Kuzey Anadolu Fayı’nın Ilgaz (çankırı) – Karlıova (bingöl) Arasında Kalan Kesiminin Morfokronoloji Tabanlı Son Beşbin Yıllık Kayma Hızı Tarihçesi Ve Depremselliği

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Avrasya Yer Bilimleri Enstitüsü, 2012Thesis (PhD) -- İstanbul Technical University, Eurasia Institute of Earth Sciences, 2012Bu çalışmada, Türkiye'nin en önemli fay kuşaklarından birini oluşturan Kuzey Anadolu Fayı'nın (KAF), Ilgaz (Çankırı) ve Karlıova (Bingöl) arasında kalan kesiminin morfokronoloji tabanlı kayma hızı ve depremselliği çalışılmıştır. Fayın farklı kesimleri üzerinde uzaktan algılama ve arazi çalışmaları ile belirlenen toplam 7 çalışma alanında, OSL (Optik Uyarımlı Işınım) yöntemi ile yaşlandırılan ötelenmiş morfolojik birimlerin son beşbin yıllık zaman dilimi içerisinde işaret ettikleri ortalama jeolojik kayma hızı 18.4 +1.4/-1.3 mm/yıl'dır (%68 olasılık aralığı). Gerek bu ortalama değer, gerekse her bir çalışma alanından elde edilen bulgular, GPS ölçümlerinin modellenmesi ile hesaplanan elastik blok model hızlarının altında kalır. Farklı zaman aralıklarını temsil eden bu iki değer arasında görülen uyumsuzluğu açıklayan en önemli hipotez, KAF üzerinde yirminci yüzyılda meydana gelen ve toplam 1000 km civarında kesimin kırılması ile sonuçlanan deprem serisinin yol açtığı post sismik süreç ve buna bağlı olarak deformasyon hızının zaman içerisinde değişmesidir. 1939 Erzincan Depremi yüzey kırığının yaklaşık 100 km'lik bir kesimini oluşturan Kelkit Vadisi Segmenti üzerinde yapılan paleosismoloji amaçlı fay kazıları, bu tez çalışmasının ikinci kısımını oluşturur. Reşadiye (Tokat) ve Koyulhisar (Sivas) arasında açılan toplam dört hendekten, iki tanesinden elde edilen sonuçlara göre KAF'ın bu kesimi için 1939 öncesi 3 eski olay belirlenmiştir. Bunlar gençten yaşlıya doğru sırasıyla MS. 1668, 1254 ve 1045 tarihsel depremleri ile deneştirilmiştir. Ayrıca bu ve bölgede yapılan diğer paleosismoloji çalışmalarının sonuçları birlikte değerlendirilerek, doğrultu atımlı fayların özellikle yapısal olarak karmaşık kesimleri için ?yarı-değişken? deprem tekrarlanma modeli önerilmiştir.In this study, I documented new geologic slip-rates for the structurally simple and single strand section of the North Anatolian Fault (NAF), between Ilgaz (Çankırı) in the west and Karlıova (Bingöl) in the east, to provide a better understanding on this system?s behaviour in different temporal and spatial scales. This morphochronologic study mainly depends on identification of sites with proper offset features, precise displacement measurements of these structures and lastly Optical Stimulated Luminescence (OSL) dating of each related geologic unit. I calculated 7 independent slip-rates from dating of geomorphic markers in 5 new and 2 revised previously known sites. I analysed all these new and existing data by using a ready Monte Carlo model to determine (a) a precise average slip rate and (b) any slip variability for the last 5 ka. Results from modelling yield an average slip rate of 18.4 +1.4/-1.3 mm/a (68% confidence). The most plausible mechanism to clarify the discrepancy of geologic and geodetic rates is the postseismic process, which started after the 20th century earthquake sequence on the NAF. In addition to slip-rate studies, I undertook paleoseismological trench investigations on the Kelkit Valley segment where there is little or no paleoseismic information to understand the rupture behaviour at this structural complex section of the NAF. I excavated 4 trenches at three different sites, between Reşadiye (Tokat) and Koyulhisar (Sivas). Only two trenches provided reliable results as evidences of 4 paleoearthquakes, which are correlated with A.D. 1045, A.D. 1254, and A.D. 1668 historical events prior to the 1939 Erzincan Earthquake rupture by using historical records and other nearby paleoseismological studies. I also suggest a new slip model by using both this and previous studies, and named it as ?quasi-variable?, in which amount of slip differs between individual events, but contains a kind of an order in multi-cycle periods.DoktoraPh

Spatio-temporal behaviour of continental transform faults: implications from the late Quaternary slip history of the North Anatolian Fault, Turkey

The slip history of the North Anatolian Fault (NAF) is constrained by displacement and age data for the last 550 ka. First, I classified all available geological estimates, being member of three groups: Model I for the eastern, Model II for the central and Model III for the western segments where the North Anatolian Shear Zone gradually widens from east to west. The short-term uniform slip solutions yield similar results, 17.5 +4/-3.5 mm/a, 18.9 +3.7/-3.3 mm/a and 16.9 +1.2/-1.1 mm/a from east to the west. Although these model rates do not show any significant spatial variations among themselves, the correlation with geodetic estimates, ranging between 15 mm/a and 28 mm/a for different sections of the NAF, displays significant discrepancies especially for the central and western segments of the fault. Discrepancies suggest that the majority of strain is accumulated along the NAF, but some portion of it is distributed along secondary structures of the North Anatolian Shear Zone. The deformation rate is constant at least for the last 195 ka, whereas the limited number of data show strain transfer from northern to the southern strand between 195 and 320 ka BP in the Marmara Region when the incremental slip rate decreases to 13.2 +3.1/-2.9 mm/a for the northern strand of the NAF. Considering the possible uncertainties of incremental displacements and their timings, it is clear that more studies on slip rate are needed at different sites, including major structural elements of the North Anatolian Shear Zone. Although most of the strain is localized along the main displacement zone, the NAF, secondary structures are still capable of generating earthquakes that can hardly reach Mw 7.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The 20th anniversary of the Eastern Marmara Earthquakes: active tectonics of continental strike-slip faults

International audienc

Preliminary results about the Quaternary activity of the Ovacık Fault Eastern Turkey

The Erzincan Basin and the surrounding region have a complex structure, which is formed by the interaction of the North Anatolian Fault (NAF), the Northeast Anatolian Fault (NEAF), the Pülümür Fault (PF), and the Ovacık Fault (OF). The region has been shaked many times by devastating earthquakes throughout both the instrumental and the historical periods. The infamous 26 December 1939 Erzincan Earthquake (M~7.9) is the largest event, which was instrumentally recorded along the NAF. Moreover, the eastern continuation of the surface rupture of this earthquake, "the Yedisu Segment", is known as one of the two seismic gaps on this dextral shear zone. We started multi-disciplinary studies on the OF, which has relatively very limited data. Even though some researches think about this tectonic feature as a non-active fault, recent GPS measurements point strain accumulation along it. In addition to that 1992 Erzincan and 2003 Pülümür earthquakes loaded additional stress on the neighboring faults, including the OF. The OF elongate between the SE Erzincan Basin and Kemaliye (Erzincan) about 110 km with a general strike of N60E. The clear morphological expression of the fault is especially observed around Ovacık, Tunceli. The OF delimits the Jurassic aged Munzur limestone in the north and the Miocene volcanoclastics and Permo-Carboniferous schist in the south in this vicinity. We identified many offset features, such as wash plains, moraines, alluvial fans and inset terraces in our preliminary morphological maps. The measured displacements change from 20 to 350 m, which may play a critical role in the calculation of the geological slip-rate. Moreover, we used morphological indices, such as topographic profiling, hypsometric integral, basin asymmetry, and the mountain front sinuosity to quantify the activity of the OF. Our preliminary results clearly point out the necessity of future studies, which may help to understand the earthquake potential of this poorly known tectonic feature

The role of intraplate strike-slip faults in shaping the surrounding morphology: The Ovacık Fault (eastern Turkey) as a case study

Although the westward extrusion of the Anatolian Block is mainly compensated along its boundary faults, the North Anatolian and the East Anatolian shear zones, it is internally deformed in a dominant manner by some strike-slip faults as well. To obtain a better understanding about this intraplate deformation of the Anatolian Block, we investigate the tectonic geomorphology of the Ovacık Fault (OF), which is the northeastern member of the Malatya-Ovacık Fault Zone (MOFZ). Further, we apply the most common geomorphic indices, such as the hypsometric curve and integral, longitudinal channel profiles, channel steepness and concavity, mountain front sinuosity, and valley height-width ratio to characterise and quantify the deformation along the OF and the surrounding region where the regional morphology is shaped with the joint effect of palaeo- and neotectonics and other morphological factors such as palaeoglacial processes. The highest hypsometric integral, steepness and concavity values are generally observed along the northeastern strand of the OF (the Munzur Mountains) and the Kemaliye Region. Further, we interpret that high HI and steepness values indicate a regional tectonic uplift because of either a change in fault geometry, which gives rise to the vertical component on the OF, or a regional high convergence zone. Furthermore, this study gives the first calculation of vertical uplift in the northern margin of the Ovacık Basin (OB) as at least 0.5 mm/y for long term deformation history. Thus, our results exhibit that the OF is one of the intraplate strike-slip faults of the Anatolian Block

Reconstructing orogens without biostratigraphy: The Saharides and continental growth during the final assembly of Gondwana-Land

A hitherto unknown Neoproterozoic orogenic system, the Saharides, is described in North Africa. It formed during the 900–500-Ma interval. The Saharides involved large subduction accretion complexes occupying almost the entire Arabian Shield and much of Egypt and parts of the small Precambrian inliers in the Sahara including the Ahaggar mountains. These complexes consist of, at least by half, juvenile material forming some 5 million km2 new continental crust. Contrary to conventional wisdom in the areas they occupy, evolution of the Saharides involved no continental collisions until the end of their development. They formed by subduction and strike-slip stacking of arc material mostly by precollisional coastwise transport of arc fragments rifted from the Congo/Tanzania cratonic nucleus in a manner very similar to the development of the Nipponides in east Asia, parts of the North American Cordillera and the Altaids. The Sahara appears to be underlain by a double orocline similar to the Hercynian double orocline in western Europe and northwestern Africa and not by an hypothetical “Saharan Metacraton.” The method we develop here may be useful to reconstruct the structure of some of the Precambrian orogenic belts before biostratigraphy became possible

Distributed transpressive continental deformation: The Varto Fault Zone, eastern Turkey

The convergence between the Eurasian and Arabian plates has created a complicated structural setting in the Eastern Turkish high plateau (ETHP), particularly around the Karlıova Triple Junction (KTJ) where the Eurasian, Arabian, and Anatolian plates intersect. This region of interest includes the junction of the North Anatolian Shear Zone (NASZ) and the East Anatolian Shear Zone (EASZ), which forms the northern border of the westwardly extruding Anatolian Scholle and the western boundary of the ETHP, respectively. In this study, we focused on a poorly studied component of the KTJ, the Varto Fault Zone (VFZ), and the adjacent secondary structures, which have complex structural settings. Through integrated analyses of remote sensing and field observations, we identified a widely distributed transpressional zone where the Varto segment of the VFZ forms the most northern boundary. The other segments, namely, the Leylekdağ and Çayçatı segments, are oblique-reverse faults that are significantly defined by uplifted topography along their strikes. The measured 515 and 265 m of cumulative uplifts for Mt. Leylek and Mt. Dodan, respectively, yield a minimum uplift rate of 0.35 mm/a for the last 2.2 Ma. The multi-oriented secondary structures were mostly correlated with “the distributed strike-slip” and “the distributed transpressional” in analogue experiments. The misfits in strike of some of secondary faults between our observations and the experimental results were justified by about 20° to 25° clockwise restoration of all relevant structures that were palaeomagnetically measured to have happened since ~2.8 Ma ago. Our detected fault patterns and their true nature are well aligned as being part of a transpressional tectonic setting that supports previously suggested stationary triple junction model

Palaeoearthquakes on the Kelkit Valley Segment of the North Anatolian Fault, Turkey: Implications for the Surface Rupture of the Historical 17 August 1668 Anatolian Earthquake

Te 26 December 1939 Erzincan (M s = 7.8) and 20 December 1942 Erbaa-Niksar (M s= 7.1) earthquakes created a total surface rupture more than 400 km between Erzincan and Erbaa on the middle to eastern sections of the North Anatolian Fault. Tese two faulting events are separated by a 10-km-wide releasing stepover, which acted like a seismic barrier in the 20th century. To understand the rupture behaviour in this structurally complex section of the North Anatolian Fault, we undertook palaeoseismological trench investigations on the Kelkit Valley segment where there is little or no palaeoseismic information. We found evidence for three surface faulting earthquakes predating the 1939 event during the past millennium in trenches excavated in Reşadiye and Umurca. In addition to the 1939 Erzincan earthquake, prior surface ruptures are attributed to the 17 August 1668, A.D. 1254 and A.D. 1045 events. Surface rupture of the 17 August 1668 Anatolian earthquake was previously reported in palaeoseismological studies, performed on the 1944, 1943, and 1942 earthquake fault segments. We suggest that the surface rupture of this catastrophic event jumped the 10-km-wide releasing stepover in Niksar and continued eastward to near Koyulhisar. Te existence of different amount of offsets in feld boundaries (sets of 4 m, 6.5 m, and 10.8 m) was interpreted as the result of multiple events, in which the 1939, 1668, and 1254 surface ruptures have about 4, 2.5, and 4 metres of horizontal coseismic slip on the Kelkit Valley segment of the North Anatolian Fault, respectivel