| Earthquake rupture process indicates the whole slip behaviours occurred on the fault plane during an earthquake,including slip initation,evoluition,propagation and termination.In this thesis,with the constraints from static GNSS and InSAR offsets,high-rates GNSS waveforms and teleseismic waveforms,I invert rupture scenarios for2017 Mw 6.3 Jinghe event,2020 M 7.8 Simeonof event and 2021 M 7.3 Maduo event.The Jinghe,Xinjiang,earthquake on 8 August 2017 is not only one of the largest events that happened along the North Tien Shan,but also the first Mw>6 event that received adequate seismic and geodetic observations in this region,providing a rare chance to gain insights into the faults that bound the Tien Shan.A previous rupture model（Zhang et al.2020）was built based on a hypothesis of a north-dipping seismogenic fault,but field geological mapping suggests the fault to be south-dipping.Different fault geometry would result in different rupture scenarios.Here,this thesis reconstructed the coseismic ground deformation with GNSS observations and Sentinel-1A interferograms,modeled the rupture process on the geologically consistent fault plane with constraints from GNSS,InSAR data and teleseismic P waveforms.Our results demonstrate that this earthquake occurred on a ramp fault buried under the foothills of the North Tien Shan,with strike 86.8°and dip 46°.The unidirectional coseismic rupture extended 20 km along strike and down to a depth of 20 km with an average rupture velocity around 1.9 km/s.Primary slip occurred within 3～7 s after the rupture initiation with a peak of 0.38 m.This event released 3.78×1018 N·m seismic moment,corresponding to Mw 6.31.Modeling the interseismic deformation shows that the seismogenic fault of the 2017 Jinghe event absorbs about 5.2±1.0 mm/yr crustal shortening between the Junngar basin and the North Tien Shan.The recurrence interval for earthquakes of the same magnitude as the 2017 Jinghe earthquake is estimated to be73±14 years based on the coseismic slip and interseismic slip rate.On 22 July 2020,the M 7.8 Simeonof megathrust earthquake struck offshore of the Alaska Peninsula.This was the largest event since 1917 in the enigmatic area known as the Shumagin seismic gap,a region of transitional plate interface coupling from highly coupled to the east to creeping to the west.Hence,this event provides a rare chance to understand rupture mechanics on such heterogeneously coupled faults.In this study,this thesis examines the rupture process of the 2020 Simeonof earthquake with a combination of static GNSS displacements,InSAR displacements,high-rate GNSS waveforms and tele-seismic waveforms.Due to the discontinuous nature of the deformation field,this thesis uses InSAR data for individual islands and tie the displacement field either to GNSS observations or keep these“floating”,i.e.this thesis estimate an ambiguity parameter during the inversion.Our results demonstrated that the rupture process of this event is unidirectional,initiating at the hypocenter and propagating westward for about 130 s with an average rupture velocity of～1.9 km/s.The highest slip was centered below the Koniuji Islands and occurred between 20 s to50 s after the rupture initiation.We find that InSAR observations,especially“floating”data on near-field islands,provide essential constraints for the slip inversion,building confidence in the slipping of the less coupled region.Comparison with an existing and an alternative plate coupling model demonstrated that the remaining slip budget is unlikely to be able to generate a large event at depths from 30 to 40 km,as the Shumagin seismic gap has been mostly filled by the 2020 Simeonof earthquake at those depths.However,both coupling models suggest a substantial slip deficit in shallow near trench regions,suggesting that a significant earthquake can still occur.Seafloor geodetic observations are required to further constrain the near-trench plate coupling.Supershear earthquake,whose rupture speed exceeds the velocity of shearing waves in rocks,is a unique and rare earthquake type.Only 10+earthquakes have been identified to be supershear events worldwide so far.Supershear processing research will improve our understanding of the physical mechanisms of earthquakes.On 21 May 2021（UTC）,M 7.3 Maduo earthquake struck eastern Tibet.Compared with prior static models,this thesis presents a spatio-temporal finite fault slip model for the 2021 M 7.3 Maduo event,with the constraints from static GNSS displacements,InSAR line-of-sight（LOS）offsets,high-rate GNSS waveforms,and global teleseismic body waveforms.The results demonstrate that this event has an archetype bilateral slip pattern,rupturing～160 km along strike and four asperities with an average rupture speed of～2.6 km/s.The main slip occurred at 4-8 km depth with～4.2 m peak slip.Owing to tight temporal constraints from the near-field dense high-rate GNSS network,this thesis find the Maduo earthquake suffered a 60 km length supershear propagation originating at～18km east of the epicenter and arresting at the east bend fault segments.The complex coseismic slip pattern of the Maduo earthquake suggests a possible wide diversity in seismogenic fault roughness and background shear stress inside the Songpan-Ganzi terrane. |
