Rupture Dynamics of the 2025 M w  7.7 Myanmar Earthquake: A Bilateral Supershear Rupture on Unusually Long Fault Superhighway

Abstract The 2025 M w 7.7 Myanmar earthquake ruptured the central Sagaing fault, a previously identified seismic gap with high seismic potential. Here, we perform hundreds of 3D dynamic rupture simulations to investigate the rupture dynamics, constrained by near‐fault strong‐motion waveforms, optical and SAR pixel offsets, and a kinematic source model. Our preferred model suggests that the rupture involves asymmetric supershear ruptures, with stable rupture speeds following initial bilateral subshear propagation, as supported by the low frequency of aftershocks and high seismic radiation efficiency. The Burridge‐Andrews mechanism and free‐surface effects likely dominate the supershear transition. Moreover, the derived slip distribution exhibits segmentation in both extent and magnitude, with few shallow slip deficits, which correlate with the interseismic locking depth and slip rate. Our results demonstrate that data‐constrained dynamic rupture simulations offer valuable insights into the physical mechanisms governing complex earthquake rupture processes.