Directivity effect on long-period ground motion of the Ms6.8 earthquake and its aftershock in Luding,Sichuan on 2022
The seismogenic fault of Luding Ms6.8 earthquake is characterized as a typical strike-slip fault,exhibiting a large dip angle and a relatively small rake angle.To study the directivity effect caused by this earthquake,this paper compared the acceleration time-history records obtained by 121 strong-motion stations located within 100 kilometers from the epicenter with the prediction results based on the attenuation model generated from historical earthquakes in southwest China.The analysis of distribution of the residual error was conducted on the long periods of acceleration response spectra,and a comparison was made between the mainshock and aftershocks with two completely different source mechanisms.The results indicate that:(1)The directivity effect of the Luding mainshock is obvious,which is reflected particularly in the periods of T=1.5～3 s,where the forward amplification effect is significant in the southeast direction.In the period range of T=0.5 s to 1.5 s,the backward attenuation effect in the northwest direction is significant,which is consistent with the directional mechanism caused by the rupture.(2)The directional effect is not obvious in the aftershocks,which are reverse faults.(3)The directivity effect of different strike-slip earthquakes is manifested differently at different periods.The amplification effect of this Luding mainshock at periods of T=0.5～4 s is greater than that of others.In contrast,the 2022 Markam's earthquakes sequence and the 2016 Kumamoto earthquake in Japan show different results.The former is concentrated in the range of T=2 s and 3～6 s,while the directivity effect of the latter increases with the increase of the period.
万方数据
维普
