Source parameter and rupture process of the M_W6.3 early strong aftershock immediately following the 2016 M_W7.8 Kaikoura earthquake(New Zealand)

The 2016 A/w7.8 Kaikoura(New Zealand)earthquake was the most complex event ever instrumentally recorded and geologically investigated,as it ruptured on more than 12 fault segments of various geometries.To study the mainshock rupture characteristics,geodetic methods like InSAR and GPS play an essential role in providing satisfactory spatial resolution.However,early strong aftershocks may cause extra ground deformation which bias the mainshock rupture inversion result.In this paper,we will focus on studying the Mw 6.3 aftershock,which is the only A/6+thrust slip aftershock that occurred only 30 minutes after the Kaikoura mainshock.We will relocate the hypocenter of this event using the hypo 2000 method,make the finite fault model(FFM)inversion for the detailed rupture processes and calculate the synthetic surface displacement to compare with the observed GPS data and figure out its influence on the mainshock study.Although we are not able to resolve the real ruptured fault of this event because of limited observation data,we infer that it is a west-ward dipping event of oblique slip mechanism,consistent with the subfault geometries of the Kaikoura mainshock.According to the inverted FFM,this event can generate 10-20 cm ground surface displacement and affect the ground displacement observation at nearby GPS stations.

Causative fault and seismogenic mechanism of the 2010 Suining M5.0 earthquake from joint modeling of seismic and InSAR data

Although the Sichuan basin is a stable block with low historical seismicity,the Suining M5.0 earthquake on January31,2010 occurred near the center of the basin,causing casualty and substantial damage.Previous studies have shown that the earthquake is very shallow and may occur in the sedimentary cover rocks,but its causative fault has not been identified.Based on local broadband seismic waveform data as well as a pair of ALOS PALSAR ascending orbit data,we explore the seismogenic mechanism via further constraining the source depth and the ruptured fault.The earthquake caused ground uplift in the southeast of the epicenter area,with a maximum line of sight displacement of about 13.6 cm,much larger than the displacement caused by a M5 earthquake at a typical depth of 10 km,which indicates that the earthquake is very shallow.Through joint inversion of seismic waveform and InSAR data,we obtain the moment magnitude of Suining earthquake as MW4.5,with the strike,dip,and rake of its fault plane as 17°,66° and 90°,respectively,and the centroid depth less than 1 km,supporting that the earthquake occurred at the shallow part of a high angle thrust fault dipping to the southeast.It is further confirmed that the earthquake may be triggered by the diffusion of high-pressure fluid migrating from the underside gas reservoir.