Why the Myanmar earthquake was so destructive
Summary
Some estimates predict more than 10,000 people died in the quake and that economic losses could exceed the gross domestic product of the already poor country.
The powerful 7.7-magnitude earthquake that struck central Myanmar on Friday was one of the most powerful in the region in years. While the full extent of the damage remains unclear, the United States Geological Survey says it is likely that more than 10,000 people died and that economic losses could exceed the gross domestic product of Myanmar, a poor country engulfed in a bloody civil war. It may take days or weeks before an accurate death toll is established, as many people are buried beneath rubble.
Here is what to know about the science behind the earthquake and why experts fear the damage could be extensive.
What caused the earthquake?
The earthquake in Myanmar was likely caused by “strike-slip faulting," in which tectonic plates—massive slabs of rock on the Earth’s crust that are always slowly moving—brush horizontally past each other. It is different from so-called “subduction" earthquakes, in which one tectonic plate is thrust beneath another.
Scientists believe this quake occurred in the vicinity of a long, straight fault that runs through the middle of the country known as the Sagaing Fault, which some experts have compared to the San Andreas Fault in California.
While Myanmar isn’t in the so-called “Ring of Fire"—a famously seismic arc around the Pacific basin that includes Japan and Indonesia—several plates converge in the country, including the India and Eurasia plates, and earthquakes are common. The USGS says that there have been six other magnitude-7, or larger, earthquakes in the vicinity of the latest one since 1900.
In 1990, an earthquake in the area caused 32 buildings to fall, and dozens were killed by another quake in 1988. But Myanmar had not in recent times suffered a mass-casualty earthquake event on par with some of the world’s biggest earthquake disasters over the past quarter-century.
The magnitude of the latest earthquake, however, is similar to some of the most deadly in recent years. A 7.8-magnitude earthquake that hit parts of Turkey and Syria in 2023 killed more than 55,000 people. A 7.9-magnitude earthquake in China’s Sichuan province in 2008 left around 90,000 people dead, including more than 5,300 children, many of whom were students attending classes.
Why do experts fear a high death toll in the latest earthquake?
Unlike some earthquakes, this one occurred at a relatively shallow depth, only around 6 miles beneath the surface—a similar depth to the 2023 Turkey-Syria quake. Such earthquakes can cause more damage aboveground than ones that occur deep beneath the Earth’s surface.
Another concern: This earthquake was very close to Myanmar’s second-largest city, Mandalay, which has around 1.2 million people. Past major quakes in Myanmar occurred when the country was less developed, with fewer tall buildings. But Mandalay has undergone significant development over the past decade, even though it remains poor compared with other major Asian cities. Experts fear that lax building standards will likely have contributed to the death toll.
“I would expect their infrastructure resistance to strong earthquakes is probably not that good, particularly compared to Japan and California," said Wei Shengji, an earthquake geophysicist at Singapore’s Nanyang Technology University who has studied the Myanmar quake and says he has warned local officials about the possibility of an event like this. “I would expect pretty high levels of damage and casualties."
Adding to the concerns is the relative isolation of Myanmar, which is ruled by a heavily sanctioned military junta. That will complicate the international response and could mean it takes longer for affected people to receive aid and for outside experts to learn the full extent of the damage.
Are further aftershocks likely?
The initial 7.7-magnitude quake struck early Friday afternoon local time, followed by a second 6.7 magnitude quake and some smaller aftershocks. More earthquakes are possible. Although aftershocks are generally smaller than original quakes, they can cause severe damage if buildings have been rendered structurally unsound. Other risks remain, including landslides caused by destabilized soil.
What is being done to get people help?
Even before the latest disaster, nearly 20 million people in Myanmar needed humanitarian aid and more than 3.5 million had been displaced from their homes because of a continuing civil war between rebel groups and the military government, according to the United Nations.
Myanmar’s junta, which has a history of refusing outside help, has declared a state of emergency and taken the rare step of appealing for international aid. China, its neighbor, has dispatched a rescue team, with more help on the way, according to Beijing. President Trump has said the U.S. will also provide assistance. Rescue workers in Mandalay say they lack adequate resources and are listening for the cries of people trapped underground to know where to dig.
Is Myanmar the only country that was affected?
The earthquake was felt more than 600 miles away in Bangkok, the capital of Thailand, where a skyscraper under construction collapsed. Panicked office workers, hotel guests and high-rise condominium residents fled through stairwells as their buildings swayed.
Many people returned to find cracks in their walls and other signs of damage, raising fears that some buildings, roads and other infrastructure in the metropolitan area of 11 million or more could require significant repairs. But Thailand is also far wealthier than Myanmar, giving it more resources to deal with any longer-term damage.
Tremors from the earthquake also caused injuries in China’s Yunnan province, which borders Myanmar, and were felt as far away as Dhaka, the capital of Bangladesh.
Write to Jon Emont at jonathan.emont@wsj.com
