A study of microearthquake seismicity and focal mechanisms within the Sea of Marmara (NW Turkey) using ocean bottom seismometers (OBSs)

We have carried out seismological observations within the Sea of Marmara (NW Turkey) in order to investigate the seismicity induced after Gölcük–İzmit (Kocaeli) earthquake (M_w 7.4) of August 17, 1999, using ocean bottom seismometers (OBSs). High-resolution hypocenters and focal mechanisms of microearthquakes have been investigated during this Marmara Sea OBS project involving deployment of 10 OBSs within the Çınarcık (eastern Marmara Sea) and Central-Tekirdağ (western Marmara Sea) basins during April–July 2000. Little was known about microearthquake activity and their source mechanisms in the Marmara Sea. We have detected numerous microearthquakes within the main basins of the Sea of Marmara along the imaged strands of the North Anatolian Fault (NAF). We obtained more than 350 well-constrained hypocenters and nine composite focal mechanisms during 70 days of observation. Microseismicity mainly occurred along the Main Marmara Fault (MMF) in the Marmara Sea. There are a few events along the Southern Shelf. Seismic activity along the Main Marmara Fault is quite high, and focal depth distribution was shallower than 20 km along the western part of this fault, and shallower than 15 km along its eastern part. From high-resolution relative relocation studies of some of the microearthquake clusters, we suggest that the western Main Marmara Fault is subvertical and the eastern Main Marmara Fault dips to south at 45°. Composite focal mechanisms show a strike-slip regime on the western Main Marmara Fault and complex faulting (strike-slip and normal faulting) on the eastern Main Marmara Fault.     

Archaean high-K granitoids produced by remelting of earlier Tonalite–Trondhjemite–Granodiorite (TTG) in the Sangmelima region of the Ntem complex of the Congo craton,southern Cameroon

We present a geochemical and isotopic study that, consistent with observed field relations, suggest Sangmelima late Archaean high-K granite was derived by partial melting of older Archaean TTG. The TTG formations are sodic-trondhjemitic, showing calcic and calc-alkalic trends and are metaluminous to peraluminous. High-K granites in contrast show a potassic calc-alkaline affinity that spans the calcic, calc-alkalic, alkali-calcic and alkalic compositions. The two rock groups (TTG and high-K granites) on the other hand are both ferroan and magnesian. They have a similar degree of fractionation for LREE but a different one for HREE. Nd model ages and Sr/Y ratios define Mesoarchaean and slab-mantle derived magma compositions respectively, with Nb and Ti anomalies indicating a subduction setting for the TTG. Major and trace element in addition to Sr and Nd isotopic compositions support field observations that indicate the derivation of the high-K granitic group from the partial melting of the older TTG equivalent at depth. Geochemical characteristics of the high-K granitic group are therefore inherited features from the TTG protolith and cannot be used for determining their tectonic setting. The heat budget required for TTG partial melting is ascribed to the upwelling of the mantle marked by a doleritic event of identical age as the generated high-K granite melts. The cause of this upwelling is related to linear delamination along mega-shear zones in an intracontinental setting.     

Late-Variscan magmatism revisited: new implications from Pb-evaporation zircon ages on the emplacement of redwitzites and granites in NE Bavaria

Pb-evaporation zircon analyses coupled with a detailed cathodoluminescence (CL) study on the complete series of granitoids from the northern Oberpfalz, NE Bavaria, provide new evidence for the commencement and timing of late-Variscan magmatism. All granitoids analysed in this study were dated before by Rb-Sr and/or K-Ar methods. Investigated samples comprise medium-grained, I-type dioritic rocks (redwitzites), I/S-type granites (Leuchtenberg, Marktredwitz (G1), Zainhammer) and S-type granites (Falkenberg, Liebenstein, Mitterteich, Friedenfels, Steinwald, Flossenbürg, Bärnau). The zircon evaporation technique reveals three groups of ²⁰⁷Pb/²⁰⁶Pb ages which are interpreted to represent magmatic crystallisation: (1) ages of 324-321 Ma are found in all analysed redwitzites and in almost all I/S-type granites; (2) the granites of Falkenberg and Liebenstein yield ages of ~315 Ma; (3) ages between 312 and 310 Ma are recorded in the Mitterteich, Friedenfels, Steinwald and Flossenbürg granites. Titanite crystals from different redwitzite bodies yield conventional U-Pb ages of 325-322 Ma, identical to the Pb-evaporation zircon data of these rocks. The S-type granites of groups 2 and 3 contain zircons with relict cores but only a small number of them yield older ages, indicating that some of the cores must have lost their radiogenic Pb. From the geochronological data, we infer that metamorphic conditions of the Variscan crust produced different granite types at different times. The data support a model involving an early period of mantle-related magmatism which postdates the final convergence stage of the Variscan orogen. This magmatic activity was at the same time as the thermal peak of regional metamorphism and is followed by a late period of crustal anatexis, which is probably related to post-collisional extension of the thickened Variscan crust.     

Forward Modeling with Forced Neural Networks for Gravity Anomaly Profıle

In this paper, we introduce a new method called Forced Neural Network (FNN) to find the parameters of the object in geophysical section respect to gravity anomaly assuming the prismatic model. The aim of the geological modeling is to find the shape and location of underground structure, which cause the anomalies, in 2D cross section. At the first stage, we use one neuron to model the system and apply back propagation algorithm to find out the density difference. At the second level, quantization is applied to the density differences and mean square error of the system is computed. This process goes on until the mean square error of the system is small enough. First, we use FNN to two synthetic data, and then the Sivas–Gürün basin map in Turkey is chosen as a real data application. Anomaly values of the cross section, which is taken from the gravity anomaly map of Sivas–Gürün basin, are very close to those obtained from the proposed method.     

Kaledonische,herzynische und alpidische Ereignisse im Mittelostalpin nördlich der westlichen Hohen Tauern,abgeleitet aus petrographischen und geochronologischen Untersuchungen

Zusammenfassung Die Schwazer Augengneise (Kellerjoch-Gneise) und die Steinkogelschiefer wurden petrographisch und geochronologisch untersucht. Die Steinkogelschiefer und die Schwazer Augengneise zeigen eine prograde Metamorphose der Amphibolitfazies. Sie liegen auf den schwächer metamorphen Innsbrucker Quarzphylliten und unter den ebenfalls schwächer metamorphen Gesteinen der Grauwackenzone, nördlich der westlichen Hohen Tauern (Tirol, Salzburg, Österreich). Aufgrund des kombinierten Compston-Jeffery- und Nicolaysen-Diagramms ist das Sedimentationsalter des Eduktes der Steinkogelschiefer 540 Mio. Jahre. Das Alter der Platznahme des Eduktes der Schwazer Augengneise ist wahrscheinlich 425 Mio. Jahre. Eine kaledonische Metamorphose ist nicht nachweisbar.Die herzynische Metamorphose verursachte sowohl in den Schwazer Augengneisen als auch in den Steinkogelschiefern eine vollständige Sr-Homogenisierung im Gesamtgestein. Die Rb-Sr-Isochrone der Schwazer Augengneise ergibt ein Alter von 322±24 Mio. Jahren bei einem Sr⁸⁷/Sr⁸⁶-Isotopenverhältnis von 0.7180±0.0024. Die Rb-Sr-Isochrone der Steinkogelschiefer definiert ein Alter von 347±30 Mio. Jahren, bei einem Sr⁸⁷/Sr⁸⁶-Verhältnis von 0.7150±0.0021. Die herzynischen Phengite aus den Schwazer Augengneisen ergeben mit der Rb-Sr-Methode ein Abkühlungsalter von 273 bzw. 260 Mio. Jahren. Die K-Ar-Phengit- und Muscovitalter sind Mischalter, welche zwischen dem Alter der herzynischen und dem der frühalpinen Metamorphose liegen. Das frühalpine Ereignis wird durch Rb-Sr-Biotitalter um 90 Mio. Jahre erfaßt. Dieses Alter entspricht dem Zeitpunkt der Abkühlung der Gesteine unter 300 °C vor dem frühalpinen Deckenschub.Die K-Ar-Alter der Biotite sind geologisch nicht interpretierbar, da sie Ar-Überschuß zeigen.Die Überlagerung der Innsbrucker Quarzphyllite durch die Steinkogelschiefer und die Schwazer Augengneise ist wahrscheinlich das Ergebnis eines herzynischen Deckenbaus. Die Steinkogelschiefer und die Schwazer Augengneise könnten daher nicht zur mittelostalpinen Deckeneinheit gehören, sondern tektonisch gesehen, Teil des unterlagernden unterostalpinen Innsbrucker Quarzphyllites sein.

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Petrology and geochronology of the Schwazer Augengneis (Kellerjochgneis) and of the Steinkogelschiefer north of the western Tauern Window have been investigated. The Steinkogelschiefer are garnet-mica schists, the Schwazer Augengneis is an orthoaugengneiss. Both rock units show a prograde metamorphism of the amphibolite facies and are interbedded between the Innsbrucker Quarzphyllite and the Grauwackenzone. The Innsbrucker Quarzphyllite and the rocks of the Grauwackenzone clearly show in respect to the Schwazer Augengneis and the rocks of the Steinkogelschiefer unit a lower metamorphic grade of the greenschist facies. From combined Compston-Jeffery- and Nicolaysen-diagrams the age of the sediments from which the mica schists of the Steinkogelschiefer unit derives is 540 m. y. The age of the intrusion of the magma from which the Schwazer orthoaugengneis later originated is probably 425 m. y. A Caledonian metamorphism could not be demonstrated by radiometry. In the Schwazer Augengneis as well as in the paragneisses of the Steinkogelschiefer unit a complete Sr-homogenisation was produced by the hercynian metamorphism. An age of 322±24 m. y. and a Sr⁸⁷/Sr⁸⁶-ratio of 0.7180±0.0024 result from a Rb-Sr-Isochrone of the Schwazer Augengneis. The RbSr-Isochrone of the Steinkogelschiefer defines an age of 347±30 m. y. and a Sr⁸⁷/Sr⁸⁶-ratio of 0.7150±0.0021. From the Rb-Sr-method a cooling age of 273 and 260 m. y. is established for the phengites from the Schwazer Augengneis.K-Ar-ages of the muscovites and of the phengites are mixed ages between the hercynian and that of the eoalpine metamorphism. The eoalpine metamorphism is dated by the Rb-Sr-age of the biotites (90 m. y.). This age corresponds to the cooling of the rocks below a temperature of 300 °C before the eoalpine nappe transport.K-Ar-ages of the biotites show excess argon and are therefore from a geological point of view meaningless. From petrological and geochronological data it cannot be demonstrated that the tectonic position of the Schwazer Augengneis and of the Steinkogelschiefer unit on the top of the Innsbrucker Quarzphyllit and under the Grauwackenzone is due to the alpine nappe transport.From a tectonic point of view, the Steinkogelschiefer and the Schwazer Augengneis therefore probably belongs to the middle austroalpine unit of the Innsbrucker Quarzphyllit.

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Résumé Les gneiss oeillés de Schwaz (Kellerjochgneise) et les schistes de Steinkogel ont été étudiés par voie pétrographique et géochronologique.Tous deux montrent une métamorphose progradée du facies amphibolite. Ils reposent sur la série moins métamorphique des »Innsbrucker Quarzphyllit« et sous la Zone des grauwackes, également peu métamorphiques, au nord des »Hohe Tauern« occidentales Tyrol, Salzbourg, Autriche).Selon le diagramme combiné Compston-Jeffery et Nicolaysen l'âge de la sédimentation des schistes de Steinkogel est de 540 Mio. ans. L'âge de la sédimentation des gneiss oeillés de Schwaz est probablement 425 Mio. ans. Un métamorphisme calédonien ne peut être démontré.Le métamorphisme hercynien a causé — tant dans les gneiss oeillés de Schwaz que dans les schistes de Steinkogel — une homogénisation complète du Sic. L'isochrone RB/Sr des gneiss oeillés de Schwaz indique une âge de 322±24 Mio. ans et un rapport Sr⁸⁷/Sr⁸⁶ de 0.7180±0.0024.L'isochrone Rb/Sr des schistes de Steinkogel indique un âge de 347±30 Mio. et un rapport Sr⁸⁷/Sr⁸⁶ de 0.7150±0.0021. Les phengites hercyniennes dans les gneiss oeillés de Schwaz indiquent, selon la méthode Rb/Sr, un âge de refroidissement de 273 et 260 Mio. ans. Les âges K/Ar de la phengite et la muscovite sont des âges mixtes compris entre celui du métamorphisme hercynien et celui du métamorphisme évalpin.L'éveénement éoalpin est évalué à 90 Mio. ans (Rb/Sr-biotite). Cet âge correspond au moment du refroidissement des roches en-dessous de 300 °C avant al poussée des premières nappes alpines.Les âges K-Ar des biotites ne peuvent pas être interpretés géologiquement étant donné pu'ils montrent un excès d'Ar.Le recouvrement de l'»Innsbrucker Quarzphyllit« par les schistes de Steinkogel et les gneiss oeillés de Schwaz est probablement le résultat d'une tectonique hercynienne. Il en résulte que les schistes de Steinkogel et les gneiss oeillés de Schwaz ne pourraient pas faire partie de l'ensemble de la nappe austroalpine moyenne, mais vus tectoniquement, être une partie de la nappe austroalpine inférieure sous-jacente de l'»Innsbrucker Quarzphyllit«.

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(Kellerjoch-Gneise) Steinkogel. . - — , (, , ). Comston-Jeffery Nicolaysen'a , SteinKogel'a, 540 . , , , , 425 . . . - 322±24 Sr⁸⁷/Sr^8b 0,7180±0,0024. Steinkogel'a 347±30 0,7150± 0,0021. - 273–260 . , -, - . , -, - 90 . 300° , - . , . . . - Steinkogel'a , , . - , , , -- .

     

Rb-Sr- und K-Ar-Altersbestimmungen an Gesteinen und Mineralien des südlichen Ötztalkristallins und der westlichen Hohen Tauern

Zusammenfassung Mehr als 150 Rb-Sr- und K-Ar-Altersbestimmungen wurden an verschiedenen Gesteinstypen und Mineralien aus dem Schneeberger-Zug (Monteneve) sowie dem südlich anschließenden Ostalpinen Altkristallin und aus den westlichen Hohen Tauern durchgeführt.Die ältesten Gesteine im Ötztalkristallin sind die einförmigen Paragesteinsserien des Ostalpinen Altkristallins. Die charakteristischen Einschaltungen in diesen Gesteinen sind langgestreckte,s-parallel eingeschaltete Orthogneise, die einen Isochronenalterswert von 436±17 Mill. Jahren ergaben, bei einem initialen Sr⁸⁷/Sr⁸⁶-Verhältnis von 0,7102±0,0014. Um die Bedeutung dieses Isochronenalterswertes zu klären, wurde ein kombiniertesCompston-Jeffery- undNicolaysen-Diagramm verwendet. Daraus ergibt sich, daß die Schmelzbildung dieser granitischen Gesteine im Ötztalkristallin kaum älter als 450 Mill. Jahre sein kann.Die Auswirkung der variszischen Metamorphose südlich des westlichen Tauernfensters ist an den Mineralien eines pegmatitischen Orthogneises mit dem Rb-Sr-Isochronenalterswert von 299±12 Mill. Jahren ersichtlich. Die Isochrone ergibt ein initiales Sr⁸⁷/Sr⁸⁶-Verhältnis von 0,9657±0,014.Das alpine Geschehen beginnt mit der frühalpinen Metamorphose in weiten Teilen des Ostalpinen Altkristallins. Die Rb-Sr-Hellglimmeralter um 120-110 Mill. Jahre weisen vermutlich auf die mögliche Bildungszeit der Hellglimmer bzw. der frühalpinen Mineralparagenesen im Bereich des Schneeberger-Zuges (Monteneve) und seiner unmittelbaren Umgebung hin. Dagegen fallen die K-Ar-Abkühlalterswerte an Hellglimmern in das Zeitintervall von 90-77 Mill. Jahren, gleichgültig ob Phengite oder Muskovite untersucht wurden. Die Rb-Sr- und K-Ar-Biotitabkühlalter von 80-74 Mill. Jahren weisen auf eine weitspannige, schnelle Abkühlung eventuell im Zusammenhang mit einer Überschiebung hin. Die frühalpine Aufwärmung fehlt nur im Südteil des Altkristallins südlich der westlichen Hohen Tauern.Das jüngste Ereignis im untersuchten Gebiet ist aus dem Bereich des Tauernwestendes durch die Rb-Sr- und K-Ar-Hellglimmeralter von 36-25 Mill. Jahren gegeben. Die Rb-Sr-Phengitalter von rund 30 Mill. Jahren sowie die gleichalten K-Ar-Hellglimmeralter aus dem schwächst temperierten Bereich des Tauernfensters stellen vermutlich Bildungsalter nahe des thermischen Höhepunktes dar. Am Tauernwestende weisen die wenig streuenden Biotitalter darauf hin, daß die Abkühlung auf etwa 300° C durch eine gleichförmige, blockartige Hebung relativ rasch erfolgte.

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More than 150 Rb-Sr and K-Ar age determinations were made on different types of rocks and minerals from the Schneeberger-Zug (Monteneve) and the south lying Eastalpine Altkristallin, as well as from rocks of the western end of the Hohen Tauern.The oldest rocks from the Oetztalkristallin are the monotonous paragneisses of the Eastalpine Altkristallin. Intercalated ands-parallel within these rocks are orthogneisses. They yield an isochron age of 436±17 m. y., with an initial of 0.7102±0.0014. The combination of aCompston-Jeffery with aNicolaysen-diagram shows, that the magmatic stage of these rocks could hardly be older than 450 m. y.A pegmatitic orthogneiss with an Rb-Sr-mineralisochron age of 299±12 m. y. and an initial of 0.9657±0.0140 shows the influence of the Hercynian metamorphic event in the South of the western end of the Hohen Tauern.The alpine orogeny starts with Eo-alpine metamorphism in widespread parts of the Eastalpine Altkristallin. Rb-Sr ages (120-110 m. y.) on white micas probably point to the time of the formation of the white micas as well as to the formation of the Eoalpine mineral-parageneses in the region of the Schneeberger-Zug (Monteneve) and its very near surroundings. The K-Ar cooling ages are in the range of 90 to 77 m. y. for muscovites and phengites. The cooling ages on biotites (Rb-Sr and K-Ar) in the range of 80 to 74 m. y. point to widespread, rapid cooling presumably in connection with an overthrust. The Eo-alpine thermal event is missing only in the southern part of the Altkristallin to the South of the western Hohen Tauern.The youngest event in the area of discussion is given by the white mica-ages (Rb-Sr and K-Ar) of 36 to 25 m. y. found in the region of the Western end of the Hohen Tauern. The Rb-Sr phengite-ages of around 30 m. y., as well as the K-Ar white mica-ages of the same age from the thermally least affected area of the Tauern-window, can probably be interpreted as formation-ages near the thermal climax. The biotite-ages at the Western end of the Hohen Tauern have a very small spread and this points to a relatively quick cooling due to blocklike uplift of the whole region.

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Résumé Plus de 150 déterminations d'âge par Rb-Sr et K-Ar ont été faites sur différentes espèces de roches et minéraux du «Schneeberger Zug» (Monteneve) et de sa continuation vers le sud: le cristallin austroalpin ainsi que du «Hohen Tauern» à l'ouest.Les plus vieilles roches du cristallin d'Oetztal sont les séries monotones des roches de caractère «para» du cristallin austroalpin. Les intercalations typiques dans ces roches sont des orthogneiss allonges ets-parallèles qui montrent un âge d'isochrone de 436±17 millions d'années avec un rapport initial de Sr⁸⁷/Sr⁸⁶ de 0,7102±0,0014.Afin de déterminer la signification de cet âge d'isochrone on utilisa un diagramme combiné deCompston-Jeffery etNicolaysen. Il en résulte que l'âge magmatique de ces roches granitiques dans le cristallin d'Oetztal ne peut pas être plus vieux que 450 millions d'années.L'influence de la métamorphose hercynienne au sud du «westliches Tauernfenster» est bien visible dans les minéraux d'un orthogneiss pegmatitique avec un âge d'isochrone de Rb-Sr de 299 ± 12 millions d'années. L'isochrone donne un rapport initial du sr⁸⁷/Sr⁸⁶ de 0,9657±0,014.L'événement alpin commence avec la métamorphose alpine initiale dans de vastes parties du cristallin austroalpin. Les âges Rb-Sr des micas blancs de 120-110 millions d'années pourraient indiquer le temps de formation possible des micas blancs respectivement des paragenèses des minéraux jeunes-alpins dans la région du «Schneeberger-Zug» (Monteneve) et ses environs directs.Par contre les dates K-Ar de refroidissement des micas blancs tombent dans l'intervalle de 90 à 77 millions d'années, indifféremment si on examine des Phengites ou Muscovites. Les âges Rb-Sr et K-Ar de refroidissement des biotites de 80 à 74 millions d'années indiquent un refroidissement étendu et rapide, peut-être en relation avec un chevauchement. L'échauffement jeune-alpin ne manque qu'au sud du vieux cristallin, situé au sud des «Hohen Tauern» occidentales.L'événement le plus jeune dans le domaine examiné se trouve dans la région du «Tauernwestende» avec un âge Rb-Sr et K-Ar des micas blancs de 36 à 25 millions d'années. L'âge Rb-Sr des Phengites de 30 millions d'années ainsi que les mêmes âges K-Ar des micas blancs de la région du «Tauernfenster» la moindre temperée, indiquent un âge de formation vraisemblablement proche du maximum thermique.Dans la région du «Tauernwestende» les âges des biotites ne différent pas beaucoup; cela nous indique que le refroidissement à 300° C s'effectua rapidement par une élévation en bloc et monotone.

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150 Rb/Sr K/Ar -, , - . , - . , S- , 436±17 , 0,7102 ±0,0014. , Compston-Jeffery, , - 450 . , Rb/Sr 299±12 . Sr⁸⁷/Sr⁸⁶ 0,9657±0,014. - . — Rb/Sr 120– 110 — , -, , . — — 90 77 , , - . , Rb/Sr K/Ar, 80–74 , , , , . .

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Erweiterte Fassung eines am 22. und 23. März 1975 im Rahmen des Schwerpunktprogramms der DFG auf dem Internationalen Symposium zur Geodynamik der Ostalpen in Salzburg gehaltenen Vortrages.     

Plutonism in the Variscan Odenwald (Germany): from subduction to collision

 Latest Devonian to early Carboniferous plutonic rocks from the Odenwald accretionary complex reflect the transition from a subduction to a collisional setting. For ∼362 Ma old gabbroic rocks from the northern tectonometamorphic unit I, initial isotopic compositions (ε_Nd=+3.4 to +3.8;⁸⁷Sr/⁸⁶Sr =0.7035–0.7053;δ¹⁸O=6.8–8.0‰) and chemical signatures (e.g., low Nb/Th, Nb/U, Ce/Pb, Th/U, Rb/Cs) indicate a subduction-related origin by partial melting of a shallow depleted mantle source metasomatized by water-rich, large ion lithophile element-loaded fluids. In the central (unit II) and southern (unit III) Odenwald, syncollisional mafic to felsic granitoids were emplaced in a transtensional setting at approximately 340–335 Ma B.P. Unit II comprises a mafic and a felsic suite that are genetically unrelated. Both suites are intermediate between the medium-K and high-K series and have similar initial Nd and Sr signatures (ε_Nd=0.0 to –2.5;⁸⁷Sr/⁸⁶Sr=0.7044–0.7056) but different oxygen isotopic compositions (δ¹⁸O=7.3–8.7‰ in mafic vs 9.3–9.5‰ in felsic rocks). These characteristics, in conjunction with the chemical signatures, suggest an enriched mantle source for the mafic magmas and a shallow metaluminous crustal source for the felsic magmas. Younger intrusives of unit II have higher Sr/Y, Zr/Y, and Tb/Yb ratios suggesting magma segregation at greater depths. Mafic high-K to shoshonitic intrusives of the southern unit III have initial isotopic compositions (ε_Nd=–1.1 to –1.8;⁸⁷Sr/⁸⁶Sr =0.7054–0.7062;δ¹⁸O=7.2–7.6‰) and chemical characteristics (e.g., high Sr/Y, Zr/Y, Tb/Yb) that are strongly indicative of a deep-seated enriched mantle source. Spatially associated felsic high-K to shoshonitic rocks of unit III may be derived by dehydration melting of garnet-rich metaluminous crustal source rocks or may represent hybrid magmas. Received: 7 December 1998 / Accepted: 27 April 1999     

A rapid seismic safety assessment method for mid-rise reinforced concrete buildings

The majority of existing buildings are not safe against earthquakes in most of the developing countries. Existing building stocks should be assessed with a seismic safety assessment method before a devastating earthquake. Cheaper and quicker rapid seismic safety assessment methods can be used instead of code-based assessment methods to determine the seismic performance of existing buildings. In this study, an approach was introduced to determine the seismic performance of existing mid-rise reinforced concrete buildings with fewer parameters and process steps than code-based detailed assessment procedures. Calibration and regulation of the introduced method were conducted on the 39 collapsed buildings’ projects in 1999 Kocaeli, Turkey, earthquake. Finally, 55 existing buildings located in Eskisehir, Turkey, assessed with this calibrated method and the results were compared with the results of a code-based detailed assessment method; the results showed a very good agreement of about 83%. This study shows that the proposed method can be applied for the determination of the seismic performance of existing mid-rise reinforced concrete buildings quickly and without compromising reliability.     

Sea level variability at Antalya and Mente? tide gauges in Turkey: atmospheric, steric and land motion contributions

Sea level trends and interannual variability at Antalya and Menteş tide gauges are investigated during the 1985–2001 period, quantifying the roles of atmospheric, steric and local land motion contributions. Tide gauge sea level measurements, temperature/salinity climatologies and GPS data are used in the analyses and the results are compared with the output of a barotropic model forced by atmospheric pressure and wind. The overall sea level trends at two tide gauges collocated with GPS are in the range of 5.5 to 7.9 mm/yr during the study period, but showing different behaviour in the sub-periods 1985–1993 and 1993–2001 due to variations in the contributing factors both in space and time. After the removal of the atmospheric forcing and steric contribution from sea level records, the resulting trends vary between 1.9 to 4.5 mm/yr in Antalya and −1.2 to −11.6 mm/yr in Menteş depending on the period considered. Vertical land movement estimated from GPS data seems to explain the high positive residual trend in Antalya during the whole period. On the other hand, the source of the highly negative sea level trend of about −14 mm/yr in Menteş during 1985–1993 could not be resolved with the available datasets. Interannual variability of wind and atmospheric pressure appear to dominate the sea level at both tide gauges during the study period. Atmospheric and steric contributions together account for ∼50% of the total sea level variance at interannual time scales. Mass induced sea level variations which were not considered in this study may help to close the sea level trend budgets as well as to better explain the interannual sea level variance.