Tehran – Sagar’s mistakes passing through Mandalay near Mandalay in Myanmar have a long history of destructive earthquakes. In 1946, a similar M7.7 earthquake to the 2025 earthquake, the northern part of the Sagar fault burst near Mandalay, causing extensive damage.
The 1931 M7.5 earthquake ruptured the Sagar Fault in the south near Yangon. The 1956 M7.0 earthquake and the 2012 M6.9 event occurred in the central and southern part of the fault.
The rupture of the SAGAING failure segment is divided into segments with different return periods. Paleoteric studies show that the southern segment (near Yangon) had a revenue period of 100-150 years at the M7+ event, and the central Métira segment (which burst at 28-3-2025) exhibited a seismic gap of 260 km that could generate an M7.9 earthquake.
Fault slip rates of 18-49 mm/year cause stress release, which usually produces M7+ earthquakes every 50-150 years, depending on the location of the fault.
The 2025 earthquake caused pent-up stress in the Meiktila section, which had not burst since the 1839 earthquake with an estimated magnitude of 7.9.
The cities of Mandalay and Nepidau are built on soft soils that are prone to liquefaction and face severe shaking and collapse of infrastructure. The MW 7.7 magnitude earthquake that struck Myanmar on March 28, 2025 caused major damage in Bangkok, Thailand, about 1,000 kilometers from the epicenter.
This unusual effect can be attributed to a combination of geological, structural and seismic factors. The main earthquake that struck Myanmar and Thailand occurred on March 28, 2025 at 1:30pm local time in Myanmar.
The earthquake near Mandalay, Myanmar’s second largest city, was 10km deep and followed by magnitude 6.4 aftershocks and other aftershocks the next day aftershocks, 11 minutes later.
Early estimates suggest that around 800,000 Myanmar experienced strong tremor measuring 9 on the Richter scale, while Bangkok was shaken by moderate tremors of 5-6 on the Richter scale. However, the amplification effect of Bangkok turned moderate tremors into catastrophic shaking for certain tall structures. Experts have previously warned that around eight earthquakes at the Saginaw Fault could destroy Bangkok.
The rupture of seismic faults had a rare “saffair” seismic mechanism (the rupture velocity was greater than the seismic velocity), resulting in long-term shaking and directed more energy towards 1,000 km of Bangkok.
This type of movement is especially important because tall buildings cause damage and create a whiplash effect. This local reinforcement is a feature of construction sites that have a significant impact on areas with soft sediment, even on long distances of major earthquakes.
A similar phenomenon was observed in the Mexican city earthquake (330 km away) in Michoacán on September 19, 1985.
The earthquake caused great damage to tall buildings in Bangkok. The unfinished 33-storey skyscraper in the Chatuchak 159 area suffered the most devastating collapse. The 33-storey civil servant, built by China Railway Construction Corporation for the Thai Audit Bureau, was built near the Chatuchak market and collapsed, killing 14 people and locking in more than 378 people.
The soft sea clay of Bangkok amplified the tremors three or four times, affecting the imperfect frames of the building. The unfinished building had no shear walls. It was a damper. Witnesses report that the collapse occurred within two minutes of the earthquake, indicating how fast-shaking shaking affects unengineered structures.
The overflow of the swimming pool on the roof of some skyscrapers caused water to flow down the roof. A social media video saw waves of water flowing through the building.
An old building in central Bangkok had cracks, broken windows and debris fallen. For example, the pool area of a luxury hotel has been damaged, and the mall roof has been partially collapsed. Buildings built before 2007, before the Thai earthquake code was updated, did not fall short of earthquake-resistant features such as reinforced concrete frames and deep foundations.
Many of these old residential complexes and office towers suffered from cracking and partial collapse. The rapid urbanization of Bangkok has resulted in a surge in skyscrapers on unstable ground. Older structures, including pagodas and apartment buildings, suffered small cracks and collapses, but new buildings that did not follow the updated code were heavily damaged.
Buildings with 10-20 stories are particularly affected by the strengthening of high-frequency seismic waves with soft soil, leading to long-term vibrations and stress in the joints.
The underground of Bangkok is characterized by soft marine soil layers up to 15 meters thick, amplifying long-term seismic waves. These waves coincided with shallow non-slip earthquakes in sagging faults that occurred during the natural period of tall buildings of 10-30 stories in Bangkok and caused serious shaking and structural damage.
This phenomenon known as the site effect allows seismic energy to travel efficiently over long distances, disproportionately affecting tall structures. This amplified the city’s thick marine clay, turning the medium shaking into destructive forces due to its tall structure.
Meanwhile, many buildings are constructed using hard concrete designs that are inappropriate for lateral forces, with only 10% of Bangkok buildings meeting current seismic standards. They are consistent with putting thousands of people at high risk in a future earthquake.
It is possible that there was a directional effect on the antislip mechanism of supersea rupture (faster than shear wave velocity) and sagging faults during earthquakes. The southeastern rupture towards Thailand increased the intensity of the long-term waves reaching Bangkok. In this way, the rupture at the top caused strong ground movement in the direction of the extension of the fault fracture rate.
However, the directional effect decreases with normal distance, with its contribution being smaller at 1000 km compared to near field. The main driver of Bangkok’s damage appears to have been the amplification of waves by soft soil.
Tall buildings (10-30 stories) have a natural vibration period of 1-5 seconds, which is consistent with long-term seismic waves (low frequency waves) produced by large distant earthquakes. Over long distances (over 1000 km), waves travel efficiently through the crust without loss of energy.
The soft clay ponds in Bangkok behave like jelly bowls and shake violently during earthquakes near these clay layers. It creates a “whiplash” vibrational motion that resonates with tall buildings and emphasizes the joints, beams and foundations of the structure. A shallow foundation built on soft clay cannot hold the building firmly during long-term, sustained shaking.
The skyscrapers act like inverted pendulums in this environment, causing the upper floors to sway violently, even when ground movement is visible.
Major earthquakes produce complex ground movements (such as high-frequency shaking and severe high-partum movements). The movement of tall buildings is particularly sensitive to long-term waves and can be amplified by natural oscillation periods.
Soft soil (common in river basins such as Mandalay) amplifies shaking, liquefies and destabilizes the foundation of the building. Sagging fault destruction caused liquefaction and worsened structural damage.
The collapse of the Bangkok skyscraper 1,000 km from the epicenter on March 28, 2025 was due to the earthquake domination of long-term waves and amplification of site conditions.
Asymmetrical building designs or uneven mass distributions create torsional forces and increase stress on columns and connections.
As they shake, adjacent structures of various heights or dynamic properties collide with each other. In Myanmar, glass breakage and falling debris caused considerable urban casualties.
Weak concrete (common in developing countries such as Myanmar) cracks under circulating loads, leading to sudden collapse. Older buildings rarely adhere to modern earthquake codes. Remodeling historical structures (for example, Mandalay Palace) without compromising cultural heritage is complicated and expensive.
A cluster of tall buildings creates “city valleys” that amplify ground movement during earthquakes through reflections of waves due to topographical effects. Rooftop pools, glass facades and heavy HVAC systems add unnecessary weight and increase stress on structures while shaking.
Thailand has historically been considered a low to medium seismic zone, which has led to poor seismic conservatism in its design. In Bangkok, engineers focus on wind loads, not necessarily earthquakes.
The directness of the Sagaing fault rupture probably sent more energy southeastward towards Bangkok.
Bangkok’s skyscrapers have been uniquely vulnerable to distant earthquakes due to the strengthening of long-term waves, coupled with decades of unsustainable development and low construction standards.
Unlike short buildings that are susceptible to high-frequency, short-period shaking, they are designed to catastrophically strengthen the shaking of high-rise buildings when high-rise waves hit soft soil and low-period shaking of soft soil. Even 1,000 km away destroyed in Bangkok, the event added new lessons to seismic engineering lessons in the New World.
The National Disaster Management Committee has declared states of emergency in six regions: Naypyidaw, Sagaing, Mandalay, Bago, Shan and Magway.
Military-led rescue teams prioritized urban areas such as Mandalay and Nepidau, where infrastructure damage is severe. Patients were treated in parking lots as hospitals in Mandalay and Nepidau were destroyed and emergency departments collapsed. Naypyidaw General Hospital reported 20 deaths in the first few hours after the event, and major hospitals in Mandalay were short of medical supplies.