Determining the strain upon the eastern section of the North Anatolian fault zone (NAFZ)
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ORIGINAL PAPER
Determining the strain upon the eastern section of the North Anatolian fault zone (NAFZ) Fatih Poyraz
Received: 3 September 2013 / Accepted: 22 January 2014 # Saudi Society for Geosciences 2014
Abstract Strain analysis is frequently used by disciplines such as material, tensile strength, mechanics, and soil mechanics. Strain causes deformation based on normal, shear, and torsional strain types. Strain cannot be measured directly, but it can be calculate by measuring deformation. Many plates are present on Earth. These plates move with respect to each other. One of the research fields of geodynamics is determining the plate movement properties. These properties are amount of plate movement with respect to other plates, rotation of plates, and the strain at plate borders and within plates. These plate movements can be calculated with seismic or geological data and geodetic data. In this study, strain analysis was conducted upon the results obtained from 35 GPS locations on Kelkit valley, which is on the Northern Anatolian fault zone (NAFZ), between the years of 2006 and 2008. Additionally, meaningful strain accumulation was found in the zones that were investigated, and its correspondence with the tectonic structure of the region was confirmed. The maximum and minimum principle strain rate parameters and maximum principle strain rate direction, which provides the average strain rate and strain directions, are E1=0.17 μs/year, E2=−0.24 μs/year, and β= −14.33 °. Furthermore, the mean pure shear strain rate of the region and the engineering shear strain rate was calculated as γ1 =−0.21 μrad/year, and γ2 =0.19 μrad/year, respectively. According to these results, there is a strain accumulation in this region. Keywords NAFZ . GPS . Strain analysis
F. Poyraz (*) Department of Geomatics Engineering, Faculty of Engineering, Cumhuriyet University, Sivas, Turkey e-mail: [email protected]
Introduction The Northern Anatolian fault zone (NAFZ) is one of the most active fault zones in Turkey, on which numerous devastating earthquakes took place throughout history. On this fault zone, there are a series of earthquakes that migrated from east to west between the years of 1939 and 1999. The region between the Erzincan Basin and Erbaa, which makes up the study region, has faced serious damages due to the 1939, 1942, and 1992 earthquakes. In the Erzincan Basin and its surroundings, The NAFZ, the Northern Anatolian fault line (NAF), and the Ovacik fault line (OF) form a complementary geometry and make up the most important tectonic structures of the region. The frequency of historically significant earthquakes is related to the motions of these three main fault lines (Kaypak and Eyidoğan 2002). The 1939 Erzincan earthquake (Fig. 1) is the biggest earthquake that took place in Turkey (Mw=7.9), and 32,962 were deceased in this earthquake. In this earthquake, a surface rupture, 360-km long, emerged, which extended from Erzincan to Erbaa, and to Amasya (Ketin 1976). On December 20, 1942, an earthquake (Fig. 1) with a magn
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