The story so far:
The powerful earthquake in Myanmar on March 28 had its source in central Myanmar, about 20 km from Mandalay, the country’s second-largest city. Mandalay, located on the east bank of the Irrawaddy river, is close to one of the most seismically active faults in the region, called the Sagaing fault, named after a town not far from Mandalay on the river’s opposite side. The earthquake of magnitude 7.7 struck around 12:50 pm local time, followed by several strong aftershocks, including one of magnitude 6.4, which occurred 11 minutes after the major event.
What effect did the earthquakes have?
The quakes were very devastating: they affected the entire region, left thousands of people dead, and destroyed many homes. The damage zone extended to Bangkok, the capital of neighbouring Thailand, which is about 1,000 km from the earthquake’s epicentre.
However, the damage in Bangkok was minimal, confined to the complete collapse of a 33-storey high-rise under construction, and causing water from a swimming pool on the top of another high-rise building to overflow. However, these incidents were given much hype because of the city’s place on the global tourism circuit. The outpouring of water from the rooftop pool was due to seismic seiches — oscillations in the water triggered by the passage of seismic waves through the area. Even though the building was located far from the earthquake’s source, slower, long-period seismic waves can cause the top floors to sway more and amplify the seiches, as observed in this case.
Editorial | Lessons from a quake: on the Myanmar earthquake
The damage prediction models of the U.S. Geological Survey estimated that the total death toll in the region could reach well over 10,000. Mandalay itself is home to over 1.5 million people and was hit the hardest, with many buildings, including pagodas, mosques, and bridges, either partially damaged or completely collapsed. A review of the damage pattern reveals that much of the devastation was concentrated in the southern areas of the Sagaing fault because this region is sitting on a thicker pile of alluvium, deposited by the Irrawaddy, which amplifies the seismic energy, as compared to the northern parts of the fault. This also explains why China’s southwest Yunnan Province, which is north of the fault, escaped earthquake-induced damage. The depth to the source of the 2025 earthquake on the Sagaing fault was only 10 km, which is another contributing factor for the heavy damage and a large felt area (area where the earthquake’s shaking is felt).
The neighbouring eastern parts of India also escaped damage because the energy released by the earthquake dispersed in a north-south direction, following the trend of the fault.
Are quakes common in South Asia?
South Asia, including Myanmar, is highly prone to earthquakes due to its proximity to the complex assemblage of some of the largest tectonic features on earth, including the Himalayas, the Shillong Plateau, the Southern Indo-Burman Range, and the Andaman-Nicobar subduction zone. Originating from the collision of the Indian and the Eurasian Plates some 40 million years ago, the plate boundary in Southeast Asia is an active tectonic feature that generated one of the largest earthquakes in history, of magnitude 9.2, and a transcontinental tsunami in 2004.
The tectonic stress accumulating on these plate boundaries is the cause of frequent seismic activity in the region. The earthquake of 1792 was also a great ‘megathrust’ earthquake of magnitude 8.5, with its epicentre located somewhere along the Arakan coast of Myanmar. This seismic event generated a tsunami in the northern Bay of Bengal and caused widespread soil liquefaction in the Chittagong areas of Bangladesh. The large thrust fault extends further north onto the Chittagong-Tripura fold belt, where several moderate earthquakes continue to occur. It is still not clear whether this part of the deformation front can generate future great earthquakes.
Southeast Asia is a tectonic museum that exhibits structures that host earthquakes of varying faulting mechanisms, occurring at depths ranging from as shallow as 5 km to 200-400 km. The deeper ones occur in the southern regions closer to Indonesia or the Indo-Burmese regions in the north, bordering the subduction front along the Indo-Eurasian plates. The 2025 Mandalay earthquake in Central Myanmar was sourced from within the continental part of the mountain range. In the tectonics of mountain building, such features develop when sediment piles up and rocks are scraped off from the subducting Indian plate, which get plastered onto the overriding Asian plate.
What is the geodynamic context of the Sagaing fault?
Because of the complex interplay of plate motions and the resulting geodynamics in the eastern margin of the Indian Ocean, the northeast-directed convergence of the India and Eurasia plates takes place in a slanted fashion rather than happening head-on. This oblique convergence of the plates causes the overall strain to become partitioned, with part of the deformation being perpendicular to the plate boundary and the other part occurring parallel within the interiors. The north-south running Sagaing fault forms the tectonic boundary between the Central Myanmar Lowlands and the Indo-Burman Range. An elongated micro-tectonic block that exists between the Indian plate and the Sagaing fault is commonly called the Burma plate or the Burma sliver. It owes its origin to the strain partitioning occurring at the subduction front.
Studies have revealed that this fault, with its subsidiary parallel structures, accommodates much of the strike-slip part of the oblique convergence, with a slip rate of 15-25 mm a year and an accumulated slippage of 100-700 km. The Sagaing fault accommodates about 50-55% of the overall plate motion in the region. Unlike the vertical motions of fault blocks along the frontal part of the convergence zone, where one tectonic block is pushed up on the other, the movement is horizontal on the Sagaing fault, with the blocks sliding past each other. The San Andreas fault in the western U.S. is another such example. Unlike thrust faults, where earthquakes originate at either shallow or deeper sources, earthquakes on strike-slip faults are almost always shallower (10-15 km).
Classified as a typical ridge-trench transform fault, the Sagaing fault system runs 1,400 km between the spreading centre under the Andaman Sea in the south to the eastern Himalayan bend in the north. It has a long history of earthquakes. Moderate and occasional strong earthquakes of magnitudes 7 and above are common in central Myanmar, where six strong quakes of 7.0 magnitude or more struck between 1930 and 1956 along the Sagaing fault or on adjacent structures. Analyses of historical earthquakes have revealed that about half of the Sagaing fault has ruptured in the last few decades. Thus, the 2025 earthquake is not a surprise event but a part of the earthquakes occurring sequentially on this structure to release the accumulating stresses from the ongoing active plate interactions.
What does the Mandalay earthquake portend?
Historical records support the occurrence of an earthquake in 1839, called the Ava earthquake, that killed more than 500 people in central Myanmar. This event may have originated on one of the segments of the Sagaing fault with a hypothesised magnitude of 7.8. Equally interesting is the earthquake of 1927, reportedly felt strongly north of Yangon, Myanmar’s largest city with a current population of more than four million people. Records also indicate that an earthquake occurred in 1946, possibly on the Sagaing fault north of Mandalay and with a magnitude of 7.7, like that of the 2025 temblor.
The historic city of Bagan in Central Myanmar, densely packed with religious monuments, has also been subjected to several damaging earthquakes. The latest one to hit this town was in 2016.
Science helps us understand the processes behind earthquakes and provides approximate locations of future earthquakes and their possible magnitudes. The Sagaing fault is not merely a scientific curiosity: it has a tragic impact on the millions who live with the restless fault beneath their feet. Myanmar is struggling to cope with the aftermath of the latest earthquake, with a rising death toll and extensive damage to infrastructure, both complicated by the ongoing civil war.
The 2025 Mandalay earthquake should serve as a warning to India. As the country most prone to earthquakes in South Asia, India should introduce scientifically tested safety measures and procedures to mitigate the impact of earthquakes.
C.P. Rajendran is an adjunct professor at the National Institute of Advanced Studies, Bengaluru. This article benefited from the paper by Yu Wang et al., published in JGR Solid Earth on March 15, 2014.
Published – April 03, 2025 08:30 am IST
