3D Dynamic Rupture Simulations for the Potential Main Marmara Fault Earthquake in the Sea of Marmara Based on the Inter-Seismic Strain Accumulation

Abstract

The northern strand of the North Anatolian Fault (NAF), the Main Marmara Fault (MMF), poses a significant earthquake risk due to a ∼120 km seismic gap situated between the Mw7.4 1912 Ganos and Mw7.4 1999 İzmit earthquakes. We generate realistic 3D dynamic earthquake rupture scenarios on the MMF, considering the non-planar geometry and heterogeneous initial stress distributions. Initial shear stress distributions are implemented by considering strain accumulation during the interseismic period due to heterogeneous fault coupling and slip rates, and stress release due to past earthquakes constrained from historical earthquake catalogs and turbidity records. A total of 87 rupture scenarios are generated, two of which are designed to test the robustness of our simulations, by considering various possible initial stress distributions and rupture initiation points. Scenarios indicate that Kumburgaz Basin and Princes' Islands (PI) segments are likely to rupture. However, due to possible low coupling and past ruptures, the moment magnitude of the expected earthquake may not exceed Mw7.4. The rupture does not enter into the İzmit Segment (IS) due to its rupture in 1999, but it may propagate to the 1912 rupture zone toward the west due to accumulated strain since then. Peak Ground Velocities (PGV) are calculated assuming that the region's complex 3D velocity structure can be modeled as a homogeneous elastic half-space. With this caveat, high PGV values are estimated for the European coast of İstanbul due to the rupture geometry and possible directivity. This underscores the urgent need for disaster mitigation in these high-risk areas.