On 28 March 2025, a magnitude 7.7 earthquake struck Myanmar near Mandalay, the country's second-largest city. It was the strongest seismic event recorded in Myanmar in more than a century, with estimates of 3,600 to 5,350 deaths and more than 11,000 injuries. Homes, transport networks and critical infrastructure were heavily damaged across both urban and rural areas, leaving communities facing years of recovery.
A new study published in Geodesy and Geodynamics provides a detailed look at the fault behavior behind this destructive event. Using satellite-based radar measurements and pixel offset tracking, researchers from China mapped how the ground moved during the earthquake. They found that the surface rupture extended about 500 km along the Sagaing Fault, one of Southeast Asia's most active fault lines. By building a fault slip model, they determined that the earthquake was dominated by horizontal movement, and most of the slip occurred within the upper 12 km of the crust, making it a relatively shallow rupture.
"Notably, the ground at the surface moved up to about 4.6 m. In many similar earthquakes, surface movement is smaller than movement at depth, a pattern known as "shallow slip deficit," says corresponding author Shuai Wang. "But the 2025 earthquake in Myanmar showed no obvious shallow slip deficit, meaning the surface experienced the full extent of the movement, making it a devastating disaster for lives and properties."
The researchers also found that part of the earthquake rupture traveled faster than seismic waves normally move through the crust, a phenomenon scientists call "supershear." A conclusion was reached this conclusion from three clues: very few aftershocks occurred in the fast-rupture zone; low moment-scaled radiated energy than similar earthquakes of the same size; and a simple linear fault geometry with minimal complexity.
"Supershear earthquakes are rare and highly destructive, but they tend to occur on faults that are straight, smooth, and structurally mature, which are the product of many earthquakes that have occurred over time," notes Wang. "Recognizing this behavior helps us better understand why some faults produce particularly damaging earthquakes.When a fault breaks at very high speed without obstruction, most of the energy goes into fracturing the rock rather than producing strong ground shaking."
The team's findings also suggest that the 2025 Myanmar earthquake may have released stress that had built up in a section of the Sagaing Fault where no large earthquake had occurred for a long time.
"Based on seismic moment budget analysis and geodetic slip deficit modeling, we estimated a 104–131‑year recurrence interval for Mw>7 earthquakes on the segments that ruptured in this event, while the northern segment may have a shorter one," adds Wang.
The results could help scientists better understand how mature strike-slip faults behave during large earthquakes, and they provide useful information for assessing earthquake risks in Myanmar and across Southeast Asia.
