A seismological phenomenon preceding the 2017 Ms7.0 Jiuzhaigou earthquake

On 8 August 2017, a Ms7.0 earthquake occurred in Jiuzhaigou in the Sichuan Province of China. In this study, we obtained the vertical continuous data recorded at 12 nearby broadband seismometers from April to December 2017, in order to characterize the temporal and spatial variations in the vertical ground motion prior to the onset of the earthquake. Using the self-mutual information method, we determined that from July to August 2017, the self-mutual information value of the vertical ground motion increased at several stations. The spatiotemporal evolution also shows that the region of highest value migrates from south to north toward the earthquake epicenter. Among them, the change of SPA (the station closest to the epicenter) is the most prominent. We believe that this phenomenon is related to the formation of the Jiuzhaigou earthquake. Our work, in combination with other published works, indicates that the Jiuzhaigou earthquake was caused by the continued eastward movement and obstruction of the Qinghai Tibet Plateau by the Sichuan Basin, and the movement of Longmenshan fault is also one of the causes of the earthquake.