to obtain the fault activity parameter; and (3) to construct the construction difference uplift rate (? UT) model, introducing the geomorphology parameter channel steep index (), indirectly analyzing the regional uplift activity; (4) combining with the existing regional precision leveling data and the cross-fault long leveling data, and combining the geological profile of different sections of the cross-fault zone, The vertical movement characteristics of the six-plate mountain structure are analyzed. Based on the above methods or parameters, the characteristics of the activity and tectonic deformation since the late Quaternary of the eastern foot fault zone of the Liupa Mountain are comprehensively analyzed, and the phenomenon of the change of the weak velocity gradient in the vicinity of the fault zone is discussed. The following conclusions are obtained: (1) The Haiyuan fault zone and the eastern foot fault zone of the Liupanshan Mountain are connected with the small faults of the two left-order oblique faults, which are the fault (f1) and the Bao-jiabao fault (f2), and the active properties of the fault (f1) and the Baojiabao fault (f2) are mainly the left-hand horizontal sliding, The activity habits of the tail end of the Haiyuan fault zone may be inherited. (2) The total length of the eastern foot fault zone of the Liupanshan Mountain is about 90km, and the whole direction is near the north and south. The fault property mainly consists of the thrust and the left-handed sliding. By means of remote sensing interpretation, digital elevation model analysis and field geological survey, the eastern foot fault zone of the Liupanshan Mountain is divided into three sections: the north section (F1) of the eastern foot fault zone of the Liupanshan Mountain is in the direction of 320 擄 -330 擄, and is a left-hand sliding and high-angle thrust property; the middle section (F2) is broken to 350 擄-SN, It is a high-angle thrust property; the south section (F3) moves to 330-340 擄, and the low-angle thrust fault is developed in the bedrock, and the high-angle thrust property is in the Quaternary sedimentary layer. (3) The vertical sliding rate is about 0.55mm/ a since the late Pleistocene in the south section (F2) of the eastern foot fault zone of the Liupanshan Mountain; the horizontal sliding rate of the north section (F1) of the eastern foot fault zone of the Liupanshan fault zone is about 0.92-1.16 mm/ a since the late Pleistocene, and the vertical sliding rate since the Holocene is about 0.31-0.41 mm/ a. (4) Collect the research results of the terrace of the Yellow River, the Longxi River and the Terrace in the two sides of Liupanshan, and use the methods of paleomagnetism and 14C to measure the existing data of the terrace formation age and the measured terrace drawing height, and introduce the construction difference uplift rate (? UT) parameters to reflect the uplift of the area. The comparative study on the uplift rate of the structure difference between the terrace of the Yellow River and the terrace of the Yellow River in Lanzhou and the terrace of the Qihe River shows that, since the quaternary system, the difference of the average tectonic difference between the terrace of the Yellow River and the terrace in Lanzhou and the terrace of the river is increased (? UT--? ) The average value is 76.87 mm/ ka, 42.88 mm/ ka, 421.06 mm/ ka and 1050 mm/ ka. The average value is 397.70 mm/ ka, and the Longxi River terrace and the river terrace are within 3 stages. UT--? 177.37 mm/ ka, 171.83 mm/ ka and 1727 mm/ ka, respectively; the average value is 172.49mm/ ka. It is indicated that the overall activity of the west of Liupanshan Mountain is stronger than that of the east of Liupanshan Mountain, while the north section of the Liupanshan tectonic belt is more active than the south section, and there is a gradual increase of the trend. (5) Using the balanced channel longitudinal section model, the steep index (ksn) of the river course in Liupanshan area is extracted, and the data is compared and analyzed by means of the mathematical statistics method. The results show that the mean value of the steep indexes of the north section, middle section and south section of Liupanshan Mountain is 65.11, 73.53 and 71.76, respectively. The change of the steep index of the channel is mainly affected by the difference of the uplift rate of the regional rock, and the influence of the related factors such as the rock formation, the rainfall and the river load in the study area on the steep index of the channel is small. The change of the steep index of the channel in each study area reflects the distribution of the uplift rate in different regions in the north and south of Liupanshan. The uplift rate of the north section of the Liupanshan Mountain is lower, the activity of the region is weak, the middle section is the fastest and the activity is strong, and the regional uplift of the south section is between the two. (6) Based on the investigation and analysis, the activity parameters of the eastern foot fault zone of the Liupanshan Mountain are analyzed, and the difference of uplift rate is constructed (? The comprehensive analysis of various parameters and data of the profile of UT, the geomorphology parameter (), the observation of the regional precision level and the profile of the level velocity and the geological profile of different sections is as follows: the uplift activity on the west side of the Liupanshan Mountain is stronger than that of the east side, The structural deformation and activity of the north section in the east-foot fault zone of the Liupanshan Mountain show a strong tendency. It is shown that the current GPS velocity profile shows the phenomenon of weak velocity gradient near the eastern foot fault zone of the six-plate mountain, but there is obvious stress accumulation, which may be the obvious stress transformation. The horizontal movement of the region is converted into the vertical motion dominated by the regional uplift, and the different sections of the fault zone and the two sides of the six-plate mountain have different vertical movement intensity.
【學位授予單位】:中國地震局地震預測研究所
【學位級別】:碩士
【學位授予年份】:2015
【分類號】:P315.2
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