Application Of High-precision Photogrammetry Method In Obtaining Quantitative Parameters Of Active Tectonics

Since the beginning of 20 th Century,the rapid development of measuring technology and dating method has promoted the development of active tectonics from the early qualitative research stage to the quantitative research stage.Quantitative research on active tectonics is inseparable from high-precision and high-resolution terrain data.The appearance and rapid development of photogrammetry provides an economic and effective technical means for the acquisition of high-precision terrain data in active tectonics research.Firstly,the paper briefly introduces the commonly used measurement methods in the study of active tectonics,and introduces the principle and development course of photogrammetry,and summarizes the application of this method in the field of active tectonics with several practical examples,such as obtaining the quantitative displacement parameters of the fault,the identification of the seismic surface rupture zone,the acquisition of the deformation field of the earthquake,the three-dimensional modeling of the trench,the study of the paleoearthquake,and so on.The potential application of photogrammetry in active tectonics is demonstrated.In order to improve the accuracy of topographic and geomorphic data obtained by photogrammetry,based on the technical flow of photogrammetry,the error sources of the method are summarized,and then two key control parameters,including the number of ground control points and the height of flight,are selected to carry out the precision analysis and test work.The results show that when carrying out the field work in a place with a relatively flat terrain using the UAVs,12 to 15 ground control points should be set up,and then ideal topographic survey results can be obtained.With the increase of the number of ground control points,the improvement of accuracy is no longer obvious.With the increase of flight height,the elevation accuracy has a tendency to decrease obviously.In this test,the accuracy is highest when the flight height is between 40 and 60 meters.With 90% confidence degree,the accuracy of terrain data is within 10-15 cm,and the elevation precision is within 5-10 cm.When using photogrammetry to acquire terrain data,the two key factors,the number of ground control points and the height of flight,have a significant impact on the accuracy of terrain data.The test results provide good reference and guidance for obtaining topographic and geomorphic data in the study of active tectonics using the photogrammetry method.On the basis of detailed analysis and test of photogrammetry,Elashan Fault(ELF)and the Northern Margin Fault of the Caka basin(CKF),which have rarely been studied with different motion properties and contentious slip rate,are selected as the research objects.Based on the high-precision photogrammetry method and the collection and testing of chronological samples,a quantitative study of the activity of the two faults has been carried out.Based on the results of the preceding precision analysis test,acquisition of high-precision topographic data acquisition is carried out on the ELF and CKF.In order to better obtain quantitative parameters of active tectonics based on the high-resolution DEM,3 vertical displacement measuring tools with graphical user interface(GUI)and a horizontal displacement measuring tool that can "restore" threedimensional geomorphology for linear geomorphology are developed in this paper.Based on these fault displacement measurement tools,we selected two typical fault geomorphic points on ELF and CKF,and obtained the fault displacement of several research points.In addition,in order to fully demonstrate the technical advantages of photogrammetry method in the field of active tectonics,the paper aims at the problems of fine geomorphic mapping,extracting information and obtaining high precision vertical displacement,using the contour map and slope map based on high resolution DEM combined with the method of terrain profile analysis,a detailed interpretation of complex multilevel geomorphologic surfaces is carried out.Based on the results of sophisticated interpretation of geomorphology,the vertical displacement of the terraces at all levels is obtained based on high-resolution DEM.Through the topographic profile data extracted by DEM,we obtain vertical displacement parameters that is difficult to obtain directly from traditional remote sensing images.It shows great application prospect of UAV photogrammetry method in the quantitative study of active tectonics.Finally,based on the age results of geomorphic with 10 Be,the slip rate of ELF and CKF,which are still controversial,have been redefined since Late Quaternary.The horizontal slip rate of ELF is(0.72 ± 0.24)mm/a,thrusting or vertical slip rate is(0.21 ± 0.12)mm/a,and the thrust or vertical slip rate of CKF fault is(0.10 ± 0.03)mm/a,which lays the foundation for understanding the activity of fault,the pattern of regional tectonic deformation and the assessment of seismic hazard.To sum up,the research work of this paper is based on the new method and new technology of photogrammetry,and the acquisition of quantitative parameters of the active tectonics is carried out.The principle,the development process of the photogrammetry,the technical process of data acquisition and data processing,and the influence factors of accuracy are summarized.The accuracy analysis test is carried out,which provides guidance for the subsequent data acquisition of the high precision terrain and geomorphology in the fault zone.In this paper,the principle,tools and application examples of the fault displacement based on high resolution DEM are introduced,and the slip rate of the faults on both sides of the Caka basin is redefined.The research results show that photogrammetry is a low-cost and high-precision method for terrain terrain data acquisition,which has a broad application prospect in the quantitative research of active tectonics.