I woke up early and was flipping to see hurricane Gustav and flipped by the Science Channel, which was showing something on the North Anatolia fault (NAF), the 1999 Izmit earthquake, and the threat from the offshore NAF to Istanbul. I only caught the end of this, but it showed and talked about a fault 15 miles (24 km) south of Istanbul. The GPS-related fault model showed a fault that ran along the southern edge of eastern Marmara Sea. The data collected in the early 2000s show that the main active fault is along northern Marmara Sea, so much closer to Istanbul...the seafloor trace is about 10 km offshore of the western Istanbul coastline, so much closer...maybe 12 or 14 km off of old Istanbul. But, the minarets at the mosques there survived for 100s of years and they at least look fragile.

The question is whether there is a southern fault where shown, and if it is active and slipping fast, and also whether it is strike-slip. There are publications that show this fault, and there were normal slip aftershocks to the 1999 quake along this trend. We collected a dense grid of data between Imrali Island and Armutlu Peninsula in July, with some data relative close to shore farther east. I'm working on processing some of this, including today. I have not interpreted enough of the data, or spent enough time with interpretation, to know anything much about the fault farther east. We'll see if I (and my collaborators) learn enough in the next 2 weeks to put something into an AGU abstract.

HW was co-author on a 2004(?) paper (Polonia et al.) that showed a buried channel offset across the northern fault in Izmit Gulf. The Channel was around 14,000 (?) years old and, given the amount of offset of it, the post-14,000 right-lateral rate was only about half the current GPS rate. (They may have used 12,000 years for the channel age). But, there are other ways to interpret this offset. We probably can't rule out the northern strand having less slip than has been published the last few years.

(There is an additional important strand of the NAF farther south than what I was talking about yet, that runs south of Armutlu Moountain through Lake Iznik and Gemlik Bay. We see this fault system farther west in our new data).
Chris