The Manyas fault zone (southern Marmara region,NW Turkey): active tectonics and paleoseismology

The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.     

Dynamic buckling of braces in concentrically braced frames

Axially loaded members might experience compressive forces above their static buckling capacity because of dynamic buckling under rapid shortening. Although the subject is studied in the context of engineering mechanics, it has not been thoroughly investigated in the field of earthquake engineering. Such dynamic overshoots in the compressive capacity can also be observed for braces of concentrically braced frames (CBFs) during earthquakes. Consequently, a comprehensive investigation is conducted in this study regarding the effects of dynamic buckling of braces on the seismic behavior of steel CBFs. After providing a theoretical background, recent dynamic experiments on braces and CBFs are simulated and discussed to investigate the occurrence of dynamic overshoot during these tests. Eight archetype CBFs are then designed, modeled, and subjected to a large set of ground motions to provide a quantified insight on the frequency and anticipated level of dynamic overshoot in the compressive capacity of braces during earthquakes. Results of a total of 1600 nonlinear time history analyses revealed that dynamic overshoots occur frequently in braces and affect the behavior of CBFs notably. Considerable increases are recorded in forces transmitted to other members of CBFs as a consequence of such dynamic overshoots. Importance of incorporating these dynamic overshoots in the capacity design procedure of columns, beams, and gusset plates is highlighted. Furthermore, results of a parametric study are presented and summarized in the form of a simple formula that can be used as a guide for estimating the level of dynamic overshoot.     

Eocene I-type magmatism in the Eastern Pontides,NE Turkey: insights into magma genesis and magma-tectonic evolution from whole-rock geochemistry,geochronology and isotope systematics

ABSTRACT

The Eastern Pontides orogenic belt in NE Turkey hosts numerous I-type plutons of Eocene epoch. Here, we report new U–Pb SHRIMP zircon ages and in situ zircon Lu-Hf isotopes along with bulk-rock geochemical and Sr-Nd-Pb-O isotope data from the Kemerlikda??, Ayd?ntepe and Pelitli plutons and mafic microgranular enclaves (MMEs) to constrain their parental melt source(s) and evolutionary processes. U-Pb SHRIMP zircon dating yielded crystallization ages between 45 and 44 Ma for the studied plutons and their MMEs. The plutons range from gabbro to granite and have I-type, medium to high-K calc-alkaline, and metaluminous to slightly peraluminous characteristics. On the primitive mantle-normalized multi-trace-element variations, the plutons and their MMEs are characterized by signi?cant enrichment in LILE/HFSE. Chondrite-normalized REE patterns of the plutons and their MMEs are close to each other and show moderate enrichment with variable negative Eu anomalies. The studied plutons have fairly homogeneous isotope composition (⁸⁷Sr/⁸⁶Sr_(i) = 0.70502 to 0.70560; εNd_(i) = +0.9 to – 1.4; δ¹⁸O = +5.0 to +8.7‰, εHf_(i) = – 2.2 to +13.5). The MMEs show medium to high-K calc-alkaline and metaluminous character. Although the isotope signatures of the MMEs (⁸⁷Sr/⁸⁶Sr_(i) = 0.70508 to 0.70542; εNd_(i) = +0.9 to ?1.1; δ¹⁸O = +5.8 to +8.0, εHf_(i) = +4.3 to +10.4) are very similar to those of the host rocks. Fractionation of plagioclase, amphibole, pyroxene and Fe-Ti oxides played an important role in the evolution of the plutons. The isotopic composition of the studied plutons and MMEs are similar to I-type plutons derived from mantle sources. The MMEs show incomplete magma mixing/mingling, representing small bodies of mafic parental magma. The parental magma(s) of the studied plutons were generated from the enriched lithospheric mantle and then modified by fractional crystallisation, and lesser assimilation and mixing/mingling in the crustal magma chambers.     

Preconcentration by Coprecipitation of Copper and Nickel with Mo(VI)/Triazole Derivative System and Their Determinations by Flame Atomic Absorption Spectrometry in Food and Water Samples

A new separation and preconcentration technique based on coprecipitation of Cu(II) and Ni(II) ions by the aid of Mo(VI)/di‐tert‐butyl{methylenebis[5‐(chlorobenzyl)‐4H‐1,2,4‐triazol‐3,4‐diyl]}biscarbamate (BUMECTAC) precipitate has been established. The Mo(VI)/BUMECTAC precipitate was dissolved by concentrated HNO₃ and the solution was completed to 5.0 mL with distilled/deionized water. The levels of the analyte ions were determined by flame atomic absorption spectrometer. The effects of experimental conditions like HNO₃ concentration, amount of BUMECTAC and Mo(VI), sample volume, etc. and also the influences of some foreign ions were investigated in detail on the quantitative recoveries of analyte ions. The preconcentration factors were found to be 40 for Cu(II) and 100 for Ni(II) ions. The detection limits for Cu(II) and Ni(II) ions based on 3σ (N:10) were 0.43 and 0.70 µg L^?1, respectively. The relative standard deviations were found to be lower than 4.0% for both analyte ions. The accuracy of the method was checked by spiked/recovery tests and the analysis of two certified reference materials (Environment Canada TM‐25.3 and CRM‐SA‐C Sandy Soil C). The procedure was successfully applied to sea water and stream water as liquid samples and baby food as solid sample in order to determine the levels of Cu(II) and Ni(II) ions.     

Preliminary seismic microzonation of Sivas city (Turkey) using microtremor and refraction microtremor (ReMi) measurements

Sivas city, located in the inner east part of Anatolia (Turkey), is far from seismic sources. However, the city is under risk owing to strong earthquakes occurring around the area, and different soil conditions that can produce variation in the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be achieved by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Sivas, based on the variation in the dominant periods of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 114 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with those obtained from refraction microtremor measurements at two profiles crossing the studied area. According to the classification of dominant periods, Sivas area can be divided into four zones, probably prone to different levels of seismic hazard. However, specific studies including analysis of weak earthquakes are required in the future to validate our microzonation map.     

Assessing radial transmissivity variation in heterogeneous aquifers using analytical techniques

Pumping tests are one of the most commonly used in situ testing techniques for assessing aquifer hydraulic properties. Numerous researches have been conducted to predict the effects of aquifer heterogeneity on the groundwater levels during pumping tests. The objectives of the present work were as follows: (1) to predict drawdown conditions and to estimate aquifer properties during pumping tests undertaken in radially symmetric heterogeneous aquifers, and (2) to identify a method for assessing the transmissivity field along the radial coordinate in radially symmetric and fully heterogeneous transmissivity fields. The first objective was achieved by expanding an existing analytical drawdown formulation that was valid for a radially symmetric confined aquifer with two concentric zones around the pumping well to an N concentric zone confined aquifer having a constant transmissivity value within each zone. The formulation was evaluated for aquifers with three and four concentric zones to assess the effects of the transmissivity field on the drawdown conditions. The specific conditions under which aquifer properties could be identified using traditional methods of analysis were also evaluated. The second objective was achieved by implementing the inverse solution algorithm (ISA), which was developed for petroleum reservoirs to groundwater aquifer settings. The results showed that the drawdown values are influenced by a volumetric integral of a weighting function and the transmissivity field within the cone of depression. The weighting function migrates in tandem with the expanding cone of depression. The ability of the ISA to predict radially symmetric and log‐normally distributed transmissivity fields was assessed against analytical and numerical benchmarks. The results of this investigation indicated that the ISA method is a viable technique for evaluating the radial transmissivity variations of heterogeneous aquifer settings. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of particle characteristics on the evolution of particle size,particle morphology,and fabric of sands loaded under uniaxial compression

Acta Geotechnica - This paper presents the results and analyses of uniaxial compression experiments performed on three silica sands. The sands have comparable particle-size distributions, but their...     

Nonsymmetrical loading protocols for shear links in eccentrically braced frames

The AISC Seismic Provisions for Structural Steel Buildings (AISC 341-16) provide a testing protocol for qualification of link-to-column connections in eccentrically braced frames (EBFs). This symmetrical testing protocol was developed by conducting nonlinear time history analysis on representative EBFs designed according to the International Building Code. Although the testing protocol is intended for qualification of link-to-column connections, many research programs have employed this recommended protocol for testing of shear links. Recent numerical investigations on constructed EBFs and archetype models showed that links can be subjected to one-sided loadings with significantly higher link rotation angles than the codified limits. A numerical study has been undertaken to develop nonsymmetrical loading protocols for shear links in EBFs. Pursuant to this goal, 20 EBF archetypes were designed according to the ASCE7-16 standard. The main parameters investigated were the link length to bay width ratio (e/L), number of stories, type of EBF, and the ground motion level. The archetypes were subjected to maximum considered earthquake and collapse level earthquake as recommended by FEMA P695. The results showed that the history of link rotation is single sided and depends strongly on e/L and the level of ground motion. Nonsymmetrical loading protocols that depend on the aforementioned variables were developed and are presented herein.     

Late Triassic rifting and Jurassic–Cretaceous passive margin development of the Southern Neotethys: evidence from the Adıyaman area,SE Turkey

Evidence of rifting and continental break-up to form the S Neotethys is found within the volcanic-sedimentary Koçali Complex. This is a folded, thrust-imbricated succession that includes lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganiferous deposits. Interbedded ribbon cherts contain radiolarians of Late Triassic to Late Jurassic age. The lower part of the succession of Mid?-Late Triassic age (Tarasa Formation) is dominated by enriched mid-ocean ridge basalt (E-MORB). The overlying Late Triassic to Mid-Jurassic interval (Konak Formation) is characterised by intercalations of ocean island basalt and E-MORB. Taking account of structural position, the basalts erupted within the outer part of a continent–ocean transition zone. Continental break-up probably occurred during the Late Triassic (Carnian–Norian). Early to Mid-Jurassic lavas and volcaniclastic sediments record volcanism probably after continental break-up. In addition, the Karadut Complex is a broken formation that is located at a relatively low structural position just above the Arabian foreland. Pelagic carbonates, redeposited carbonates and radiolarites predominate. Radiolarians are dated as Early to Mid-Jurassic and Late Cretaceous in age. The pelagic carbonates include planktic foraminifera of Late Cretaceous age. The Karadut Complex resulted from the accumulation of calcareous gravity flows, pelagic carbonate and radiolarites in a relatively proximal, base-of-slope setting. After continental break-up, MORB and ophiolitic rocks formed within the S Neotethys further north. Tectonic emplacement onto the Arabian platform took place by earliest Maastrichtian time. Regional interpretation is facilitated by comparisons with examples of Triassic rifting and continental break-up in the eastern Mediterranean region and elsewhere.