An engineering challenge on an active fault
In the rugged terrain of northern Shan State, the Kunlong Bridge is an important transportation link, crossing the powerful Salween River. The modern bridge, a 286-meter-long box girder structure, was completed in 2023 to replace an older, deteriorating suspension bridge built in 1965. This newer bridge, with a load capacity of 75 tonnes, facilitates trade along the Hsenwi-Kunlong-Chinshwehaw road, an important route to China. The bridge's location, however, places it directly over the Nantinghe Fault, a seismically active feature, presenting a significant engineering problem.
Myanmar is a region of high seismic activity, primarily due to the collision between the Indo-Australian and Eurasian tectonic plates. This collision zone is dominated by the Sagaing Fault, a major right-lateral strike-slip fault that runs for over 1,200 kilometers through the country. The Nantinghe Fault is part of this larger, active system. Probabilistic Seismic Hazard Analysis (PSHA) is a method used by engineers and seismologists to estimate the likelihood of certain levels of ground shaking at a given location. For the Kunlong Bridge, PSHA indicates a 10% probability of a magnitude 7 earthquake occurring within 50 years, a standard benchmark used in infrastructure planning. Such an event could generate ground shaking severe enough to exceed the bridge's structural capacity.