Seismotectonics of the southern branch of North Anatolian Fault Zone along Bolu, Bursa, and İzmir cities and Değirmenlik (Milos) island in the Aegean Sea

Abstract

The segment distribution of the northern branch of the North Anatolian Fault Zone (NAFZ) is well determined under the Sea of Marmara by intense seismic reflection studies. However, there is no agreement on the number of branches and their positions in the southern Marmara and western Anatolia, even if the area is not covered by the sea. In this paper, we performed morphotectonic studies with the help of the high-resolution satellite images, seismicity, and focal mechanism solutions of significant earthquakes to determine the segment distribution of the active faults accurately. Thus, the distinction of middle and southern branches of NAFZ in the southern Marmara region is established and the route of southern branch of NAFZ from Bolu to Değirmenlik (Milos) island via Bursa, Balıkesir, and İzmir is documented in detail. Besides, our results demonstrate that the hypotheses of "bend model" and "İzmir-Balıkesir Transfer Zone", which were suggested in previous publications to explain the active fault pattern in southern Marmara and western Anatolia, are not working.