This article is interdisciplinary in nature, relevant to the fields of both earth sciences and historiography, which come together in the investigation of longterm earthquake hazard. Taking here as an example the earthquake of 10 September 1509, which was associated with an inferred 70- +-30-km-long offshore fault break in the Sea of Marmara (MW 7.2 +-0.3) and with widespread damage in Istanbul and the adjacent region, this article emphasizes the need for systematic and consistent analysis of historical earthquake data and sets an example for such a task.

The re-examination of this earthquake, in the context of the long-term seismicity of the region over the last 2000 yr and in comparison with larger historic and modern events in the region, shows no macroseismic, and to some extent, no tectonic evidence that the 1509 earthquake was a catastrophic event. It is one of the damaging shocks in the 17-century-long history of Istanbul, of a magnitude that was smaller than the large events that can occur further east in the Anatolian Fault Zone.

This is consistent with the evidence from seismic reflection surveys in the Sea of Marmara, which shows that faults are generally less continuous offshore than onshore, as well as from the long-term seismicity of the region, which is an implication of the opening up of the Sea of Marmara earthquakes and its association with relatively short faults compared with ruptures of great lengths in the Anatolian Fault Zone further east, which is dominated by strike slip.