摘要:
2025-01-07，西藏定日Ms 6.8地震造成了重大人员伤亡，快速获取近场同震地表形变并确定地震震级对震后快速响应、防震减灾至关重要。随着北斗三号精密单点定位技术（precise point positioning，PPP） B2b技术的成熟及地震周边高频全球导航卫星系统（global navigation satellite system,GNSS）测站的布设，为此次地震研究提供了宝贵的观测资料。利用PPP-B2b技术对9个GNSS 1Hz和50Hz高频观测数据进行地表形变监测和震级反演研究。首先利用PPP-B2b技术对广播星历进行改正，获取实时高精度轨道和钟差产品，然后基于精密单点定位获取测站地表形变和地震波，并与事后PPP结果进行对比，最后开展基于GNSS观测的预警震级确定研究。结果表明，基于B2b改正产品解算的地震波形与事后精密产品解算结果相比，在东、北和垂向的均方根误差分别为0.40 cm、0.41 cm和1.34 cm，表明B2b改正产品可用于高频GNSS地震形变监测。基于B2b产品反演的震级结果为7.16，与事后PPP反演的震级相差0.08，与美国地质调查局发布的矩震级相差0.06，验证了B2b精密产品在震级反演中的有效性。50 Hz超高频GNSS结果表明，1 Hz GNSS监测对近场测站地震波存在一定失真，综合考虑网络传输能力和失真问题，认为5～10 Hz采样可满足地震监测相关需求。
Abstract:
Objectives:On January 7, 2025, the Ms 6.8 earthquake in Dingri, Tibet resulted in significant casualties. Rapidly capturing near-field seismic surface deformation and accurately estimating earthquake magnitude are crucial for post-earthquake response and disaster mitigation. The development of BDS-3 precise point positioning, (PPP) B2b technology and the deployment of high-rate global navigation satellite system(GNSS) stations in the seismic region provide valuable observational data for this study. Methods:This study utilizes PPPB2b corrections to process 1 Hz and 50 Hz GNSS data from nine stations for surface deformation monitoring and magnitude estimation. First, PPP-B2b is applied to correct broadcast ephemerides, generating real-time highprecision orbit and clock products. These corrections are then used in PPP to derive ground displacement and seismic waveforms, which are compared with post-processed PPP results. Finally, an investigation is conducted on earthquake magnitude estimation based on GNSS observations. Results:The results show that seismic waveforms derived using B2b-corrected products exhibit root mean square errors of 0.40 cm, 0.41 cm, and 1.34 cm in the east, north, and vertical components, respectively, compared to solutions based on post-processed precise products. This confirms the feasibility of B2b-corrected products for high-rate GNSS seismic deformation monitoring. The earthquake magnitude estimated using B2b-corrected products is 7.16, differing by 0.08 from the post-processed PPP result and by 0.06 from the moment magnitude reported by the United States Geological Survey, demonstrating the effectiveness of B2b precise products for magnitude estimation. Additionally, 50 Hz ultra-high-rate GNSS data reveal that 1 Hz GNSS monitoring exhibit aliasing distortion in near-field seismic waveforms. Considering both network transmission capacity and waveform fidelity, a sampling rate of 5-10 Hz is recommended for seismic monitoring applications. Conclusions:The BDS PPP-B2b technology, in conjunction with ultra-high-rate GNSS, has effectively facilitated the monitoring of surface deformation and the inversion of early warning magnitudes for the Ms 6.8 earthquake in Dingri, Tibet, demonstrating its feasibility and reliability.
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