Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü

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Preliminary seismic evaluation of highway bridges in Istanbul
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 1995., 1995.) Zülfikar, A. Can.; Yüzügüllü, Özal.
In spite of the considerable developments in bridge engineering in recent years, substantial damages of highway bridges in recent earthquakes, have lead to an increasing awareness on the seismic performance of bridges. Seismic vulnerability of a bridge can be defined as the potential of a bridge to sustain significant damage or collapse. The seismicity at the location of the bridge is essential in the determination of its vulnerability. Istanbul is one of the most crucial cities in Turkey due to its historical, industrial and commercial importance. The main objective of the current study is to establish an inventory for the highway bridges on the 01 and 02 peripheral routes and the corresponding link roads in Istanbul and evaluate their seismic vulnerabilities according to a certain screening procedure. Such a preliminary screening procedure contemplates only the technical aspects of the problem and does not include political and economic considerations. In the preliminary screening process, Structural characteristics of the bridge, Importance of the bridge as a vital transportation link, Foundation and site characteristics of the bridge, are taken into consideration. In addition to the above studies, truck loading testing and a detailed analysis on a typical representitive bridge are presented. The results of this investigation are to be considered as the essential and basic step for the maintenance and rehabilitation of the ,highway bridges in istanbul under a future seismic activity.
A review of the tectonics of the aegean region
(Thesis (M.S.)- Bogazici University. Kandilli Observatory and Eartquake Research Institute, 1998., 1998.) Komut, Tolga.; Küleli, H. Sadi.
The Aegean region is a remarkably deforming part of the Alpine-Himalayan orogenic belt, which has the highest seismic activity in Europe. An extensional deformation regime has led to subsidence of the continental crust over all the Aegean region behind the south Aegean consumption boundary. The region that is mainly under pure shear stress is an internally deforming part of the counterclockwise rotating (relative to Eurasia) Anatolian plate. To understand the tectonics and dynamic evolution of the region many geoscientists have collected numerous data and interpreted them. In the present study, all available data have been compiled into a unique database. For this purpose, as a first step, raw and processed information have been compiled and classified with their sources, date information and criticism of their accuracy and limitations. This step allows the comparison of similar types of study and data in order to· understand basic problems more clearly. As the second step, all interpretations of the studies are discussed and critically reviewed by considering associated data and methodology on a regional scale. The goal of the work is to determine the problems with highest priority, find the gaps in the database.
Determination of earthquake performance of Süleymaniye Mosque
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 1999., 1999.) Kaya, Samiye Mircan.; Yüzügüllü, Özal.
Built between 1549-1557 by the great Turkish architect Mimar Sinan and named after the legendary Ottoman Emperor Siileyman the Magnificient, the Siileymaniye Mosque is considered to be the masterpiece of the Ottoman architecture. It is a fact that the research studies carried out up today towards the determination of the earthquake performance of this masterpiece of Otioman-Turkish Engineering is very limited. Within the framework of research activities being carried out at the Earthquake Engineering Department of Kandilli Earthquake Observatory and Earthquake Research Institute for the important historic edifices which was initiated with the Hagia Sophia, the present study on Siileyrnaniye Mosque is aimed at the exploration of the earthquake performance and dynamic characteristics of the structure. The three dimensional finite element model of the structure previously prepared by A.Selahiye was refined.Non-destructive material tests were carried out in the mosque in order to determine the material characteristics.The data obtained from the tests were used in the study and as a further step, the effects of different materials were investigated.At this stage the effects of different boundary conditions were also combined in the study. The earthquake records obtained from the strong ground motion accelerometers previously installed on Siileymaniye Mosque were also analysed to obtain the natural vibration frequencies and to compare the resulting values with those obtained by other methods.As a last stage of the study, the analysis of the improved model under a scenario earthquake for istanbul was carried out.
Seismic performance evaluation of the Sadabat 1 (V3) viaduct
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2002., 2002.) Önem, Göktürk.; Aydınoğlu, M. Nuray.
Sadabat V3 was designed in the late 1980's as a connector highway bridge in conjunction of Okrneydam and Hastal on ball-Sakarya motonvay route, which is a major component of the transportation system of Istanbul. The bridge shows some typical examples of old seismic design philosophy such as low level of design forces and lack of modem ductile detailing. Based on the visual inspection, any detrimental effects such as cracking or spalling of cover concrete due to corrosion could not be observed. Generally, it can be say that current condition of the bridge is good. The bridge is evaluated as a critical bridge because of the location on major traveled route. The bridge is expected to remain functional immediately following a destructive earthquake. Seismic performance of the bridge has been assessed by using nonlinear time history analysis and pushover analysis. At the end of the analysis, deformation demand determined fi-om the analysis has been compared with the predetermined component deformation capacity to obtain whether the bridge provides expected performance. Analysis shows that elastomeric; bearings, particularly located on flexible intermediate piers have insufficient displacement capacities in transverse direction to remain elastic. Displacement ductility of the piers are inadequate due to the poor detailing of the plastic hinge region. Because of the low ductility capacity, the piers are unlikely to tolerate cyclic displacement much exceeding yield in transverse direction. However, it can be concluded that the bridge response is essentially elastic in longitudinal direction.
Influence of modeling parameters on seismic response of steel moment resisting frames
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2003., 2003.) Gündüz, Ahmet Suat.; Aydınoğlu, M. Nuray.
The purpose of this work is to identify the building response to variations in modeling parameters and assumptions for the steel mid-rise buildings. The behavior and response of 9-story building in Los Angeles are studied. The building that was designed according to the UBC 1994 provisions was used in the analysis. Different models for this structure were developed and analyzed dynamically. The models investigated involved the use of centerline dimensions of elements, or clear length dimensions (rigid zone effect), nonlinear springs for the beam connections, and nonlinear springs for the panel zones. Also, P-delta effects on the system response to the ground motions were investigated. Nonlinear time-history analysis was used to assess the performance of buildings subjected to strong earthquake ground motions. The global (roof) and story level displacement demands, story drift ratio demands, beam and panel zone plastic rotation demands, location of plastic rotations of the systems, and the story shears were obtained by subjecting the six models to set of 10 ground motions representative of a 10150 (10% probability of being exceeded in 50 years) hazard level. The results are compared to evaluate the influence of modeling assumptions on the nonlinear dynamic response of the structures. As a result it is concluded that, the effect of analytical modeling is intrinsic to understanding the response of the structure. The overall effect of the different models can result in significant changes in the demands. Moreover, structure P-delta effects are found to have a potentially severe influence on the response of steel moment resisting structures.
Calibration of various magnitude scales in Turkey using broadband data
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2003., 2003.) Görgün, Ethem.; Aktar, Mustafa.
The local magnitude, ML, for earthquakes of Western Turkey and surrounding regions are determined using synthetic Wood-Anderson seismograms derived from newly available broadband recording from the Boğaziçi University Kandilli Observatory and Earthquake Research Institute (BU KOERI). Seismograms obtained from various types of broadband instruments are transformed to Wood-Anderson type using SAC (Seismic Analysis Code) routines and script files that are developed for this purpose. Wood-Anderson peak amplitudes are measured on 1560 three-component, obtained from 200 earthquakes in the distance range of 8 to 785 km. The earthquakes ranged from ML = 1.0 to 6.4 and were recorded at about 7 stations in the region. ML magnitudes can be obtained from the horizontal and vertical component. Scattering of each ML magnitude in each station is analyzed and their dependence on magnitude and distance are discussed. The station magnitude correction values are found. Some improvements are proposed for the magnitude determination procedures that are actually used at BU KOERI Seismological Laboratory. Finally we have compared our ML computations with the one obtained by other studies using different approaches or different waveform data. We have noted that our results agree well with ML magnitude determinations done at TUBITAK MRC, but deviates significantly from the MD calculations of BU KOERI Seismological Laboratory.
Seismic evaluation of pile groups
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2003., 2003.) Beker, Hüseyin Afşin.; Siyahi, Bilge.
In certain regions of the country, designing deep foundations to withstand seismic loading is a reality. Seismic loading of structures and foundations reach a critical state as the laterally applied force increases. Especially liquefaction is the major effect on laterally loaded piles. So firstly, the liquefaction potential of the site has been evaluated to make the best seismic assessment, as studied in the following chapter. Since, liquefaction potential analysis is highly complex and is based on numerous variables such as moment magnitude, epicentrical distance, PGA, thickness of soil layers, overburden pressure and duration of motion etcetera. Most of the potential analysis methods are empirically based on the statistical measurements of known past earthquakes. Thus, firstly the liquefaction potential analysis of the site is evaluated. by means of these methods. Secondly, the effects of liquefaction-induced lateral spreading on piles have been studied. Then, after a brief information is given about the structure, which is chosen as the model, the capacity estimations of the piles and the superstructure are acquired. Then soil, piles and the superstructure are modeled together in the SAP2000 computer program. Liquefaction-induced lateral spreading, spectral analysis (for TSC-98) and non-linear time-history analysis, with three different earthquake records (two of them are simulated), are examined. Finally, the results of the most critically forced structural elements are illustrated and then compared both by the structural capacity and between the different methods of solutions used. This study also gives a general knowledge about the sufficiency of the Turkish Seismic Code for buildings within the vicinity of an active fault line.
An application of the coda methodology for moment - rate spectra using three broadband stations in Turkey
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2003., 2003.) Eken, Tuna.; Türkelli, Niyazi.
In this study, an empirical magnitude calibration method developed by Mayeda et al., (2003) was tested by using both local and regional dista1tce earthquakes that occurred along the North Anatolian Fault Zone as well as throughout the broader region of Turkey. The method is based on source spectra that are derived from time-domain amplitude measurements of coda envelopes for 14 consecutive narrow frequency bands ranging between 0.02-8.0 Hz. Previous application of the methodology to earthquakes in the western United States and Dead Sea Rift regions (Mayeda and Walter, 1996; Mayeda et al., 2003) show that the moment magnitudes, Mw(coda), based on coda envelopes are significantly more stable and unbiased than conventional narrowband regional magnitudes which are obtained from direct phase measurements. Coda envelopes have a number of properties that make it a desirable choice for sparse station monitoring: 1) the coda envelopes are nearly insensitive to the radiation pattern and directivity of the earthquake source, 2) the coda is not as sensitive to lateral crustal heterogeneity because of the crustal averaging due to scattering, 3) clipped data can be used for fitting the envelopes after the clipped portion of the seismogram. During the calibration study, the empirical magnitude calibration method was applied in order to calibrate the three broadband stations, ISP, ISK and MALT in Turkey. Therefore, 182 common events, which mostly occurred along· the North Anatolian Fault zone near the Marmara region and recorded at both stations ISP and ISK, 137 common earthquakes, which are distributed over the broader region of Turkey recorded by stations ISP and MALT, were used. After applying the method to both pairs of datasets, consistent source spectra that were validated by equivalent seismic moment estimations from long period waveform modeling and derived moment magnitudes (Mw) were obtained. This study resulted in amplitude measurements that are a factor of 3 to 4 less variable than distance-corrected direct wave measurements (i.e., Pg, Lg, and surface waves). Upon comparing our coda-derived moment magnitude, Mw(coda)'s with those from long-period waveform modeling, Mw(waveform), a standard deviation of 0.17 for ISP-ISK and 0.14 for ISP-MALT station pair was 'Observed comparable to the results of previous studies (Mayeda and Walter, 1996; Mayeda et al., 2003). After calibrating the stations ISP, ISK and MALT, for some recent earthquakes such as the Piiltimtir earthquake of January 27, 2003, Mw = 6.1, the Urla earthquake of the Apri110, 2003, Mw = 5.7 and the Bingol earthquake of the May 1, 2003, Mw = 6.4, Mw(coda) values were estimated. The successful application of the method is remarkably important considering we are studying a much larger region with significant lateral complexities. With these calibrations we can extend the measurement of stable Mw to significantly smaller events, which could otherwise not be waveform, modeled due to poor signal-to-noise ratio.
Search of optimal crustal velocities using waveform modelling of local earthquakes
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2004.) Bekler, Feyza Nur.; Aktar, Mustafa.
One of the concerns of geophysicist during the last decade is to reduce the damage of earthquakes. As a result, seismic hazard studies have become an integral part of long term planning and mitigation. One approach is to calculate pe.ak ground acceleration (PGA) and use this scalar value in building design. However, this method has some disadvantages: it is very simple and it does not give spectral information related to the ground motion. Generally, the effects of faulting type, source mechanism, rupture directivity, asperities are ignored during the calculation of the PGA values. The study in this thesis contributes to the simulation of the ground motion by constructing optimal crustal velocity models based on 1- D synthetic seismogram modeling. For this purpose, different crustal models were generated using the discrete wave-number technique (Bouchon, 1981) and they have been tested by searching the best-fit between observed and synthetic seismograms. Waveforms from 5 earthquakes were analyzed in this study. The selected earthquakes have magnitudes larger than 3.5 and they are located along the main fault zone in the Sea of Marmara. The vertical, radial and transversal components were compared using the cross correlation coefficient between observed and synthetic seismograms. Crustal models having S-layers with fixed depths were used to calculate the synthetics for each selected event. First, the optimum P-wave velocities were searched within predefined velocity limits for each layer. Once the optimum P velocities were obtained, then the S wave velocities have been searched. In general a moderate level of fitting is obtained even for the optimal crustal models. Although numerically the correlation values are quite low, the shapes of the waveforms are roughly close to each other, at least for some selected parts of the total waveform. The degree of fitting is particularly low in the part of the waveform where the 3-dimentional effects in the crust start to dominate, such as the P-arrivals in the transversal component. The performance also degrades with the level of the local noise, which is known to be not negligeable at ISKB station. The use of a clever search algorithm that uses a feedback mechanism to guide the search in a selective parameter space and accelerates the convergence towards the optimum (such as steepest descent, etc) will allow the scanning of wider range of parameter (eg estimating the layer depths in parallel to velocities, etc). This will certainely improve the results.
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
Strain based performance evaluation charts for rectangular reinforced concrete columns in nonlinear analysis of structures
(Thesis (M.S.)- Bogazici University. Kandilli Observatory and Eartquake Research Institute, 2005., 2005.) Şadan, Oğuz Bahadır.; Aydınoğlu, M. Nuray.
Several methods and criterion are being used recently in determination of the deformations occurred in structural elements of a building and performance evaluation of these structural elements under earthquake motion using nonlinear analysis. Performance evaluation of structures under nonlinear earthquake loading using material strains, rather than the rotations as commonly used in other seismic codes (FEMA356, ATC40, EUROCODE8 etc.) is the basic subject of this study. Performance evaluation using material strains is also being mentioned in Chapter 13 of New Turkish Seismic Code Dra3. For performance evaluation using member strains, Strain Based Performance Evuluation Charts for rectangular reinforced concrete columns have been formed which bring easiness by omitting several cross sectional analysis in order to transform rotations into strains. These Strain Based Performance Evaluation Charts are intended to be very useful for the structural engineers who will practice nonlinear analysis using New Turkish Seismic Code in the future. However it should be noticed that these charts are formed only for rectangular reinforced columns with limited concrete-steel grade combinations. Therefore further studies should be performed for other combinations and beams.
Seismic performance evaluation of public school buildings in İstanbul metropolitan area
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2005.) Ekser, Burç.; Yüzügüllü, Özal.
Earthquake resistance of school buildings deserves special attention with respect to seismic safety because of their occupancy characteristics and their importance to immediate and long-term earthquake disaster relief and recovery efforts. The aim of the study is that the seismic performance evaluation of public school buildings in Istanbul. According to this, in Istanbul, three different types of projects are practiced and evaluated for public schools constructed due to different number of stories and different earthquake zones. besides, these kinds of porjects were analyzed in terms of 1975 and 1998 Turkish Codes. In addition to the seismic performance evaluation of public schools, a preliminary screening procedure was carried out in that study. To eliminate the losses caused by earthquakes, the earthquake resistance of the school building must be examined by quick and easy method which is Rapid Visual Screening Procedure prepared by Applied Technology Council. Actually, the method which was carried out, is classified the earthquake resistance resistance of the public schools and determined a detailed evaluation is required or not.
Paleoseismological studies on Düzce fault and geological data on the seismogenic sources in the vicinity of Düzce area
(Thesis (Ph.D.)- Bogazici University. Kandilli Observatory and Eartquake Research Institute, 2005., 2005.) Komut, Tolga.; Gürbüz, Cemil.
In 1999, two earthquakes ruptured the Northern Almaclk strand (NAIS) of the North Anatolian Fault that includes the Diizce and Aksu faults, producing surface rupture along the northern border of the Almaclk block. Paleoseismological trenching is performed at four sites along the Aydmpmar and Mengencik segments of four-structural-segmented Diizce fault. Six dated-events from eleven trenches that cross cuts the fault zone provided insights on its seismogenic behavior. The excavations from five trenches at three sites expose evidence for six earthquakes that occurred since B. C. 1740. A shallow of watertable, unfavorable trench materials and lack of financial support to perform 3-D trenching made the identification anu characterization of individual paleoearthquakes difficult. However, by integrating date constrains of events from the trenches that were performed along the Diizce fault including previous studies along the easternmost segment, a periodical recurrence model seems to be concordant with the radiocarbon age data. Seven serial surface-rupturing earthquakes including the 1999 Diizce event along the Diizce fault are defined. The model suggests that the Diizce fault is behaving as a single seismic segment at least for the last serial rupture in Holocene time. The additional two older events are showing an irregularity in the serial. Hitherto unrecognized earthquakes probably would eliminate this irregularity. A recurrence interval is estimated by also considering the two older earthquakes. This final sequential model suggests that 1999-type earthquakes repeat each 355±35 year (% 70 probability). The slip rate that was calculated from 350 cm average slir of the 1999 event and the recurrence period is about 9.5±1 mmlyr having % 70 probability. This value is in agreement with geodetic measurements (10 mmlyr) from independent studies. Because short time has elapsed since the 1999 earthquake that occurred along the Diizce fault, the Diizce fault does not appear to have an important seismogenic potential in near future. The Diizce plain is one of the major basins of the Marmara region. There is no active faulting excluding Diizce and Aksu faults that is detected in the basin and surrounding borders according to this study. In addition to this pull-apart and then continuing active formation of the Diizce basin hypothesis is not validated by rigorous data. Therefore, considering these data, it may be suggested that Diizce area is not under a severe seismogenic threat for very near future.
The analysis of 2003 Saros earthquake sequence, North Eastern aegean region and a calibration study of surface wawe magnitude (Ms)
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2005.) Mutlu, Ahu.; Karabulut, Hayrullah.
This study includes works on two different topics. In the first part, we analyzed the aftershock activity following Mw=5.8, 6th July 2003 Saros earthquake. The activity took place along the axis of the Saros gulf between the depths of 8 km and 20 km. The mainshock occurred at a depth of 17.5 km on the continuation of the North Anatolian Fault Zone (NAFZ) in the Gulf of Saros. Focal mechanism of the mainshock and largest aftershocks are almost pure right lateral strike slip with minor normal faulting. Strikes of the fault mechanism solutions are aligned with the axis of Saros depression. in the second part of this study, three different surface wave magnitude (Ms) formulae, Prague, Herak and Herak and Modified Prague formulae were used to determine Ms for earthquakes in and around Turkey between the years 1997 and 2004, recorded at local and regional distances. The results of three Ms formulae with different correction factors were compared. It was concluded that Prague formula and Modified Prague formula produce significantly distance dependent estimates while Herak and Herak formula has no significant distance dependency and more robust Ms values. It was also observed that Herak and Herak formula has better correlation with Moment magnitude than the other two formulae.
Relocating earthquakes by hypodd in Cınarcık basın and surrounding
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2006.) Bulut, Fatih.; Aktar, Mustafa.
We relocated part of aftershock activity in <;marclk Basin and surrounding that are associated with the 1999 izmit Earthquake Mw 7.4. We used double difference relocation algorithm (Waldhauser and Ellsworth, 2000) to relocate the aftershocks. The data set was obtained by a temporary seismic network deployed by Bogazi9i University, Kandilli Observatory and Earthquake Research Institute, LGIT (Grenoble) and IPGP (Paris) 10 days after the mainshock (Karabulut et al., 2002). For a better station coverage, additional data set was obtained from a network operated by TUBITAK Marmara Research Center. Differential travel times were calculated using both arrival time readings and waveform cross correlation method. We relocated 1550 of the aftershocks and interpreted the results by classification into three main clusters, namely, Tuzla, Y alova and Central Cluster. Tuzla Cluster is located in the northern scarp of the <;marclk Basin and shows events that are linearly oriented in NW-SE direction. The depth section of this cluster indicates a vertically dipping activity,. The linear trend might imply a secondary strike-slip faulting parallel to the main one. However, the earlier fault plane solutions do not confirm this statement. Y alova Cluster contains a well-developed aftershock activity that is located beneath the north of the Armutlu Peninsula. The depth section of this activity reveals a well defined linearly dipping characteristic which is plunging to the Iiorth with an approximate angle of 56°. The orientation of the seismicity is roughly EW and therefore parallel to the main rupture of 1999 izmit Earthquake. The Central Cluster traverses the total length of the Gulf of izmit and extends into the <;marctk Basin linearly with the orientation of E-W direction. It corresponds to the continuation of the main rupture of 1999 Izmit Earthquake to the west of the Hersek Peninsula. The relocation results obtained by HypoDD reveal seismicity patterns in a more clarified manner, provide more convincing data for models that were proposed before and fmally imply new seismological ideas about the Eastern Marmara.
Investigation of failure modes and mechanisms of Alibey Earth Dam by solid-fluid coupled nonlinear dynamic finite element simulation
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Parker, Ahmet Alper.; Siyahi, Bilge.
In this study, earthquake resistance of Alibey Earth Dam was investigated. Darn was modeled with four node plane-strain finite elements and displacement-pore pressure coupled finite element analyses were performed. Nonlinear material models such as pressure dependent and independent multi yield materials were implemented during the analyses. Transient dynamic finite element analyses were performed with Newmark method. Newton-Raphson solution scheme was adopted during the solution of the equations. Liquefaction and/or cyclic mobility effects were considered during the analysis. For the finite element analyses OpenSees (Open System for Earthquake Engineering Simulation) framework was adopted.
Seismic anisotropy and mantle flow beneath Turkey
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Polat, Gülten.; Türkelli, Niyazi.
In this study, SKS and SKKS phases have been used for the analysis of shear wave splitting in order to investigate polarization anisotropy in the upper mantle beneath Turkey. To determine the shear wave splitting parameters (fast polarization direction and delay time), we have used teleseismic waveforms obtained from 21 broadband stations in Turkey. Shear wave splitting measurements are very important in determining the role of mantle flow in the geodynamics of the African-Arabian-Eurasian collison. The collision of the Arabian and African plates with Eurasia dominates the tectonic framework of the Eastern Mediterranean and Middle East (e.g., McKenzie, 1972; Jackson and McKenzie, 1988). The leading edge of the African plate is being subducted along the Hellenic trench at a higher rate than the relative northward motion of the African· plate, required that the trench moves southward relative to Eurasia proper (e.g., Sander and England, 1989; Royden, 1993). There are two adjacent subduction zones in the region: The Hellenic arc to the west and the Cyprian arc to the east. The Hellenic arc is characterized by a relatively steep, retreating subduction, whereas the Cyprus arc appears to involve a shallow subduction with two major seamounts (the Eratosthenes and Anixamander) impinging on the trench (Kempler and Ben-Avraham, 1987). Extension behind the Hellenic arc is arc-normal, whereas extension behind the Cyprus arc appears to be arc-parallel. Our results in Central Anatolia basically exhibits a NE-SW fast direction, while in Eastern Anatolia we have found a NE-SW fast direction and lag time consistent with the results obtained from temporary broadband stations of the eastern Turkey Seismic Experiment project within the Anatolian plate (Sandvol, 2003). These observations indicate that the anisotropic fabric could be relatively uniform throughout the upper mantle beneath the Anatolian plate. However, in the western Anatolia we have found a N-S fast direction that shows consistency with the directions of lithospheric extension inferred from GPS data. We have also found some evidence of trench parallel mantle flow as inferred from our results and those of Hatzfeld et al. (2001). Given the thin and hot lithospheric mantle beneath Turkey, it is unlikely that any of the observed anisotropy can be attributed to "frozen" or "fossilized" LPO induced splitting. Therefore, we believe that these observed changes in splitting reflect the variations in the asthenospheric flow along the AfricanAnatolian plate boundary.
A tomographic image of the fault zone on the north anatolian fault
(Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Afacan Ergün, Tuğçe.; Karabulut, Hayrullah.
During the fall of 2003, seismic data were collected in the eastern Marmara Region on the North Anatolian Fault Zone near izmit rupture zone by a controlled source experiment. The fault was clearly exposed on the surface and the thickness of the sediments in the basin is expected to be greater than several hundred meters. The data were acquired along a 1.2 km long nmih-south profile with a total of 50 recorders equipped with 4.5 Hz geophones. 3-component geophones were used near the fault zone to detect trapped waves. The shot spacing was 5 m and receiver spacing was varying from 1Om to 20m. More than 180 shots were fired using a vibroseis. Data were recorded continuously with 1OOHz sampling rate. . This study is a step towards a determination of a shallow P wave velocity structure on the NAFZ near izmit rupture. We applied regularized inversion technique to the first arrival travel times. More than 6500 picks from 129 shot-gathers were used in the analysis. A shallow P wave velocity image (<200m) from travel time tomography was obtained in the izmit basin. The results indicate a fault zone of approximately 100 m thick. A velocity contrast was detected between the fault zone and surrounding blocks. The P wave velocity on the southern block varies between a range 1.4 - 1. 7 km/s and 1. 7 - 2.0 km/s on the northern block the velocity decreases to 1.4 km/s within the fault zone. 3-component recordings and fan shots indicates the presence of the fault zone consistent with the . tomographic image. Previous seismological studies in the region also show that the thickness of the fault zone is on the order of approximately 1OOm.
Seismic evaluation of Bolu viaduct 1
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake research Institute, 2006., 2006.) Candan, B. Tolga.; Aydınoğlu, M. Nuray.
A thesis is presented on the seismic evaluation of a viaduct using non-linear analysistechniques. The Bolu viaduct is a 2-3 km long seismically isolated structure with two parallelbridges each with a span length of 39.2 m and pier height of maximum 49 m that was nearly complete when it was struck by the 1999 Duzce earthquake in Turkey. With the design basedon AASHTO standards, it suffered complete failure of the seismic isolation system andnarrowly avoided total collapse due to excessive superstructure moment. After investigationsthe retrofit of the viaduct had been decided due to the study carried out by Michele Calvi and J. Nigel Priestley. This thesis concentrates on the retrofitted structure of Viaduct 1 by non-linear time historyanalysis.
Near shore bathymetric and topographic surveys in Marmara Sea
(Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Germen, Emine Öner.; Özener, Haluk.
Hydrographic Survey is the SCIence which deals with the measurement and description of the physical features of bodies of water and scientific mapping of the sea bed for navigation while bathymetric survey is related to topography of seafloor. The difference between land surveying and bathymetric survey is not being able to see the sea surface during observations, so collected data entirely rely on remote measurements. Early tools used at very beginning were very slow and eventually they replaced by modem techniques such as optical systems, acoustic and satellites. Each method is appropriate for different applications, for instance manual techniques can be preferred at construction applications while aerial photography may be suitable method in extremely shallow water. Thus, different techniques are explained according to surveying type. In addition to depth values, one must define also the point position that is distance measurement. There are several ways of distance measurement for different purposes. On the other hand all vertical and horizontal data have a meaning when they represented in a way that in common use. Coordinate systems are used to display measuring data in an understandable form. Consequently, depth measurement, point positioning and mapping are main stages of bathymetric survey and they thoroughly explained in this thesis with an example study. Living in country of which three sides are sea, it is inevitable solution to benefit from water resources for transportation. Water resources of the world compared to terrestrial resources are offering economical solution for all types of transportation for comfort and speed. For this reason The Marmaray Project which is a rail line project between the European and Anatolian sides of Istanbul, linking two continents by an under Bosporus tunnel, undertaken to meet the transportation demand of Istanbul City. Application section oftms thesis is a part ofthat significant project.

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