Damage mechanisms and seismic vulnerability of building structures following the 2025 M 7.7 Mandalay earthquake sequence, Myanmar

The M 7.7 Mandalay earthquake struck central Myanmar on March 28, 2025, at 6:20:52 UTC, resulting in widespread damage to residential buildings, public buildings, critical structures and infrastructures, heritage structures, and monuments. An M 6.7 aftershock followed the mainshock after 12 min, which aggravated damage to structures and infrastructures. More than 81,600 buildings sustained some level of damage due to the earthquake sequence per the disaster management authority. At least 3387 fatalities and 5106 injuries occurred primarily in the vicinity of the rupture propagation along the Sagaing fault. This paper presents an account of damage mechanisms observed in reinforced concrete, brick masonry, brick nogging, and wooden buildings together with heritage structures and monuments. The failure modes are juxtaposed with the status of the enforcement of seismic detailing and code compliance. We also present critiques and future improvements in the building codes. Preliminary seismic vulnerability and fragility models are derived for general purpose seismic risk/loss assessment. In addition, strong motion recorded for the mainshock event is interpreted in relation to the damage mechanisms. Global lessons regarding seismic performance of substandard, code noncompliant, and nonengineered construction systems are reflected based on field observations and forensic interpretations. We conclude that the damage mechanisms observed during the Mandalay earthquake sequence are attributed to the lack of adequate seismic considerations adhering to seismic demands, besides strong seismic excitation.