Slip Distribution Of The 2018 Mw 6.6 Hokkaido,Japan,Earthquake From InSAR And GPS Data

There are about 4.9 earthquakes with magnitude >5 every day around the world(from USGS statistics from 2010 to 2019).As we all know,the earthquake will bring serious loss of life and property to the cities in the focal area,and it is easy to cause secondary disasters such as fire,tsunami,landslide and debris flow.Therefore,the study of earthquake is a very urgent and significant scientific problem.Geodetic methods such as global positioning system(GPS)and interferometric synthetic aperture radar(InSAR)have been widely used in earthquake research and have their own advantages.GPS and InSAR techniques are of great significance for us to better understand the seismogenic mechanism and to establish the fault model.On September 5,2018,an earthquake with a magnitude of Mw 6.6 occurred in Hokkaido,Eastern Iburi,Japan,causing a great number of landslides and heavy loss of life and property.The tectonic background of this earthquake is very complex,and GPS and InSAR technologies have recorded accurate coseismic displacement.Therefore,this thesis uses multi-source geodetic data(GPS,InSAR)to study the seismogenic structure,coseismic slip distribution and seismogenic mechanism of this event,which is very important for us to better understand the event and to assess of regional seismic hazards.Main conclusions of this thesis are listed as follow:1.GPS and InSAR data acquisition and processing.In this thesis,GAMIT/GLOBK software was used to process GPS data,and GAMMA software was used to process InSAR data to obtain GPS and InSAR coseismic displacement fields.Based on the ascending and descending interferograms,we obtained the 2.5D deformation field and analyzed the coseismic ground deformation.In addition,the consistency of the displacement field obtained by GPS and InSAR was analyzed to get rid of the unreasonable observations.2.Obtained fault parameters from nonlinear inversion.In this thesis,the fault parameters were inverted based on the surface deformation obtained from GPS and InSAR,and the fault location,strike angle,dip angle,slip angle,length,depth and magnitude of the Hokkaido earthquake in 2018 were retrieved.3.Obtained the fault slip distribution model from linear inversion.In this study,fault parameters obtained from nonlinear inversion were used to carry out distributed slip inversion for this event.Additionally,we performed the forward simulation to the largest slip uncertainties,the checkboard test was also carried out by this thesis.4.Coulomb stress change and regional seismic risk assessment.Based on the preferred coseismic slip distribution model,this study further calculated the Coulomb stress generated by the earthquake,discussed the triggering relationship between the coseismic Coulomb stress changes and aftershock distribution;we calculated the Coulomb stress change on the fault around the earthquake area,and we evaluated the seismic risk of the focal area.5.Discussed the seismogenic structure and seismogenic mechanism of the earthquake,based on existing research achievement.