2010年新西兰Mw7.0主震与2011年Mw6.1余震近场强地面运动特征比较分析

摘要

The New Zealand earthquake of September 3,2010,Mw7.0 occurred in the South Island of New Zealand with depth of 10 km.The February 21,2011,South Island,New Zealand,earthquake occurred as a part of the aftershock sequence of the 2010 Mw7.0 mainshock (Darfield earthquake of 2010).This largest Mw 6.1 aftershock (Christchurch earthquake of 2011) is significantly closer to the main population center of Christchurch,New Zealand,than is the September 2010 mainshock,however,violent Mw6.1 aftershock was caused by movement along a fault that does not appear to have broken the surface.Considering the amplification of shallow velocity structure (vs30),we compared the observed horizontal PGAs (peak ground acceleration) and PGVs (peak ground velocity) of both the mainshock and aftershock with NGA (next generation attenuation),respectively.The near-field strong ground motion of the aftershock is higher than the observations of mainshock.For the New Zealand sequence,two special finite fault models,dynamical composite source model (DCSM) and scholastic finite-fault model (SFFM),are constructed for Darfield and Christchurch earthquake of 2010 and 2011,respectively.For comparison purpose,we also conducted the broadband ground motion predictions for the station of Heathcote Valley Primary School (HVSC) and Greendale station (GDLC),which are the nearest stations from the epicenter of mainshock and aftershock,respectively.We compared the advantage and limitation of the DCSM and SFFM,respectively,for developing appropriate technique to generate the shaking map in real time and for earthquake early warning.%2010年9月3日16时35分46秒新西兰南岛Greendale附近发生了Mw7.0地震,震源深度约10.0 km.2011年2月21日新西兰南岛又发生了Mw6.1地震,为2010年Mw7.0主震后最大的一次余震,震源深度约5.0 km,发震断层为Christchurch南约9 km一条近东西走向逆冲的隐伏断层,该地震造成Christchurch城内多处建筑物严重损毁.本文分析了2010年新西兰地震事件Mw7.0主震与Mw6.1余震强地面运动的特征.新西兰Mw6.1余震近场强地面运动整体高于Mw7.0主震.将主震和余震的强震观测记录分别与新一代衰减关系(NGA)进行对比,发现余震强震观测数据整体高于其震级对应的NGA.分别选取距离主震和余震震中最近且强震观测记录最高的两个台站(GDLC台站和HVSC台站)作为参照台站,建立动态复合震源模型(DCSM)及有限断层随机振动模型(SFFM)进行强地面运动的模拟计算,分析两种模型的模拟结果并对比二者的优势及局限,以便在未来工作中更好地通过模型计算强地面运动特征,实现区域化特征快速、实时分析及局部重点、细致分析相结合的目标.