Myanmar's devastating quake could reshape how California and other fault zones gauge future risk

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A devastating earthquake in Myanmar is giving scientists new insight into how major quakes start, spread, and grow. The findings could improve risk estimates for dangerous faults around the world. A new study, published in the journal Science and led by researchers at the USC Dornsife College of Letters, Arts and Sciences, finds that faults that appear structurally simple can produce surprisingly complex earthquakes.

The research focuses on the magnitude 7.7 quake that struck near Mandalay, Myanmar, in March 2025, killing more than 3,600 people and causing damage estimated at up to 14% of the country's economy.

It also puzzled scientists.

The Sagaing Fault, where the quake occurred, is long and relatively smooth, without the sharp bends or major branches that often help explain why a rupture stops in one place and spreads in another.

"The Sagaing Fault looks relatively simple, but this earthquake ruptured across multiple sections of it," said Sylvain Barbot, professor of Earth sciences at USC Dornsife and senior researcher on the study. "That raises an important question: What controls how large earthquakes grow?"

Study rattles long-held earthquake assumptions

To investigate, the scientists used satellite radar data to map how the ground shifted during the quake. They then combined those observations with computer models that simulate how stress builds up and releases along faults over hundreds to thousands of years. The rupture stretched about 450 kilometers—roughly the distance from Los Angeles to San Francisco.

The analysis pointed to an important driver of earthquake behavior: Different parts of a fault don't move at the same rate. Over time, even modest differences—sometimes just 10% to 20%—can build uneven stress along the fault, influencing where earthquakes start, how far they spread, and whether they remain confined or jump into neighboring segments.

"Even on a relatively straight fault, small differences in how nearby sections move over time can influence whether a rupture remains contained or grows into something much larger," said Mingqi Liu, the study's corresponding author, who conducted the research as a postdoctoral scholar at USC Dornsife and is now at ENS Paris.

In the researchers' simulations, those differences caused ruptures to break into segments or, in some cases, to jump from one segment to another. That may help explain why the 2025 Myanmar quake didn't stop where scientists might have expected.

The findings also challenge the long-standing seismic gap hypothesis, which holds that a stretch of fault that hasn't ruptured in a long time may be due for a major quake.

But in Myanmar, the rupture appears to have started outside a known seismic gap, then continued through it and beyond.

"Seismic gaps can tell you where stress might be building," Liu said. "But they don't necessarily tell you where a quake will start—or how far it will go."

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New earthquake insights matter beyond Myanmar

Many major faults around the world—including California's San Andreas Fault and New Zealand's Alpine Fault—are relatively simple in shape. If long-term differences in motion can influence earthquake behavior on the Sagaing Fault, similar processes may be at work on other major faults, as well.

That broader relevance is where the research may have practical value. "We're getting to a point where we can start making more meaningful assessments of seismic hazard," Barbot said. "The same kind of modeling could be applied to places like California or Turkey to better understand what future earthquakes might look like."

The findings suggest that scientists need to look beyond a fault's visible structure and pay closer attention to how it moves over time.

The researchers emphasize that earthquake modeling remains inherently challenging. Their simulations rely on some simplifying assumptions, and certain properties of real faults still can't be measured directly.

Even so, Barbot says the models reproduced the main features of the rupture and offer a useful framework for understanding how large earthquakes can grow.

Despite its limitations, the study highlights a broader shift in how scientists think about earthquake hazard. Rather than asking only where a fault might break, researchers are increasingly examining how the entire fault system evolves over time—and how past earthquakes leave behind stress patterns that shape the next one.

"Earthquakes have a kind of memory," Liu said. "What happened before influences what happens next."

Combining satellite data, geological records, and advanced simulations may enable scientists to build better quake risk estimates for major faults and give communities clearer information about the hazards they face.

Publication details

Mingqi Liu, Dynamic segmentation of the Sagaing fault, Science (2026). DOI: 10.1126/science.ady3237. www.science.org/doi/10.1126/science.ady3237

Journal information: Science

Key concepts

faulttectonophysicsfaulting (geologic)

Provided by University of Southern California