Spatio-temporal behaviour of continental transform faults: implications from the late Quaternary slip history of the North Anatolian Fault, Turkey

Abstract

The slip history of the North Anatolian Fault (NAF) is constrained by displacement and age data for the last 550 ka. First, I classified all available geological estimates as members of three groups: Model I for the eastern, Model II for the central, and Model III for the western segments where the North Anatolian Shear Zone gradually widens from east to west. The short-term uniform slip solutions yield similar results, 17.5 +4/–3.5 mm/a, 18.9 +3.7/–3.3 mm/a, and 16.9 +1.2/–1.1 mm/a from east to the west. Although these model rates do not show any significant spatial variations among themselves, the correlation with geodetic estimates, ranging between 15 mm/a and 28 mm/a for different sections of the NAF, displays significant discrepancies especially for the central and western segments of the fault. Discrepancies suggest that most strain is accumulated along the NAF, but some portion of it is distributed along secondary structures of the North Anatolian Shear Zone. The deformation rate is constant at least for the last 195 ka, whereas the limited number of data show strain transfer from northern to the southern strand between 195 and 320 ka BP in the Marmara Region when the incremental slip rate decreases to 13.2 +3.1/–2.9 mm/a for the northern strand of the NAF. Considering the possible uncertainties of incremental displacements and their timings, more studies on slip rate are needed at different sites, including major structural elements of the North Anatolian Shear Zone. Although most of the strain is localized along the main displacement zone, the NAF, secondary structures are still capable of generating earthquakes that can hardly reach Mw7.