GNSS-illuminated kinematics of the Sagaing fault system, Myanmar: Implications for the 2025 Mw 7.7 Mandalay Earthquake

The 2025 M w 7.7 Mandalay earthquake occurred along the central-southern segment of the Sagaing fault system in Myanmar, a major Quaternary strike-slip fault system that extends longitudinally through the entire country. The kinematics of the fault system prior to the large earthquake remains open to debate, and the linkage between preseismic deformation and coseismic rupture is still not clear. In this study, we collect GNSS observational data over the Myanmar territory, and adopt a two-dimensional dislocation model to quantify the loading rate, locking depth and seismic magnitude prior to the 2025 Mandalay earthquake of the major segments along the Sagaing fault system. The results demonstrate loading rates of 18–24 mm/yr, locking depths of 8–18 km, and seismic magnitudes ranging from M w 7.2 to M w 7.6 for three major segments, with the Meiktila segment hosting a maximum slip rate at 24 mm/yr, a largest locking depth at 18 km, and a maximum magnitude of M w 7.6. In addition, we calculate the moment magnitude of the 2025 Mandalay large earthquake, using the geodetically-derived preseismic fault kinematic parameters of the major segments. We derive an updated magnitude of more than M w 7.8, with the Meiktila segment identified as the major seismogenic faulting during the 2025 large earthquake. The unruptured Bago segment in the southernmost section, which has the potential to generate an M w ∼ 7.4 earthquake, underscores a significantly elevated seismic hazard level in the region.