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    Determination of recent tectonic deformations in the vicinity of Adana-Osmaniye-Hatay-Gaziantep triple junction region by half-space modeling
    (Centre Mersenne Pour Ldition Scientifique Ouverte, 2020) Yildiz, Selim Serhan; Ozkan, Ali; Yavasoglu, Hasan Hakan; Masson, Frederic; Tiryakioglu, Ibrahim; Alkan, Mehmet Nurullah; Bilgi, Serdar
    Recent earthquakes on the East Anatolian Fault Zone (EAFZ) and its surroundings in the Eastern Mediterranean region reveal a potential seismic hazard. It is thus needed to constrain deformations within tectonically active zones and clarify kinematics of the triple junction near Adana, Osmaniye, Hatay, and Gaziantep provinces. To understand strain accumulations and interseismic patterns of these active zones, one of the most popular geodetic methods was applied. Slip rates derived from Global Positioning System (GPS) observations by half-space modeling lead us to predict possible magnitudes and even probable locations of future destructive earthquakes. In this context, we form a region-specific GPS network consisting of both campaign observation sites and permanent stations to monitor strain accumulations across major active faults and investigate fault kinematics in detail. The campaign GPS data sets acquired in 2009, 2010, 2011, and 2019 were merged with data from different local permanent GPS networks for an integrated analysis of the determination of recent tectonic deformations. The TDEFNODE software was used to construct a kinematic model in an elastic and homogeneous half-space. The modeling approach needs inputs such as block and fault geometries, GPS site velocities, and locking depth assumptions. Our kinematic model indicates that an almost purely sinistral strike-slip rate of 7.5 mm/yr without any significant normal or reverse component is dominant on the main branch of the EAFZ. This estimated slip rate supports a prediction for a magnitude margin of 7.2-7.6 for the next probable large earthquake on the Turkoglu-Golbasi segment. The Karatas-Osmaniye Fault has a 3.4 mm/yr dextral strike-slip rate together with a reverse-slip rate of 3.1 mm/yr, which corresponds to a possible magnitude of 6.8-7.1 for an earthquake on the southwest end of the East Anatolian Fault. The Karasu Fault extends from the Turkoglu Triple Junction on the EAFZ in the north to the Hatay Triple Junction in the south. This critical fault segment has a sinistral 4.4-5.4 mm/yr slip rate with a normal component slip rate of 3.0 mm/yr, supporting earthquake prediction with a possible magnitude of 6.8-7.2. As a result, the determination of such kinematic indications in active tectonic zones by GPS observations plays a key role in seismic hazard analysis for the Eastern Mediterranean region.
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    Monitoring aseismic creep trends in the Ismetpasa and Destek segments throughout the North Anatolian Fault (NAF) with a large-scale GPS network
    (Copernicus Gesellschaft Mbh, 2020) Yavasoglu, Hasan Hakan; Alkan, Mehmet Nurullah; Bilgi, Serdar; Alkan, Oyku
    The North Anatolian Fault Zone (NAFZ) is an intersection area between the Anatolian and Eurasian plates. The Arabian Plate, which squeezes the Anatolian Plate from the south between the Eurasian Plate and itself, is also responsible for this formation. This tectonic motion causes the Anatolian Plate to move westwards with almost a 20 mm yr(-1) velocity, which has caused destructive earthquakes in history. Block boundaries that form the faults are generally locked to the bottom of the seismogenic layer because of the friction between blocks and are responsible for these discharges. However, there are also some unique events observed around the world, which may cause partially or fully free-slipping faults. This phenomenon is called aseismic creep and may occur through the entire seismogenic zone or at least to some depths. Additionally, it is a rare event in the world located in two reported segments along the North Anatolian Fault (NAF), which are Ismetpasa and Destek. In this study, we established GPS networks covering those segments and made three campaigns between 2014 and 2016. Considering the long-term geodetic movements of the blocks (Anatolian and Eurasian plates), surface velocities and fault parameters are calculated. The results of the model indicate that aseismic creep still continues with rates of 13.2 similar to 3.3 mm yr(-1) at Ismetpasa and 9.6 similar to 3.1 mm yr(-1) at Destek. Additionally, aseismic creep behavior is limited to some depths and decays linearly to the bottom of the seismogenic layer at both segments. This study suggests that this aseismic creep behavior will not prevent medium- to large-scale earthquakes in the long term.
  • Küçük Resim
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    Monitoring the deformation and strain analysis on the Ataturk Dam, Turkey
    (Taylor and Francis Ltd., 2018) Yavaşoğlu, Hasan Hakan; Kalkan, Yunus; Tiryakioğlu, İbrahim; Yiğit, Cemal Özer; Özbey, Volkan; Alkan, Mehmet Nurullah; Bilgi, Serdar; Alkan, Reha Metin
    Every man-made structure creates certain risks – dams are no exception. Most failures in man-made structures that have occurred could have been avoided if the structures’ behaviour had been inspected, monitored, and analyzed continuously, and if proper corrective measures had been taken in a timely fashion. The DSI (The General Directorate of State Hydraulic Works), which is the institution responsible for dam safety, has long used surveying methods to measure the displacements of geodetic points as a part of dam monitoring policy. In this study, we focus on the dam’s mechanical behaviour throughout a time period of more than 10 years. These study results have been derived from a separate, ongoing project that has monitored deformation on the Ataturk Dam and is now determining the water level of the reservoir. The project results show that although the dam body has become more stable and the water load behind the dam has increased, the rate of displacement of the dam has declined significantly. From these results, it can be seen that the reservoir water level can be increased evenly over time and that 542 m is the maximum water level of the dam’s reservoir. © 2017 The Author(s).
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    THE USAGE OF UNMANNED AERIAL VEHICLES (UAVs) FOR 3D MAPPING OF ARCHAEOLOGICAL SITES
    (Parlar Scientific Publications (P S P), 2019) Ilci, Veli; Ozulu, Ibrahim Murat; Bilgi, Serdar; Alkan, Reha Metin
    In archaeological sites, mapping, documentation, registration, and visualization of cultural heritage is very important for both cultural heritage's conservation, understanding of the historical importance and to transmit future generations. Traditionally, mapping and documentation studies are carried out through terrestrial measurements performed during excavation or at the end of each workday. Together with the improvements in image acquisition and processing techniques, Unmanned Aerial Vehicles (UAVs) have become an alternative for many applications including archaeological areas, historic sites, and cultural heritage buildings with accurately and efficiently. The UAVs provide the user low cost, fast data collection even in real-time, and application flexibility for mapping especially of small areas. This study aimed to investigate the usability of UAVs for 3D mapping of archaeological sites. For this purpose, two measurement campaigns were carried out in two different archaeological sites, AlacahoyUk and Sapinuva. From the outcome of this study, it is clear that aerial maps and 3D models of the studied sites were produced with UAV measurements within a cm to dm level of accuracy in a fast and cost-effective manner. In general, the results show that UAVs can be used for many archaeological mapping and documentation studies as a strong alternative to high cost and labor conventional terrestrial and photogrammetric surveying methods.