Probabilistic earthquake hazard assessment for Ankara and its environs

The capital and the second largest city of Turkey, Ankara, is generally considered to be safe in terms of seismic activities and earthquake hazard. However, recent studies and earthquakes experienced in the region showed that Ankara is not indeed seismically safe. As the number of studies on Ankara's seismic hazard increases, the number of scientists who claim that the earthquake hazard in Ankara is higher than expected also increases. However, to date no detailed analysis has been undertaken as to the earthquake hazard facing Ankara. This study has compiled data from the earthquake catalogues available in Turkey and employed the latest knowledge available to produce an Ankara-specific earthquake catalogue. Probabilistic seismic hazard analysis of the unified data was then used to produced peak ground acceleration (PGA) values for 5%, 10%, 20%, and 40% probability of exceedance over a 50-year return period. The PGA values at main rock sites were determined using the most appropriate attenuation relationship. These show an exceedance probability of 10% over a 50-year return period to range from 0.20 g to 0.25 g for the Ankara provincial districts of Ayas, Cankaya, Etimesgut, Sincan, and Yenimahalle; from 0.25 g to 0.30 g for Altindag, Golbasi, Kecioren, and Mamak; and from 0.30 g to 0.35 g for Akyurt, Cubuk, Elmadag, and Kazan.