Tsunami hazard in the Marmara Sea (Turkey): a numerical approach to discuss active faulting and impact on the Istanbul coastal areas

The westward propagation of the seismic ruptures along the North Anatolian Fault (NAF) during the 20th century has increased the probability that the next rupture will be located offshore, in the Marmara Sea, in the prolongation of the 1999 Izmit earthquake faulting. Historical tsunamis have been evidenced in the Marmara Sea, e.g., those associated with the 1509, May 1766 strong earthquakes that broke submarine parts of the NAF, in the vicinity of Istanbul, and future submarine events are expected to produce tsunamis as well that could be triggered either by submarine coseismic displacements or by landsliding. The assessment of their amplitude and extent of their effects is discussed in this paper through numerical modeling based on both earthquake and landsliding sources. We use a finite difference method that yields the maximum water levels reached in the Mamara Sea and the effects (run-up values) around the coasts of Istanbul, using a set of three nested bathymetric grids with a decreasing cell size to focus on Istanbul