Invited Talk
The rupture behavior of the Sagaing fault: lesson learned from the 2025 Myanmar earthquake
Wang YU, National Taiwan University
wangyu79@ntu.edu.tw

Biography

WANG Yu is an associate professor from the Department of Geosciences, National Taiwan University, Taiwan. He has been working on the active tectonics and earthquake geology of Myanmar since 2006, especially on the oblique convergent boundary offshore western Myanmar, and the southern and central sections of the Sagaing Fault. Wang Yu’s research use several different techniques to observe and quantify the tectonic deformation associated with the seismic cycle. These techniques include optical remote sensing, paleoseismological investigation, topographic and geodetic surveys. His current research targets include the shallow rupture behavior of active faults in Southeast Asia, the active fault system in eastern Taiwan, and the rapid assessment of natural hazards and fault ruptures.

The Sagaing fault is known as a major seismological source in mainland Southeast Asia. The simple, smooth, and continuous fault trace along its central and southern sections has been considered as the source of several destructive earthquakes in Myanmar, and the most recent event is the Mw 7.7 Mandalay earthquake on 28 March 2025. The Mw 7.7 earthquake is accompanied by a ~500-km-long rupture along the fault, with the largest coseismic offset reached 5 to 6 meters along the northernmost part of the rupture, and in many parts of the fault, the coseismic rupture is approximately ~4 m. Instead of being confined in the seismic gap at the central Sagaing fault, the rupture broke several fault segments, extending from the area west of Mandalay to the area near the Pyu township. The latter belongs to the fault section that ruptured in December 1930, less than 100 years ago. The amount of coseismic slip mapped in the 2025 earthquake shows high similarity to the geomorphic offset resulting from the previous earthquakes, with the largest single event offset reach 5 to 7 meters along the northern 100-km-long fault section ruptured in 2025, and about 4 meters along the central part of the 2025 fault rupture. The time interval between the 2025 and the 1839 earthquakes also matches to the mean recurrence interval we estimated from the geomorphic offset markers, suggesting the 2025 Mandalay earthquake is likely representing the characteristic earthquake rupture in the central part of the Sagaing fault. Although our previous estimation prior to the 2025 earthquake did not expect the coseismic rupture to extend to the Pyu section, a previous study did suggest an extra short recurrence interval at the Pyu section that roughly matches to the interval between the 1930 Pyu earthquake and the 2025 Mandalay earthquake. All these lines of evidence suggest that the simple geometry of the Central and the Southern Sagaing fault exhibits a relatively simple rupture behavior, with the rupture interval between ~100 to ~200 years at the central and southern part of the fault.