Diverse tectonic settings of formation of the metaigneous rocks in the Jurassic metamorphic accretionary complexes (Refahiye,NE Turkey) and their geodynamic implications

Two isolated metamorphic accretionary complexes of Jurassic age, the Refahiye and Kurtlutepe metamorphic rocks, crop out as tectonic slices within the coeval suprasubduction-zone ophiolite at the southern margin of the Eastern Pontides (NE Turkey), close to the ?zmir-Ankara-Erzincan suture. The Refahiye metamorphic rocks are made up of greenschist, marble, serpentinite, phyllite and minor garnet amphibolite, garnet micaschist and metachert. The whole unit was metamorphosed under garnet-amphibolite-facies conditions and strongly retrogressed during exhumation. The Kurtlutepe metamorphic rocks consist of subgreenschist-facies metavolcanics, metavolcaniclastics, marble, calc-phyllite, and minor serpentinite and metachert. Metabasites in the Refahiye metamorphic rocks are represented by four distinct geochemical affinities: (i) cumulate “flavor,” (ii) alkaline oceanic island basalt (OIB), (iii) enriched mid-ocean ridge basalt (E-MORB) and (iv) tholeiitic island arc basalt (IAB). On the other hand, the Kurtlutepe metavolcanic rocks display only tholeiitic to calc-alkaline island arc geochemical affinities. The metabasic rocks with OIB affinities were interpreted as parts of the accreted oceanic islands, and those with E-MORB affinities as parts of accreted ridge segments close to oceanic islands and/or plume-distal mid-ocean ridges with a mantle previously metasomatized by plume components. The metabasic rocks with IAB affinities might have been derived from the overlying suprasubduction ophiolite and/or arc domain by a number of tectonic or sedimentary processes including tectonic slicing of accretionary complex and overlying fore-arc ophiolite, juxtaposition of the magmatic arc with subduction zone by strike slip faults, submarine gravity sliding and debris flows or subduction erosion. However, totally recrystallized nature of the metabasic rocks together with field relations does not allow any inference on the processes involved. The Kurtlutepe metavolcanic rocks might represent collided and accreted oceanic island arc with the subduction zone. Attempted subduction of an intraoceanic island arc may also explain the magmatic lull during Late Jurassic–Early Cretaceous in the Eastern Pontides.     

Geochemistry of mafic rocks of the Karakaya complex,Turkey: evidence for plume-involvement in the Palaeotethyan extensional regime during the Middle and Late Triassic

The Karakaya Complex within the Early Mesozoic Cimmerian Orogeny in northern Turkey represents the remnants of the Palaeotethys. It includes slivers and/or mega-blocks of slightly metamorphic basic volcanic rocks associated with fossiliferous sediments as well as hypabyssal and intrusive rocks with basaltic-andesitic to ultramafic compositions. They display two distinct compositional groups; namely alkaline and variably tholeiitic. The alkaline basalt samples are more akin to oceanic-island basalts (OIB) with relatively enriched trace element characteristics together with strong partitioning in HREE ([La/Yb]_N = 5.8–16.2), suggesting that garnet is present as a residual phase in the source of those basalts. The variably tholeiitic samples apart from diabases display E-MORB characteristics; being relatively depleted compared to the alkaline counterparts and less fractionated REE patterns ([La/Yb]_N = 2.1–3.6). The diabases, on the other hand, are distinctively different with a significant negative Nb anomaly (Zr/Nb = 28.9–43.4) and flat REE patterns ([La/Yb]_N = 0.8–1.4), suggesting their generation above a supra-subduction zone, probably a back-arc basin. These results may suggest that a mantle plume-related magmatism associated with extensional oceanic system should have been installed within Palaeotethys during Middle-Late Triassic time, which was then incorporated into subduction–accretion prism forming the final picture, that is, “the Karakaya Complex”.     

Spatial and temporal variations in rainfall characteristics in mountainous and lowland areas in Taiwan

Although changes in rainfall characteristics have been noted across the world, few studies have reported those in mountainous areas. This study was undertaken to clarify spatial and temporal variations in rainfall characteristics such as annual rainfall amount (Pr), mean daily rainfall intensity (η), and ratio of rain days (λ) in mountainous and lowland areas in Taiwan. To this aim, we examined spatial and year‐to‐year variations and marginal long‐term trends in Pr, η, and λ, based on rainfall data from 120 stations during the period 1978–2008. The period mean rainfall () at the lowland stations had strong relationships with the period mean daily rainfall intensity () and the period mean ratio of rain days () during those 31 years. Meanwhile, was only strongly related to at mountainous stations, indicating that influences on spatial variations in were different between lowland and mountainous stations. Year‐to‐year variations in Pr at each station were primarily determined from the variation in η at most stations for both lowland and mountainous stations. Long‐term trend analysis showed that Pr and η increased significantly at 10% and 31% of the total 120 stations, respectively, and λ decreased significantly at 6% of the total. The increases in Pr were mostly accompanied by increases in η. Although stations with significant η increases were slightly biased toward the western lowland area, increases or decreases in Pr and λ were not common. These results contribute to understanding the impacts of possible climate changes on terrestrial hydrological cycles. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessment of potential seismic hazard and site effect in Antakya (Hatay Province), SE Turkey

Antakya city is at risk because of strong earthquakes occurring in the area, and different soil conditions that can produce variation of the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be provided 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 Antakya, based on the variation of the dominant periods and shear velocities of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 69 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with data obtained from refraction microtremor (ReMi) measurements at four profiles crossing the studied area. According to the classification of dominant periods, Antakya city can be divided into five zones, probably prone to different levels of seismic hazard. The shorter natural periods are in inner Antakya and both the sides of Asi River (i.e., northern and southern parts). The eastern and western parts of Antakya have maximum dominant periods. The V _s ³⁰ values were calculated by using the ReMi method along the profiles. Antakya city has V _s ³⁰ values in the range of category C of the national earthquake hazard reduction programme site classification.     

On‐line Solid Phase Extraction of Copper in Water Samples with Flow Injection Flame Atomic Absorption Spectrometry

An on‐line solid phase extraction method for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry has been described. The procedure is based on the retention of Cu(II) ions at pH 6.0 on a minicolumn packed with Amberlite XAD‐1180 resin impregnated with chrome azurol S. After preconcentration, Cu(II) ions adsorbed on the impregnated resin were eluted by 1 mol L^?1 HNO₃ solution. Several parameters, such as pH, type of eluent, flow rates of sample and eluent solutions, amount of resin were evaluated. At optimized conditions, for 3.5 min of preconcentration time, the system achieved a detection limit of 1.0 µg L^?1, and a relative standard deviation of 1.2% at 0.2 µg mL^?1 copper. An enrichment factor of 56‐fold was obtained with respect to the copper determination. The proposed method was successfully validated by the analysis of standard reference material (TMDA 54.4 lake water) and recovery studies. The method was applied to the preconcentration of Cu(II) in natural water samples.     

Multi-disciplinary earthquake researches in Western Turkey: Hints to select sites to study geochemical transients associated to seismicity

Warm and hot spring water as well as soil gas radon release patterns have been monitored in the Aegean Extensional Province of Western Turkey, alongside regional seismic events, providing a multi-disciplinary approach. In the study period of 20 months, seven moderate earthquakes with M _L between 4.0 and 4.7 occurred in this seismically very active region; two earthquakes with magnitude 5.0 also occurred near the study area. Seismic monitoring showed no foreshock activity. By contrast, hydro-geochemical anomalies were found prior to these seismic events, each lasting for weeks. The anomalies occurred foremost in conjunction with dip-slip events and seem to support the dilatancy and water diffusion hypothesis. Increased soil gas radon release was recorded before earthquakes associated with strike-slip faults, but no soil radon anomalies were seen before earthquakes associated with dip-slip faults. Geochemical anomalies were also noticeably absent at some springs throughout the postulated deformation zones of impending earthquakes. The reason for this discrepancy might be due to stress/strain anisotropies.     

Long-term earthquake prediction in western Anatolia with the time- and magnitude-predictable model

Instrumental and historical data on mainshocks for 13 seismogenic sources in western Anatolia have been used to apply a regional time- and magnitude-predictable model. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T _t = 0.13 M _min + 0.21 M _p ? 0.15 log M ₀ + 2.93 and M _f = 0.87 M _min ? 0.06 M _p + 0.33 log M ₀ ? 6.54. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.29, respectively, for the first relation, and 0.65 and 0.47, respectively, for the second relation. The positive dependence of T _t on M _p and the negative dependence of M _f on M _p indicate the validity of time- and magnitude-predictable model on the area considered in this study. On the basis of these relations and using the occurrence time and magnitude of the last main shocks in each seismogenic source, the probabilities of occurrence P(Δt) of the next main shocks during the next 50 years with decade interval as well as the magnitude of the expected main shocks were determined. The highest probabilities P ₁₀ = 80 % (M _f = 6.8 and T _t = 13 years) and P ₁₀ = 32 % (M _f = 7.6 and T _t = 29 years) were estimated for the seismogenic source 11 (Golhisar-Dalaman-Rhodes) for the occurrence of a strong and a large earthquake during the future decade, respectively.     

A Comparative Study of Ozonation,Homogeneous Catalytic Ozonation,and Photocatalytic Ozonation for C.I. Reactive Red 194 Azo Dye Degradation

In this study, the decolorization, dearomatization, and mineralization efficiencies of different advanced oxidation processes (AOPs; namely O₃, O₃/Fe(II), O₃/Fe(II)/UVA, and O₃/TiO₂/UVA) were investigated for the azo dye C.I. Reactive Red 194 (RR194). The effects of pH (3–11), amount of TiO₂ (0.05–1 g/L), and concentration of Fe(II) (0.1–1.6 mM) were investigated for the applied methods. The decolorization and mineralization efficiencies of the photocatalytic ozonation system (O₃/TiO₂/UVA) were increased by decreasing the pH of the dye solution in contrast to the ozonation system (O₃). Decolorization of RR194 was increased in the photocatalytic ozonation system with an increasing amount of catalyst however, a decreasing was occurred for the homogeneous catalytic system (O₃/Fe(II)) when increasing the concentration of catalyst. The decolorization efficiency of the homogeneous catalytic system (O₃/Fe(II)) was enhanced when combined with UVA light. In our study, the most efficient method for dearomatization and mineralization was the O₃/TiO₂/UVA among the applied AOPs.     

Seismic microzonation and earthquake damage scenarios for urban areas

A methodology for seismic microzonation and earthquake damage scenarios may be considered as composed of two stages. In the first stage, microzonation maps with respect to estimated earthquake characteristics on the ground surface are generated for an investigated urban area. The effects of local geological and geotechnical site conditions are taken into account based on site characterization with respect to representative soil profiles extending down to the engineering bedrock. 1D site response analyses are performed to calculate earthquake characteristics on the ground surface using as many as possible, hazard compatible real acceleration time histories. In the second stage, vulnerability of buildings and pipeline systems are estimated based on site-specific ground motion parameters. A pilot study is carried out to evaluate seismic damage in a district in Istanbul, Turkey. The results demonstrate the significance of site characterization and site response analysis in calculating the earthquake characteristics on the ground surface in comparison to simplified empirical procedures.