This rare earthquake did everything scientists hoped to see

Scientists have long struggled to observe earthquakes that behave in such a clean and predictable way. The Myanmar event stood out because its fault geometry removed many of the complications that typically obscure how seismic energy moves through the Earth.

Investigating the Longstanding Shallow Slip Deficit Mystery

An international research team led by The University of New Mexico focused on understanding how mature faults behave during large earthquakes, with special attention on a debated phenomenon called the "shallow slip deficit." In many earthquakes, surface movement is far smaller than the motion that occurs deep underground. This gap has raised questions about whether some of the energy is absorbed by surrounding rock or simply goes undetected.

By closely analyzing the 2025 Myanmar earthquake, the researchers aimed to determine how energy moves along an ancient, relatively simple fault system and whether deep motion is fully transferred to the surface.

The study, titled "Mature fault mechanics revealed by the highly efficient 2025 Mandalay earthquake," was published in Nature Communications. It was led by UNM Assistant Professor Eric Lindsey, working alongside collaborators from Taiwan and Myanmar.

Studying a Major Earthquake From Space

Because Myanmar is currently affected by armed conflict and the earthquake caused further damage to infrastructure, researchers were unable to quickly conduct on-the-ground investigations. Instead, they turned to satellite-based observations to collect the data needed for their analysis.

"We used two primary satellite technologies: Optical Image Correlation (using Sentinel-2 satellites) to track how pixels in satellite photos moved between two images collected before and after the quake, and Interferometric Synthetic Aperture Radar (InSAR) using Sentinel-1 satellites, which measures the change in distance to the ground from the satellite between two consecutive passes. These tools allowed us to measure ground shifts with incredible precision without setting foot in the danger zone," explained Lindsey.

How InSAR Reveals Ground Movement in Extreme Detail

InSAR functions like a sophisticated version of "spot the difference," using radar signals to detect extremely small changes in the Earth's surface from orbit. As a satellite circles the planet, it sends radar waves toward the ground and records the returning signals.

"By comparing the time it takes for the signal to bounce back to the satellite from each point on the ground, we can detect changes in the ground's elevation or position down to a fraction of an inch. It allows us to map exactly how the Earth warped over an area hundreds of miles wide, day or night, and through clouds," Lindsey said.

This approach allowed the team to reconstruct the earthquake's impact across an enormous region with remarkable accuracy.

A 500-Kilometer Rupture Unlike Most Earthquakes

The rupture caused by the Myanmar earthquake extended for nearly 500 kilometers. To visualize that scale, it is similar to a crack stretching from Albuquerque to Denver, with the ground on either side suddenly sliding past each other by 10 to 15 feet.

"Most earthquakes we study break much shorter fault segments -- perhaps 30 to 60 miles long. It is incredibly rare and scientifically significant to see a rupture that is this long, continuous, and straight," Lindsey said.

Such a long, uninterrupted rupture provided scientists with an exceptional natural experiment.

A Fault System Comparable to California's San Andreas

The earthquake occurred along the Sagaing Fault, which is a strike-slip fault. In this type of fault, the two sides move horizontally past one another, similar to cars scraping by each other on a highway.

"This is just like the San Andreas fault in California," Lindsey said. "We also describe the Sagaing fault as 'mature,' which means it has been slipping in the same way for millions of years. Over that vast time, 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."

This long history of motion has shaped the fault into a structure that allows seismic energy to move with little resistance.

No Missing Energy at the Surface

For decades, researchers have observed that many earthquakes show far less movement at the surface than deep underground, a phenomenon known as the "Shallow Slip Deficit."

"We found that in the 2025 Mandalay earthquake, this deficit was non-existent. The massive amount of slip that happened miles underground was transferred 100% to the surface," Lindsey explained.

This result contrasts sharply with many recent earthquakes where surface motion was reduced because energy was spread across networks of small fractures rather than concentrated on a single fault.

"This shows that on mature, smooth faults, the energy is highly focused and comes right to the surface," Lindsey said. "This is significant because it means the ground shaking near the fault line might be more intense than our current hazard models predict for these types of faults."

How One Earthquake Linked Multiple Fault Segments

The research also revealed that the rupture was able to connect several fault sections into one continuous 500-km event, passing through boundaries that scientists previously believed might halt an earthquake.

"We found that the fault followed a historical pattern: it slipped less in areas that had experienced earthquakes in the 20th century and slipped the most in areas that hadn't broken since the 1800s," Lindsey said. This behavior is known as "slip predictability" and suggests scientists may be able to estimate how much movement could occur on fault segments that have not yet ruptured.

Such insights could improve long-term earthquake forecasting and preparedness efforts.

Why Satellite Science Matters for Global Safety

The study demonstrates the growing power of satellite-based observation. Even in a conflict zone where traditional fieldwork was not possible, researchers were able to produce one of the most detailed analyses of earthquake mechanics to date.

"It's a testament to how global scientific collaboration and open data access (like the Copernicus Sentinel missions) can help us understand natural hazards that affect millions of people," Lindsey said. "The significance lies in safety. This earthquake showed us that mature faults can be much more efficient at transmitting energy to the surface than younger ones, which has direct implications for how we build infrastructure to withstand the 'Big One' in the United States."

Applying These Methods Closer to Home

Lindsey noted that New Mexico sits on a very different fault system known as the Rio Grande Rift, which is pulling apart inside of sliding sideways.

"The remote sensing techniques we refined in this paper are the exact same methods we can use to monitor safety issues close to home," he explained.

By using InSAR to track land subsidence caused by aquifer depletion in New Mexico, as well as slow ground movement related to the rift and deep magma body inflation beneath Socorro, researchers can help state officials better plan for future risks.

"Understanding the physics of 'mature' faults helps us understand the general mechanics of the earth's crust, which improves earthquake hazard models globally," Lindsey concluded.