33 results on '"Tolga Gorum"'
Search Results
2. Spatiotemporal variations of fatal landslides in Turkey
- Author
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Tolga Gorum and Seckin Fidan
- Subjects
021110 strategic, defence & security studies ,business.industry ,0211 other engineering and technologies ,Distribution (economics) ,Landslide ,02 engineering and technology ,Geotechnical Engineering and Engineering Geology ,Natural (archaeology) ,Geography ,Megacity ,Hotspot (Wi-Fi) ,Natural hazard ,Black sea ,Physical geography ,business ,021101 geological & geomatics engineering - Abstract
Landslides are one of the devastating geohazards that cause extensive socio-economic and environmental damages on local, regional, and global scales. Previous studies based on digital media sources have attracted attention to the high fatal landslide rate in Turkey, at a continental or global scale; however, the preparation of a comprehensive and long-term database for Turkey has been neglected until today. To examine this data gap, we present a new database of fatal landslide events resulting in fatalities from 1929 to 2019, which has been compiled using Turkish national and local printed and digital media reports, academic papers, disaster, and city annual reports. The fatal database of Turkey (FATALDOT) shows that, in total, 1343 people were killed in 389 fatal landslide events. The spatiotemporal distribution of the fatal landslides highlighted increasing trends with reference to two distinct hotspot zones throughout the Eastern Black Sea and Marmara Region, mostly around Istanbul megacity. Our results show that there has been a significant uniformity between the number of fatalities and fatal landslides triggered by anthropogenic and natural factors over the past decade, indicating an increasing dominance of human activities in fatality rates. Our findings also, for the first time, remarked the potential signatures of the economic crisis and political steadiness on fatal landslide trends. Nevertheless, we conclude that the increasing rate of anthropogenic disturbances in urban and mountainous areas, together with regional variances in topography and climatic setting, is essential in governing the pattern of fatal landslides.
- Published
- 2021
3. Türkiye’de ölümcül heyelanların dağılım karakteristikleri ve ulusal ölçekte öncelikli alanların belirlenmesi
- Author
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Seckin Fidan and Tolga Gorum
- Subjects
education.field_of_study ,Geography ,Distribution pattern ,Human settlement ,Black sea region ,Population ,Period (geology) ,Landslide ,General Medicine ,Physical geography ,Priority areas ,education ,Distribution characteristic - Abstract
Annually, a large number of landslide events that resulted in the deaths of dozens of people occur in Turkey. However, the preparation of an inventory of fatal landslide events in Turkey has been neglected until today. In this respect, a database on fatal landslide events in Turkey for the period from 1929 to 2019 was compiled from various sources comprising national and local printed and digital media reports with pre-determined keywords in Turkish, academic papers, disaster, and city annual reports, and government and aid agency reports. In the studied period, 389 landslides events that caused of death 1343 people were detected. According to the Mann-Kendall (MK) test and Sen's slope method, which is used to determine the temporal distribution characteristic of landslide events and deaths, an increasing trend is observed in both events and the number of deaths in the period comprising 1929-2019. These landslide events, which show intensity in the summer during the year, constitute two major density regions, the Eastern Black Sea Region and the Istanbul environment. In general, the Eastern Black Sea Region is represented by fatal landslides triggered by natural factors, while fatal landslides triggered by anthropogenic factors characterize the Istanbul and near vicinity. Spatially, fatal landslides were recorded in 227 different counties in 67 of 81 cities. The determination of the priority areas was evaluated by the population of the settlements exposed to the landslide and the probability value calculated with the number of landslides recorded and the relationship with the number of the dead. In conclusion, based on the final distribution pattern we revealed that the frequency of the landslides in provinces and districts where the topographic roughness is above the country average, at the Eastern Black Sea Region are strikingly high from the other hilly sections of the country.
- Published
- 2020
4. The Quaternary landforms of the Büyük Menderes Graben System: the southern Menderes Massif, western Anatolia, Turkey
- Author
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Emrah Özpolat, Tolga Gorum, and Cengiz Yıldırım
- Subjects
lcsh:Maps ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Landform ,red relief image map ,Geography, Planning and Development ,menderes massif ,Geochemistry ,Alluvial fan ,extensional landscape ,river terrace ,Massif ,010502 geochemistry & geophysics ,01 natural sciences ,Extensional definition ,alluvial fan ,western anatolia ,Graben ,lcsh:G3180-9980 ,Earth and Planetary Sciences (miscellaneous) ,Quaternary ,Geology ,0105 earth and related environmental sciences - Abstract
We present the first detailed Quaternary landform map of the Büyük Menderes Graben System, located in western Turkey which is one of the most active extensional domains in the world. The main map was produced with a combination of TanDEM-X (12.5 m resolution), Red Relief Image Map, unmanned aerial vehicle, Google Earth images, and multiple fieldworks. The main map is presented at a scale of 1:160,000 although landforms were mapped at a scale of 1:15,000. The ten Quaternary landforms were defined considering their surface morphology and depositional environment. The alluvial fans, river terraces, and floodplains are the most common landforms. The spatial pattern of the alluvial fans and river terraces showed the variable rates of tectonics and surface processes along the strike of the graben system. The distribution of the meander cut-offs and paleo-shorelines imply that Büyük Menderes Graben System is vulnerable to geohazards like flash-flood sedimentation and flood events.
- Published
- 2020
5. River, alluvial fan and landslide interactions in a tributary junction setting: Implications for tectonic controls on Quaternary fluvial landscape development (Central Anatolian Plateau northern margin, Turkey)
- Author
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Tuǧba Öztürk, Kevin P. McClain, Tolga Gorum, Attila Çiner, Cengiz Yıldırım, Orkan Özcan, Sefa Şahin, M. Akif Sarıkaya, Oğuzhan Köse, Nafiye Güneç Kıyak, Işık Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Işık University, Faculty of Arts and Sciences, Department of Physics, and Öztürk, Tuğba
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Radiocarbon dating ,Alluvial fan ,010504 meteorology & atmospheric sciences ,Turkey ,Fluvial terrace ,Luminescence dating ,Fluvial ,010502 geochemistry & geophysics ,01 natural sciences ,law.invention ,Yenice river ,law ,Tributary ,Fluvial geomorphology ,Anatolia ,OSL ,Pontides ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Filyos river ,geography ,Meleagris gallopavo ,geography.geographical_feature_category ,Plateau ,Cosmogenic surface exposure dating ,Landslide ,River terrace ,Archaeology ,Central pontides ,Tectonic setting ,Quaternary ,Geology - Abstract
Along the western flank of the northern margin (Central Pontides) of the Central Anatolian Plateau, the humidity from the Black Sea is much higher than the central and eastern flanks and creates a complex relationship between surface and tectonic processes by triggering intense mass wasting activity and aggradation within narrow valleys. We identified three incised fill terrace levels and used Optically Stimulated Luminescence (OSL) dating to calculate fluvial sediment ages and cosmogenic 36Cl exposure dating to calculate limestone boulders exposure ages across the terrace surface. Stratigraphical interpretations and OSL ages of the lowest levels revealed that a fluvial fill terrace formed in the main valley at 275.6 ± 12.8 ka and was overlain by a main river-tributary junction alluvial fan that was abandoned at 39.5 ± 3.5 ka. The results collectively show the influence of climate, topography, hillslope processes, and lithology on aggradation-incision patterns of main rivers. Prolonged aggradation can prevent the channel equilibrium required to calculate rock uplift rates while also causing a new base-level and aggradation upstream. This effect can be exacerbated in uplifting mountainous regions with limited depositional areas. Bedrock incision rates based on the fluvial terrace age were between 0.15 and 0.2 mm/a since 39.5 ± 3.5 ka. However, the high aggradation within this segment of the main valley prevented incision of the channel bedrock for long periods, causing a potential underestimation of the rock uplift rate calculation. Our local period of aggradation appears to be related to increased aggradation and decreased bedrock incision rates measured 14 km upstream that were previously assumed to be the result of decreased tectonic uplift rates. This demonstrates the importance of corroborating strath terrace incision rate estimations with ages and incision rates of downstream fill terraces, if present, to check for potential interference with the tectonic signal. This work was supported by the European Commission within the Marie Curie-ITN ALErT Project [grant number FP7-PEOPLE-2013-ITN , number 607996] and the Istanbul Technical University BAP Project [grant number TDK-2017-40776 ]. We would also like to thank the CNRS-ASTER Laboratory in Aix en Provence France for AMS measurements and AcmeLabs, Canada for measurements of major and trace element concentrations. Reviews by the Geomorphology editor, Sarah Boulton (University of Plymouth), Tim Barrows (University of Wollongong), and an anonymous reviewer have greatly helped to improve the content of this work. This work was supported by the European Commission within the Marie Curie-ITN ALErT Project [grant number FP7-PEOPLE-2013-ITN, number 607996] and the Istanbul Technical University BAP Project [grant number TDK-2017-40776]. We would also like to thank the CNRS-ASTER Laboratory in Aix en Provence France for AMS measurements and AcmeLabs, Canada for measurements of major and trace element concentrations. Reviews by the Geomorphology editor, Sarah Boulton (University of Plymouth), Tim Barrows (University of Wollongong), and an anonymous reviewer have greatly helped to improve the content of this work. Publisher's Version
- Published
- 2021
6. Sinkhole development in the Sivas gypsum karst, Turkey
- Author
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Mateja Ferk, Tolga Gorum, Francisco Gutiérrez, and Ergin Gökkaya
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geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Water table ,Bedrock ,Sinkhole ,Geochemistry ,Subsidence ,010502 geochemistry & geophysics ,Karst ,01 natural sciences ,Cave ,Denudation ,Carbonate rock ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
The extensive gypsum karst of Sivas, Turkey is one of the most outstanding examples of bare gypsum karst in the world. It displays a number of remarkable geomorphic features, including: (1) two stepped planation surfaces cut-across folded gypsum developed during an initial phase of slow base level deepening punctuated by periods of stability; (2) unusual deeply entrenched gypsum canyons related to a subsequent phase of rapid fluvial incision and water table lowering; (3) a polygonal karst of superlative quality mainly developed in the upper surface; (4) relict valleys disrupted by sinkholes in the lower erosional surface; (5) a large number of bedrock collapse sinkholes mostly associated with the lower surface; and (6) numerous cover subsidence sinkholes developed in the valley floors. This work analyses the spatial distribution, characteristics and evolution of the sinkholes within the broad Plio-Quaternary geomorphological and paleohydrological evolution of the epigene karst system dominated by autogenic recharge. A cartographic sinkhole inventory has been produced in an area covering 2820 km(2) with morphometric data and including 295 bedrock collapse sinkholes and 302 cover subsidence sinkholes. The different sinkhole types show a general spatial zonation controlled by the hydrogeological functioning of the different sectors: (1) solution sinkholes (polygonal karst) in the upper recharge area; (2) bedrock collapse sinkholes in the lower denudation surface and close to the base level, where well developed caves are inferred; and (3) cover subsidence sinkholes, with high densities probably associated with areas of preferred groundwater discharge. The morphology of the bedrock collapse sinkholes, varying from small cylindrical holes to large and deep tronco-conical depressions with gentle slopes reflect to geomorphic evolution of these sinkholes that reach exceptionally large hectometre-scale diameters. Their evolution, involving substantial enlargement and deepening, is attributed to the solutional removal as solute load of large volumes of gypsum by downward vadose flow. This type of morphological evolution with significant post-collapse solutional denudation differs from that observed in carbonate rocks characterised by lower solubility and erodibility. The analysis of historical imagery reveals that bedrock collapse sinkholes currently have a very low probability of occurrence and that buried cover subsidence sinkholes are used for urban development creating risk situations. (C) 2021 The Author(s). Published by Elsevier B.V.
- Published
- 2021
7. Could road constructions be more disastrous than an earthquake in terms of landsliding?
- Author
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Dalia Kirschbaum, Luigi Lombardo, Hakan Tanyas, Tolga Gorum, UT-I-ITC-4DEarth, Faculty of Geo-Information Science and Earth Observation, and Department of Earth Systems Analysis
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010504 meteorology & atmospheric sciences ,Notice ,business.industry ,Environmental resource management ,0207 environmental engineering ,Magnitude (mathematics) ,Landslide ,02 engineering and technology ,Mass wasting ,01 natural sciences ,Geography ,Anthropocene ,Hydroelectricity ,Slope stability ,ITC-ISI-JOURNAL-ARTICLE ,020701 environmental engineering ,business ,ITC-GOLD ,Sediment transport ,0105 earth and related environmental sciences - Abstract
Roads can have a significant impact on the frequency of mass wasting events in mountainous areas. However, characterizing the extent and pervasiveness of landslides over time rarely been documented due to limitations in available data sources to consistently map such events. We monitored the evolution of a road network and assessed its effect on slope stability for a ten year window in Arhavi, Turkey. The main road construction projects run in the area are associated with a hydroelectric power plant as well as other road extension works and are clearly associated with the vast majority (90.1%) of mass movements in the area. We also notice that the overall number and size of the landslides are much larger than in the naturally-occurring comparison area. This marks a strong and negative effect of human activities on the natural course of earth surface processes. Our findings show that the damage generated by the road construction is compatible with the possible effect of a theoretical earthquake with a magnitude greater than Mw=6.0. Overall, better co- and post-construction conditions should be ensured during and after road works to mitigate the risk to local communities. We also notice a significant variation in sediment transport as a result of road construction. As a result, our study fits in the big picture of Anthropocene related changes and specifically points out at problems in mountainous areas that could undoubtedly be better managed to reduce the risk to local communities.
- Published
- 2020
8. Fatal Landslide Database of Turkey (FATALDOT)
- Author
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Tolga Gorum and Seckin Fidan
- Subjects
Geography ,Landslide ,Cartography - Abstract
Landslides are one of the destructive geomorphological hazards that cause substantial socio-economic and environmental damages on a global scale. Knowing the precise number of deaths caused by landslides and their spatial and temporal distributions will facilitate a better understanding of the losses and damages, and further to prevent and minimize the damages caused by this type of disasters. Thus, reliable historical inventories, including past landslide events, are crucial in understanding the future landslide hazards and risks.Turkey, similar to mountainous countries suffering from landslides, is also high-elevated (average altitude of >1100 m) and tectonically active country located where the Europe and Asia continents meet. In the years between 1995-2014, 335 of the total 1375 fatalities caused by landslides in European countries have occurred in Turkey. This reported number not only shows that Turkey is the first country in Europe in terms of deaths caused by landslides but also implies that the landslide related problems are overwhelming than expected in Turkey. Although many studies have been carried out on individual landslides and landslide inventories in Turkey, we have limited information about the landslides that cause death. However, there are many landslide events that resulted in the deaths of tens of people every year in Turkey. Therefore, neglecting fatal landslides and their consequences resulted in an unrealistic comprehension of landslide risk. In this respect, we contribute to filling this data gap by presenting the first country-scale archive inventory of fatal landslides, their spatio-temporal distribution, and the triggering mechanism characteristics for Turkey, which is Europe's topmost deadly country.The fatal landslide events in Turkey for the period from 1929 to 2019 were compiled from various sources comprising national and local printed and digital media reports with pre-determined keywords in Turkish, academic papers, disaster, and city annual reports, and government and aid agency reports. According to the new database, 1343 people lost their lives as a result of 389 landslide events in Turkey between 1929 and 2018. In total 197 fatal landslide events, which resulted in 301 deaths, were identified due to anthropogenic triggers (i.e., construction, infrastructure, and mining activities). On the other hand, 147 landslides occurred, and 883 people lost their lives due to natural triggering factors. The natural trigger origin of the fatal landslides is concentrated in the Eastern Black Sea and is generally shallow landslides corresponding to regolithic zones where chemical weathering is severe. On the contrary, the trigger factor of 45 landslide events cannot be assigned to the FATALDOT database due to a lack of detailed information in incidence reports. The database, which is planned to be transformed into an information system with a semi-automatic update feature, is thought to be an underlying data source for future research works to prevent hazard and risk studies and landslide-related deaths in the country scale.
- Published
- 2020
9. Tectonic, topographic and rock-type influences on large landslides at the northern margin of the Anatolian Plateau
- Author
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Tolga Gorum
- Subjects
021110 strategic, defence & security studies ,geography ,Plateau ,geography.geographical_feature_category ,0211 other engineering and technologies ,Fluvial ,Terrain ,Landslide ,02 engineering and technology ,Geotechnical Engineering and Engineering Geology ,Tectonics ,Erosion ,Radiometric dating ,Geomorphology ,Geology ,021101 geological & geomatics engineering ,Orographic lift - Abstract
High Anatolian orographic margins have large variations in terms of topographic relief, precipitation, and uplift rate. These variations lead to the dynamics of mass movements and surface runoff, which are the dominant geomorphological processes in ice-free mountain landscapes. There is growing recognition that large landslides are important agents of landscape evolution, resulting in massive slope failures, which can cause extensive and rapid topographic changes in many active orogenic belts. Unlike the cognatic orogenic plateau margins in the world, there are no studies available on the large landslides and their geomorphic impact at the margins of the Anatolian Plateau. This study presents results from a regional-scale inventory of 1290 large landslides (> 1 km2) that allow the characterization of spatial distribution and landslide-dominated landscapes in the northern margins of the Anatolian Plateau. The majority of large landslides are clustered in three main zones that correspond to the Western, Central, and Eastern Pontides, which is an east-west-trending orogenic belt that represents a coalesced tectonic entity in the northern section of Turkey. Nearly 80% of large landslides have occurred in a terrain with a mean hillslope relief of > 1000 m in those three landslide-dominated landscapes. The results of regional comparisons reveal that in addition to hillslope relief and steepness, lithotectonic differences largely control the abundance of landslides along the northern margins of the Anatolian Plateau. In this respect, the spatial distribution and abundance of large landslides imply a landscape in which lithological and tectonic controls on hillslope erosion are more significant than climate. The study further shows that the parallel or perpendicular position of the landslides with respect to the direction of the drainage network is effective as positive or negative feedback in response to fluvial dissection of the plateau margins. On the other hand, there is certainly a need for more comprehensive radiometric dating studies to understand the contribution of large landslides on the erosional decay rate of Anatolian Plateau margins. Furthermore, the presence of these large landslides and the derived deposits in this dynamic terrain provide a unique opportunity for deciphering the past climatic and seismic events.
- Published
- 2018
10. Vegetation record of the last three millennia in central Anatolia: Archaeological and palaeoclimatic insights from Mogan Lake (Ankara, Turkey)
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Tolga Gorum, Aydin Akbulut, Cemal Tunoğlu, Emel Oybak Dönmez, Muammer Tün, Alaettin Tuncer, Faruk Ocakoğlu, and Burçin Aşkım Gümüş
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Palynology ,010506 paleontology ,Archeology ,Global and Planetary Change ,010504 meteorology & atmospheric sciences ,Macrofossil ,Geology ,Vegetation ,Structural basin ,01 natural sciences ,Archaeology ,Natural (archaeology) ,Geography ,Aridification ,Period (geology) ,Roman Warm Period ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
In this study, the high-resolution palynological data derived from two cores taken from Mogan Lake in the Golbasi Basin of the Ankara region in central Anatolia (Turkey) are presented. The results provide the palaeobotanical, palaeoclimatological and palaeoenvironmental records of the last ca. 3100 years for the region which is characterised by rich natural resources and a long human occupation history. The major climatic events and the archaeological-historical periods, which are well established in previous works, along with textual sources, are related to vegetation history inferred from the palynological investigation in the study area. Five main vegetation phases are distinguished and interpreted. Our findings demonstrate that the phases of limited woody vegetation cover are chiefly coupled to several dry climate periods, with some exceptions. Steppe vegetation in an open landscape accompanied by more cultural indicators and lesser arboreal elements is inferred during the Near-East Aridification Phase at the LBA-Iron Age transition (c. 1200-850 BCE), Roman Warm Period before 700 CE, Medieval Warm Period at about 1020 CE, the 1500s and twentieth century. Only during the three dry episodes in the 1600s, 1800s and at the start of Modern Warming Period (in the twentieth century) partial arboreal recovery is deduced, and land-cover patterns are related to both natural and human-induced factors. The most extensive pine-dominated forest cover coincides mainly with the three wet climatic episodes, in Galatians times of the Hellenistic Period at c. 2080 BP, the 700s CE of the middle Byzantine era, the Seljuqs Dynasty and the earlier Ottoman Periods (c. 1165-1432/1435 CE). The former episode is represented by remarkable signs of human interference, while the others have marks of sporadically less cultivated landscape. It is concluded that a combination of various factors can be taken into account as the drivers of vegetation changes in the Ankara region, but climate appears to have been the primary agent in shaping the land-cover. (C) 2021 Elsevier Ltd. All rights reserved.
- Published
- 2021
11. The Sinop Peninsula: The Northernmost Part of Asia Minor
- Author
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Cengiz Yıldırım, Okan Tüysüz, and Tolga Gorum
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Paleontology ,geography ,geography.geographical_feature_category ,Peninsula ,Landform ,Fluvial ,Submarine pipeline ,Black sea ,Marine terrace ,Geology - Abstract
The Sinop Peninsula is located at the northernmost part of the Asia Minor (Anatolia). Its geographic position between the Central Pontide Mountains and the Black Sea together with the presence of young geological units and landforms provides favorable conditions for understanding onshore and offshore geological and geomorphic processes acting along the northern Anatolian coasts. Here, we focus on some landscapes that constitute one of the best examples along the Turkish Black Sea coast. These are inundated fluvial valleys, uplifted isthmus and marine terraces, and paleo- and active dunes.
- Published
- 2019
12. A seismologically consistent expression for the total area and volume of earthquake-triggered landsliding
- Author
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Patrick Meunier, Odin Marc, Taro Uchida, Niels Hovius, and Tolga Gorum
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Peak ground acceleration ,geography ,geography.geographical_feature_category ,Seismic microzonation ,010504 meteorology & atmospheric sciences ,Landslide classification ,Landslide ,Fault (geology) ,010502 geochemistry & geophysics ,01 natural sciences ,Tectonics ,Geophysics ,Landslide mitigation ,Seismic moment ,Seismology ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
We present a new, seismologically consistent expression for the total area and volume of populations of earthquake-triggered landslides. This model builds on a set of scaling relationships between key parameters, such as landslide spatial density, seismic ground acceleration, fault length, earthquake source depth, and seismic moment. To assess the model we have assembled and normalized a catalog of landslide inventories for 40 shallow, continental earthquakes. Low landscape steepness causes systematic overprediction of the total area and volume of landslides. When this effect is accounted for, the model predicts the total landslide volume of 63% of 40 cases to within a factor 2 of the volume estimated from observations (R2=0.76). The prediction of total landslide area is also sensitive to the landscape steepness, but less so than the total volume, and it appears to be sensitive to controls on the landslide size-frequency distribution, and possibly the shaking duration. Some outliers are likely associated with exceptionally strong rock mass in the epicentral area, while others may be related to seismic source complexities ignored by the model. However, the close match between prediction and estimate for about two thirds of cases in our database suggests that rock mass strength is similar in many cases and that our simple seismic model is often adequate, despite the variety of lithologies and tectonic settings covered. This makes our expression suitable for integration into landscape evolution models and application to the anticipation or rapid assessment of secondary hazards associated with earthquakes.
- Published
- 2016
13. UAV-based evaluation of morphological changes induced by extreme rainfall events in meandering rivers
- Author
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Bülent Bayram, Orkan Özcan, Fusun Balik Sanli, Tolga Gorum, Semih Sami Akay, and Omer Lutfi Sen
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Geologic Sediments ,Atmospheric Science ,Topography ,Time Factors ,Turkey ,010504 meteorology & atmospheric sciences ,Rain ,Marine and Aquatic Sciences ,Sinuosity ,010502 geochemistry & geophysics ,01 natural sciences ,Deposition (geology) ,Flooding ,Surveys and Questionnaires ,Animal Management ,Sedimentary Geology ,Multidisciplinary ,Geography ,Geology ,Agriculture ,Satellite Communications ,Erosion ,Medicine ,Estuaries ,Environmental Monitoring ,Research Article ,Freshwater Environments ,Livestock ,Science ,Meteorology ,Rivers ,Surface Water ,Streamflow ,Petrology ,0105 earth and related environmental sciences ,Hydrology ,Landforms ,Flood myth ,Ecology and Environmental Sciences ,Aquatic Environments ,Shores ,Biology and Life Sciences ,Sediment ,Geomorphology ,Bodies of Water ,Water level ,Earth Sciences ,River morphology ,sense organs - Abstract
Morphological changes, caused by the erosion and deposition processes due to water discharge and sediment flux occur, in the banks along the river channels and in the estuaries. Flow rate is one of the most important factors that can change river morphology. The geometric shapes of the meanders and the river flow parameters are crucial components in the areas where erosion or deposition occurs in the meandering rivers. Extreme precipitation triggers erosion on the slopes, which causes significant morphological changes in large areas during and after the event. The flow and sediment amount observed in a river basin with extreme precipitation increases and exceeds the long-term average value. Hereby, erosion severity can be determined by performing spatial analyses on remotely sensed imagery acquired before and after an extreme precipitation event. Changes of erosion and deposition along the river channels and overspill channels can be examined by comparing multi-temporal Unmanned Aerial Vehicle (UAV) based Digital Surface Model (DSM) data. In this study, morphological changes in the Büyük Menderes River located in the western Turkey, were monitored with pre-flood (June 2018), during flood (January 2019), and post-flood (September 2019) UAV surveys, and the spatial and volumetric changes of eroded/deposited sediment were quantified. For this purpose, the DSAS (Digital Shoreline Analysis System) method and the DEM of Difference (DoD) method were used to determine the changes on the riverbank and to compare the periodic volumetric morphological changes. Hereby, Structure from Motion (SfM) photogrammetry technique was exploited to a low-cost UAV derived imagery to achieve riverbank, areal and volumetric changes following the extreme rainfall events extracted from the time series of Tropical Rainfall Measuring Mission (TRMM) satellite data. The change analyses were performed to figure out the periodic morphodynamic variations and the impact of the flood on the selected meandering structures. In conclusion, although the river water level increased by 0.4–5.9 meters with the flood occurred in January 2019, the sediment deposition areas reformed after the flood event, as the water level decreased. Two-year monitoring revealed that the sinuosity index (SI) values changed during the flood approached the pre-flood values over time. Moreover, it was observed that the amount of the deposited sediments in September 2019 approached that of June 2018.
- Published
- 2020
14. A MULTI-SOURCE DATA APPROACH FOR THE INVESTIGATION OF LAND SUBSIDENCE IN THE KONYA BASIN, TURKEY
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Antonio Pepe, F. Balik Sanli, Jorge Pedro Galve, Murat Yakar, Davide Notti, Fabiana Calò, Hasan Bilgehan Makineci, Osman Orhan, Saygin Abdikan, Tolga Gorum, Selçuk Üniversitesi, Mühendislik Fakültesi, Harita Mühendisliği, Makineci, Hasan Bilgehan, and Zonguldak Bülent Ecevit Üniversitesi
- Subjects
geography ,Hydrogeology ,geography.geographical_feature_category ,Small baseline subset (SBAS) ,Turkey ,010504 meteorology & atmospheric sciences ,Grace ,Global warming ,Sinkholes ,Aquifer ,Subsidence ,Remote sensing ,Structural basin ,010502 geochemistry & geophysics ,01 natural sciences ,Water resources ,Differential SAR interferometry (DInSAR) ,Environmental science ,Physical geography ,Groundwater ,Environmental degradation ,0105 earth and related environmental sciences - Abstract
2018 Geoinformation for Disaster Management Conference, Gi4DM 2018 -- 18 March 2018 through 21 March 2018 -- -- 135177, Groundwater depletion caused by rapid population growth, global climate change, water resources overexploitation is a major concern in many regions of the world. Consequences are not limited to a non-renewable water loss but extend to environmental degradation and geo-hazards risk increase. In areas where excessive groundwater withdrawal occurs, land subsidence induced by aquifer compaction is observed, resulting in severe socio-economic damage for the affected communities. In this work, we apply a multi-source data approach to investigate the fragile environment of Konya plain, central Turkey. The area, which is under strong anthropogenic pressures and faces with serious water-related problems, is widely affected by land subsidence. In order to analyze the spatial and temporal pattern of the subsidence process we use the Small BAseline Subset DInSAR technique to process two datasets of ENVISAT SAR images spanning the 2002-2010 period and to produce ground deformation maps and associated time-series. Results, complemented with meteorological, stratigraphic and piezometric data as well as with land-cover information, allow us to obtain a comprehensive picture of the climatic, hydrogeological and human dynamics of the study area. © Authors 2018. CC BY 4.0 License., Istanbul Üniversitesi National Research Council Consiglio Nazionale delle Ricerche Florida International University Adamawa State University, Mubi European Regional Development Fund European Space Agency: 10050, 1 National Research Council (CNR) of Italy, Institute for the Electromagnetic Sensing of the Environment (IREA), Napoli, Italy - (calo.f, pepe.a)@irea.cnr.it 2 National Research Council (CNR) of Italy, Research Institute for Geo-Hydrological Protection (IRPI), Torino, Italy - davide.notti@irpi.cnr.it 3 Department of Geodynamics, University of Granada, Granada, Spain - jpgalve@ugr.es 4 Department of Geomatics Engineering, Engineering Faculty, Bulent Ecevit University, Zonguldak, Turkey - sabdikan@beun.edu.tr 5 Geography Department, Istanbul University, Istanbul, Turkey - tolga.gorum@istanbul.edu.tr 6 Department of Earth and Environment, Florida International University, Miami, USA - oorhan@fiu.edu 7 Geomatics Engineering Department, Faculty of Engineering, Selcuk University, Konya, Turkey - bilgehanmakineci@gmail.com 8 Geomatics Engineering Department, Faculty of Engineering, Mersin University, Mersin, Turkey - myakar@mersin.edu.tr 9 Department of Geomatic Engineering, Civil Engineering Faculty, Yildiz Technical University, Istanbul, Turkey - fbalik@yildiz.edu.tr, The work was financed by the project Space Advanced Project Excellence in Research and Enterprise (SAPERE) within the Italian Program “Sviluppo e Potenziamento dei Cluster tecnologici Nazionali”. The activities were carried out through the Infrastructure of High Technology for Environmental and Climate Monitoring-PONa3_00363 project of Structural Improvement financed under the National Operational Programme for “Research and Competitiveness 2007–2013,” supported with the European Regional Development Fund and National Resources. ENVISAT ASAR data were provided by European Space Agency (ESA) in the framework of the CAT-1 ESA No. 10050 project.
- Published
- 2018
15. Analysis of deformation patterns through advanced DINSAR techniques in Istanbul megacity
- Author
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Antonio Pepe, F. Balik Sanli, Fabiana Calò, Tolga Gorum, and Saygin Abdikan
- Subjects
lcsh:Applied optics. Photonics ,Small BAseline Subset ,geography ,geography.geographical_feature_category ,Monitoring ,GNSS augmentation ,lcsh:T ,lcsh:TA1501-1820 ,Urban sprawl ,Urban area ,lcsh:Technology ,Metropolitan area ,Hazard ,Deformation ,Megacity ,lcsh:TA1-2040 ,Urban planning ,Differential SAR Interferometry ,Urbanization ,lcsh:Engineering (General). Civil engineering (General) ,Cartography ,TerraSAR-X - Abstract
As result of the Turkey’s economic growth and heavy migration processes from rural areas, Istanbul has experienced a high urbanization rate, with severe impacts on the environment in terms of natural resources pressure, land-cover changes and uncontrolled sprawl. As a consequence, the city became extremely vulnerable to natural and man-made hazards, inducing ground deformation phenomena that threaten buildings and infrastructures and often cause significant socio-economic losses. Therefore, the detection and monitoring of such deformation patterns is of primary importance for hazard and risk assessment as well as for the design and implementation of effective mitigation strategies. Aim of this work is to analyze the spatial distribution and temporal evolution of deformations affecting the Istanbul metropolitan area, by exploiting advanced Differential SAR Interferometry (DInSAR) techniques. In particular, we apply the Small BAseline Subset (SBAS) approach to a dataset of 43 TerraSAR-X images acquired, between November 2010 and June 2012, along descending orbits with an 11-day revisit time and a 3 m × 3 m spatial resolution. The SBAS processing allowed us to remotely detect and monitor subsidence patterns over all the urban area as well as to provide detailed information at the scale of the single building. Such SBAS measurements, effectively integrated with ground-based monitoring data and thematic maps, allows to explore the relationship between the detected deformation phenomena and urbanization, contributing to improve the urban planning and management.
- Published
- 2018
16. Control of style-of-faulting on spatial pattern of earthquake-triggered landslides
- Author
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Emmanuel John M. Carranza and Tolga Gorum
- Subjects
geography ,Environmental Engineering ,geography.geographical_feature_category ,Geographic information system ,business.industry ,Landslide ,Structural engineering ,Fault (geology) ,Environmental Chemistry ,Common spatial pattern ,Spatial representation ,Spatial variability ,General Agricultural and Biological Sciences ,business ,Seismology - Abstract
Predictive mapping of susceptibility to earthquake-triggered landslides (ETLs) commonly uses distance to fault as spatial predictor, regardless of style-of-faulting. Here, we examined the hypothesis that the spatial pattern of ETLs is influenced by style-of-faulting based on distance distribution analysis and Fry analysis. The Yingxiu–Beichuan fault (YBF) in China and a huge number of landslides that ruptured and occurred, respectively, during the 2008 Wenchuan earthquake permitted this study because the style-of-faulting along the YBF varied from its southern to northern parts (i.e. mainly thrust-slip in the southern part, oblique-slip in the central part and mainly strike-slip in the northern part). On the YBF hanging-wall, ETLs at 4.4–4.7 and 10.3–11.5 km from the YBF are likely associated with strike- and thrust-slips, respectively. On the southern and central parts of the hanging-wall, ETLs at 7.5–8 km from the YBF are likely associated with oblique-slips. These findings indicate that the spatial pattern of ETLs is influenced by style-of-faulting. Based on knowledge about the style-of-faulting and by using evidential belief functions to create a predictor map based on proximity to faults, we obtained higher landslide prediction accuracy than by using unclassified faults. When distance from unclassified parts of the YBF is used as predictor, the prediction accuracy is 80 %; when distance from parts of the YBF, classified according to style-of-faulting, is used as predictor, the prediction accuracy is 93 %. Therefore, mapping and classification of faults and proper spatial representation of fault control on occurrence of ETLs are important in predictive mapping of susceptibility to ETLs.
- Published
- 2015
17. Presentation and Analysis of a Worldwide Database of Earthquake-Induced Landslide Inventories: Earthquake-Induced Landslide Inventories
- Author
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Jonathan W. Godt, Kate E. Allstadt, Niels Hovius, Hakan Tanyas, Cees J. van Westen, Tolga Gorum, M. Anna Nowicki Jessee, Odin Marc, Robert G. Schmitt, Hiroshi Sato, Randall W. Jibson, Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation, and UT-I-ITC-4DEarth
- Subjects
Peak ground acceleration ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Database ,Mercalli intensity scale ,Landslide ,Fault (geology) ,010502 geochemistry & geophysics ,computer.software_genre ,01 natural sciences ,ITC-HYBRID ,Centralized database ,Geophysics ,Epicenter ,ITC-ISI-JOURNAL-ARTICLE ,Geological survey ,Frequency distribution ,computer ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
Earthquake‐induced landslide (EQIL) inventories are essential tools to extend our knowledge of the relationship between earthquakes and the landslides they can trigger. Regrettably, such inventories are difficult to generate and therefore scarce, and the available ones differ in terms of their quality and level of completeness. Moreover, access to existing EQIL inventories is currently difficult because there is no centralized database. To address these issues, we compiled EQIL inventories from around the globe based on an extensive literature study. The database contains information on 363 landslide‐triggering earthquakes and includes 66 digital landslide inventories. To make these data openly available, we created a repository to host the digital inventories that we have permission to redistribute through the U.S. Geological Survey ScienceBase platform. It can grow over time as more authors contribute their inventories. We analyze the distribution of EQIL events by time period and location, more specifically breaking down the distribution by continent, country, and mountain region. Additionally, we analyze frequency distributions of EQIL characteristics, such as the approximate area affected by landslides, total number of landslides, maximum distance from fault rupture zone, and distance from epicenter when the fault plane location is unknown. For the available digital EQIL inventories, we examine the underlying characteristics of landslide size, topographic slope, roughness, local relief, distance to streams, peak ground acceleration, peak ground velocity, and Modified Mercalli Intensity. Also, we present an evaluation system to help users assess the suitability of the available inventories for different types of EQIL studies and model development.
- Published
- 2017
18. Geomorphology of the Mount Akdag landslide, Western Taurus range (SW Turkey)
- Author
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Resul Çömert, Tolga Gorum, Cihan Bayrakdar, Uğur Avdan, Anadolu Üniversitesi, Yer ve Uzay Bilimleri Enstitüsü, and Avdan, Uğur
- Subjects
010504 meteorology & atmospheric sciences ,Turkey ,Range (biology) ,Geography, Planning and Development ,010502 geochemistry & geophysics ,01 natural sciences ,Western Taurus ,lcsh:G3180-9980 ,Earth and Planetary Sciences (miscellaneous) ,Geomorphology ,0105 earth and related environmental sciences ,lcsh:Maps ,geography ,geography.geographical_feature_category ,Akdag ,Landform ,Geomorphological mapping ,Sediment ,Landslide ,Rockslide ,Mount ,Geomorphological Mapping ,Scale (map) ,Geology - Abstract
WOS: 000424358600001, This paper presents the results of a geomorphological investigation of Mount Akdag landslide complex, located on the Western Taurus range, SW Turkey. The landslide, resulting in the collapse of a 5 km segment of Mount Akdag, covers an area of 9.8 km(2) and has a volume of about 3 x 108 m(3). The 1: 15,000 scale geomorphological map (Main Map) of the Akdag landslide presented here was produced from a combination of field studies and unmanned aerial vehicle-based DSM, including aerial-photo interpretation and geomorphometric analysis of landforms. The map shows contemporary and past geomorphological hillslope processes and landforms associated with the landslide complex. Our new map suggests that the Akdag landslide was a complex rockslide consisting of multiple landslide types that developed through various movements. We found that 43 highly developed and active mass movements on the main body and side slopes of the landslide made a major contribution to the sediment input. The sediment produced in the upstream severely threatens the touristic site of Saklikent Canyon in the lower catchment via an increasing magnitude of torrents. This map will provide important data for local and national administrators regarding monitoring up-to-date mass-wasting processes, understanding the landslide and its related sedimentary dynamics, and implementing risk assessment and necessary precautions., Scientific Research Projects Coordination Unit of Istanbul University [ONAP 33594 [ID734]]; Anadolu University Scientific Research Projects Commission [1210E156], The authors would like to thank the Scientific Research Projects Coordination Unit of Istanbul University (Project number: ONAP 33594 [ID734]) and Anadolu University Scientific Research Projects Commission for their financial support through grant no. 1210E156.
- Published
- 2017
19. DInSAR-Based Detection of Land Subsidence and Correlation with Groundwater Depletion in Konya Plain, Turkey
- Author
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Saygin Abdikan, Davide Notti, Fabiana Calò, Fusun Balik Sanli, Tolga Gorum, Jorge Pedro Galve, Antonio Pepe, and Zonguldak Bülent Ecevit Üniversitesi
- Subjects
Differential SAR Interferometry (DInSAR) ,010504 meteorology & atmospheric sciences ,Turkey ,remote sensing ,Small BAseline Subset (SBAS) ,GRACE ,subsidence ,sinkholes ,groundwater ,climate change ,Sinkhole ,Climate change ,Aquifer ,010502 geochemistry & geophysics ,01 natural sciences ,lcsh:Science ,0105 earth and related environmental sciences ,Hydrology ,geography ,geography.geographical_feature_category ,Subsidence ,Water resources ,Overexploitation ,Drawdown (hydrology) ,General Earth and Planetary Sciences ,lcsh:Q ,Geology ,Groundwater - Abstract
In areas where groundwater overexploitation occurs, land subsidence triggered by aquifer compaction is observed, resulting in high socio-economic impacts for the affected communities. In this paper, we focus on the Konya region, one of the leading economic centers in the agricultural and industrial sectors in Turkey. We present a multi-source data approach aimed at investigating the complex and fragile environment of this area which is heavily affected by groundwater drawdown and ground subsidence. In particular, in order to analyze the spatial and temporal pattern of the subsidence process we use the Small BAseline Subset DInSAR technique to process two datasets of ENVISAT SAR images spanning the 2002-2010 period. The produced ground deformation maps and associated time-series allow us to detect a wide land subsidence extending for about 1200 km2 and measure vertical displacements reaching up to 10 cm in the observed time interval. DInSAR results, complemented with climatic, stratigraphic and piezometric data as well as with land-cover changes information, allow us to give more insights on the impact of climate changes and human activities on groundwater resources depletion and land subsidence. © 2017, by the authors; licensee MDPI, Basel, Switzerland.
- Published
- 2017
20. Empirical prediction of coseismic landslide dam formation
- Author
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Tolga Gorum, Xuanmei Fan, Qiang Xu, Cees J. van Westen, and David G. Rossiter
- Subjects
Hydrology ,geography ,Multivariate statistics ,geography.geographical_feature_category ,Landslide classification ,Geography, Planning and Development ,Drainage basin ,Landslide ,Landslide susceptibility ,Landslide dam ,Emergency response ,Earth and Planetary Sciences (miscellaneous) ,Digital elevation model ,Geomorphology ,Geology ,Earth-Surface Processes - Abstract
In this study we develop an empirical method to estimate the volume threshold for predicting coseismic landslide dam formation using landscape parameters obtained from digital elevation models (DEMs). We hypothesize that the potential runout and volume of landslides, together with river features, determine the likelihood of the formation of a landslide dam. To develop this method, a database was created by randomly selecting 140 damming and 200 non-damming landslides from 501 landslide dams and > 60 000 landslides induced by the Mw 7.9 2008 Wenchuan earthquake in China. We used this database to parameterize empirical runout models by stepwise multivariate regression. We find that factors controlling landslide runout are landslide initiation volume, landslide type, internal relief (H) and the H/L ratio (between H and landslide horizontal distance to river, L). In order to obtain a first volume threshold for a landslide to reach a river, the runout regression equations were converted into inverse volume equations by taking the runout to be the distance to river. A second volume threshold above which a landslide is predicted to block a river was determined by the correlation between river width and landslide volume of the known damming landslides. The larger of these two thresholds was taken as the final damming threshold. This method was applied to several landslide types over a fine geographic grid of assumed initiation points in a selected catchment. The overall prediction accuracy was 97.4% and 86.0% for non-damming and damming landslides, respectively. The model was further tested by predicting the damming landslides over the whole region, with promising results. We conclude that our method is robust and reliable for the Wenchuan event. In combination with pre-event landslide susceptibility and frequency–size assessments, it can be used to predict likely damming locations of future coseismic landslides, thereby helping to plan emergency response. Copyright © 2014 John Wiley & Sons, Ltd.
- Published
- 2014
21. Why so few? Landslides triggered by the 2002 Denali earthquake, Alaska
- Author
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Freek D. van der Meer, Chong Xu, Oliver Korup, Mark van der Meijde, Cees J. van Westen, Tolga Gorum, Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation, and UT-I-ITC-4DEarth
- Subjects
Archeology ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Institut für Erd- und Umweltwissenschaften ,Sediment ,Geology ,Glacier ,Landslide ,Fjord ,Terrain ,Fault (geology) ,Slope failure ,METIS-303852 ,ITC-ISI-JOURNAL-ARTICLE ,Glacial period ,Geomorphology ,Ecology, Evolution, Behavior and Systematics ,Seismology - Abstract
The 2002 M-w 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of similar to 1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M 8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent slope failure. In order to explore potential controls on the reduced extent of regional coseismic landsliding we compare our data with inventories that we compiled for two recent earthquakes in periglacial and formerly glaciated terrain, i.e. at Yushu, Tibet (M-w 6.9, 2010), and Aysen Fjord, Chile (2007 M-w 6.2). Fault movement during these events was, similarly to that of the Denali earthquake, dominated by strike-slip offsets along near-vertical faults. Our comparison returns very similar coseismic landslide patterns that are consistent with the idea that fault type, geometry, and dynamic rupture process rather than widespread glacier cover were among the first-order controls on regional hillslope erosional response in these earthquakes. We conclude that estimating the amount of coseismic hillslope sediment input to the sediment cascade from earthquake magnitude alone remains highly problematic, particularly if glacierized terrain is involved. (C) 2014 Elsevier Ltd. All rights reserved.
- Published
- 2014
22. Transient water and sediment storage of the decaying landslide dams induced by the 2008 Wenchuan earthquake, China
- Author
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Fuchu Dai, Oliver Korup, Tolga Gorum, Runqiu Huang, Cees J. van Westen, Qiang Xu, Gonghui Wang, Xuanmei Fan, Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation, and UT-I-ITC-4DEarth
- Subjects
Hydrology ,geography ,Institut für Erd- und Umweltwissenschaften ,geography.geographical_feature_category ,Bedrock ,Ephemeral key ,Flux ,Sediment ,Landslide ,Debris ,Landslide dam ,METIS-293942 ,ITC-ISI-JOURNAL-ARTICLE ,Sedimentary budget ,Geomorphology ,Geology ,Earth-Surface Processes - Abstract
Earthquake-triggered landslide dams are potentially dangerous disrupters of water and sediment flux in mountain rivers, and capable of releasing catastrophic outburst flows to downstream areas. We analyze an inventory of 828 landslide dams in the Longmen Shan mountains, China, triggered by the M-w 7.9 2008 Wenchuan earthquake. This database is unique in that it is the largest of its kind attributable to a single regional-scale triggering event: 501 of the spatially clustered landslides fully blocked rivers, while the remainder only partially obstructed or diverted channels in steep watersheds of the hanging wall of the Yingxiu-Beichuan Fault Zone. The size distributions of the earthquake-triggered landslides, landslide dams, and associated lakes (a) can be modeled by an inverse gamma distribution; (b) show that moderate-size slope failures caused the majority of blockages; and (c) allow a detailed assessment of seismically induced river-blockage effects on regional water and sediment storage. Monte Carlo simulations based on volumetric scaling relationships for soil and bedrock failures respectively indicate that 14% (18%) of the estimated total coseismic landslide volume of 6.4 (14.6) x 10(9) m(3) was contained in landslide dams, representing only 1.4% of the >60,000 slope failures attributed to the earthquake. These dams have created storage capacity of similar to 0.6x 10(9) m(3) for incoming water and sediment. About 25% of the dams containing 2% of the total river-blocking debris volume failed one week after the earthquake; these figures had risen to 60% (similar to 20%), and >90% (>90%) within one month, and one:year, respectively, thus also emptying similar to 92% of the total potential water and sediment storage behind these, dams within one year following the earthquake. Currently only similar to 0.08 x 10(9) m(3) remain available as natural reservoirs for storing water and sediment, while similar to 0.19 x 10(9) m(3), i.e. about a third of the total river-blocking debris volume, has been eroded by rivers. Dam volume and upstream catchment area control to first order the longevity of the barriers, and bivariate domain plots are consistent with the observation that most earthquake-triggered landslide dams were ephemeral. We conclude that the river-blocking portion of coseismic slope failures disproportionately modulates the post-seismic sediment flux in the Longmen Shan on annual to decadal timescales.
- Published
- 2012
23. Medium - scale hazard mapping for shallow landslide initiation : the Buyukkoy catchment area, Cayeli, Rize, Turkey
- Author
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Hakan A. Nefeslioglu, Harun Sonmez, Candan Gokceoglu, Tolga Gorum, and Department of Earth Systems Analysis
- Subjects
Variables ,media_common.quotation_subject ,METIS-302806 ,Sampling (statistics) ,Poison control ,Landslide ,Geotechnical Engineering and Engineering Geology ,Hazard ,Current (stream) ,Geography ,Natural hazard ,Physical geography ,Catchment area ,Cartography ,media_common - Abstract
The main purpose of this study is to develop a new hazard evaluation technique considering the current limitations, particularly for shallow landslides. For this purpose, the Buyukkoy catchment area, located in the East Black Sea Region in the east of Rize province and the south of Cayeli district, was selected as the study area. The investigations were executed in four different stages. These were (1) preparation of a temporal shallow landslide inventory of the study area, (2) assessment of conditioning factors in the catchment, (3) susceptibility analyses and (4) hazard evaluations and mapping. A total of 251 shallow landslides in the period of 1955–2007 were recognised using different data sources. A ‘Sampling Circle’ approach was proposed to define shallow landslide initiation in the mapping units in susceptibility evaluations. To accomplish the susceptibility analyses, the method of artificial neural networks was implemented. According to the performance analyses conducted using the training and testing datasets, the prediction and generalisation capacities of the models were found to be very high. To transform the susceptibility values into hazard rates, a new approach with a new equation was developed, taking into account the behaviour of the responsible triggering factor over time in the study area. In the proposed equation, the threshold value of the triggering factor and the recurrence interval are the independent variables. This unique property of the suggested equation allows the execution of more flexible and more dynamic hazard assessments. Finally, using the proposed technique, shallow landslide initiation hazard maps of the Buyukkoy catchment area for the return periods of 1, 2, 5, 10, 50 and 100 years were produced.
- Published
- 2011
24. Description of dynamics of the Tuzla Landslide and its implications for further landslides in the northern slope and shelf of the Cinarcik Basin (Marmara Sea, Turkey)
- Author
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Fatmagül Batuk, Hüseyin Tur, Anisya B. Tekkeli, Erkan Gökaşan, Hakan Alp, M. C. Tunusluoglu, Candan Gokceoglu, Tolga Gorum, Faculty of Geo-Information Science and Earth Observation, and Department of Earth Systems Analysis
- Subjects
geography ,geography.geographical_feature_category ,Mass movement ,Landslide classification ,North Anatolian Fault ,Geology ,Landslide ,Structural basin ,Fault (geology) ,Geotechnical Engineering and Engineering Geology ,ESA ,ADLIB-ART-2773 ,Basement (geology) ,Ridge ,Geomorphology ,Seismology - Abstract
Seismic and multi-beam bathymetric data from the northern shelf and slope of the Cinarcik Basin, which is generated by the North Anatolian Fault Zone (NAFZ) located in the easternmost basin in the Marmara Sea, were re-interpreted to better understand the future sub-marine landslide susceptibility. Seismic data indicate that upper surface of the sub-marine extension of the Paleozoic rocks has an NNE–SSW oriented basin and a ridge type morphology controlled by the secondary faults of the NAFZ. Basins are fulfilled by Plio-Quaternary sediments, which are cut by strike-slip faults on the shelf and slope. The thickness of basin deposits reaches up to 130 m toward the linear northern slope of the Cinarcik Basin. A relatively recent sub-marine landslide, the Tuzla Landslide, cuts the slope of the Cinarcik Basin. The detailed morphological investigation indicates that the Tuzla Landslide is a deep-seated rotational landslide, which was likely triggered by activity of the NAFZ. Morphological analyses also indicate that the thick Plio-Quaternary deposits on the Paleozoic basement slid during the Tuzla Landslide event. This landslide is considered as a key event to understand the dynamics of the potential landslides on the northern shelf and slope of the Cinarcik Basin. Two areas locating on the eastern and the western sides of the Tuzla Landslide are considered as the potential areas for future sliding due to similarities of geological and geomorphological features with the Tuzla Landslide such as similar thick Plio-Quaternary deposits, similar slope morphology, and similar fault activity cutting the sediments. Considering this information, the purposes of the present study are to determine the dynamics of the possible landslide areas and to discuss their effects on the sub-marine morphology. In the light of the interpretations, the amounts of possible displaced material are obtained. Three different landslide scenarios due to possible slide surfaces for future landslides are developed and assessed. The first scenario is sliding of the sediments at the shelf break. The third scenario is a mass movement of almost whole basin deposits on the Paleozoic rocks. The latter one is evaluated as less important because of the volume of the displaced material, and the latter one is accepted as lowest possible event. Among the scenarios, the second scenario is accepted as the most critical and possible because of the amount of the slipped material and existence of faults rupture, which is considered as further sliding surfaces. These landslides will result in important changes in shelf, slope and basin floor in the study area.
- Published
- 2009
25. Faulting, mass-wasting and deposition in an active dextral shear zone, the Gulf of Saros and the NE Aegean Sea, NW Turkey
- Author
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Hakan Alp, Erkan Gökaşan, Dogan Kalafat, Halim Birkan, Hüseyin Tur, Berkan Ecevitoğlu, Fatmagül Batuk, Timur Ustaömer, and Tolga Gorum
- Subjects
geography ,geography.geographical_feature_category ,Pull apart basin ,North Anatolian Fault ,Environmental Science (miscellaneous) ,Structural basin ,Fault (geology) ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Strike-slip tectonics ,Tectonics ,Sinistral and dextral ,Earth and Planetary Sciences (miscellaneous) ,Shear zone ,Seismology ,Geology - Abstract
Structural, mass-wasting and sedimentation processes along an active dextral shear zone beneath the Gulf of Saros and the NE Aegean Sea were investigated on the basis of new high-resolution swath bathymetric data and multi-channel seismics. A long history of dextral shearing operating since the Pliocene culminated in the formation of a NE-SW-trending, ca. 800-m-deep basin (the so-called inner basin) in this region, which is bordered by a broad shelf along its northern and eastern sides and a narrow shelf at the southern side. The western extension of the North Anatolian Fault Zone (the Ganos Fault) cuts the eastern shelf along a narrow deformation zone, and ends sharply at the toe of the slope, where the strain is taken up by two NE-SW-oriented fault zones. These two fault zones cut the basin floor along its central axis and generate a new, Riedel-type pull-apart basin (the so-called inner depression). According to the bathymetric and seismic data, these basin boundary fault zones are very recent features. The northern boundary of the inner depression is a through-going fault comprising several NE-SW- and E-W-oriented, overlapping fault segments. The southern boundary fault zone, on the other hand, consists of spectacular en-echelon fault systems aligned in NE–SW and WNW–ESE directions. These en-echelon faults accommodate both dextral and vertical motions, thereby generating block rotations along their horizontal axis. As the basin margins retreat, the basin widens continuously by mass-wasting of the slopes of the inner basin. The mass-wasting, triggered by active tectonics, occurs by intense landsliding and channel erosion. The eroded material is transported into the deep basin, where it is deposited in a series of deep-sea fans and slumps. The high sedimentation rate is reflected in an over 1,500-m-thick basin fill which has accumulated in Pliocene–Quaternary times.
- Published
- 2008
26. Factors controlling the morphological evolution of the Çanakkale Strait (Dardanelles, Turkey)
- Author
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Tolga Gorum, Erhan Gezgin, Hakan Alp, Mustafa Özyalvaç, Ahmet Türker, Erkan Gökaşan, Halil İbrahim Sur, Timur Ustaömer, Fatmagül Batuk, Mustafa Ergin, Halim Birkan, Hüseyin Tur, and Murat Özturan
- Subjects
geography ,geography.geographical_feature_category ,Sediment ,North Anatolian Fault ,Environmental Science (miscellaneous) ,Present day ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Seafloor spreading ,Tectonics ,Acoustic Doppler current profiler ,Peninsula ,Earth and Planetary Sciences (miscellaneous) ,Bathymetry ,Geology - Abstract
Seismic profiling, bathymetric and physical oceanographic data collected from the Canakkale Strait revealed that the morphological evolution of the strait has been controlled by tectonic activity, and sediment erosion and deposition. Sediments in the strait have been sourced mostly by rivers draining the Biga Peninsula during lowstand periods. In highstand periods, by contrast, deposits in the strait were reworked by currents. The seafloor morphology of the Canakkale Strait is also controlled by a sequence of factors ranging from tectonics to current erosion and deposition. Channel deposits overlying the basement are being eroded at the narrower, meandering central section of the strait (the Nara Passage) due to high current velocities. The eroded sediments are deposited in the relatively linear and wider, northern and southern sectors of the strait exposed to low current velocities. As a result, the high-energy areas are more deeply incised due to the erosion, whereas deposition elevates the seafloor in the areas exposed to lower current energy. Three strike-slip faults, which possibly relate to the activity of the North Anatolian Fault Zone, are responsible for the irregular shape of the strait and this, in turn, controls the current velocity along the strait. The high-energy conditions probably commenced with the latest invasion of Mediterranean waters some 12 ka b.p., and have continued as a two-layered current system to the present day.
- Published
- 2007
27. Quaternary evolution of the Gulf of İzmit (NW Turkey): a sedimentary basin under control of the North Anatolian Fault Zone
- Author
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Engin Meriç, Tolga Gorum, Oktay Çetin, Erdal Dolu, Hüseyin Tur, Fatmagül Batuk, Mustafa Ergin, Buğser Tok, Niyazi Avşar, Erkan Gökaşan, Berkan Ecevitoğlu, Muhittin Görmüş, and Çukurova Üniversitesi
- Subjects
geography ,geography.geographical_feature_category ,North Anatolian Fault ,Environmental Science (miscellaneous) ,Sedimentary basin ,Fault (geology) ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Sedimentary depositional environment ,Paleontology ,Earth and Planetary Sciences (miscellaneous) ,Sedimentary rock ,Glacial period ,Shear zone ,Quaternary ,Geomorphology ,Geology - Abstract
The Quaternary evolution of the Gulf of Izmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence of the Gulf of Izmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into the gulf from the south since 200 ka indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level fluctuations in the Marmara Sea. During this period, the Gulf of Izmit was invaded mainly by Mediterranean and partly by Black Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western sub-basins of the gulf turned into lakes. The present evolution of the Gulf of Izmit is controlled by the after effects of the new rupture of the NAFZ and the estuarine nature of the gulf environment. © Springer-Verlag 2007. Istanbul Üniversitesi Acknowledgements This paper is based on the MSc thesis of Erdal Dolu. We gratefully acknowledge the captains and crews as well as the scientists and technicians of the R/V Arar of Istanbul University, and the R/V TCG Çubuklu of the Turkish Navy, Department of Navigation, Hydrography and Oceanography, for their help during the bathymetric and seismic surveys. We thank Dr. Timur Ustaömer for his very valuable criticism. We also acknowledge the helpful comments of two anonymous referees and the editor of the journal, Dr. Burg Flemming, to improve the paper.
- Published
- 2007
28. The space-borne DInSAR technique as a supporting tool for sustainable policies: the case of Istanbul megacity, Turkey
- Author
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Saygin Abdikan, Antonio Pepe, Tolga Gorum, Fabiana Calò, Fusun Balik Sanli, Havvanur Kılıç, and Zonguldak Bülent Ecevit Üniversitesi
- Subjects
Risk ,Differential SAR Interferometry (DInSAR) ,Disaster risk reduction ,Turkey ,business.industry ,Urbanization ,Vulnerability ,Small BAseline Subset (SBAS) ,Hazard ,Geography ,Megacity ,urban deformations ,Urban planning ,Natural hazard ,hazard ,risk ,urbanization ,Istanbul ,General Earth and Planetary Sciences ,lcsh:Q ,lcsh:Science ,business ,Environmental planning ,Risk management ,Remote sensing - Abstract
In today's urbanizing world, home of 28 megacities, there is a growing need for tools to assess urban policies and support the design and implementation of effective development strategies. Unsustainable practices of urbanization bring major implications for land and environment, and cause a dramatic increase of urban vulnerability to natural hazards. In Istanbul megacity, disaster risk reduction represents a challenging issue for urban managers. In this paper, we show the relevance of the space-borne Differential SAR Interferometry (DInSAR) technique as a tool for supporting risk management, and thus contributing to achieve the urban sustainability. To this aim, we use a dataset of high resolution SAR images collected by the TerraSAR-X satellite that have been processed through the advanced (multi-temporal) Small BAseline Subset (SBAS)-DInSAR technique, thus producing spatially-dense deformation velocity maps and associated time-series. Results allow to depict an up-to-date picture of surface deformations occurring in Istanbul, and thus to identify urban areas subject to potential risk. The joint analysis of remotely sensed measurements and ancillary data (geological and urban development information) provides an opportunity for city planners and land professionals to discuss on the mutual relationship between urban development policies and natural/man-made hazards. © 2015 by the authors.
- Published
- 2015
29. Evidence and implications of massive erosion along the Strait of İstanbul (Bosphorus)
- Author
-
Mehmet Simsek, Hüseyin Tur, Faruk Caglak, Erkan Gökaşan, Halim Birkan, Berkan Ecevitoğlu, Ahmet Türker, Tolga Gorum, and Buğser Tok
- Subjects
geography ,geography.geographical_feature_category ,Sediment ,Submarine canyon ,Environmental Science (miscellaneous) ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Deposition (geology) ,Seafloor spreading ,Current (stream) ,Earth and Planetary Sciences (miscellaneous) ,Erosion ,Bathymetry ,Geology ,Channel (geography) - Abstract
The Strait of Istanbul (SoI) (Bosphorus) is a narrow valley, which has evolved tectonically from a stream, and in which thick sediment deposits have accumulated in the course of its evolution. Detailed seismic and multi-beam bathymetric data have revealed that the upper parts of the deeper channel deposits consist of parallel strata, which have mostly been eroded subsequently to their deposition. The resulting erosion surface is represented by the present channel floor in the strait, the estimated volume of the eroded material being approximately 2×108 m3 . Erosion rate and seafloor morphology indicate that the flow direction was from the south to the north. This inner channel may have been formed by an abrupt flooding of the Black Sea by Mediterranean waters at the beginning of the latest connection between the Marmara and the Black seas. Subsequently, the Mediterranean bottom current of the modern two-way flow system, which was established at about 5–4 ka b.p., has given the latest shape to the strait floor.
- Published
- 2005
30. Complex rupture mechanism and topography control symmetry of mass - wasting pattern, 2010 Haiti earthquake
- Author
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Mark van der Meijde, Xuanmei Fan, Oliver Korup, Cees J. van Westen, Freek D. van der Meer, Tolga Gorum, Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation, and UT-I-ITC-4DEarth
- Subjects
geography ,geography.geographical_feature_category ,Landslide ,Slip (materials science) ,Mass wasting ,Fault (geology) ,Instability ,Rockfall ,METIS-293985 ,IR-90293 ,Slope stability ,ITC-ISI-JOURNAL-ARTICLE ,Thrust fault ,Geology ,Seismology ,Earth-Surface Processes - Abstract
The 12 January 2010 Mw 7.0 Haiti earthquake occurred in a complex deformation zone at the boundary between the North American and Caribbean plates. Combined geodetic, geological and seismological data posited that surface deformation was driven by rupture on the Leogâne blind thrust fault, while part of the rupture occurred as deep lateral slip on the Enriquillo–Plantain Garden Fault (EPGF). The earthquake triggered > 4490 landslides, mainly shallow, disrupted rock falls, debris-soil falls and slides, and a few lateral spreads, over an area of ~ 2150 km2. The regional distribution of these slope failures defies those of most similar earthquake-triggered landslide episodes reported previously. Most of the coseismic landslides did not proliferate in the hanging wall of the main rupture, but clustered instead at the junction of the blind Leogâne and EPGF ruptures, where topographic relief and hillslope steepness are above average. Also, low-relief areas subjected to high coseismic uplift were prone to lesser hanging wall slope instability than previous studies would suggest. We argue that a combined effect of complex rupture dynamics and topography primarily control this previously rarely documented landslide pattern. Compared to recent thrust fault-earthquakes of similar magnitudes elsewhere, we conclude that lower static stress drop, mean fault displacement, and blind ruptures of the 2010 Haiti earthquake resulted in fewer, smaller, and more symmetrically distributed landslides than previous studies would suggest. Our findings caution against overly relying on across-the-board models of slope stability response to seismic ground shaking.
- Published
- 2013
31. Analysis of landslide dams induced by the 2008 Wenchuan earthquake
- Author
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Fuchu Dai, Cees J. van Westen, Tolga Gorum, Xuanmei Fan, Qiang Xu, Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation, and UT-I-ITC-4DEarth
- Subjects
geography ,geography.geographical_feature_category ,Landslide classification ,Geology ,Landslide ,Fault (geology) ,Landslide dam ,Tectonics ,Landslide mitigation ,METIS-293943 ,ITC-ISI-JOURNAL-ARTICLE ,Thrust fault ,Geomorphology ,Channel (geography) ,Earth-Surface Processes - Abstract
Landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers, capable of delivering large outburst floods that may devastate downstream areas. We analyzed a unique inventory of 828 landslide dams triggered by the M w 7.9 2008 Wenchuan tectonic earthquake, China, constituting ∼1.4% of the >60,000 coseismic slope failures mapped and attributed to this event. While 501 landslides blocked the rivers completely, the remainder caused only partial damming or channel diversion. The spatial distribution of landslide dams follows the same trend of that of the total landslide distribution, with landslide dams being most abundant in the steep watersheds of the hanging wall of the Yingxiu-Beichuan Thrust Fault, and in the northeastern part of the strike-slip fault near Qingchuan. Besides the co-seismic landslide density, the river width also played a key role in determining the landslide dam formation. Narrow rivers are more prone to be dammed than the wide rivers. The correlation between river width and landslide dam volume follows a linear relation, which can be used to roughly estimate the dam formation possibility. However, the applicability of this correlation needs to be validated in other regions. The decay (failure) rate of dams, defined here as the percentage of the number and area of landslide dams that have failed over time, shows that ∼25% of dams accounting for ∼30% of total landslide dam area failed one week after the earthquake. These percentages increased to ∼60% within 1 month, and to >90% within 1 year. The geomorphometric parameters were analyzed, revealing power-law relations between landslide area and dam width, landslide source area and dam area, as well as lake area and lake volume. The inventory presented in this study will enrich the worldwide earthquake-induced landslide dam database and will also contribute to a better understanding of the post-earthquake dam decay.
- Published
- 2012
32. Landform effect on rockfall and hazard mapping in Cappadocia (Turkey)
- Author
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Candan Gokceoglu, M. Celal Tunusluoglu, Tolga Gorum, Kıvanç Zorlu, Dilek Turer, Ali Yalcin, Hakan A. Nefeslioglu, Mühendislik Fakültesi, Gorum, Tolga -- 0000-0001-9407-7946, Gokceoglu, Candan -- 0000-0003-4762-9933, Zorlu, Kivanc -- 0000-0002-2086-7379, and Nefeslioglu, Hakan -- 0000-0003-1117-6012
- Subjects
Hazard mapping ,Ignimbrite ,Global and Planetary Change ,geography ,Rockfall ,geography.geographical_feature_category ,Landform ,Outcrop ,Soil Science ,Geology ,Neogene ,Hazard map ,Cappadocia ,Pollution ,Butte ,Environmental Chemistry ,Mesa ,Geomorphology ,Earth-Surface Processes ,Water Science and Technology - Abstract
WOS: 000288802500012, The Cappadocia region has unique geomorphological features resulting from differential erosional processes which make it very attractive to tourists. Besides the fairy chimneys for which the area is best known, there are also impressive buttes and mesas. Buttes and mesas are formed in regions having flat-lying strata in which the uppermost levels are composed of well-cemented limestones and granular ignimbrites, whereas the lower parts and slopes consist of low-durability tuff and ignimbrites. This durability difference results in serious rockfall events. This study involves two-dimensional rockfall analyses in and near the Avanos, Zelve, and Cavusini areas, where volcano-sedimentary units of Neogene age outcrop, to provide a rockfall hazard map in which areas of tourism activity are also considered.
- Published
- 2011
33. Late quaternary evolution of the Canakkale Strait region, Dardanelles, NW Turkey : implications of a major erosional event for the postglacial Mediterranean - Marmara sea connection
- Author
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Fatma Guel Batuk, Hueseyin Tur, Tolga Gorum, Nurcan Sagci, Hakan Alp, Timur Ustaömer, Ozan Emem, Mustafa Ergin, Erkan Gökaşan, and Department of Earth Systems Analysis
- Subjects
Marine isotope stage ,Canyon ,geography ,geography.geographical_feature_category ,METIS-304384 ,Environmental Science (miscellaneous) ,Structural basin ,Geotechnical Engineering and Engineering Geology ,Oceanography ,Unconformity ,Paleontology ,Basement ,Sill ,Earth and Planetary Sciences (miscellaneous) ,Bathymetry ,Quaternary ,Geology - Abstract
Seismic and bathymetric data from the Canakkale Strait and its extensions onto the shelves of the Marmara and Aegean seas indicate that the strait was formed mainly by an erosional event. Four seismic units are observed on seismic profiles. The lower two of these (units 4 and 3) constitute the basement of a regionally widespread erosional unconformity (ravinement), which developed during marine isotope stage 2 (MIS 2). The two upper units (units 2 and 1), which overlie the ravinement surface, form a higher-order sequence. Sequence stratigraphic analysis indicates that units 2 and 1 deposited as lowstand and highstand systems tracts respectively, since the end of MIS 2. The transgressive systems tract is represented by a major erosional event which occurred throughout the Canakkale sill area when the Mediterranean-Marmara Sea connection and, hence, the Canakkale Strait was formed. The existence of the erosive Sarkoy Canyon along the shelf edge of the southern Marmara Sea demonstrates that the flow direction causing the erosion was from south to north, thus proving that it was produced by Mediterranean water flowing over the sill into the Marmara Sea basin.
- Published
- 2010
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