Using Swarm Satellite Orbit Perturbation And EGM2008 Gravity Field Model To Study Regional Tectonic Stress

Inversing regional tectonic stress field is one of research hotspots in the field of geosciences,especially the study of structural stress changes before and after geological disasters such as earthquakes.With the advent of the era of satellite measurement,the use of satellites to achieve tectonic stress calculations is the general trend.As the first ESA satellite constellation of ESA,Swarm satellites carry a variety of scientific measurement loads and can provide high-precision orbit data,which provides an opportunity to study regional and even global tectonic stress field changes.Gravity is the main driving force for tectonic stress.According to this theory,it is to establish the mathematical model of the calculated regional tectonic stress field by using the Swarm satellite orbit perturbation data and EGM2008 gravity field model,,and to implement the algorithm.The main contents and research results of the thesis are as follows:(1)Present the overview of related research in the field of tectonic stress.The research on the driving mechanism of tectonic stress,the calculation method of tectonic stress,and the tectonic stress change in geologic events are summarized.(2)Establish a mathematical model of regional tectonic stress based on gravity drive.Gravity is the main force of tectonic stress.The gravity-driven theory of tectonic stress is of great significance in explaining geodynamics and geological structural changes.Based on this theory and the infinite plate hypothesis,a mathematical model for calculating regional tectonic stress is established by using horizontal gravity total gradient,deviation of vertical line and satellite orbital motion.(3)Complete the purification of the Swarm satellite orbit data.The Swarm satellite provides high-precision simplification of dynamic orbit data,which is used to meet the requirements of subsequent research calculations,and to realize the mutual conversion between various time systems and coordinate systems of satellite orbit observation data.(4)Using the North China plate as the research area,calculate the regional tectonic stress by using the gravity anomaly and vertical deviation of the EGM2008 gravity field model to verify the reliability of the algorithm.The following conclusions are obtained from the calculation results:a)The results of the tectonic stress field of the North China plate calculated by the gravity anomaly and vertical deviation of the EGM2008 gravity fieldmodel are basically consistent with the results of previous scholars in terms of numerical values and trends;b)Compared with the calculation results of gravity anomaly,the tectonic stress field calculated by the vertical deviation is more obvious in the trend,and the result is more detailed;c)The tectonic stress field calculated by the EGM2008 gravity field model can correspond well with the actual tectonic zone and seismic zone,which provides a possibility to further analyze the tectonic stress field of the seismic region by using the calculation results of the model;d)The tectonic stress field of the North China plate calculated by the three satellite orbital perturbation data of Swarm can't be consistent with the calculation result of the gravity model,which is far from the actual stress field,which is related to the fact that the orbital perturbation does not simply contain tectonic stress.(5)Using the EGM2008 gravity field model and Swarm satellite perturbation to calculate the usual tectonic stress field in the earthquake area and the tectonic stress field change trend before and after the earthquake.The paper selected the Iraq earthquake,the Jiuzhaigou earthquake in 2017 and two deep-seismic earthquakes in the Fiji Islands in 2018.Firstly,the normal tectonic stress field in the earthquake area is calculated by using the vertical deviation of the EGM2008 gravity field model,and the basic situation of the stress field in the seismic region is analyzed.Then,using the three satellites of Swarm-Calculated the average stress of the five months before and after the earthquake,and obtained the trend graph of stress change.By comparing and analyzing the calculation results,the following conclusions are obtained:a)The tectonic stress of the shallow source seismic region calculated by the vertical deviation of the EGM2008 gravity field model can reflect the actual structural conditions well,and the location of the earthquake is located in the area where the tectonic stress is active;b)The tectonic stress in the deep source earthquake region calculated by the vertical deviation of the EGM2008 gravity field model is relatively poor and can only reflect part of the structure.However,the earthquake-stricken areas are also located in areas where the tectonic stress is relatively active;c)Compared with the other two satellites with lower orbits,Swarm-B stars can invert the trend of tectonic stress before and after the earthquake in shallowearthquakes.However,the inversion results of the three satellites for the deep source earthquakes do not reflect the trend of stress before and after the earthquake.