-thick lining. The tunnel alignment is located in a seismically active region, about to the North Anatolian Fault Zone. To decrease the seismic stresses/strains below the permissible levels, two flexible seismic joints/segments; with displacement limits of ± for shear and ± for extraction/contraction; were innovated, designed specially, localized through geological/geophysical/geotechnical conditions, tested in laboratory; implemented ‘first time’ in TBM tunnelling under similar severe conditions. The design earthquake magnitude was specified as moment magnitude of 7.25 and design of functional and safety evaluation earthquakes have a return period of 500 and 2,500 years, respectively. Seismic joint locations defined during design phase were verified through continuous monitoring of cutterhead torques. The tunnel was excavated and constructed with a diameter Mixshield Slurry TBM exclusively designed and equipped with the latest } disc cutters (35 pieces monoblock disc cutters, all atmospherically changeable and have individual wearing sensor system), 192 piece cutting knives (only 48 atmospherically changeable), special pressurized locks for divers and material and rescue chamber for all shift members. Slurry Treatment Plant (installed power of which de-silts the bentonite slurry used during excavation and regenerates with capacity (approximately equivalent to ) was installed. The utilized TBM ranks first in the world with its cutterhead power, second with its pressure design; and sixth with its excavation area. TBM operation was completed within ± tolerance in 479 calendar days, resulting in an average advance rate of ( for working days) by three crews 24/7. The maximum advance rate was realized at marine sediment zone with . Spent direct time for excavation and ringbuild were around 3,500 and 1,700 hours, respectively. In Trakya formation, 28 dyke zones were excavated with an average frequency of and thicknesses were varying between . Furthermore, 440 disc cutters, 85 scrapers and 475 brushes were replaced by TBM crew and four times hyperbaric maintenance operations (total of 45 days) with specially trained divers (max. under first time in the world) were successfully performed. 15,048 piece -thick precast segments (1,672 rings) with the high performance (average charge passed is 280 Coulomb (1,000 Coulomb limit) were produced and connected to each other by using 30,765 bolts. Each ring consists of nine segments that had an average 28 day cylinder compressive strength of and can resist at least 127 years as a service life against subsea conditions. Only 0.3% of produced segments were found to be deficient due to existence of cracks width more