STATIC COULOMB STRESS SCENARIOS FOR EARTHQUAKE RUPTURES IN THE EASTERN MARMARA SEA

The 1999 Izmit earthquake (M=7.4) extended the historical progression of large earthquakes along the right-lateral, strike-slip North Anatolian fault into the Sea of Marmara, and to within 100 km of Istanbul, a city of 12 million people. Ambiguous locations of the western termination of the 1999 Izmit, Turkey earthquake rupture and the location of the 1963 Yalova earthquake (M=6.4) add uncertainty to any single prediction of the earthquake-induced stress changes in the eastern Sea of Marmara in northwest Turkey. We use a historical earthquake catalog, mapped Marmara Sea fault traces, and fault slip distributions for the 1999 Izmit earthquake to determine the stress change scenarios that result from six plausible configurations for the western termination of 1999 Izmit earthquake rupture and the location of the 1963 Yalova earthquake. Coulomb stresses calculated using geomechanical models are increased on the Princes’ Island, Cinarcik, and Armutlu fault segments in each case. In four of the six plausible rupture configurations, the Cinarcik fault receives the greatest average stress change. In one other configuration, the average stress increase on the Princes’ Islands fault is greatest. In another, the stress changes on the Cinarcik and Princes’ Islands fault are comparable. Rupture initiating on either the Princes’ Islands or Armutlu faults would be favored to propagate onto the Central Marmara, or Imrali fault, respectively, based on their favorable geometries of the respective fault intersections. Whereas rupture initiating on the Cinarcik fault would be limited to a much shorter rupture based on its mapped western termination. Therefore, while the earthquake-induced stress changes may, in most cases, be greatest on the Cinarcik fault, an earthquake initiating on this fault may produce a shorter cumulative rupture compared to rupture initiation on the two other major eastern Marmara Sea fault segments.