Analysis of co-seismic ionospheric disturbance of the Qinghai Mw 7.4 earthquake on May 21, 2021

In this study, the total electron content (TEC) was extracted from Global Navigation Satellite System (GNSS) data provided by the Crustal Movement Observation Network of China (CMONOC). The ionospheric disturbances related to the Qinghai earthquake on 21 May 2021 were analysed. Significant coseismic ionospheric disturbances (CIDs) were observed near the earthquake epicentre. To further investigate the propagation characteristics of ionospheric anomalies associated with this earthquake, the epicentral area was divided into eight regions, each corresponding to a 45° sector, to analyse the characteristics of ionospheric disturbances. Firstly, based on the spatial and temporal characteristics of the slant total electron content, different degrees of ionospheric disturbances were identified at various time intervals after the earthquake. Secondly, the earthquake generated two types of coseismic ionospheric disturbances at the epicentre. The first type, with velocities of approximately 1.4 km s− 1, 1.8 km s− 1, and 1.0 km s− 1, were triggered by acoustic waves generated by the ground surface rupture induced by the earthquake. The second type, with velocities of about 0.8 km s− 1, represented another form of ionospheric disturbance induced by acoustic waves from the ground surface rupture. Thirdly, the ionospheric anomaly was most pronounced within the 90°–135° sector relative to the epicentre, corresponding to the southeast direction from the epicentre. Finally, based on the data from 15 GNSS stations at the epicentre, the coseismic deformation displacement of the earthquake was determined, with a maximum displacement of 0.24 m, and the leptokurtic slip characteristics of the earthquake were revealed.