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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 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 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 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 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 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 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 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 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 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.