Abstract: The ascending and descending Sentinel-1 SAR imageries are used to extract the co-seismic deformation field accused by 2018 Mw6.4 Hualian earthquake in Taiwan based on the D-InSAR method. The result shows that the maximum surface deformation is about 38.2 cm which belongs to uplift mainly, and the largest displacement difference between the hangingwall and the footwall is 50 cm. We construct the fault slip distribution models of the 2018 and 2021 Hualian earthquakes with the surface deformation obtained by the InSAR observation, and the results indicate that the fault of the 2018 Mw6.4 Hualian earthquake is a concealed west-dipping fault close to the Milun fault, the maximum is 1.8 m dominated by a left-lateral strike-slip movement with a small amount of thrust, the fault rupture propagate to the western erea of the Milun fault, which have an effect on seismicity of the Lingding fault and the Milun fault. The 2021 Hualian Mw6.0 earthquake occurred in the north of the Lingding fault, the maximum slip is 0.38 m a dominated by left-lateral strike-slip, both of two events have the high dip angle. With the redistribution of the static coulomb stress and the M-T diagram of two earthquakes,we find that the 2018 Hualian earthquake have triggered the 2021 Hualian earthquake,the stress transports and accumulats from high latitude to low latitude, the seismicity between the Hualian aera and the offshore remains active in short period,present the characteristics that the small earthquakes occur frequently and birth period of medium-strong earthquakes are short.

Key words: Hualian earthquake, InSAR coseismic deformation, fault slip, coulomb stress