🌍 Exceptional: when all the energy from a mega-earthquake is transmitted to the surface

When an ancient and smooth seismic fault releases all its energy at once, the consequences are spectacular. The magnitude 7.7 earthquake that occurred in Myanmar in March 2025 is a striking example, offering geologists a rare opportunity to study the behavior of the most formidable fault systems. While the majority of earthquakes occur along irregular rupture lines, this one followed an exceptionally straight and uniform path.

This particular configuration made it possible to grasp the energy release mechanisms of a major continental rupture. To conduct their work, scientists benefited from international collaboration. Due to armed conflicts and significant destruction on site, field access was impossible. They therefore relied on satellite observation, an approach that proved to be both effective and highly accurate.


The team used two satellite techniques to collect its data. The first, optical image correlation, studies the displacement of pixels between images taken before and after the event. The second, radar interferometry, allows for extremely precise measurement of changes in distance between the satellite and the ground. Together, these tools made it possible to map deformations over a vast area.

The results revealed a rupture extending for nearly 500 kilometers (about 310 miles), a highly unusual length, accompanied by a lateral ground slip of 3 to 4.5 meters (roughly 10 to 15 feet). This remarkable continuity is explained by the nature of the Sagaing Fault, an ancient and very smooth geological structure, similar to the famous San Andreas Fault in California.

The study also helped solve a long-standing enigma in seismology. Usually, the movement recorded at the surface during an earthquake is much less than that occurring at depth. However, for this event in Myanmar, the observations show no discrepancy: the energy released at depth was transmitted entirely to the surface.

Furthermore, the earthquake linked several fault segments into a single rupture. It thus crossed barriers that were thought capable of stopping its progression. The analysis also shows that areas that had already experienced shaking in the 20th century moved less, while those that had been quiet since the 19th century slipped more. This regularity could be exploited to refine predictions regarding future movements.

What is a 'mature' or ancient seismic fault?

In geology, a fault is described as 'mature' when it has experienced repeated seismic activity over a very long period, often several million years. This turbulent history gives it particular physical characteristics. Through repeated slipping, the two blocks of rock that compose it end up polishing each other.

The asperities, bumps, and bends present during the fault's formation are gradually worn down. The fault plane then becomes extremely smooth and straight over long distances. This simplified geometry has a direct impact on how seismic energy propagates during an earthquake.

On a young and irregular fault, the energy of a rupture can be dissipated or deflected by obstacles. It can also create an elaborate network of small fractures around the main fault. On an ancient fault, the absence of obstacles allows the rupture wave to travel quickly and efficiently over a very great length, without losing too much power.

This transmission efficiency means that the energy accumulated at depth reaches the surface almost without attenuation. The shaking felt near these faults can therefore be more intense and concentrated than predicted by models that did not fully account for this particularity of ancient geological structures.