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Slip Distribution and Rupture Characteristics of the 9 August 1912 Mürefte Earthquake (Ms=7.3) along the Ganos Segment of the North Anatolian Fault (Turkey)

Aksoy, M.E., Istanbul Technical University, Eurasia Institute of Earth Sciences, Maslak, Istanbul, 34469, TR, and Institut de Physique du Globe de Strasbourg, 5, Rue René Descartes, Strasbourg, 67084 FR,; Meghraoui, M., Institut de Physique du Globe de Strasbourg, 5, Rue René Descartes, Strasbourg, 67084 FR; Ferry, M., Centro de Geofísica de Évora, Rua Romao Ramalho, 59, Évora 7002-554, PT; Çakir, Z., and Akyüz, S., Istanbul Technical University, Faculty of Mines, Department of Geology, Maslak, Istanbul, 34469, TR; Altunel, E., Eskisehir Osmangazi University, Department of Geology, Meselik, Eskisehir, 26480, TR

The Ganos fault is the westernmost segment of the NAF that generated the 9 August 1912 earthquake (Ms=7.3) followed by a second shock on 13 September 1912 (Ms=6.9). We investigated the surface ruptures at 45 sites to document slip distribution and cumulative offset along strike. The 1912 offsets range from 2 to 5.5 m with a maximum slip in the northeastern fault section. Active deformation along the 45-km-long dextral strike-slip fault inland section displays morphology with offset drainage system. Classification of cumulative slip at 49 sites show 3 classes of stream offset, which indicate the onset of drainage development controlled by climatic events and provide the timing of long term deformation along the NAF. Analysis of the 1912 surface rupture inland shows a minimum of 4 sub-segments limited by the Kavak, Gölcük and Yörgüç pull-apart basins. In the Marmara Sea, similar structures show a significant bend (17°) near the coast and a large pull-apart basin (Central Basin) that may correspond to the eastern end of the 1912 earthquake rupture. Paleoseismic trenching at Saros, Yeniköy and Gaziköy yield a recurrence interval of 270 years for large events and a slip rate of 17,5-20 mm/yr. This reveals an interseismic maximum strain accumulation of ~5 m in accordance with our slip measurements for the 1912 rupture. Analysis of the 9 August and the 13 September 1912 damage distribution and seismic waveforms from 45 instrumental records documents the relative size and characteristics of the events. The large earthquake moment ~1,27 x1020 Nm corresponds to ~118 km rupture length and requires an offshore extension in both Marmara sea and Saros bay. More studies of seismic records and related fault parameters may better constrain the 9 August and 13 September 1912 ruptures nucleation and termination and the characteristics of the expected large earthquake in the Marmara Sea.


Last Modified: 2011 Aug 10