Rapid source models of the 2021 Mw 7.4 Maduo, China, earthquake inferred from high-rate BDS3/2, GPS, Galileo and GLONASS observations

On May 21, 2021, a Mw 7.4 earthquake struck the Maduo County in Qinghai province of China. The earthquake was well recorded by the surrounding high-rate Global Navigation Satellite System (GNSS) stations. In addition to GPS, GLONASS and BDS2 observations, these stations also recorded the latest BDS3 and Galileo observations. The performance of high-rate single-GNSS and fusion of multi-GNSS on warning magnitude calculation, rapid centroid moment tensor inversion and static fault slip inversion are well investigated in this study. The results demonstrate that within a short period of time (5 min), Precise Point Positioning (PPP) displacements of BDS3 alone are better than those of BDS2 alone, while the individual displacement accuracies of BDS3, GPS and Galileo are comparable. When BDS3 and BDS2 data are combined, the combined BDS accuracy is slightly better than that of GPS or Galileo alone. Compared with the single-GNSS displacements, the fusion of GPS + GLONASS + Galileo + BDS3/2 (GREC) can achieve the highest accuracy with standard deviation values of 0.25 cm, 0.22 cm and 0.53 cm in north, east and up components, respectively. For the warning magnitude estimation, BDS3 alone, BDS2 alone, combined BDS3/2, combined GPS + BDS3/2, Galileo alone and GREC all show comparable performance. The results of centroid moment tensor inversion and static fault slip inversion are related to the station distribution. When the same stations are used, the inverted centroid moment tensors and static fault slips of a single GNSS are very similar to the multi-GNSS inversion results, but the multi-GNSS centroid moment tensor series and fault slips appear to be more stable when the observation quality of a single GNSS such as GLONASS, is relatively low. The results obtained in this study imply that GPS, BDS3, Galileo and combined multi-GNSS have the potential to be used for the earthquake early warning and rapid earthquake source modeling.