Overview

• The March 28, 2025 Mw7.7 Mandalay earthquake produced an approximately 510-kilometer continuous surface rupture along the Sagaing Fault, exceeding previously assumed segment boundaries.
• High-resolution satellite optical and radar image correlation measured a uniform average slip of about 3.3 meters with no shallow-slip deficit.
• The rupture propagated at supershear speeds that surpassed seismic shear waves, a dynamic behavior linked to the fault’s mature geometry.
• Quasidynamic simulations reproduced irregular rupture patterns and estimated that Mw>7.5 earthquakes on the Sagaing Fault recur every 141 ± 40 years.
• These findings challenge segmentation-based hazard assessments and prompt re-evaluation of earthquake preparedness on analogous faults such as California’s San Andreas.