USIAS Fellows seminar - Can we predict the next major earthquake in the Marmara Sea?

By Hayrullah Karabulut and Jean Schmittbuhl, USIAS Fellows 2015

The North Anatolian Fault (NAF) poses a significant hazard to the large cities surrounding the Marmara Sea region, and particularly to the megalopolis of Istanbul. Indeed, the NAF is presently hosting a long unruptured segment below the Sea of Marmara. This seismic gap is approximately 150 km long and corresponds to the Main Marmara Fault (MMF) where a large earthquake (M>7) is expected to happen shortly. The last major event in the region was the 1999 M7.6 Izmit earthquake. It was shown recently that this event was actually preceded by a series of small foreshocks, 44 minutes before the main shock, opening new perspectives for a possible forecast of such large events.

Since the 1999 earthquake, which ruptured the eastern segment of the gap, scientists have been involved in the monitoring of the activity of the fault, using a large spectrum of techniques. During the SEISNAF-USIAS project, we analysed the seismicity along the Main Marmara Fault below the Marmara Sea during the period of 2007–2014 to provide new insights on the recent evolution of this important regional seismic gap. We show that seismicity varies strongly along strike and depth providing fine details of the fault behaviour. We also show that a specific region (the Central Basin) behaves differently from the rest of the fault. This region hosts nine long-lasting seismic repeaters that show similarities with the foreshocks of the Izmit earthquake.