芦山7级地震的同震位移估计和震源滑动模型反演尝试

利用自动经验基线校正方法，分析2013年4月20日芦山M_S7.0级地震13个近场强震动台的观测资料，以估算同震位移场分布，并据此反演了震源滑动模型.经与GPS结果比较，两种不同方法给出的芦山7级地震的水平近场同震位移场幅度都不超过cm级，均显示为典型的逆冲型地震（兼有少量左旋走滑错动）.强震最大水平和垂直永久位移分别为4.9 cm和4.4 cm，分别出现在51YAM台和51QLY 台.两种资料反演的震源滑动模型虽显示多事件特征，但主要滑动均集中在第一次事件，即初始滑动点两侧的走向长约30 km、倾向长约25 km的相对集中的较小范围内，强震和GPS模型的最大滑动量分别为1.14 m和1.09 m，较为一致.其余子事件滑动量小且分布零散，不能排除其数值效应的因素.反演矩震级均在M_w6.7左右，地表破裂应该不明显.文章还讨论了目前在我国利用近场强震动记录估计M_w6~7级地震同震位移场存在的困难和问题，为今后类似工作提供参考.

Slip model and co-seismic displacement field derived from near-source strong motion records of the Lushan MS7.0 earthquake on 20 April 2013

Near-source co-seismic displacement field of the 20 April 2013 M_S7.0 Lushan, Sichuan earthquake is estimated from digital strong-motion records after correction for their baseline errors using an improved empirical method and compared with the GPS observations. Furthermore, different slip models of the earthquake are inverted from the GPS and strong-motion based displacement data separately and jointly, which are in good agreement. Both show that the earthquake is dominated by the thrust mechanism(also a few left-lateral dislocations). The maximum horizontal and vertical co-seismic displacements reached 4.9 cm and 4.4 cm, and occurred at stations 51YAM and 51QLY, respectively. The fault slips are mainly distributed around the first event and in an area of about 30 km along the strike and 25 km along the dip. The moment magnitude is estimated to be M_w6.7, and the peak slip is about 1.14 m from strong motion data and 1.09 m from GPS data. The surface rupture should be very small. Finally, we discuss the minimum requirements on the strong-motion data that ensure a reliable recovery of the co-seismic displacement data and corresponding problems in the current strong-motion networks in China.