The New Zealand earthquake of February 21, 2011, MW6. 1 occurred in the South Island, New Zealand with the epicenter at longitude 172. 70癊 and latitude 43. 58癝, and with depth of 5 km. The MW6. 1 earthquake occurred on an unknown blind fault involving oblique-thrust faulting, and this fault is 9 km south of Christchurch, which is the third largest city of New Zealand, with a striking direction from east toward west. At least 163 were killed and lots of structures were destroyed in Christchurch city. The Peak Value of Acceleration (PGA) observed at station Heathcote Valley Primary School (HVSC), which is 1 km away from the epicenter, is up to almost 2. Og. The ground-motion observation suggests that the New Zealand earthquake generated higher than normal near-fault ground motion. In this study, we analyzed the source spectral parameters based on the observations, and estimated the near-field groundrnmotion based on the Brune's circle model. The results indicate that the larger ground motion may be produced by higher effective stress drop (dynamic stress drop,A展开▼
