关键词: 青海玛多7.4级地震, GNSS, 同震位移

Abstract: On May 21,2021, the Maduo M7.4 earthquake in Qinghai Province caused serious disasters in Maduo County and its surrounding areas. In order to quickly obtain the GNSS coseismic displacement field and serve for the rapid investigation and determination of the earthquake situation, this paper used various methods to carry out targeted research. In this paper, we collected 18 GNSS stations surrounding the epicenter, including 7 stations that recorded 1Hz high-frequency observation data. We used three methods to process the data and obtain the coseismic displacement, including dynamic difference for 1Hz frequency by GAMIT/GLOBK Track module, static calculation for five hours of postseismic data and static calculation for multi-day data. The results show that the dynamic difference of GAMIT/GLOBK Track module has ability to quickly solve the data. When using the high frequency data to obtain coseismic deformation by Track module, it is suitable for the near field stations which have large value of coseismic deformation. However, in the far field, the accuracy of the solution is at cm level which is restricted by the distance of both stations. Although the results obtained by Track are not accurate, it can be used as a method to quickly determine the motion characteristics and displacement of the surface. The static calculation for five hours data is more time-sensitive than the results obtained by the multi-day static calculation. Comparing the results obtained by static calculation for five hours data and multi-day, the magnitude, direction and influence range of the displacements of the two methods have strong consistency. However, the accuracy of the results from 5 hours data is relatively low at the far away station. When the displacement value is small, it is difficult to obtain the accurate results, and the difference is 1-4mm. Taking into account the timeliness of the 5 hours postseismic data, we believe that the results are credible as a quick emergency consultation data after earthquake. Based on the analysis of various results, we preliminary judged the Maduo earthquake is a dominated by left-handed strike-slip. At present, the maximum displacement of the QHMD station, which is about 40km from the epicenter, is about 24cm in western and 8cm in northern. The earthquake affected the area around epicenter including Maduo, Xining, Dulan,Delingh areas in the north and Zebra and Ganzi areas in the south. From the comparison of the static calculation results from 5 hours and multi-day, it is believed that the postseismic deformation process in the near field is significant, and it is still requires continued attention in the later stages.

Key words: the MaDou M7.4 earthquake in Qinghai Province, GNSS, coseismic displacement