On September 10, 1509, a massive earthquake estimated above magnitude 7 struck Constantinople, collapsing over a thousand buildings, breaching sections of the city's ancient walls, and killing thousands. Ottoman chroniclers dubbed it the Kucuk Kiyamet, or Lesser Judgment Day. Sultan Bayezid II mobilized thousands of workers for reconstruction, and the disaster reshaped urban planning in the Ottoman capital for a generation.
In 1509 the ground beneath Constantinople gave way. The earthquake, which modern seismologists place along the North Anatolian Fault beneath the Sea of Marmara and estimate at around magnitude 7, struck a city that had been the Ottoman capital for barely half a century. More than a thousand houses collapsed, along with scores of mosques. Long stretches of the Theodosian land walls and the sea walls cracked or fell, and waves driven up from the Marmara reportedly spilled over the waterfront defenses. Fires broke out among the wreckage, consuming what the shaking had spared. Estimates of the dead range from several thousand to more than ten thousand, and the aftershocks continued for weeks, so frightening residents that many refused to sleep indoors.
Ottoman writers reached for apocalyptic language, calling the disaster the Kucuk Kiyamet, the Lesser Judgment Day. Even the imperial complex offered no refuge. Sultan Bayezid II, whose own mosque had been completed only a few years earlier, abandoned the damaged Topkapi Palace for tents and then withdrew to Edirne while the capital steadied itself. The monumental mosque of his father, Mehmed the Conqueror, was badly damaged, a pointed blow to a dynasty that had staked its prestige on transforming the conquered Byzantine city into a showpiece of Islamic rule.
The rebuilding became one of the largest public works efforts of the era. Bayezid summoned laborers and craftsmen from across the empire, with sources commonly citing tens of thousands of workers, and financed the effort in part through a special levy on households. Crews restored the walls with remarkable speed, and the experience left a lasting mark on how the city was built: officials and builders increasingly favored lighter timber-framed houses, judged better able to flex with the ground, even though that choice would leave Istanbul chronically exposed to the great fires that swept its neighborhoods in the centuries that followed.