The Hagia Sophia is built just about 17 miles from a very active fault line –the Anatolian Faultline., and has experienced over a hundred earthquakes. The dome collapsed two decades later in 558 on May 7 due to an earthquake. Justinian was still alive, and Isidorus the Younger, nephew of Isidore, one of the first architects. Isidorus elevated the dome 30 more feet, using light material, and reinforcing the original structure of the dome. This is the same structure that exists today. It is really as testament to the architectural planning that the church/museum is still largely unscathed after almost 1500 years. It is still standing, and considering the earthquake activity all around it, that is pretty amazing. There s an ongoing effort, however, to reinforce the structure, and to know seismic activity, and to continuously reinforce the exisiting structure of the church so that it may remain unscathed.