Source parameters of the 2016 M_S8.0 New Zealand earthquake and characteristics of strong ground motion observations

The New Zealand earthquake of November 13, 2016, M_S8.0 occurred near the Kaikoura area in the South Island, New Zealand, with focal depth of 11 km. The M_S8.0 earthquake occurred on the transform boundary faults between the Pacific Plate and the Australian Plate, and the focal mechanism solution shows the earthquake is of thrust type event. Two people were killed, twenty or so people were injured and more than ten buildings were destroyed during this earthquake, so the damage level is not so severe in consideration about the huge magnitude. In this study, we analyzed the dynamic source process according to the source parameters, it can be confirmed that the radiated energy and the apparent stress of the New Zealand earthquake are small and minor. The results indicate a frictional overshoot behavior in the dynamic source process of the earthquake, which is actually with sufficient rupture and more abundant moderate aftershocks. Comparison with the next generation attenuation (NGA) relationship indicates that the observed horizontal peak ground acceleration (PGA) of the strong ground motion is generally small. The ground motion observations show that the recordings of New Zealand M_S8.0 earthquake are less than the New Zealand M_W6.1 earthquake in 2011 with nearly 200 deaths. In addition, we studied the characteristics of the observed PGAs at the six near-fault stations, which are located in the area less than 10 km to the main fault. The relatively high ground motion of the six stations may be produced by the higher slip around the asperity area rather than the initial rupture position on the main plane. In fact, the less damage level of New Zealand M_S8.0 earthquake may probably result from the smaller strong ground motion and the rare population in the near fault area, with the most severe surface destruction.