Boğaziçi Üniversitesi Tezleri

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0-30V / 5A digital power supply with computer control
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2010., 2010.) Sünetci, Önder.; Kahya, Yasemin.; Cerid, Ömer.
Most of the electronic circuits require a DC power supply to operate. There are many designs and topologies covering different properties and specifications for DC power supplies. The voltage and current range and accuracy, power capacity and quality, failure protections, isolations, robustness and reliability, power efficiency, size and ease of usage are some of the most important characteristics of power supplies. A DC power supply with the parameters given in the following sections is designed and realized for the fulfillment of the Master of Science thesis. The criteria for making decisions on the design parameters were range, isolations and ease of use. The range is proposed to be 30VDC and 5A output. The isolation is realized both between the mains and the device and between the device and PC that, when connected, controls it. For the ease of use, a 4x4 keypad to enter data and a 2x20 character LCD to monitor data are used.
1,27-2,50 GeV/c momentumlu pozitif pionların protonlarla etkileşmeleri
(Thesis (Assoc. Prof.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1981., 1981.) Arık, Engin.
1-D local crustal structures from seismological data in the Cyprus Subduction Zone and Antalya bay
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2013., 2013.) Perk, Şükran.; Karabulut, Hayrullah.
The eastern Mediterranean is a tectonically complex region, where long-term subduction and accretion processes have shaped the overall evolution. Recently, many seismic tomography studies have shown subducted slabs of the Neo-Tethyan lithosphere, continuing its subduction in the Hellenic trench, stalled in the Cyprus trench and being torn near the intersection between them. Antalya bay is a key region located on the western flank of the Cyprus Subduction Zone (CSZ), close to the junction between the Hellenic and Cyprus Arcs. Here deep earthquakes are nucleated, which otherwise cannot be seen anywhere else along the CSZ. For this reason, we focus our attention specifically to the Antalya Bay area but also the remaining parts of the CSZ. Several regional studies have been carried out to define the velocity structure beneath the region but none have been able to locate the CSZ. One of the main reasons for this was the lack of incorporation of a wide seismic network in those regional studies. We compile a large catalog of seismicity and relocate earthquakes to infer 1D local crustal structure using the clusters of seismicity. We used seismic data between 2005 – 2011 which are recorded at more than 250 seismic stations operated by several agencies and portable deployments. The data-set is composed of over 10,000 events and earthquakes can be grouped in several distinct clusters. We defined five of these clusters, where the total number of events is more than 4500, among which we selected over 2000 events with the highest data quality. 1-D local P-wave velocity models are developed using this high quality data-set and the earthquakes are relocated using the local velocity models. The compiled and reanalyzed data will contribute to perform local earthquake tomography. Moreover, obtained local velocity models represent a fundamental step towards an improved seismic tomography studies in a very crucial region in the eastern Mediterranean.
10-BIT 60 MS/s two-step flash ADC design
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2013., 2013.) Esen, Vahap Barış.; Dündar, Günhan,
Two step flash ADCs have widespread use in electronic circuits, since they can achieve decent resolutions in high speed applications. Their two step structure requires coordination of many analog blocks that is ensured by control signals. Generating and delivering these control signals as clock signals are as important as the design of the analog blocks. In this thesis analog design of a two-step flash ADC which is used as a test circuit for an automation tool that can synthesize the necessary clock signals is presented. The design procedures of the blocks in 10-bit 60 MS/s two step flash ADC are examined. The overall design is realized by using UMC 180nm technology. Finally the simulation results obtained by using Mentor Graphics tools and MATLAB are presented. The performance of the ADC is evaluated using ENOB as a figure of merit. Resolutions up to eight bits are attained in typical case simulations. Comparison with the literature is also made by using energy per conversion values.
140 Mb/s deqpsk modem if stage
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1985., 1985.) Suyabatmaz, M. Akif.; Cerid, Ömer.
Recently, as the digital technology progresses, the exploding capacity of digital information nececities fast digital communication systems. Since the congestion prevailing in many regions of radio frenuency spectrum has created the need for improved spectrum utilization techniques, the demand for multilevel (Mrary) digital modulation techniques has also increased. In this thesis, a differentially encoded and differentially decoded quadrature phase shift keyed modem, employing coherent demodulator, was briefly analy.zed. System building blocks were investigated and the one, proper to high data rate application, was chosen for system realization. A working circuit, was build as an intermediate frequency (IF) stage, operating at 140 Mbit per second, and realized.
16. yüzyılda bir nazire şairi Sebzi ve nazireleri
(Thesis (M.A.) - Bogazici University. Institue of Social Sciences, 2001., 2001.) Karataş, İbrahim Hakan.
16S rDNA analysis of microbial communities in a highly polluted region of the Marmara Sea
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2007., 2007.) Türker, Gökhan.; İnce, Bahar Kasapgil.
The Marmara Sea is a small (size 70 x 250 km) intercontinental basin connecting Black Sea and Mediterranean Sea. The population of Marmara region reaches to 25 million and therefore there is large number of domestic and industrial wastewater discharges to the Marmara Sea from different points. Also large quantities of Central Asian oil and gas are transported to the west through the Marmara Sea. Combining effect of pollution sources create a chronic pollution at the Marmara Sea and formed several anoxic sediments in highly polluted sites. One of the areas is Küçükçekmece region. The region is populated by both residential and industrial sites and takes domestic and industrial effluent of more than 3 million people. Industrial sites mainly composed of metal industry, textile and leather industry, medicine industry, paper industry, chemical industry, rubber and plastic industry. Also in 1999 due to tanker accident at Küçükçekmece beach, the region was polluted with more than 3000 tones of petroleum. Sediment is a carbon and nutrient pool for aquatic environments. The presence of hydrocarbon compounds creates a suitable environment for the growth of anaerobic bacteria. Anaerobic biodegradation processes are slower than aerobic biodegradation. However, anaerobic processes can be a significant factor in removal of organic contaminants owing to the abundance of anaerobic electron acceptors relative to dissolved xygen; therefore promising a stable and long term removal of contaminants. It has been estimated that less than 1% of the total microbial population in the land environment and even less in the marine environment have been successfully isolated in pure culture. Marmara Sea has great importance not only because of geological position but also its composition of microbial life which still remains in darkness. The microbial diversity in this unique ecosystem has not been studied using culture-independent molecular techniques yet. Microbial community analyses together with chemical analyses of the sediments will undoubtly form a base to develop bioremediation strategies to overcome chronic pollution at the Küçükçekmece coast. Main aim of this study is to find a suitable microbial community in anoxic sediments taken from Marmara Sea for a bioremediation strategy depending on anaerobic biodegradation. The microbial diversity and community structure were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rDNA Clone Library method. The results were evaluated with sediment quality parameters along the sampling point. Established results will be used with other information from the literature to analyze the suitability of any of the community in the anoxic sediments from the Küçükçekmeçe coast for bioremediation purposes. Suitable communities will be marked and used as a cornerstone for a bioremediation strategy based on anaerobic biodegradation. DGGE results indicate presence of 34 different bands for bacterial community and 15 different bands for archaeal community with each band representing a different organism. Clone library results are parallel to results of DGGE. In bacterial clone library there are 23 different clones and 26 different clones for September 05 and December 06 respectively. In archaeal 16S rDNA clone library, 19 different clones and 20 different clones were found in September 05 and December 06 respectively. The result of sequencing of bacterial dominant clones indicate presence of Trichococcus pasteurii, Clostridium glycolicum in September 05 and Elbe River snow isolate Iso26, Xanthomonas sp. CC-FH5, and Gallicola barnesae in December 06. Archaeal dominant clones are Methanoplanus petrolearius, Methanoplanus limicola, Methanogenium organophilum in September 05 and Methanogenium frigidum and Methanosaeta sp. in December 06. Results of clone library generation show that syntrophic relations are running in both times. In September 05, fermentation and hydrogenotrophic methanogenesis dominated pathway. In December 06, anaerobic respiration and fermentation coupled with acetoclastic and hydrogenotrophic methanogenesis dominated the pathway.
16S rDNA analysis of microbial communities in anoxic marine sediments of the Marmara Sea
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2007., 2007.) Sezgin, Aslı.; İnce, Bahar Kasapgil.
The sediments of the Marmara Sea are of importance since they are believed to have been a rather sensitive recorder of climatic, biological and chemical changes and water-mass movements in the region. In this study, overall microbial community of coastal sediments from the Marmara Sea was characterized by cloning and sequencing of 16S rRNA genes. Denaturing Gradient Gel Electrophoresis was used to investigate the seasonal distribution of the microbial communities in coastal sediments from Tuzla and Moda. The sequencing of clone libraries revealed a higher microbial diversity in anoxic sediment samples of Tuzla than that of derived from Moda. and served to understand the potential dominant metabolic processes prevailing under anoxic conditions. Methylotrophic methanogenesis and denitrification were found as the potential dominant metabolic processes in Tuzla sediments, whereas hydrogenotrophic methanogenesis and fermentation appeared to be the potential dominant metabolic processes in Moda sediments. DGGE data revealed a more significant seasonal change in microbial community structure of Tuzla sediments.|Keywords: Marmara Sea, Anoxic Marine Sediments, 16S rDNA, Microbial Diversity, Clone Library
1940-nm thulium fiber laser ceramic bracket debonding
(Thesis (M.S.) - Bogazici University. Institute of Biomedical Engineering, 2012., 2012.) Demirkan, İrem.; Gülsoy, Murat,
The aim of the study was to determine the proper laser paramaters for 1940-nm Thulium Fiber Laser for ceramic bracket removing. In order to assess the e ectiveness of 1940-nm Thulium Fiber Laser in orthodontic ceramic bracket debonding , polycrystalline ceramic brackets were bonded to mandibular bovine teeth with adhesive agent.The samples were divided into 9 di erent groups due to applied laser power and laser duration, debonding method used . There was a control group that had no laser application . The e cency of the laser was investigated together with the required debonding forces and intrapulpal temperature changes . In this study, keeping intrapulpal temperature changes below the threshold value that is accepted 5; 5 C must be accepted as a must. In most of the lasing groups , the increase in intrapulpal temperature changes were observed almost below the threshold value 5; 5 C . The ndings revealed that 1940-nm Thulium Fiber Laser irradiation could reduce the needed debonding force or SBS (shear bond strength ) values signi cantly compared to control group . Irradiation of the specimens by 1940-nm Thulium Fiber Laser caused more than 50% reduction in the needed debonding force when compared to the control group. Di erent application methods : non-scanning and scanning were studied to assess the e ects of the distinct con gurations. Scanning method was tried to reduce the intrapulpal temperature rise during laser irradiation but in this study side e ects of this method were faced. It was revealed that di erent application methods did not create any remarkable di erences . In more than 50% of samples with energies 25 J or more, adhesive remnant hasn't been observed on enamel surfaces for the laser groups.|Keywords : Laser, Debonding, Ceramic Brackets.
2-D mathematical modelling of hydrogen storage in metal hydrides
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2009., 2009.) Küçük, Gülşad.; Aksan, Emre.
In this study a numerical model which simulates heat and mass transfer processes of hydrogen absorption in LaNi5 is studied. Energy balance method is used for discretizing the heat equation. Transient heat conduction with convective boundary conditions is evaluated with explicit scheme. The analyses are conducted using MATLAB. Evaluation of temperature profiles and hydrogen mass that is being absorbed during hydriding are shown to be correlated with the experimental data and with the previous numerical studies. Since the hydriding reaction is exothermic, the rate of removal of heat released is critical in time needed to reach saturation in metal-hydride reactor. The effects of bed geometry, inlet hydrogen pressure, and metal porosity, initial bed temperature and the temperature of cooling fluid are investigated. Different cases are compared with the base case which is chosen to have similarities with conventional metal hydride tanks in reactor geometry and in thermophysical properties.
2-D modeling of compression ignition engine combustion
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Yıldırım, Cebrail.; Bedir, Hasan.
Internal combustion engines are the cornerstones of our society. They are widely used in a vast range of area from transportation to power generation. Since they are mostly petroleum-powered and emission regulations are getting tighter due to the environmental concerns, ICE research activity is vibrant today. In the present study, a multidimational CFD approach has been used to simulate a CI diesel engine combustion to investigate the e ect of injection timing and swirl ratio on combustion and emissions. AVL Fire software has been used for combustion, spray and emission modeling. Within this context, ECFM-3Z, k {u100000} ", Wave break-up, Dukowicz, extended Zeldovich and Hiroyasu approaches have been used for, in order, combustion, turbulence, spray atomization, spray evaporation, NOx and soot emission modeling. When compared with the experimental data, the simulation results show a good agreement. As for the swirl ratios, minimum NO and soot emission are achieved at SR 3.0 while the optimum bsfc and maximum indicated e ciency are found at SR 1.0. Findings of di erent injection timing are that advanced injection results in higher NO and higher soot emissions as the retarded injection provides lower NO and higher soot emissions with reference to the baseline simulation.. As a result, SR 1.0 and reference injection timing have been found to be the optimum con guration in terms of bsfc and emissions for the engine studied.
2D to 3D video conversion
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Çoban Aydın, Aysun.; Acar, Burak.
Stereoscopic 3D visualisation is increasingly embedded into social life through the use of commercially available 3D-TV sets. In this work, a hybrid approach for 2D to 3D conversion is presented to produce stereoscopic 3D video automatically from 2D mono video frames. Each frame is synthesized to stereo pairs. Disparity/depth information required for 3D view is extracted from mono frame sequences based on motion and geometrical cues. Depth estimation of the scene is considered separately for background and foreground. Background geometry of the scene is determined by using geometrical cues such as vanishing point and straight lines in the image. According to this geometry, relevant information on the background depth eld of a single image is estimated to generate a canonic disparity map of the background. For foreground depth estimation, on the other hand, two approaches are presented. First approach is based on detection of moving foreground objects. A depth value is assigned to each object based on its corresponding location in the background depth map. In the second approach, background registration is applied for consecutive frames that are captured by a moving camera. By this method, disparity in foreground regions is distinguished from background disparity that leads to a distinctive 3D e ect on foreground regions. Consequently, depth/disparity information of foreground regions is combined with background canonic disparity map. According to these nal disparity maps, pixels of the original frames are shifted to generate virtual frames to enable 3D views. This work is accompanied by a subjective evaluation on the basis of user test which compare our 3D results with commercially available 3D-TV sets.
3 - D optical profilometry at micron scale with modified fiber optic Lloyd's mirror technique
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2017., 2017.) İnanç, Arda.; İnci, Naci.
In this thesis, it is shown that a modiﬁed ﬁber optic Lloyd’s mirror technique is suitable and practical to produce fringe patterns that have easily adjustable frequency. This allows measuring 3D height distribution of test objects at micron scale without using additional elements as part of the optical projection unit. To test the validity of the proposed method, images that contain deformed fringe patterns due to the height distribution of micron scale test objects are recorded by a CCD camera and analysed with one dimensional continuous wavelet transform. After the extraction of phase map using 1D continuous wavelet transform, the height dis tribution of the test objects is obtained by further analyses. Finally, the results are discussed and compared with the expected values.
3 D display of organs using CT data implementation on an IBM PC
(Thesis (M.S.)- Bogazici University. Institute of Biomedical Engineering, 1987., 1987.) Hüner, Mutlu.; Güveniş, Albert.
This thesis presents a low cost software package for the three dimensional display of organs using an IBM microcomputer.First existing 3D display techniques and their application in medicine are given. Then the particular algorithm selected for implementation is described and explanations pertinent to this specific implementation are discussed. The boundary detection algorithm used is the one developed by G.T. Herman et,al, Standard computer graphics methods displaying 3D objects. A grid technique is are used introduced for when performing the scan conversion in orter to increase image quality. Some of the results obtained by using mathematical phantoms are presented and discussed. The results indicate that this package can display high resolution images withoul antialiasing effect that is typically encountered in similer packages. It is shown that low pass filtering is only needed in extreme cases.
3+1 formulation in Newton-Cartan gravity
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Aras, Ulaş.; Bleeken, Dieter Van den.
In this thesis, we will give a review of torsion-free Newton- Cartan theory. We will start by doing a large c expansion of general relativity and we will restrict ourselves to a few leading orders. After obtaining Newton-Cartan theory in this way, we will explore its symmetries. Through a special set of combined symmetries, we will construct a split space and time structure. Lastly, we will work out the field equations and equations of motion for a particle in the 3+1 formulation we have obtained.
3-D crustal structure of the Isparta angle region from local earthquake tomography
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2011., 2011.) Çakır, Ersin.; Türkelli, Niyazi.
Isparta Angle is a seismically active and complex zone in terms of tectonic and geologic features. A temporary seismic network consisting of nineteen three-component broadband stations were installed around Isparta Angle (IA) and surroundings to address some of the important questions. Detailed crustal structure of the Isparta Angle were obtained using the seismic data collected over two years from July 2006 to June 2008. Results of this study will contribute to beter characterize the crustal structure and the seismicity of the region. In this study, local earthquake data that were collected from temporary broad-band seismic array operated in the region, data from permanent stations of Kandilli Observatory and Earthquake Research Institute (KOERI), permanent stations of Disaster and Emergency Management Presidency (DEMP) and Süleyman Demirel University (SDU) in order to determine the upper crust seismic P wave velocity structure of IA and the surrounding regions by three-dimensional (3-D) Local Earthquake Tomography (LET) method. S-wave arrival times were not included due to strong attenuation and higher picking errors of S-phases. The result of tomographic processes, 3-D velocity model, was compared with the seismological and tectonic features of the region and also compared with the results of the previous studies in the region. The results suggest that low-velocity zones beneath Isparta Angle in the depth range between 0-10 km can be related to alluvial deposits, and the velocity variation below 20 km depth can be related with the transition from upper crust to lower crust.
3-D crustal structure of the Simav - Küyahya and surrounding regions
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2017., 2017.) Duran, Nuray.; Konca, Ali Özgün.
Kütahya and surroundings are quite complex structures from a tectonic and geological perspective. On May 19, 2011, an earthquake of magnitude M = 5.9 occurred in Simav. The purpose of this thesis is determination of the 3-D seismic velocity structure applying the local earthquake tomography method, using earthquakes that occurred between the years 2010 and 2015 in Kütahya Simav and surroundings. The signifigance of this study is that the first 1-D and 3-D tomographic inversion for Simav, Kütahya and surroundings is done by this study. The region's 1-D velocity model, 3-D velocity model and crustal structure are obtained. In this study, the 3-D velocity distribution up to 30 km depth of upper crust of the study area is determined with tomographic inversion methods. For this purpose, by creating data sets, travel time of phases were prepared by tomographic inversion format, appropriate model structure has been created, Vp, Vs and Vp/Vs models that obtained with appropriate resolution parameters and tomographic inversion, has been interpreted with geological and tectonic features of the area. At 30 km depth, P and S waves velocity structure of Kütahya, Simav and surroundings were obtained. The Graben system of the region is supported by the velocity cross-section obtained. The depth of the graben is determined as 20 km. The relationship between the hypocentre of the recorded earthquakes in the region and Vp, Vs, and Vp/Vs anomalies has been revealed with horizontal and vertical cross-sections. Comments are made about the structural differences of the region’s P wave and S wave velocity information and the physical properties of the rock’s Vp/Vs ratio information. Fault systems, potential fault zones and earthquake activity of the region are discussed with the combined results of the study.
3-D gamma knife distribution by normoxic gel dosimetry near tissue inhomogeneties
(Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2005., 2005.) İşbakan, Fatih.; Ülgen, Yekta.
The primary goal in this study was to investigate the three dimensional dose distributions, near the areas of tissue inhomogeneities, in Gamma Knife Radiosurgery with the normoxic gel dosimetry. Following irradiation, when scanned in MR and post processing the MR images, dose imparted to any particular point in the gel phantom can be calculated via the true T2 relaxation time at that point. In the neighborhood of air-tissue inhomogeneity in the head, electronic disequilibrium can lead to errors in dose calculated with the treatment planning algorithms that presume the head as a homogeneous media. Two experiments were designed to investigate the inhomogeneity effects in the Gamma Knife radiosurgery: one experiment simulating the volume near the auditory canal cavity and, the other simulating the volume near the paranosal sinuses cavity. In the auditory canal cavity experiment, an identical balloon of a diameter of 16 cm with two corks placed on each side to represent the air cavities constitutes the inhomogeneous phantom. In the paranosal sinuses cavity experiment, a cylindrical cork is placed to represent the maximal sinuses. In both experiments, the homo geneous phantom is a spherical glass balloon filled with normoxic polymer gel. For dose calibrations, 100 ml vials filled with the same gel are irradiated at predefined doses, and the R2-dose calibration curve is extracted. Dose distributions are the results of a single shot, by using all 201 Cobalt sources, delivered to a known point in the phantoms. In the aspect of dosimetrical quality control, the Gamma Knife planning system predicted dose distribution is compared with the experimental results. In the homogeneous phantoms, the gel dosimetry calculated dose distribution is in good agreement with the GammaPlan predicted dose distribution. However, in the case of inhomogeneous phantoms, the dose distribution is spatially different and significant differences in dose levels are observed. The dose decrease near the air-tissue interface causes the overshooting of the dose by the GammaPlan. This underdosing effect can be essential for the lesions near tissue inhomogeneities. In the auditory canal cavity experiment, the diameter of the 50% isodose curves differ by 35% in the X axis and 1% in the Y axis for Z=105 mm axial plane; and by 39% in the X axis and 5% in the Z axis for Y=105 mm coronal plane in the inhomogeneous phantom as compared to the homogeneous phantom. In the paranosal sinuses cavity experiment, the diameter of the 50% isodose curves differ by 42% in the X axis and 47 %in the Y axis for Z=71mm axial plane; 42% in the X axis and 60%in the Y axis for Z=75 mm axial plane; 52% in the X axis and 70% in the Y axis for Z=79 mm axial plane respectively in the inhomogeneous phantom when compared to the homogeneous phantom. The dose decrease near the airtissue interface causes the Gamma Plan’s predicted dosage to be higher than that actually delivered. The resulting underdosing effect can be critical for the control of the lesions near tissue inhomogeneities.
3-D P wave velocity structure of Marmara Region using local earthquake tomography
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2013., 2013.) Işık, Sezim Ezgi.; Gürbüz, Cemil.
The 3D P wave velocity model of upper and lower crust of the Marmara Region between 40.20 - 41.20 N and 26.50 - 30.50 E is obtained by tomographic inversion (Simulps) of 47034 P wave arrivals of local earthquakes recorded at 90 land stations, 30 OBO stations and 14162 shot arrivals recorded at 35 OBO stations (Seismarmara Survey, 2001) between October 2009 and December 2012. We first obtained a 1D minimum model with Velest code in order to use it as an initial model for 3D inversion with 648 well located earthquakes located within the study area. We first developed a 1D model by VELEST code then used it as an initial model for 3D tomography. After trial 3D inversions we decided to create a more adequate initial model for 3D inversion. Choosing the initial model we estimated the 3D P wave velocity model representing the whole region both for land and sea. The results are tested by making Checkerboard Test, Restoring Resolution Test and Characteristic Test, and the reliable areas of the resulting model is defined in terms of RDE, DWS, SF and Hit count distributions. By taking cross sections from the resulting model we observed the vertical velocity change along profiles crossing both land and sea. All the profiles crossing the basins showed that the high velocities of lower crust make extensions towards the basin area which looks like the force that gives a shape to the basins. Under the north of the Central Basin and Çınarcık Basin high velocity zones appeared which look like resisting walls holding the north of the basins between 5 km and 15 km. The same is also observed under the southern Tekirdağ Basin between 5 km and 15 km. These extensions of lower crust towards the basins appeared with an average velocity of 6.3 km/s. These extensions might be the result of the deformation due the shear in the region and it is also interpreted that the development of these high velocities coincides with the development of the basins. Thus, both the basins and the high velocity zones around them might be resulted from the entrance of the NAF into the Marmara Sea when also a shear regime is dominated due to the resistance of the northern Marmara Region (Yılmaz, 2010). The seismicity is observed between 5 km and 15 km after the 3D location of the earthquakes. The locations of the earthquakes improved and the seismogenic zone is determined well, between 5 km and 15 km. The depths of the pre-kinematic basement and crystalline basement showed great differences under the sea. It is observed that the velocity under sea becomes compatible with land after 8 km.
3-D P-wave velocity structure beneath eastern Turkey applying local earthquake tomography (LET) method
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2005.) Teoman, Uğur Mustafa.; Türkelli, Niyazi.
Eastern Turkey is a seismically active region exhibiting a complex structure in terms of both tectonic and geologic· features. A temporary seismic network consisting of 29 broadband three-component broadband stations were installed in the scope of Eastern Turkey Seismic Experiment (ETSE) to address the important questions. Detailed and accurate evidences relevant to the crustal and upper mantle structure of the region were obtained using the seismic data collected in between October 1999 and August 2001. Results of the ETSE project had a considerable contribution to understanding and interpreting the tectonic evolution along with the seismicity of the region. In this study, local earthquake data from the ETSE project were used in order to determine the upper crust seismic P wave velocity structure of Eastern Turkey and the surrounding regions by three-dimens}onal (3-D) Local Earthquake Tomography (LET) method. As far as resolution is concerned, S waves were not included in this study due to strong attenuation, insufficient number of S phase readings and higher picking errors with respect to P phases. LET is the 3-D imaging process ofthe velocity structure of a target volume by using the travel time data of the earthquakes recorded within the seismic network in an active region. To provide accurate tomographic results, a high quality data set, initial hypocentral parameters and a minimum one-dimensional (1-D) velocity model that adequately represents the region are required. Initially, data compilation and earthquake locations were determined. Initial locations of 9*4 events were performed by HYPOCENTER algorithm using an initial 1-D velocity model, which was obtained from the previous studies in the region. Following the earthquake location procedure, higher quality events were selected in order to construct the 1-D minimum velocity model for the region. As a basic data selection criteria, events with azimuthal gap (GAP) ::; 200° and number of observations (P) ~ 8 were selected from the initial data set (6978 P-phase readings). 1-D velocity model was calculated by VELEST algorithm performing a simultaneous and iterative 1- D velocity inversion. New hypocentral parameters and station corrections were also calculated in addition to the minimum velocity model. Three different trial velocity models were used in order to construct an initial velocity model based on the results of a set of inversions with ten iterations and four calculation steps. Each velocity model were constructed in 0-42 depth range in accordance with the crustal structure of the region, however, accurate results were obtained down to~ 15-20 km due to the depth distribution ofthe events. The relocation of the earthquakes was performed by VELEST via the 1-D minimum velocity model and the relevant station corrections. In the final step, various stability tests were applied to check the resolution capability minimum 1-D velocity model. As a result of these tests, it was suggested that 1-D minimum velocity model adequately represented the region. After the derivation of the most appropriate velocity model, 3-D tomographic inversions were applied to the final data set. Events with GAP :::;; 180° and P > 8 were reselected from the data set. Number of events for the tomographic inversion reduced to 504 after applying this criteria (Total number of 6742 P-phase readings). 3-D tomographic inversion was iteratively and simultaneously performed by SIMULPS 14 algorithm using node-grid geometry for model parameterization. Considering the event-station distribution, a horizontal grid with 30x30 km grid spacing was chosen. In vertical direction, depth values taken from the 1-D velocity model were used. Modeling was made down to 42 km. Tomographic inversions with four iterations and two processing steps were initiated after determining the appropriate control parameters and the damping factor. At the end of these processes, 3-D P wave velocity model and the resulting hypocenters were determined. A significant reduction in data variance (- %50) and in residuals (-%50) was observed during these processes. In order to assess the solution quality and the resolving power of the 3-D model, tests with the synthetic data were performed. Critical parameters affecting the resolution estimates were calculated and mapped along with absolute velocities (Vp) and% perturbations relative to the 1-D initial velocity model in both horizontal and vertical cross-sections. Consequently, after the tomographic applications, the compatibility of the results with the tectonic and seismological features of the region were evaluated and also compar~d with the results of the previous studies in the region. The differences between the initial and the final hypocentral parameters were emphasized in various cross-sections. XV

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