Application of Chebyshev theorem to data preparation in landslide susceptibility mapping studies:an example from Yenice(Karabük,Turkey) region

Landslide database construction is one of the most crucial stages of the landslide susceptibility mapping studies. Although there are many techniques for preparing landslide database in the literature, representative data selection from huge data sets is a challenging, and, to some extent, a subjective task. Thus, in order to produce reliable landslide susceptibility maps, data-driven, objective and representative database construction is a very important stage for these maps. This study mainly focuses on a landslide database construction task. In this study, it was aimed at building a representative landslide database extraction approach by using Chebyshev theorem to evaluate landslide susceptibility in a landslide prone area in the Western Black Sea region of Turkey. The study area was divided into two different parts such as training (Basin 1) and testing areas (Basin 2). A total of nine parameters such as topographical elevation, slope, aspect, planar and profile curvatures, stream power index, distance to drainage, normalized difference vegetation index and topographical wetness index were used in the study. Next, frequency distributions of the considered parameters in both landslide and nonlandslide areas were extracted using different sampling strategies, and a total of nine different landslide databases were obtained. Of these, eight databases were gathered by the methodology proposed by this study based on different standard deviations and algebraic multiplication of raster parameter maps. To evaluate landslide susceptibility, Artificial Neural Network method was used in the study area considering the different landslide and nonlandslide data. Finally, to assess the performances of the so-produced landslide susceptibility maps based on nine data sets, Area Under Curve (AUC) approach was implemented both in Basin 1 and Basin 2. The best performances (the greatest AUC values) were gathered by the landslide susceptibility map produced by two standard deviation database extracted by the Chebyshev theorem, as 0.873 and 0.761, respectively. Results revealed that the methodology proposed by this study is a powerful and objective approach in landslide susceptibility mapping.     

Late Pleistocene–Holocene history of the Golden Horn Estuary,Istanbul

The historical Golden Horn Estuary (GHE), near the confluence of the Istanbul Strait (Bosphorus) and the Sea of Marmara in the European part of Istanbul, has been used as a natural harbor since 330 a.d. The sedimentary infill of the GHE is 15–46 m thick, deposited unconformably above the turbiditic sandstones of the Carboniferous Trakya Formation. Chronostratigraphic and paleontological analyses of the infill sequence indicate that the GHE was a fluvial channel prior to 13,500 cal. a (calibrated to calendar years) B.P. It subsequently became gradually influenced by marine waters, and was a brackish-water environment until 9,500 cal. a B.P. Normal marine salinities prevailed at ca. 9,500−5,600 cal. a B.P., with suboxic/dysoxic bottom-water conditions. The increase in salinity at 9,500 cal. a B.P. was most likely caused by Mediterranean water outflow into the Black Sea through the Istanbul Strait. The estuary was influenced by large fluvial inputs between 5,600 and 1,000 cal. a B.P., possibly during a distinct pluvial period, as shown by coarse siliciclastic sediments deposited on the flanks. It has become a highly polluted environment with marked anthropogenic inputs during the last millennium. The finding that the sediment infill sequence above the Carboniferous basement is not older than about 20 ka strongly suggests that the Golden Horn Estuary acquired its present-day morphology during the late glacial–Holocene period.     

Ground-motion characterization for the probabilistic seismic hazard assessment in Turkey

This study describes the methodology implemented to establish the ground-motion logic-tree for national probabilistic seismic hazard map of Turkey for shallow active crustal regions. The presented procedure provides quantitative information to guide the hazard experts while establishing the logic tree to capture the epistemic uncertainty in ground-motion characterization. It uses non-data-driven and data-driven testing methods to identify and rank candidate ground-motion prediction equations (GMPEs) under a specific ground-motion database. The candidate GMPEs are subjected to visual inspection and are classified into center, body and range (CBR) spectral estimates for a proper consideration of epistemic uncertainty. The GMPEs classified into CBR are then used in a suite of seismic hazard sensitivity analysis to establish the most suitable GMPE logic-tree whose spectral estimates are not biased by any one of the GMPEs in the logic-tree structure. The sensitivity analysis considers normalized spectral ordinates and is not manipulated by the spectral amplitudes. The proposed procedure is inherited from the relevant studies of the Earthquake Model of the Middle East (EMME; www.efehr.org:8080/jetspeed/portal/emme.psml) regional seismic hazard project. This paper also highlights the similarities and differences in ground-motion characterization between EMME and our approach.     

A statistical analysis of seismo-ionospheric TEC anomalies before 63 <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> ≥ 5.0 earthquakes in Turkey during 2003–2016

In this study, pre-seismic and post-seismic total electron content (TEC) anomalies of 63 M_w?≥?5.0 earthquakes in Turkey (36°–42°N, 26°–45°E) were statistically investigated. The largest earthquake that occurred in Turkey during 2003–2016 is the M_w 7.1 Van earthquake on October 23, 2011. The TEC data of epicenters is obtained from CODE-GIM using a simple 4-point bivariate interpolation. The anomalies of TEC variations were determined by using a quartile-based running median process. In order to validate GIM results, we used the GPS-TEC data of available four IGS stations within the size of the Van earthquake preparation area. The anomalies that are detected by GIM and GPS-TEC show a similar pattern. Accordingly, the results obtained with CODE-GIM are reliable. The statistical results show that there are not prominent earthquake precursors for M_w?≤?6.0 earthquakes in Turkey.     

A probabilistic seismic hazard assessment for the Turkish territory: part II—fault source and background seismicity model

Over the years, several local and regional seismic hazard studies have been conducted for the estimation of the seismic hazard in Turkey using different statistical processing tools for instrumental and historical earthquake data and modeling the geologic and tectonic characteristics of the region. Recently developed techniques, increased knowledge and improved databases brought the necessity to review the national active fault database and the compiled earthquake catalogue for the development of a national earthquake hazard map. A national earthquake strategy and action plan were conceived and accordingly with the collaboration of the several institutions and expert researchers, the Revision of Turkish Seismic Hazard Map Project (UDAP-Ç-13-06) was initiated, and finalized at the end of 2014. The scope of the project was confined to the revision of current national seismic hazard map, using the state of the art technologies and knowledge of the active fault, earthquake database, and ground motion prediction equations. The following two seismic source zonation models are developed for the probabilistic earthquake hazard analysis: (1) Area source model, (2) Fault and spatial smoothing seismic source model (FSBCK). In this study, we focus on the development and the characterization of the Fault Source model, the background spatially smoothed seismicity model and intrinsic uncertainty on the earthquake occurrence-rates-estimation. Finally, PSHA results obtained from the fault and spatial smoothed seismic source model are presented for 43, 72, 475 and 2475 years return periods (corresponding to 69, 50, 10, and 2% probability of exceedance in 50 years) for PGA and 5% damped spectral accelerations at 0.2 and 1.0 s.     

Evaluation of groundwater quality and contamination around fluorite mineralization,Kaman region,Central Anatolia,Turkey

Groundwater can be exposed to pollution and therefore the quality will be affected in areas of fluorite mineralization. Distribution of fluorite mineralization in the area, its formation type and hydrogeological characteristics of these rocks are a factor of the pollution parameters in groundwater. Syenite, nephelinesyenite and micro gabbro type alkaline rocks are exposed in the Kaman region. Hydrothermal fluorite mineralization is formed in fractures and fissures of the syenite and nepheline-syenites in the study area. The fluoride values of these rocks vary between 480–11990 ppm. These high fluoride concentrations in the rocks result in fluoride contamination in groundwater.     

Critical evaluation of strong motion in Kocaeli and Düzce (Turkey) earthquakes

Turkey was struck by two major events on August 17th and November 12th, 1999. Named Kocaeli (M_w=7.4) and Düzce (M_w=7.2) earthquakes, respectively, the two earthquakes provided the most extensive strong ground motion data set ever recorded in Turkey. The strong motion stations operated by the General Directorate of Disaster Affairs, the Kandilli Observatory and Earthquake Research Institute of Bogazici University and Istanbul Technical University have produced at least 27 strong motion records for the Kocaeli earthquake within 200 km of the fault. Kocaeli earthquake has generated six motions within 20 km of the fault adding significantly to the near-field database of ground motions for M_w>=7.0 strike–slip earthquakes. The paper discusses available strong motion data, studies their attenuation characteristics, analyses time domain, as well as spectral properties such as spectral accelerations with special emphasis on fault normal and fault parallel components and the elastic attenuation parameter, kappa. A simulation of the Kocaeli earthquake using code FINSIM is also presented.     

Landfill Leachate Treatment: A Case Study for Istanbul City

One of the most important problems arising from landfilling solid wastes is the leachate which contains high amount of pollution. Discharge of leachate without treatment causes negative effects on environmental and public health. In this study, parameters of chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH₄‐N), and total phosphorus (TP) were examined in the samples taken from the influent and effluent of leachate treatment plant, where Odayeri landfill leachate is treated. Obtained results showed that the treatment plant, which consisted of preanoxic biological treatment system, ultrafiltration (UF) and nanofiltration (NF) units were operating with high efficiency. Among the examined parameters during study, COD, TN, NH₄‐N, and TP were found to be treated at the rate of 99, 94.5, 99, and 93.8%, respectively. Landfilling is increasing rapidly in the world and this consequently brings the need of leachate treatment facilities. Therefore, this study is considered to be a guide for construction and operation stages of proposed new treatment plants.     

The effect of cubic specimen size on uniaxial compressive strength of carbonate rocks from Western Turkey

One of the most important quality and design parameters of natural rock materials is uniaxial compressive strength (UCS). UCS value of a building stone determines its application area such as cladding, roofing, facing, and coverings. In rock mechanics and engineering practice determination of UCS values of rock materials is suggested on core specimens whereas in construction and building stone sector, cubic specimens are suggested. In this experimental study, the effect of cubic specimen size on UCS values of some carbonate rocks which are being used as dimension stones are investigated. A total of 299 cubic specimens at five different edge sizes (3, 5, 7, 9, and 11 cm) from limestone, marble, and travertine are prepared. Chemical, petrographic analyses and physical properties of specimens are determined and after that UCS tests are carried out. It is observed that as the specimen sizes increase from 3 to 11 cm, average UCS values decrease about 7% for the tested carbonate rocks. In the light of this finding, results of UCS tests could be interpreted considering cubic specimen sizes for the same rock types in various fields.