Myanmar earthquake: Experts explain cause of disastrous seismic shocks

Al Arabiya

29-03-2025

Experts have explained the cause of a massive 7.7-magnitude quake which struck northwest of Myanmar on Friday – killing more than 1,000 people in the war-torn country and causing catastrophic damage across the region, including a skyscraper collapse in Thailand and shaking reported from India to the west and China to the east, as well as Cambodia and Laos.
Understanding the tectonic forces
The powerful earthquake, which struck Sagaing at 12:50 p.m. (0650 GMT) on Friday at a shallow depth of 10 kilometers (six miles), was followed minutes later by a powerful 6.7-magnitude aftershock and a dozen smaller tremors. Geologists believe the event was caused by movement along the Sagaing Fault, a major geological feature from Myanmar's coast to its northern border.
Suzan van der Lee, a professor in Earth and Planetary Sciences at Northwestern University, explained: 'The earthquake is a result of the collision of the India tectonic plate with the Eurasia tectonic plate. The Himalayas and the Tibetan Plateau are the most prominent results of this collision, but the eastern side of the India Plate also meets the Eurasia Plate, in Myanmar.'
This 'meeting of plates' in Myanmar is characterized by several faults that accommodate both, the ongoing northwards motion of India concerning Eurasia (Myanmar) and the convergence between the two plates.
The quake caused approximately 5 meters of movement between the sides of the fault — an exceptionally large displacement that triggered violent shaking along the roughly 200-km rupture zone.
Light to moderate shaking was felt throughout most of Myanmar and across borders into Bangladesh, India, China, Laos, and Thailand.
This earthquake was 'quite significant' because events of this magnitude (M7.7) are relatively rare. The USGS (US Geology Survey) reports that only six earthquakes of magnitudes greater than 7 have occurred near this location since 1900. The most recent was a magnitude 7.0 earthquake in January 1990, which caused 32 buildings to collapse. A magnitude 7.9 earthquake had occurred south of Friday's event in February 1912.
The dangerous Sagaing Fault
Judith Hubbard, a Harvard graduate and earthquake scientist, provided further context: 'The fault that ruptured Friday is called the Sagaing Fault, and is a huge strike-slip fault that reaches from the coast in the south to Myanmar's northern border, a distance of almost 1,200 km.'
'This region is extremely complicated from a tectonic perspective. Put very simply, the India Plate is shouldering its way northward as it collides with Eurasia. Along its eastern edge, it is dragging along a sliver-like fragment of continental crust, causing strike-slip faulting on the Sagaing Fault.'
The Sagaing Fault cuts directly through Myanmar's central valley region, with slips along the fault creating chains of low hills and mountains. It has long been considered one of the most dangerous strike-slip faults on Earth because it passes directly by Yangon (the largest city), Nay Pyi Taw (the capital), and — most closely — Mandalay, the second largest city.
GPS measurements and geological studies indicate the Sagaing Fault slips at an average rate of about 20 millimeters per year.
Warning signs and seismic gaps
'As with all great earthquakes on known active faults, this M7.7 earthquake was both completely expected (the location and magnitude), and completely unexpected (the timing),' Hubbard explained. 'However, this event also falls within a special class of earthquakes: ones that have previously been singled out as especially likely to occur. That is because researchers had previously identified a seismic gap — a section of the fault that has not broken during recent centuries — in the general area of today's earthquake.'
Hubbard noted that the seismic gap, stretching along the Meiktila segment from Naypyidaw toward Mandalay, may not have fully ruptured in this earthquake. Instead, the southern termination of the rupture appears to lie about halfway through the Meiktila segment, based on early USGS data.
One concerning aspect of strike-slip earthquakes is that while they relieve stress on the segment of the fault that ruptured, they actually increase stress on neighboring segments and sometimes on other regional faults.
'This is a process that we saw in February 2023 in Turkey, when a M7.8 earthquake triggered a M7.5 earthquake on a neighboring fault nine hours later,' Hubbard said.
The relatively simple, straight trace of the Sagaing Fault may enable especially large earthquakes, as ruptures don't encounter large jumps or jogs that could stop them from growing to significant size.
Rising death toll and devastation
The death toll from the earthquake has jumped to over 1,000, with significantly more people injured, according to Myanmar's ruling junta on Saturday. However, experts warn this figure is likely to increase substantially.
'The situation looks grim: based on the estimated shaking, population densities, and quality of construction, the USGS PAGER (Prompt Assessment of Global Earthquakes for Response) is currently estimating a 22 percent chance that more than 100,000 people have died and a 56 percent chance that more than 10,000 people have died,' Hubbard said.
These early estimates, while uncertain, provide general guidance rather than specific predictions about outcomes. The PAGER system also estimates that about 800,000 people experienced intensity IX shaking (violent), and four million more were subjected to intensity VIII shaking (severe).
Challenges in assessment and response
Accurately assessing the impact of such a large earthquake typically takes considerable time — hours, days, or even weeks — particularly in areas with limited communication, said Hubbard. Myanmar's ongoing armed conflict, following the 2021 military coup, complicates disaster response efforts.
Much of the early reporting has come not from Myanmar itself, but from neighboring Thailand, where hundreds of people reported feeling the tremors. While damage in Thailand is significant, the situation across much of Myanmar is likely far worse.
Building vulnerability and expected damage
A critical question is how Myanmar's buildings responded to the intense ground motion. Most structures in the country lack earthquake-resistant designs, as Myanmar has never implemented effective or widespread seismic building codes.
'An earthquake of this size hasn't happened since most occupied buildings have been constructed, so there isn't a lot of data to go on,' Hubbard noted. 'They do have a lot of wood construction, which on the one hand is less dangerous in terms of collapse hazard, but on the other hand is very likely to sustain heavy damage or allow fires to spread. We can also expect widespread collapse of cultural structures like pagodas, of which many beautiful examples can be found in Sagaing, close to the fault trace.'
'Given the unstable situation in Myanmar, much of the new scientific data will likely be remotely sensed,' Hubbard said. 'It is also likely that we will begin to see satellite imagery of the rupture area in the next couple of days. That imagery will enable direct estimates of the rupture length and slip amount by pixel correlation,' Hubbard added.
Regional impact and international response
A state of emergency has been declared in six regions in Myanmar, including Mandalay, the country's second-largest city, which was close to the epicenter and has suffered massive destruction.
In Thailand, 10 people died in Bangkok, mostly in the collapse of an under-construction skyscraper. Up to 100 construction workers are believed to be trapped in the rubble near Bangkok's sprawling Chatuchak market. A crane collapse at a second construction site prompted city officials to shut down metro and light rail services overnight for safety inspections.
Hundreds of residents in Bangkok slept in parks overnight, either unable to return home or fearful of structural damage to their buildings.
The scale of devastation has prompted Myanmar's military regime to make a rare plea for international assistance. Junta leader Min Aung Hlaing invited 'any country, any organization' to send aid and announced that all routes were open for foreign relief efforts.
Offers of help quickly followed, with India among the first to pledge assistance. US President Donald Trump also confirmed that Washington had 'already spoken' with Myanmar about aid.
The World Health Organization warned that the earthquake posed a major threat to life and health and was preparing to scale up its response.