Abstract:We study the Jiuzhaigou MS7.0 earthquake in August 8, 2017, using observation data from 10 broadband seismometers near the epicenter before the earthquake, to calculate the permutation entropy of ground motion velocity. We investigate the relationship between the temporal-spatial variation characteristics of permutation entropy and the formation of large earthquakes. The results show that there were two abnormal episodes of permutation entropy in late July 2017; the largest one occurred at the end of July 2017. There was an entropy reduction process at all 10 stations. Among them, the decreases of permutation entropy at Maerkang(MEK), Zhouqu(ZHQ), and Diebu(DBT) stations were relatively large, with entropy values of 0.75, 0.76, and 0.79, respectively, which decrease by 12%, 12%, and 10% compared to the mean, respectively. The decrease of entropy at multiple stations indicate that there was an orderly vibration source in the crustal movement. The spatial evolution images of the low-value areas in the northeast and southwest of epicenter also indicate that there is a correlation between the abnormal change of entropy and the formation of this large earthquake. Based on previous research results, we believe that the eastward movement of Qinghai-Tibet plateau block and its blockage by the north China block and the south China block resulted in the energy accumulation of this earthquake. The Jiuzhaigou MS7.0 earthquake was triggered by upwelling and rotation of the lower crustal material after it was blocked by the Sichuan basin.
XU Kangsheng,LI Ying,LI Xiaoxue et al. Seismological Characteristics of Seismogenic Process of the Jiuzhaigou MS7.0 Earthquake[J]. jgg, 2024, 44(5): 497-502.