How did the Myanmar earthquake happen? | Defined

The story to date:

The highly effective earthquake in Myanmar on March 28 had its supply in central Myanmar, about 20 km from Mandalay, the nation’s second-largest metropolis. Mandalay, situated on the east financial institution of the Irrawaddy river, is near some of the seismically lively faults within the area, known as the Sagaing fault, named after a city not removed from Mandalay on the river’s reverse facet. The earthquake of magnitude 7.7 struck round 12:50 pm native time, adopted by a number of robust aftershocks, together with one among magnitude 6.4, which occurred 11 minutes after the most important occasion.

What impact did the earthquakes have?

The quakes had been very devastating: they affected all the area, left hundreds of individuals lifeless, and destroyed many properties. The harm zone prolonged to Bangkok, the capital of neighbouring Thailand, which is about 1,000 km from the earthquake’s epicentre.

Nevertheless, the harm in Bangkok was minimal, confined to the entire collapse of a 33-storey high-rise below building, and inflicting water from a swimming pool on the highest of one other high-rise constructing to overflow. Nevertheless, these incidents got a lot hype due to the town’s place on the worldwide tourism circuit. The outpouring of water from the rooftop pool was on account of seismic seiches — oscillations within the water triggered by the passage of seismic waves by means of the world. Despite the fact that the constructing was situated removed from the earthquake’s supply, slower, long-period seismic waves could cause the highest flooring to sway extra and amplify the seiches, as noticed on this case.

Editorial | Classes from a quake: on the Myanmar earthquake 

The harm prediction fashions of the U.S. Geological Survey estimated that the overall loss of life toll within the area may attain effectively over 10,000. Mandalay itself is residence to over 1.5 million folks and was hit the toughest, with many buildings, together with pagodas, mosques, and bridges, both partially broken or utterly collapsed. A assessment of the harm sample reveals that a lot of the devastation was concentrated within the southern areas of the Sagaing fault as a result of this area is sitting on a thicker pile of alluvium, deposited by the Irrawaddy, which amplifies the seismic vitality, as in comparison with the northern components of the fault. This additionally explains why China’s southwest Yunnan Province, which is north of the fault, escaped earthquake-induced harm. The depth to the supply of the 2025 earthquake on the Sagaing fault was solely 10 km, which is one other contributing issue for the heavy harm and a big felt space (space the place the earthquake’s shaking is felt).

The neighbouring japanese components of India additionally escaped harm as a result of the vitality launched by the earthquake dispersed in a north-south course, following the development of the fault.

Are quakes frequent in South Asia?

South Asia, together with Myanmar, is extremely vulnerable to earthquakes on account of its proximity to the advanced assemblage of a few of the largest tectonic options on earth, together with the Himalayas, the Shillong Plateau, the Southern Indo-Burman Vary, and the Andaman-Nicobar subduction zone. Originating from the collision of the Indian and the Eurasian Plates some 40 million years in the past, the plate boundary in Southeast Asia is an lively tectonic characteristic that generated one of many largest earthquakes in historical past, of magnitude 9.2, and a transcontinental tsunami in 2004.

The tectonic stress accumulating on these plate boundaries is the reason for frequent seismic exercise within the area. The earthquake of 1792 was additionally an incredible ‘megathrust’ earthquake of magnitude 8.5, with its epicentre situated someplace alongside the Arakan coast of Myanmar. This seismic occasion generated a tsunami within the northern Bay of Bengal and brought on widespread soil liquefaction within the Chittagong areas of Bangladesh. The massive thrust fault extends additional north onto the Chittagong-Tripura fold belt, the place a number of average earthquakes proceed to happen. It’s nonetheless not clear whether or not this a part of the deformation entrance can generate future nice earthquakes.

Southeast Asia is a tectonic museum that reveals buildings that host earthquakes of various faulting mechanisms, occurring at depths starting from as shallow as 5 km to 200-400 km. The deeper ones happen within the southern areas nearer to Indonesia or the Indo-Burmese areas within the north, bordering the subduction entrance alongside the Indo-Eurasian plates. The 2025 Mandalay earthquake in Central Myanmar was sourced from throughout the continental a part of the mountain vary. Within the tectonics of mountain constructing, such options develop when sediment piles up and rocks are scraped off from the subducting Indian plate, which get plastered onto the overriding Asian plate.

What’s the geodynamic context of the Sagaing fault?

Due to the advanced interaction of plate motions and the ensuing geodynamics within the japanese margin of the Indian Ocean, the northeast-directed convergence of the India and Eurasia plates takes place in a slanted vogue relatively than taking place head-on. This indirect convergence of the plates causes the general pressure to grow to be partitioned, with a part of the deformation being perpendicular to the plate boundary and the opposite half occurring parallel throughout the interiors. The north-south operating Sagaing fault varieties the tectonic boundary between the Central Myanmar Lowlands and the Indo-Burman Vary. An elongated micro-tectonic block that exists between the Indian plate and the Sagaing fault is usually known as the Burma plate or the Burma sliver. It owes its origin to the pressure partitioning occurring on the subduction entrance.

Research have revealed that this fault, with its subsidiary parallel buildings, accommodates a lot of the strike-slip a part of the indirect convergence, with a slip price of 15-25 mm a yr and an amassed slippage of 100-700 km. The Sagaing fault accommodates about 50-55% of the general plate movement within the area. Not like the vertical motions of fault blocks alongside the frontal a part of the convergence zone, the place one tectonic block is pushed up on the opposite, the motion is horizontal on the Sagaing fault, with the blocks sliding previous one another. The San Andreas fault within the western U.S. is one other such instance. Not like thrust faults, the place earthquakes originate at both shallow or deeper sources, earthquakes on strike-slip faults are virtually all the time shallower (10-15 km).

Labeled as a typical ridge-trench rework fault, the Sagaing fault system runs 1,400 km between the spreading centre below the Andaman Sea within the south to the japanese Himalayan bend within the north. It has an extended historical past of earthquakes. Reasonable and occasional robust earthquakes of magnitudes 7 and above are frequent in central Myanmar, the place six robust quakes of seven.0 magnitude or extra struck between 1930 and 1956 alongside the Sagaing fault or on adjoining buildings. Analyses of historic earthquakes have revealed that about half of the Sagaing fault has ruptured in the previous couple of a long time. Thus, the 2025 earthquake shouldn’t be a shock occasion however part of the earthquakes occurring sequentially on this construction to launch the accumulating stresses from the continuing lively plate interactions.

What does the Mandalay earthquake portend?

Historic information assist the prevalence of an earthquake in 1839, known as the Ava earthquake, that killed greater than 500 folks in central Myanmar. This occasion could have originated on one of many segments of the Sagaing fault with a hypothesised magnitude of seven.8. Equally attention-grabbing is the earthquake of 1927, reportedly felt strongly north of Yangon, Myanmar’s largest metropolis with a present inhabitants of greater than 4 million folks. Information additionally point out that an earthquake occurred in 1946, presumably on the Sagaing fault north of Mandalay and with a magnitude of seven.7, like that of the 2025 temblor.

The historic metropolis of Bagan in Central Myanmar, densely full of spiritual monuments, has additionally been subjected to a number of damaging earthquakes. The most recent one to hit this city was in 2016.

Science helps us perceive the processes behind earthquakes and supplies approximate places of future earthquakes and their potential magnitudes. The Sagaing fault shouldn’t be merely a scientific curiosity: it has a tragic influence on the hundreds of thousands who reside with the stressed fault beneath their toes. Myanmar is struggling to deal with the aftermath of the newest earthquake, with a rising loss of life toll and intensive harm to infrastructure, each difficult by the continuing civil battle.

The 2025 Mandalay earthquake ought to function a warning to India. Because the nation most vulnerable to earthquakes in South Asia, India ought to introduce scientifically examined security measures and procedures to mitigate the influence of earthquakes.

C.P. Rajendran is an adjunct professor on the Nationwide Institute of Superior Research, Bengaluru. This text benefited from the paper by Yu Wang et al., revealed in JGR Strong Earth on March 15, 2014.