The Sea of Marmara has been in the focus of national and international research groups because of its tectonic setting on the North Anatolian Fault (NAF) and its earthquake risk since the August 17, 1999 Kocaeli earthquake. After the 1912 Mürefte and 1999 Kocaeli earthquakes, the presence of a seismic gap in the Sea of Marmara and its rupture with one or more M>7 earthquake(s) in the near future are now accepted by most authorities. Determination of the NAF segment(s) constituting the seismic gap and the magnitude of the earthquake(s) that could be caused by their rupture are of vital importance for earthquake risk assessment for the Istanbul area specifically and for the Marmara region in general. In particular, it is highly important in this assessment to determine if the very low microseismic activity of the Central High segment south of Çekmece- Silivri is creeping or locked. Within the framework of 15 years of continuous collaboration between Turkish and French research groups, we set up an acoustic ranging geodetic experiment along the Central High segment of NAF and deployed ocean bottom seismometers (OBS) close to the fault during October-November, 2014 onboard R/V Pourquoi Pas. With the
proposed project, the data collected fort he next three years from the seafloor instruments will be anlyzed to determine if the Cetral High segment is creeping or locked.

The NAF monitoring data from the seafloor instruments will be obtained six-monthly using a Turkish vessel and used with the following objectives of:

(1) Evaluating the possibility to measure creep on the Marmara Central High segment by analyzing the data from the in-situ marine acoustic-ranging experiment and from far-field continuous land-based GPS stations,
(2) Acquiring new hydrologic data from sensors that will be deployed in April 2016 and bottom pressure time series to eliminate the effect of the water column on acoustic travel time variability,
(3) Improving the fine-scale distribution of and better characterizing the near-fault seismicity, by integrating the OBS data with land-network data, and
(4) Designing an optimal submarine monitoring observatory to be implemented in the Sea of Marmara. The design will be based on the results from these seismological data integration, geodetic experiments and bottom pressure recordings, and from previous submarine equipment deployments, which mostly focused on fluid emission sites. This collaborative project consists of 4 work packages and involves seven research groups: two from Turkey (ITU and KOERI) and five from France (Ifremer, LDO, CEREGE, ISTERRE, LIENs).

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