Abstract:

Based on a 3-D global velocity structure model, the authors used teleseismic P wave data from Asian and South American array to image the rupture process of 2016 Mw 7.8 New Zealand earthquake via backprojection analysis. The results show that the rupture is a unilateral one with northeast direction, extending to the ocean. The rupture speed is about 1.65 km/s. There are two phases dominated by high frequency power radiation, occurring during 20−40 s and 60−80 s, respectively. The second phase is the major one, whose distribution of low frequency power radiation is consistent with the centroid location of the event. The high frequency back projection result of the South American data is better correlated with the peak ground acceleration result. According to the comparison and analysis of the Asian and South American results, it could be inferred that in order to obtain more detailed rupture information of high frequency, the data of array deployed in the region with lower 3-D heterogeneity should be adopted in back projection analysis to enhance the coherency of waveforms.

Key words: 2016 New Zealand earthquake, rupture process, 3-D earth model, back projection method

摘要：

基于三维地球模型, 分别使用南美洲和亚洲的远场P波数据资料, 对2016年11月13日Mw7.8级新西兰地震的破裂过程进行反投影成像分析。结果显示, 该地震是破裂方向为东北的单边破裂, 破裂长度约为140 km, 延伸至海中, 破裂速度约为1.65 km/s。该地震的高频能量释放有两个阶段, 分别为20~40 s和60~80 s, 其中第二阶段为能量释放的主要阶段, 该阶段的低频能量聚束分布与该地震的矩心位置较为一致。从南美洲数据得到的高频破裂分布与地面峰值加速度的结果较为一致。通过对比分析南美洲和亚洲数据的结果, 指出在反投影分析中, 为了获取更精确的高频破裂细节, 应尽量选取位于三维不均匀性较弱区域的台阵数据, 以增强高频信号的相关性。

关键词: 2016年新西兰地震, 破裂过程, 三维地球模型, 反投影方法