The Myanmar earthquake on March 28, 2025 was more than a strong tremor recorded by instruments. In just a few dozen seconds it showed how unpredictable the Earth can be, transforming an already known fault into a natural laboratory of extreme phenomena. The new research led by Dara E. Goldberg, a geophysicist at the US Geological Survey, tells of an earthquake capable of challenging the laws we knew, running faster than seismic waves and leaving behind a landscape marked by fractures and failures.
The heart of the story is a rupture almost five hundred kilometers long, a distance that no one would have associated with a 7.7 magnitude earthquake. It is as if the fault suddenly decided not to respect the rules, taking a run and continuing to flow well beyond what was expected. Scientists followed this rush with everything they had: global seismic data, satellite images, ground deformation maps. A web of clues which, put together, show a fracture capable of exceeding three miles per second, entering the very rare category of earthquakes supershear.
A race that overcomes seismic waves
When a fracture proceeds at this speed, the energy no longer disperses as in “normal” earthquakes: it is concentrated in a sort of seismic cone, a shock front that runs on the surface and which can make the shaking much more violent even at great distances. In the case of the Myanmar earthquake, this compressed wave even reached some regions of Thailand. A phenomenon that, until a few years ago, many considered almost impossible on a continental fault.
To understand why this happened, you need to look at the Sagaing Fault through the right lens. Its southern section is unusually straight, devoid of the folds that usually slow fracturing. It is a rare condition, but alone it would not be enough to explain such an extreme event. The other ingredient comes from time: the last major significant rupture in that area dates back to 1839. Two centuries of plates pushing, sliding, accumulating energy, in silence. A spring that no one sees, but remains there to tense.
Then there is the composition of the rocks. The two sides of the fault are made of different materials, with stiffnesses and strengths that suddenly change from one side to the other. This contrast modifies the way in which energy bounces and propagates, favoring a fast fracture, almost undecided whether to slow down or accelerate further. It is the combination of these three conditions – the shape of the fault, the stress accumulated over time and the structure of the rocks – that transforms a natural event into something exceptional.
The result has been seen across the territory: cracked walls, bent streets, entire neighborhoods marked by soil liquefaction, that phenomenon in which the earth loses consistency and behaves like a semi-liquid mass. Without satellite images it would have been almost impossible to reconstruct a complete map of the damage, because many areas were unreachable due to internal conflicts.
The traces collected from above show one thing very clear: the most devastated areas follow the supershear section of the fault step by step. Not a coincidence, but a precise sign of how the speed of the rupture affected the type of destruction.
The lesson that such an anomalous earthquake leaves us
Current seismic hazard models are often based on the idea that the length of a fracture is proportionate to its magnitude. The Myanmar earthquake, however, demonstrates that this equivalence is not always reliable. A fault can run much further than we expect, without needing to reach extreme magnitudes. It is a reminder that concerns many countries: from California to Asian regions crossed by long fault systems, where linear shapes and contrasts between rocks can create similar conditions.
For scientists, this event represents a new reference. An invitation to look not only at the magnitude, but also at the way in which a fault accumulates energy, at its materials, at its geometry. A sort of call to a more careful, more complete seismology, more aware of the complexity with which the Earth moves under our feet.
The study, published in the journal Sciencemarks a turning point and reminds us that earthquakes are not all the same. Some run. Some are surprising. And some forever change the way we read risk maps.
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