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    Application of GPR to normal faults in the Buyuk Menderes Graben, western Turkey
    (Pergamon-Elsevier Science Ltd, 2013) Yalciner, Cahit Caglar; Altunel, Erhan; Bano, Maksim; Meghraoui, Mustapha; Karabacak, Volkan; Akyuz, H. Serdar
    Paleoseismology documents past surface-rupturing earthquakes that occurred on faults. This study is limited by the scarcity data on geomorphic and sedimentary environments that may preserve adequate records of deposition, erosion, and fault slip markers. Identifying relevant trenching sites can be difficult when a fault is buried or its surface expression has been eroded since the last tectonic motion. Ground penetrating radar (GPR) is an effective tool for locating suitable sites for trenching. Characteristic reflections are produced by boundaries between elements with contrasting electrical properties, such as grain size distribution (sorting, clay content, etc.), porosity, and water content. GPR is capable of resolving faults by imaging offset stratigraphic reflectors or reflections from the fault plane. GPR surveys were performed at two sites along the Buyuk Menderes Graben (western Turkey) to precisely locate the normal fault zone; there is no clear evidence of surface rupture at these sites. We used 250 and 500 MHz antennas for receiving the GPR data. From the GPR measurements, we determined locations suitable for paleoseismic investigations and performed a trenching study across the fault plane. The comparison of the GPR results and the trenching study indicates a good correlation between these methods. (C) 2012 Elsevier Ltd. All rights reserved.
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    Paleoseismic history and slip rate along the Sapanca-Akyazi segment of the 1999 Izmit earthquake rupture (Mw=7.4) of the North Anatolian Fault (Turkey)
    (Elsevier Science Bv, 2018) Dikbas, Aynur; Akyuz, H. Serdar; Meghraoui, Mustapha; Ferry, Matthieu; Altunel, Erhan; Zabci, Cengiz; Langridge, Robert
    The Sapanca-Alcyazi segment (SAS) is located on western part of the North Anatolian Fault (NAF) of Turkey. It was ruptured together with four other segments during the 17th August 1999 Izmit earthquake (M-w = 7.4) which caused similar to 145-km-long surface rupture in the east Marmara region. We conducted geomorphological investigations and 2D-3D paleoseismic trenching at 3 different sites near the Sakarya River along the SAS to obtain new data for the timing of past earthquakes and slip rate of this section of the NAF. Detailed investigations using Ground Penetrating Radar on the western bank of the Sakarya River reveal 18.5 +/- 0.5 m of right-lateral cumulative offset of an alluvial terrace dated as 850 +/- 11 years BP using Optically Stimulated Luminescence. The analysis of trench data from the three different sites of the SAS indicates the occurrence of four surface rupturing past earthquakes including the 1999 Izmit earthquake. According to the radiocarbon dating, these paleo-earthquakes can be correlated with the 1719 CE, 1567 CE, and 1037 CE historical earthquakes and suggest an average recurrence period between 273 and 322 years. The total dextral offset, the age of trench units and the terrace deposits together suggest a 22 +/- 3 mm/yr slip rate for this portion of the NAF.