application of regional frequency analysis to the estimation of extreme storm surges traditionally extreme value theory is applied to single site series of surge observations in order to estimate the probability of occurrence of extreme events at that particular site however single site analyses give uncertain estimation of extreme quantiles mainly because of the limited duration of observation periods in order to reduce this uncertainty regional frequency analysis rfa approaches suggest collecting information not only from a single site series but also from all statistically similar available series of observation the use of rfa is widely increasing in geosciences but few applications have been attempted yet for surge estimation the aim of this study is to examine the applicability of rfa to extreme storm surges the surge data observed at 18 french harbors located on the atlantic coast from the spanish to belgian borders were collected the series span a period of 30 years on average with the longest series going back to the 19th century stationary and independent samples of extreme surges peaks over a given threshold are extracted and their statistical homogeneity has been tested via heterogeneity and discordancy measures based on l moments homogeneous regions have been identified and in order to merge information on frequency of occurrence of surges from all the sites a surge index pooling method is defined finally a regional frequency distribution has been estimated the hypothesis and the applicability of rfa application are discussed with some ideas for future developments in the research direction

extensional tectonics of northwestern macedonia greece since the late miocene tectonic field studies in the florina ptolemais basin northwestern greece were carried out in an attempt to define the regional stress tensors in selected areas affected by neogene and quaternary faulting using recently proposed quantitative methods the analysis allows us to distinguish two extensional phases in the area a late miocene pliocene one with a ne sw average direction of extension and a pleistocene recent one with a nw se direction of extension we conclude that the principal stress axes 2 and 3 were interchanged in passing from one phase to the other these results are reasonably consistent with results of studies carried out in other parts of the aegean area especially the south aegean back arc domain

petrology and evolution of the hercynian pieria granitoid complex thessaly greece paleogeographic and geodynamic implications abstract the upper carboniferous pieria granitoid complex pgc and associated pelagonian basement units are remnants of a hercynian orogenic belt incorporated into the alpine nappe systems of the central hellenides the granitoid rocks range from tonalite to granite and are mildly peraluminous the lack of significant negative eu and sr anomalies suggests insignificant high level crystal fractionation involving plagioclase meta diorite sheets that cut and are deformed with the granitoids are characterized by metamorphic fabrics their trace element signatures are similar to enriched morb and the high ba la is typical of subduction related mafic rocks they are interpreted as representing predominantly asthenosphere derived melts intruded into the granitoids the bimodal mafic felsic association observed in the pgc is also found in other plutonic complexes throughout the flambouron unit of the pelagonian terrane geochemically and isotopically these plutons resemble hercynian plutons of western europe interpreted to result from melting of lower crustal orthogneisses the flambouron unit plutons were situated paleogeographically on the northern margin of gondwana mantle enrichment resulted from short lived subduction during devonian to early carboniferous collision of gondwana and laurasia whereas plutonism occurred during regional extension as gondwana rotated clockwise with respect to laurasia in the late carboniferous

hindcast of the wave conditions along the west iberian coast this paper describes the development of a wave prediction system for the west iberian coast the implemented wave prediction system is based on two state of the art spectral wave models wam for the ocean area and swan for the nearshore however because of its extended geographical space the swan model will include some generation effects in the coarse swan simulations complemented by wave transformation effects near the coast the system was validated by means of extended hindcast runs in various regions belonging to the continental portuguese coastal environment which were compared with buoy data focusing on the extreme energetic events and both direct comparisons and statistical results are presented

teleconnection pattern influence on sea wave climate in the bay of biscay the potential modification of hydrodynamic factors such as waves is a source of concern for many coastal communities because of its potential effect on shoreline evolution in the northern atlantic swell is created by storm winds that cross the atlantic following west east tracks these tracks are shifted more southward or northward depending on the season and on recurring large scale atmospheric pressure anomalies also called teleconnection patterns this study investigates the trends of sea wave patterns in the bay of biscay and relates their interannual variability to teleconnection patterns sea wave parameter time series from the 40 yr european centre for medium range weather forecasts

estimating the upper tail of flood peak frequency distributions using hydrometeorological information in its 1988 report the national research council committee on estimating the probabilities of extreme floods identified principles for improving the estimation of floods with annual exceedance probabilities of the order of 10 3 or smaller this paper presents a methodology for estimating the probability of extreme floods which makes use of these principles its core is the peak to volume method bradley and potter 1992 which is based on separately estimating the probability distributions of flood volumes and flood peaks conditioned on volumes in its original form it relies on extrapolating a conventionally estimated probability distribution the distribution of flood volumes to strengthen this step we propose use of the gradient of extreme values gradex method guillot and duband 1967 in which the upper tail of the flood volume distribution is deduced from that of precipitation we enhance the gradex method by exploiting the work of smith 1989 who developed a regional model for estimating the upper tail of a frequency distribution based on extreme order statistics an example illustrates the proposed method

gondwana derived terranes in the northern hellenides the hellenides constitute an integral part of the alpine orogenic system in southeast europe despite the recognition of several subparallel zones which are interpreted as terranes separated by ophiolitic sutures e g pindos and vardar sutures the classical view of an orogen with a foreland fold and thrust belt a central crystalline zone and a rather undeformed hinterland is still under discussion this paper concentrates on basement terranes of exotic provenance in two of the internal zones of the hellenides that support the interpretation of the hellenides as an accretionary orogen formed by amalgamation of crustal segments during the subduction of tethyan oceanic basins the oldest of these terranes the florina terrane in the pelagonian zone is composed of neoproterozoic arc related orthogneisses two other exotic terranes occur east of the vardar zone within the serbo macedonian massif the pirgadikia terrane is a microterrane in the southern chalkidiki peninsula that consists of panafrican mylonitic orthogneisses with volcanic arc related trace element geochemistry and sr isotopic composition the vertiskos terrane occupies the northwestern part of the serbo macedonian massif and is primarily composed of coarse grained volcanic arc related peraluminous orthogneisses of silurian age these terranes are exotic in relation to the other parts of the hellenides the provenance of the late proterozoic pan african florina and pirgadikia terranes is assumed to be gondwanan whereas the silurian vertiskos terrane may have been part of the so called hun terrane which formed at the northern active continental margin of gondwana in the early paleozoic

formation of homogeneous regions for regional frequency analysis of extreme significant wave heights regional frequency analysis rfa can reduce uncertainties in the estimations of return levels provided that homogeneous regions can be delineated in the framework of extreme marine events a physically based method to form homogeneous regions by identifying typical storms footprints is proposed first a spatiotemporal declustering procedure is employed to detect storms generating marine extremes second the identification of the most typical storms footprints relies on a clustering algorithm based on a criterion of storm propagation the resulting regions are readily explicable sites from a given region are likely to be impacted by the same storms and any storm impacting a region is likely to remain enclosed in this region this procedure is fairly simple to implement as the only information required is the time of occurrence of the observed extremes an application to the estimation of extreme significant wave heights from the numerical sea state database anemoc 2 is given six regions both physically and statistically homogeneous are delineated in the north east part of the atlantic ocean it is shown that the identification of storms footprints allows the increase of the overall statistical homogeneity combined with rfa the proposed method highlights regional differences in the spatial extent and intensity of storms

upper mantle seismic wave attenuation effects of realistic partial melt distribution frequency dependence of seismic velocity and attenuation resulting from viscoelastic relaxation of partially molten mantle is estimated we consider the contribution of the melt squirt mechanism through which pressure differences between disk shaped inclusions are equalized by melt passing through connecting tubes the pressure differences arise as a result of shear strain compressing disk shaped pores differently on the basis of disk orientation with respect to the applied shear the frequencies over which the transition from the unrelaxed to the relaxed states occurs are determined by representing the melt as a network of tubes connecting oblate ellipsoidal pores the pressure equalization process is modeled by a system of first order linear differential equations whose eigenvalues are the characteristic frequencies for melt squirt relaxation it is shown that in this framework the set of frequencies is invariant to the absolute scale of the system but is sensitive to melt bulk modulus and viscosity as well as distribution of melt inside pores and conduits use of realistic solid and melt physical properties and pore and conduit geometries demonstrates that it is the relaxed modulus that is most likely excited in the seismic band and that melt mobility has little effect on seismic attenuation some conceivable melt distributions however would result in detectable attenuation in the seismic band in all cases investigated attenuation increases with frequency indicating that melt squirt is not responsible for global upper mantle q observations

upper mantle seismic wave velocity effects of realistic partial melt geometries we investigate seismic wave velocity reduction resulting from the presence of partial melt in the upper mantle the amount of shear and bulk modulus reduction produced by the presence of a connected network of realistically shaped and naturally organized melt inclusions is found using finite element calculations the geometries of the inclusions are taken directly from laboratory experiments of mantle melting with finite element meshes constructed to conform to these shapes the shear and bulk moduli of the composite material are found for both the unrelaxed isolated inclusions and relaxed pressure equalized inclusions cases by assigning appropriate material properties to the fluid modulus reduction from deformation simulations of a solid containing realistically shaped and ellipse shaped melt inclusions quantify the effect of melt pocket cuspateness and melt pocket organization on seismic velocity reduction the three dimensional response is estimated from two dimensional distributions of the melt phase by determining the mode ii and mode iii components of elastic modulus reduction separately and summing their effects in general cuspate and naturally organized melt inclusions cause greater velocity reduction it is shown that v and vs reduction per percent partial melt are at least 3 6 and 7 9 respectively even higher values for velocity reduction are possible above 1 melt fraction if melt exists only in tubules below 1 melt fraction the lower more conservative values of velocity reduction are 070 greater for vp and 84 greater for vs than the analytically determined values for ellipsoidal inclusions somewhat greater effects are possible if nonrandom organization of melt occurs on scales greater than our model

a high resolution hindcast of wind and waves for the north sea the norwegian sea and the barents sea 1 a combined high resolution atmospheric downscaling and wave hindcast based on the era 40 reanalysis covering the norwegian sea the north sea and the barents sea is presented the period covered is from september 1957 to august 2002 the dynamic atmospheric downscaling is performed as a series of short prognostic runs initialized from a blend of era 40 and the previous prognostic run to preserve the fine scale surface features from the high resolution model while maintaining the large scale synoptic field from era 40 the nested wam wave model hindcast consists of a coarse 50 km model covering the north atlantic forced with era 40 winds and a nested 10 11 km resolution model forced with downscaled winds a comparison against in situ and satellite observations of wind and sea state reveals significant improvement in mean values and upper percentiles of wind vectors and the significant wave height over era 40 improvement is also found in the mean wave period era 40 is biased low in wind speed and significant wave height a bias which is not reproduced by the downscaling the atmospheric downscaling also reproduces polar lows which cannot be resolved by era 40 but the lows are too weak and short lived as the downscaling is not capable of capturing their full life cycle

late carboniferous plutonism within the pre alpine basement of the external hellenides kithira greece evidence from u pb zircon dating in memory of theodor doutsos for his invaluable contribution to the understanding of geology of greece u pb zircon dating of three granitic orthogneisses sampled from kithira island sw greece provide the first reliable evidence for carboniferous plutonism within the pre alpine basement of the external hellenides concordant zircons from two samples yielded ages at 324 2 ma and 323 3 ma whereas the third sample yielded a lower intercept age at 320 1 2 ma the concordant ages are interpreted to date the emplacement of the igneous protolith ages of inherited zircons of two orthogneisses range from 2 5 to 2 4 ga indicating late archaean early proterozoic crustal components in combination with published ages for other aegean metagranitoids the new u pb ages provide additional evidence of a temporally restricted period of plutonism in the pre alpine aegean region from 325 to 300 ma comparing the post neoproterozoic evolution of the investigated basement with that of the cycladic and pelagonian basements and of the continental massifs of ne greece and turkey we argue that all these crustal blocks were part of the gondwana derived cimmerian terrane based on the spatial and temporal distribution of late carboniferous aegean plutonism we suggest that this period of magmatic events results from the southward subduction of palaeotethys beneath the marginal fragments of northern gondwana

extreme wave climate variability in southern europe using satellite data 1 a time dependent generalized extreme value gev model for monthly significant wave height maxima from satellite databases is used to model the seasonal and interannual variability of the extreme wave climate throughout southern europe in order to avoid a misleading use of the maxima time series the classical extreme value model has been modified to cope with nonhomogeneous monthly observations seasonality is represented using intraannual harmonic functions in the model while interannual variability is modeled including north atlantic and mediterranean regional scale sea level pressure predictors such as the north atlantic oscillation nao the east atlantic ea or the east atlantic western russian ea wr patterns the results quantify the strong spatial variability detected in the seasonal location and scale gev parameters in general prominent zonal west east and meridional north south gradients of these location and scale parameters reveal the predominance of low pressure centers located in the nao region e g a gradient of 4 m for the location parameter and 1 5 units for the scale parameter between north south is shown in the month of september the model also quantifies the influence of regional climate patterns on extreme wave climate results show a great influence of nao and ea on the atlantic basin e g every unit of the monthly nao index explains 25 cm of the extreme wave height in the gulf of biscay and the ea index explains 20 cm while the negative phases of ea wr contribute greatly to the western mediterranean basin

regional frequency analysis of extreme waves in a coastal area abstract this study analysed the wave data from several locations in a coastal region to identify the areas with comparable wave height statistics and to estimate regional extreme significant wave heights of designated return periods the regional frequency analysis algorithm executed in this work utilised the significant wave height data from 35 sites 35 45 n 6 5 11 0 w in a coastal grid 0 25 0 25 off portugal in the north atlantic ocean extracted from 44 years hipocas hindcast wave database regional frequency analysis algorithms based on l moments identified the discordant sites discordant site statistics are substantially diffused from the group of sites statistics assisted in the formation of homogeneous regions by cluster analyses data vectors include site characteristics and site statistics and consequently selected appropriate regional frequency distributions by z goodness of fit test statistic at 90 level of significance to estimate regional extreme significant wave height quantiles of designated return periods the regional frequency analysis algorithm recognised in certain cases neighbouring sites as members of diverse regions revealing that geographical proximity of sites are not ascertaining factors to form homogeneous regions at site analyses along with regional frequency analysis enabled to apprehend the precision of the regional extreme quantile as genuine feature of its at site extreme quantiles

detrital zircon and micropalaeontological ages as new constraints for the lowermost tectonic unit talea ori unit of crete greece the talea ori unit is the lowermost known tectonic unit of crete and the most external part of the hellenides its stratigraphy ranges from late carboniferous to oligocene and outcrops of the lower part are only known in the talea ori mountains central crete in this area a black sandstone at the base of the galinos beds thought to be the oldest formation contains zircons which were dated using the single grain evaporation method the majority of these grains yielded late carboniferous ages variscan while a small group yielded early proterozoic ages the age distribution of these zircons suggests that at the carboniferous permian boundary not much of the older north gondwanan basement was exposed and that a river system carried detrital material from the variscan belt towards the forming neotethyan rift additionally higher up in the stratigraphy benthic foraminifers miliolids were found in clasts from a conglomerate which was so far thought to be of early triassic age epting m kudrass h r leppig u schaffer a 1972 geologie der talea ori kreta n jb geol palaont abh 141 259 285 these miliolids belong to the species hoyenella inconstans michalik j jendrejakova o borza k 1979 some new foraminifera species of the fatra formation uppermost triassic in the west carpathians geol carpath 30 1 61 91 thus attributing a late triassic carnian norian maximal age to this conglomerate the carbonate platform from which the miliolids bearing clasts come is not known the presence to the north of a continuous hemipelagic record from the carboniferous to the triassic phyllite quartzite and tripali units attributed to the palaeotethys realm allows the talea ori unit and its lateral equivalents the ionian zone to be assigned to the westward continuation of the cimmerian block and therefore to the northern margin of the east mediterranean neotethys ocean

late permian early triassic igneous activity in the attic cycladic belt attica new geochronological data and geodynamic implications article i nfo article history igneous rocks of the attic cycladic belt acb formed prior to the alpine orogeny have received relatively little attention especially regarding their crystallisation age new u pb shrimp zircon data from mylonitised metagranitoid rocks within metapelites and metabasites of the pentelikon mountain lower tectonic unit ltu of attica in combination with internal zircon characteristics reveal the following the metagranitoid precursor was very likely an i type pluton crystallising in two successive stages at 255 3 ma and 246 2 ma weighted mean 206 pb 238 u ages error at 95 c l these age results are respectively marginally older than and within un certainty of the 240 4 ma protolith age reported for metagranitoids of the same unit in the area of lavrion at tica they are in line with the protolith ages of several meta igneous rocks within the cycladic blueschist unit of aegean islands one core zircon domain and one single zircon grain yielded

the use of laboratory velocity data for estimating temperature and partial melt fraction in the low velocity zone comparison with heat flow and electrical conductivity studies peridotite is widely considered to be the dominant component of the upper most mantle seismic velocities of a dry peridotite determined in the laboratory at high pressure and hypersolidus temperature show a rapid decrease with increasing temperature the strong temperature dependence of velocities can be used to estimate temperature and melt fraction in the low velocity zone of the earth the laboratory results show that the pressure dependence of both velocity and melt fraction appears to be well accounted for by the pressure dependence of the solidus temperature of the peridotite i e homologous temperature dependence this observation allows us to extrapolate laboratory results to higher pressures greater depths with some confidence requiring only a knowledge of the solidus as a function of pressure using the ratios of lithospheric to asthenospheric velocities temperature and melt fraction in the asthenosphere the low velocity zone can be determined from laboratory velocity data examples of thermal structures of the upper mantle beneath oceanic plates are presented we choose three locations of geophysical interest iceland plateau pacific ocean and philippine sea where reliable seismic velocities have been determined in the upper mantle from surface wave studies a large amount of partial melt 5 vol and a higher temperature than the dry peridotite solidus are inferred in 0 5 m y asthenosphere under the iceland plateau and the active marginal basin of the east philippine sea the partial melt zone appears to extend deeper 100 km and to greater ages 20 m y in the pacific ocean region than under the slowly spreading iceland plateau partial melting is not expected in the asthenosphere older than 5 m y under the iceland plateau even though the volume fraction of partial melt is not so large 3 vol beneath the pacific plate the melting zone may extend to a distance of above 2000 km from the ridge many seamounts observed in the pacific ocean may result from this vast region of melting under the plate we suggest a linear relation between the width of melting zone and the plate velocity the laboratory results are also applied to other low velocity zones it is suggested that a velocity drop up to about 6 in the asthenosphere does not necessarily require the existence of partial melt but can be explained by high subsolidus temperature this implies that partial melt may not exist generally but only in limited areas in the low velocity zone comparison of seismic results with theoretical models may overestimate the temperature and melt fraction if the velocity drop at subsolidus temperature is neglected temperature and melt fraction obtained in this study are discussed together with results from heat flow and electrical studies almost the same temperatures as inferred from seismic velocity and a dry peridotite solidus are calculated from heat flow data indicating that the upper mantle under mid ocean ridges may be fairly dry even a water or co2 undersaturated solidus 0 1 wt does not give a temperature consistent with the lithospheric geotherm and laboratory velocity results it is noted that electrical conductivity studies generally yield lower temperatures and larger melt fractions than this study unknown pressure frequency and impurity effects on laboratory conductivities of partially molten mantle rocks are suggested as possible reasons for this discrepancy

development of regional flood duration frequency curves based on the index flood method abstract the aim of this research paper is to develop a statistical model that provides a more complete description of a basin s flood regime the approach adopted in this paper is based on the flood duration frequency qdf analysis which takes into account the temporal variability of floods this approach is analogous to the intensity duration frequency idf model commonly used for rainfall analysis the proposed model allows qdf curves for a given basin to be estimated while using a minimum number of parameters this model is called converging model because of the observed convergence of distributions towards small return periods a local at site model and a regional approach are developed the regional approach uses classical concepts of regional hydrologic frequency analysis index flood if method and can be used for basins where no streamflow data is available results from 158 catchments located in the provinces of quebec and ontario canada are used to illustrate the method

on the sheltering effect of islands in ocean wave models 1 the effect of resolving relatively small islands in a third generation wave model covering the whole north atlantic is shown to have noticeable effects at long distances from the islands in addition to the local effects that have been reported earlier to resolve the islands a very fine grid is adopted locally which is then nested in the overall model the examples presented show the shadowing effect of azores islands for three specific wave conditions when they come from the southwest from the west and from the northwest the sheltering effect of the islands was demonstrated by a reduction of the significant wave height in the region on the leeward side of azores archipelago when comparing the wave model results with the island resolved and unresolved

thresholds for storm impacts on an exposed sandy coastal area in southern portugal abstract storms are one of the most important phenomena responsible for coastal erosion their destructive power presents major challenges for coastal management and knowledge of their characteristics and associated consequences is therefore of paramount importance in this study thresholds for storm impacts are defined for a sandy coast in southern portugal faro beach ria formosa using two different approaches i hydrodynamic conditions associated with historical storm impacts i e infrastructural damage and ii computed maximum wave run up values r high compared with beach morphology damage thresholds are defined as limits above which the action of a storm exceeds beach front response capability and starts to act directly on human infrastructures according to method i four different thresholds were defined for individual storms directed from the sw the threshold is a significant wave height of 4 7 m with a storm duration of 2 days and for storms directed from the se is a significant wave height of 6 m with a storm duration of at least 2 days regarding storm groups for those directed from the sw the threshold is 2 storms lasting at least 2 days each with significant wave heights greater than 3 5 m whilst for those directed from the se the threshold is 3 short storms lasting 1 day each with significant wave height over 3 9 m the return period for the sw storm group threshold is just 1 7 years for method ii beach morphological parameters d high highest elevation of the frontal dune d low elevation of the dune base and tan f foreshore slope were determined for five chosen cross shore profiles along the study area and r high computed for different hydrodynamic conditions results were validated through field observations of storm impacts the lowest thresholds for overwash are along the central part of the study area where a dune crest is absent due to human occupation the highest thresholds for overwash are on those profiles where a frontal dune is well developed or a foredune ridge is present western and eastern parts of the study area this study presents a methodological strategy to compute realistic thresholds for storm impacts along faro beach based on historical datasets of hydrodynamics and storm impacts information the approach could be implemented in other coastal areas to provide a comprehensive assessment of the storm impact requiring only simple information like offshore storm hydrodynamics characteristics beach morphology and reports of coastal infrastructure damage

storminess and surges in the south western approaches of the eastern north atlantic the synoptic climatology of recent extreme coastal storms abstract the climatology of intense winter cyclone events in the eastern north atlantic responsible for high magnitude surge generation top 1 of events within the region of the south western approaches to northwest france and southwest england is extracted from daily sea level and 500 hpa level atmospheric pressure analyses cluster analysis yields discrete cyclone track regimes linked to upper airflow patterns being responsible for the generation of intense storms central pressure at sea level 990 hpa which promote severe surge events 60 cm along the french coast of the south western approaches fluctuations in storminess are strongly influenced by the southward intrusion and strengthening of the jet stream in mid atlantic these occurrences are often associated with negative sea surface temperature sst anomalies near newfoundland and a strengthening of the thermal gradient across the atlantic well to the south of its normal position resultant cyclogenesis promotes storms displaying a delay in minimum central pressure attainment until well east of 14 w encouraging enhancement of surge flow stepwise multiple regression analysis indicates that the most influential variables in promoting severe surge events in the south western approaches are trans atlantic sea surface temperature gradients the most important influence is the prevailing west east sea surface temperature gradient during the month of the storm followed by that for the prior month of the storm and thirdly the north south sea surface temperature gradient prevailing during the month of the event other influential variables reflect the character of the cyclone storm duration mean deepening rate of storm central pressure the value of the outermost closed isobar around the storm centre and the longitudinal position of the outermost closed isobar to the right of the cyclone track in contrast the north atlantic oscillation nao is not very effective as a discriminator of surge activity this may reflect the greater intra month volatility of parameters used to derive the nao index than of other monthly variables considered in the study the lack of resolvability at the individual storm level probably also arises because of the monthly detailing of the nao against storms of 2 3 days duration this behavioural model of extreme storminess in the south western approaches to northwest france provides the basis by which extremes of coastal susceptibility can be calibrated

effect of dynamic melting on acoustic velocities in a partially molten peridotite abstract the mechanical effect of materials with a zero shear modulus aggregated with solids with non zero shear moduli has been the primary motivation for why partially molten rocks should have lowered shear wave velocities we propose that elastic softening associated with the process of melting must also be considered in this view seismic waves propagating in regions of partial melting perturb the thermodynamic state and drive solid to liquid and liquid to solid thereby lowering the effective elastic moduli we present measurements of young s modulus for a mantle peridotite klb1 at lvz pressures and temperatures and seismic frequency that support this model the model predicts that the softening of elastic modulus is controlled by the pressure dependence of melt fraction f p and not the percentage of melt present in contrast to previous models the p wave velocity is decreased by nearly the same percentage as the s wave velocity

shear wave attenuation and dispersion in melt bearing olivine polycrystals 2 microstructural interpretation and seismological implications 1 the torsional forced oscillation tests of melt bearing olivine aggregates reported by jackson et al 2004 consistently show a peak in attenuation that is absent from melt free aggregates tested under similar conditions and grain sizes characterization by sem shows that the melt resides in triple junction tubules and larger pockets as previously described tem imaging and eds analysis reveals that olivine olivine grain boundaries are characterized by a region 1 nm wide which is structurally and chemically distinct from olivine grain interiors from the possible mechanisms that can produce an anelastic attenuation peak melt squirt can be eliminated for our samples and experimental conditions we attribute the observed attenuation peak to elastically accommodated grain boundary sliding requiring that the grain boundaries are weak relative to olivine grain interiors but have a significantly higher viscosity than bulk melt while the nanometer scale grain boundary structure in the melt bearing aggregates is essentially the same as for melt free aggregates studied previously elastically accommodated sliding in the latter is apparently inhibited by tight three grain edge intersections the exponentially increasing high temperature background attenuation in both types of aggregate is attributed to diffusionally accommodated grain boundary sliding extrapolation to mantle grain sizes shows that the broad peak may be responsible for nearly frequency independent attenuation in partially molten regions of the upper mantle

serbo macedonian revisited a silurian basement terrane from northern gondwana in the internal hellenides greece abstract new geochronological and geochemical data on basement orthogneisses from the vertiskos unit of the serbo macedonian massif smm internal hellenides northern greece are used in order to constrain the pre alpine tectonic history of the basement units in the metamorphic hinterland of the hellenides the prevailing rock types in the vertiskos crystalline basement are coarse grained biotite augengneisses with subordinate leucocratic muscovite gneisses and two mica gneisses zircon pb pb and u pb ages on 20 samples range from 425 9 4 2 ma to 443 4 5 5 ma with a mean of 432 2 3 2 ma and are interpreted as primary crystallisation ages of the basement granites on the basis of the magmatic internal structure of the zircon grains trace element and isotope geochemistry of the gneisses show that they originated in a magmatic arc setting but also contain material from pre existing continental crust the rocks are slightly peraluminous and some leucocratic gneisses are strongly depleted in incompatible trace elements the zircon ages document an early silurian magmatic phase in the internal hellenides the association of lithologies and ages is distinctly different from that of the adjacent basement massifs this difference in basement provenance and the fact that the vertiskos unit is bordered by ophiolitic material both to the west and to the east leads to the conclusion that this part of the smm is an exotic terrane of northern gondwanan origin which was finally accreted to its present position during the alpine orogeny the vertiskos terrane may have been part of the hun superterrane which evolved at the northern active continental margin of gondwana in the early palaeozoic and rifted away from it during the opening of the rheic ocean in the cambrian to silurian parts of this superterrane such as the vertiskos terrane are present throughout the variscan and alpine orogens

zircon geochronology of basement rocks from the pelagonian zone greece constraints on the pre alpine evolution of the westernmost internal hellenides the pelagonian zone of greece is the westernmost segment of the internal hellenides comprising widespread crystalline basement exposures of granites and orthogneisses we dated these basement rocks in order to identify the major crust forming episodes and to understand the evolutionary history of the area in our study we investigated granites gneisses meta rhyolites and mylonites from the major occurrences of the pelagonian zone we applied single zircon dating techniques such as pb pb evaporation conventional u pb and shrimp the majority of the basement rocks gave permo carboniferous intrusion ages thus emphasizing the importance of this crust forming event for the internal hellenides of greece triassic intrusion ages were obtained however for a meta rhyolite from the western pelagonian zone and two mylonites from the eastern pelagonian zone these ages are interpreted to reflect magmatism accompanying early rifting that led to the subsequent opening of the pindos ocean to the west and the meliata ocean to the east of the pelagonian zone the geochronological results demonstrate that the magmatic episodes during which most of the pelagonian zone crystalline basement formed are predominantly pre alpine in age

effect of phase transitions on compressional wave velocities in the earth s mantle the velocities of seismic waves in the earth are governed by the response of the constituent mineral assemblage to perturbations in pressure and stress the effective bulk modulus is significantly lowered if the pressure of the seismic wave drives a volume reducing phase transformation a comparison between the amount of time required by phase transitions to reach equilibrium and the sampling period thus becomes crucial in defining the softening and attenuation of compressional waves within such a two phase zone these phenomena are difficult to assess experimentally however because data at conditions appropriate to the earth s deep interior are required here we present synchrotron based experimental data that demonstrate softening of the bulk modulus within the two phase loop of olivine ringwoodite on a timescale of 100 s if the amplitude of the pressure perturbation and the grain size are scaled to those expected in the earth the compressional wave velocities within the discontinuities at 410 520 and possibly 660 km are likely to be significantly lower than otherwise expected the generalization of these observations to aluminium controlled phase transitions raises the possibility of large velocity perturbations throughout the upper 1 000 km of the mantle

44 year wave hindcast for the north east atlantic european coast this paper describes a 44 year from 1958 to 2001 wave hindcast conducted for the north atlantic using a fine grid in the north east atlantic coastal areas of europe the wind fields were obtained by a local area model that was applied in the areas adjacent to the european coasts which was forced by the results of the ncep reanalysis while the ncep results have a spatial distribution of 2 and a time step of 6 h the wind fields produced by the local area model have a spatial resolution of 0 5 and a time step of 1 h which is important for accurate descriptions of the conditions in coastal areas and in rapidly changing storms a version of the wam model that allowed two way nesting was adopted and calculations were made with nested grids allowing a fine resolution in the coastal areas of europe this paper includes the description of the set up of the wave model and the validation performed vs in situ measurements so as to allow assessments of the quality of the data produced in this study

olivine flow mechanisms at 8 gpa abstract the mechanisms responsible for high temperature olivine deformation are investigated at a pressure of 8 gpa and temperatures up to 1780 k san carlos olivine specimens of different average grain sizes 0 5 and 5 m were deformed simultaneously between hard alumina pistons during relaxation experiments these experiments are carried out in a multi anvil high pressure apparatus coupled with synchrotron x ray radiation the different grain size specimens experienced identical p t stress condition at any given time a new method for measuring strains and strain rates 10 6 s 1 of specimens at high pressure is documented this method uses time resolved in situ x ray imaging and an image analysis computation the microstructures of run products recovered after being quenched at different temperatures were characterized by transmission electron microscopy tem we find that high temperature olivine flow is grain size insensitive at 8 gpa which suggests that dislocation creep dominates olivine deformation at high pressure this result is confirmed by the tem investigation of our deformed specimens in which we find evidences of the activation of olivine dislocation slip systems specimen microstructures are consistent with dynamic recrystallization as an assisting process in olivine deformation during the high pressure experiments extrapolation of our results to the low stress level and large grain size expected in the mantle suggests that dislocation creep assisted by dynamic recrystallization may also dominate natural olivine deformation in the upper mantle

the oldest rocks of greece first evidence for a precambrian terrane within the pelagonian zone the pelagonian zone in greece represents the westernmost belt of the hellenide hinterland internal hellenides previous geochronological studies of basement rocks from the pelagonian zone have systematically yielded permo carboniferous ages in this study we demonstrate for the first time the existence of a precambrian crustal unit within the crystalline basement of the pelagonian zone the u pb single zircon and shrimp ages of these orthogneisses vary from 699 7 ma to 713 18 ma which identify them as the oldest rocks in greece these late proterozoic rocks which today occupy an area of c 20 100 km are significantly different from the neighbouring rocks of the pelagonian zone they are therefore interpreted as delineating a terrane named here the florina terrane during the permo carboniferous florina was incorporated into an active continental margin where it formed part of the basement for the pelagonian magmatic arc the activity of this arc was dated in this study by single zircon pb pb ages as having taken place at 292 5 ma and 298 7 ma during the alpine orogeny florina together with the pelagonian zone eventually became a constituent of the hellenides geochemically the florina orthogneisses represent granites formed at an active continental margin because of the late proterozoic ages this late proterozoic active continental margin can be correlated to a pan african or cadomian arc as the gneisses contain inherited zircons of late to middle proterozoic age the original location of florina was probably at the northwestern margin of gondwana similar to other gondwana derived terranes such as east avalonia florina approached the southern margin of eurasia during palaeozoic times where it became part of an active continental margin above the subducting palaeotethys these interpretations further indicate that terrane accretion was already playing an important role in the early pre alpine evolution of the hellenides

tectonic sedimentary evolution of the western margin of the mesozoic vardar ocean evidence from the pelagonian and almopias zones northern greece

extreme wave statistical methods and implications for coastal analyses abstract this work reviews methods for extreme value analysis of ocean waves including site specific univariate analysis environmental contour analysis and spatial analysis a variation of regional frequency analysis is proposed based on the hypothesis that the distribution of extreme wave events at different sites within a homogeneous region are identical except for a shift due to a location parameter with this assumption the shape and scale parameters of the distribution can be determined with greater certainty by pooled measurements while the spatial variation is captured by the location parameter which is equal to a threshold wave height and may be more reliably sourced from a computational model as compared to the extreme values themselves this approach attempts to overcome the lack of accuracy of most wave models in extreme wave events by basing the shape and scale parameters on measurements while using a wave hind cast in a range where it is acceptably accurate to find the spatially varying location parameter the methods are applied to a case study of the canadian pacific coast un sheltered measurement sites were found to satisfy statistical homogeneity and were used to define a regional shifted extreme value distribution a high resolution numerical model was used to define the spatially varying location parameter equal to the 98th percentile of significant wave heights in general the results are satisfactory and suggest this approach may be a useful tool in understanding the spatial variability of wave extremes however it is acknowledged that this approach relies on the availability of multiple measurement sites with sufficient duration to support extreme value analysis

petrogenesis and tectonic significance of jurassic iat magma types in the hellenide ophiolites as deduced from the rhodiani ophiolites pelagonian zone greece abstract the rhodiani ophiolites are represented by two tectonically superimposed ophiolitic units the lower ultramafic unit and the upper volcanic unit both bearing calcareous sedimentary covers the ultramafic unit consists of mantle harzburgites with dunite pods and chromitite ores and represents the typical mantle section of supra subduction zone ssz settings the volcanic unit is represented by a sheeted dyke complex overlain by a pillow and massive lava sequence both including basalts basaltic andesites andesites and dacites chemically the volcanic unit displays low ti affinity typical of island arc tholeiite iat ophiolitic series from ssz settings having as most distinctive chemical features low ti v ratios the rare earth element and incompatible element composition of the more primitive basaltic andesites from the rhodiani ophiolites can be successfully reproduced with about 15 non modal fractional melting of depleted lherzolites which are very common in the hellenide ophiolites the calculated residua correspond to the depleted harzburgites found in the rhodiani and othrys ophiolites both field and chemical evidence suggest that the whole sequence of the rhodiani volcanic unit from basalt to dacite originated by low pressure fractional crystallization under partially open system conditions the modelling of mantle source melt generation and mantle residua carried out in this paper provides new constraints for the tectono magmatic evolution of the mirdita pindos oceanic basin

a hybrid efficient method to downscale wave climate to coastal areas long term time series of sea state parameters are required in different coastal engineering applications in order to obtain wave data at shallow water and due to the scarcity of instrumental data ocean wave reanalysis databases ought to be downscaled to increase the spatial resolution and simulate the wave transformation process in this paper a hybrid downscaling methodology to transfer wave climate to coastal areas has been developed combining a numerical wave model dynamical downscaling with mathematical tools statistical downscaling a maximum dissimilarity selection algorithm mda is applied in order to obtain a representative subset of sea states in deep water areas the reduced number of selected cases spans the marine climate variability guaranteeing that all possible sea states are represented and capturing even the extreme events these sea states are propagated using a state of the art wave propagation model the time series of the propagated sea state parameters at a particular location are reconstructed using a non linear interpolation technique based on radial basis functions rbfs providing excellent results in a high dimensional space with scattered data as occurs in the cases selected with mda the numerical validation of the results confirms the ability of the developed methodology to reconstruct sea state time series in shallow water at a particular location and to estimate different spatial wave climate parameters with a considerable reduction in the computational effort

kinetics of melting in peridotite from volume strain measurements abstract partial melting in the earth s mantle involves a combination of processes such as ionic diffusion and solid liquid transition these processes yield an array of characteristic times for the melting kinetics both the magnitude and time constant of melt induced volume strain affect seismic velocity attenuation and buoyancy in situ monitoring of samples during melting are enabled by multi anvil high pressure devices coupled with synchrotron x ray radiation in this study the volume strain induced in a sample from melting is measured as a function of time using x ray images we find a doubling of the effective thermal expansion for only 2 melt both from our data and from thermodynamic models of peridotite the characteristic time of melting is determined to be less than one second these findings have a direct impact on the effect of melting on seismic velocities