Rupture directivity effect of near-field ground motions in Italy M_W6.2 earthquake on August 24， 2016

For investigating the rupture directivity effect of the central Italy M_W6.2 earthquake on August 24， 2016， more than 150 strong motion stations are separated into two groups， which are SE and NW， according to the fault strike. Comparing the PGA， PGV， pseudo-acceleration response spectrum (PSA) and significant duration D_SR of two groups， the results show that: the observed PGAs, PGVs and PSAs of NW group are larger than those of SE group; the residuals between the observed and predicted PGAs and PGVs are significantly correlated with the azimuth; the observed D_SR of NW group is smaller than that of SE group. From these observations we deduce that the rupture directivity effect exists in this earthquake. Furthermore， the inversion for source rupture parameters using PGAs and PGVs, respectively， shows that the rupture is bilateral， and the M_W6.2 earthquake predominantly ruptured in the direction 345°--360°， accounting for 70%--80% of the total rupture， and the rupture velocity is 2.2--2.5 km/s. These results validate the conclusion that the differences of ground motion parameters between two groups of stations might be caused by the rupture directivity effect.