Seismicity of the Sea of Marmara (Turkey) since 1500

We use the earthquake history of the last 500 years to help evaluate the te ctonic and hazard contexts of the 1999 earthquakes at Izmit and Duzce in we stern Turkey. The 20th century has been unusually active, but over the 500 year period the seismic moment release can account for the known right-late ral shear velocity across the Marmara region observed by GPS. Two areas of known late Quaternary faulting stand out as unusually quiet over this perio d: the northwest shore of the Sea of Marmara and the southern branch of the North Anatolian fault system between Bursa and Mudurnu.