The North Anatolian fault on the Hersek Peninsula, Turkey: Its geometry and implications for the 1999 İzmit earthquake rupture propagation

Abstract

The western termination of the 1999 İzmit earthquake still remains as an intriguing problem for researchers and the people residing around the Sea of Marmara. Th ere have been numerous off shore mapping and modeling studies performed in the Gulf of İzmit. However, the main debate about the western termination of the 1999 İzmit surface rupture is linked to the Hersek Peninsula and corresponding fault geometry. We focused our eff orts at resolving the fault geometry on the Hersek Peninsula by applying geological mapping, geomorphic analyses, palaeoseismic trenching and geophysical surveys. Our studies reveal that the North Anatolian Fault forms a restraining stepover and did not experience surface rupture during 1999 İzmit earthquake in the vicinity of Hersek Peninsula. We tested this fault geometry with a fi nite element model in half elastic space and correlated the results successfully with the existing topography. In addition, we ran a simple Coulomb model to explain the possible cause of surface rupture termination at this specifi c location. Our studies, combined with detailed off shore bathymetry data, suggest that the restraining step of the North Anatolian Fault on the Hersek Peninsula is capable of creating an effi cient earthquake rupture barrier. © TÜBİTAK.