The March 28 magnitude 7.7 quake on Myanmar's Sagaing Fault produced a roughly 300-mile (500 km) surface rupture and transferred nearly all deep slip to the surface, according to a study in Nature Communications. Using Sentinel-1 radar and Sentinel-2 optical data, researchers measured ground motion to fractions of an inch despite limited field access. The fault's estimated age (14–28 million years) likely made it smooth and efficient at transmitting energy, producing 10–15 feet (3–4.5 m) of surface offset and highlighting implications for infrastructure resilience against a potential "Big One."
Myanmar's Massive 7.7 Quake Transferred Deep Energy Smoothly to the Surface — Lessons for the 'Big One'
View of the Ava Bridge near Sagaing, Myanmar, which collapsed during the March 2025 magnitude 7.7 earthquake. The bridge was built in 1934 and was the only bridge across the Irrawaddy river for more than 60 years after its construction. | Credit: Wang Yu
A fault that ruptured in Myanmar on March 28 produced an unusually long, efficient surface rupture that transmitted energy from deep underground almost entirely to the surface, researchers report. The magnitude 7.7 earthquake on the Sagaing Fault produced a remarkably smooth, long rupture with major implications for how mature faults can concentrate shaking at the surface.
What Happened
The March 28 quake generated a surface rupture of roughly 300 miles (about 500 kilometers) — far longer than the tens of miles typical for surface-breaking events. The rupture began roughly 6 miles (10 km) beneath the surface and was accompanied by severe shaking that led to more than 5,400 deaths and extensive infrastructure damage.
How Scientists Studied It
Because field surveys were limited by destruction and ongoing armed conflict in the region, researchers relied on satellite observations. They combined optical imagery from the European Space Agency's Sentinel-2 satellites with radar (synthetic aperture radar) data from Sentinel-1 to measure ground motion down to fractions of an inch across the fault zone.
Key Findings
The new study, published Dec. 8 in Nature Communications, found that nearly all of the slip that occurred miles underground reached the surface — meaning there was essentially no "shallow slip deficit." In most earthquakes, some deep displacement is absorbed below the surface; here, the deep slip was transferred almost 100% to surface offset.
"The massive amount of slip that happened miles underground was transferred 100% to the surface," said Eric Lindsey, a geoscientist at the University of New Mexico and the study's first author. "Over millions of years the rough edges and bends in the fault have been ground down. Because it is so smooth and straight, the earthquake rupture could travel very efficiently across a huge distance."
On one side of the Sagaing Fault the ground shifted about 10 to 15 feet (3 to 4.5 meters) relative to the other — a displacement captured in a first-of-its-kind video showing the fault cracking at the surface.
Why the Fault Was So Efficient
Researchers attribute the efficient transfer of deep slip to the Sagaing Fault's maturity. The fault is estimated to be between about 14 million and 28 million years old; over that time its irregularities and bends have been smoothed by repeated movement. A straighter, smoother fault can allow rupture to propagate more continuously from depth to the surface, amplifying surface displacement and shaking.
Implications
The findings matter for earthquake hazard assessment and infrastructure design. A mature, smooth fault may transmit destructive energy to the surface more effectively than a younger, rougher fault — meaning that in regions with long-lived, well-developed faults, earthquakes could produce unexpectedly large surface offsets and intense shaking. Lindsey and colleagues note this has direct implications for preparing for a potential "Big One" in places like the United States, where mature faults may also exist.
Study Source: Lindsey et al., Nature Communications, published Dec. 8.
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