Initial reports suggested the city's great monuments had escaped unscathed. But yesterday's thoughts were for the dead and injured, and it will be some time before the city's churches, mosques and palaces can be surveyed for structural damage.
Today Istanbul is a sprawling industrial city. But it has been successively capital of the Christian and Islamic worlds, and its history has left it littered with monuments. They have always stood in peril from the faultline that runs so close to the city, and earthquake engineers regularly visit the main sites to see how they can be protected.
Aya Sofia, for centuries the largest and most important church in the world, has stood for almost a millenium and a half. But it has been severely damaged by earthquakes that have shaken the city in the past, and the hordes of tourists who visit see a building patched up to keep it standing.
The great mosque of Sultan Mehmet the Conqueror, who seized the city for Islam in 1453, ending the eastern Roman Empire, was not so lucky. Not a trace of his mosque survives: it was devastated by one of the major earthquakes that hit the city every century.
The spiritual headquarters of the Orthodox Christian Church escaped damage this time. Its head, Ecumenical Patriarch Bartholomew I, and his staff, were not injured by the earthquake, but like much of Istanbul's buildings, the Phanar, as the headquarters is known, is without electricity or working telephones.
Bartholomew I, Archbishop of Constantinople, New Rome and Ecumenical Patriarch, is the spiritual leader of 300 million Orthodox Christians.
Damage to any of the main sights would be one more blow to Turkey's reeling tourism industry. Among the monuments the engineers will survey when the dust has cleared will be the Blue Mosque, built in the 17th century, and the legendary harem at the Topkapi Palace, home of the Ottoman sultans. The tile-work in some of the rooms is considered to be the finest in Turkey.
The vast ornate underground cisterns that gave ancient Constantinople water will also be top of surveyors' lists.