4. Istanbul, Turkey
Metro area population: 14,377,019
North Anatolian Fault Line, one of the most active faults in the world, passes less than 30 miles from downtown Istanbul. The Princes Islands in the Sea of Marmara, which historically served for the housing of unwanted royalty from Byzantine and Ottoman courts could be a possible epicenter. The islands are part of Istanbul Adalar district and today are a very popular touristic destination.