Heterogeneous rupturing and barrier mechanism during the 2025 Mw7.7 Myanmar earthquake.

The 28.03.2025 Mw7.7 Myanmar earthquake caused surface rupture along the Sagaing fault, a major right-lateral transform fault between the Indian and Sunda Plates in Myanmar. The event was followed by another Mw6.7 earthquake twelve minutes later near Mandalay. Here we present observations from field surveys and Sentinel-1 synthetic aperture radar (SAR) imagery to constrain surface fault offset associated with this earthquake. Offset Tracking analysis of SAR satellite images reveals ground displacements exceeding 3 m along the fault, with localized offsets reaching 4-5 m in the Sagaing segment near Mandalay. Moreover, the maximum displacement is measured 4.5 m around Naypyidaw settlement further south during field survey. Fault offset distribution is affected by rheology differences and barrier effect of basement rocks on the propagation of rupture in this event, indicating the importance of inelastic aspects of earthquakes and rupture behavior. Briefly, the combination of heterogeneous rheology producing elastic and inelastic deformation and multi ruptured fault segments created inhomogeneous slip distribution along the surface rupture. The heterogeneous displacement patterns and segmented rupture behavior emphasize the importance of pre-existing fault structures in controlling coseismic slip distribution.