A plain of seismic survivors
On August 24, 2016, a magnitude 6.8 earthquake struck central Myanmar, with its epicenter just south of the Bagan Archaeological Zone. This plain, covering 42 square kilometers, holds one of the world's densest concentrations of Buddhist temples, with more than 2,200 structures dating from the 10th to the 14th centuries. The seismic event caused significant damage, with initial assessments indicating that nearly 400 monuments were affected. spires crumbled and walls cracked. Yet, considering the earthquake's strength and the age of the buildings, a remarkable number of temples withstood the shaking.
This resilience is not accidental. It is the result of sophisticated engineering techniques developed by the masons of the Bagan Empire. Analysis after the 2016 quake, and a previous one in 1975, showed that original, undisturbed structures often performed better than those that had undergone modern reconstructions. The newer materials and rigid construction methods used in 20th-century repairs proved less effective than the ancient designs. Investigators found that poorly bonded connections between original masonry and modern additions were a primary cause of failure; the reconstructed tops of some temples detached and collapsed onto the ancient structures below.
The engineering of ancient brick
The secret to the stupas' longevity lies in their construction. The builders of Bagan perfected a form of masonry that allows for a degree of flexibility. Instead of using a strong, binding mortar, many temples were built with bricks laid with extreme precision, often using a thin clay slurry or sometimes plant-based adhesives. This method, combined with expert bricklaying, created a structure that could shift and resettle during seismic activity without catastrophic failure.
An important architectural feature is the use of vaulted arches and massive, solid cores. In many larger temples, wedge-shaped bricks, or voussoirs, form arches that distribute weight without the need for internal beams. These arches channel compressive forces down into the thick walls and foundations. Stones shaped like a carpenter's square were sometimes inserted at corners to add strength. The immense volume and weight of the solid brick stupas give them a low center of gravity, providing stability. When shaken, the thousands of individual bricks can minutely shift and rub against each other, dissipating the energy of seismic waves in a way a rigid, monolithic structure cannot. Post-earthquake analysis now involves advanced technology, including LiDAR laser scanning and drones, to create detailed 3D models that help conservators understand these ancient structural systems.