Myanmar Earthquake Rupture Moved at Supersonic Speed

The magnitude 7.7 earthquake in Myanmar on March 28, 2025, involved a fast-moving rupture along the Sagaing Fault, according to a new study.

The earthquake also caused building damage and ground failure across a wide stretch of central Myanmar.

A section of the fault broke into supershear, with the rupture outrunning the shear waves moving through the rock. This exceptional speed helps explain why this quake stands out among modern continental events.

The study was led by Dara E. Goldberg,a research geophysicist at the U.S.Geological Survey (USGS) Earthquake Hazards Program.

Her research focuses on rapid earthquake characterization so that scientists can better estimate shaking and hazards from major faults.

Tracking an ultrafast rupture

The Mandalay rupture extended roughly 300 miles, about 475 kilometers, along the Sagaing fault. That distance is more than twice what standard magnitude scaling rules predict for a quake of that size.

To determine how fast the rupture moved, the team combined global seismic records with satellite measurements of ground motion and damage. These data allowed them to track the slip second by second along the full path of the rupture.

The models indicate that southern segments moved faster than three miles per second, a clear sign of supershear motion. They also identified a Rayleigh Mach wave,a concentrated surface wave launched by that ultrafast rupture,passing through parts of Thailand.

Seismologists now consider Mandalay and the 1906 San Francisco quake as members of a small class of rare, very long continental ruptures.

These case studies provide expectations for how similar faults might behave in heavily populated regions in the future.

How the rupture raced ahead

Most earthquakes send out seismic shear-waves, side-to-side vibrations that carry much of the damaging ground motion. The rupture itself, the slipping crack on the fault, usually travels more slowly than those waves.

In supershear events, the crack speed overtakes the shear waves, causing energy to pile up along a narrow cone ahead of the rupture.

A USGS analysis shows that this beaming can raise shaking at some distances while reducing it right beside the fault.

In Myanmar,the fast-moving portion of the rupture remained on a long southern stretch rather of quickly dropping back to slower speeds.

That sustained behaviour extended the zone of especially intense shaking beyond what standard models would have forecast for such an event.

For engineers and planners, that means distance from the fault is not