Rupture Characteristics of the 1912 Mürefte (Ganos) Earthquake Segment of the North Anatolian Fault (Western Turkey)

The Ganos fault is the westernmost segment of the North Anatolian Fault (NAF) that generated the 9 August 1912 Mürefte (Ganos) earthquake (MW=7.4). We study the 1912 earthquake characteristics using coseismic fault slip and fault segmentation coupled with the analysis of historical seismic records. Surface ruptures with small releasing and restraining structures and 1.5 to 5.5 m right-lateral offsets have been measured at 45 sites of the onland ~45-km-long fault section. Similar structures are delineated by fresh fault scarps and prominent pull-apart basins in the Marmara Sea and Saros Bay. A second shock with Mw=6.8 occurred on 13 September 1912 implying 20 to 40-km-long rupture; the damage distribution and analysis of seismic records suggest an epicenter located further west near Saros Bay, which indicates the location of western termination of the 9 August rupture. Our modeling of historical seismic records reveal a relative source time function between the two events and indicates a 40 second rupture duration, and hence a 120±20-km-long fault rupture for the 9 August shock. An estimated total rupture length of 150±20 km for the two earthquakes combined with onshore and offshore fault segmentation allow us to better constrain the western limit of the Marmara Sea seismic gap and related potential for producing a large earthquake that was sharply increased by the devastating 1999 Izmit earthquake in the east.