A newly developed seismic microzonation model of Erbaa (Tokat, Turkey) located on seismically active eastern segment of the North Anatolian Fault Zone (NAFZ)

A methodology to model seismic microzonation maps is required in the hazard mitigation decision plans of the earthquake prone areas. The stage of disaster preparedness for new residential places is of great importance for detailed seismic microzonation models. The effects of local geological and geotechnical site conditions were considered in order to establish site characterization as the initial stage of the models in this study. Dynamic soil properties based on the empirical correlations between shear wave velocity (V _s) and standard penetration test blow counts were taken into account in order to define representative soil profiles extending down to the engineering bedrock. One-dimensional site response analyses were performed to analyze earthquake characteristics on the ground surface. The layers for soil classification, geology, depth to groundwater level, amplification, distance to fault, slope and aspect, and liquefaction-induced ground deformation potential of the study area were prepared in seismic microzonation models. The study area, Erbaa, is placed along the seismically active North Anatolian Fault Zone. Final seismic microzonation map of the study area was evaluated applying different GIS-based Multi-Criteria Decision Analysis (MCDA) techniques. Two of the MCDA techniques, simple additive weighting and analytical hierarchical process (AHP), are considered during the evaluation step of the final seismic microzonation map. The comparison is made in order to distinguish two different maps based on these MCDA techniques. Eventually, AHP-based seismic microzonation map is more preferable for the seismic design purposes in this study.     

GIS-based microzonation of the Niksar settlement area for the purpose of urban planning (Tokat, Turkey)

Niksar (Tokat) is an urban area located in a seismically active zone of Turkey. The aim of this study is to prepare a GIS-based microzonation map of the Niksar settlement area for the purpose of urban planning. Liquefaction, activity, slope, aspect, fault proximity, ground amplification, and lithology are considered during the overlay analysis, using a multicriteria decision-making analysis of the analytical hierarchy process (AHP) and simple additive weighing (SAW) methods. Based on the resulting evaluations, the study area is divided into four different zones, namely (1) areas suitable for settlement, (2) provisional settlement areas, (3) areas requiring detailed geotechnical investigation, and (4) unsuitable areas. Maps prepared by the SAW and AHP methods are found to be consistent with each other. However, the microzonation map prepared by the AHP method is recommended for the purpose of urban planning because it is able to check its own consistency.     

Seismic site characterization and site response study of Nirsa (India)

Natural Hazards - The Nirsa block, a coal mining area, and an industrial town lies in the southern part of Dhanbad district, at the border between the Indian states of Jharkhand and West Bengal....     

Determination of natural radioactivity levels in soil and travertine of the region of Tokat and Sivas,Turkey

In this study, the environmental radioactivity measurements for Tokat and Sivas provinces in the northeast of Turkey were performed. Using gamma ray spectrometry, the activity concentrations of natural radionuclides in soil and travertine samples (²³²Th, ²²⁶Ra, and ⁴⁰K) were determined. The annual effective dose equivalent, the absorbed doses rate in air, the radium equivalent, and the external hazard index were obtained from these activities. The activity concentrations vary from 9.09 to 17.04 Bq kg^?1 for ²³²Th, from 36.53 to 76.95 Bq kg^?1 for ²²⁶Ra, and from 216.56 to 576.59 Bq kg^?1 for ⁴⁰K in soil samples. The activity concentrations in travertines vary from 15.99 to 21.01 Bq kg^?1 for ²³²Th, from 19.89 to 67.71 Bq kg^?1 for ²²⁶Ra, and from 179.89 to 314.43 Bq kg^?1 for ⁴⁰K. The average dose rate in air for soil and travertine samples was 43.41 and 41.05 nGy h^?1 respectively. The obtained results are presented and compared with other studies, and the results of this study are lower than the international recommended value (55 nGy h^?1) given by UNSCEAR ( 2000). The results show that the region has a background radiation level within the natural limits.     

The Geology and Evolution of the Tokat Massif,South-Central Pontides,Turkey

The Tokat Massif is a major metamorphic complex of the south-central Pontides, the origin and development of which have long remained unknown. Recent detailed field-based mapping has revealed the major geological features of this complex. The Tokat Massif appears to be a tectonic mosaic composed of three major components: (1) the Yesilirmak Group; (2) the Turhal Metaophiolite; and (3) the Amasya Group. The Yesilirmak Group, which consists of a coherent lithoiogical sequence involving Paleozoic basement and overlying Triassic units, represents a short-lived basin assemblage. The Turhal Metaophiolite consists of an ophiolitic melange association and slices of a stratigraphically ordered ophiolite. The Amasya Group, the highest-standing tectonic unit, is represented by a lower Paleozoic clastic succession.

The different major tectonostratigraphic assemblages of the Tokat Massif record a continent-continent collision between the Laurasian Amasya Group and the Gondwanan Yesilirmak Group. The Turhal Metaophiolite, sandwiched between the two continental fragments, represents remnants of an oceanic realm that was consumed between the two continents. The three major tectonic components were assembled and underwent regional metamorphism during the Late Triassic-Liassic transition, and were later covered during the Liassic by basal detrital units.     

Structural and geomorphological aspects of the Kat landslides (Tokat—Turkey) and susceptibility mapping by means of GIS

Kat County, which is located in a slope of hilly region and constructed in the side of a mountain along the North Anatolian Fault Zone, is frequently subject to landslides. The slides occur during periods of heavy rainfall, and these events cause destruction to property, roads, agricultural lands and buildings. In the last few decades, a lot of houses and buildings have been damaged and destroyed. Settlement areas have remained evacuated for a long time. The slope instabilities in the study area are a complex landslide extending from north to south containing a lot of landslides. Field investigations, interpretation of aerial photography, analyses of geological data and laboratory tests suggest that some factors have acted together on the slopes to cause the sliding. In the wet season, the slopes became saturated. As the saturation of the earth material on the slope causesa rise in water pressure, the shear strength (resisting forces) decreases and the weight (driving forces) increases; thus, the net effect was to lower the safety factor. Previous failures have affected the rock mass, leading to the presence of already sheared surfaces at residual strengths. The relation between the joint planes and the instability of the slope in the study area was discussed and it was found that the potential slope instabilities are mainly in the directions of NW–SE, NE–SW and N–S. The landslide susceptibility map obtained by using the geographical information system showed that a large area is susceptible and prone to landslides in the northern part of the study area.An erratum to this article can be found at     

Geochemistry and geochronology of meta-igneous rocks from the Tokat Massif, north-central Turkey: implications for Tethyan reconstructions

Located in the eastern Pontides of the Sakarya Zone in north-central Turkey, the Tokat Massif records the closure of both the Paleo-Tethyan (Karakaya Complex) and Neo-Tethyan ocean basins. Meta-igneous samples collected from the region were studied to determine their sources and ages. We find significant geochemical differences between metagabbros of the Karakaya and Neo-Tethyan units in terms of their trace elements: Neo-Tethyan rocks are consistent with generation in an island arc setting, whereas Karakaya assemblages were likely generated in an oceanic spreading-center environment. Karakaya metagabbros also contain glaucophane, consistent with subduction subsequent to formation. Small (2–50 μm) zircon and baddeleyite grains from four Karakaya metagabbros were dated in thin section using an ion microprobe. The results demonstrate the reliability of the method to directly constrain the tectonomagmatic history of these types of assemblages. The rocks yield Late Permian/Early Triassic ²³⁸U/²⁰⁶Pb crystallization ages of 258 ± 14 Ma (±1σ, zircon) and 254 ± 8 Ma (±1σ, baddeleyite) and an Early Cretaceous minimum metamorphic age of 137 ± 8 Ma (±1σ, zircon). Some zircon grains and baddeleyite grains with zircon overgrowths yield Early to Middle Jurassic ages. Here we present a model in which metamorphism and deformation in this region occurred during northward subduction and closure of a Paleo-Tethyan ocean basin and accretion of the Karakaya units to the Laurasian continental margin. This was followed by the onset of closure of the Neo-Tethys during the Campanian-Paleocene and accretion of island arc units to the Tokat region.     

Landfill site selection and landfill liner design for Ankara, Turkey

Considering the high population growth rate of Ankara, it is inevitable that landfill(s) will be required in the area in the near future to sustain the sanitary waste disposal needs of the city. The main scope of this study is to select alternative landfill sites for Ankara based on the growing trends of Ankara toward the northwest, particularly toward the Sincan municipality, and to eventually select the best alternative through utilizing multi-criteria decision making. Landfill site selection was carried out utilizing Geographic Information System (GIS) and Multi-Criteria Decision Analysis. A number of criteria, namely, settlement, slope, proximity to roads, geology, availability and proximity of landfill containment material (i.e., clay for composite lining system), suitability for agriculture, erosion, vegetation cover and lineament system were gathered in a GIS environment. Each criterion was assigned a weight value by applying the Pairwise Comparison Method and the Analytical Hierarchy Method. In order to choose the best alternative, the Technique for Order Preference by Similarity to the Ideal Solution, which is regarded as an ideal point method, was applied and a landfill site was selected. The geotechnical properties of the so-called “Ankara clay” that shows widespread distribution in Ankara were reviewed and assessed for its suitability as a compacted clay liner.     

Hydrochemical,isotopic, and reservoir characterization of the Pasinler (Erzurum) geothermal field,eastern Turkey

The reservoir temperature and conceptual model of the Pasinler geothermal area, which is one of the most important geothermal areas in Eastern Anatolia, are determined by considering its hydrogeochemical and isotope properties. The geothermal waters have a temperature of 51 °C in the geothermal wells and are of Na–Cl–HCO₃ type. The isotope contents of geothermal waters indicate that they are of meteoric origin and that they recharge on higher elevations than cold waters. The geothermal waters are of immature water class and their reservoir temperatures are calculated as 122–155 °C, and their cold water mixture rate is calculated as 32%. According to the δ¹³C_VPDB values, the carbon in the geothermal waters originated from the dissolved carbon in the groundwaters and mantle-based CO₂ gases. According to the δ³⁴S_CDT values, the sources of sulfur in the geothermal waters are volcanic sulfur, oil and coal, and limestones. The sources of the major ions (Na⁺, Ca²⁺, Mg²⁺, Cl^?, and HCO₃ ^?) in the geothermal waters are ion exchange and plagioclase and silicate weathering. It is determined that the volcanic rocks in the area have effects on the water chemistry and elements like Zn, Rb, Sr, and Ba originated from the rhyolite, rhyolitic tuff, and basalts. The rare earth element (REE) content of the geothermal waters is low, and according to the normalized REE diagrams, the light REE are getting depleted and heavy REE are getting enriched. The positive Eu and negative Ce anomalies of waters indicate oxygen-rich environments.     

Review of water and soil contamination in and around Salihli geothermal field (Manisa,Turkey)

The town of Salihli is situated in Gediz Graben in the western Anatolia. This region is important in terms of industry, mining, geothermal energy, water sources, and agricultural production. Geothermal flow and anthropogenic activities in Salihli threaten the surrounding environment due to the contamination of cold groundwater, surface water, and soil. The goal of the present study is to determine the environmental effects of the geothermal and anthropogenic activities in Salihli on soil, stream sediments, and water. Stream sediments and farm soil have been contaminated by substances derived from geothermal and industrial effluents. To this end, the quality review of the water was completed and the heavy metal levels in stream sediment samples were measured to determine the extent of contamination. The elements As, B, Br, Fe, and Ni are the major contaminants present in surface water and groundwater in the study area. The concentrations of these elements excess tolerance limits of international water standards. Gibbsite, K-mica, kaolinite, sepiolite, halite, sulfur, willemite, and Pb(OH)₂ might be precipitated as scales at low temperatures on the soil; this could be interpreted as a resultant from soil contamination. The concentrations of 17 elements (As, Ba, B, Cd, Co, Cr, Cu, Fe, Hg, Li, Mo, Mn, Ni, Pb, Sb, Sr, and Zn) were measured in samples from stream sediments and surface soils. In the study area, especially geothermal and anthropogenic activities give rise to environmental pollution.     

Geotechnical characterization and facies change detection of the Bogacay coastal plain (Antalya,Turkey) soils

The Bogacay Plain is well known tourist site in Turkey, which is famous for its wide beaches. However, almost 60% of the area is now occupied by buildings, and some of the high-rise buildings suffer from foundation settlement and tilting. Soils of the plain are of lagoonal origin; all of the facies which are typical of the lagoonal environment are present in the geological profile. Because of variation in grain size and development of a weathered crust, the fine-grained soils of the central-lagoon environment are highly variable with regard to their engineering properties. The compression indices of clays range from 0.25 to 0.55 and correlate relatively well with initial void ratio, liquid limit, and moisture content. Over consolidation ratio varies between 1.4 and 10 and decreases from the surface down to the base of the weathered-crust zone. The undrained shear strength of clays decreases with depth for the first 6 m; this behaviour is because of apparent overconsolidation in the weathered-crust zone. Sedimentary facies and their boundaries can be detected using CPT data; moreover, for profiling and facies-boundary detection, SPT and seismic sounding are not as effective as CPT.     

Geochemical characterization of the Biga Peninsula thermal waters (NW Turkey)

Thermal water chemistry from the Biga Peninsula (NW Turkey) was investigated in order to discriminate among hydrochemical facies, and isotopic groups and identify the major geochemical processes. A systematic hydrogeochemical survey was carried out, incorporating new data as well as results from the previous studies. Results were used to further develop hydrogeological and geochemical models. Thermal water compositions were classified into four groups and the processes affecting evolution of water compositions were interpreted. Types 1, 2 and 3 are representatives of water corresponding to sulfate dominant fluids (mainly NaSO₄-type), chloride dominant fluids (mainly NaCl-type), and bicarbonate dominant fluids (Na- or CaHCO₃-type), respectively. Group 4 comprises the fluids with compositions that are not dominated by any distinctive anion. Groundwater infiltrates and circulates through the marbles of the Paleozoic basement. The isotopic composition of thermal waters revealed that deep infiltration of meteoric water took place in periods of changed climatic conditions.     

GIS-based evaluation of groundwater quality and estimation of soil salinization and land degradation risks in an arid Mediterranean site (SW Tunisia)

Arabian Journal of Geosciences - The present work is concerned with the valorization of clay minerals of the Aleg formation (Coniacian-middle Campanian) in the clinker manufacturing. The studied...     

GIS-based landslide susceptibility for Arsin-Yomra (Trabzon,North Turkey) region

The purpose of this study is to assess the susceptibility of landslides around Yomra and Arsin towns near Trabzon, in northeast of Turkey, using a geographical information system (GIS). Landslide inventory of the area was made by detailed field surveys and the analyses of the topographical map. The landslide triggering factors are considered to be slope angle, slope aspect, distance from drainage, distance from roads and the weathered lithological units, which were called as “geotechnical units” in the study. Idrisi and ArcGIS packages manipulated all the collected data. Logistic regression (LR) and weighted linear combination (WLC) statistical methods were used to create a landslide susceptibility map for the study area. The results were assessed within the scope of two different points: (a) effectiveness of the methods used and (b) effectiveness of the environmental casual parameters influencing the landslides. The results showed that the WLC model is more suitable than the LR model. Regarding the casual parameters, geotechnical units and slopes were found to be the most important variables for estimating the landslide susceptibility in the study area.     

MSW landfill site selection by combining AHP with GIS for Konya,Turkey

Landfill site selection is a critical issue in the urban planning process because of its enormous impact on the economy, ecology, and the environmental health of the region. Landfill site selection process aims to locate the areas that will minimize hazards to the environment and public health. Multi-criteria evaluation methods are often used for different site selection studies. The purpose of this study was to determine suitable landfill site selection by using the geographical information system and the analytic hierarchy process in the study area. The final index model was grouped into four categories as “low suitable”, “moderate”, “suitable” and “best suitable” with an equal interval classification method. As a result, 12.69 % of the study area was low suitable, 7.27 % was moderately suitable, 13.79 % was suitable, and 15.52 % was the best suitable for landfilling; 50.72 % of the study area is not suitable for a landfilling.     

微型桩加固土质边坡的动土压力响应及其频谱特性研究

通过大型振动台试验,对滑面附近位置处的动土压力峰值分布规律进行了分析。由于地震信号具有持时短、非平稳性等特点,为分析其在不同频带的动力响应情况,利用小波包分析频带划分均匀能力和时频局部化性质,对水平向加载的El波进行了分解,从而对其频谱特性进行了研究。试验结果表明:滑面附近位置处动土压力常常最大,且动土压力在沿桩身高度25 cm及45 cm处均出现了突变,在实际工程中应重点关注这两个位置;对微型桩动土压力影响较大的频段主要为第一频带(0.1～6.26Hz)和第二频带(6.26～12.51Hz),在工程应用中应避免这两个频带的地震波与微型桩发生共振;沿桩身高度25 cm处,后排微型桩山侧及河侧的动土压力值均要大于前排微型桩山侧及河侧的动土压力值;而在沿桩身高度45 cm处,前排微型桩山侧及河侧的动土压力值均要大于后排微型桩山侧及河侧的动土压力值。     

土钉支护边坡动力模型的建立及地震响应分析

参照上部结构抗震设计的方法,对土钉支护边坡的抗震设计提出了3个水准的抗震设防要求和两阶段设计法。综合考虑输入地震波的特性、边坡土体特性、坡高因素,以及土体边坡在水平地震激励下,其位移响应主要为剪切型变形,建立了土钉支护边坡地震动力简化模型。该模型将同一水平层不稳定土体、稳定土体在水平地震作用下运动趋势假想为同步,两者之间相互作用很小,因此,取不稳定土体和面板为研究对象。由于面板很柔,其运动随着土体的运动而变化,其刚度只考虑剪切刚度,将土钉处理成弹性支座,建立了土钉支护边坡振动方程,求解了在简谐地震作用下土钉支护边坡动力响应的解析解,通过该模型可以得到滑移面附近土钉轴力动力响应和土钉支护边坡的弹性动位移响应。最后,结合案例进行了分析,比较了按此分析方法与用ADINA按弹性有限元方法计算的结果,两者吻合较好。故这种方法可用于土钉支护边坡的第1阶段的抗震分析与设计。     

移动荷载作用下层状饱和土的动力响应

根据Biot波动理论,采用传递、反射矩阵（TRM）方法研究了移动荷载作用下层状饱和土动力响应问题。由快速Fourier逆变换法（IFFT）得到层状土地基位移、应力及孔压在时间-空间域内的数值解。计算结果与已有文献结果相吻合,验证了算法的正确性。通过算例分析表明：移动荷载作用下含有软弱夹层的层状土体比均质土具有更显著的动力响应,同时会引起土体孔隙水压升高、土体波动性增强;硬夹层时情况则相反。