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Item Evolution of earthquake hazards in İzmir response to M4+ earthquakes(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2022., 2022) Yılmaz, Tolunay.; Bulut, Fatih.In this study, we investigated the evolution of earthquake hazards in İzmir (Turkey), the city accommodating the third highest population in Turkey in response to M4+ size earthquakes analyzing Coulomb stress change on all potential receiver faults in the target region. The city is located in western Turkey, which falls under Aegean tectonics, which leads to very high earthquake activity in the region. Fault segments with increasing Coulomb stress host high earthquake activity verifying that M4+ earthquakes prepone the generation processes of some earthquakes. In contrast, fault segments with decreasing Coulomb stress host earthquake silence verifying that M4+ earthquakes postpone the generation processes of some earthquakes. Hence, M4+ earthquakes played a critical role in the occurrence of the 2021 Samos Earthquake (M 6.92) as they increased the Coulomb stress above 0.1 bars along its rupture plane. To sum up, our results show that Coulomb stress change generated by M4+ earthquakes plays a critical role in earthquake activity in the vicinity of İzmir, Turkey.Item Accuracy of GPS precise point positioning (PPP)(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2009., 2009.) Tekiç, Simge.; Şanlı, Uğur.We tried to show how the accuracy of GPS varies with respect to observing session duration by using the method of GIPSY precise point positioning (PPP), and how the site’s coordinates latitude, longitude and ellipsoidal height are affected. We used eleven IGS sites scattered almost evenly across the earth. GPS data were obtained from SOPAC archives at http://sopac.ucsd.edu/cgi-bin/dbDataBySite.cgi in Rinex (Receiver Independent Exchange) format. Processing of the GPS data was achieved through the use of Jet Propulsion Laboratory’s GIPSY OASIS II software and the application of “Precise Point Positioning” method (PPP) by Zumberge et al., (1997). In addition, least squares (LS) analysis was used to model the accuracy of PPP. Our study is based on the mathematical expression of Eckl et al., (2001) in which the dependence of accuracy on observing session is expressed with T. GPS data were segmented into shorter sessions from 1 h to 24 h. For each segment a GPS solution was produced using the PPP routine. We used RMS values from sub-segments to model the accuracy of GPS PPP. Results indicate that accuracy of GIPSY PPP depends only on the observing session T. Observing sessions shorter than 4 hour show dependency on latitude especially for the components longitude and ellipsoidal height. Using session length of 6 or more hours one can model the accuracy of GPS PPP with a simple formulation. Our results also indicate that prediction formulation for PPP is only slightly different from that of relative positioning formulation.Item Analysis of strain accumulation of the faulting zones by the help of continuous GPS stations(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Arslan, Asude.; Yılmaz, Onur.The NOlih Anatolian Fault Zone (NAFZ) belongs to one of the largest recent active fault systems in the Earth and it is the most effective zone in the Anatolian Plate. During the last decades a westward expansion of large earthquakes along the North Anatolian Fault has extented till the Sea of Marmara. The researchers give attention to the seismic gap in the Mmmara Sea. It is expected that northem and middle strand of NAFZ have a strong risk for future actions. The purpose of this study has two main goals. First one is to estimate velocity field of the region, and the second one is to investigate changes of the strain accumulation in the region by seven continuous GPS stations. This investigation is done by tiangulation method and by using GPS coordinate differences obtained from 2002 to 2004 periods. Strain parameters such as maximum and minimum principal strains, direction of the maximum and principal strain, maximum shear strain parameters and its direction are detennined.Item Analysis of preparedness and response to earthquake risk of Beşiktaş district using GIS(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2009., 2009.) Akşit, Ayşegül Özturan.; Yılmaz, Onur.; Özener, Haluk.For years Turkey is placed in a higher position among the countries that have been struck with loss of life and property due to earthquakes. Location of Turkey is the most important reason for this situation, since it is located on an active seismic belt. Being the economical, cultural and industrial centre of the country, Istanbul has a considerably high earthquake risk since the North Anatolian Fault Zone extents through the Marmara Sea. Considering the historical earthquakes especially Kocaeli Mw:7.4 in 1999, and the structure of the North Anatolian Fault Zone, it is estimated that the occurrence probability of an earthquake, bigger than Mw: 7.0 in the next 30 years is approximately 70 per cent. Furthermore the earthquake risk increases due to the rapid, unplanned urbanization and building construction that damages the specifications in Istanbul. Considering urban structuring in Istanbul, it has been concluded that connected districts have different characteristics. That is why the need of a comprehensive damage mitigation plan which is based on detailed earthquake hazard analysis emerged. The aim of this study is to investigate the preparedness and response levels of Besiktas district for a possible earthquake using the Geographic Information Systems and carrying out the analyses that will form a base for extensive damage mitigation plans. Within this concept, the earthquake risk for houses and business units located on Besiktas district is determined using a scenario earthquake which is obtained from Kandilli Observatory and Earthquake Research Institute Earthquake Engineering Department and a hazard assessment was determined by using the geological formation and seismic activity evaluations of the field. Additionally, estimation of the casualties in terms of damage probabilities by determining the building stocks, structural characteristics of these buildings (wood, steel, reinforced concrete etc.) and number of stories has been performed. A data infrastructure has been prepared for the planning activities which will be produced by using these analyses. In this way, the determination of the most appropriate meeting and tenting areas after an earthquake and the determination of the closest health care centers for injured people were practiced in this study.Item The design and use of continuous GNSS reference networks(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Avcı,Özgür.; Özener, Haluk.Today, through the developments in positioning technologies, coordinate information has been the information to which daily users who are not geodesists are frequently applied. Global Navigation Satellite Systems (GNSS), gives answer to the question "Where?" by defining the Earth on a reference system Vlith the help of recent investments and future aspects of GNSS systems wide range of users trust on the reliability and accuracy of position information achieved from these systems. In order to increase the accuracy of satellite based positioning systems to centimeter levels for the end users, Countries are establishing regional and local Continuously Operating Reference Stations (CORS) stations. These stations serve to satisfy high accurate position requirement of daily users, besides they are used for the studies like disaster management, transportation planning, detection of crustal movements and monitoring critical structures. In this study, the properties of GNSS with its future aspects, benefits of using all GNSS systems together, components required for system implementation and fields of use are presented with the proposals for the design of such systems. All components required for the CORS system are examined in two groups. First one is sites to which GNSS stations are installed and the other one is control center. Besides, the system is explained in details with its components in the scope of present technologies and techniques. The application of CORS systems are classified as R TK based applications, structural monitoring and crustal defOlwation. The benefits of using CORS system is mentioned, and proposals are given by regarding the technical properties of site equipments, the range of the application, economy and efficiency ofthe system. Examples from different studies are given in order to improve the quality and efficiency of ongoing projects and new project in different range.Item Analysis of total crustal deformation by the comparison of terrestrial and GPS measurement in the Marmara Region(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Akay, Gözde.; Özener, Haluk.In order to monitor crustal movements along one of the branches of North Anatolian Fault Zone (NAFZ), Geodesy Department of Kandilli Observatory and Earthquake Research Institute (KOERI) established microgeodetic networks around the eastern Marmara Region. General Command of Mapping (GCM) - Istanbul Technical University (ITU) net as part of the networks was measured from 1941 to 2007 five times with both space methods and conventional methods. The terrestrial network implemented by GCM as constitution of nine pillars scattered around south and north of Iznik Mekece fault. The net was measured by trilateration and triangulation methods by GCM and ITU. After KOERI Geodesy Department joined GCMITU net in Marmara Microgeodetic Project, the net was also monitored by GPS Campaigns. This study is based on the use of repeated observations over the network and on the analysis of the results obtained from different epochs by means of displacements. Thus, first all epoch of observations were computed and then the amount of displacements were analyzed judging by the fault movement and the accuracy values for each observation method. In addition to this, in order to check the coherence of results, GPS campaign data have been processed in detail.Item Determination of velocity field and strain accumulation of densification network in Marmara Region(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Deniz, İlke.; Özener, Haluk.For the implementation of constructing continuously operating reference stations and determination of transformation parameters, Turkey has started a new project: Turkish Continuously Operating Reference Stations (CORS-TR). Network-120, Network-90, and Network-60 were created as CORS test networks. These networks were composed of 115 check points which were established by institutions such as Geodesy Department of Kandilli Observatory and Emihquake Research Institute of Bogazic;i University, Istanbul Metropolitan Municipality, General Command of Mapping (GCM), General Directorate of Land Registry and Cadastre, and TUB IT AK Marmara Research Center (MRC) in KIrklareli, Tekirdag, Bursa, Bilecik, and Adapazan. Before the 1999 earthquake, positions of 115 check points which are tied to Turkish National Fundamental GPS Network (TNFGN) were determined by different time and institutions. Between July 15 and October 30, 2006; corporations such as TOPCON, TRIMBLE, and LEICA made observations. They evaluated CORS test networks. TOPCON and TRIMBLE measured all of CORS test networks, but LEICA measured only Network-60. Positions of main points of test networks were calculated and points were tied to International GNSS Service (lGS). The purpose of this study is to provide analysis of datum of 1999 observations and unity of datum, to analyze evaluation and computation of coordinates of 2006 observations, and to examine unity of datum in 2006 observations. It will also describe the determination of velocity field, strain accumulation on test field by modeling difference vectors between the coordinates of check points and the comparisons with other studies. The difference vector between the coordinates of check points in 1999 and 2006 (observed and computed by different companies) were derived.Item A Unified approach in GPS accuracy determination studies(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2009., 2009.) Öztürk, Didem.; Şanlı, Uğur.By the time GPS technology started to be used in Geodesy, it is much easier to reach the desired precision of point positioning. It is significantly a useful technique, thus one can easily predict the accuracy of GPS before a field survey and know about the quality of the observations that have been made on a reference point. Parallel to the improvement of the GPS technology, predicting the accuracy over short and long baselines has really been an important discussion. There have been several studies dealing with precise point positioning and the topic was to determine how the accuracy depends on the baseline length and the duration of the observing session (Eckl et al., 2001, Soler et al., 2005, Do an, 2007, Engin and Sanli, 2009). In the previous studies, the accuracies for the baselines were taken into account separately, and models have been created for the baselines between 30-300 km and 300- 3000 km. For the baselines smaller than 300 km, the accuracy was found to be a function of only the observing session duration (Eckl. et al., 2001) but for the baselines between 300-3000 km the results show that it does not only depend on the observing session it also depends on the inter-station distance (Engin and Sanli, 2009). In this study, the aim was to make the discussion topic certain and to combine a model for baselines ranging from 3 km to 3000 km. To define a unified model, GPS accuracy was tested in IGS network and the results are compared with recent studies by using GIPSY software. 13 baselines and the data of 10 days have been used in this research. Baseline lengths were between 3 km and 2739 km. The data of each day have been divided into sub sessions (6-8-12 and 24 hours) and then evaluated separately. Thus, the relation among GPS point positioning, base length and duration of observation has been examined. The results show that, the point positioning accuracy in IGS network over 3-3000 km depends both on the baseline length and the observing session duration. It is partially possible to define a unified model for baselines between 3 and 3000 km. To define a unified model for this range, could only be possible by testing out the significancy of various sub sets of Least Squares coefficients.Item Slip and strain partitioning across subparallel strands of the north Anatolian fault in the Marmara Region(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Okur, Yağızalp.; Bulut, Fatih.Marmara Region hosts a substantial part of the inhabitants in Turkey, more than 30% of the total population in the cities of Istanbul, Bursa, and Kocaeli. This region has experienced a number of large earthquakes in the past and still under threat of de structive earthquakes in the future. There, subparallel strands of the North Anatolian Fault (NAF) expand into the region distributing the earthquake hazards across the whole region. In this context, it is a key issue to investigate how the tectonic process is distributed between these sub-parallel strands in order to discriminate their indi vidual earthquake hazards. In this context, we jointly used historical earthquakes and GPS slip rates to quantify the slip and strain partitioning of the subparallel strands of the fault system. In addition to all available slip rates, we analyzed 50 new GPS sites (38 continuous and 12 campaign-based) to intensify the GPS network in the re gion. Historical earthquake records since 100 AD shows that 76.4% of the total slip is stored on the northern strand. The rest of the slip is partitioned between middle and southern strands as 11.8% and 11.8% respectively. These ratios are almost confirmed by GPS observations with 76.8%, 12.7%, and 10.5% slip ratios for northern, middle, and southern strands respectively. In conclusion, the northern strand of the NAF is the most active compared to the middle and southern strands and therefore accommo dates the highest earthquake hazards in the Marmara region. As middle and southern strands deform at substantially slower slip rates, they accommodate relatively much lower earthquake hazards.Item North Anatolian and East Anatolian faults beyond Karlıova in the east(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Elvanlı, Müfide.; Doğru, Aslı.The vicinity of Karliova, located at the intersection of two major fault systems in Turkey, is a seismically active region with a tectonically complex structure, however; there is little information about the east of Karliova, to what extent in the east the seismic activity continues. Investigating the possible extensions of the North Anatolian Fault (NAF) and the East Anatolian Fault (EAF) to the east of Karliova is therefore significant target to verify if there is a strain accumulation and therefore unknown earthquake hazard in the region. In this study, possible extensions of the NAF and the EAF in the east of Karliova were investigated using GPS slip rates. In this context, historical and instrumental period earthquakes had been compiled to identify potential indications for the possible extensions of the NAF and the EAF in the east of Karliova. With the focal mechanism solutions, it has been observed that the tectonics of this particular region is dominated by mostly strike slip structures. Fault information in previous studies conducted in the region was compiled to locate of potential eastern extensions to be used in the analysis. Also, the all-available GPS stations were homogenously combined (CORS-TR and campaign-based GPS measurements) to achieve the best possible station coverage to characterize tectonic surface deformation in the region. Using combined GPS data, Arctangent profiling analysis and block modeling analysis were performed to determine the location and movement of the potential extensions of the NAF and the EAF. The results of the analysis have shown that there is a strike slip faulting activity in the east of Karliova suggesting continuation of the NAF and the EAF in the east. The NAF extends ~ 170 km southeast of Karliova, by the slip rate of about 10.3 mm/y. The EAF extends ~ 180 km northeast of Karliova, by the slip rate of about 5.8 mm/y. For both fault systems, slip rates drastically decrease to the east of Karliova, down to the half of their slip rates in the west.Item Earthquake cycle of the North Anatolian Fault along the rupture zone of the August 17, 1668 Great Anatolian Earthquake(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2021., 2021.) Yıldırım, Sevil Cansu.; Bulut, Fatih.We investigated the earthquake cycle along the 450-km rupture zone of the August 17, 1668 Great Anatolian Earthquake (M8.1) combining GPS and earthquake data. We elaborated on elastic rebound theory investigating creeping and locked stages of the individual fault segments. We simultaneously estimated segment-based slip rates and locking depths. Slip rates are used to estimate preliminary inter-seismic slip stor ages assuming fully locked fault segments right after the mainshocks. Misfits between co-seismic slips and preliminary inter-seismic slip storages indicate that the fault does not store slip for a while after major earthquakes. Our analysis shows a partitioning between creeping and locked stages. Only along one segment, the 1943 M7.7 rupture, creep played a minor role during the seismic cycle (0.1%). Along the 1939 M7.9, 1957 M7.0, 1967 M7.2, and 1999 M7.5 ruptures, creep played a considerable role (16.9%, 22.2%, 17.9% and 22.4%, respectively). Along the 1942 M7.1, 1944 M7.4, 1999 M7.1 rupture zones, creep played a substantial role, and covered almost half of the seismic cycle (54.4%, 44.0% and 48.3%, respectively). The segments host currently differ ent earthquake potentials as they have distinctive creeping/locking rates despite the fact that they are exposed to similar deformation rates (between 19.5±0.5 – 24.2±0.3 mm/y). Our results show that slip rates systematically accelerate from the east to the west. Failure of the NAFZ will probably end at the western segments within 239±3 years. The space-time pattern of the earthquakes during the last three complete and the current incomplete cycles confirms that the failure of the NAFZ starts from the east, and systematically migrate to the west deceleratingly.Item Characterizing deformation of Istambul wall by geodetic terrestrial laser scanner(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2020., 2020.) Batur, Maryna.; Özener, Haluk.; Yılmaz, Onur.Historical buildings are an integral element of human civilization and they play a big part in cultural heritages for the descendants. Turkey, as being the cradle of civilizations, hosts very important and valuable structures. These structures are exposed to deformations for various reasons. Classical geodetic monitoring is a key approach for years to detect the deformation behaviors of structures. However, with the advanced technology, modern geodetic instruments replaced the classical geodetic instruments. Terrestrial Laser Scanner is built on the approach of acquiring a high-density point clouds, which represents X, Y, Z coordinates of the reflective surface. The case of Istanbul Land Walls has been chosen for this study due to its ~1600 years of historical value. In particular, two different towers of Land Walls having huge cracks on the front side of both structures is the motivation of this study. During this study, it happened an earthquake in Silivri offshore with the local magnitude (ML) of 5.8. Thus, there are 2 observations before and after the earthquake. In total, three independent measurements are made. Data obtained from scanning were compared in Cyclone 3DR software using Cloud-to-Cloud method of deformation analysis. Geometries of structures are defined with outputs found by point clouds; deformation progresses are scrutinized, and three-dimensional models are constituted. In conclusion, Terrestrial Laser Scanning technology is convenient to detect the deformations of historical structures with high capacity point clouds. The deformation maps obtained from comparing the point cloud data give a good structural information about the object by showing the current deformations and highlighting zones with possible future damage. It is thought that this study may provide a significant contribution to literature about not only protecting cultural heritage but also deformation studies.Item Seismo-geodetic characterization of the Tuzla Fault (İzmir/Turkey) : |its kinematics and earthquake potential(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2020., 2020.) Gelin, Bengisu.; Bulut, Fatih.Izmir, the third largest city of Turkey, located in western coast of the country is seismically super active due to Hellenic subduction zone and extensional back-arc basin under the Aegean Sea. This tectonic environment has attened the cities in the region again and again as reported in the historical records. Hence, investigating the seismically active faults in the region is crucial to elaborate on earthquake hazard for the cities along the Western Turkey. In this context, we jointly analyzed geodetic, geological and seismological data to investigate latest failure, present day deformation, slip accumulation and fault kinematics along the Tuzla Fault. Historical and recent earthquakes were investigated to determine the latest failure of the Fault and result reveals that there is no evidence of a large earthquake failing the Fault entirely since 1688. Six epochs GPS measurements of fteen stations were analyzed for the time period of 2009-2017 to obtain horizontal tectonic slip rates along the Tuzla Fault. As a result, overall southwest movements change between 26.67 1.03 mm/yr and 28.96 1.00 mm/yr with respect to Eurasia. Di erential slip rates range between 1.00 to 2.00 mm/yr. Magnitude calculations were done for Tuzla Fault and its segments seperately. Tuzla Fault has currently a potential to generate a strong earthquake up to M6.2-M6.8. Strain analysis results show that the Çatalca Segment and northern Orhanlı Segment, accumulates high shear strain and therefore accommodate higher potential for co-seismic slip. According to fault plane solutions and maximum shear strain values and planes, Cumalı Segment has dextral characteristic, however, maximum shear strain planes indicates sinistral structure in Çatalca Segment.Item Earthquake potential of the East Anatolian Fault(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2020., 2020.) Uçan, Kaan Alper.; Bulut, Fatih.This study aims to forecast magnitude of future strong (6.0 M <7.0) and major (7.0 M <8.0) earthquakes along the East Anatolian Fault Zone (EAFZ hereafter), which is a seismically active plate boundary between Arabian and Anatolian plates. In this context, we investigated segmentation of the EAFZ reviewing previous studies on structural variation zone and historical earthquakes. We analysed the combined GPS velocity eld to obtain back-slips using steepest descent/gradient inversion method. The method projects GPS-derived back-slip rates onto the fault plane using Okada's quasi-in nite space model simulating elastic Green's functions to obtain on-fault slip de cit rates. Resulting slip de cit rates are used to estimate present-day slip budgets on each fault segment. We also analysed along-fault b-value distribution to verify if it can be used to di erentiate between locked and creeping patches. Our results show that the EAFZ currently have a 1.51 m average slip. We suggest that the EAFZ is split into eight fault segments generating strong/major earthquakes. The January 24, 2020 Elaz g earthquake (M 6.8) ruptured the Sivrice-Pütürge segment verifying our segmentation model and magnitude forecasts for future earthquakes. We found no slip de cit accumulation observed on the Hacılar segment. Remaining six segments are able to generate three strong, three major earthquakes. Currently Karlıova, Kaleönü-Beyhan, Palu-Sivrice, Taştepe, Çelikhan-Erkenek, Gölbaşı-Pazarcık segments can currently generate M 7.0, M 6.9, M 7.1, M 6.8, M 6.9, M 7.4 earthquakes, respectively. Karlıova, Palu-Sivrice, Taştepe, Gölbaşı-Pazarcık segments currently have the potential to generate previous strong/major earthquakes they hosted. We observed a reverse correlation between slip de cit rates and b-values verifying that b-value can be used to discriminate locked and creeping fault segments.Item Network design and optimization for deformation monitoring on Tuzla fault-İzmir and its vicinity(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2007., 2007.) Halıcıoğlu, Kerem.; Özener, Haluk.Seismological and geodynamic researches emphasize that the Aegean Region which comprises the Hellenic Arc, Greek mainland and western Turkey is the most seismically active region in western Eurasia. The convergence of Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasia. Western Anatolia is a valuable laboratory for Earth sciences because of its complex geological structure. Izmir as a big metropolitan city in Turkey with a 2.5 million population has a great risk about big earthquakes. Unfortunately, geodynamics studies which were performed in this region are insufficient or cover large areas instead of specific faults. This study aims to perform a large scale investigation focusing on Tuzla Fault and its vicinity for better understanding of region tectonics. Tuzla Fault forms the lineament trending NESW between Menderes Town and Doganbey Cape. Moreover, Tuzla Fault is an important fault in terms of seismic activities and the distance to the highly populated metropolitan city of Izmir. In order to investigate the crustal deformation on Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This project produced a schedule for crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension of study area in terms of monitoring different types of fault characteristics.Item Recent velocity field in western Anatolia from continuous GPS data(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Kaynarca, Tayfun.; Özener, Haluk.Aegean Region is one of the most deforming parts of Alpine-Himalayan orogenic belt. The region is intensely under pure shear stress which is caused by an internally deforming counter-clock rotation of the Anatolian plate relative to Eurasian plate. The counter-clockwise motion caused by the compression of the Arabian plate through Anatolian plate eventuate in north-south extension and formation of east-west trending active grabens. Many seismological studies were carried out in Western Anatolia and its surroundings due to remarkable seismic activity in the area. In this study, GPS data from 16 of CORS-TR stations which measured in 2015, 2016, 2017 and 2018 were used by considering the seasonal effects. The obtained velocities of selected CORS-TR stations were combined with the velocity fields of Reilinger et al., (2006) and Aktu˘g et al., (2009) for better understanding of the dynamic mechanism of the region. 14 mutual IGS stations in the studies were utilized for the transformation process. Combined velocity values vary between 10.66 ± 1.22 mm/yr and 32.71 ± 0.54 mm/yr. The obtained velocity field demonstrates that Western Anatolia is characterized by predominantly north-south extension and experiencing rapid internal deformation. Western Anatolia’s internal mechanism supports graben formation in the east-west direction and results are consistent with the characteristics of the Western Anatolia extensional mechanism.Item Interaction between atmospheric conditions and GPS accuracy: A case study from Istanbul(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Eraslan, Ayça.; Doğru, Aslı.In this study, changes of the position data recorded by KANT permanent GPS station has been examined under the environmental conditions of the station. This cGPS station is situated in Kandilli Campus of Boğaziçi University and operated by Kandilli Observatory and Earthquake Research Institute. It is one of the sites of the Marmara GPS Network-MAGNET (TUBITAK), which was established for earthquake research in the Marmara Region. Data from KANT station has been continuously archived with thirty-second recording interval since 1999 in RINEX format. In this study, the position coordinates of the station have been obtained by GAMIT program with 2014 data. Data processing has been performed by selecting data from other short- and long-distance cGPS stations to minimize the potential errors and daily position GPS time series have been obtained. Error sources at such a permanent GPS station can be listed as satellite clock, upper atmosphere (ionosphere), receiver clock, satellite orbit, lower atmosphere (troposhere) and multipath. In this study, changes in the position coordinates of the station have been compared with atmospheric conditions to understand whether the effects of atmospheric pressure, temperature, wind and humidity. Meteorological data obtained from Meteorology Laboratory of the Institute in daily base. According to the results, the coordinate displacements caused by environmental conditions can be significant and the effects should be taken into account, especially in high-precision geophysical research.Item Installation of borehole strainmeters to monitor North Anatolian fault near Istanbul(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2018., 2018.) Bal, Osman.; Özener, Haluk.The North Anatolian Fault Zone (NAFZ) , which forms the plate boundary between the Anatolian plate in the south and the Eurasian plate in the north, runs under the Marmara Sea and is located less than 20 km from the city of _Istanbul. According to historical seismicity data and recurrence times; an earthquake, which is bigger than magnitude 7, is expected. Geodesists have been doing many observations on the NAFZ with various techniques since 1972. Geodesy Department of Kandilli Observatory and Earthquake Research Institute (KOERI) plays a crucial role on deformation measurement on the NAFZ with its micro-geodetic networks since 1989. By using the developing technology in time, Geodesy Department of KOERI incorporated some other terrestrial deformation measuring techniques like creepmeters and strainmeters. The aim of this thesis is to discuss, the need of the strainmeter, installation cases for two boreholes, solutions found for site speci c problems and the result of installation. Installed strainmeters will allow us to monitor potential slow-slip events along the Marmara Seismic Gap.Item Time series analysis of GPS permanent stations around east Anatolia(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2016., 2016.) Julaiti, Wumiti.; Ergintav, Semih.The eastern part of Anatolia is a significant location in the world due to its tectonically active background. It includes one of the major fault zone of Anatolia: left-lateral East Anatolian Fault (EAF), forming a boundary between the Anatolian and the Arabian plates. Its long-term slip rate as well as localizations of creeping zones, locking depth and the surface offsets can be obtained by using inter-seismic Global Positioning system (GPS) velocities and proper models. However, the quality of position time series generated from each GPS station directly determines the accuracy of the velocity estimation. The Continuous Operating Reference Stations (CORS) of Turkish National Permanent GNSS Network-Active (TNPGN-Active), mainly using the GPS measurements, covers the most area of Turkey, including the whole segments of the EAF. In the thesis duration, a limited part of the TNPGN-Active data could be archived. Then, as a thesis objective, we decided to control the quality of GPS velocities, estimated from limited data of stations around the EAF, in order to improve the GPS velocity field in this region. In this study, 2-year span GPS data from 37 sites of TNPGN-Active were processed by using GAMIT/GLOBK to generate daily position time series of each station as well as the related velocity estimates. For the GPS time series, mainly noise analysis was applied to distinguish which station is sufficient enough for using its velocity estimates. Finally, it has been found that the velocity estimates of at least three specific stations with spectral indices > 0.7 and linear trend uncertainties > 2.5 mm on horizontal components, which are MUUS, HINI and GEME, are not quite reliable with the limited 2-year data. This result will be highly likely an important reference for the campaign type GPS study along Hazar-Palu segment of the EAF in the future. To estimate a high quality velocity field, new campaign sites could be added around the problematic TNPGN-Active stations.Item Recent velocity field in eastern anatolia from a combination of continuous and campaign type GPS observation(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2013., 2013.) Farisoğulları, Ömer; Özener, Haluk.The tectonic structure of our country is the result of collision of Arabian, African and Eurasian plates. Deformation towards to the west of the Karlıova region, which is the conjunction of North Anatolian Fault Zone with East Anatolian Fault Zone, is caused by the strike-slip faulting along North Anatolian Fault Zone and East Anatolian Fault Zone and the deformation from this intersection area to the east is caused by the thrust faults exist in the region. In Eastern Turkey, many scientific studies have been conducted with applying geodetic methods. In this study, six epochs of data from 19 of CORS-TR stations were used and data was chosen by considering seasonal effects. GAMIT/GLOBK academic software was used to process the data and obtain velocity field of the study area. The obtained velocities of stations were combined with the velocity fields of Reilinger et al., (2006) and Aktuğ et al., (2013). The transformation process is performed by using 13 IGS stations which are mutual in the studies. Obtained velocity values vary between 3.77 mm/yr ±0.52 mm/yr and 24.94 mm/yr ±5.34 mm/yr. The results obtained show consistency with the recent tectonic structure of the region. The results of prior studies in the study area is considered and taken into account within the processing of data which made it possible to consider a long term data set. Long term data set allowed obtaining the velocity field of the area more accurately.