The 28 March 2025 M_W7.7 Myanmar earthquake revealed by InSAR and POT observations: A supershear event with no shallow slip deficit

On 28 March 2025, a shallow devastating strike-slip earthquake with a moment magnitude (M_W) of 7.7 struck Mandalay, the second-largest city in Myanmar, marking the most powerful seismic event in this region over the past century. The event holds significant implications for understanding regional tectonic evolution. In this study, we utilize spaceborne interferometric synthetic aperture radar (InSAR) data and pixel offset observations in both azimuth and range directions to capture the co-seismic surface deformations associated with this earthquake, which depict clear surface ruptures extending approximately 500 km. We develop a three-segment fault slip model to estimate the detailed slip distribution of the 2025 Myanmar event. The inversion results demonstrate that a three-segment fault model with dip angles varying from 70° to 88°can effectively produce the observed coseismic surface deformation. Our analysis reveals that the earthquake is dominated by right-lateral strike-slip motions within the top 12 km of the crust. Notably, the maximum slip of 4.6 m is observed at the ground surface, suggesting no significant shallow slip deficit occurred. Furthermore, the 2025 M_W7.7 earthquake appears to have filled a previously identified seismic gap along the southern segment of the Sagaing fault. Coulomb stress transfer modeling indicates that coseismic slip on the northern segment has promoted the subsequent failure of the two southern segments. We estimate a recurrence interval of large-magnitude earthquakes (M_W > 7) of approximately 104–131 years for the seismogenic fault based on the coseismic and interseismic released seismic moments. The significant scarcity of aftershocks within the supershear rupture zone, coupled with the relatively low moment-scaled radiated energy, provides compelling evidence for supershear rupture propagation along the Sagaing fault during this earthquake.