average seasonal variation of the atlantic equatorial currents from historical ship drifts abstract surface currents in the tropical atlantic were studied using historical ship drift data these are the only available data capable of resolving the long term seasonal fluctuations of currents over a broad geographical region the north equatorial countercurrent was found to extend as a continuous eastward flowing current across the atlantic in the band 5 8 n from july to december the maximum average eastward velocity was 30 cm s 1 during july september east of 20 w the countercurrent continued throughout the year west of 20 w and from january to june the countercurrent disappeared and westward currents were observed average westward velocity reached 20 cm 1 in april and may centered near 40 w the annual cycle in surface velocity 20 cm s 1 amplitude agrees closely with that of geostrophic velocity inferred from variations in thermocline depth across the counter current jets centered near 2 n and 4 s separated by a minimum near 1 s the northern jet has a large 14 cm s 1 semiannual v

the thermal and mineral springs of aitoloakarnania prefecture function mechanism and origin of groundwater the study area is located in the northwestern part of greece in aitoloakarnania prefecture in this region where no volcanic activity exists thermal springs such as kremasta and kokkino stefani well known for their healing properties occur the objective of this study was the investigation of these springs as well as the study of the chemical composition and origin of water relationships between these springs were also examined the geological setting of the area comprises sedimentary rocks of the pindos gavrovo tripolis and ionian geotectonic zones deformed by orogenic movements followed by neogene extensional tectonism the thermal and mineral springs were classified into three main groups the first group is characterized by ca hco3 water type and low water temperatures it corresponds to the springs that are hosted in the ionian zone and their possible enrichment in so4 is mainly attributed to the evaporites the other two groups consist of alkaline thermal water mainly hosted in the formations of gavrovo tripolis zone in these two groups the very strong reducing conditions that prevail are expressed by high amounts of nh3 and h2s moreover na f li sr and ba display elevated concentrations the second includes mineral waters of ca na hco3 type that are depleted in calcium their residence time is rather long and they originate from deep water circulation through siliceous rocks the third group includes thermal waters of ca mg na hco3 water type of higher water temperatures that reveal characteristics of deep circulation directly associated with the underlain limestones

waveform relocation and focal mechanism analysis of an earthquake swarm in trichonis lake western greece abstract in early april 2007 a series of moderate earthquakes m l 4 1 4 8 oc curred in the area of trichonis lake in western greece the earthquake activity waswell recorded by the hellenic broadband seismic network hl operated by the na tional observatory of athens initial locations for 156 events of the swarm showed adiffuse image of seismicity subsequently 101 events are precisely relocated calcu lating source specific station terms and differential travel times from waveform crosscorrelation uncertainties in relocations are estimated with a bootstrap approach byrandomly weighting the original picks and the differential times additionally wave forms of seven out of the eight largest earthquakes of the swarm were inverted inorder to derive regional moment tensor solutions the results showed a tight north northwest south southeast cluster located on an offshore extension of a similarlyoriented fault trace mapped onshore moment tensor solutions indicate normal fault ing with a substantial component of left lateral strike slip motion it is possible thatthis identified fault forms part of a link that connects the gulf of corinth rift system tothe west northwest east southeast fault zone south of trichonis basin online material event catalog and focal mechanism for the eight largest events introduction

microseimicity and strain pattern in northwestern greece during a 7 week microearthquake experiment conducted in epirus akarnania and the ionian islands of western greece we located approximately 600 earthquakes with magnitudes between 2 and 4 2 no event was deeper than 40 km the seismicity cannot be clearly associated with any single fault except the lixourion right lateral fault located west of the ionian islands focal mechanisms of about 100 earthquakes show for a narrow band of earthquakes located along the coast ene wsw shortening consistent with the surface tectonics farther east focal mechanisms show nnw sse extension beneath the foothills of the pindus mountains which is unrelated to surface faulting but is consistent with the presently subsiding basins this strain pattern is seen far north and south of the lixourion fault and is similar to the one observed in the peloponnese it suggests that a large scale mechanism is responsible for the recent geodynamics of both the northwestern and southwestern aegean

mapping climatological seasonal variations of surface currents in the tropical atlantic using ship drifts the seasonal variability of current velocities in the tropical atlantic was studied by grouping ship drift velocity observations into 2 5 boxes and calculating monthly mean velocity values these values were used to calculate and map the annual mean velocity the seasonal variation about the mean the annual and semiannual harmonics and the first two empirical orthogonal functions eofs the seasonal variation is primarily zonal in the equatorial band and in the north equatorial countercurrent necc and primarily alongshore near the coast of south america maxima of seasonal variation of 23 cm s are centered in the necc near 6 n 42 5 w and in the gulf of guinea near 2 n 7 5 w most 80 of the variance in the necc and along the western boundary of the area studied has an annual period most of the variance along the equator in the mid atlantic has a semiannual period over the whole region 49 of the seasonal variance is explained by the annual harmonic and 69 is explained by a combination of the annual and semiannual harmonics the second eof contains 29 of the variance of the data set and shows a simultaneous speeding slowing of the major equatorial currents the south equatorial current sec the north brazil current the necc and the guinea current along their principal axes of variation with a concurrent slowing speeding of the guyana current and the brazil current the pattern of variation resembles a large equatorial gyre centered along 4 n that flows clockwise from may to september and counterclockwise most of the rest of the year the first eof accounts for 35 of the variance and shows a simultaneous speeding slowing of eastward velocity from 5 s to 10 n except in the western sec the western end of the north brazil current and the guinea current the out of phase fluctuations apparent in the western sec near the equator are explained by the slowing and reversal of the south equatorial current near 2 n 40 w between april and june this slowing of the sec is associated with the start up of the necc which accelerates eastward in may june and july and flows eastward across the atlantic from july through december the sec divides seasonally near the eastern tip of brazil where residual alongshore velocities are northward for half the year peaking during may and june and southward for the other half of the year a second division can be seen north of the amazon where the north brazil current continues up the coast into the guyana current during the first half of the year but partially retroflects into the necc during the last half of the year a fast eastward flow in the necc coincides with below average velocities in the guyana current and above average velocities in the western sections of the north brazil current and the sec north of the equator

double celled subtropical gyre in the south atlantic ocean means trends and interannual changes 1 we present here a study of the mean upper layer structure of the south atlantic subtropical gyre sasg and its modes of variability based on archiving validation and interpretation of satellite oceanographic data sea level anomaly data gravity recovery and climate experiment based mean dynamic topography mdt models reynolds sea surface temperatures and two tide gauge time series from permanent service for mean sea level analysis of the mdts shows that the sasg mean structure is represented by a double cell circulation the southern cell being a narrow quasi zonal strip centered around 33 s its southern limb is limited by the recently discovered saint helena current tristan da cunha current sthc tcc and the north subtropical front around 35 s this system is shown to be well separated from the south atlantic current south subtropical front around 42 45 s a method based on singular spectrum analysis was used to determine the principal modes of variability through the decomposition of the data into band passed data sets the altimeter sea level trend analysis suggests that the sasg pattern is slowly migrating southward and has been growing in amplitude between 1994 and 2006 with local growth rates of 5 10 mm yr occurring in the southern cell flow intensifications in this period 2 3 cm s in the south equatorial current and north brazil undercurrent 3 5 cm s in the benguela current and weakening by 4 5 cm s in the sthc tcc are recorded the altimeter derived sea level trend is coherent with the growing phase of a bidecadal oscillation found from both tide gauges

comparison of the implementation of rock engineering system and analytic hierarchy process methods upon landslide susceptibility mapping using gis a case study from the eastern achaia county of peloponnesus greece as landslides are very common in greece causing serious problems to the social and economic welfare of many communities the implementation of a proper hazard analysis system will help the creation of a reliable susceptibility map his will help local communities to define a safe land use and urban development the purpose of this study is to compare the implementation of two semi quantitative landslide assessment approaches using landslide susceptibility maps compiled in a gis environment the compared methods are rock engineering system res and the analytic hierarchy process ahp for the landslide susceptibility analysis the northeastern part of the achaia county was examined this area suffers from many landslides because of its neighborhood with the tectonically active corinthian gulf and its geological setting neogene sediments flysch and other bedrock formations with local overthrusts ten parameters were used in both methodologies and each one was separated into five categories ranging from 0 to 4 representing their specific conditions derived from the investigation of the landslides in the western part of the study area ranking area a layer map was generated for each parameter using gis while the weighting coefficients of each methodology were used for the compilation of res and ahp final maps of the eastern part of the study area validating area by examining these two maps it is revealed that even though both correctly show the landslide status of the second site the res map reveals a better behavior in the spatial distribution of the various landslide susceptibility zones

first paleomagnetic results from mio pliocene series of the hellenic sedimentary arc abstract paleomagnetic measurements have been conducted on the mio pliocene series along the external sedimentary hellenic arc in order to detect the presence or absence of rotational deformations in different sections of the arc in the central eastern part of the arc crete and rhodes paleomagnetic directions are very closely aligned along the north south direction showing that this portion of the arc has not undergone significant rotation since at least 7 m y for crete and 4 m y for rhodes in the western and northwestern parts results from south peloponnesos zakinthos kephallinia and corfu indicate that this section of the arc has undergone a clockwise rotation detailed analysis of the data from the three ionian islands shows that their rotation began about 5 m y b p and has proceeded since then at roughly 5 m y giving a total amplitude of about 26 it is suggested that the beginning of this rotation is related to the lower pliocene compressive phase which most probably initiated the tectonic activity of the present day ionian margin

correlated millennial scale changes in surface hydrography and terrigenous sediment yield inferred from last glacial marine deposits off northeastern brazil abstract the stable isotope composition of planktonic foraminifera correlates with evidence for pulses of terrigenous sediment in a sediment core from the upper continental slope off northeastern brazil stable oxygen isotope records of the planktonic foraminiferal speciesglobigerinoides sacculiferandglobigerinoides ruber pink reveal sub milankovitch changes in sea surface hydrography during the last 85 000 yr warming of the surface water coincided with terrigenous sedimentation pulses that are inferred from high xrf intensities of ti and fe and which suggest humid conditions in northeast brazil these tropical signals correlate with climatic oscillations recorded in greenland ice cores dansgaard oeschger cycles and in sediment cores from the north atlantic heinrich events trade winds may have caused changes in the north brazil current that altered heat and salt flux into the north atlantic thus affecting the growth and decay of the large glacial ice sheets

winds at st peter and st paul rocks during the first sequal year wind observations were obtained during the first nine months of the sequal field program from a station maintained at st peter and st paul spp rocks winds are very steady from may to november and very unsteady during april when the intertropical convergence zone itcz crosses the site wind stress components are computed and comparison with 1979 data shows that the onset of the winds occurred one month earlier in 1983 but is of similar amplitude the spectral analysis of the wind shows a significant increase in the variance for periods between 3 5 days and 10 15 days

quaternary tectonics in the gulf of patras western greece abstract air gun seismic and 3 5 khz profiling data from the gulf of patras western greece show that it is occupied by a small asymmetric graben with several geometric similarities to the larger scale graben in the gulf of corinth to the east major listric faulting characterizes the southern flank of the graben whilst the northern flank represents an associated rollover structure affected by antithetic and synthetic faulting the present phase of subsidence is of holocene age but buried growth faults suggest earlier subsidence in the gulf the average rate of subsidence through the holocene is estimated to be 10 mm year the gulf of patras graben together with the gulf of corinth graben and the megara basin represent a continuous system of wnw ese trending grabens in a broad zone of intense seismicity within the aegean domain individual grabens are offset and are interconnected by ne sw trending fault systems

gas charged sediments in the aegean and ionian seas greece abstract during the last fifteen years marine seismic surveys in the aegean and ionian seas have revealed numerous acoustic anomalies i e acoustic turbid zones gas pockets gas plumes enhanced reflectors columnar disturbances wipe outs and meso to micro morphological features such as pockmarks domes mud volcanoes and elongated depressions these are attributed to the presence of gas in sediment interstices the gas charged sediments are found in pleistocene and present day fjord like environments pleistocene and present day deltaic environments lakes and open sea environments the gas found in the quaternary fjord like and deltaic depositional environments is assumed to be of biogenic origin the gas found in the pre quaternary open sea environments is associated with faulting and salt doming and may therefore be of thermogenic origin although the sediment grain size is favourable for the formation of pockmarks the lack of them is probably due to the high seismicity which characterises these regions

coseismic crustal deformation from microseismicity in the patras area western greece summary the patras area lies in the western part of central greece it is an area characterized by high seismicity and complex neotectonics several devastating earthquakes have occurred in the region since 600 bc contemporary crustal deformation is examined in this area using microearthquake data recorded over a lengthy period during 1983 84 by the patras seismic network principally and to a lesser extent by the volos seismic network the microseismicity 1 8 3 9 ml defines a zone deepening to the ne which justifies a possible extension of the gulf of corinth major graben towards the trikhonis lake to the nw spectra of 108 well located microearthquakes are estimated using p waves obtained by selective windowing designed to include only the p phase seismic moments in the range 0 3 45 7 1012 nm are obtained accompanied by estimates of seismotectonic source parameters including source radii average stress drop and average coseismic slip poor correlation is found between seismic moment and magnitude and the likely reason is the complex nature of the neotectonic regime existing in the area two zones differing in crustal deformation characteristics are observed the corinth trikhonis zone reveals two sets of characteristic faults the first set is represented by microearthquakes showing distinctive and relatively higher seismic moments in conjunction with lower stress drops and seismic slips this set of faults shows greater source radius than the second set and therefore the faults are longer the second set is characterized by an almost constant source radius within the range of uncertainty and a wide range of seismic moments stress drops and seismic slips the rio zone is characterized by low seismic slip stress drop and fault radii with the exception of the locality south of the city of patras where relatively higher seismic slip stress drop and fault radius are observed

intermediate layer water masses in the western tropical atlantic ocean intermediate layer water masses are defined according to temperature salinity relationships derived from conductivity temperature depth ctd observations measured during four 1990 1991 western tropical atlantic experiment westrax hydrographic surveys the intermediate layer bounded by density surfaces of sigma theta 26 00 and 27 65 approximately 150 and 1300 m deep respectively is conveniently divided into upper and lower layers by the relatively low salinity antarctic intermediate water aaiw which is centered at sigma theta 27 25 approximately 700 m deep approximately 60 5 of the region s waters are traced to a southern hemisphere origin indicating the importance of aaiw in the western tropical atlantic s water mass structure the southern source water masses south atlantic central water and aaiw enter the westrax region west of 44 w and between the equator and 9 n as part of the subthermocline north brazil current depending on the season all or part of these southern waters retroflect anticyclonically through the region and flow eastward into the north equatorial undercurrent the primary northern source water mass north atlantic central water enters the northeastern corner of the westrax region as part of a cyclonic branch of the north equatorial current nec and converges with the southern water this meeting produces mixture water masses which make up 45 4 of the region in volume and are predominantly of a southern nature the patterns of the mixture water masses which fill the areas between the source water masses suggest the importance of lateral mixing in this ocean region further some of the mixture water in the upper layer appears to be part of the nec suggesting southern water recirculation in the tropical atlantic gyre a time dependent water mass box model of advective and mixing transports is used to suggest that lateral mixing dominates vertical mixing by a ratio of approximately 10 to 1 typical box model results for the fall winter 1990 1991 period indicate that 13 sv of mixture water masses are produced through mixing a sum of 9 sv and 4 sv from southern and northern source water masses respectively while a net 17 sv of mixture water masses are exported from the region

the continuity of active fault systems in greece summary evidence from geomorphology the distribution of large earthquakes and geodetic measurements suggests that the active faulting in mainland greece and the north aegean sea is concentrated into a small number of discrete linear zones that bound relatively rigid blocks on land the zones are most clearly identified where the faulting is associated with large escarpments particularly in hard footwall rocks the zones can become indistinct and diffuse near their ends sometimes because they enter high unstable topography where landsliding obscures the fault morphology but mostly because the extension rates decrease along strike as a consequence of the relative rotation of the blocks they bound the main graben systems of chalkidiki southern thessaly and the north gulf of evia all seem to connect with the strike slip faulting in the offshore aegean and to die out in the west a configuration related to clockwise rotations in east central greece by contrast the gulf of corinth which is the fastest opening graben system in greece opens more rapidly in the west than the east both these features of the gulf of corinth are consequences of the motion of the south aegean and peloponnese as a single block late pliocene and quaternary geology and geomorphology indicate that the boundaries of the rigid blocks in central greece have changed over that time with faulting migrating into the hanging walls sometimes changing in orientation these changes are probably related to the way faulting in the seismogenic layer adapts to block rotation so as to maintain the general features of a velocity field that is controlled by larger scale effects such as buoyancy forces and the seaward migration of the subducting slab beneath crete the image of greece as a mosaic of rigid blocks whose boundaries change with time is a useful framework for seismic hazard evaluation but we emphasize that some moderate sized earthquakes do occur away from the main fault zones within the relatively rigid blocks and especially near their diffuse ends

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

on the origins of the north brazil current the analysis of the hydrographic data obtained during the nordeste iii neiii survey by the r v almirante saldanha brazilian navy between may 4 and july 12 1986 is reported in this work distributions of geostrophic speeds and transports relative to 1000 m reveal the north brazil current nbc and other major features of the tropical atlantic circulation west of 30 30 w between 4 s and 10 30 s the well developed nbc appears in all analyzed crossisobath sections bordering the brazilian continental slope between 10 s and 5 s transporting an average of 21 sv the velocity core of the nbc is found to be centered at about 100 200 m instead of at the surface as previously thought the central branch of the south equatorial current csec enters the study region at about 5 s 6 s and separates into two portions the northern portion of the csec transports about 15 sv northwestward and north of 5 s it coalesces with the nbc to form a 300 km wide current that transports more than 36 sv equatorward the southern branch of the csec transports 14 sv southwestward until about 9 30 s where it makes a cyclonic turn to the north and merges with northward flow from the southernmost branch of south equatorial current ssec the high salinity signature of waters from the ssec appears in the nbc indicating that it is formed to the south of the study area by contrast historical ship drift and lagrangian drifter observations suggest that the nbc and the brazil current are formed at the bifurcation of the csec this apparent contradiction is explained by the surface ekman drift which obscures the geostrophic flow patterns

energetics of eddy mean flow interactions in the brazil current between 20 s and 36 s the energetics of eddy mean flow interactions in the brazil current bc between 20 s and 36 s are investigated in nineteen transects perpendicular to the 200 m isobath ten years 2000 2009 of output data from the hybrid coordinate ocean model hycom ncoda reanalysis with a spatial resolution of 1 12 5 and five day averages are used the mean kinetic energy mke and eddy kinetic energy eke fields presented the same subsurface spatial pattern but with reduced values the eke increases southward with high values along the bc path and the offshore portion of the jet the values of the barotropic conversion term btc are highest in the surface layers and decreased with depth whereas the values of the baroclinic conversion term bcc and the vertical eddy heat flux vehf are highest in the subsurface despite the vertical thickening of the bc the highest energy conversion rates are confined to the upper 700 m of the water column the energetic analysis showed that the current features mixed instability processes the vertical weighted mean of the btc and bcc presented an oscillatory pattern related to the bathymetry the eddy field accelerates the time mean flow upstream and downstream of bathymetric features and drains energy from the time mean flow over the features the bc is baroclinically unstable south of 28 s and the highest energy conversion rates occur in cabo de sao tome cabo frio and the cone do rio grande

relative sea level changes and regional tectonic evolution of seven coastal areas in nw greece since the mid holocene abstract this study presents relative sea level rsl curves for seven coastal areas in akarnania and the northwestern peloponnese nw greece since the mid holocene rsl fluctuations are deduced from 48 14c ams dated sedimentological sea level markers from 27 vibracores drilled in near coast geological archives as well as from six geoarchaeological sea level indicators of known ages seven palaeo sea level curves including uncertainty bands are reconstructed for a coastal zone spanning a distance of 150 km considerable intra regional differences in sea level evolution exist these differences are mainly due to tectonic reasons in general rsl in northwestern greece has never been higher than today rates of local sea level rise were highest until 5500 5000 cal bc up to 12 3 m ka and lowest during 4000 500 cal bc 0 2 1 4 m ka during the past 2500 or so years rsl has accelerated anew 0 7 2 7 m ka calculating differences between local mean sea level curves provides quantitative information on intra regional differences of tectonic activity the coastal plains of palairos and elis show signs of uplift whereas the mytikas and boukka plains are strongly subsiding compared to other areas of the eastern mediterranean northwestern greece has been subject to significant net long term subsidence regional tectonic events rtes were detected for the time around 4000 2500 500 and 250 cal bc as well as around 250 and 1250 cal ad rtes are characterized by changes of uplift subsidence rates or by the redirection of local tectonic movements the question if some of the rtes were of a supra regional nature is still open from a geodynamic point of view the results presented show that akarnania s southwestern fringe is being downwarped while the tectonic block as a whole is moving towards the southwest strongest subsidence rates are observed for central akarnania at akarnania s fringes subsidence is reduced by the influence of strong uplift of adjacent areas such as around preveza and the northern peloponnese

neotectonic evolution of northwestern continental greece the post miocene sedimentary and structural evolution of nw continental greece changes from west to east

near surface current and temperature variability observed in the equatorial atlantic from drifting buoys we examine data from 23 surface drifters which were deployed between june 1983 and july 1984 at 4 w 1 5 4 s the drifters were equipped with a window shade drogue centered at 15 m depth and in most cases a 117 m long thermistor chain drift data indicate a westward south equatorial current with typical speeds of about 20 cm s 1 south of the equator maximum westward flow of 30 40 cm s 1 occurred in june through september of 1983 and 1984 consistent with climatology near zero westward flow which was significantly weaker than was expected from climatology by about 20 cm s 1 occurred from february to april 1984 this probably represents real interannual variability and may be related to the fact that the equatorial atlantic was warmer than usual in the spring and summer of 1984 energetic variations on time scales of o 1 month and less and space scales of o 100 km and less are ubiquitous in the drift and temperature data kinetic energy levels associated with these variations south of the equator are typically 100 cm2 s 2 with slightly higher values in boreal summer energy levels north of the equator are about 500 cm2 s 2 on the basis of data available only during the boreal summer and fall the sources of this energy include inertia gravity waves instabilities of the general circulation and other phenomena for which there is no simple explanation

a microearthquake study in the gulf of patras region western greece and its seismotectonic interpretation summary the seismicity of the gulf of patras region was monitored from 1983 may to 1984 april by a six station microearthquake network with 30 km aperture over 650 events were located using the revised version of the hypo71 computer program for determining hypocentral locations of these a subset of 73 well located events was identified for detailed study analysis of these 73 events reveals a local pattern of seismicity with two main features firstly a gap in seismicity in the central and western parts of the gulf despite the local presence of active faulting affecting the seabed secondly a zone of high seismicity in the northeast part of the gulf where offshore seismic surveys reveal a zone of intense structural complexity a northeast dipping diffuse zone of seismicity extending to a depth of about 25 km has been identified in the northeastern corner of the gulf centred on the rio antirrio channel between the gulfs of patras and corinth it is postulated that the active faults in the central part of the gulf which are apparently aseismic are linked via a shallow decollement surface under the gulf to a deep wnw ese trending fault zone defining the southern margin of the corinth graben and extending westwards to trichonis lake the dipping zone of seismicity is related to the latter fault zone and aseismic faulting in the gulf of patras is attributed to the shallow surface of decollement into which the faults sole a transfer fault zone trending approximately ne sw is postulated to account for the offset of the corinth and patras grabens

the strain pattern in the western hellenic arc deduced from a microearthquake survey summary than loo0 earthquakes recorded during 7 weeks in 1986 in the peloponnese and surrounding areas show shallow seismicity spread over a wide area bounded by the hellenic trench the highest level in the energy release is for clusters located along the hellenic trench where changes in the morphology are seen a few clusters are also observed as at the intersection between the gulf of corinth and the gulf of patras near the lake trikhonis or between kythira and crete in the peloponnese the shallow earthquakes do not define single faults but are diffusely distributed a higher concentration and a deepening of the foci within the whole crust towards the west seem to reflect a higher strain rate there fault plane solutions exhibit a scattered pattern for earthquakes shallower than 11 km but for earthquakes deeper than 11 km they show some consistency in the orientation of p t and b axes gently dipping nodal planes are seen all over the peloponnese with the conjugate vertical plane striking in various directions and with no consistency in the sense of motion these earthquakes are located between 8 and 18 km deep and could reflect a decoupling between the lower and the upper crust reverse faulting is seen in the gulf of kefallinia and the western peloponnese the p axes trend ne sw to e w normal faulting is seen in the gulf of corinth and in central peloponnese with the t axes trending n s and in the southern peloponnese where the t axes trend nw se the deformation over the western hellenic arc revealed by fault plane solutions of earthquakes with depth between 11 and 40 km appears to be the superposition of two phenomena first throughout the aegean crustal extension with orientation roughly parallel to the trench dominates with crustal shortening and subduction along the aegean arc superimposed on this is a more local effect of the collision between the aegea and apulia which seems to induce horizontal compression roughly perpendicular to the aegean arc west of the peloponnese and epirus the compression due to this decays eastward at a distance comparable with the width of the collision zone the deepening of the brittleductile transition is likely to be due to an increase of the strain field towards the ionian islands

numerical ages of cenozoic biostratigraphic datum levels results of south atlantic leg 73 drilling discussion and reply no abstract available the article discussed appeared in the bulletin v 95 p 863 876

the april 2007 earthquake swarm near lake trichonis and implications for active tectonics in western greece abstract we investigate the properties of the april 2007 earthquake swarm mw 5 2 which occurred at the vicinity of lake trichonis western greece first we relocated the earthquakes using p and s wave arrivals to the stations of the hellenic unified seismic network husn and then we applied moment tensor inversion to regional broad band waveforms to obtain the focal mechanisms of the strongest events of the 2007 swarm the relocated epicentres cluster along the eastern banks of the lake and follow a distinct nnw ese trend the previous strong sequence close to lake trichonis occurred in june december 1975 we applied teleseismic body waveform inversion to obtain the focal mechanism solution of the strongest earthquake of this sequence i e the 31 december 1975 mw 6 0 event our results indicate that a the 31 december 1975 mw 6 0 event was produced by a nw se normal fault dipping to the ne with considerable sinistral strike slip component we relocated its epicentre i using phase data reported to isc and its coordinates are 38 486 n 21 661 e ii using the available macroseismic data and the coordinates of the macroseismic epicentre are 38 49 n 21 63 e close to the strongly affected village of kato makrinou b the earthquakes of the 2007 swarm indicate a nnw sse strike for the activated main structure parallel to the eastern banks of lake trichonis dipping to the ne and characterized by mainly normal faulting occasionally combined with sinistral strike slip component the 2007 earthquake swarm did not rupture the well documented e w striking trichonis normal fault that bounds the southern flank of the lake but on the contrary it is due to rupture of a nw se normal fault that strikes at a 45 angle to the trichonis fault the left lateral component of faulting is mapped for the first time to the north of the gulf of patras which was previously regarded as the boundary for strike slip motions in western greece this result signifies the importance of further investigations to unravel in detail the tectonics of this region

the deglacial history of the western tropical atlantic as inferred from high resolution stable isotope records off northeastern brazil abstract the western south atlantic boundary currents represent a sensitive system within the global thermohaline circulation thc we investigated the impact of deglacial thc changes on the western tropical atlantic studied in six high resolution sediment cores from the upper continental slope of brazil the stratigraphy of the cores is mainly based on 14c ams dating of monospecific foraminiferal samples changes in the upper layer tropical ocean during the deglaciation are inferred from stable oxygen isotope measurements on planktic and benthic foraminifera variations in the 18o residuals are assumed to be mainly temperature related during the oldest and younger dryas cooling periods two major deglacial thc disturbances are reported from north atlantic sediment cores concomitant to the repeated thc slowdown we observe an upper layer warming in the tropical ocean a reduced northward heat export from the tropical areas during these periods weak north brazil current is additionally reflected by low meridional gradients in the stable oxygen records this generally agrees with results from coupled ocean atmosphere models

sea surface temperatures in the equatorial and south atlantic ocean during the last glacial maximum 23 19 ka 1 we used planktic foraminiferal assemblages in 70 sediment cores from the tropical and subtropical south atlantic ocean 10 n 37 s to estimate annual mean sea surface temperatures ssts and seasonality for the last glacial maximum with a modified version of the imbrie kipp transfer function method iktf that takes into account the abundance of rare but temperature sensitive species in contrast to climap project members 1981 the reconstructed ssts indicate cooler glacial ssts in the entire tropical subtropical south atlantic with strongest cooling in the upwelling region off namibia 7 10 c and smallest cooling 1 2 c in the western subtropical gyre in the western atlantic our data support recent temperature estimates from other proxies in the upwelling regions in the eastern atlantic our data conflict with sst reconstructions from alkenones which may be due to an environmental preference of the alkenone producing algae or to an underestimation of foraminiferal ssts due to anomalous high abundances of n pachyderma sinistral

models of strain variation in nappes and thrust sheets a review abstract strain within nappes and thrust sheets can be modelled using simple boundary conditions an original rectangular prism of material resting on a thrust plane is considered to be subject to various pure and simple shear components operating parallel to the thrust deformation gradient tensors are determined for the models and solutions found for the principal strains a two dimensional model considers heterogeneous simple shear combined with a stretch in the direction of shear simple shear zones arise as a special case where 1 recumbent fold nappes characteristic of gravitational collapse can be modelled with 1 and thrust sheets with layer parallel shortening and folding with differential transport of nappes gives rise to additional wrench type shears solutions for the principal strains in this type of model are found and used to interpret side wall ramps and steep zones parallel to nappe movements by including a stretch in the transport direction these differential transport models produce prolate strains 1 and oblate strains finally a brief consideration of bending strains produced in a sheet passing over a ramp indicates reversals in the shear direction during the strain history these predict possible crenulation of early thrust fabrics at ramps

microearthquake seismicity and active tectonics of northwestern greece we carried out a microearthquake survey lasting for six weeks in northwest greece using 18 portable seismograph stations to examine a region in which normal and thrust faulting have been reported in close proximity to one another with this array we located 148 events and determined fault plane solutions for eight events using only rays radiated upwards the seismicity of the region is diffuse with events extending to depths of nearly 30 km and there is a minimum in activity near a depth of 15 km the fault plane solutions exhibit a wide spectrum of fault types and orientations and are not consistent with simple zones of shortening or extension neither tractions applied to the edges or bottom of the region nor deviatoric stresses that compensate for lateral variations in crustal thickness can account for the variety of fault plane solutions we think that the complicated behavior is a manifestation of inhomogeneous deformation due at least in part to a pre existing complicated juxtaposition of structures and formations

seismicity and seismotectonics in epirus western greece results from a microearthquake survey during a twelve month passive tomography experiment in epirus in northwestern greece a total of 1368 microearthquakes were located the most accu rately located events and focal mechanisms are used here to understand the seismo tectonics of the area the seismicity shows a clear association with the main previously defined deformation zones a total of 434 well defined focal mechanisms were also used for the determination of the stress pattern in the area the computed stress field pattern is quite complex close to the surface and almost homogeneous at depths below 15 km for these depths the stress field is purely compressional in a west southwest direction whereas for shallow depths it is transpressional or even extensional for some smaller areas the abrupt change in the stress pattern which occurs as depth increases suggests the existence of a detachment surface which is provided by the evaporites that have intruded into the upper layers through the thrust zones the presence of the evaporites and their lateral extent is mapped by the seismicity distribution and con firmed by seismic tomography based on the findings we estimate a possible total evaporite thickness of almost 10 km at least for the central part of the study area such a result is important for the oil exploration efforts that have just started in epirus

ionian sea western greece its structural outline deduced from drilling and geophysical data abstract this paper outlines the preliminary structural results obtained by the compilation of geological drilling and geophysical data in western greece most external geotectonic zones of the hellenides are included in the geological setting of the marine and insular domain of western greece ionian pre apulian and apulian zones the gavrovo and pindus zones make a restricted contribution to the marine geological framework continental shelf of southwest peloponesus besides the geographical setting of the geotectonic units their general tectonic characteristics allow the following remarks to be made the main tectonic events younger than eocene are well marked in both ionian and pre apulian zones the detrital sequence shows a fast pinch out towards the apulian platform where the plio quaternary clastic layers overlap what are probably late mesozoic or early tertiary limestones taking into consideration general tectonic features we can distinguish a northern area and a southern one separated by a fault trending 30 n located on the western margin of kephallinia lefkas islands 1 a in the northern area we observe a strong tangential tectonism decreasing towards the apulian platform with transitional characteristics on the pre apulian zone paxos where asymmetrical folding occurs 2 b in the southern area from lefkas kephallinia islands to the s w cape of peloponesus the tangential tectomism is well masked by strong vertical faulting attributed to young plio quaternary deformations the fast subsidence induces huge diapiric structures in the ionian zone salt walls originating from triassic layers intersect a thick pleistocene sequence

the tectonic setting and earthquake ground hazards of the 1993 pyrgos earthquake peloponnese greece the pyrgos earthquake in western greece 26 march 1993 m l 5 2 was caused by oblique normal slip on a north dipping and wnw trending fault and produced significant damage in the town of pyrgos several lines of evidence from the epicentral area suggest that faults within two active graben in the pyrgos basin the grape and alfios grabens were reactivated during this earthquake and subsequent aftershocks evaluation of morphotectonic data the fault slip rate between 0 05 and 0 35 mm a 1 and seismic activity associated with the 1993 earthquake suggest that the alfios graben is the most active structure in the basin this graben which is 25 km long and crosses the pyrgos basin is segmented along its strike by transfer zones analysis of the seismic activity in this graben shows that transfer zones are the focus for the concentration of seismic activity and thus the concept of transfer zones is important for understanding the pyrgos earthquake the 1993 earthquake caused landslides at 47 locations and liquefaction phenomena at 7 localities within an area of 145 km 2 the lower threshold level to induce landslides was m l 4 0 and to induce liquefaction was 5 0 the majority of landslides occurred along fault scarps and either caused the slope to retreat and or acted to protect the slope gradient

structural controls on basin evolution neogene to quaternary of the ionian zone western greece turbidite deposition of oligocene to early miocene age occurred in the foreland basin to the pindus mountains which formed the nnw trending hellenide thrust front deposition was interrupted by the migration of the deformation front westwards through the foreland basin itself the kalamitsi thrust exposed in west levkas became active in late early miocene times a miocene to pliocene piggy back basin developed fed both from the thrust front to the west and the mountain belt to the east during the mid late miocene deformation remained confined to the ionian and gavrovo zones possibly related to the presence of lubricating evaporites which terminate in the pre apulian zone to the west during the late plio quaternary inner arc extension trenchward of the hellenic arc caused a system of ene and wnw basins to open under the n s tensional regime these were linked by nnw and ne transtensional faults and the system is still active in the lake trikhonis and gulf of corinth areas today in the west of the study area however post pliocene nw se compressional faults dissected the piggy back basin this compressional phase must have been either contemporaneous with or interrupted the extension active in the east from late pliocene times

observations of eastward currents in the tropical south atlantic ocean 1978 1980 data from four cruises to the tropical south atlantic ocean are used to describe the current distribution at 25 w and 27 5 28 w two distinct eastward flowing countercurrents separated by a branch of the westward flowing south equatorial current sec were observed during all the cruises the south equatorial undercurrent located between 3 s and 5 s has a subsurface velocity core with maximum speeds of about 0 4 m s geostrophic volume transports of the seuc from the surface to 1000 m range from 5 to 23 sv surface flow above the core of the seuc can be to the east or west the south equatorial countercurrent secc is located typically between 7 s and 9 s although weaker than the seuc with transports ranging from 3 to 7 sv the secc also has a subsurface velocity core maximum speeds of 0 1 m s are observed at about 275 m surface flow above the core of the secc is typically to the east upper layer waters of the secc are saltier and warmer than waters within similar density layers to the north

geometry and kinematics of active faults and their seismotectonic significance in the western corinth patras rift greece abstract the western part of the corinth patras rift is formed in an area which is being uplifted rifted domains have subsided relative to the adjacent areas in nw peloponnesus and sterea hellas but subsidence rates rarely exceed uplift rates extension is mainly accomplished by wnw trending active faults with lengths up to 25 km most of these faults show an along strike segmentation and often terminate against transfer faults displacement analysis along 170 mesoscopic faults and 36 mappable faults has been carried out to assess slip rates and to estimate the magnitudes and recurrence time intervals of earthquakes occurring along them earthquake magnitude ranges between 5 and 6 7 only eight faults appear to be capable of producing earthquake magnitudes larger than 6 recurrence times of these large earthquakes vary between 80 and 1690 years upper crustal deformation in the western corinth graben can be described by six large asymmetric grabens which are inferred to bottom out to a n dipping curved ramp the asymmetric shape of most wnw trending rifts in the hellenic peninsula including the corinth patras rift promotes the simple shear model of extension against the pure shear model in the upper crustal layer

flexural uplift of rift flanks in central greece uplifts with elevations of up to 2000 m and short wavelengths 30 35 km flank three major grabens in central greece the rio sparta and atalanti grabens they are bordered on their landward sides by narrow basins oriented parallel to the graben axes the manesi and trichonis basins at the rio graben and copais and istiea basins at the atalanti graben the flexural origin of these uplift profiles is investigated here by using thin broken plate models it is demonstrated that the observed topography of the graben flanks is consistent with the upward deflection of elastic and viscoelastic plates in response to upward directed forces applied at the graben flanks in order to evaluate to applicability of each model their predictions are checked against the observations the elastic predictive modeling fits well with the observed flexural wavelengths and the flanking seismicity however it fails to predict the graben widths and the inferred elastic layer thickness in contrast the viscoelastic model successfully explains the graben widths and the back basins as flexural hinterland basins and matches the seismological data and the time constraints of rifting it is therefore suggested that flexural uplift with viscoelastic relaxation accounts for the building of the graben flanks the invoked viscoelastic models constrain the effective elastic thickness of the plates at 10 km for the rio graben and 15 km for the sparta and atalanti grabens suggesting a low viscosity lower crust furthermore they predict low rates of tectonic uplift of the order of 0 1 mm a 1 for the atalanti graben intermediate rates of 0 24 0 37 mm a 1 for the rio graben and high rates of 0 7 0 9 mm a 1 for the sparta graben the latter are quite possibly overestimated since napping events capable of producing high local relief are traced normal to the modeled profiles

observations of near surface currents and temperature in the central and western tropical atlantic ocean eleven satellite tracked drifting buoys were deployed in the central south atlantic ocean during two austral summer and two austral winter cruises between 7 s and 11 s and 23 w and 31 w during austral winter net buoy drift was to the west surface geostrophic flow was to the east between 7 s and 9 s it is proposed that strong southeast trade winds can induce directly driven surface flows to the west that are more intense than the eastward geostrophic flows associated with the south equatorial countercurrent secc a sustained period of eastward drift within the secc was observed during austral summer when the trades are weaker the trajectories indicate surface waters north of 8 s have a mean northward meridional component and those south of 8 s a southward component the buoys which drifted north became entrained into the north brazilian coastal current nbcc and those that drifted south into the brazil current one buoy left the nbcc at about 5 n to drift northeastward in the north equatorial countercurrent necc this trajectory and historical ship drift reports suggest that the necc may extend only to 35 w to 40 w during boreal winter temperature data obtained as the buoys drifted westward and northward suggest that increases in upper layer heat content can be attributed to heat fluxes through the sea surface

estuarine flocs their size settling velocity and density the size and settling velocity of flocs of suspended sediments from the chesapeake bay were measured in laboratory experiments and in the field the curves between floc diameter and settling velocity showed a non stoke s relationship that was best described by the following settling velocity cm s 1 73 floc diameter cm 0 78 furthermore the relationship between floc diameter and settling velocity indicated that the floe density decreased as the floes increased in size in addition to changing density a cylinder shape was found to be the best shape factor