Izmit is about 70 miles east of Istanbul just across the sea of Marmara and stands on the North Anatolian fault line, although many major earthquakes have occurred along this fault line Istanbul has been more or less unaffected.
I experienced the 1967 earthquake as I was in Istanbul at the time and there was a lot of talk of the big one that was going to destroy the city, and they have been talking about it ever since, but Istanbul is still standing, as it has for the last two thousand years, nuff said.