3D Physics‐Based Numerical Simulations of Ground Motion in Istanbul from Earthquakes along the Marmara Segment of the North Anatolian Fault

In this article, the outcomes of a research cooperation between Politecnico di Milano, Italy, and Munich RE, Germany, aiming to improve ground‐motion estimation in the Istanbul area through 3D physics‐based numerical simulations (PBSs), are illustrated. To this end, 66 PBSs were run, considering earthquake scenarios of magnitude ranging from 7 to 7.4 along the North Anatolian fault (NAF; Turkey), offshore Istanbul. The present article focuses on the detailed introduction of the simulated scenarios comprising: (1) the setup of the 3D numerical model, (2) the validation of the model with recordings of a recent earthquake, (3) the PBSs results, (4) a parametric study on the effect of different features of the seismic source, and (5) a comparison with well‐established ground‐motion prediction equations to highlight the main differences resulting from the use of a standard empirical approach as opposed to physics‐based “source‐to‐site” numerical simulations. As a main outcome of this study, we observed as, for magnitude 7 and 7.2, PBSs are in agreement with empirical prediction models whereas, for magnitude 7.4, PBSs provide higher ground‐motion estimates, as a consequence of directivity effects, amplified by the specific geometry of the portion of the NAF facing Istanbul.