LEE- Jeodinamik-Yüksek Lisans

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http://hdl.handle.net/11527/19320

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  • Öge
    Artemia fecal pellet is an important paleoenvironment indicator in hypersaline lakes : A case study Urmia Lake (NW İran)
    (Graduate School, 2022) Sarı, Selma ; Mohammadi, Ali ; 708646 ; Geodynamic Programme
    Hypersaline lakes are dynamic sedimentary environments responding change in a complex pattern. The Urmia Lake in NW Iran (Azerbaijan area), is the second-largest hypersaline lake in the world. The lake is a hybrid terrigenous-biochemical sedimentary environment that completely shifted to an almost pure chemical sedimentary environment due to an extreme rapid water level fall in the last decades. Artemia urmiana, as a saline water shrimp, is the only animal living in Urmia Lake. Artemia fecal pellets are the major bio-chemical component of the lake sediments, recording the lake's hydro-chemical variation through time. For paleoclimate reconstruction of the Turkish-Iranian Plateau in the Late Pleistocene-Holocene, based on Artemia fecal pellets characteristics, we studied a 25 m long sediment core collected from the northwestern part of Urmia Lake in 2017. This research uses morphological, mineralogical, textural, biochemical, geochronological, and stable isotopic characteristics of Artemia fecal pellets along with the lithostratigraphy of the core to reconstruct paleoclimate and paleogeography of the lake in the Late Pleistocene-Holocene. In Urmia Lake sediments, fecal pellets are capsule shaped grains in silt to medium sand size. The frequency, size, shape, colour and surface morphology of fecal pellets were studied using a binocular, polarizing and scanning electron microscopes on 140 sediment sub-samples. Sub-samples were collected according to facies variations along the studied core. Correlations of sedimentary units with fecal pellets variations along the core we classified five lake level stages based on fecal pellets frequency and characteristics variation: Lake-level falling stage (2500-1472 cm depth) is mainly composed of coated grains, reworked shell fragments and diagenetic sulfate minerals with a minor amount of brownish broken fecal pellets; Lake-level low stand stage with lake floor exposure (1471-816 cm depth) has black, orange, and brown pellets, rounded diagenetic gypsum minerals with volcanic lithics and glasses admixed; Lake-level rising stage (815-611 cm depth) is dominated by sulfate minerals and the absence of pellets; Lake-level high stand (610-320 cm depth) is dominated by fresh cream-coloured pellets; and lake-level falling towards drying out stage (319-0 cm depth) is composed of evaporite minerals as a salt crust on lake floor. The radiocarbon ages of fecal pellets indicate that the 25 m lake sediment cover ~ last 50 kyr with some glacial and interglacial periods. The age-depth model indicates different sedimentation rate in different depth which are consistent with our identified sedimentary facies. The oxygen and carbon isotopic data variation along the core exhibit deeper part of the core is more dry and cold climate (glacial period) and the upper core is more humid climate (interglacial period). Overall, the stable oxygen and carbon isotopic composition are in agreement with determined sediment facies and lake level fluctuations.
  • Öge
    İstanbul-Şile kumullarının manyetik ve sedimantolojik analizi: Paleoçevresel çıkarımlar
    (Lisansüstü Eğitim Enstitüsü, 2022) Yıldırım, Cengiz ; Makaroğlu, Özlem ; 776787 ; Jeodinamik Bilim Dalı
    Kumullar sahip oldukları stratigrafik, manyetik ve kronolojik özellikleri ile Kuvaterner döneminde meydana gelen ortamsal (iklim, çevre) değişimlerle ilgili çıkarım yapılmasına imkân veren önemli çökel kayıtlarıdır. Bu çalışmada İstanbul'un Şile İlçesi'nin batısında bulunan Sofular Köyü'nün sahil kısmında yer alan falezler boyunca yüzlek veren 3 ayrı kesit boyunca paleosol ve kumul çökelleri incelenmiştir. Çevresel manyetik özellikleri analiz edilmiş ve Işık Uyarmalı Lüminesans (OSL) yöntemi ile tarihlendirilerek kronolojiler elde edilmiştir. Bir çökelim alanının karakteristik özellikleri tortunun bünyesine yansıdığından, ortamsal karşılaştırma amacıyla Passega Diyagramı çizilmiş olup, ortamsal anlamda kum ağırlıklı kesitler olduğu ve taneboyu analizi ile uyumlu olduğu görülmektedir. κlf (manyetik duyarlılık), ARM (Anhisteretik kalıntı mıknatıslanma), IRM (Eş-ısıl kalıntı mıknatıslanma) ve SIRM (Doymuş eş-ısıl kalıntı mıknatıslanma) gibi parametrelerin ölçümlerini içeren çevre manyetizması analizleri ile kesitler boyunca manyetik minerallerin yoğunluk ve tane boyu değişimleri incelenmiştir. Farklı derinliklerinde ani değişimler veya yüksek değerlerin ölçüldüğü bazı seviyelerde ölçülen yüksek manyetik duyarlılık ve kalıntı mıknatıslanma şiddetleri (NRM, ARM ve SIRM) kesit boyunca görece, manyetik minerallerin bu seviyelerde yoğunlaştığını açık olarak göstermektedir. Birinci ve ikinci kesitte çoğunlukla düşük olarak hesaplanan S-oranı bu iki kesitte üçüncü kesite oranla daha yüksek oranda yüksek koersiviteli manyetik minerallerin olduğunu göstermektedir. Yüksek HIRM değerleri de bu durumu desteklemektedir. Üçüncü kesitte elde edilen tane boyu analizleri bu kesit boyunca kil içeriğinin diğer iki kesite göre önemli derecede düşük olduğunu buna karşılık, kum içeriğinin en yüksek bu kesitte bulunduğunu göstermektedir. Diğer iki kesite oranla, üçüncü kesitte elde edilen düşük manyetik duyarlılık ve kalıntı mıknastıslanma şiddeti tane boyu analizi ile de desteklenen düşük kil içeriği ile ilişkilendirilmiştir. OSL analizlerinde çapraz tabakalı eolinitin hemen altında yer alan paleosol olan birinci kesitin yaşı 121.3±7.66 bin yıl, yine paleosol olan ikinci kesitin yaşı 54.94±3.77 bin yıl ve tamamı eolinitten oluşan üçüncü kesitin yaşı 139.1±22.46 bin yıl olarak belirlenmiştir. Birinci ve üçüncü kesitlerin denizel izotopik evre DİE 5, ikinci kesitin ise DİE 3'e karşılık geldiği görülmüştür. Bu veriler sahada buzullararası dönemde (DİE 5) kumul oluşumuna uygun iklim şartlarına sahip olduğunu göstermektedir. İkinci kesitin oluştuğu DİE 3'te yani 80 bin yıl önce başlayan buzul döneminin ortalarında bölgede toprak gelişimi için daha uygun ve kimyasal ayrışma için daha elverişli çevre koşullarının bulunduğuna işaret etmektedir.
  • Öge
    Age and significance of amphibolites in the bolu massif (İstanbul Zone, NW Turkey)
    (Graduate School, 2022-07-06) Demirkaya, İnal ; Topuz, Gültekin ; Wang, Jia-Min ; 602191003 ; Geodynamics
    The Bolu Massif represents the Late Neoproterozoic crystalline basement of the Istanbul Zone (NW Turkey), and is made up of two tectonometamorphic units which are separated by a major tectonic line. The lower tectonometamorphic unit comprises amphibolite-facies metamorphic rocks which are dominated by the migmatitic amphibolite and locally trondhjemite. On the other hand, the overlying tectonometamorphic unit comprises greenschist-facies mafic to felsic metavolcanic rocks intruded by a huge granitoid of Late Neoproterozoic age. This study deals with the metamorphic evolution of the underlying amphibolite-facies tectonometamorphic unit. The amphibolite-facies tectonometamorphic unit comprises migmatitic amphibolite (ca. 80% of the exposure area) and concordant to crosscutting trondhjemite sills/dykes/stocks (ca. 20% of the exposure area). Although this amphibolite unit was formerly interpreted to the crustal part of an ophiolite, rare earth element patterns and multi-element variation diagrams involving fluid immobile elements differ from the well-documented ophiolites. The geochemical features of these voluminous amphibolites are more consistent with those in intra-oceanic arcs and magmatic arcs. U-Pb dating of zircons from four trondhjemite samples and from three amphibolite samples consistently yielded ages of 255-260 Ma (Middle to Late Permian). Only zircons from one amphibolite sample defined a discordia with an upper intercept age of 554 ± 34 Ma (2) (Late Neoproterozoic-Cambrian). The geochronological data shows that the amphibolite-facies tectonometamorphic unit does not represent the Late Neoproterozoic basement of the Istanbul Zone. It is related to Late Palaeozoic to Late Mesozoic orogenic events.
  • Öge
    Investigation of late holocene period vegetation and climatic changes of Gölbaşi basin based on palynological analysis
    (Graduate School, 2024-06-12) Gökgöz, Dila Doğa ; Biltekin, Demet ; Eriş, Kürşad Kadir ; 602211001 ; Geodynamics
    The Gölbaşı Basin is located in Adıyaman Province, SE Türkiye and there are three lakes within the basin, namely Gölbaşı, Azaplı, and İnekli. This thesis focuses on the palaeoenvironmental and palaeoecological changes in the Gölbaşı Basin which is one of the most important wetlands in southern Anatolia. For the first time, and palaeoenvironmental reconstruction was performed through high-resolution palynological data covering the late Holocene (> 3019 cal years) in the basin. Fossil pollen and non–pollen palynomorphs (NPPs) provide a complementary assessment for environmental monitoring, such as vegetation and climate changes, agricultural preferences, deforestation phases, animal husbandry, land-use change, trophic states of wetlands, and prey–predator relationships in the ecosystem. Scope of this thesis, palynological analyses were performed on two sediment cores obtained from Lakes Gölbaşı (GLB-01) and Azaplı (AZP-03) during the fieldwork of the TÜBİTAK-121Y287 project carried by İTÜ EMCOL Applied Research Centre. Analyses and observations were performed in the microscope laboratory at the Eurasia Institute of Earth Sciences and sedimentology and geochemistry laboratories in the East Mediterranean Centre for Oceanography and Limnology (EMCOL) Applied Research Center. The chronology of the cores was established based on AMS radiocarbon dating. Additionally, 53 species and 13 families were identified within the pollen assemblages, and 83 distinct non–pollen types were classified based on their taxonomic characteristics. According to palynological data, the dominance of cultivated plants, anthropogenic plants, cereal types, mega herbivore indicators, and open vegetation indicator fungal taxa indicates that intense human activity occurred around Lake Gölbaşı and Lake Azaplı during the late Holocene. In the GLB-01 core taken from Lake Gölbaşı, the abundance of Poaceae increased from the upper part of the Glb-1 pollen zone toward the top of the core with slight fluctuations. The presence of cultivated species such as Juglans (walnuts), Olea (olive), and Pistacia (pistachio) indicates agricultural practices in the vicinity of Lake Gölbaşı at 1915 cal years BP. The drastic decrease in the abundance of Cedrus (cedar), which is a relict plant in Anatolia, is probably related to human activity in the Glb-1 pollen zone. At the transition of the Glb-1 and Glb-2a pollen zones, increasing arboreal species and lake levels are probably associated with humid conditions. Additionally, this phase is supported by algae and micro herbivore taxa. At 85 cm, the decrease in abundance of herbaceous communities and lake level suggest arid climatic conditions. Additionally, agricultural practices were probably affected by dry conditions during this time interval. In the middle of the Glb-2b pollen zone, increasing drought-tolerant Mediterranean xerophytes such as Quercus ilex- coccifera, and Pistacia indicate another dry period. The uppermost pollen zone of the GLB-01 core shows abrupt changes in the non–pollen assemblages, indicating important environmental alterations associated with deforestation. The dominance of Glomus (a mycorrhizal fungus) in the core suggests that erosion processes were active in the basin and were associated with some dry climatic conditions, anthropogenic influences, and probably seismic activity. At the bottom of the AZP-03 core taken from Lake Azaplı, with increasing deciduous Quercus, the humidity increases (>3019 cal years BP). This humid phase is also supported by algae taxa and the lake level change curve. In the upper part of the Azp-1 pollen zone, the decrease in the abundance of arboreal pollens such as deciduous Quercus, Pinus, and Cedrus and the presence of some NPP assemblages inhabiting dead wood and leaf litter indicate that the deforestation phase during the early Iron Age was accompanied by arid conditions. However, in the following pollen zones until the uppermost zone, an increase in Pinus represents the presence of secondary forests as a result of decreasing human pressure on the forests after the early Iron Age. Concurrently, the existence of cultivated and anthropogenic species and mega herbivore indicators prove that human activity has occurred in the area. The presence of Juglans (walnuts), which is a cultivated species in Anatolia, has spanned more than the last 3019 cal years in the vicinity of Lake Azaplı. The earlier emergence of Juglans compared to its eastern counterparts such as Lake Van and Lake Hazar, is possibly related to its geographic position which is situated at the intersection of the Eastern Mediterranean and Iran-Turan phytogeographic regions and earlier human activity in the area. The upper parts of the Azp-2b and Azp-1 pollen zones are represented by abrupt changes with decreasing numbers of arboreal plants and an increasing number of herbs, similar to Lake Gölbaşı. An increasing number of algae taxa, such as Pediastrum simplex, Pediastrum duplex, Pediastrum boryanum, Pediastrum biwae, Cosmarium sp., Spirogyra sp., Scenesmus, and Staurastrum sp., are related to nutrient enrichment as a result of freshwater input to the catchment area and human-induced pollution in the basin during the late Holocene. Moreover, the NPP of Rotifera eggs, Acari (oribatida), tintinids, and Cladocera species including Bosmina longirostris, among the microherbivores increased with the nutrient and algae enrichment in the GLB-01 and AZP-03 sediment cores. However, in the uppermost part of the cores, the occurrence of algal blooms is likely related to water level rise, changes in lake chemistry due to urbanization, and increased waste. Additionally, the classification of algae taxa based on trophic state showed that Lake Azaplı has more eutrophic conditions than Lake Gölbaşı in the uppermost pollen zones. Based on these findings, a palynological assessment revealed important environmental changes during the late Holocene in the Gölbaşı Basin. Further investigations are needed to better understand the ecological role of non–pollen palynomorphs and to establish their transfer functions. In addition, since the study area is a tectonically active basin, the ecological history of the region should be compared with palaeoseismological studies, together with the new chronology to be created with extra 14C dates.
  • Öge
    27 Eylül 2021 Girit depremi ve artçıları için derin öğrenmeye dayalı detaylı sismik kataloğun oluşturulması
    (Lisansüstü Eğitim Enstitüsü, 2024-06-26) Balkaya, Zeynep Nihal ; Özeren, Mehmet Sinan ; 602201009 ; Jeodinamik
    Helen Dalma Batma Zonu ve Girit'de son yıllarda arka arkaya 6 ve üzeri büyüklüklerde depremlerin sık olmuş olması bu çalışmanın çıkış noktasını oluşturmaktadır. 27 Eylül 2021'de adada meydana gelen Mw 6.0 büyüklüğündeki depremi ve sonrasındaki artçıları incelemek amacıyla bir katalog oluşturulmaya karar verilmiştir. Girit Adası ve Helen Dalma Batma Zonu çevresinde 26 Eylül 2021 ve 31 Ocak 2022 tarihleri aralığında gerçekleşen depremler için derin öğrenmeye dayalı bir dedektör ve faz seçici olan EQTransformer ve kaynak konumu için faz tespitlerinin tutarlılığına dayanan bir kod olan REAL kullanılarak hassas bir deprem kataloğu oluşturulmuştur. Sismolojide sismik aktiviteyi izlemek için pek çok adım kullanılır. Geçmişte manuel olarak gerçekleştirilen bu adımlar günümüzde faz gelişlerini tespit etmek için tasarlanan algoritmalarla otomatik olarak gerçekleştirilmektedir. Sürekli sismik veriler içinde sismik olayın başlangıç zamanını tanıma, P ve S dalgalarının varış zamanını belirleme sismolojide çok önemlidir ve veri kümelerinin çok büyük olması sismolojiyi derin öğrenme uygulamalarına çok elverişli hale getirir. 27 Eylül 2021'de Girit adasında Arkalochori yakınlarında ada içinde aletsel dönemde kaydedilmiş en büyük deprem meydana geldi. Aletsel büyüklüğü Mw 6.0 olan ve adadaki normal faylardan Kastelli Fayı yakınlarında meydana gelen deprem 1 ölüme ve adada hasara neden oldu. Ana şoku aynı gün içinde 4 ve üzeri büyüklükte birçok artçı şok takip etti. Ertesi gün 5.3 Mw büyüklüğünde en büyük artçı şok yaşandı ve ilk birkaç gün yüzlerce deprem meydana geldi. Bu çalışmada daha ayrıntılı bir katalog oluşturmak ve dolayısıyla artçı depremleri daha detaylı tesbit etmek amacıyla ada ve çevresinde yer alan Hellenic Unified Seismological Network'e ait HC, HI, HL, HT ve GE ağlarına ait yedisi ivmeölçer, biri kısa periyot ve yirmi geniş bant olmak üzere toplamda yirmi sekiz istasyondan gelen sürekli dalga formlu MiniSEED formatında olan veriler için derin sinir ağı temelli yapay zeka tabanlı bir deprem sinyali dedektörü ve P ve S faz seçici olan EQTransformer kullanıldı. Bu işlemden sonra ise REAL (Rapid Earthquake Association and Location) ile daha önceden EQTransformer ile seçilmiş olan P ve S fazları birbirleriyle ilişkilendirilerek depremler tesbit edildi. Girit'e ait 1 boyutlu hız modeli ile bu tesbit edilen depremlerin yerleri Hypocenter programı ile konumlandırıldı. Sonrasında depremlerin lokal büyüklükleri (ML) hesaplandı ve böylece 23°-28.5° boylam; 34.5°-36.5° enlemlerini kapsayan 128 günlük bir katalog oluşturuldu. Böylelikle NOA ve ISC kataloglarına göre çok daha hassas bir deprem kataloğu elde edildi. Çalışmada EQTransformer ile oluşturulan katalogda 23°-28.5° boylam; 34.5°-36.5° enlemlerini kapsayan 128 günlük zaman aralığında bulunan deprem sayısı 14958'dir. Aynı zaman ve koordinat aralığı için bu sayı NOA kataloğunda 6341, ISC kataloğunda ise 6360'dır. Sonraki tüm kıyaslamalar ISC kataloğu ile yapılmıştır. EQTransformer ile oluşturulan katalog ve ISC kataloğunun ortak olarak bulmuş oldukları deprem sayısı 4004'dür. Yalnızca EQTransformer ile oluşturulmuş olan katalogda bulunan deprem sayısı 10954'dür. Sadece ISC kataloğunda bulunan depremlerin sayısı ise 2356'dır. 2'den küçük depremleri bulmada EQTransformer'ın oldukça başarılı olduğu görülmüştür. EQTransformer ile oluşturulan katalogda 2'den küçük depremlerin sayısı 10724'dür. Bu sayı ISC kataloğu için 3316'dır. Adadaki deprem ve artçılarını incelemek amacıyla EQTransformer ile oluşturulan katalog 34.9°-35.5° enlem ve 24.8°-25.8° aralığında daraltıldı. Bunun sonucunda EQTransformerın bulmuş olduğu deprem sayısı 13325, aynı koordinatlarda ISC kataloğundaki deprem sayısı ise 4818 oldu. Bu depremlerin EQTransformer ile oluşturulan katalogda bulunanların 10035'i 2'den daha küçüktür. ISC kataloğunda ise 4818 depremden 2832'si 2'den küçüktür. 3'den büyük depremlerin her iki katalogda ortak olarak daha kolay yakalanabildiği görülmüştür. Ada içinde her iki katalogda ortak olarak bulunan deprem sayısı ise 3601'dir. Depremlerin derinlik dağılımına baktığımızda ise ağırlıklı olarak 0-10 km'de meydana geldiğini ve ilk 20 km'de olduğunu görürürüz. 27 Eylül 2021'de saat 6:17'de meydana gelen Girit adasındaki deprem çözülen odak mekanizma sonuçlarına göre 25.25° boylam ve 35.18° enleminde, 4.1 km derinlikte, doğrultusu 229°, eğimi 43° ve atım açısı -73° bulunmuştur. Buna göre diğer çalışmalara benzer olarak Kastelli Fayı'nın Avli segmentinde Heraklion-Messara Havzasının yönelimine benzer olarak GGB-KD-GB-KD gidişli, neredeyse doğrultu atımlı normal fay olduğu sonucuna varılır. Bulunan sismisite dağılımı ile fayın yönelimi benzerlik göstermektedir. Böylelikle daha hassas bir deprem kataloğu oluşturulmuş ve ada içindeki ilk gün ve sonraki gün olan bazı depremlerin odak mekanizma çözümleri yapılmıştır.
  • Öge
    Geochemical characterization of the metabasic rocks in the lower karakaya complex (Western pontides)
    (Graduate School, 2024-07-05) Uçar, Tuğçe ; Topuz, Gültekin ; 602211005 ; Geodynamics
    The Karakaya Complex covers extensive areas in the Sakarya Zone and is subdivided into two units such as the Lower Karakaya and Upper Karakaya complexes. The Upper Karakaya Complex is a strongly deformed, unmetamorphosed chaotic unit made up mainly of basic volcanic and volcanoclastic rocks, arkosic sandstone and limestone. The Lower Karakaya Complex comprises greenschist- to albite-epidote-amphibolite–facies metabasite, phyllite, marble, and minor serpentinite and metachert with locally preserved slices of blueschist and eclogite. There are mainly two opposite views on the formation setting of the Karakaya Complex such as (i) a back-arc rift basin that formed due to the southward subduction of the Paleotethys beneath the northern margin of Gondwana during the Late Triassic, or (ii) a subduction-accretion complex that formed to the southern margin of Eurasia by northward subduction of the Paleotethys during Late Triassic. The purpose of this study is twofold. The first purpose is to map the part of the Lower Karakaya Complex cropping out between Bilecik and Bozüyük towns (the Bozüyük Metamorphic Rocks) at the scale of 1/25.000 and to determine the rock assemblage and their mineral parageneses. The second purpose is to constrain the geochemical characteristics of the metabasic rocks in the Lower Karakaya Complex cropping out in areas such as Bandırma, Bursa, and Bilecik to understand their geodynamic formation setting. The Bozüyük Metamorphic Rocks comprise blueschist- and greenschist-facies rock assemblages involving metabasite, phyllite, marble and, minor serpentinite. The greenschist-facies metamorphism is retrograde with respect to epidote blueschist-facies, suggesting formation in a subduction zone. The age of the metamorphism is constrained as ≥ 200 Ma (Late Triassic) by 40Ar-39Ar stepwise dating of phengite. This age value in conjunction with Ar-Ar phengite data in the literature (201-215 Ma) suggests that a significant part of the Lower Karakaya Complex in the western Pontides, 30 km by 230 km, extending from Bandırma to the north of Eskişehir formed during the latest Triassic. About 80 vol.% of the metabasic rock in the Lower Karakaya Complex cropping out between the Bandırma to the north of Eskişehir show anorogenic alkaline to tholeiitic affinity similar to ocean island basalts (OIBs). About 10 vol.% of the metabasic rocks within the serpentinite slivers, interpreted as ophiolite fragments, are characterized by enriched mid-ocean ridge basalt (E-MORB) signature. Nearly 5 vol.% of the metabasite samples show normal mid-ocean ridge basalt (N-MORB) affinity, and the remaining metabasites are island-arc tholeiite (IAT). All these geochemical features conclusively demonstrate that the overwhelming part of accreted material originated in seamounts and the remaining part from related oceanic lithosphere (enriched and normal MORBs) and supra-subduction zone oceanic setting.
  • Öge
    Dating and interpreting a firn core from the East Antarctic Plateau
    (Graduate School, 2024-08-29) Sağol, Furkan Kaan ; Schwamborn, Georg Johannes ; Hörhold, Maria ; 602201003 ; Geodynamics
    Detecting and understanding potential changes in annual mean temperature and accumulation rate at the East Antarctic Plateau is crucial to assess the sensitivity and future response of the Antarctic ice sheet to global warming. Due to the very low accumulation rate and its spatial variability, the interpretation of climate proxies from shallow firn cores with centennial to decadal time resolution is challenging. A major limitation is the available time resolution obtained by available dating approaches and a reliable assessment of its uncertainty. In this study, a 204 m long firn core, B56, drilled in 2017 on the East Antarctic Plateau, is analyzed. The major goal of this study is dating the firn core by combining different dating methods based on available density data, dielectric properties, and ion chromatography (of non-sea-salt sulfate) data. To utilize density, the Herron-Langway model is used for determining the depth-age relation. In this model, temperature and snow accumulation are assumed to be constant and the relationship between the snow density and the depth below the snow surface does not change over time. Depending on the accumulation rate used, the resulting age at 200 m depth varies between 6000 to 7200 years. Secondly, the dielectric profile and non-sea-salt sulfate concentration (nssSO42-) data are used for constructing another depth-age model, thereby matching prominent data peaks to known volcanic eruptions that have been recorded in the past. Here, the resulting age at 200 m depth is determined to be about 6200 years, which compares well to published age models of firn cores from the East Antarctic Plateau. In comparison, it is recognized that all age models are consistent within the upper 40 m (stretching over the past 1000 years), but the Herron-Langway model tends to overestimate the age at greater depths. It is proposed that the findings indicate changes of the accumulation rate in the past, leading to the offset in the Herron-Langway model (which uses a constant accumulation rate). However, by combining the dating methods, it is possible not only to provide a reasonable dating over the full firn core, but also to improve the time resolution of the derived age model. This will improve the interpretation of the climate proxies extracted from this firn core and may serve as a role model for other shallow firn cores from the East Antarctic Plateau.
  • Öge
    High resolution coseismic surface displacement measurements between Çiğli and Hassa along the surface rupture of february 6, 2023 Pazarcık Earthquake
    (ITU Graduate School, 2025-06-18) Baka, Çağdaş Mert ; Yıldırım, Cengiz ; 501211040 ; Geodynamics
    The subject of this study is the first of the 6 February 2023 Kahramanmaraş Earthquake Doublet (Mw:7.7 and Mw: 7.6), Pazarcık Earhquake, that deeply affected Türkiye. After earthquake occured, studies related to satellite based geodetic data and remote sensing data conducted to reveal surface ruptures and slip distribution of these earthquake doublet. Although such studies contribute to bulk deformation analysis, comprehensive field investigations that determine and quantify the coseismic deformation, fault geometry relationships and discrete deformation analysis from offset features are still lacking. Istanbul Technical University, EarthBeeLab carried out a field campaign to produce high-resolution (<5 cm) UAS imagery with 300m width throughout the 510 km long surface rupture. The principal goal of this study is to provide a detailed pattern of the fault strands along the rupture, co-seismic slip distribution and deformation zone width variations along the surface rupture. Approximately 80 km length of the surface rupture from Hassa to Çiğli were mapped by using the mentioned UAS imagery dataset. The rupture then divided into five sections according to changes in geometry along the rupture: İslahiye, Beyoğlu, Türkoğlu, Küpelikız and Kapıçam from south to north. Deformation zone widths of the rupture were also measured and the results ranges from a few meters up to 1051m. According to measurements, narrow and concentrated sections are Kapıçam, Beyoğlu and Türkoğlu Sections while more distributed sections are observed as İslahiye and Küpelikız Sections. The jog areas where section geometries change represent the widest deformation zones along the fault. Displacements were categorized as ''On Fault'' for those occurring along the main fault and ''Off Fault'' for more than 10 meters from the main fault to show how much of strain is distributed within the deformation zone. After a detailed study over 1419 coseismic displacement measurements (1233 On Fault and 186 Off Fault), highest slip was identified as of 7.9 ± 0.3 m in Kapıçam Section and overall average value of the offset measurements was 2.18 ± 0.30 m. Based on the results of previous studies, maximum coseismic displacement value was obtained as 7.3 ± 0.2 m at Büyüknacar Area (25 km north of the Çiğli), which is smaller than our result. In the study area, Kapıçam Section and Beyoğlu-Türkoğlu transition exhibited the highest concentration and magnitude of displacements among the fault segments.