Tectonic Position and Seismotectonic Manifestations of the March 28, 2025 Mandalay Earthquake M = 7.7 (Myanmar)

The March 28, 2025 Mandalay Earthquake, with a magnitude M = 7.7 and its epicenter near the city of Mandalay, occurred within the zone of the major N–S trending active right-lateral Sagging fault. The earthquake generated a seismic rupture zone that extended mainly southward from the epicenter along this fault. Using radar interferometry and sub-pixel correlation of satellite imagery, the authors determined the parameters of the rupture zone. Its length is ~ 460 km, with right-lateral displacement reaching the maximum observed amplitude of 5.8 m. Given the hypocenter depth of 10 km, the seismic ruptures can be considered the surface expression of the earthquake source. The Sagging Fault is associated with the ophiolite belt of Myanmar, which represents relicts of the Meso-Tethys paleo-ocean, displaced by Cenozoic tectonic movements. In northern Myanmar, where the Mandalay earthquake occurred, the ophiolite belt functions as the magmatic component of the submeridional northern segment of the Sunda island arc, beneath which the Indian Plate is subducting in a north-northeast direction. While the subduction surface is gently dipping near the front of the Sunda Plate, it experiences steep subduction further to the east. The Sagging Fault lies above the eastern flank of the region of steep Indian Plate subduction. Beneath the region lies a mantle plume that reduces lithospheric thickness and causes softening of the lower crust. We suggest that the increased extent of the rupture zone of the Mandalay earthquake is due to the plasticity of the ophiolitic substrate, which facilitates rock slip, while the shallow depth of the hypocenter is related to the softening of the lower crust and upper mantle under the influence of the mantle plume. The significance of these factors is confirmed by comparing the Mandalay earthquake with the strongest earthquakes in Eastern Anatolia over the past 80 years, which occurred under similar tectonic conditions. These factors are supposed to be taken into account when assessing seismic impacts of major earthquakes.