Dynamic segmentation of the Sagaing fault

The structurally simple Sagaing fault, which ruptured during the 2025 moment magnitude 7.7 Mandalay earthquake, exhibits clear dynamic segmentation despite lacking major geometric complexities. Using physics-based seismic cycle simulations, we tested the hypothesis that dynamic segmentation on the Sagaing fault is influenced by a northward increase in long-term slip rates from 18 to 28 millimeter/year. Models incorporating geodetically constrained long-term slip rates reproduced the rupture extent of historical earthquakes and the geodetically inferred slip distribution of the 2025 mainshock. Slip rate contrasts of 10 to 20% between adjacent segments generate sufficient heterogeneous stress accumulation to initiate dynamic segmentation, regulating earthquake recurrence patterns and maximum magnitudes across the fault system. These results highlight the value of integrating geodetic, geological, and seismological observations to improve seismic hazard assessment.