Surface Rupture of the 2025 Mw 7.7 Mandalay, Myanmar, Earthquake: Insights from Field and Optical Remote Sensing Observations

Abstract We document coseismic right-lateral offsets of the 2025 Mw 7.7 Mandalay earthquake in Myanmar using post-quake field surveys and optical remote sensing data. Both results confirm that the 2025 Mandalay earthquake generated a surface rupture exceeding 470 km in length, extending from the central to southern section of the Sagaing fault. Our investigation confirmed the presence of a continuous, narrow rupture, with coseismic slip peaking at ∼4.6 m across the rupture, and ∼6.2 m from optical satellite imagery in the northern Sagaing Hills. Although the slip distribution measured in the field shows a pattern similar to that derived from optical satellite data, comparison of field measurements against remote sensing observations reveals a systematic ∼1 m deficit along most parts of the rupture. This difference suggests that a substantial portion of displacement was accommodated by distributed deformation within unconsolidated Quaternary alluvial deposits in the very shallow part of the fault. This interpretation is further supported by a highly localized offset along the fault section that cuts through metamorphic rocks with minimal overlying sediments in the Sagaing Hills. Since the southernmost segment of the Sagaing fault, which last ruptured in May 1930, is the principal remaining unruptured section, we highlight the seismic hazard potential for densely populated southern Myanmar, necessitating urgent paleoseismological work and seismic risk assessment.