the role of earthquakes in inducing sediment mass movements in the eastern korinthiakos gulf an example from the february 24 march 4 1981 activity abstract korinthiakos gulf is a narrow arm of the sea connecting the ionian and the aegean seas through the rion antirion strait and the korinth canal respectively the eastern part of korinthiakos was surveyed by the marine geology department of the institute of geology and mineral exploration of greece using a 3 5 khz subbottom profiler the survey was carried out a short time after intensive earthquake activity which occurred in the area from february 24 to march 4 1981 during this activity three major shocks of magnitudes ranging from 6 4 to 6 7 took place the subbottom profiles reveal a sediment mass which was deposited by submarine slumping in the alkyonides basin which lies at the eastern end of the studied area the slump is about 10 km long 1 5 to 2 0 km wide and its areal extent is about 16 km2 the scarp area occurs at a bathymetric depth of about 100 to 250 m in the northeastern part of the basin the scarp faces are from 10 to 15 m high and have a total areal extent of about 4 km2 the destruction of fishing nets of trawling boats and other evidence indicates that the triggering of the mass flow was effected by the earthquake activity and probably by the first major shock scarp areas and scarp faces from which sediment masses have been removed were detected in other shallow and deep sectors of the studied area indicating that mass transport processes are very common in this area of high seismicity

estimating groundwater exchange with lakes 1 the stable isotope mass balance method groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope 18o 16o mass balance method the stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network in this paper the method is applied to a lake in northern wisconsin demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist inflow and outflow rates calculated for the wisconsin lake using the isotope mass balance method are 29 and 54 cm yr respectively which compare well to estimates derived independently using a three dimensional groundwater flow and solute transport model of 20 and 50 cm yr such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes in addition utilization of stable isotopes in studies of groundwater lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers

tsunamigenic sources in an active european half graben gulf of corinth central greece abstract the gulf of corinth is an active half graben dissecting the mainland of greece along an east west axis the gulf is well known for its intense seismic activity and its rapid extension rates however published historical catalogues reveal that the gulf of corinth is also the site of frequent and relatively destructive tsunami occurrences this paper presents a comparative study of the potential of probable tsunami sources in the gulf of corinth by referring to published offshore geology data coseismic seafloor displacement along offshore faults and submarine mass failures are the active tsunamigenic sources the paper applies easy to use empirical and semi empirical equations that estimate the generated tsunami wave height just over the source area building upon the most probable worst case scenarios for both coseismic fault displacement and submarine mass failure generated tsunamis the tsunami potential of its case is explored a maximum probable 6 7 m w offshore earthquake would produce a rupture on the seafloor surface with a maximum displacement of 0 66 to 1 08 m in height in the gulf of corinth the tsunami which would be generated by the seafloor displacement would have a wave height of the same magnitude as the seafloor displacement furthermore existing evidence of submarine mass failures that took place over the last 3000 years in the eastern part of the corinth gulf had and would have the potential of generating tsunamis with a maximum wave height of 1 04 and 4 04 m and maximum wave length of 4 52 and 6 25 km

numerical analysis of the mobility of the palos verdes debris avalanche california and its implication for the generation of tsunamis abstract analysis of morphology failure and post failure stages of the palos verdes debris avalanche reveals that it may have triggered a significant tsunami wave our analysis of the failure itself indicates that the slope is stable under aseismic conditions but that a major earthquake with a magnitude around 7 could have triggered the slide a post failure analysis considering the debris avalanche as a bi linear flow shows that peak velocities of up to 45 m s could have been reached and that the initial movement involved a mass of rock less than 10 km wide 1 km long and about 50 80 m thick initial wave height estimates vary from 10 to 50 m tsunami waves propagating to the local shoreline would be significantly smaller such a range demonstrates our lack of proper knowledge of the transition from failure to post failure behavior related to mass movements further investigations and analyses of terrestrial and submarine evidence are required for a proper hazard assessment related to tsunami generation in the los angeles area

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

shrimp u pb zircon geochronology and thermal modeling of multilayer granitoid intrusions implications for the building and thermal evolution of the central system batholith iberian massif spain abstract this work shows the results of a u pb shrimp zircon geochronological study of the central part of the gredos massif spanish central system batholith the studied batholith is composed of several granodiorite and monzogranite tabular bodies around 1 km thick each intruded into partially molten pelitic metasediments granodiorites and monzogranites belonging to three distinct intrusive bodies and samples of anatectic leucogranites have been selected for shrimp u pb zircon geochronology distinct age groups separated by up to 20 ma have been distinguished in each sample important age differences have also been determined among the most representative age groups of the three analyzed granitoid bodies 312 6 2 8 ma for the circo de gredos bt granodiorites floor intrusive layer 306 9 1 5 ma for the barbellido plataforma granitoids top intrusive layer and 303 5 2 8 ma for las pozas crd monzogranites middle intrusive layer these age differences are interpreted in terms of sequential emplacement of the three intrusive bodies contemporary with the late paleozoic d3 deformation phase the anatectic leucogranites are coeval to slightly younger than the adjacent intrusive granodiorites and monzogranites 305 4 1 6 ma for refugio del rey leucogranites and 303 2 ma for migmatitic hornfelses it is suggested that these anatectic magmas were generated in response to the thermal effects of granodiorite intrusions thermal modeling with comsol multiphysics reveals that sequential emplacement was able to keep the thermal conditions of the batholith around the temperature of zircon crystallization in granitic melts around 750 c for several million of years favoring the partial melting of host rocks and the existence of large magma chambers composed of crystal mush prone to be rejuvenated after new intrusions

some aspects of energy balance and tsunami generation by earthquakes and landslides tsunamis are generated by displacement or motion of large volumes of water while there are several documented cases of tsunami generation by volcanic eruptions and landslides most observed tsunamis are attributed to earthquakes kinematic models of tsunami generation by earthquakes where specified fault size and slip determine seafloor and sea surface vertical motion quantitatively explain far field tsunami wave records on the other hand submarine landslides in subduction zones and other tectonic settings can generate large tsunamis that are hazardous along near source coasts furthermore the ongoing exploration of the oceans has found evidence for large paleo landslides in many places not just subduction zones thus we want to know the relative contribution of faulting and landslides to tsunami generation for earthquakes only a small fraction of the minimum earthquake energy less than 1 for typical parameter choices for shallow underthrusting earthquakes can be converted into tsunami wave energy yet this is enough energy to generate terrible tsunamis for submarine landslides tsunami wave generation and landslide motion interact in a dynamic coupling the dynamic problem of a 2 d translational slider block on a constant angle slope can be solved using a green s function approach for the wave transients the key result is that the largest waves are generated when the ratio of initial water depth above the block to downslope vertical drop of the block h 0 w sin is less than 1 the conversion factor of gravitational energy into tsunami wave energy varies from 0 for a slow velocity slide in deep water to about 50 for a fast velocity slide in shallow water and a motion abruptly truncated to compare maximum tsunami wave amplitudes in the source region great earthquakes produce amplitudes of a few meters at a wavelength fixed by the fault width of 100 km or so for submarine landslides tsunami wave heights as measured by b block height are small for most of the parameter regime however for low initial dynamic friction and values of h 0 w sin less than 1 tsunami wave heights in the downslope and upslope directions reach b and b 4 respectively wavelengths of these large waves scale with block width for significant submarine slides the value of b can range from meters up to the kilometer scale thus the extreme case of efficient tsunami generation by landslides produces dramatic hazards scenarios

groundwater recharge and discharge dynamics in an arid zone ephemeral lake system australia the coongie lakes are a series of ephemeral freshwater lakes on the lower reaches of cooper creek a large intermittent river of the arid lake eyre basin australia hydrogeological chemical and isotopic observations in conjunction with numerical modeling of groundwater responses to lake inundation events have been used to identify the dominant processes linking shallow unconfined groundwater with the hydrology of the lakes during wet and dry periods the lakes are predominantly zones of net groundwater recharge during inundation events however soil profile data suggests that drying of some of these lakes allows evaporative groundwater discharge to occur through the soil profile of the dry lake beds resulting in salinization of the soil profile of the more ephemeral lakes the occurrence of young high salinity groundwater is best explained by variations in soil profile flushing in response to wet and dry interannual periods of river discharge during interannual drier phases when filling of previously dry lakes is more common recharge is mostly via macropore flow during the rising stage of the inundation increased salinization of the lake bed sediments occurs during longer dry periods due to transport of solutes to the near surface from lake bed evaporation and limited flushing of the soil profile because of the macropore dominated flow during recharge during wet periods recharge is more likely dominated by matrix flow that results in leaching of the soil profile and increased export of solutes into the alluvial aquifer

isotopic tracing of the source water for cedar bog in west central ohio usa abstract cedar bog a boreal fen in west central ohio is home for many endangered plants and animals the whereabouts of the water source that sustains cedar bog has been the subject of several investigations in the past two decades some of these studies indicated that a recharge area lies to the east and northeast of the bog using environmental isotopes of oxygen and hydrogen the present study positively identifies a major recharge area located northeast of the bog and enclosed by two small tributaries of the mad river oxygen isotopic composition and tritium contents of ground water suggest that the bog water is only a few years old

fluid record of rock exhumation across the brittle ductile transition during formation of a metamorphic core complex naxos island cyclades greece fluid inclusions trapped in quartz veins hosted by a leucogneiss from the southern part of the naxos metamorphic core complex attic cycladic massif greece were studied to determine the evolution of the fluid record of metamorphic rocks during their exhumation across the ductile brittle transition three sets of quartz veins v m2 v bd v b are distinguished the v m2 and v bd are totally or respectively partially transposed into the foliation of the leucogneiss they formed by hydrofracturing alternating with ductile deformation accommodated by crystal plastic deformation the v b is discordant to the foliation and formed by fracturing during exhumation without subsequent ductile transposition fluids trapped during crystalplastic deformation comprise two very distinct fluid types namely a co2 rich fluid and a high salinity brine that are interpreted to represent immiscible fluids generated from metamorphic reactions and the crystallization of magmas respectively they were initially trapped at approximate to 625 degrees c and 400mpa and then remobilized during subsequent ductile deformation resulting in various degrees of mixing of the two end members with later trapping conditions of approximate to 350 degrees c and 140mpa in contrast brittle microcracks contain aqueous fluids trapped at 250 degrees c and 80mpa all veins display a similar 13c pointing to carbon that was trapped at depth and then preserved in the fluid inclusions throughout the exhumation history in contrast the d signature is marked by a drastic difference between i v m2 and v bd veins that are dominated by carbonic aqueous carbonic and high salinity fluids of metamorphic and magmatic origin characterized by d between 56 parts per thousand and 66 parts per thousand and ii v b veins that are dominated by aqueous fluids of meteoric origin characterized by d between 40 parts per thousand and 46 parts per thousand the retrograde pt pathway implies that the brittle ductile transition separates two structurally chemically and thermally distinct fluid reservoirs namely i the ductile crust into which fluids originating from crystallizing magmas and fluids in equilibrium with metamorphic rocks circulate through a geothermal gradient of 30 degrees c km1 at lithostatic pressure and ii the brittle upper crust through which meteoric fluids percolate through a high geothermal gradient of 55 degrees c km1 at hydrostatic pressure

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

development of fluid conduits in the auriferous shear zones of the hutti gold mine india evidence for spatially and temporally heterogeneous fluid flow abstract the gold mineralization of the hutti mine is hosted by nine parallel n s trending steeply dipping 2 10 m wide shear zones that transect archaean amphibolites the shear zones were formed after peak metamorphism during retrograde ductile d 2 shearing in the lower amphibolite facies they were reactivated in the lower to mid greenschist facies by brittle ductile d 3 shearing and intense quartz veining the development of a s 2 s 3 crenulation cleavage facilitates the discrimination between the two deformation events and contemporaneous alteration and gold mineralization ductile d 2 shearing is associated with a pervasively developed distal chlorite sericite alteration assemblage in the outer parts of the shear zones and the proximal biotite plagioclase alteration in the center of the shear zones d 3 is characterized by development of the inner chlorite k feldspar alteration which forms a centimeter scale alteration halo surrounding the laminated quartz veins and replaces earlier biotite along s 3 the average size of the laminated vein systems is 30 50 m along strike as well as down dip and 2 6 m in width mass balance calculations suggest strong metasomatic changes for the proximal biotite plagioclase alteration yielding mass and volume increase of ca 16 and 12 respectively the calculated mass and volume changes of the distal chlorite sericite alteration ca 11 ca 8 are lower the decrease in 18 o values of the whole rock from around 7 5 for the host rocks to 6 7 for the distal chlorite sericite and the proximal biotite plagioclase alteration and around 5 for the inner chlorite k feldspar alteration suggests hydrothermal alteration during two stage deformation and fluid flow the ductile d 2 deformation in the lower amphibolite facies has provided grain scale porosities by microfracturing the pervasive steady state fluid flow resulted in a disseminated style of gold sulfide mineralization and a penetrative alteration of the host rocks alternating ductile and brittle d 3 deformation during lower to mid greenschist facies conditions followed the fault valve process ductile creep in the shear zones resulted in a low permeability environment leading to fluid pressure build up strongly episodic fluid advection and mass transfer was controlled by repeated seismic fracturing during the formation of laminated quartz gold veins the limitation of quartz veins to the extent of earlier shear zones indicate the importance of pre existing anisotropies for fault valve action and economic gold mineralization

earthquake induced coastal sediment instabilities in the western gulf of corinth greece abstract on june 15 1995 a locally 6 2 r destructive earthquake occurred in the western gulf of corinth and caused extensive onshore and offshore sediment instabilities a detailed offshore geophysical survey along the tolofonas eratini coastline soon after the earthquake revealed the existence of two major sediment failures affecting the surficial 8 and 2 m of the recent sedimentary cover the sizes of the two sediment failures are approximately 200 000 and 50 000 m 2 the geotechnical study has shown that 1 the coastal sediments are stable under gravitational stresses and cyclic loading stresses induced by the 6 2 r earthquake and 2 the sediment failures were initiated due to liquefaction of subsurface layers the failed sediments very quickly disintegrated and transformed to mass flows the deformation of the failed sediment was caused by loss of sediment strength due to development of high pore water pressure induced by the earthquake the study suggests that the alluvial fan deposits along the coastal zone of the western corinth gulf are susceptible to liquefaction by any earthquake event with a magnitude greater than 6 r depending upon the proximity of the site to the earthquake epicenter earthquakes of magnitude 6 r are expected to occur every 22 7 years and therefore the recurrence interval for sediment failure events is about the same

package fluids 1 computer programs for analysis of fluid inclusion data and for modelling bulk fluid properties the computer package fluids contains five sets of computer programs written in c for the calculation of fluid properties both model fluids and data from fluid inclusions can be analysed in the programs bulk density molar volume and composition of fluid inclusions are calculated with the program bulk which uses microthermometric data micro raman spectroscopic data cation ratios and volume fraction estimations as input the program offers a broad variety of equations of state which are selected according to the fluid system or the temperature and pressure conditions of interest the isochores that correspond to the output or test v x properties of fluid inclusions are calculated by the program isoc in calculating the isochores this program takes account of the compressibility and expansion of selected host minerals the program test allows different equations of state to be compared directly with experimental data thereby facilitating selection of the most adequate model in the programs bulk and isoc loner is a group of programs that handle individual equations of state eos for all fluid systems presented in the programs bulk and isoc aqso is a group of programs that allows purely empirical modelling of electrolyte bearing aqueous solutions henry s law for dilute gas bearing aqueous solutions and osmotic coefficients for dilute electrolyte bearing aqueous solutions the programs are available on the university of leoben web site at http www unileoben ac at buero62 minpet ronald

tsunami sources in the southern california bight 1 locally generated tsunamis due to faulting or slope failures offshore southern california threaten nearby coastal cities disruption of operations at port facilities due to tsunami attack could severely impact the regional and national economies this study examines three faults and two landslides scenarios as potential tsunami sources computed runup ranges from 0 5 to 6 m depending on the source and location bathymetric features such as the broad san pedro shelf are shown to contribute to tsunami wave focusing while retarding tsunami arrival times suggesting the usefulness of an early warning system

crustal thickening and attenuation as revealed by regional fold interference patterns ciudad rodrigo basement area salamanca spain abstract the structure of the ciudad rodrigo area iberian massif central iberian zone has been revisited in order to integrate new geological data with recent models of the evolution of the iberian massif detailed mapping of fold structures along with a compilation of field data have been used to constrain the geometry and relative timing of ductile deformation events in this section of the hinterland of the variscan belt the structural evolution shows in the first place the development of a regional train of overturned folds with associated axial planar foliation d 1 towards the lower structural levels the deflection of the fold limbs and a subhorizontal crenulation cleavage depict the upper structural boundary of a superimposed low angle shear zone d 2 which extends at least to the deepest parts of the basement exposed in the study area the amplification and rotation of d 1 folds about a horizontal axis also occurred within this shear zone the flat lying character of the d 2 structures accounts for the attenuation of the previously thickened crust which developed following gravity gradients during thermal re equilibration subsequent deformation led to the formation of two orthogonal sets of upright folds d 3 representing a new shift between crustal thinning and crustal thickening in the region

determination of groundwater flow through regimes of shallow lakes and wetlands from numerical analysis of stable isotope and chloride tracer distribution patterns a numerical model previously developed to systematically examine groundwater flow in vertical section near shallow surface water bodies such as lakes wetlands and ponds is further developed to include simulation of the distribution patterns of hydrogeochemical and stable isotopic tracers in relation to the surface water body and the geometry of distribution patterns of the tracers in the groundwater release zone of the lake many different possible flow regimes are identified however in this paper attention is focused on flow through water bodies as these are the flow regimes observed in field validation two shallow lakes on the swan coastal plain of south west western australia are the subject of field studies where hydrogeochemical and stable isotopes are used to validate the flow through groundwater flow regime predicted by the modelling confirming the validity of the approach the flow regime transition diagrams introduced in earlier papers are extended to include consideration of the hydrogeochemical and stable isotopic indices cl l cl and 1000 l 1000 these ratios are introduced as an additional two of nine non dimensional ratios that are necessary to analyse the problem the ratios represent the chloride and isotopic composition ci l and l respectively in the groundwater release zones of the lakes relative to these parameters in the groundwater capture zone cl and for the lake field data from the case studies plotted on appropriately configured transition diagrams demonstrates the overall validity of the modelling approach and its underlying assumptions it is concluded that isotopic and hydrogeochemical data are invaluable in interpreting the interaction between lakes or wetlands and regional aquifers as it is very difficult to make physical or hydraulic measurements in the field that allow an understanding of lake aquifer interaction the tools and concepts developed that are summarized in the presented transition diagrams are invaluable starting points for the consideration and analysis of other case specific examples of groundwater surface water interaction and will improve the scientific basis of decision making concerning lake and wetland management and groundwater interaction by water resource and environmental managers

active faulting within the offshore western gulf of corinth greece implications for models of continental rift deformation discrimination between different lithospheric extension models focusing on the roles of low angle vs high angle faulting and how strain is distributed requires high fidelity imaging of brittle deformation high resolution seismic reflection and multibeam bathymetric data in the western gulf of corinth continental rift were collected to establish the contribution of offshore faults to extension onshore fault slip here is significantly less than expected from geodetic strain rates the rift at this location is a half graben tilted to the north by s dipping faults within the uppermost crust a basement horst on the northern margin is uplifted by the north and south eratini faults and the axial channel is fault controlled subsided lowstand shorelines in the hanging wall of the north eratini and the well studied aigion fault suggest that the faults have similar displacements summed extension from the four major faults across this part of the rift eliki subchannel south eratini north eratini is 8 16 mm yr thereby reconciling geologic and geodetic data sets distributed deformation across isolated multiple faults can model this part of the rift without recourse to and potentially incompatible with an underlying low angle detachment

tsunamis observed in greece and the surrounding area from antiquity up to the present times abstract a new and improved catalogue of tsunamis observed in greece and the surrounding area from antiquity up to the present time is presented reliable information derived from previous catalogues as well as original historical information which has not been previously taken into account has been used as data source as far as the associated earthquakes are concerned some recent and reliable seismological catalogues have been used as data sources the main cause of the generation of tsunamis is the shallow seismic activity that occurs along the hellenic arc as well as in the internal seismic zone of the aegean area the statistics for tsunamis indicate that the tsunami hazard is low considering the area in question as a whole ten distinct coastal regions in which this hazard can be suggested as medium or high have been defined

scaling properties within the gulf of corinth greece comparison between offshore and onshore active faults abstract the gulf of corinth greece is a 110 km long by 30 km wide active graben displaying strong seismicity hosted both on north and south dipping normal faults this complex fault pattern consists of two fault populations offshore and onshore the offshore fault population is investigated by densely arranged seismic reflection profiles during the last 20 years whereas the onshore fault population displays spectacular and well exposed faults delineated by high accuracy mapping we analyzed fault length and throw in order to study the scaling properties of 136 well determined offshore and onshore faults and the comparison between the two datasets we examined the statistical properties on both fault populations in order to describe the role of segmentation in the growth of faults and the different stages of the evolution of the fault networks our results on power law relationships associated with the scaling properties of the fault zones in the gulf of corinth suggest that both fault populations are bi fractal providing the initiation of a sature state in deformation in addition the vertical throw of faults shows that both fault populations have similar properties but different distributions below and above 5 km respectively displacement length ratios show that faults larger than 9 km appear to accumulate throw without any dramatic change to their length these observations combined with other geophysical studies within the gulf suggest that the characteristic fault lengths of 5 km and 9 km can be correlated to the crustal mechanical structure and the seismicity of the gulf

granite magma formation transport and emplacement in the earth s crust the origin of granites was once a question solely for petrologists and geochemists but in recent years a consensus has emerged that recognizes the essential role of deformation in the segregation transport and emplacement of silica rich melts in the continental crust accepted petrological models are being questioned either because they require unrealistic rheological behaviours of rocks and magmas or because they do not satisfactorily explain the available structural or geophysical data provided flow is continuous mechanical considerations suggest that far from being geologically sluggish granite magmatism is a rapid dynamic process operating at timescales of or 100 000 years irrespective of tectonic setting

chemical evolution of groundwater near a sinkhole lake northern florida 1 flow patterns age of groundwater and influence of lake water leakage leakage from sinkhole lakes significantly influences recharge to the upper floridan aquifer in poorly confined sediments in northern florida environmental isotopes oxygen 18 deuterium and tritium chlorofluorocarbons cfcs cfc 11 ccl3f cfc 12 ccl2f2 and cfc 113 c2cl3f3 and solute tracers were used to investigate groundwater flow patterns near lake barco a seepage lake in a mantled karst setting in northern florida stable isotope data indicated that the groundwater downgradient from the lake contained 11 67 lake water leakage with a limit of detection of lake water in groundwater of 4 3 the mixing fractions of lake water leakage which passed through organic rich sediments in the lake bottom were directly proportional to the observed methane concentrations and increased with depth in the groundwater flow system in aerobic groundwater upgradient from lake barco cfc modeled recharge dates ranged from 1987 near the water table to the mid 1970s for water collected at a depth of 30 m below the water table cfc modeled recharge dates based on cfc 12 for anaerobic groundwater downgradient from the lake ranged from the late 1950s to the mid 1970s and were consistent with tritium data cfc modeled recharge dates based on cfc 11 indicated preferential microbial degradation in anoxic waters vertical hydraulic conductivities calculated using cfc 12 modeled recharge dates and darcy s law were 0 17 0 033 and 0 019 m d for the surficial aquifer intermediate confining unit and lake sediments respectively these conductivities agreed closely with those used in the calibration of a three dimensional groundwater flow model for transient and steady state flow conditions

iberian late variscan granitoids some considerations on crustal sources and the significance of mantle extraction ages a suite of post tectonic granitoids mostly peraluminous broadly i type granodiorites and monzogranites and mafic rocks from nwiberia with crystallization ages between ca 309 and 290 ma has been investigated for sm nd isotopes and inherited zircon content in order to constrain the nature of their source rocks end values at 300 ma vary from 0 2 to 5 9 and tdm values range from 1 01 to 1 58 ga inherited xenocrystic zircons yielded ages ranging from 458 to 676 ma with 90 of data between 490 and 646 ma corresponding to neoproterozoic mostly ediacaran cambrian andordovician ages only three highlydiscordant analyses yielded ages older than 650 ma based on the data reported herein and relevant data fromthe literaturewe contend that post tectonic granitoids of the iberian variscan belt with exception of the scarce anatectic s type granitoids were derived mostly from metaigneous lower crustal sources which in turn were ultimately derived from a subcontinental lithospheric mantle enriched between ca 0 9 and 1 1 ga i type granitoids and mantle derived mafic rocks both underwent varying degrees of contamination by ametasedimentary lower crust depleted in pre 650 ma zircon through previousmelting episodes with a time integrated sm nd evolution different to that of the metaigneous lower crust participation of this metasedimentary crust in the genesis of these granitoids may account for nd isotopic variability and nd model ages well in excess of 1 2 ga

magnetic resonance sounding evidence shows that shallow groundwater discharge maintains the lake landscape in the hunshandake sandy land north china the hunshandake sandy land hsl is a well known water rich sandy region in china that is home to many lakes most of these lakes are sustained by groundwater inflow however due to the limited hydrogeological survey data the mechanism by which the lakes interact with groundwater is not well understood magnetic resonance sounding mrs is a geophysical method that has emerged in recent years that can directly detect the distribution of groundwater and determine the lithology of the aquifer medium compared with drilling this method is convenient rapid and inexpensive in this study to determine how the lakes are recharged by groundwater a field experiment using mrs was conducted on haoletuyin lake which is located in the central hsl the results showed that compared with borehole data the mrs derived aquifer depth has an uncertainty of 6 88 additionally the lithology of the media derived from the mrs is consistent with that derived from the borehole data this finding suggests that the mrs derived results are highly accurate based on the mrs derived results two hydrogeological profiles were plotted and they show that the lake in the experimental area is recharged primarily by shallow groundwater and not by deep groundwater this study is significant because it not only reveals the mechanism by which haoletuyin lake is maintained but also proves that mrs is an excellent tool for studying lake groundwater relations in desert sandy land regions with limited hydrogeological survey data

hydrogeochemistry and isotope techniques to determine water interactions in groundwater dependent shallow lakes wet pampa plain argentina this paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater dependent shallow lakes in the southeastern pampa plain of argentina water samples lakes streams spring water and groundwater for hydrochemical and stable isotopic determination were collected and the main physical chemical parameters were measured the combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin the hydrochemical processes which explain los padres lake water chemistry are evaporation from groundwater co2 input calcite dissolution na release by ca2 and mg2 exchange and sulfate reduction the model that best aligns with la brava lake hydrochemical constraints includes mixing co2 and calcite dissolution cationic exchange with na release and mg2 adsorption and to a lesser extent ca na exchange this model suggests that the fractured aquifer contribution to this water body is greater than 50 an isotopic specific fingerprint for each lake was identified finding a higher evaporation rate for la brava lake compared to los padres lake isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer becoming areas of high groundwater vulnerability the tandilia range system considered in many hydrogeological studies as the impermeable bedrock of the pampean aquifer acts as a fissured aquifer in this area contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition

the 1956 earthquake and tsunami in amorgos greece summary we conduct a comprehensive study of the amorgos greece earthquake and tsunami of 1956 july 09 the largest such event in the aegean sea in the 20th century systematic relocation of the main shock and 34 associated events defines a rupture area measuring 75 40 km the use of the preliminary determination of focal mechanism algorithm resolves the longstanding controversy about the focal geometry of the event yielding a normal faulting mechanism along a plane dipping to the southeast which expresses extensional tectonics in the back arc behind the hellenic subduction zone the seismic moment of 3 9 10 27 dyn cm is the largest measured in the past 100 yr in the mediterranean basin a quantitative database of 68 values of tsunami run up was built through the systematic interview over the past 5 yr of elderly eyewitness residents of 16 aegean islands and the turkish coast of asia minor it confirms values of up to 20 m on the southern coast of amorgos 10 m on astypalaia and up to 14 m on the western coast of folegandros 80 km to the west of the epicentre these values largely in excess of the inferred seismic slip at the source and their concentration along isolated segments of fault are incompatible with the generation of the tsunami by the seismic dislocation and require an ancillary source in the form of a series of landslides triggered by the earthquake and or its main aftershocks a model confirmed by hydrodynamic simulations using both the dislocation source and models of landslide sources

submarine and coastal sediment failure triggered by the 1995 ms 6 1 r aegion earthquake gulf of corinth greece on june 15th 1995 a locally destructive earthquake of magnitude ms 6 1 on the richter scale occurred offshore 7 5 km nne of the town of aegion in the western gulf of corinth greece an offshore survey using 3 5 khz subbottom profiling system and a remote operated vehicle rov has shown that the earthquake caused small sized subaerial to submarine sediment failure in at least four sites in three fan delta deposits the rododafni the eliki and the tolofonas the fan deltas were located within a radius of about 9 km from the epicentre the areal size of the four sediment failure sites ranged from 2 104 m2 to 6 105 m2 whilst the volume of the failed masses ranged from 4 103 to 3 106 m3 the sediment deformation types identified at the failure sites consist of ground cracking rotational slides elongated slides sediment gravity flows and extrusion of mixtures of water and sand sand boils the sediment failure in the four sites affected the upper 5 6 m of well layered holocene topset and foreset fan delta deposits the failure occurred on slopes ranging from 0 2 to 23 and the slip planes were all bedding planes which have a gradient from 0 2 to 21 the dominant instability mechanism that caused the sediment failure in the rododafni and eliki fan deltas is considered to be liquefaction of a shallow sub surface horizon the liquefaction was caused by elevated pore pressure enhanced perhaps by the presence of gas resulting from the cyclic loading induced by the earthquake the liquefied layer is assumed to have temporarily provided a failure surface for sliding to take place on and caused movement of sand that was ejected onto the surface in the tolofonas fan delta the causative mechanism in the case of the multi block rotational slide is considered to be deformation of the underlying sediments caused by remoulding and or liquefaction while in the case of the elongated slide it is considered to be the result of a combination of shear stress increase and or strength degradation of the unconsolidated sediment both of these conditions could have been generated during the cyclic loading resulting from the aegion earthquake the study of historical documents reveals that sediment failure like those described above have also occurred at least four times during the past 2500 years in the same locations therefore it is suggested that they could be repeated in the future by any earthquake event with a magnitude greater than 6 r depending upon the proximity of the site to the earthquake epicentre

u pb zircon and monazite geochronology of post collisional hercynian granitoids from the central iberian zone northern portugal abstract in the central iberian zone ciz of the iberian massif large volumes of granitoids were emplaced during the post collisional stage of the hercynian orogeny syn to post d3 the last ductile deformation phase twelve granitic units and a quartz monzodiorite were selected for a u pb zircon and monazite geochronological study they represent successive stages of the d3 event the ucanha vilar lamego sameiro and refoios do lima plutons are coeval 313 2 ma 319 4 ma 316 2 ma and 314 2 ma respectively and belong to the earliest stage later on the braga massif was emplaced its different units yielding the same age 309 3 ma for the braga granite 309 1 ma for the gonca granite and 311 5 ma for a related quartz monzodiorite the braga massif is subcontemporaneous with the agrela and celeiros plutons 307 3 5 ma and 306 2 ma respectively in agreement with field data the briteiros granite is younger 300 1 ma followed by the emplacement of the peneda geres massif geres paufito illa and carris granites the geres granite emplaced at 296 2 ma seems to represent a first magmatic pulse immediately followed by the intrusion of the paufito granite at 290 2 5 ma for the carris granite a minimum emplacement age of 280 5 ma was obtained based on these results the following chronology is proposed 1 syn d3 biotite granitoids 313 319 ma 2 late d3 biotite dominant granitoids 306 311 ma 3 late to post d3 granitoids ca 300 ma 4 post d3 granitoids 290 296 ma these chronological data indicate that successive granitic intrusions were emplaced in the ciz during a short time span of about 30 ma that corresponds to the latest stages of the hercynian orogeny a rapid and drastic change occurred at about 300 ma between a compressive ductile tectonic regime d3 ca 300 320 ma associated to calc alkaline monzonitic and aluminopotassic plutonism and a fragile phase of deformation d4 which controlled the emplacement of the subalkaline ferro potassic plutonism at 290 296 ma

surface water groundwater interaction near shallow circular lakes flow geometry in three dimensions steady flow regimes for three dimensional lake aquifer systems are studied via idealized mathematical models that are extensions of earlier simplified vertical section models of interaction between shallow lakes and underlying aquifers the present models apply to a shallow circular lake at the surface of a rectangular aquifer of finite depth yielding a truly three dimensional representation of the resulting flow system flux boundary conditions are applied at the ends of the aquifer with net vertical recharge or evapotranspiration at the water table the lake is defined by a region with constant head by determining and visualizing solutions to the discretized saturated flow equations a range of possible flow regimes is identified and their topological properties are studied tools for analyzing flow regimes are described including a method for locating and mapping three dimensional dividing surfaces within steady flow fields results show strong similarities between two and three dimensional systems including a large number of flow through recharge and discharge regimes and reverse flow cells flow lines calculated on a vertical plane through the middle of a lake resemble but are not identical to two dimensional streamlines for a range of aquifer flow and recharge conditions estimates of the widths and depths of capture and release zones for various lake aquifer geometries are asymptotic to earlier results for two dimensional systems numerical predictions are compared with analytical results for certain limiting flow regimes

sediment transport processes on an active submarine fault escarpment gulf of corinth greece abstract sediment transport processes on the escarpment of a listric fault in the tectonically active and terrigenous sediment dominated corinth graben in greece are studied using 3 5 khz and airgun profiles and sidescan sonar images the whole of the slope area is affected by gravitational mass movements slumps debris mud flows and liquified and turbidity flows in canyon fan systems large volumes of sediment are transported through slumping debris mud and turbidity flows into the basin here they build coalescing fans which consist of intercalations of debris flow deposits and turbidites in delta front slope fan apron systems sediments are transported radially downslope through slumping debris mud flows liquified flows and high density turbidity flows into the basin where they build coalescing fan aprons these consist of massive homogenized deposits fluxoturbidites in shelf slope systems retrogressive rotational slumping is the dominant instability feature however due to the sharp increase in the slope gradient caused by the slumping debris and turbidity flows are triggered the major factors responsible for triggering gravitational mass movements in the region are earthquakes high sedimentation rates off the river mouths and heavy rainfalls and high seas these mass movements appear to occur at least once every 2 yrs as indicated by the failure of submarine cables

magnitude versus faults surface parameters quantitative relationships from the aegean region historical and seismotectonic data from the broader aegean region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re evaluated all events associated to co seismic surface faulting have been selected and further investigated while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these morphogenic earthquakes sensu bull inqua 16 1993 24 in particular in order to perform seismic hazard analyses we compiled a list of all earthquakes where the surface rupture length srl the maximum vertical displacement mvd or the average displacement ad is available we thus obtained reliable values of these source parameters for 36 earthquakes of which 26 occurred during the 20th century 6 in the 19th century and the 3 remaining earlier magnitude versus srl and mvd has been compiled for estimating empirical relationships the calculated regression equations are ms 0 90 log srl 5 48 and ms 0 5 9log mvd 6 75 showing good correlation coefficients equal to 0 84 and 0 82 respectively co seismic fault rupture lengths and especially maximum displacements in the aegean region have systematically lower values than the same parameters worldwide but are similar to those of the eastern mediterranean middle east region the envelopes of our diagrams are also calculated and discussed for estimating the worst case scenario furthermore for all investigated seismogenic structures based on several geological criteria we measured the geological fault length gfl which is the total length of the neotectonic faults showing cumulative recent activity we then compared srl with gfl and their ratio shows a clear bimodal distribution with a major peak at 0 8 1 0 indicating that about 50 of the investigated earthquakes ruptured almost the entire fault length while a second peak around the value of 0 5 is clearly related to a segmentation process of longer neotectonic structures further implications of this distribution are also discussed eventually from the distribution of gfl versus magnitude we also infer an important geological threshold for the occurrence of morphogenic earthquakes at about 5 5 degrees

fluid rock interactions and the role of late hercynian aplite intrusion in the genesis of the castromil gold deposit northern portugal abstract castromil northern portugal is one of several important orogenic gold deposits located within the central iberian geotectonic zone of northwest iberia the deposit occurs at the margin of a variscan syn to late d3 biotite granite and is spatially associated with a small tourmaline aplite body that intrudes the granite at its contact with a secondary anticline of palaeozoic arenaceous and argillaceous metasediments of the valongo belt identification of the ore fluids and their pathways and the reconstruction of the p t x conditions during mineralisation were obtained by combining the geometric characteristics of veins and microstructures together with a detailed study of the inclusion fluids several stages of fluid percolation following contact metamorphism can be recognised at each stage the contact zone characterised by intrusive aplites related faults and fractures appears to have focused the hydrothermal flow and acted as a structural conduit for deeper sourced hydrothermal fluids the earliest fluid stage stage i is characterised by aqueous carbonic fluids dominated by co2 and ch4 that were probably generated by high temperature fluid rock interaction 400 500 c with graphitic schists interbedded with the metasediments these fluids were responsible for significant alteration greisenisation of the aplite and its host granite and the formation of silicified flat lying structures that can be traced along the strike length of the deposit at temperatures between 400 and 500 c fluid pressure ranges from 230 to 300 mpa which is equivalent to a depth of 10 1 5 km the second stage of mineralisation stage ii as ore stage is also characterised by aqueous carbonic fluids and represents the main phase of quartz arsenopyrite pyrite deposition the third stage of mineralisation stage iii au ore stage was accompanied by intense microfracturing of the preexisting quartz veins and the preferential deposition of gold along microfractures in the sulphides the introduction of gold corresponds to the percolation and mixing of two distinctive aqueous fluids of contrasting salinity at relatively low temperatures 150 275 c based on compositional and temperature data it is suggested that during the main phase of uplift shallow waters penetrated deep into the basement allowing gold to be leached from potential source rocks most probably the palaeozoic metasediments and deposited in structural and geochemical traps formed during earlier stages of the hydrothermal system the decrease in pressure during the as ore stage corresponds to a significant tectonic uplift around 5 6 km and probably marks the transition from lithostatic to hydrostatic pressure conditions furthermore if uplift had already been initiated during aplite emplacement the prevailing sub isothermal high temperature conditions provide an explanation for the presence of decrepitated aqueous carbonic inclusions in metamorphic quartz lenses and veins in the surrounding metasediments to conclude localised heat flows linked to late hercynian magmatism at deeper structural levels appears to be the main cause of fluid circulation at castromil evidence suggests that contact zones related to faulting along a secondary anticline of the valongo belt controlled both aplite intrusion and subsequent long lived hydrothermal fluid circulation the proposed genetic model differs from orogenic gold deposit models in emphasising the role of late stage aqueous fluids in the development of economic grade 10 15 g t gold ores

sedimentary impacts of recent moderate earthquakes from the shelves to the basin floor in the western gulf of corinth abstract in seismically active areas long term records of large earthquakes are indispensable to constrain reccurence patterns of large earthquakes in the western corinth rift one of the most active areas in europe in terms of seismicity data about ancient earthquakes are still insufficient despite historical records covering the last two millenia and several studies in onshore paleoseimology in this paper we test the use of offshore sediments from the gulf of corinth to identify sediment failures and tsunamis that have been triggered by historical earthquakes two shelves 40 100 m deep one sub basin 180 m and the basin floor 330 m have been sampled by short gravity cores the cores were analyzed in order to identify and characterize event deposits the age control has been provided by 137cs and 210pb activity measurements showing that the cores represent 2 to 4 centuries of sedimentation in each site sandy event deposits are interbeded in the muddy hemipelagic sedimentation the age of event deposits has been compared to the record of historical earthquakes using new and published macroseismic data this comparison shows temporal coincidence of some event deposits and documented earthquakes with a macroseismic intensity vii in the area e g in 1861 ce 1888 ce and 1909 ce in nearshore shallow water settings the record of event deposits does not exactly fit with the historical record of large earthquakes because too few event deposits are present this may be due to the absence of sediment failures or to a lower preservation of the deposits in such settings in the deepest site in the basin floor the correspondence is better a sandy turbidite probably corresponds to each large earthquake since 1850 ce except one aseismic sediment density flow that occurred at the end of the 20th century surprisingly the ms 6 2 june 15 1995 aigion earthquake is only possibly recorded in one nearshore site on the aigion shelf in the form of a tsunami back wash flow deposit this study showed that moderate earthquakes m 5 8 6 5 can significantly impact marine sediments regarding the evaluation of seismic hazard in the area the basin floor is proposed as a promising site for long term paleoseismology in the gulf of corinth while shallower settings need to be considered more carefully

influence of regional setting on the interaction between shallow lakes and aquifers 1 interaction between surface water and groundwater depends on the position of a lake within the regional flow system the approach in this paper is to nest a local scale two dimensional 2 d lake aquifer model within a 1 d regional aquifer model to examine the effect of the regional setting on surface water groundwater interaction this extends previous steady state flow modeling which is presented in earlier publications the results indicate that the type of regional setting and position of the lake within that setting impose constraints on the near field flow geometry only nine of 39 previously identified flow regimes are possible in the regional flow system considered flow through lakes are dominant and can occur anywhere within the regional flow recharge and discharge lakes are more likely to occur near the groundwater divide where regional hydraulic gradients are flattest and can be counteracted by local forcing in and near the lake

identification of fluid inclusions in relation to their host microstructural domains in quartz by cathodoluminescence abstract the geometry of fluid trapping in relation to microfracture healing or filling was investigated using massive quartz vein samples characterized by multistage deformation and fluid trapping the multidisciplinary approach used in this study includes 1 mapping of oriented thin sections of quartz using the cathodoluminescence cl mode of a scanning electron microscope sem sem cl images display areas of different intensities from dark to white which correspond to the intensity of the cl and are caused by trace elements present in the quartz microfracture healing by newly formed quartz crystallization may occur under physical chemical conditions different from those which characterized the early quartz matrix formation thus evidences of linear cathodoluminescent markers have been searched and identified by paralleling sem cl images and transmitted light microphotographs data show that cathodoluminescence makes clearly visible the healed crack networks which are only detected in part by transmitted light microscopy the technique is essential to establish the microcrack chronology and to estimate the width affected by healing along a fluid inclusion trail such data are useful for the estimation of the microfracture permeability changes throughout the history of fluid migration 2 systematic and statistical analysis of the microstructural markers in horizontal and oriented planes using an interactive videographic analyzer which gives the geometry of the paleofluid pathways orientation dip and width of the veinlets fluid inclusion trails and cathodoluminescent microdomains 3 microthermometric and raman analyses of fluid inclusions in selected fluid inclusions for the determination of the p v t x conditions of fluid migration in a specific microcrack network studied quartz samples come from au mineralized quartz veins from the french massif central and some quartz samples from the cassiar mountains in british columbia have been observed for comparison in all samples the quartz matrix exhibits intense microfracturing suggesting strong brittle deformation which postdates the main stage of quartz lens formation the quartz veins are characterized by multistage quartz crystallization healed microfractures clear quartz bands as well as quartz comb veinlets were studied as functions of the physicochemical conditions in relation to stages of deformation and ore deposition this study shows that systematic measurements of microstructural marker orientations together with detailed fluid inclusion and mineral petrography and microthermometry may lead to a precise determination of ore fluid pathways and chronology

estimating groundwater exchange with lakes 2 calibration of a three dimensional solute transport model to a stable isotope plume a three dimensional groundwater flow and solute transport model was calibrated to a plume of water described by measurements of 18o and used to calculate groundwater inflow and outflow rates at a lake in northern wisconsin the flow model was calibrated to observed hydraulic gradients and estimated recharge rates calibration of the solute transport submodel to the configuration of a stable isotope 18o plume in the contiguous aquifer on the downgradient side of the lake provides additional data to constrain the model a good match between observed and simulated temporal variations in plume configuration indicates that the model closely simulated the dynamics of the real system the model provides information on natural variations of rates of groundwater inflow lake water outflow and recharge to the water table inflow and outflow estimates compare favorably with estimates derived by the isotope mass balance method krabbenhoft et al this issue model simulations agree with field observations that show groundwater inflow rates are more sensitive to seasonal variations in recharge than outflow

local tsunamis and distributed slip at the source variations in the local tsunami wave field are examined in relation to heterogeneous slip distributions that are characteristic of many shallow subduction zone earthquakes assumptions inherent in calculating the coseismic vertical displacement field that defines the initial condition for tsunami propagation are examined by comparing the seafloor displacement from uniform slip to that from an ideal static crack we demonstrate that dip directed slip variations significantly affect the initial cross sectional wave profile because of the hydrodynamic stability of tsunami wave forms these effects directly impact estimates of maximum runup from the local tsunami in most cases an assumption of uniform slip in the dip direction significantly underestimates the maximum amplitude and leading wave steepness of the local tsunami whereas dip directed slip variations affect the initial wave profile strike directed slip variations result in wavefront parallel changes in amplitude that are largely preserved during propagation from the source region toward shore owing to the effects of refraction tests of discretizing slip distributions indicate that small fault surface elements of dimensions similar to the source depth can acceptably approximate the vertical displacement field in comparison to continuous slip distributions crack models for tsunamis generated by shallow subduction zone earthquakes indicate that a rupture intersecting the free surface results in approximately twice the average slip therefore the observation of higher slip associated with tsunami earthquakes relative to typical subduction zone earthquakes of the same magnitude suggests that tsunami earthquakes involve rupture of the seafloor whereas rupture of deeper subduction zone earthquakes may be imbedded and not reach the seafloor

p t x conditions of late hercynian fluid penetration and the origin of granite hosted gold quartz veins in northwestern iberia a multidisciplinary study of fluid inclusions and their chemistry quartz veins hosted by late hercynian granites and their host rocks occur across the variscides of the northern iberian peninsula and locally display au as mineralization four separate occurrences at corcoesto tomino penedono and pino have been investigated to determine p t x conditions of formation and likely fluid sources special attention has been paid to fluid chemistry using a multidisciplinary investigation of fluid inclusion gases by raman spectroscopy individual fluid inclusion analysis and mass spectrometry bulk analysis and ion chemistry using microthermometry and bulk leachate chemical analysis two major changes in the chemical and physical environment have been identified 1 a progressive change in the bulk chemical composition from early co2 rich c h o n fluids equilibrated with graphitic metamorphic host rocks to late h2o dominated fluids inferred from their halogen signature to result from an influx of meteoric or upper crustal fluids affecting the basement at the end of variscan orogenesis and 2 changes in the p t conditions from early stage sulphide deposition in quartz veins at ca 450 c and 150 300 mpa towards epithermal conditions ca 260 310 c and 75 mpa at the stage of gold mineralization several chemical trends are shown by the fluid inclusions 1 dilution of the early volatile rich fluids 2 a break of graphite buffering activity demonstrated by the ch4 content increase in the volatile fraction of the latest as mineralizing fluids and 3 increasing contribution of a relatively oxidizing fluid enriched in sulphate and bromide during the latest stages of fluid percolation au stage these latest fluid stages are interpreted as indicative of extended fluid penetration downward in the crust enhanced by late brittle deformation and decompression and played an important role in mass transfer at the end of the hercynian orogeny especially in transport of metals gold ores have formed mostly in granites because main fluid pathways developed in the main structurally active zones which favoured the emplacement of the granites however there is no evidence of genetic link between gold ores and their enclosing granites

geodetic estimate of seismic hazard in the gulf of korinthos the recent 15 june 1995 m0 6 0 1018 n m aigion earthquake in the western gulf of korinthos has focussed attention on the seismic hazard of the region although there have been few large earthquakes in the region during this century the historical record suggests that there may have been many large earthquakes there in the interval 1750 1900 we present geodetic data that give estimates of the rate of extension of the gulf of korinthos during this century and which suggest that less than half of the elastic strain in the central and western gulf of korinthos has been released by earthquakes during this century in contrast the seismic and geodetic strains in the eastern gulf of korinthos are in agreement with each other if the discrepancy between seismic and geodetic strains in the western gulf of korinthos that has accumulated during this century is removed in earthquakes the moment release will be equivalent to several ms 6 5 earthquakes

geodetic determination of tectonic deformation in central greece from 1900 to 1988 the global positioning system has been used to measure the relative displacements of fifteen monuments in a hundred year old triangulation network spanning part of the aegean extensional basin these displacements reflect the tectonic deformation of the region over the past century showing more than one metre of north south extension across the network the crust in this region appears to contain a few slowly deforming blocks separated by more rapidly deforming zones

evolution and paragenetic context of low δd hydrothermal fluids from the panasqueira w sn deposit portugal new evidence from microthermometric stable isotope noble gas and halogen analyses of primary fluid inclusions abstract the evolution paragenetic context and origin of remarkably low d hydrothermal fluids from the hercynian panasqueira w sn cu ag deposit have been investigated through a combined microthermometric stable isotope halogen and noble gas fluid inclusion study large variations in d between 60 and 134 have been observed in primary fluid inclusions from growth zones in a quartz crystal pa66 paragenetically constrained to the main sulfide stage mss of ore formation the same fluids exhibited relatively constant fluid inclusion homogenisation temperatures 254 to 260 c salinities 7 4 to 8 7 wt nacl equivalent and calculated fluid 18o 3 8 to 4 4 all the fluids exhibited 40ar excesses mean molar br cl and i cl ratios varied from 2 3 10 3 4 2 10 3 and 8 10 4 10 10 4 respectively with the more br rich fluids being associated with the more deuterium depleted fluids the low palaeolatitude of panasqueira throughout the main stages of ore formation and the overwhelming predominance of meteoric fluids in the main late and post ore mineralising fluids with d of 40 to 65 lends little support for any models involving low d palaeometeoric water the limited range of 40ar cl ratios 1 1 10 5 1 6 10 5 also precludes boiling during the mss or mixing of meteoric water with highly fractionated deuterium depleted magmatic waters as viable mechanisms for producing the low d fluids the high br cl and i cl of the mss fluids indicate significant fluid interactions with organic rich sediments or metasediments in particular regionally abundant carboniferous coals or coaly sediments that are inferred to be depleted in deuterium by around 85 compared to palaeometeoric water the large range of d observed in the mss fluids may be explained by isotopic exchange of palaeometeoric water with these coals at varying water rock wt wt ratios between 0 02 and 0 002 with fluid oxygen isotopic compositions controlled by exchange with the beira schists such a model is consistent with the requirements that any satisfactory model must take into account viz i the relative constancy of temperature salinity 40ar and fluid 18o during excursions to low d ii the high i cl and br cl ratios observed and iii the coincidence of these low d fluids with the onset of precipitation of polymetallic sulfides and phosphates under reducing conditions the model indicates that meta sedimentary sources of ore forming components became increasingly important during the evolution of the panasqueira sn w deposit and accounts in part for the observed progression from oxide dominated to base metal sulfide dominated parageneses

transient hydrogeological controls on the chemistry of a seepage lake a solute mass balance method was used to estimate groundwater inflow and outflow rates for nevins lake michigan a seepage lake in the upper peninsula that historically has shown extremely variable water chemistry compared with most other seepage lakes a 4 year study 1989 1992 of the hydrology and geochemistry of nevins lake and its contiguous groundwater system revealed that changes in the mass of dissolved solutes are the result of annual hydraulic gradient reversals a pronounced acidification of nevins lake from 1986 to 1988 was likely caused by drought induced diminished groundwater inflow rates in this study dissolved calcium the major cation in water of nevins lake groundwater and precipitation was used for estimating mass flow rates during the 1989 1992 period nevins lake showed a reproducible annual cycle in calcium mass immediately following spring snowmelt and the resulting hydraulic gradient reversal the mass of dissolved calcium in the lake increases rapidly and then it decreases steadily throughout the summer and early fall at which time the lake becomes hydraulically mounded and receives no groundwater inflow groundwater flow rates estimated by the solute mass balance method are sensitive to assumed solute concentrations in discharging groundwater pore water samples from the lake bed are shown to be more representative of water discharging to the lake than are samples from piezometers near the lake shore but spatial and temporal variability in pore water chemistry must be considered stable isotope analyses 18o and 2h of lake water groundwater and pore water samples show that water discharging to nevins lake in the spring is entirely recycled lake water and no groundwater derived from terrestrial recharge reaches the lake the conceptual model formulated during this study linking lake chemistry and the contiguous groundwater system and general groundwater flow patterns surrounding highly transient lake systems are likely transferable to other similar systems

the interaction of lakes with variably saturated porous media numerical simulation of variably saturated porous media indicates that groundwater recharge is variable in time and space depending on the thickness of the unsaturated zone through which infiltrating water must move the resulting complex transient groundwater flow systems have significant impact on contiguous surface water in very permeable media small local closed groundwater flow systems can develop and dissipate within a few weeks to several months after major recharge these have a direct effect on contiguous surface water by alternately causing seepage to and seepage from the surface water the transient nature of these flow systems indicates that reversals of the direction of groundwater flow may be common in less permeable media the same complex flow systems may occur but the time for development and dissipation is much greater for example it is conceivable that small local flow systems may exist for many months or years as a result of major recharge therefore directions of flow in such systems are more stable and the effect on contiguous surface water also is more stable the findings of this study indicate that wells and groundwater quality sampling sites need to be carefully located to define accurately water table configuration groundwater recharge direction of seepage through the beds of surface water bodies and complex geochemical processes related to changing directions of groundwater flow

palaeoseismic events recorded in archaean gold quartz vein networks val d or abitibi quebec canada archaean gold quartz vein deposits are commonly hosted in high angle reverse shear zones and are interpreted to have formed in a regime of horizontal compression and high fluid pressure environment this paper presents the results of a combined structural and fluid inclusion study on three gold quartz vein deposits of the val d or area abitibi quebec consisting of subhorizontal extensional veins and e w steeply dipping shear veins crack seal structures tourmaline fibres stretched quartz crystals and open space filling textures indicate that the subhorizontal veins formed by hydraulic fracturing under supralithostatic fluid pressure co2 rich and h2o nacl fluid inclusions interpreted as two coexisting immiscible fluids occur typically in microcracks of different orientations interpreted to have formed in the 1 2 plane horizontal co2 rich fluid inclusion planes are contemporaneous with the opening of these veins 3 vertical vertical h2o nacl fluid inclusion planes as well as some microstructures such as deformed minerals indicate that the same extensional veins have experienced episodic vertical shortening 3 horizontal alternating with the opening events deformation and slip opening also occurred in shear veins in which preferred orientation of fluid inclusion planes is not clear except that the h2o nacl fluid inclusion planes tend to be oriented at high angles to the slip direction the successive opening and collapse events in subhorizontal extensional veins are correlated with deformation and slip opening events in shear veins respectively and are attributed to cyclic fluid pressure fluctuations in the system they are thus consistent with the fault valve model sudden drop in fluid pressure from supralithostatic to lower values induces fluid unmixing and occurs immediately post failure following seismic rupturing along the shear zone sealing of the shear veins allows the fluid pressure to build up again and the subhorizontal extensional veins to form the intermittent change in orientation of 3 in horizontal extensional veins is ascribed to a total shear stress release along the neighbouring shear veins after rupture the complex internal structures of the gold quartz veins provide an excellent record of archaean seismic activity along high angle reverse faults

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

magmatic structures and kinematics emplacement of the variscan granites from central portugal serra da estrela and castro daire areas abstract the late d3 variscan granites which represent the most important volume of granites of central portugal are studied here for their magmatic and solid state fabrics by means of the anisotropy of magnetic susceptibility ams technique in a 5000 km 2 area located between guarda and castro daire including the serra da estrela region two main directions n150e and n20e of stretching lineations are found indicating that the emplacement of these late kinematic granitoids was tectonically controlled a three stage model is proposed in which a openings along n150 striking dextral strike slip faults allow the first granitic magmas to be emplaced in the upper crust of palaeozoic metasediments and syn d3 granitoids b openings along n20 striking possibly sinistral strike slip faults conjugates to the prior strike slip faults and allow the enlargement of the granitic plutons and c the final emplacement of this huge volume of granitic rocks was mainly controlled by the magma pressure which explains the rarity of structures related to this stage of granites emplacement in the country rocks this structural study of granitic rocks yields new constraints on the tectonic evolution of this part of the variscan orogenic belt at c 300 ma

episodic uplift deduced from holocene shorelines in the perachora peninsula corinth area greece four raised shorelines between 1 1 m and 3 5 m have been identified at two localities on the perachora peninsula and were dated by ams 14c to between 6400 and 1500 calibrated years ago uplift movements seem to have occurred in increments of 0 8 0 3 m with a return period of about 1600 years the last uplift coincided with a regional tectonic paroxysm which has already been documented in several areas of the eastern mediterranean the average uplift rate was probably faster during the holocene than the average since the last interglacial period no important vertical displacement occurred in this area at the time of or after the 1981 earthquake but a new episode of coseismic uplift may be in preparation

strong tsunami impact on the bay of aghios nikolaos and its environs nw greece during classical hellenistic times abstract this paper presents for the first time detailed geomorphological sedimentological geoarchaeological geophysical and geochemical evidence of a strong tsunami impact on the bay of aghios nikolaos and its environs nw greece during classical hellenistic times tsunamigenically dislocated beachrock slabs found on top of the santa maura beach ridge complex are closely interrelated to adjacent coarse grained washover fan deposits encountered in vibracores and detected by earth resistivity measurements based on detailed topographic surveys and geomorphometric investigations it was possible to localize areas of high intensity overflow underwater studies revealed that the central and northern parts of the former plaka beach ridge were completely destroyed by tsunami impact loose littoral deposits were flushed into the bay of aghios nikolaos and mega blocks of the underlying beachrock structure were dislocated landwards tsunami landfall occurred all along the eastern and northern shores of the bay where deposits partly weathered and associated to archaeological findings were found runup was estimated to minimum values between 2 3 m and 4 6 m a s l crosschecking the results of radiocarbon analyses with archaeological ages from five sites allowed to date the strong tsunami event to the time period between 395 cal bc and 247 cal bc due to the funnel like contour of the coastline the area is extremely sensitive to tsunami events of mid to high magnitude and high frequency

nitrogen isotope compositions of metasedimentary rocks in the catalina schist california implications for metamorphic devolatilization history abstract in the catalina schist subduction zone metamorphic complex california metasedimentary rocks show a decrease in n concentration and an increase in 15nair with increasing metamorphic grade lowest grade lawsonite albite rocks contain 632 185 ppm n with 15 n 1 9 0 6 whereas highgrade amphibolite equivalents contain 138 76 ppm n with 15 n 4 3 0 8 loss of n accompanied devolatilization reactions that evolved h2o rich c o h s n fluids through consumption of chlorite and phengitic white mica and production of mineral assemblages containing muscovite biotite garnet and kyanite whole rock n concentrations of up to 200 ppm in veins and pegmatites produced during high p t metamorphism reflect the redistribution of n during devolatilization and partial melting of the metasedimentary rocks bulk fluid rock n isotope fractionations 15n 15nfluid 15nrock of 1 5 1 were calculated with the rayleigh distillation equation taking into account variability in rock composition by comparison of samples with similar k2o concentrations these fractionations are similar to but slightly lower than published calculated fractionations for n2 nh4 exchange at the temperature range of 350 600 c over which most of the devolatilization occurred in the catalina schist approximately 3 4 to 2 25 the n systematics appear to be explained by n2 nh4 exchange and a devolatilization process intermediate in behavior to batch volatilization and rayleigh distillation the observed shifts in n concentration and 15n cannot be explained by nh3 nh4 exchange at these temperatures using the equilibrium models the distillation devolatilization process implicated in this study may govern the behavior of other trace elements partitioned into hydrous fluids during devolatilization e g b cs u similarity of the calculated fluid 15n 1 5 to 5 5 with compositions of natural gases inferred to be derived from metasedimentary sources indicates the possibility of using n as a tracer of large scale volatile transport

characterization and timing of the different types of fluids present in the barren and ore veins of the w sn deposit of panasqueira central portugal the panasqueira w sn deposit is the largest quartz vein type deposit of the iberian peninsula and the most important wolframite deposit in western europe the ore veins are almost exclusively sub horizontal besides ore bearing sub horizontal veins the panasqueira mine also contains barren quartz veins there are essentially two generations of barren quartz quartz contemporaneous with the earliest regional metamorphism qi and recrystallized quartz contemporaneous with the thermal metamorphism related to the granite intrusion qii fluid inclusion studies microthermometry and raman were undertaken in order to distinguish fluids contemporaneous with the barren quartz from those contemporaneous with the ore bearing quartz qiii fluid inclusion data indicate that the barren and ore bearing quartz fluids are dominantly aqueous 93 to 98 mol h2o with a nearly constant bulk salinity 8 to 12 wt eq nacl with the quantity of volatile component determined by raman spectrometry higher in qiii but never greater than 5 mol however the co2 ch4 n2 ratio is different for each type of quartz volatiles are dominated by ch4 10 to 96 mol zch4 and or n2 3 to 87 mol zn2 in the barren quartz and by co2 60 to 73 mol zco2 in ore bearing quartz the bulk chemical composition of the fluids in qiii is comparable to that found commonly in hydrothermal fluids associated with wolframite mineralization where na k ca and hco3 cl so4 a dispersion in th 226 to 350 c found in qiii together with a variation in the degree of filling 0 5 to 0 7 and with the consequent variation of fluid densities 0 70 to 0 79 may result from changes in the fluid pressure regime below lithostatic pressure suggesting vein filling related to tectonic events

textural evolution of synthetic fluid inclusions in quartz during reequilibration with applications to tectonic reconstruction experimental reequilibration of synthetic 10 wt nacl h2o inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the p t path followed by the inclusion after formation these differences combined with other geological information may be used to determine whether the sample rock followed a dominantly isothermal or isobaricp t path following entrapment the intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of thep t path from the original isochore for the inclusion thus fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradep t path but also the magnitude of departure of this path from one that is isochoric

tsunami hazard in the marmara sea turkey a numerical approach to discuss active faulting and impact on the istanbul coastal areas abstract the westward propagation of the seismic ruptures along the north anatolian fault naf during the 20th century has increased the probability that the next rupture will be located offshore in the marmara sea in the prolongation of the 1999 izmit earthquake faulting historical tsunamis have been evidenced in the marmara sea e g those associated with the 1509 may 1766 strong earthquakes that broke submarine parts of the naf in the vicinity of istanbul and future submarine events are expected to produce tsunamis as well that could be triggered either by submarine coseismic displacements or by landsliding the assessment of their amplitude and extent of their effects is discussed in this paper through numerical modeling based on both earthquake and landsliding sources we use a finite difference method that yields the maximum water levels reached in the marmara sea and the effects run up values around the coasts of istanbul using a set of three nested bathymetric grids with a decreasing cell size to focus on istanbul first we consider probable earthquake sources along the northern branch of the emerged naf namely in the eastern cinarcik basin magnitude mw 7 2 in the western tekirdag and central basins magnitude mw 7 5 and along the whole branch magnitude mw 7 6 the impact obtained in istanbul is all the more important as a normal component in the eastern basin is present and maximum water levels can reach 2 m along the shoreline provoking locally significant inundations these results show that the historical tsunami observations around istanbul 1509 may 1766 provided they are directly due to earthquake sources imply a significant normal component in the eastern basin whatever the extent of the rupture westward conversely a source located in the western and or central basin does not provoke large waves in istanbul e g august 1766 most probably finally we test three landslide sources in the southern vicinity of istanbul and show that the damage is expected to be larger than in the case of earthquake sources for moderate to large volumes involved this kind of source in addition to the coseismic deformation could therefore be a good candidate to explain the historical waves in istanbul especially in 1509 where run up values as high as 6 m have been reported provided we are confident in the historical documents available

the seismogenic zone of the continental crust in northwest iberia and its relation to crustal structure the distribution of seismicity at the western end of the cantabrian mountain range nw iberia reflecting current crustal dynamics is investigated integrating seismically active structures long term structures and the topographic features at the surface the thickness of the seismogenic zone within the continental crust is established in 20 km two crustal domains can be distinguished in the study area in terms of the seismicity pattern the style of alpine structures and the relief the presence of crustal fluids arises as a very likely contributing factor to the excessive thickness of the seismogenic zone in the study area more importantly a switch in tectonic style at the transition between crustal domains in coincidence with the lateral termination of orogenic frontal thrusts is envisaged as involving sufficient stress heterogeneity and amplification to explain the current concentration and characteristic pattern of historical seismicity in the region overall the distribution of seismicity in the crust is sensitive to the type and style of crustal structures

late holocene coastal depositional environments and climate changes in the gulf of corinth greece multidisciplinary studies in coastal systems of the eastern mediterranean region have proven to be excellent tools in understanding paleoenvironmental paleoecological and paleoclimatic changes th

high pressure and temperatures during the early stages of tungsten deposition at panasqueira revealed by fluid inclusions in topaz the variscan vein type panasqueira w sn cu deposit one of the main tungsten deposits in western europe has a long and complicated geological history the first vein infillings which consist of the quartz wolframite association as well as the first generation of topaz underwent significant deformation as a consequence most fluid inclusions of the earliest hydrothermal event are deformed and destroyed two preserved fluid inclusion assemblages are however found in the topaz overgrowth band and are dense aqueous carbonic inclusions as well as dense co2 dominated fluid inclusions the p t conditions of fluid trapping are constrained by using the intersection between isochores as well as graphite water equilibrium data and yield the following trapping conditions 500 20 c and 250 20 mpa these p t conditions are incompatible with fluid unmixing fluid chemistry results from water graphite equilibrium probably in metapelites at two distinct temperatures around 450 500 c for the predominant aqueous carbonic fluid and higher temperatures of maximal 550 c for the co2 rich fluid enriched in n2 these p t estimates are consistent with deep crustal levels around 8 10 km depth and a high geothermal gradient around c 60 c km 1 the ascending non magmatic fluids enriched in volatiles are essential in the ore genesis the high thermal gradients may be related either to new magma pulse after the formation of the panasqueira granite intrusion or to anomalous heat flux produced by the hot fluids ascending from migmatitic levels present at greater depth this hypothesis necessitates to consider the role of a crustal weakness which is attested both by the successive intrusions of several granitic magmas at the same place and the presence of inherited quartz filled structures so called seixo bravo found only in the panasqueira area

role of fluids in migmatites co2 h2o fluid inclusions in leucosomes from the deep freeze range migmatites terra nova bay antarctica the metasedimentary sequence of the deep freeze range northern victoria land antarctica experienced high t low f metamorphism during the cambro ordovician ross orogeny the reaction bt sil qtz grt crd kfs melt was responsible for the formation of migmatites peak conditions were c 700 750 c c 3 5 5 kbar and xh2oc 0 5 distribution of fluid inclusions is controlled by host rock type 1 co2 h2o fluid inclusions occur only in graphite free leucosomes 2 co2 ch4 h2o fluid inclusions are the most common type in leucosomes and in graphite bearing mesosomes and gneiss and 3 co2 n2 ch4 fluid inclusions are observed only in the gneiss and subordinately in mesosomes co2 h2o mixtures 41 co2 58 h2o 1 nad mol are interpreted as remnants of a synmig matization fluid their composition and density are compatible p t ah2o conditions of migmatization c 750 c c 4 kbar xh2oc 0 5 co2 h2o fluid in graphite free leucosomes cannot originate via partial melting of graphite bearing mesosomes in a closed system this would have produced a mixed co2 ch4 fluid in the leucosomes by a reaction such as bt sil qtz c h2o grt crd kfs l co2 ch4 we conclude that an externally derived oxidizing co2 h2o fluid was present in the middle crust and initiated anatexis high density co2 rich fluid with traces of ch4 characterizes the retrograde evolution of these rocks at high temperatures and support isobaric cooling p t anticlockwise path in unmigmatized gneiss mixed co2 n2 ch4 fluid yields isochores compatible with peak metamorphic conditions c 700 750 c c 4 4 5 kbar they may represent a peak metamorphic fluid that pre dated the migmatization