Bülent Kaypak

The 2005 - 2007 Bala (Ankara, central Turkey) earthquakes: a case study for strike-slip fault terminations

An intense seismic activity has been observed after the Bala (Ankara, NW central Turkey) earthquakes (30 July 2005: Mw=5.3, 20 December 2007: Mw=5.4, and 26 December 2007: Mw=5.3), continuing up to the present. The epicenters and the focal mechanism solutions of the earthquakes indicate that the right lateral strike-slip Afsar fault, trending N55-60°W, is responsible for the main shocks. The Afsar fault is thought to be the NW continuation of the Tuzgolu fault zone, which is one of the main neotectonic elements in central Anatolia. On the other hand, the aftershock distributions of the 2005 event have a NNE trend, and those of the 2007 event show a NW trending. Some focal mechanism solutions of the 2005 Bala earthquake aftershocks indicate normal and oblique normal faulting that corresponds to the NNE-trending Karakecili fault. It seems that seismic activation of the NNE-trending Karakecili fault was triggered by the 2005 main shock (Mw=5.3) that occurred on the NW trending right lateral strike-slip Afsar fault. The overall neotectonic framework is that the northwestern edge of the Tuzgolu fault zone, represented by the Afsar fault in Bala, terminates in an extensional system represented by the oblique-slip Karakecili fault.

Afyon-Akşehir Grabeni Batı Kenarının Tektonik Özellikleri Üzerine Jeolojik ve Jeofizik Gözlemler: İki Evreli Genişleme Modeli Hakkındaki Tartışmalara Bir Katkı

Afyon-Aksehir Grabeni’nin bati kenarini olusturan, baskalasim temel kayaclari ile Neojen cokel kayaclari arasindaki KB-GD dogrultulu tektonik dokanak bir grup arastirmaci tarafindan Sultandagi Fayi olarak isimlendirilmis ve ters fay olarak yorumlanmis, diger bir grup tarafindan ise sinirin normal fay oldugu ileri surulmustur. Bazi arastirmacilar da Sultandagi Fayi’ni normal fay olarak kabul etmekle birlikte, bu fay tarafindan kesilen daha eski Yakasenek Ters Fayi’ni tanimlamislardir. Bu calismada soz konusu Yakasenek Ters Fayi uzerinde jeolojik ve jeofizik calismalar gerceklestirilmistir. Temel birimler ile Neojen birimler arasindaki dokanak uzerinde uygulanan ‘Sismik Isin Yonlendirme’ yontemi ile Yakasenek Ters Fayi’na karsilik gelen tektonik hat kuzeydoguya egimli olarak belirlenmistir. Buradaki fayin guneybatinin aksine kuzeydoguya egimli olarak saptanmasi, bolgede Miyosen-Pliyosen’de sikismanin varligini ortaya koyan ve iki evreli graben modelini destekleyen Yakasenek Ters Fayi’nin bulunmadigini gostermistir. Bolgede yapilan arazi gozlemlerinde de ters faya yonelik herhangi bir veriye rastlanmamistir