Observation And Modelling Of Coseismic,Postseismic Deformation Field Of Fault Zone Using Time-series InSAR Techniques

In recent years,with the continuous development of geodesy and the continuous advancement of the its application in the field of earthquakes,the study of the seismic cycles combine with the InSAR technology,observe the deformation characteristics,the postseismic deformation mechanism and the dynamic process of the long-term interseismic stress loading,has become the focus of attention of scientists in the world.As the ‘third pole',the Tibet Plateau is the most active subduction zone in the world.A series of large thrust faults and strike faults formed around the Tibet Plateau.Particularly the collision zone between the India Plate and Eurasian Plate forms several giant thrust faults extending from east to west for hundreds of kilometers,which absorbed nearly half of the converge rate of the India-Eurasia plate and formed the Himalayan seismic belt.Since 1500,at least 10 major earthquakes above M7.5 occurred.However,due to the complex topography and geomorphology of the Himalayas and southern Tibet,the harsh natural environment,and the difficulty of ground observations.The understanding of the deep geometric structure of the fault,the coseismic rupture mode of large earthquake,the deformation response of the deep zone,the afterslip of the postseismic and the rheological properties of the middle and lower crust is still limited.such as the Haiyuan earthquake in 1920,the Kunlun earthquake in 2001,the Wenchuan earthquake in 2008,the Yushu earthquake in 2010,and the Nepal earthquake in 2015.In the southern of the Tibet plateau,The tectonic structure and deformation characteristics of the northern India and southern Tibet is the focus of research around the world.By processing SAR data with long-term baseline and strong temporal and spatial correlations to obtain the deformation field in the northern India plate and southern Tibet,which provides an important basis for analyze the deformation rate of the subduction zone and the rheological characteristics of the northern India plate and Southern Tibet.On April 25,2015,an Mw7.8 earthquake occurred in Nepal,located in the Himalayan tectonic belt.This is also the strongest earthquake in the Himalayan orogenic belt since satellite observation record.The distribution of the coseismic rupture deformation and the postseismic deformation are well captured by GPS and InSAR,which help us to study the geometry and movement characteristics of the fault,the rupture mode and the mechanism of the seismogenic.In this study,we obtain the coseismic and postseismic deformation field based on the DInSAR and time-series InSAR techniques,and simulate the postseismic deformation mechanism of the Nepal earthquake.In addition,we also studies the complex multi-fault rupture characteristics of four earthquake sequences above M6.0 occurred in Mindanao in 2019.The main research contents and conclusions of the study are as follows:1.We obtain the coseismic deformation field of the Mw7.8 and Mw7.3 earthquake based on the ALOS-2 and Sentinel-1 satellite data,and analyze the deformation characteristics of the two earthquake.Inverting the fault slip distribution based on the coseismic deformation field and observation the spatial relationship of the two earthquake slip distribution.The result shows that the deformation field is uplift in southern and subsidence in northern.The slip distribution of the aftershock in depth is deeper than the main shock,there was still a 30-40 km unruptured zone between the two earthquakes.2.We process the ALOS-2 PALSAR and Sentinel-1A/B SAR data from 2015 to2019,based on the SBAS-InSAR and PS-InSAR to obtain the time-series postseismic deformation and deformation rate field.We simulate the postseismic mechanism using the kinematic aferslip model and stress-driven afterslip model,through the correlation of the observation and simulate values of GPS and InSAR data.The result shows that the deformation signal of the postseismic deformation field is reverse to the coseismic deformation field.The postseismic afterslip is mainly distributed in the downdip direction of coseismic rupture,a range of slip also exist in the updip direction.The area of the postseismic afterslip is basically same as the coseismic coulomb stress positive value area.3.We obtain the coseismic deformation field of Mindanao earthquake sequence based on the ALOS-2 and Sentinel-1A data.The earthquake sequence occurred on the conjugate fault in NE and NW strike.The maximum slip was about 1.2m.The static coulomb stress shows that the previous earthquake has the coulomb stress triggering effect on the later earthquakes.Taking the NW and NE direction as the receiving faults,the results show that the NW direction is still in coulomb stress loading environment after the earthquake.