Surface rupture characteristics and macroseismic effects of the 2025 Mw 7.7 Sagaing fault earthquake in central Myanmar

The 2025 M 7.7 Myanmar earthquake affected over 30 million people across Myanmar and the broader Asian region. The earthquake caused over 5,000 fatalities, injured thousands, and left several hundred people missing. Damage extended across Myanmar, Thailand, and China, with strong shaking felt throughout Southeast Asia. The rupture propagated for over 450 km, one of the longest strike-slip earthquake ruptures worldwide, cutting through densely populated and economically important regions of central Myanmar. However, the ongoing military coup and subsequent civil conflict between the central army and People’s Defence Forces (PDFs) severely limited rescue operations and ground-based field investigations. As a result, the assessment of rupture characteristics and, slip distribution, remains limited due to gaps in ground observations.In this study, we investigate rupture characteristics and coseismic offsets using ground-based field survey data integrated with remote-sensing observations and social media-derived felt reports and rupture information. Near the northern rupture termination, which coincides with an active conflict area, we mapped rupture patterns using newly updated Google Earth imagery, validated through reports of rupture posted by locals on social media (Facebook). Along the inferred 1839 M7+ rupture segment, details of the surface rupture were documented using unmanned aerial vehicle (UAV) and tape-and-compass surveys. In the restricted regions controlled by the central army, from Nay Pyi Taw to the southern rupture termination, coseismic offsets were measured using tape-and-compass methods only.Slip amounts measured from ground-based surveys south of Mandalay systematically underestimate offsets determined from remote sensing, suggesting a significant fraction of the deformation occurred beyond a few meters of the main fault zone. Nonetheless, our mapping indicates that the 2025 surface rupture partially or fully overlapped multiple earlier historical Sagaing fault ruptures, including those in 1839 (Mw 7+), 1956 (Mw 7.1), 1929 (Mw ~7.0), 1930 (Mw 7.3) and 2012 (Mw 6.8). The observed macroseismic effects are comparable to those inferred for the 1839 Ava earthquake, which was poorly understood due to limited historical data. These ground-based data provide critical insights into the rupture behaviour over multiple earthquake cycles of fault segments that, at least in 2025, are inferred to have produced supershear rupture.