Slip partitioning between subparallel strands of the North Anatolian Fault in the Marmara Region

Abstract

SUMMARY Marmara Region hosts a substantial part of the inhabitants in Turkey, more than 30 per cent of the total population in the cities of Istanbul, Bursa and Kocaeli. This region has experienced several large earthquakes in the past and is still under threat of destructive earthquakes in the future. There, subparallel strands of the North Anatolian Fault (NAF) expand into the region, distributing the earthquake hazards across the whole region. Thus, it is a key issue to investigate how the tectonic process is distributed between these subparallel strands to discriminate their individual earthquake hazards. In this context, we used GPS slip rates to quantify the slip partitioning of the subparallel strands of the fault system. In addition to available slip rates compiled by Bulut et al. and Kreemer et al., we analysed 71 GPS sites (51 continuous and 20 campaign-based) to intensify the GPS network in the region. GPS observations reveal 81.7, 7.7 and 10.7 per cent slip ratios for northern, middle and southern strands. These ratios are also verified by the time series analysis of continuous GPS stations, leading us to the conclusion that the northern strand of the NAF hosts substantially shorter recurrence periods and, therefore, in the long term, the highest earthquake hazard in the Marmara Region.