Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 9 3 2009 10.5194/nhess-9-663-2009 http://www.nat-hazards-earth-syst-sci.net/9/663/2009/ http://www.nat-hazards-earth-syst-sci.net/9/663/2009/nhess-9-663-2009.html http://www.nat-hazards-earth-syst-sci.net/9/663/2009/nhess-9-663-2009.pdf 663 671 2009-05-05 Investigation of long period crustal deformation on the inactive branch of the North Anatolian Fault Zone G. Akay H. Ozener ozener@boun.edu.tr Bogazici University, Kandilli Observatory and Earthquake Research Institute, Geodesy Department, Istanbul, Turkey Istanbul Technical University, Civil Engineering Faculty, Department of Geodesy and Photogrammetry Engineering, Istanbul, Turkey The western part of North Anatolian Fault (NAF) bifurcates around Mudurnu into two fault segments: northern and southern branch. The latter bifurcates again at west of Pamukova and creates middle strand. This study aimed to analyze crustal movement along the middle strand near Iznik which is considered as inactive fault. We focused on a microgeodetic network called General Command of Mapping-Istanbul Technical University (GCM-ITU) network around this segment. In order to obtain displacement values, five campaigns performed on the network which were used in the study. The displacements of the stations were estimated relative to the fixed stations located at the south of the network. The coordinates of the stations were calculated from the triangulation measurements realized in 1941 and 1963, trilateration measurements in 1981, and GPS campaigns in 2004 and 2007. Then, mean displacements of the network ranging between 7 mm/yr and 18 mm/yr were obtained for these years. <br><br> In the second part of the study, the GPS data were re-processed by adding three stations from Marmara Continuous GPS Network (MAGNET). Details of MAGNET can be found Ergintav et al. (2002). Estimated displacements were ranging between 3 mm/yr and 13 mm/yr for 2004 and 2007. TUBI station of IGS network was taken as stable. Akay, G.: Analysis of Total Crustal Deformation by the Comparison of Terrestrial and GPS Measurements in the Marmara Region, M. S. thesis, Bogazici University, Istanbul, Turkey, 92~pp., 2007. Ambraseys, N. N. and Finkel, C. F.: Long-term seismicity of Istanbul and of the Marmara sea region, Terra Nova, 3, 527–539, 1991. Ayhan, M. E., Demir, C., Lenk, O., Kiliçoglu, A., Altiner, Y., Barka, A. A., Ergintav, S., and Ozener, H.: Interseismic strain accumulation in the Marmara sea region, B. Seismol. Soc. Am., 92, 216–229, 2002. 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