Surface deformation and early warning magnitude of 2016 Kaikoura (New Zealand) earthquake from high-rate GPS observations

On 13th November 2016, the Kaikoura region of New Zealand was struck by a major M(w)7. 8 earthquake. In this study, coseismic deformation field is derived from 1 Hz high rate GPS observations based on the GAMIT track solution module, combining with PCA spatial filtering method firstly. Then the 5 s peak displacement of P wave (P-d) and the peak ground displacement (PGD) are extracted from the real-time simulated kinematic displacement of the trackRTr module. Finally, the warning magnitude is calculated from the statistical regression model. Our results indicate that the duration time of the kinematic deformation is up to 2 min. The KAIK and HANM stations, which are closest to the epicenter, have secondary severe deformation. And the deformation amplitude of the north stations of the epicenter is larger than that of the south. The static coseismic deformation field from high-rate GPS observations shows the characteristics of the focal mechanism of strike-slip after thrust. In addition, the P-d warning magnitudes from different stations have a significant difference, with the maximum magnitude difference of M(w)2. 5. Considering the timeliness and reliability of the warning magnitude jointly, the warning magnitude from the four-station PGD joint warning method of reasonable spatial distribution can reach its initial stability (M(w)7. 56) at 23 s after the event, while final stability (M(w)7. 78) at 110 s, which is consistent with the USGS moment tensor magnitude (M(w)7. 8).