Could the complex rupture dynamics of the 2025 Mw 7.8 Myanmar Earthquake have been predicted? 

The 2025 Mw 7.8 Myanmar earthquake produced one of the longest continental strike-slip ruptures ever recorded. Expanding beyond a known seismic gap, it struck a densely populated region with vulnerable infrastructure. Study of this earthquake is hampered by limited seismic data coverage, yet uniquely informed by exceptional CCTV footage, a near-fault station, and comprehensive satellite geodetic imagery.To understand the earthquake’s dynamics, we explore hundreds of 3‑D dynamic rupture simulations, all informed by a static slip model on a helix‑shaped fault geometry, which we geodetically inferred from Sentinel-1A/2 and ALOS-2 satellite data. Exploring various fault friction‑initial stress combinations, we identify a family of models characterized by near-critical prestress, low strength drop, and short slip‑weakening distances proportional to slip. These unexpected dynamic parameters are required to reconcile the inferred fast rupture speed with the low crustal wave velocities and the low inferred stress drop of the event. These preferred dynamic rupture models can explain space‑geodetic fault offsets, CCTV‑derived on‑fault slip‑rates, teleseismic waveforms and back-projection, and a near‑fault strong‑motion record. They spontaneously initiate unilateral supershear rupture shortly after nucleation, predominantly propagating at supershear speeds southward within a deep band. In contrast, shallow rupture, although driven by the underlying faster supershear rupture, remains sub‑shear, causing strong curvature of the rupture front. This depth‑dependent rupture speed reconciles the fast average rupture speed imaged by teleseismic back‑projection and confirmed by the early S‑wave onset at station NPW, and the subshear pulse-like phase captured by CCTV. Our dynamic rupture models imply low fracture energy, characteristic of a structurally mature, clay‑rich fault zone, potentially facilitated by hydrothermal alteration and elevated pore-fluid pressure. Additional rupture models incorporating bimaterial effects show that while a bimaterial contrast may explain the subshear–supershear dichotomy between northward- and southward-propagating rupture, such a contrast is inconsistent with the NPW record, suggesting that bimaterial conditions were likely localized. Our results demonstrate that dynamic rupture ensembles informed from a static slip model and validated by interdisciplinary observations can offer a physically grounded route for earthquake characterization, complementary to kinematic modeling. Our results indicate that the Myanmar earthquake was critically influenced by spatial variations in frictional properties and fault stress across low-fracture-energy faults with important implications for assessing seismic hazard of major strike-slip faults.