Just before 1 p.m. on 28 March 2025 — at 12:50 local time (06:20 UTC) — a magnitude 7.7 earthquake struck central Myanmar, with its epicenter near the city of Sagaing, close to Mandalay, the country’s second-largest city. USGS lists the depth at just 10 km (about 6 miles) — shallow enough that the shaking arrived at the surface with most of its energy intact. It was Myanmar’s strongest earthquake in more than a century, and by the time scientists had mapped it, it had rewritten a record: the longest continental strike-slip rupture ever documented.
The numbers that followed were grim. Reported death tolls climbed for weeks as rescue teams reached cut-off towns; later tallies put the total at more than 5,400 fatalities and more than 11,000 injuries across the region, the great majority in Myanmar. Within Myanmar alone, the AHA Centre count cited in early studies already stood at 3,645 deaths by 8 April 2025, with hundreds still missing — and those were incomplete statistics, gathered in a country in the middle of a civil war. Treat every toll from this earthquake as a floor, not a final count.
The earthquake ruptured the Sagaing Fault, the great north–south strike-slip fault that runs through the heart of Myanmar. Strike-slip means the two sides slide horizontally past each other — in this case right-lateral motion, as the crust west of the fault moved north relative to the east. For the mechanics, see Fault Types Explained. About 11 minutes after the mainshock, a magnitude 6.7 aftershock struck roughly 32 km to the south — the largest of more than 500 aftershocks recorded in the months that followed. On aftershock patterns generally, see Why Aftershocks Happen.
The damage corridor ran through the country’s core: Sagaing, Mandalay and the capital, Nay Pyi Taw, all sat close to the rupture. In Mandalay, multi-story buildings pancaked, a famous bridge over the Irrawaddy — the Ava Bridge — dropped into the river, and fires broke out in damaged neighborhoods. Historic pagodas and monasteries, many built of unreinforced masonry, were badly hit. Then there was the shock felt a thousand kilometers away: in Bangkok, Thailand, a high-rise under construction — the State Audit Office tower — collapsed, killing workers at the site. Bangkok sits on soft river sediments that amplify long-period shaking from distant large earthquakes, which is why a quake centered in another country could do its worst Thai damage there.
One brief clip came to symbolize the event: a security camera near Thazi, south of Mandalay, captured the surface rupture itself arriving — the ground on one side of the fault visibly lurching sideways past the other, in real time, in a matter of seconds.
What makes this earthquake scientifically extraordinary is its length. A USGS-led study published in Science in 2025, working from satellite imagery and seismic data, found that the rupture tore through 475 km (about 295 miles) of the Sagaing Fault — from north of Sagaing southward past Nay Pyi Taw. That is, the study notes, the longest continental strike-slip rupture on record, and roughly 1.6 to 4.7 times longer than standard magnitude-scaling relationships would predict for a magnitude 7.7 event. Surface slip averaged about 3.3 meters and peaked at around 5.6 meters.
South of the epicenter, the rupture also ran fast — at supershear speed, faster than 5 km per second, outrunning the shear waves in the surrounding rock. Supershear ruptures concentrate their energy into a focused front, a kind of sonic boom in the ground, and they tend to keep going: the USGS authors argue that the supershear speed, the fault’s unusually straight and simple geometry, and its moderate slip together explain how the rupture ran so far. The whole process took only about 80 seconds — in that time, a fault segment longer than the distance from Los Angeles to San Francisco broke, and more than six million people were exposed to violent or extreme shaking, in the study’s estimate. The authors call it a modern analog of the 1906 San Francisco earthquake, another atypically long, fast rupture — see San Francisco 1906.
Why it matters beyond Myanmar: the hazard models used worldwide to estimate earthquake risk rely on scaling relationships between magnitude and rupture length. A magnitude 7.7 that behaves like this — rupturing 475 km through three major cities — does not fit those relationships. If supershear strike-slip earthquakes are systematically longer than the models assume, the population exposed to the worst shaking is systematically underestimated too.
The Sagaing Fault is one of Asia’s major plate-boundary structures: it takes up a large share of the sideways motion between the India Plate and the Sunda Plate as India drives northward into Asia. For the bigger picture, see Tectonic Plates Explained. The fault runs more than 1,000 km down Myanmar’s spine, passing close to its biggest cities — Mandalay, Nay Pyi Taw, and, further south, toward Yangon.
By most accounts, the stretch that failed in 2025 had not produced a major earthquake since 1839, when a large quake devastated the royal capital at Inwa (Ava), near modern Mandalay. Seismologists had flagged this quiet central segment as a seismic gap — a locked section between past ruptures, accumulating strain. The 2025 earthquake was, in that sense, the gap closing. Other segments of the fault, including stretches further south offshore and toward the Andaman Sea, did not rupture in 2025 and remain a concern for future earthquakes.
The human catastrophe unfolded inside a humanitarian one. Myanmar has been in civil war since the 2021 military coup, and many of the worst-hit areas were contested or hard to reach. Roads and bridges were cut by ground cracks and collapsed spans; communications failed across the epicentral region; hospitals in Mandalay and Sagaing were themselves damaged and overwhelmed. The ruling military authorities made a rare appeal for international assistance, and foreign rescue teams and aid did arrive — but access, fighting and damaged infrastructure slowed the response in exactly the places the shaking was strongest.
It is one reason the death toll stayed uncertain for so long, and why different sources still give different numbers. This article follows the practice of leading with reported counts and labeling estimates as estimates: more than 5,400 deaths in later overall tallies, against early confirmed counts that were still rising week by week. Damage across the region was estimated in the billions of US dollars.
Three lessons travel. First, length is a hazard in itself: an earthquake does not have to be magnitude 8-plus to put millions of people in the violent-shaking zone if its rupture runs far enough along a populated fault. Second, soft ground far away is not safe ground — Bangkok’s collapsed tower, roughly 1,000 km from the epicenter, is a reminder that basin sediments and tall, flexible buildings can turn a distant quake into local destruction. For how shaking strength is described at a place, as opposed to the earthquake’s size, see Magnitude vs. Intensity. Third, the oldest lesson: buildings of unreinforced masonry and non-ductile concrete along a known fault remain the difference between a great earthquake and a mass-casualty one — in Mandalay as in so many cities before it.
The Sagaing Fault has not gone quiet; it has simply moved its stress elsewhere along its length. The 475 km that broke in about 80 seconds on 28 March 2025 will be studied for decades — as a record rupture, as a warning about the models, and, above all, as the day central Myanmar’s long-quiet fault spoke at full volume.