Jeodezi Anabilim Dalı

Jeosantrik dik ve coğrafi koordinat dönüşüm yöntemleri

Günümüzde GPS ölçüleri, hassasiyet gerektiren mühendislik ölçmelerinde ve yersel jeodezik referans ağlarına altlık teşkil edecek WGS84, ITRS ve ETRS koordinat sistemlerinin oluşturulmasında yoğun olarak kullanılmaktadır. Jeosantrik kartezyen koordinatlardan (x, y, z) elipsoid coğrafi koordinatlarının (B, L, h) karşılıklı hesabı, sıkça kullanılan jeodezik hesaplamalardan birisidir. Ülkemizin deprem kuşağı içinde bulunması nedeniyle jeodezik referans noktalarının hassas belirlenmesi gerekir. Ayrıca nokta sayısının fazla olduğu projelerde dönüşüm algoritmasının işlem hızı, yazılımda tercih sebebidir. Bu nedenlerden dolayı birçok yöntem geliştirilmiştir. (B, L, h) dan (x, y, z) hesabı ortak olup, ters dönüşüm hesabı için oldukça farklı yöntemler mevcuttur. Bu çalışmada; (x, y, z) koordinatları verilmişken (B, L, h) hesabı için geliştirilen farklı 27 yöntemin çözüm algoritması incelenmiştir. Enlemin ve elipsoid yüksekliğinin arasında artan değişken alınıp diğer elemanların sabit tutulmasıyla, yöntemlerin enlem ve yükseklik değişimine göre doğrulukları incelenmiştir. Ayrıca, yöntemlerin işlem zamanları da belirlenmiştir. Uygulama sonucunda, üç karşılaştırma kriterlerinde en hassas sonuçları veren yöntemler önerilmiştir.

Antalya-I (1935-1977) ve Antalya-II (1985-2005) mareograf istasyonlarında deniz seviyesi değişimlerinin araştırılması

Deniz kıyısına sahip ülkelerde pratik ve bilimsel amaçlar için işletilen mareografistasyonlarında yapılan deniz seviyesi ölçüleri, oşinografik uygulamaların yanı sırajeodezi alanında da yaygın olarak kullanılmaktadır. Deniz seviyesi, iklimsel (basınç,sıcaklık, rüzgâr vb.), yörüngesel salınım (Ay ve Güneşin periyodik çekim etkileri),buzulların erimesi ve tektonik hareketler gibi etkenler nedeniyle sürekli bir değişimhalindedir. Geçen yüzyılda küresel deniz seviyesinin 10-20 cm yükseldiği ve yükselişinbu yüzyılda 40-60 cm olacağı tahmin edilmektedir. Bu tahminler doğrultusunda denizkıyılarına sahip ülkelerde kıyı hattındaki yerleşim alanlarının sular altında kalma riskisosyoekonomik açıdan önem taşımaktadır. Deniz seviyesi değişimlerinin belirlenmesi,ülke düşey kontrol ağlarının datumu açısından da önem arz etmektedir.Bu çalışmada Antalya-I ve Antalya-II mareograf istasyonlarının bilimsel yöntemlerlekalite kontrolü yapılmış saatlik deniz seviyesi verileri kullanılarak mevsimsel ve uzundönemli deniz seviyesi değişimleri araştırılmıştır. Mevsimsel (yıllık ve yarım yıllık)değişimler ile ortalama deniz seviyesi ve hızı, matematik modeli harmonik bir fonksiyonolan eşitlikle, En Küçük Kareler Yöntemine göre hesaplanmıştır. Antalya-I ve IImareograf istasyonlarının ayrı ayrı ve de her iki istasyonun birleştirilmiş verilerinin analizedildiği bu çalışmada Antalya-I (1935-1977) mareograf istasyonu ortalama deniz seviyesihızı 1.00 ± 0.3 mm/yıl, Antalya-II (1985-2005) mareograf istasyonu ortalama denizseviyesi hızı 4.4 ± 0.7 mm/yıl olarak tespit edilmiştir. Her iki istasyonun birleştirilmişverileri ile yapılan hesaplama sonucunda ise 1935-2005 dönemine ait ortalama denizseviyesi hızı 0.2 ± 0.1 mm/yıl olarak belirlenmiştir.Anahtar Kelimeler: Mareograf istasyonu, deniz seviyesi değişimleri, gelgit, trend,harmonik analiz.

Eğik kenar-eğik kenar ve düşey açıların ölçüldüğü nirengi ağlarının üç boyutlu dengelenmesi

Farklı yüzeylere sahip hedeflerin konumlarının belirlenmesinde reflektörsüz ölçmelerin doğruluk analizi

Bu çalışmada; farklı yüzeylere sahip materyallere total station aletleri ile reflektörsüz ölçüler yapılarak, doğruluk analizlerinin incelenmesi amacıyla bir çalışma gerçekleştirildi. Hedeflerin reflektörsüz ölçmelerinin yapılabilmesi için öncelikle bölgedeki etkin yapı stoku ve yaygın olarak kullanılan materyallerin cinsi ve renkleri değerlendirildi. Böylece ilgili bölgelerde (sivil yerleşim ve sanayi bölgeleri, tarihi ya da eski binaların ağırlıklı olduğu alanlar, vb.) saha çalışmaları yapılarak uygun materyaller belirlendi. Saha çalışmaları ile belirlenmiş olan bu veriler kapsamında 18 çeşit materyal (beyaz boyalı ahşap, gri boyalı ahşap, sarı boyalı ahşap, kırmızı boyalı ahşap, mavi boyalı ahşap, pürüzsüz ahşap, pürüzlü ahşap, kahverengi plastik, beyaz plastik, granit, beyaz mermer, gri, mermer, tuğla, beyaz beton, turuncu beton, sarı boyalı metal, gri boyalı metal, metal) kullanıldı. Reflektörsüz ölçü özelliğine sahip total stationlar (LEICA TS16, Spectra Focus 8) ile ilk olarak, belirlenen yaklaşık mesafelerde(50,100,200,400m) reflektör ile ölçüler yapılarak referans mesafeler belirlendi. Ardından aletler, daha önceden özel olarak tasarlanmış tutturma aparatı yardımıyla hedef yüzeylere yönlendirilerek reflektörsüz mesafe ölçüleri yapıldı. Reflektör kullanılarak gerçekleştirilen referans mesafe ölçüleri ile reflektör kullanmadan gerçekleştirilen mesafe ölçüleri arasındaki karesel ortalama hata değerleri hesaplanarak karşılaştırıldı. Çalışma kapsamında hedef yüzeylerin malzeme türü, rengi, yüzey dokusu, boyalı olup olmaması, hedef yüzeye lazer ışınının geliş açısı gibi etkenler ölçü değerlerini etkilediği gözlenmiş olup, bu etkilerin her biri için ölçü değerleri ve değerlendirmeleri yazılı ve görsel olarak hazırlandı. Ayrıca ölçüyü etkileyecek dış etkenler (sıcaklık, basınç, nem, güneş ışının gelişi açısı vs.) ölçü süreci boyunca incelendi ve veriler kayıt altına alındı. Son olarak istatistik programı olan STATA programında ele alınarak tüm ölçü değerlerinin birbirlerine göre lineer doğruluk analizleri gerçekleştirildi. Çalışma sonunda; farklı renk yüzeylerine sahip hedeflerin mesafe ölçüleri üzerinde önemli etkiye sahip olduğu ortaya çıktığı, hedef yüzeye gelen ışının geliş açısı değiştikçe karesel ortalama hatanın değiştiği, ölçü mesafesi arttığında (200m sonrası) hatanın arttığı, farklı yüzey dokusuna sahip hedeflerin hata oranlarında farklılıklar olduğu, hedef yüzeyin boyalı olup olmaması ölçü sonuçlarını etkilediği ve iki ölçü aletinin mesafe ölçüleri ile hesaplanan karesel ortalama hataları arasında farklılıkların olduğu gözlenmiştir.

Doğu anadolu fayı güneybatı bölümünün mekansal ve zamansal sismik tehlike analizi

Türkiye is one of the most seismically active regions in the world due to its location at the intersection of the Eurasian, Arabian, and African tectonic plates. The country's tectonic regime is primarily governed by two major strike-slip fault systems, namely the North Anatolian Fault (NAF) and the East Anatolian Fault (EAF). On February 6, 2023, southeastern Türkiye experienced a devastating earthquake doublet, with moment magnitudes of 7.8 and 7.6, occurring nine hours apart along different segments of the EAF system. These events caused widespread destruction across 11 provinces, affecting millions of people and significantly altering the stress regime of the region. This study investigates the seismic behavior of the southwestern part of the EAF system before and after the 2023 earthquakes to understand the seismic hazard potentials. To achieve this, a combined approach was adopted involving Coulomb stress modeling, b-value analysis, and geodetic deformation assessment. Coulomb stress change calculations were performed to evaluate stress transfer and potential triggering in adjacent fault segments. In addition, the b-values, derived from the Gutenberg-Richter frequency-magnitude relationship, were used to detect spatiotemporal stress accumulation and release zones, with additional sub-period analysis revealing the impact of the 2023 events and background seismicity of the region. To complement these two approaches, coseismic deformation was analyzed using the InSAR technique, observing displacement patterns across the affected region. Additionally, strain rate fields were reviewed from regional GPS data to identify areas of increased tectonic stress. By integrating these geodetic and seismological datasets, the study highlights overlapping regions characterized by high strain accumulation, low b-values, and positive coulomb stress changes. The convergence of these datasets contributes a comprehensive framework for understanding tectonic stress evolution and improving future seismic hazard assessments along the southern and southwestern parts of the EAF system.

Empirik koda normalizasyonu ve ınsar yöntemlerini kullanarak kaf'taki depremler için büyüklük tahminleri

This thesis presents an integrated seismological and geodetic study to improve earthquake source characterization along the North Anatolian Fault Zone (NAFZ), a region of high seismic risk and significant tectonic complexity. The primary objective is to resolve inconsistencies in regional earthquake catalogs by developing a homogeneous moment magnitude (Mw) catalog for events with magnitudes ranging from 3.5 to 6.0. To achieve this,the Coda Calibration Technique (CCT) that utilizes the stable, scattered energy of coda waves to derive robust source spectra, mitigating path and site effects common in tectonically complex areas, is applied. The calibration is fixed using independently derived Mw from moment tensor inversion for low frequencies and apparent stress (σA) from coda spectral ratios for high frequencies, resulting in a reliable, homogeneous Mw catalog. Second, for two specific events, the 23 November 2022 M w 6.0 Düzce and the 18 April 2024 Mw 5.6 Tokat earthquakes, we conduct Interferometric Synthetic Aperture Radar analysis using Sentinel-1 data. The resulting coseismic deformation fields are modeled using an elastic dislocation formulation to invert for fault slip distribution, providing independent, geodetically-derived Mw estimates that validate the seismological results. A key finding of this study is the evidence for non-self-similar source scaling in the NAFZ; apparent stress is observed to increase with seismic moment, suggesting that larger earthquakes radiate energy more efficiently than smaller ones. Furthermore, the derived apparent stress values are systematically lower than in other active tectonic regions, indicating a potentially low-stress, low-seismic-efficiency environment for the fault zone. This integrated, multi-physics framework not only produces a critical, homogeneous Mw catalog for improved seismic hazard assessment but also provides fundamental new insights into the earthquake rupture physics of the NAFZ.

Earthquake cycle of the North Anatolian fault along the rupture zone of the august 17, 1668 great Anatolian earthquake

In this study, we investigated the earthquake cycle along the rupture zone of the August 17, 1668 Great Anatolian Earthquake (M8.1) combining GPS measurements and earthquake records. The 1668 M 8.1 earthquake ruptured 450 km section of the NAFZ. Based on the historical and paleo earthquake records, we detected three complete and one incomplete earthquake cycles since 1254. We elaborated on elastic rebound theory investigating the creeping and the locked stages of the individual fault segments along the NAFZ. We combined all available GPS measurements and modeled them using arctangent approach to simultaneously estimate segment-based slip rates and locking depths. Slips rates are then used to estimate preliminary inter-seismic slip storages assuming fully locked fault segments right after the mainshocks. The misfits between co-seismic slips and preliminary inter-seismic slip storages of historical earthquake indicate that the fault does not store slip for a while after a major earthquake. Our analysis showed that there is a partitioning of the creeping and locked stages both in time and space. Only along one the segments, the 1943 (M7.7) rupture zone, exceptionally 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) rupture zones, 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 different earthquake potentials as they have distinctive creeping/locking rates despite the fact that they are exposed to similar deformation rates (ranging between 19.5±0.5 – 24.2±0.3 mm/y). In this frame, the NAFZ is currently able to generate M7+ earthquakes along the 1939 (M7.9), 1943 (M7.7), and 1944 (M7.4) rupture zones, M6.5+ earthquakes along the 1942 (M7.1), 1957 (M7.0), 1967 (M7.2), and 1999 (M7.5) rupture zones, and an M6+ earthquake along the 1999 (M7.1) rupture zone. Our results show that the GPS-derived slip rates systematically accelerate from the east to the west. GPS-derived locking depths do not demonstrate a systematic trend. They are deeper along the central NAFZ and shallower along the other sub-segments. 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 the earthquakes systematically migrate to the west outlining a decelerating behavior.

Analysis of the surface deformation caused by the Hatay earthquake on february 20, 2023 with insar technique

The tectonic of Türkiye are mainly shaped by the movements of the surrounding tectonic plates. The Arabian and African plates move northward against the Anato- lian and Eurasian plates, influencing the tectonic dynamics of T¨urkiye. The Anatolian Plate is moving predominantly to the west and southwest, and this movement is ac- commodated by the North Anatolian Fault Zone (NAFZ) with right-lateral strike-slip motion and the East Anatolian Fault Zone (EAFZ) with left-lateral strike-slip motion. Further south, the movement continues along the Dead Sea Fault Zone (DSFZ) in southeastern T¨urkiye. On February 20, 2023, an earthquake with magnitude of Mw 6.3, known as the Hatay earthquake, occurred at the intersection of the EAFZ, the DSFZ, and the onshore extension of the Cyprus Arc, two weeks after the Kahraman- mara¸s earthquakes of February 6, 2023. The DSFZ, trending north-south, originates south of the EAFZ and extends across Syria, Lebanon, and Israel. Although the frac- ture segment near Hatay is not as active as the northern parts of the EAFZ, it has experienced significant seismic activity in the past. Interferometric Synthetic Aperture Radar (InSAR) method was used on Sentinel-1 data to assess the deformation caused by the Hatay earthquake. The TopsApp module within the InSAR Scientific Com- puting Environment (ISCE) software was utilized to analyze the SAR images acquired before and after both earthquakes. This analysis focused on obtaining interferograms of the co-seismic deformation in the Hatay region from both ascending and descending satellite tracks. Our data analysis indicates that the maximum amount of deformation caused by the 2023 Hatay earthquake is ∼ 17 cm.

Evolution of earthquake hazards in Izmir in response to M4+ earthquakes

In this study, we investigated the evolution of earthquake hazards in İzmir (Turkey), the city accommodating the third highest population in Turkey in response to M4+ size earthquakes analyzing Coulomb stress change on all potential receiver faults in the target region. The city is located in western Turkey, which falls under Aegean tectonics, which leads to very high earthquake activity in the region. Fault segments with increasing Coulomb stress host high earthquake activity verifying that M4+ earthquakes prepone the generation processes of some earthquakes. In contrast, fault segments with decreasing Coulomb stress host earthquake silence verifying that M4+ earthquakes postpone the generation processes of some earthquakes. Hence, M4+ earthquakes played a critical role in the occurrence of the 2021 Samos Earthquake (M 6.92) as they increased the Coulomb stress above 0.1 bars along its rupture plane. To sum up, our results show that Coulomb stress change generated by M4+ earthquakes plays a critical role in earthquake activity in the vicinity of İzmir, Turkey.

Tuzla Fayı'nın (İzmir/Türkiye) sismo-jeodezik karakterizasyonu: Fay kinematiği ve deprem potansiyeli

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 fattened 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 fi 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. Differential slip rates range between 1.00 to 2.00 mm/yr. Magnitude calculations were done for Tuzla Fault and its segments separately. 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.

Yersel lazer tarama tekniği ile İstanbul kara surlarının deformasyonunun belirlenmesi

Historical buildings are an integral element of human civilization and they play a big part in cultural heritages for the descendants. Turkey, as being the cradle of civilizations, hosts very important and valuable structures. These structures are exposed to deformations for various reasons. Classical geodetic monitoring is a key approach for years to detect the deformation behaviors of structures. However, with the advanced technology, modern geodetic instruments replaced the classical geodetic instruments. Terrestrial Laser Scanner is built on the approach of acquiring a high-density point clouds, which represents X, Y, Z coordinates of the reflective surface. The case of Istanbul Land Walls has been chosen for this study due to its ~1600 years of historical value. In particular, two different towers of Land Walls having huge cracks on the front side of both structures is the motivation of this study. During this study, it happened an earthquake in Silivri offshore with the local magnitude (ML) of 5.8. Thus, there are 2 observations before and after the earthquake. In total, three independent measurements are made. Data obtained from scanning were compared in Cyclone 3DR software using Cloud-to-Cloud method of deformation analysis. Geometries of structures are defined with outputs found by point clouds; deformation progresses are scrutinized, and three-dimensional models are constituted. In conclusion, Terrestrial Laser Scanning technology is convenient to detect the deformations of historical structures with high capacity point clouds. The deformation maps obtained from comparing the point cloud data give a good structural information about the object by showing the current deformations and highlighting zones with possible future damage. It is thought that this study may provide a significant contribution to literature about not only protecting cultural heritage but also deformation studies.

Earthquake potential of the East Anatolian fault

This study aims to forecast magnitude of future strong (6.0≤ M <7.0) and major (7.0≤ M <8.0) earthquakes along the East Anatolian Fault Zone (EAFZ hereafter), which is a seismically active plate boundary between Arabian and Anatolian plates. In this context, we investigated segmentation of the EAFZ reviewing previous studies on structural variation zone and historical earthquakes. We analysed the combined GPS velocity field to obtain back-slips using steepest descent/gradient inversion method. The method projects GPS-derived back-slip rates onto the fault plane using Okada's quasi-infinite space model simulating elastic Green's functions to obtain on-fault slip deficit rates. Resulting slip deficit rates are used to estimate present-day slip budgets on each fault segment. We also analysed along-fault b-value distribution to verify if it can be used to differentiate between locked and creeping patches. Our results show that the EAFZ currently have a 1.51 m average slip. We suggest that the EAFZ is split into eight fault segments generating strong/major earthquakes. The January 24, 2020 Elazığ earthquake (M 6.8) ruptured the Sivrice-Pütürge segment verifying our segmentation model and magnitude forecasts for future earthquakes. We found no slip deficit accumulation observed on the Hacılar segment. Remaining six segments are able to generate three strong, three major earthquakes. Currently Karlıova, Kaleönü-Beyhan, Palu-Sivrice, Taştepe, Çelikhan-Erkenek, Gölbaşı-Pazarcık segments can currently generate M 7.0, M 6.9, M 7.1, M 6.8, M 6.9, M 7.4 earthquakes, respectively. Karlıova, Palu-Sivrice, Taştepe, Gölbaşı-Pazarcık segments currently have the potential to generate previous strong/major earthquakes they hosted. We observed a reverse correlation between slip deficit rates and b-values verifying that b-value can be used to discriminate locked and creeping fault segments.