Supershear Rupture Along the Sagaing Fault Seismic Gap: The 2025 Myanmar Earthquake

The 28 March 2025 M$_W$7.7 Myanmar earthquake on the Sagaing fault caused widespread building collapses and over 3800 fatalities, as well as strong shaking in Bangkok. High‐frequency backprojection very early on revealed an ∼500 km rupture. Following a bilateral subshear propagation, the rupture accelerated southward to at least 5.3 km/s, reaching the stable supershear regime, as also confirmed by Mach‐cone analysis with Love waves. Pixel tracking analysis from optical and radar imagery confirms the rupture length and indicates a peak surface offset of 5 m and average offsets of 3–4 m along the rupture zone. Pseudodynamic rupture inversion constrained by seismic waveforms and the radar‐interferometric deformation field indicates ∼4 m slip over ∼15 km depth range. The earthquake yielded unusually few aftershocks; its supershear rupture likely released most of the accumulated stress. It appears that the rupture almost certainly broke the Sagaing gap and very likely overlapped completely with the 1956 M 7.0 event. It may also have partially overlapped with the 1946 M 7.8 rupture zone in the north and the 1930 M 7.5 event in the south. Acceleration to supershear only started in the gap area, and the rupture decelerated and arrested after moving into the previously broken segment.