The off-fault deformation on the North Anatolian Fault zone and assessment of slip rate from carbonate veins

Discrepancies in earthquake characteristics between geodetically determined and geologically observed slip rates are prominent for the eastern part of the North Anatolian Fault (NAF) zone. We investigated the spatial distribution of deformation across a NAF fault segment near Erzincan, NE Turkey, through field observations of physiographic features along the principle fault and a carbonate-filled fissure system. We propose that distributed deformation across the principal fault in a stretching zone caused sigmoidal simple-shear rotation of the carbonate-filled fissure system. Displacement data of that sigmoidal fissure using isotopic age data of the carbonate fill indicates an off-fault deformation rate of 15.90 +/- 3.19 mm per year for the Holocene, which corresponds to at least 50% of the geodetically estimated annual slip across the fault. It is critical to take the distributed deformation into account for determining earthquake characteristics of active fault systems.