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Neotectonics and seismicity of the Ankara region : a case study in the Uruş area

Kaplan, Tülin
Study area, the Urus province, is located 70 km WNW of city of Ankara. Major settlements in the study area are two counties, Urus and Güdül; and there are a number of villages, such as, from W to E, Macun, Yogunpelit, Kabaca, Üregil, Özköy, Tahtaciörencik, Kirkkavak, Kavaközü, Kayi and Karacaören. The study area is 189 km2 in size and included in 1/25000-scaled topographic quadrangles of H28a3, a4, d1 and d2. The Güdül- Urus section of the Çeltikçi morphotectonic depression (Çeltikçi Basin) drained by the Antecedent Kirmir River and its second-order drainage system was first mapped in detail in the present study, and faults determining northern margin of the Çeltikçi depression were named as the Urus fault set comprising the SW part of the Çeltikçi Fault Zone; and the mechanism of the master fault of the Urus fault set was determined as left lateral oblique-slip fault with reverse component by the morphologic markers such as the deformed drainage system and pressure ridges. This was also supported by the fault plane solutions of the 2000.08.22 Urus earthquake. Three fault plane solutions, of which two of them for the 2000.08.22 Urus earthquake, and one of them for the 2003.02.27 Çamlidere earthquake, were done to determine nature of the source. Ground material underlying the city of Ankara were divided into three categories: (a) well-lithified basement rocks, (b) Pliocene fluvio-lacustrine v sedimentary sequence, and (c) unconsolidated terrace and alluvial sediments of Quaternary age. Quaternary unconsolidated sediments are densely populated in Ankara. These sediments are fine-grained and have a maximum thickness of 200 m or more. Inside these sediments, static ground water level is very close (as on average: 6 m) to ground surface. These conditions are quite suitable for liquefaction of these unconsolidated alluvial sediments. In addition,