GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.2 143 poor before 1999 despite the serious seismic risk for the Istanbul region with a 15 million populations. Starting from the year 2000, ISMAR-CNR in cooperation with a team of Turkish scientists from several institutions have conducted several geological/geophysical surveys in the Sea of Marmara and the NE Aegean, along the submerged part of the NAF (cruise reports available at http://www.ismar.cnr.it/prodotti/reports-campagne) . In the course of these expeditions, several types of marine geological and geophysical data were collected, including multibeam bathymetry, single- and multi-channel seismic reflection profiles, magnetometry, high-resolution CHIRP sub-bottom profiles and bottom imaging with remotely-operated vehicle (ROV). Over 100 gravity and piston cores from key locations of the Sea of Marmara and the NE Aegean Sea were also collected. The main objectives of such studies were to identify and date fault ruptures at the seafloor, define the spatial-temporal distribution and the nature of tectonic deformations in this portion of a major continental strike-slip boundary, and acquire information useful for assessing seismic hazards. Sedimentary and topographic features were analysed in search for piercing lines allowing both to estimate the slip along the fault and to reconstruct the post-glacial paleo-oceanographic history of the Sea of Marmara, including the effects of glacioeustatic/paleoclimatic fluctuations on the water exchange between Marmara and the Black Sea on one side, and the Mediterranean on the other (Çağatay et al. , 1999, 2003, 2009; 2015; McHugh et al. , 2008). The two topics are strongly connected, because a detailed stratigraphy with robust markers like lake/marine transitions, tephra and sapropels, and dated morphological features such as erosional channels, submarine canyons and paleo-shorelines, provides key piercing points for neotectonics and paleoseismology The North-Anatolian Fault System. The NAF, one of the world’s major continental transform systems, separates the Anatolian and the Eurasian plates for more than 1,000 km in northern Turkey. The motion is primarily right-lateral, with a slip rate estimated from GPS geodetic measurements at approximately 24 mm/y (McClusky et al. , 2000). The Sea of Marmara is located near the transition between the right lateral strike-slip regime of the NAF Fig. 1 - Tectonic map of the North-Anatolian Fault (NAF) in the Marmara region. Topographic data are from SRTM database. Bathymetric data are from different sources, including: Le Pichon et al. , (2001); Polonia et al. (2004); Gasperini et al. (2011). Red thick solid lines mark the NAF trace, both in the N and S strands. Position of the faults is from: Sengor et al. (1985); Le Pichon et al. (2001); Armijo et al. (2002); Gasperini et al. (2010; 2011). Geological slip rates obtained by submarine paleoseismological studies (Polonia et al. , 2004; Gasperini et al. , 2011) are also indicated (yellow boxes).