the 1986 kalamata south peloponnesus earthquake detailed study of a normal fault evidences for east west extension in the hellenic arc tectonic and seismological data collected in the field following the september 13 1986 kalamata earthquake south peloponnesus are presented and analyzed to discuss the earthquake rupture process and the regional tectonics the event occurred on the kalamata normal fault whose trace was mapped with spot images and topographic and field observations this fault is part of an approximately nnw sse en echelon system cutting through the hellenic nappes the fault striking n15 e on the average with a dip of about 50 has a minimum cumulated quaternary throw of the order of 1 km the measured coseismic slip is 6 18 cm over a length of 6 km the main shock focal mechanism obtained from long period waveform modeling strike 201 10 20 dip 45 5 rake 283 10 25 represents almost pure east west extension and is in good agreement with tectonic observations the centroid depth is constrained to 5 3 km and the seismic moment to 7 0 2 5 1017 n m over 700 aftershocks located by a 16 station network installed after the earthquake for a period of 2 weeks define two clusters separated by a gap of aftershock activity from the surface to a depth of about 10 km the main cluster to the south defines a 45 west dipping plane which lies on the downward extension of the fault mapped at the surface focal mechanisms of aftershocks on this fault plane are homogeneous and represent e w extension as the main shock in contrast the majority of focal mechanisms in the uppermost part of the foot wall show more or less e w compression probably corresponding to postseismic stress release the northern cluster of aftershocks is very dense and located away from the surface rupture within a relay zone between the kalamata and the next en echelon faults to the nw the thouria faults there focal mechanisms represent extension from about n115 to n70 and n20 corresponding mostly to fault reactivation in an area where nonrigid deformations prevail the main shock probably initiated in this relay zone 3 4 s before the rupture front reached the main fault plane and released most of the energy there the rupture presumably propagating southward the focal mechanism of the kalamata earthquake and that of the april 27 1965 earthquake located to the northwest of crete as well as the regional active normal fault pattern imply that e w extension oblique to the hellenic arc is presently the dominant tectonic regime e w stretching occurs partly on reactivated nw se faults parallel to the hellenic structures but mostly on newly formed n s normal faults across those structures the latter faults are responsible for the apparent segmentation of the hellenic belt from southern peloponnesus to crete the existence of active e w extension in this region implies a recent change in the tectonic regime and consequently a change in boundary conditions at the subduction zone probably in response to the incoming margin of africa

stress transfer by the 2008 mw 6 4 achaia earthquake to the western corinth gulf and its relation with the 2010 efpalio sequence central greece we investigate the interaction between transform faults and normal faults in western greece based on seismological analysis and static stress transfer calcula tions associated with the 8 june 2008 mw 6 4 achaia earthquake we present a re located earthquake catalog for the period between june 2008 and january 2010 when two normal faulting events on 18 mw 5 3 and 22 mw 5 2 january 2010 occurred at efpalio western corinth gulf they were located approximately 70 km northeast from the buried right lateral fault identified as the causative structure of the achaia earthquake the first efpalio event ruptured a mapped normal fault that trends east northeast west southwest dipping 55 60 to the south we estimate 2 fold seismic ity rate changes in the western corinth gulf region for the interseismic period june 2008 january 2010 and we find that inside this interval the monthly event rate re mained increased at a 2 significance level we calculate a coulomb stress increase 0 1 0 6 bar in the efpalio region using optimally oriented for failure planes and an 0 11 bar coulomb stress increase at the hypocenters of the january 2010 events when incorporating geologically defined receiver planes we conclude that the pos itive static stress changes following the achaia event promoted the observed spatio temporal clustering in the corinth gulf for this specific period we identify fault unclamping due to normal stress reduction as the physical mechanism in this case the high seismic hazard character of the target region 0 24g in the national building code emphasizes the importance of time dependent earthquake probabilities and stress mediated fault interaction studies

deformation of western greece during neogene clockwise rotation and collision with apulia following an early miocene phase of n s extension affecting the entire hellenides 50 clockwise rotation affected western greece modern gps analyses show rapid southwestward motion in southwestern greece over subducting oceanic lithosphere and no motion in the northwest where greece collided with apulia we aim to identify the deformation history of western greece associated with the rotation and the collision with apulia the timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures the results show that accompanying the onset of rotation compression was re established in western greece in the early langhian around 15 ma subsequently western greece collided with the apulian platform leading in the late miocene to a right lateral strike slip system running from the aliakmon fault zone in northern greece via the kastaniotikos fault and the thesprotiko shear zone to the kefallonia fault zone offshore western greece ne sw compression and uplift of the ionian islands was accompanied by ne sw extension in southwestern greece associated with faster southwestward motion in the south than in the north this led in the middle pliocene around 3 5 ma to collision without further shortening in northwestern greece from then onward nw se to n s extension east of apulia and gradually increasing influence of e w extension in the south accommodated motion of the hellenides around the apulian platform as a result curved extensional basin systems evolved including the gulf of amvrakikos sperchios basin gulf of evia system and the gulf of corinth saronic gulf system

a vertical section of eddy kinetic energy through the gulf stream system ocean current observations made by drifting buoys sofar floats and current meters are combined to produce the first section of eddy kinetic energy through the gulf stream and subtropical gyre along 55 w eddy kinetic energy peaks at 2000 cm2 s 2 in the surface gulf stream near 39 n and decreases latitudinally and vertically to a low of 0 5 cm2 s 2 in the abyssal gyre interior 4000 m 28 n still further south eddy energy increases slightly in the region of the north equatorial current

cgps time series and trajectories of crustal motion along the west hellenic arc summary western greece is one of the seismotectonically most active regions in europe the main tectonic structures are the west hellenic arc wha and the kephalonia fault zone in order to monitor and understand the crustal movements in space and time a continuous gps network was installed in this paper we present results of 6 yr 1995 2001 of measurements to ensure a consistent reference frame 54 mainly european igs and euref sites were included in the processing a selected subset was used to estimate an euler pole for the rotation of eurasia in order to obtain coordinate time series of high precision that are representative for crustal deformation special emphasis was given to the elimination of non tectonic effects four steps of improvement were pursued including a reprocessing after exclusion of poor data the removal of remaining outliers the correction of unknown phase centre offsets after antenna changes and weighted common mode filtering with this procedure non tectonic irregularities were reduced significantly and the precision was improved by an average of 40 per cent the final time series are used as a base for depicting trajectories of crustal motion interpreting the temporal behaviour of the sites and for estimating velocities for the first time height changes in the wha area were detected and quantified by gps sites that are located near the epicentres of the 1997 strofades mw 6 6 and the 1999 athens mw 6 0 earthquakes are particularly considered

the flux and mixing rates of antarctic bottom water within the north atlantic calculation was made of the northward flow of antarctic bottom water into the western north atlantic basin through a passageway approximately 300 km wide between the ceara rise and the mid atlantic ridge at about 4 n two moorings carrying four current meters each were placed in the region where currents were expected to be the greatest and were left for 360 days the current was not steady but exhibited large surges with approximately a 60 day time scale whose cause is unknown current meters in the fastest flowing region all exhibited a net northward flow it is estimated that approximately 0 8 106 m3 s 1 of water colder than 1 9 c potential temperature flowed on the average into the north atlantic with this number possibly being too small by 0 3 106 m3 s 1 or too big by 0 1 106 m3 s 1 depending upon estimates of the width of the region which the current meters sample however these numbers differ from geostrophic estimates of 1 98 106 m3 s 1 the disagreement coming almost entirely from the fact that the geostrophic estimates give a sizeable flux of water colder than 1 2 c while the current meters do not based upon the two different flux rates residence times and mixing coefficients are calculated for antarctic bottom water for each 0 1 c potential temperature interval from 1 0 c to 1 9 c finally some comments on the dynamics of the northward flow are made

long term versus short term deformation of the meizoseismal area of the 2008 achaia elia mw 6 4 earthquake in nw peloponnese greece evidence from historical triangulation and morphotectonic data abstract the deformation of the meizoseismal area of the 2008 achaia elia mw 6 4 earthquake in nw peloponnese of the first significant strike slip earthquake in continental greece was examined in two time scales of 102 years based on the analysis of high accuracy historical triangulation data describing shear and of 105 106 years based on the analysis of the hydrographic network of the area for signs of streams offset by faulting our study revealed pre seismic accumulation of shear strain of the order of 0 2 rad year in the study area consistent with recent gps evidence but no signs of significant strike slip induced offsets in the hydrographic network these results confirm the hypothesis that the 2008 fault which did not reached the surface and was not associated with significant seismic ground deformation probably because of a surface flysch layer filtering high strain events was associated with an immature or a dormant recently activated fault this fault about 150 km long and discordant to the morphotectonic trends of the area seems first to contain segments which have progressively reactivated in a specific direction in the last 20 years reminiscent of the north anatolian fault and second to limit an 150 km wide recent shear zone in the internal part of the arc in a region mostly dominated by thrust faulting and strong destructive earthquakes

along strike changes in the structural evolution over a brittle detachment fault example of the pleistocene corinth patras rift greece abstract the patras corinth and northern saronic gulfs occupy a 200 km long n120 trending pleistocene rift zone where peloponnese drifts away from mainland greece the axes of patras and corinth basins are 25 km apart and linked by two transfer fault zones trending n040 the older one defines the western slope of panachaikon mountain and the younger one limits the narrow rion patras littoral plain between these two faults the ca 4 km thick rion patras series dips 20 30 ssw it is part of the patras gulf synrift deposits which pile in an asymmetric basin governed by a fault dipping ca 25 35 nne located in the southern gulf of patras mapping of this fault to the east in northern peloponnese shows that it is an inactive north dipping low angle normal fault 0 to 30 n called the northern peloponnese major fault npmf the structural evolution of the npmf was different in the gulfs of patras and corinth in the gulf of patras it is still active in northern peloponnese footwall uplift and coeval southward tilting flattened the fault and locked its southern part steeper normal faults formed north of the locked area connecting the still active northern part of the npmf to the surface after several locks the presently active normal faults psathopyrgos aigion helike trend along the southern shore of the gulf of corinth this migration of faults caused the relative 25 km northward shift of the corinth basin and the formation of ne sw trending transfer faults between the corinth and patras gulfs

fluctuations of beam attenuation coefficient in the lowest 2 m on the continental rise off nova scotia abstract two sets of time series observations of the light beam attenuation coefficient at 0 5 1 0 and 2 0 m above the bottom were made from a tripod on the nova scotia rise the three transmissometers sampled once every 16 s and operated for approximately three days beginning september 27 and five days beginning october 2 1980 temporal variations consisted of slowly varying components superimposed with occasional bursts of highly turbid waters semidiurnal periodicity prevailed in the september mooring the rapidly varying components showed larger vertical gradients than the slowly varying components suggesting that the rapid fluctuations are local resuspension events the magnitude of high frequency fluctuations and vertical gradients also contained semidiurnal periodicity spectral analysis of fluctuations of beam attenuation coefficients indicate that higher energy densities tend to be associated with the lower level 0 5 m than the higher levels 1 0 and 2 0 m semidiurnal periodicity was not apparent in the october mooring vertical gradients between 0 5 and 1 0 m above the bottom during the october mooring contained semidiurnal periodicity but not in the layer between 1 0 and 2 0 m above the bottom power spectra of the vertical gradients indicate that fluctuations are more uniform in the vertical over the frequencies lower than the semidiurnal frequency and less uniform more variable over the frequencies higher than the semidiurnal frequency

seismic coastal uplift and subsidence in rhodes island aegean arc evidence from an uplifted ancient harbour abstract archaeological evidence from a 2400 years old harbour currently about 3 m above sea level sheds light on an enigmatic sequence of coastal uplift and subsidence along the coasts of rhodes island close to a 4 km deep trough marking the east edge of the aegean arc the tectonics of this area are not clear because of the absence of major earthquakes in the last 80 years but are likely to be controlled by a combination of shear and compression producing strong earthquakes some associated with tsunamis and some with thrust uplifted notches the latter up to 6000 years old also show evidence of phases of subsidence our study focuses on remains of shipsheds in particular a ramp used to pull warships out of the water and keep them protected under cover during winter this ramp was constructed between approximately 250 225 bc and some decades later it was repaved after a major earthquake destroyed the town of rhodes and most probably the harbour and sheltered ships as historical evidence reveals 300 years later the harbour was to a great part abandoned because of a coastal uplift the only reasonable explanation for the ramp reconstruction was to counteract a 1 m seismic subsidence at around 220 bc or earlier several possible explanations can be proposed for the earthquake which produced seismic subsidence alternating with uplift in rhodes in a pattern of vertical motions different from that observed in crete or other convergent boundaries

evaluation of environmental seismic intensities of all known historical and recent earthquakes felt in zakynthos island greece using the environmental seismic intensity esi 2007 scale abstract the complete and detailed knowledge of the historical earthquakes the past earthquake environmental effects eee and the respective seismic intensities has become significant in recent years due to the fact that among others it serves as a valuable tool for revealing and highlighting sites of significant earthquake related hazards many efforts have been made to record the eee of individual recent earthquakes and evaluate their seismic intensity based on the environmental seismic intensity 2007 scale esi 2007 in greece and around the world but fewer studies have focused on the complete seismic history including historical and recent earthquakes of an area and the respective intensities based on the induced eee the central ionian islands western greece and especially zakynthos island are considered appropriate for the development of this approach the complete history of earthquakes with destructive impact on zakynthos from 1513 to present is presented emphasis is given on eee while the respective esi 2007 intensities are assigned based on the eee s distribution on the affected fault blocks it is concluded that eastern zakynthos has been affected more often and severely by earthquakes this selective distribution is attributed to the neotectonic setting of zakynthos the recording of the eee over the past five centuries and the study of possible correlation with the seismotectonic structure of the affected area could be used as a basic guide for the reduction of the future seismic risk and the risk from eee through effective land use planning and preparedness in earthquake prone areas

eddy energy of the northwest atlantic and gulf of mexico determined from geos 3 altimetry from may 1975 to october 1978 the geos 3 satellite altimeter made numerous repeated observations of sea surface topography in the northwest atlantic and gulf of mexico by comparing members of about 1000 collinear pairs of altimeter profiles we have determined mesoscale sea height variability and eddy kinetic energy in these ocean regions our results agree qualitatively with estimates made from traditional oceanographic surveys but significant quantitative differences exist in certain areas especially in the gulf stream between florida and cape hatteras where the altimetric results show less variability the reason for this appears to be due to differences in spatial sampling historical oceanographic measurements are relatively sparse and must be aggregrated into small geographic boxes to compute variability statistics results therefore represent a combination of temporal and spatial variability in contrast repeated satellite altimeter tracks provide point measurements of changes of sea height and slope this enables determination of temporal variability alone a quantity more representative of eddy energy it is important to make this distinction between space and time because in regions of strong horizontal gradient such as the gulf stream spatial variability can exceed the temporal component in mid ocean where spatial variability is negligible altimetric and oceanographic results are in excellent agreement

sedimentation under deep sea storms fast currents high concentrations of suspended sediment and grooved mud beds are associated with erosion in frequent abyssal storms where a fast deep mean flow is augmented or reversed by intense intermittent currents this occurs about 5 km below the gulf stream or its rings the waning phase of a storm results in development of bedforms and rapid deposition of a mud blanket several other regions of the world ocean display evidence of abyssal storm activity

an analysis of the optical features of the near bottom and bottom nepheloid layers in the area of the scotian rise profiles of light transmission versus depth have been studied in the region of the scotian rise of the north atlantic at bottom depths between 4900 and 5000 m a component model has been developed and consists of three components of transmission which can be combined to duplicate accurately any given transmission profile two of the components are shown to be representative of several basic phenomena the particle concentration within a uniform flow and the separation of a benthic nepheloid layer in the case of a uniform flow it is the relative magnitudes of settling and eddy diffusion which determine the shape of the transmission profile separation of the benthic nepheloid layer was inferred to be caused by an occasional cross slope velocity component the physical interpretation of the third component was ambiguous eulerian and lagrangian transformations of the data show that benthic storms that were detected at one location and time appeared nearly identical at a later time downstream and that benthic storms can be detected over a large distance distance and time scales obtained from these transformations show the area of the scotian rise to be one characterized by bottom storms which keep their general form over periods of at least 2 weeks and for distances traveled of at least 400 km

detection of active fault scarps in western peloponnese greece abstract this study aims at reconstructing pleistocene slope erosion processes and transformation of relief in well developed pleistocene tyrrhenian marine terraces along the western peloponnese the investigations are based on existing geological data field observations a selected seismic reflection profile sedimentological analysis and radiometric dating aftershock rupture segment extends for 6 km in a wnw direction each fault movement in an earthquake results in a sudden increase in the size of the scarp by an amount ranging from a few centimeters to several meters thrust faulting occurs on shallow dipping faults and does not commonly produce a true fault scarp because the tip of the upper part over the thrust block tends to collapse leaving a sinuous scarp that does not coincide with the fault plane strike slip faulting may result in a scarp if there is a significant extensional or thrust component of motion or if rock types with different weathering characteristics and thickness are compared by faulting failing this both active and inactive faults are often marked by a fault line a line of preferential erosion along the fault the combined effects of fault motion erosion and sediment deposition affect the form of the scarp and the latter two will eventually eliminate it after movement on the fault ceases if the rock erosion rates on both fault sides are known or can be assumed to be negligible and the sediments deposited contain material that can be dated then the magnitude of the scarp can be used to determine the age at which the scarp began to form and the long term rate of movement on the fault more information regarding the relative significance and rate of movement of these faults can be obtained by observing their effects on the drainage pattern in the area in particular morphotectonic data indicate that the observed rupture segment may reflect a fault line scarp corresponding to an old fault scarp which belongs to the isotopic stage 7 or prior i e isotopic stage 11 during the evolution of nw peloponnese basin moreover morphotectonic data clearly shows that nw peloponnese is characterized by a complex structural pattern and erosion process phenomena aided by human activity this data is well supported by seismic reflection profiles information

short distance variability in slope bed forms along the southwestern adriatic margin central mediterranean abstract the slope of sw adriatic margin sam is impinged today by two bottom water masses of thermohaline origin that interact constructively along a preferred path the levantine intermediate water liw generated in the eastern mediterranean through intense evaporation and flowing along the contour and the north adriatic dense water naddw formed on the shallow north adriatic and cascading episodically off the shelf these two southward flowing bottom water masses impact the upper slope which is characterized by an irregular physiographic setting and together create the bottom current deposits e g fine grained contourite drifts and sediment waves and related erosional features e g furrows scours comet marks this study is focussed on a small open slope area of the sam ca 35 25 km where high resolution seismic data allow observe elongated contour parallel scours widespread erosion surfaces accompanied by wide crescent shape scours and furrow fields and giant comet marks spatially associated and genetically linked along a common current path further downslope and away from this highly energetic current path a field of sediment waves migrates upcurrent and shows bifurcated crests in some cases the downcurrent limbs of the sediment waves display a well defined erosional character on seismic profiles and furrows on side scan sonar mosaics all bottom current features observed are in equilibrium with the present day oceanographic regime as documented by the available current metre data moreover sediment cores suggest that the sediment waves are actively migrating during the present interglacial possibly implying that bottom waters formation was enhanced after the shallow adriatic shelf was drowned during the late quaternary eustatic rise the sam slope represents therefore an ideal site to improve our understanding of the depositional impact of bottom currents along the mediterranean margins and may provide useful hints on the activity of bottom currents elsewhere on the mediterranean margins

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

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

active faulting at the western tip of the gulf of corinth greece from high resolution seismic data abstract the gulf of corinth is one of the fastest spreading intra continental rifts on earth gps data indicate that the rift is currently opening in a nne ssw direction with a rate of extension reaching up to 16 mm yr 1 in its westernmost part although the rest of the offshore rift has been well studied the western tip of the rift is still poorly explored we present an accurate map of submarine faults in this area based on two high resolution seismic reflection surveys single channel sparker in the eastern part of the studied area the sedimentary infill is affected by the known north eratini south eratini and west channel faults further to the west the seafloor is mostly flat and is bounded to the north by the normal south dipping trizonia fault to the north the shallower part of the gulf shows to the east a diffuse pattern of normal and strike slip deformation which is replaced to the west by a 7 5 km long se striking strike slip fault zone called the managouli fault zone to the westernmost tip of the gulf in the nafpaktos basin two fault sets with different strikes are encountered the one with a ne sw strike exhibits a clear strike slip component the western tip of the gulf of corinth is the only part of the corinth rift where convincing evidence for strike slip movement has been found this fault pattern is likely related to the complex deformation occurring at the diffuse junction at the western tip of the rift between three crustal blocks continental greece peloponnese and the ionian island akarnania block

underthrusting and exhumation a comparison between the external hellenides and the hot cycladic and cold south aegean core complexes greece 1 after their emplacement in the course of the late mesozoic and the cenozoic the hellenic nappes became fragmented during late orogenic extension since the late eocene here we focus on the transition of underthrusting during nappe emplacement to exhumation during late orogenic extension to this end we compared previously published data on the structural geological and metamorphic history of the underthrusted parts of the tripolitza and ionian nappes which were exhumed in the cycladic and south aegean windows with newly obtained data on the sedimentary stratigraphic and structural development of the part of these nappes in the foreland in front of the subduction thrust the results allow the identification of two major events event 1 took place around the eocene oligocene transition and marks the onset of underthrusting of the tripolitza nappe below the pindos nappe and the ionian nappe below the tripolitza nappe respectively this led to the uplift and erosion of the pindos unit and the onset of deposition of the tripolitza and ionian flysch in front of the pindos thrust together with the formation of mylonites at the base of the metamorphosed portions of the pindos unit related to the underthrusting of the tripolitza unit event 2 occurred in the latest oligocene to earliest miocene and marks the decoupling of the ionian unit from the underthrusting plate the accretion of the tripolitza and ionian units to the overriding plate and the onset of late orogenic extension and exhumation in the overriding plate this led to the formation of the south aegean and cycladic core complexes and the subsidence of the klematia paramythia half graben throughout the early miocene

on the mechanics of earthquake afterslip we propose a model for earthquake afterslip based on rate and state variable friction laws in the model afterslip is attributed to the interaction of a velocity weakening region at depth within which earthquakes nucleate with an upper region of velocity strengthening frictional behavior the existence of this upper region is supported by independent seismologic observations and the results of laboratory friction experiments in our model afterslip is the result of relaxation of a stress perturbation within the velocity strengthening region which arises when an earthquake propagates into that region from below we derive the stress perturbation and its decay from the friction constitutive law using a simple 1 degree of freedom approximation for the elastic interaction between the fault and its surroundings this approximation is based on thickness averaged displacements and slip velocities within the velocity strengthening region which is assumed to slip as a rigid block coseismic and postseismic slip are coupled through the thickness averaged stiffness k of the velocity strengthening region we assume k to be inversely proportional to the thickness of this region which means that thicker velocity strengthening regions have a greater tendency to arrest coseismic slip we model the afterslip time histories of the 1966 parkfield and 1987 superstition hills earthquakes and relate the model parameters to physical parameters which may govern the rheologic behavior of the faults in accord with field observations our model predicts 1 that afterslip on some faults scales with the thickness of the unconsolidated sedimentary cover and 2 that proportionally more afterslip occurs for earthquakes in which coseismic surface slip is small compared with coseismic slip at depth velocity strengthening frictional behavior is to be expected for faults within poorly consolidated sediments and for those that contain significant gouge zones about 500 m within their shallow regions 3 5 km combining our results with those of recent laboratory friction studies indicates that relatively young faults with little accumulated fault gouge should exhibit little afterslip

subduction erosion and accretion in the solomon sea region abstract the solomon sea region is an area of intense tectonic activity characterized by structural complexity a high level of seismicity and volcanism and rapid evolution of plate boundaries there is little accretion in the eastern new britain trench accretion gradually increases westward with thick accretion in the western new britain trench and in the trobriand subduction system the thick accretion in the western part of the new britain trench may be a result of collision from the north of finisterre huon block with new guinea mainland the present boundary of the collision is along the ram markham fault deformation structures and present day seismicity suggest that the northern block is under compression accretion has occurred in the sediment filled trenches in the solomon sea the scale of the accretionary wedge depends on the amount of trench fill sediment available it is unlikely that there is no sediment supply to the eastern part of the new britain trench where no accretion is observed and subduction erosion may be occurring there are two possible mechanisms for subduction erosion of sediment either a rapid rate of subduction relative to the supply of sediment inhibiting sediment accumulation in the trench or horizontal tensional force superimposed on both the forearc and backarc regions of the arc seafloor spreading in both the manus and woodlark basins is fan like with nearby poles in the western margins of the basins this may be a reflection of a horizontally compressional field in the western part and a tensional field in the eastern part of the solomon sea therefore it is possible to conclude that the consumption of sediment in the eastern new britain trench is related to the horizontal tensional field superimposed on both the forearc and backarc regions of the subduction system imbricated thrust and overthrust faults in the western new britain trench and trobriand trough are not linear over long distance but form wavy patterns in blocks with unit distance of approximately 10 km

correlation between surface gulf stream and bottom flow new 5000 meters depth abstract spectral analyses of three long term 8 months deep 5 km current meter records located on the scotian rise 40 n 62 w and a time series of the average northerly position of the surface gulf stream system obtained from analyses of satellite data give evidence at a period of about 2 weeks that the gulf stream system is influencing the ocean in this region from the surface to the bottom

stress drop at the kephalonia transform zone estimated from the 2014 seismic sequence abstract the kephalonia transform zone ktz is a seismically active dextral transform fault decoupling the extensional deformed area of the ionian abyssal plain and the compressional deformed area of the mediterranean ridge we estimate a prominent steady state strain rate of 225 20 nstrain year across the ktz from the mean velocities of permanent global navigation satellite system gnss stations in east italy and west greece which confirms previous estimates based on the regional statistical seismicity and using the local gutenberg richter relation we investigate the energetic balance between stress accumulated as a consequence of the continuous dextral shear deformation and the average stress released by shallow seismicity if the maximum expected magnitude is mw 7 4 the estimated a and b parameters of the local gutenberg richter relation and the geodetically determined shear strain rate set an upper limit to the regional stress drop 0 4 mpa we verify these values by analyzing a seismic sequence on the ktz between january and february 2014 which culminated in the mw 6 09 event of jan 26 and the mw 6 14 event of feb 3 the estimated epicenters lie within a few kilometers from each other on the western side of the kephalonia island at a hypocentral depth 10 km the measured coseismic displacements of gnss stations in this area fit the expected surface dislocation which can be predicted for an elastic half space using the measured fault plane solutions as input if the hypocenters of the aftershocks are taken as indicator of optimal dextral shear stress orientation then a low regional deviatoric stress of 0 4 mpa that is comparable with the maximum regional stress drop estimated above is required for the coulomb stress to match the pattern of the aftershocks of the 2014 sequence as a consequence we conclude that the regional deviatoric stress and the seismically released shear stress are in close balance in the ktz seismic province

the cephalonia transform fault and its extension to western lefkada island greece the central area of the ionian islands is dominated by the existence of a major tectonic structure called the cephalonia transform fault ctf its main part cephalonia segment has been identified by previous work based on the spatial distribution of earthquake foci fault plane solutions of strong earthquakes active tectonics structural studies and geodetic measurements this part cephalonia segment which exhibits strike slip motion with a thrust component strikes in a northeast direction dips to the southeast and has a length of 90 km in the present paper information concerning new fault plane solutions orientation of isoseismals sea bottom topography and recent gps results are used to further check the properties of this southern part of the ctf and to explore its northeastward prolongation to lefkada island it is shown that the ctf is extended to the western coast of lefkada this northern branch lefkada segment of the ctf which is also characterized by strike slip motion with a thrust component strikes in a north northeast direction dips to the east southeast and has a length of 40 km these two segments of the ctf form a major kinematic boundary where the slip rate is 2 3 cm yr

the relative motion between africa and eurasia as derived from itrf2000 and gps data 1 studies of intra and inter plate deformation typically need a model describing the motions of the stable part of the tectonic plates for reference purposes we have developed deos2k a model for the current motion of seven major tectonic plates derived from space geodetic observations this paper focuses on relative motion between africa and eurasia in the past this motion has been poorly established because of poor data coverage for africa deos2k is based on itrf2000 altamimi et al 2002 and new african gps observations it is an improvement over the nuvel 1a model for predicting the present day relative motions of these two plates deos2k predicts in northeastern africa that africa eurasia relative motion is about 40 smaller in magnitude than nuvel 1a and trends more to the northwest this is consistent with independent local geodetic observations a similar shift in orientation clockwise is observed at the western tip of the plate boundary

contemporary kinematics of the southern aegean and the mediterranean ridge summary this study focuses on the kinematics of the southern aegean and the mediterranean ridge mr a quantification of the deformation of the mr is essential for both evaluating physical models of accretionary wedges in general and for obtaining a self consistent model of the surface deformation over the entire nubia eurasia nu eu plate boundary zone in the eastern mediterranean previous kinematic studies have not properly considered the deformation field south of the hellenic arc although this study focuses on the deformation field of the mr we also discuss the kinematics of the southern aegean because the geometry and movement of the hellenic arc determine to a large extent the kinematic boundary conditions for kinematic studies of the mr we calculate a continuous velocity and strain rate field by interpolating model velocities that are fitted in a least squares sense to published global positioning system gps velocities in the interpolation we use information from a detailed data set of onshore and offshore active faulting to place constraints on the expected style and direction of the model strain rate field in addition we use the orientations of tracks left by seamounts travelling into the wedge to further constrain the offshore deformation pattern our model results highlight the presence of active shear partitioning within the mediterranean ridge high compressional strain rates between the ridge crest and the deformation front accommodate approximately 60 70 per cent of the total motion over the wedge and the outward growth rate of the frontal thrust is 4m m yr 1 strain partitioning within the wedge leads to 19 23 mm yr 1 of dextral motion at the wedge backstop contact of the western mr whereas the pliny and strabo trenches in the eastern mr accommodate 21 23 mm yr 1 of sinistral motion the backstop of the western mr is kinematically part of the southern aegean which moves as a single block the aegean block ae at 33 34 mm yr 1 in the direction of s24 w 1 towards stable nubia nu our model confirms that there is a clear divergence between the western and eastern hellenic arc and we argue for a causal relation between the outward motion of the arc and the gradient in the regional geoid anomaly our results suggest that a significant driving source of the surface velocity field lies south of the hellenic arc and only for the southeastern aegean could there be some effect as a result of gravitational collapse associated with density differences within the overriding plate

seismicity and geodynamics of western peloponnese and central ionian islands insights from a local seismic deployment abstract the tectonic setting of western peloponnese and central ionian islands greece is characterized by the subduction of the oceanic african plate beneath the aegean micro plate the transition from subduction to continental collision in northwestern greece is accommodated by the right lateral cephalonia transform fault in this work we exploit the recordings of a temporary seismic network composed of 15 stations operating from july 2016 until may 2017 to investigate the complex deformation of this region our local network fills in a major observational gap in one of the most tectonically active regions of the hellenic arc we detected and located more than 1200 local earthquakes and constrained five 1d optimum local velocity models the relocated seismicity including the aftershock sequence that followed the october 2018 mw 6 7 earthquake offshore zakynthos and associated focal mechanisms constrained for the major earthquakes point out a complex crustal deformation we propose a clockwise rotation of the ionian akarnania block accommodated by major marginal strike slip fault zones that appear segmented along their strike additionally left lateral motion is observed on the kyllini cephalonia fault along a north west direction finally the seismicity recorded in north cephalonia offshore myrtos and fiskardo suggests that the cephalonia transform fault is a large deformation zone where secondary wnw striking sinistral strike slip faults occur

new constraints from seismology and geodesy on the mw 6 4 2008 movri greece earthquake evidence for a growing strike slip fault system the 2008 mw 6 4 movri earthquake ruptured a nne right lateral strike slip fault about 30 km south of the city of patras although some strike slip activity on minor faults was known there was no tectonic evidence of large scale ns striking fault and such a large event was not anticipated following the event a network of six stations was installed for 4 months in the epicentral area in order to monitor aftershocks and in particular the northern part of the rupture area closest to the city of patras we combine these new aftershock observations with gps measurements of an already existing geodetic network in the area performed just after the earthquake as well as with sar interferograms together with already published source studies in order to refine already proposed models of this event the combined data set allows defining much more accurately the lateral and vertical limits of the rupture its length inferred from geodesy is 15 km and its modelled upper edge 17 km the seismic moment then constrains the lower edge to coincide within a few kilometres with the moho interface the absence of seismicity in the shallow crust above the co seismic fault is interpreted as a result of the decoupling effect of possible presence of salt layers above the rupture area near 14 to 16 km in depth which favours our interpretation of an immature strike slip fault system compatible with the absence of surface ruptures the immature character of this large crustal fault is further suggested by the high variability of focal mechanisms and of fault geometries deduced from aftershock clusters in the strike direction its geometry and mechanism is consistent with the crustal shear striking nne revealed by gps in this region this shear and faulting activity might be generated by the differential slip rate on the subduction interface 50 km to the south leading to a north northeastward propagating strike slip fault zone the wide extension of the aftershock distribution forming a nne alignment beyond the rupture area towards the north suggests a localization process of the shear strain which could be the preliminary stage of fault propagation further to the nne an alternative speculative model for this regional stress could be the existence of a well developed nne striking shear zone within the uppermost mantle marking at depth the southward propagation of the northern branch of the north anatolian fault both models may not be exclusive of each other and in fact their sources may be mechanically interdependent

the mantle magnitude mm and the slowness parameter θ five years of real time use in the context of tsunami warning we study a database of more than 119 000 measurements of the mantle magnitude mm introduced by okal and talandier 1989 obtained since 1999 as part of the operational procedures at the pacific tsunami warning center the perfor mance of this method is significantly affected by the seismic instrumentation at the recording station with the very broadband sts 1 and ks54000 systems offering the lowest residuals between measured values of mm and those predicted from the har vard centroid moment tensor cmt catalog and also by the period at which spec tral amplitudes are measured with the best results between 70 and 250 sec with such mild restrictions estimates of seismic moments can be obtained in real time by retaining either the maximum value of mm measured on each record or its average over the various mantle frequencies with the resulting residuals on the order of 0 1 0 2 moment magnitude units mm deficiencies in the case of the two large earthquakes of peru 2001 and hokkaido 2003 are attributed to azimuthal bias from an excess of stations principally in north america in directions nodal for the focal mechanism and directivity patterns we further study a group of more than 3000 measurements of the energy to moment ratio h introduced by newman and okal 1998 which allows the real time identification of teleseismic sources violating scaling laws and in particular of so called tsunami earthquakes the use of a sliding window of analysis in the computation of h allows the separation of late earthquakes characterized by a delayed but fast moment release from truly slow earthquakes many such events are recognized notably on major oceanic and con tinental strike slip faults introduction and background we present detailed analyses of a large dataset resulting from implementation as part of the operational procedures of the pacific tsunami warning center ptwc of the real time calculation of the mantle magnitude mm and of the slowness parameter h as defined and introduced by okal and talandier 1989 and newman and okal 1998 re spectively during the past five years more than 119 000 individual measurements of mm and 3000 values of h have been computed through automated algorithms these values contribute to the estimation of the source characteristic of distant earthquakes in the framework of the real time as sessment of their tsunamigenic potential this study offers a progress report on the performance of the algorithms and in particular discusses the influence of instrumentation at the various reporting stations as the final revision of this article was being prepared the occurrence of the great sumatra earthquake on 26 de cember 2004 provided an opportunity to extend the concepts of mm and h to a range of magnitudes unexplored for the

close up stereo photographs of abyssal bedforms on the nova scotian continental rise abstract close up stereo photographs of the seafloor were taken at five stations on the nova scotian rise stereo viewing reveals abundant relief with heights in the range 1 50 mm which are not apparent in oblique monoscopic pictures objects with dimensions of 0 1 mm can be resolved and areas up to 1 0 cm 2 can be viewed photogrammetric contour mapping at one millimeter intervals of longitudinal ripples gives in situ dimensions of 12 cm height 90 cm full width and 410 cm 2 cross sectional area a field of ripples spaced at 5 m with a sediment density of 0 7 g cm 3 contains 5 7 kg dry sediment per m 2 seafloor roughness on the scale of centimeters in abyssal high energy boundary layers reflects both recent sedimentary and biological processes the spatial density of eight classes of bed relief varies on scales of tens of kilometers downslope and is consistent with downslope trends in the occurrence of larger bedforms texture of surface sediments and bottom boundary layer conditions most relief is biogenic directly or indirectly and most is streamlined

deformation of the ancient mole of palairos western greece by faulting and liquefaction abstract a submerged 2300 years old mole or breakwater with a sigmoidal shape has been identified at the palairos harbor akarnania sw greece mainland different possible scenarios could be proposed to explain this enigmatic shape for an ancient breakwater such as selective erosion of the original structure construction above existing shoals or reefs gravity sliding and post construction offset due to strike slip faulting but all these scenarios seem rather weak inspired by a large scale lateral offset of a retaining wall of a quay at the barcelona harbor due to static liquefaction by evidence of strike slip earthquakes and of liquefaction potential in the study area as well as by recent evidence for long duration steady nearly uni directional dynamic displacements in the near field of strike slip faults we propose an alternative scenario for this mole an earthquake associated with strike slip faulting and high acceleration produced liquefaction of the mole foundations and long duration nearly unidirectional tectonic slip while the later part of the steady slip produced additional secondary surficial slip on liquefied layers

a two fault model of the 2003 leucas aegean arc earthquake based on topological inversion of gps data the fault pattern of the 2003 m w 6 2 leucas lefkada lefkas earthquake at the northwest edge of the aegean arc an area of very high seismicity rates was modeled using global positioning system gps data the rupture process of this earthquake is a matter of debate because of the complexities in the aftershock distribution and in the waveforms of the mainshock as well as the kinematics of the area are not well understood especially the characteristics of the cephalonia kefalonia keffalinia transform fault and its relationship with major discordant active thrusts representing the tectonic fabric of western greece our analysis was based on the topological inversion topinv algorithm which uses a deterministic hypergrid search to identify one or more clusters of n dimensional points around the true solution of the system of observation equations from these clusters optimal estimators of the variables defining okada type faults and their variance covariance matrices are computed as statistical moments and results are validated by minimum mean misfits faulting of the 2003 seismic sequence was approximated by two stepping essentially strike slip segments with a separation of 10 km this pattern is in agreement with fault rupture models based on inversion of seismological data and their main difference is a thrust component in the major segment well constrained by interferometric synthetic aperture radar and gps observations of uplift this thrust component may reflect either postseismic evaporite salt controlled slip or uncertainties in the inversion models the 2003 and other seismic sequences among them the 1953 m 7 2 cephalonia catastrophic earthquakes that were associated with major uplift seem to confirm previous views for an 100 km wide shear zone superimposed on compression along the edges of the aegean arc online material description of analytical inversion methodology the topological inversion algorithm topinv including a figure showing projection of hypergrids on planes

sediment dynamics driven by contour currents and mesoscale eddies along continental slope a case study of the northern south china sea abstract based upon 3 d seismic reflection data published drill core studies oceanographic observations and numerical modelling this study identifies a small scale contourite depositional system that is locally confined by canyons slope failures erosional terraces and erosional slopes on the jianfeng slope northern south china sea 1500 to 2300 m water depth possible oceanic driving mechanisms for the spatial heterogeneity in sedimentation and erosion within the quaternary deposits in this complex slope system are investigated numerical simulations show that the quasi steady south china sea deep water circulation which affects the study area is characterised by low velocities maximum 4 cm s with a slight modulation by tides 1 cm s this quasi steady deep water thermohaline circulation is able to keep sediment particles in suspension rather than to erode seafloor sediment the bottom hydrodynamic regime becomes energetic when mesoscale eddies horizontal scale of 10 to 100 km approach our modelling study indicates that both surface and bottom mesoscale eddies are essential to account for the spatial heterogeneity in sedimentation pattern along the northern south china sea continental slope according to simulation the eddy front contains the highest flow velocity over a mesoscale eddy cycle 45 days exceeding the threshold for resuspension of unconsolidated sediment 15 cm s as a consequence massive resuspension is produced at various sites and redistributed by sub mesoscale horizontal scale of 1 to 10 km circulations originated from an eddy topography interaction in contrast to the surrounding areas which are subject to erosional forcing for a relatively long part 7 of an eddy cycle both the locally confined drift and a further upstream large elongated mounded drift experience little erosion

long period surface motion of the multi patch mw9 0 tohoku oki earthquake we show that it is possible to capture the oscillatory ground motion induced by the tohoku oki event for periods ranging from 3 to 100s using precise point positioning ppp we find that the ground motions of the sedimentary basins of japan were large respectively 0 15m s and 0 15m s2 for velocity and acceleration even for periods larger than 3s we compare geodetic observables with a ground motion prediction equation gmpe designed for japan seismicity and find that the spectral acceleration sa is well estimated for periods larger than 3s and distances ranging from 100 to 500km at last through the analysis of the displacement attenuation plots we show that the 2011 tohoku oki event is likely composed of multiple rupture patches as suggested before by time reversal inversions of seismic data

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

abyssal currents and advection of resuspended sediment along the northeastern bermuda rise abstract an integrated study using current meters time series nephelometers and water samplers for measurements of particulate matter concentration revealed an intense nepheloid layer centered on the slopes of the eastward scarp the northeastern boundary of the bermuda rise these slopes also contained extensive furrows truncated seismic reflectors and wisconsin age and older surface sediments the abyssal circulation in this region appears to be accelerated when it encounters the steep topography of the eastward scarp eroding sediments creating the erosional furrows and moving eroded sediment upslope instruments on top of the bermuda rise recorded episodic events benthic storms where particle concentrations at 25 m above the bottom increased from a background level of 60 g 1 1 to maximum of 251 g 1 1 and current velocities were nearly 20 cm s 1 net transport of both water and entrained sediment was to the west northwest during the largest benthic storm water temperature decreased by 0 1 c consistent with a 300 600 m upslope transport of water and resuspended sediments from the upper slopes of the eastward scarp when currents carry resuspended sediment over the rim of the eastward scarp to the plateau region the current slows depositing its sediment load thus the plateau is growing upwards slowly at the expense of the surrounding scarps

evolution of the offshore western gulf of corinth the young gulf of corinth rift in central greece is an ideal place to study processes occurring during the initiation and early stages of continental extension at the east end of the 100 km long e w rift holocene extension on n dipping faults equates to geodetic extension rates at the western end however estimated extension rates on n dipping onshore faults account for only 20 40 of the geodetically measured rates 10 15 mm yr we use high quality multichannel seismic reflection and swath bathymetry data to investigate the tectonics of the western gulf and quantify the contribution of offshore fault activity toward total rift extension five major offshore faults generate the variable basement topography and a ca 0 4 ma unconformity separates stratigraphy into two main packages basin fill geometry indicates that during the early stages of subsidence of the offshore western gulf s dipping faults were the dominant border fault structure this is still the case at the western end of the western gulf however elsewhere n dipping faults on the south margin are now relatively more dominant and cause stratigraphy to tilt south the temporally and spatially varying rift structure contrasts with the simple consistently n dipping border fault half graben geometry of the east gulf of corinth combined west gulf offshore and onshore holocene fault extension rates total 5 14 5 mm yr within the range calculated geodetically and render enhanced slip on a low angle detachment surface beneath the western gulf unnecessary

the 1953 earthquake in cephalonia western hellenic arc coastal uplift and halotectonic faulting summary geomorphological marine biological and radiometric data in combination with earlier reports reveal that the m 7 2 1953 cephalonia earthquake the most destructive but least studied earthquake in greece this century was associated with a 0 3 0 7m quasi rigid body uplift and westward tilting of the central part of the island another palaeoseismic event around 1500 yr bp associated with coastal uplifts was also identified structural data indicate that the 1953 uplift is bounded by two subparallel east dipping major reverse faults and corresponds to a piston like motion this structurally unusual pattern of seismic deformation is detached from the deformation of the basement conspicuously a thrust and different from the long term deformation pattern of the area it is probably due to the particularities of salt tectonics a 1500m thick salt layer acts as a regional dccollement while thinner layers are sandwiched between the carbonate thrust sheets that compose the overburden and reduce their friction during fault movement this crustal anisotropy is responsible for the observed anomalous attenuation of seismic waves during the 1953 and historical earthquakes the 1953 seismic surface deformation mimics long term halotectonic patterns but is not directly indicative of the regional stress field for it reflects uplift induced stresses only

origin of longitudinal triangular ripples on the nova scotian continental rise since the recognition of current produced bedforms in the deep ocean attempts have been made to predict direction intensity and variability of abyssal flow from the nature of sea floor irregularities see refs 1 3 longitudinal triangular ripples ltrs are inter mediate scale bedforms 20 cm high metres long that are becoming recognized as important and geographically widespread predictors of bottom current flow i describe here recent sea floor photographs of ltr fields on the lower continental rise off nova scotia which show that the bedforms develop in fine grained cohesive sediment with an alignment parallel to the regional contours and to mean current direction an observational model for ltr formation is proposed wherein ltrs are deposited initially as tails behind large sea floor biological mounds and are subsequently constructed and propagate in the direction of mean current by sediment transport oblique to the bedform axis this transport is induced by short term currents that deviate from mean current direction and cause formation of a separation bubble on one side or the other of the ltr crest

three dimensional model of hellenic arc deformation and origin of the cretan uplift 1 the hellenic arc of greece is the most seismically active part of europe but little is know about its mechanics we modeled deformation along the arc using a finite element model the model was intended to capture large scale 3 d structure of nubian plate subduction beneath the aegean block and its deformational consequences the shape of the interface was developed using mapped traces at the surface and earthquake hypocenters at depth model block motions were constrained by recent compilations of gps velocity vectors we simulated a 10 ka period of convergence between nubia and the aegean and calculated the strain field in the overriding plate as well as the spatial distribution and orientation of differential stress 1 3 from these calculations we derived testable quantities such as the expected seismic moment rate on the interplate contact uplift pattern and distribution of strain modes our relatively simple model broadly reproduced observed uplift patterns earthquake activity and loci of extension and contraction the model showed a localization of uplift near the island of crete where the fastest aegean uplift rates are well documented comparison of calculated expected seismic moment and observed earthquake catalogs implies a nearly fully coupled interplate contact on the basis of our modeling results we suggest that south aegean deformation is driven primarily by the fast moving 33 mm a 1 aegean upper plate overriding a nearly stalled 5 mm a 1 nubian lower plate this tectonic setting thus more closely resembles a continental thrust than it does a typical oceanic subduction zone

global evaluation of large earthquake energy from 1997 through mid 2010 1 we develop an updated radiated seismic energy e catalog of global earthquakes with seismic moment m0 1019 nm mw 6 7 from 1997 through mid 2010 recording 342 events using 17849 seismograms station specific corrections and event duration dependent total p wave group calculations allow for improved e determinations for large and long duration earthquakes we find the global mean energy to moment ratio log10 e m0 4 59 0 36 robust deviations are found for thrust t 4 74 strike slip ss 4 44 and normal n 4 51 faulting events for two regions with recent energy deficient tsunami earthquakes tse we examine all large thrust earthquakes with m0 5 1017 nm mw 5 7 to identify a regional characterization in their relative radiated energy to moment ratio while thrust events along java indonesia the site of two tse events in 1994 and 2006 are comparable t jv 4 91 to the global thrust average events along the middle america trench mat the site of the 1992 nicaragua tse are consistently deficient t mat 5 15 along the mat a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths with tse events representing the shallowest and most energetically deficient end member of the events in the study results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kpa near the surface to 2 mpa near 70 km depth

particulate size spectra behavior and origin of nepheloid layers over the nova scotian continental rise 1 26 32 m measured by coulter counter on 10 cm 3 samples correlate linearly with light beam attenuation coefficient correlation between particle volume and weight concentration indicates lower apparent particle density for low concentration suspensions a feature that is attributed to aggregation during aging of the suspension particle size distributions show unimodal form with a peak at 4 m in high concentrations near the bed changing to a bimodal form with an additional mode at 16 m in low concentrations high above the bed 500 and 1000 m a b meters above bottom the presence of the coarse mode at 1000 m a b coupled with its increase in the lower 250 m of the water column suggests that it both settles from the surface and is resuspended from the bed ultrasonic disaggregation experiments show that much of the fine mode is of aggregates but the coarse mode is single solid particles distributions with a low volume concentration increase in volume when disaggregated and are interpreted as having a relatively large part of their total distribution in unmeasured sizes 32 m distributions with a high concentration decrease in counted volume on disaggregation inversions in the light attenuation profiles are taken to indicate the presence of former bottom mixed layers and their occurrence suggests thickening of the nepheloid layer by detachment and lateral injection of these turbid mixed layers they occur at levels sufficiently high as to provide a nepheloid layer over 1500 m thick over the adjacent sohm abyssal plain the coarse mode probably comprises solid particles with a calculated settling velocity of 12 m day its absolute concentration increases toward the bed but as a proportion of the distribution it increases upward it is thus thought to be particles of surface origin both settling to the bottom and in the lower 250 m of the water column resuspended from the bed the fine mode at 4 m has a spatially constant form thought to be controlled by physical coagulation mechanisms rates of coagulation estimated from shear mechanisms suggest that the postulated change of peaked into flat size distribution by particle aggregation and settling has a time scale of a few years rather than months which is probably long when compared with the lateral injection process lower in the nepheloid layer for that reason distribution with a fine mode peak are found well above the bottom mixed layer

sedimentary processes and variations in slope current activity during the last glacial interglacial episode on the hebrides slope northern rockall trough north atlantic ocean abstract shallow cores and high resolution seismic reflection data collected from two areas along the hebrides slope indicate that a variety of depositional processes have been active since the last glacial interval seismic reflection profiles from the most northerly slope area immediately south of the wyville thomson ridge reveal a slope apron and an embayed area with a relict mid upper slope channel five cores from this locality consist of distal muddy turbidites in the area of the channel with muddy contourites interbedded with glaciomarine ice rafted sediments and thin debris flow deposits most of the cores are topped by sandy contourites the preserved sequence suggests that lowered sea levels during the last glaciation 10 ka resulted in a predominance of downslope and glaciomarine sedimentation with bottom current activity greatly suppressed at the onset of deglaciation alongslope activity increased as bottom currents gained in strength with climatic fluctuation and the retreat of ice sheets from the shelf producing muddy and sandy contourites present day current activity is still much in evidence with two current meter stations on the mid and lower slope recording a northward flowing current following the bathymetric contours recorded peak velocities at 468 m and 403 m were 26 48 cm s some elements of reverse flow at the deeper site may be tidal oscillation compounded by short duration high intensity benthic storms cores from the more southerly area in the vicinity of the geikie escarpment penetrated hemipelagites erosively overlain by sandy contourites dinoflagellate and nannofossil dating of these deposits indicate that the lower hemipelagites are of late glacial age 13 ka the sandy contourites are probably of early holocene age the lack of the allerod bolling interstadial and younger dryas stadial may be indicative of a hiatus in sedimentation a possible cause of this may be the increasing slope angles up to 28 on the escarpment concentrating the effects of a thermohaline slope current current flow was also strengthened during deglaciation producing erosion or non deposition of the lower units leaving the coarser top only sandy contourites

crustal motion and deformation in greece from a decade of gps measurements 1993 2003 abstract the hellenic plate boundary region located in the collision zone between the nubian arabian and eurasian lithospheric plates is one of the seismo tectonically most active areas of europe during the last 15 years gps measurements have been used to determine the crustal motion in the area of greece with the aim to better understand the geodynamical processes of this region an extended reoccupation network covering whole greece has been measured periodically in numerous gps campaigns since the late eighties and a continuous gps network has been operated in the region of the ionian sea since 1995 in this paper we present a new detailed high quality solution of continuous and campaign type measurements acquired between 1993 and 2003 during the gps processing a special effort was made to obtain consistent results with highest possible accuracies and reliabilities data of 54 mainly european igs and euref sites were included in the gps processing in order to obtain results which are internally consistent with the european kinematic field and order to allow for a regional interpretation after an overview of the results of the igs euref sites the results from more than 80 stations in greece are presented in terms of velocities time series trajectories and strain rates previous geodetic geological and seismological findings are generally confirmed and substantially refined new important results include the observation of deformation zones to the north and to the south of the north aegean trough and in the west hellenic arc region arc parallel extension of about 19 mm yr along the hellenic arc and compression between the ionian islands and the greek mainland due to continuous long term observations of 4 8 years it was possible to extract height changes from the gps time series in greece we observe a differential subsidence of the order of 2 mm yr between the northern and central ionian islands across the kefalonia fault zone the differential subsidence of the central ionian islands with respect to the northwestern greek mainland amounts to 4 mm yr

geodetic evidence for tectonic activity on the strymon fault system northeast greece abstract the current kinematic patterns of northeast greece remain largely unknown this is mainly because this region is characterised by low seismicity rates and is poorly covered by gps stations here we analyse new homogeneous gps data collected over a period of 5 5 years from the first permanent network in northeast greece hepos to shed light in the kinematics of this region we find that gps displacement vectors that derive from either side of the natural depression of the strymon valley differ significantly in orientation and magnitude specifically we find that across a distance of ca 30 km the gps displacement vectors change orientation by 130 from nnw to ssw producing a mean horizontal strain rate of 3 3 0 3 mm yr we attribute this kinematic translation to result from movement along the strymon fault system sfs a 200 km long structure that strikes nw se and extends from sw bulgaria to north aegean where possibly abuts against the north anatolian fault up to date the sfs was considered to be a major alpine and neogene geotectonic boundary of unclear holocene activity if the interseismic strain stored currently across the fault system is released seismically large earthquakes m 7 and associated coseismic lateral displacements should be expected in the area these results call for a better assessment of the earthquake risk in northeast greece which is currently evaluated as a low seismic hazard region

global seismicity of 2003 centroid moment tensor solutions for 1087 earthquakes abstract centroid moment tensor cmt solutions are presented for 1087 earthquakes that occurred during 2003 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodward j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure as represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york pp 785 797 the model of inelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of inelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2003 are reviewed

rupture process and aftershocks relocation of the 8 june 2008 mw 6 4 earthquake in northwest peloponnese western greece on 8 june 2008 at 12 25 gmt an m w 6 4 strong earthquake occurred in the area of northwest peloponnese western greece causing the death of two people and extensive damage to the surrounding area the main event and its aftershocks were recorded by one nationwide and three regional networks equipped with three component broadband seismometers initial locations of the earthquake sequence comprising 438 aftershocks showed a linear northeast southwest trend and that the mainshock was located at 22 km depth after the relocation using catalog and differential travel times most events form three distinct clusters at depths 15 25 km moment tensor solutions for the main event and its largest aftershocks exhibited a pure strike slip mechanism with one nodal plane orientated northeast southwest in accordance with the relocated seismicity a parallel nonnegative least squares inversion technique utilizing multiple time windows was used to derive the spatiotemporal slip distribution of the main event the resulting slip distribution model revealed a large slip patch maximum slip 150 cm between 10 and 20 km depth at the northeast part of the fault that also coincides with the area that suffered most of the damage another patch exhibiting smaller amounts of slip 20 50 cm is located to the southwest direction at the same depth range and smaller patches exist at 25 30 km depth most aftershocks are located in areas of low slip 25 cm filling the regions of slip deficit the 8 june earthquake occurred at an area where no previous seismological or other observations indicated the existence of a seismogenic fault at that depth and with this strike this and the fact that the event nucleated in the middle to lower crust may be interpreted as the reactivation of a fault structure that was inherited from previous tectonic phases

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

excepftonally strong near bottom flows on the continental rise of nova scotia recent current velocity measurements across the lower continental rise of nova scotia show a deep equatorwardflow with speeds maximum 73 centimeters per second among the highest recorded for the deep sea silicate measurements indicate that this flow usually consists of southern source antarctic bottom water these measurements confirm the existence of a second and deeper western boundary flow that was earlier inferredfrom geological observations

the aftershock sequence of the 2008 achaia greece earthquake joint analysis of seismicity relocation and persistent scatterers interferometry on 8 june 2008 an earthquake of mw6 4 took place in the northwestern part of peloponnese greece the main shock was felt in a wide area and caused appreciable damage along the main rupture area and particularly at the antipodal of the main shock epicenter fault edge implying strongly unilateral rupture and stopping phase effects abundant aftershocks were recorded within an area of 50 km in length in the period 8 june 2008 end of 2014 by a sufficient number of stations that secure location accuracy because the regional network is adequately dense in the area all the available phases from seismological stations in epicentral distances up to 140 km until the end of 2014 were used for relocation with the double difference technique and waveform cross correlation a quite clear 3 d representation is obtained for the aftershock zone geometry and dimensions revealing the main rupture and the activated adjacent fault segments sar data are processed using stanford method for persistent scatterers stamps and a surface deformation map constructed based on ps point displacement for the coseismic period a variable slip model with maximum slip of 1 0 m located at the lower part of the rupture plane is suggested and used for calculating the deformation field which was found in adequate agreement with geodetic measurements with the same slip model the static stress changes were calculated evidencing possible triggering of the neighboring faults that were brought closer to failure the data availability allowed monitoring the temporal variation of b values that after a continuous increase in the first 5 days returned and stabilized to 1 0 1 1 in the following years the fluctuation duration is considered as the equivalent time for fault healing which appeared very short but in full accordance with the cessation of onto fault seismicity

global patterns of radiated seismic energy and apparent stress radiated energies from shallow earthquakes with magnitudes 5 8 that occurred between 1986 and 1991 are used to examine global patterns of energy release and apparent stress in contrast to traditional methods which have relied upon empirical formulas these energies are computed through direct spectral analysis of broadband seismic waveforms velocity squared spectra of body waves are integrated after they have been corrected for effects arising from depth phases frequency dependent attenuation and focal mechanism the least squares regression fit of energy es to surface wave magnitude ms for a global set of 397 earthquakes yields log es 4 4 1 5ms which implies that the gutenberg richter relationship overestimates the energies of earthquakes the least squares fit between es and seismic moment m0 is given by the relationship es 1 6 10 5 m0 which yields 0 47 mpa as the average global value of apparent stress however the regression lines of both es ms and es m0 yield poor empirical predictors for the actual energy radiated by any given earthquake the scatter of data is more than an order of magnitude about each of the regression lines on the other hand global variations between es and mo while large are not random when subsets of es m0 are plotted as a function of seismic region and faulting type the scatter in data is substantially reduced the es m0 fits for many seismic regions and tectonic environments are very distinctive and a characteristic apparent stress c can be derived the lowest apparent stresses 3 0 mpa are associated with strike slip earthquakes that occur at oceanic ridge ridge transforms and in intraplate environments seaward of island arcs intermediate values of apparent stress 1 5 a 3 0 mpa are associated with strike slip earthquakes at incipient or transitional plate boundaries in general the dominant mode of failure for a tectonic environment is associated with the faulting type that has the lowest apparent stress an energy magnitude me can complement moment magnitude mw in describing the size of an earthquake me being derived from velocity power spectra is a measure of seismic potential for damage mw being derived from the low frequency asymptote of displacement spectra is more physically related to the final static displacement of an earthquake when earthquake size is ranked by moment a list of the largest events is dominated by earthquakes with thrust mechanisms when earthquake size is ranked by energy the list of the largest events is dominated by strike slip earthquakes

crustal deformation in the central ionian islands greece results from dgps and dinsar analyses 1995 2006 abstract ground deformation studies based on differential gps dgps and differential interferometric sar dinsar analyses have been conducted in the seismically active area of the central ionian islands local gps networks were installed in cephallonia 2001 and zakynthos 2005 the cephallonian network has been remeasured five times and zakynthos once as of july 2006 the studies have yielded detailed information regarding both local and regional deformations that are occurring in the area for lefkas island dinsar analysis march to september 2003 revealed 56 mm of uplift in the central and western parts and is attributed to the august 2003 earthquake mw 6 3 that occurred offshore to the west synthetic dinsar modelling of the magnitude and extent of deformation is consistent with the seismologically deduced parameters for the ruptured segment along the lefkas transform fault subsidence for cephallonia island dinsar analysis 1995 to 1998 indicated ground deformation up to 28 mm located in small sections of the island further interferometric analysis for the period 2003 to 2004 encompassing the occurrence of the lefkas earthquake in august 2003 indicated 28 mm of uplift in the northern part while during the next two years 2004 to 2005 further uplift of at least 56 mm had taken place at the western and northern part of the island dgps measurements for the period 2001 to 2006 revealed a clockwise rotation of the island with respect to a centrally located station on aenos mt the horizontal component of deformation generally ranged from 6 to 34 mm with the largest values at the western and northern parts of the island considering the vertical deformation two periods are distinguished the first one 2001 to 2003 is consistent with anticipated motions associated with the main geological and tectonic features of the island the second one 2003 to 2006 has been tentatively attributed to dilatancy in which relatively small uplift 20 40 mm occurred along the southern and southeastern parts of the island while larger magnitudes 50 mm happened at the western part paliki peninsula these large magnitudes of uplift over an extended area 50 km in conjunction with an accelerated benioff strain determined from the analysis of the seismicity in the broader region are consistent with dilatancy this effect commenced some time after 2003 and is probably centered in the area between zakynthos and cephallonia if this interpretation is correct it may foreshadow the occurrence of a very strong earthquake s sometime during 2007 to 2008 in the above designated region

transition from collision to subduction in western greece the katouna stamna active fault system and regional kinematics transition from subduction to collision occurs in western greece and is accommodated along the downgoing plate by the kefalonia right lateral fault that transfers the hellenic subduction front to the apulian collision front here we present an active tectonic study of aitolo akarnania western greece that highlights how such a transition is accommodated in the overriding plate based on new multi scale geomorphic and tectonic observations we performed an accurate active fault trace mapping in the region and provide evidence for active normal and left lateral faulting along the katouna stamna fault ksf a 65 km long nnw striking fault system connecting the amvrakikos gulf to the patras gulf we further show that the cenozoic hellenide thrusts located west of the ksf are no longer active either in field observation or in gps data leading us to propose that the ksf forms the northeastern boundary of a rigid ionian islands akarnania block iab cosmic ray exposure measurements of 10be and 36cl were performed on a quaternary alluvial fan offset along the ksf 50 m left lateral offset a maximum abandonment age of 12 14 ka for the alluvial fan surface can be determined giving an estimated ksf minimum geological left lateral slip rate of 4 mm year 1 in agreement with high gps slip rates 10 mm year 1 despite this high slip rate the ksf is characterized by subdued morphological evidence of tectonic activity a gypsum breccia bedrock and a low level of seismicity suggesting a dominantly creeping behavior for this fault finally we discuss how the iab appears to have been progressively individualized during the pleistocene younger than 1 5 ma

pleistocene fluctuations in the western boundary undercurrent on the blake outer ridge the mean grain size of the detrital silt fraction was analyzed in two piston cores from the crest of the blake outer ridge using electronic particle analysis the resultant profiles in the two cores are highly correlatable and are interpreted to reflect the paleospeed of the western boundary undercurrent wbuc for the past 90 kyr the record can be divided into three periods the first encompasses the past 12 000 years and begins with an abrupt acceleration marking the transition from slow glacial to more vigorous holocene conditions the later holocene is a period of strong but variable flow the second period extends from 30 to 12 10 years and is characterized by a steady reduction of wbuc strength through the last ice age the current continued to decelerate until 12 10 years when the polar front finally retreated northward past the passages connecting the norwegian sea to the north atlantic the third period from 30 to about 90 10 years was a time of strong and variable flow that was independent of the glacial interglacial signal that is seen in the oxygen isotope record during this time the core of maximum flow appears to have shifted up and down the flank of the blake outer ridge and may have been influenced as much by salinity as by temperature variations in the source areas of the wbuc

the irpinia italy 1980 earthquake detailed analysis of a complex normal faulting a detailed analysis of near source strong motion and leveling data together with the results of teleseismic waveform modeling by westaway and jackson 1987 and aftershock studies by deschamps and king 1984 allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude ms 6 9 november 23 1980 irpinia earthquake southern italy the three main rupture episodes starting at about 0 20 and 40 s are here associated with better constrained source parameters than in previous studies we first evaluated the triggering time for the 11 closest accelerometers by using the well recorded 40 s strong motion phases this gave the absolute time and location of the dominant episodes of faulting the first rupture propagated mainly toward the northwest on a ne dipping normal fault at a mean velocity close to 3 km s for about 20 km and continued 15 km further on smaller subfaults it was associated with surface breakage in the southeastern part the second rupture started from the southeastern end of the first rupture about 18 s after it and propagated about 20 km toward the southeast on a low angle normal fault dipping 20 ne it was associated with secondary faulting on steeper planes reaching the surface the third and last episode at 39 s nucleated near the first hypocenter at shallower depth and the rupture possibly propagated on a 10 to 15 km long normal fault striking se antithetic to the first activated fault a clear correlation appears between the strength of the geological formations and the existence of surface breakage and shallow aftershock activity

the 2014 cephalonia earthquakes finite fault modeling fault segmentation shear and thrusting at the nw aegean arc greece we present refined finite fault models ffm for the 2014 cephalonia keffalinia kefalonia seismic sequence mw 6 0 at the nw edge of the aegean arc ionian sea the area represents the seismically most active part of europe and a continental promontory in which fault modeling is a challenge because of structural complexity and poor coverage by seismological gps and insar data inversion was based on gps data and a new algorithm permitting fusion of slip vectors of individual earthquakes and of their cumulative dislocation and accepting constraints and collocation type analysis of uncertainties computed ffm which correspond to an essentially strike slip fault and a blind shallow oblique slip thrust were assessed by sensitivity analysis and insar data and are consistent with the tectonic fabric of the area they can also explain the observed extreme peak ground accelerations the 2014 faults in combination with ffms of the 2003 and 2015 leucas lefkada lefkas earthquakes farther ne and of the 1983 m7 0 earthquake farther sw constrain a 100 km long immature strike slip fault zone along close to the cephalonia leucas coasts this fault pattern previously regarded as a poorly documented cephalonia transform fault consists of occasionally overlapping oblique slip segments with variable geometric and kinematic characteristics in a shear zone landwards of the plate interface as evidence from seismic profiles reveals this pattern may explain the enigmatic superimposition of shear and compression in the nw edge of the aegean arc

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

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

from earthquake centroid to spatial temporal rupture evolution mw 6 3 movri mountain earthquake june 8 2008 greece 1 we propose a new strategy to reveal the spatial temporal evolution of the earthquake rupture process from near regional data without assuming a constant rupture velocity the approach is based on a conjugate gradient method for which we express analytically the required waveform misfit derivative with respect to slip on the fault the derivative is given by back propagation of residual seismograms towards the source a good initial source approximation is necessary being obtained from hypocenter location and centroid moment tensor solution the iterative approach then gradually reveals major characteristics of the source process as an application we investigate a line source model of a damaging mw6 3 earthquake in greece revealing predominantly unilateral rupture propagation and two or three main slip patches one of which being significantly delayed indicating a temporary rupture arrest the region of largest slip coincides with the region of least abundant aftershocks between hypocenter and centroid the method has application potential for shakemaps emergency response and or aftershock hazard assessment

particle mixing rates in deep sea sediments determined from excess 210pb and 32si profiles particle mixing rates have been determined for 5 south atlantic antarctic and 3 equatorial pacific deep sea cores using excess 210 pb and 32 si measurements radionuclide profiles from these siliceous calcareous and clay rich sediments have been evaluated using a steady state vertical advection diffusion model in antarctic siliceous sediments 210 pb mixing coefficients 0 04 0 16 cm 2 y are in reasonable agreement with the 32 si mixing coefficient 0 2 or 0 4 cm 2 y depending on 32 si half life in an equatorial pacific sediment core however the 210 pb mixing coefficient 0 22 cm 2 y is 3 7 times greater than the 32 si mixing coefficient 0 03 or 0 07 cm 2 y the difference in 210 pb and 32 si mixing rates in the pacific sediments results from 1 non steady state mixing and differences in characteristic time and depth scales of the two radionuclides 2 preferential mixing of fine grained clay particles containing most of the 210 pb activity relative to coarser particles large radiolaria containing the 32 si activity or 3 the supply of 222 rn from the bottom of manganese nodules which increases the measured excess 210 pb activity relative to 226 ra at depth and artificially increases the 210 pb mixing coefficient based on 32 si data and pore water silica profiles dissolution of biogenic silica in the sediment column appears to have a minor effect on the 32 si profile in the mixed layer deep sea particle mixing rates reported in this study and the literature do not correlate with sediment type sediment accumulation rate or surface productivity based on differences in mixing rate among three antarctic cores collected within 50 km of each other local variability in the intensity of deep sea mixing appears to be as important as regional differences in sediment properties

suspended particulate matter transport through the vema channel richardson m j biscaye p e gardner w d and hogg n g 1987 suspended particulate matter transport through the vema channel mar geol 77 171 184 sixteen month time series measurements of water velocity and light scattering were coupled with hydrographic and suspended particulate matter sections to determine the flux and the variability in flux of suspended particulate matter through the vema channel the northward flux of spm through the vema channel ranged from 3 to 10 5 104 g s 1 with a mean of 6 5 104 g s 1 the largest fluxes were measured in the deepest and eastern portions of the channel with maximum fluxes of suspended particulate matter at specific sites being roughly two to four times the mean flux some of the suspended particulate matter in the channel may be eroded from the channel itself by the swift currents or eddy like features however the known manganese encrustation and hard floor of the channel suggest that the deep channel floor is not a likely source of sediment a primary source of the suspended particulate matter in the channel may be the sediment drifts in the argentine basin with their associated high standing crops of resuspended particulate matter this resuspended material would then be transported by the antarctic bottom water into and through the vema channel into the brazil basin the northward flux of suspended particulate matter through the vema channel is presently a significant but not dominant influence on sedimentation in the brazil basin

thrust sequences in the central part of the external hellenides the model of a foreland propagating sequence already presented for the external hellenides is significantly modified in this paper new data are used including structural maps cross sections stratigraphic determinations and seismic profiles in general thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time thus during the middle eocene the pindos thrust resulted in the formation of the ionian gavrovo foreland and acted in tandem with the newly formed gavrovo thrust within the basin until the late oligocene the gavrovo thrust consists of segments showing that out of sequence thrusting was important thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the ionian gavrovo foreland basin shortening rates within the gavrovo ionian foreland are low about 1 mm year although thrust load played an important role in the formation of this basin the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting

seismicity associated with the sumatra andaman islands earthquake of 26 december 2004 the u s geological survey national earthquake information center usgs neic had computed origins for 5000 earthquakes in the sumatra andaman islands region in the first 36 weeks after the sumatra andaman islands mainshock of 26 december 2004 the cataloging of earthquakes of m b usgs 5 1 and larger is essentially complete for the time period except for the first half day following the 26 december mainshock a period of about two hours following the nias earthquake of 28 march 2005 and occasionally during the andaman sea swarm of 26 30 january 2005 moderate and larger m b 5 5 aftershocks are absent from most of the deep interplate thrust faults of the segments of the sumatra andaman islands subduction zone on which the 26 december mainshock occurred which probably reflects nearly complete release of elastic strain on the seismogenic interplate thrust during the mainshock an exceptional thrust fault source offshore of banda aceh may represent a segment of the interplate thrust that was bypassed during the mainshock the 26 december mainshock triggered a high level of aftershock activity near the axis of the sunda trench and the leading edge of the overthrust burma plate much near trench activity is intraplate activity within the subducting plate but some shallow focus near trench reverse fault earthquakes may represent an unusual seismogenic release of interplate compressional stress near the tip of the overriding plate the interplate thrust nias earthquake of 28 march 2005 in contrast to the 26 december aftershock sequence was followed by many interplate thrust aftershocks along the length of its inferred rupture zone

temporal variations of beam attenuation coefficient on the continental rise off nova scotia two separate time series observations of light transmission in the bottom water on the continental rise off nova scotia show fluctuations of light transmission in a wide range 0 50 transmission at 660 nm the range corresponds approximately to spm concentrations of 12 mg l to 150 g l the former is the maximum value determined by filtration biscaye 1980 and the latter is determined by an empirical relation between beam attenuation coefficient and particle volume determined by a particle counter nepheloid layers of significant turbidity called benthic storms were observed in 30 and 10 of the time respectively for the two observations and each storm lasted 2 5 days high frequency fluctuations represented by pulse lengths less than 10 min were observed superimposed on the low frequency fluctuations during 16 and 4 of the time both the major storms and the high frequency pulses are interpreted to be a result of resuspension of bottom sediments at varying distances from the instrument the high frequency pulses are thought to be a result of erosion at a relatively short distance while the low frequency fluctuations result from erosion at greater distance

determination of sediment provenance at drift sites using hydrogen isotopes and unsaturation ratios in alkenones the large 20 hydrogen isotopic gradient in surface waters of the northwest atlantic ocean is exploited to track changes in the source of alkenones to the bermuda rise sediment drift cultures of the predominant alkenone producing coccolithophorid e huxleyi were grown in deuterium enriched seawater and shown to possess alkenones with a d h ratio that closely tracked the water d h ratio r 2 0 999 n 5 isotopic enrichments with a fractionation factor between 0 732 and 0 775 a hydrogen isotopic depletion of 193 3 n 9 was measured in alkenones from suspended particles relative to seawater in the subpolar and subtropical northwest atlantic ocean this value was used to calculate the water d values in which alkenones from bermuda rise sediment were synthesized and by extension the water mass in which they were produced applying this technique we find that 60 to 100 of the alkenones in late holocene bermuda rise sediment were produced in deuterium depleted subpolar water to the northwest of the drift to reconcile values of the alkenone unsaturation ratio u k 37 a widely used proxy for sea surface temperature with the d values of alkenones in late holocene sediments from the bermuda rise at least three sources of sediment must be invoked a cold very isotopically depleted source almost certain to be the scotian margin a warm moderately isotopically depleted source likely to be the northwestern edge of the subtropical gyre and a cold isotopically enriched source which we hypothesize to be the subpolar waters overlying the main branch of north atlantic deep water flowing southwest from the nordic seas copyright 2005 elsevier ltd paleoclimate records with sufficient length and temporal resolution to study the occurrence and causal mechanisms of abrupt climate change are exceedingly rare rapidly deposited ocean sediments provide the best archive for studying these events through geologic time but such sites in the open ocean are limited to sediment drift deposits such as the bermuda rise in the northwest atlantic using multiple climate proxies in a single core is becoming more common in high resolution pa leoclimate investigations but a major potential concern for this approach arises from the possibility that the fine fraction of sediment e g 63 m and the climate proxies within it may represent conditions far from the deposition site here we propose and test the hypothesis that hydrogen isotope ratios of alkenones a class of lipids from phytoplankton may provide insight into the source of fine grained sediment because of their restricted sources broad geographic distri bution and excellent preservation properties alkenones are of particular interest in the emerging field of compound specific hydrogen isotopic analysis the sedimentary abundances ex tents of unsaturations and isotopic compositions of alkenones provide quantitative and near continuous records we isolated alkenones from cultured unicellular algae haptophyte emil iania huxleyi surface ocean particulate material and open ocean sediments to determine the extent and variability of hydrogen isotopic fractionation in the di tri and tetraunsat urated c37 compounds we then compared the d values of the alkenones in surface sediments between the bermuda rise and the scotian margin above which a large 20 d gradient exists we determined the fractionation between alkenones from suspended particulate samples and the water in which the phytoplanton lived and examined the variability of alkenone d values during the medieval warm period little ice age climate transition cf keigwin 1996 at the bermuda rise

energetic rupture coseismic and post seismic response of the 2008 mw 6 4 achaia elia earthquake in northwestern peloponnese greece an indicator of an immature transform fault zone summary the 2008 june 8 moment magnitude mw 6 4 crustal earthquake in northwestern peloponnese greece was a strong shaking dextral strike slip event with teleseismic broad band and high frequency energy magnitudes me of 6 8 and 7 2 respectively a high stress drop 5 10 times the global average is associated with excessive high frequency energy the ne sw trending fault plane shown by the aftershock distribution and focal mechanism is not associated with previously mapped faults and no obvious coseismic surface rupture was discovered contrasting the enhanced rupture energy the event created no substantial coseismic or post seismic surface deformation likely due to a fault buried below a detached thick and compositionally weak flysch layer comparative spatial analysis including over 30 regional strike slip events between 1965 and 2009 reveals a ne sw striking diffuse transform fault zone subparallel to the cephalonia transform fault the dextral sense of motion along the transform zone is consistent with the ongoing global positioning system gps derived deformation along the west hellenic arc and the motion on the cephalonia transform fault characterizing this system is important to constraining the seismic hazard near patras a major port city immediately ne of the 2008 event

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

synergy of tectonic geomorphology applied geophysics and remote sensing techniques reveals new data for active extensional tectonism in nw peloponnese greece abstract in tectonically active areas such as in the northwest peloponnese of western greece geomorphic processes are strongly influenced by active faulting in many cases such faults cannot be easily identified in this paper we apply multidisciplinary analysis morphotectonic indices neotectonic mapping geophysical surveys and remote sensing techniques to map the recently recognized east west trending pineios river normal fault zone with a high degree of accuracy and to better understand its contribution to the evolution of the ancient region of elis during holocene time fault activity seems to be related to frequent changes in river flow patterns and to displacements of the nearby shoreline we argue that fault activity is the main reason for migration of pineios river mouth as documented for several time periods during historical time quantitative constraints on deformation caused by the faulting were applied through the application of the morphotectonic indices proposed in this paper including drainage network asymmetry and sinuosity and mountain front sinuosity all of which indicate that this is a highly active structure slip rates calculated to be as high as 0 48 mm yr for the last 209 ka based on previously published dating were verified by applied geophysical methods the fault surface discontinuity was identified at depth using vertical electrical resistivity measurements and depositional layers of different resistivity were found to be clearly offset displacement increases toward the west reaching an observed maximum of 110 m the most spectacular landform alteration due to surface deformation is the north south migration of the river estuary into completely different open sea areas during the late quaternary mainly during the holocene the sediment transport path has been altered several times due to these changes in river geometry with and the most recent seeming to have occurred almost 2000 years ago the river estuary migrated to its contemporary position along the southern coast settled on the hanging wall inducing retrograding of the northern coast and settled on the foot wall with rates reaching the order of 0 52 m yr as concluded from historical and recently acquired remote sensing data

chemical characterization of individual particles from the nepheloid layer in the atlantic ocean abstract particulate matter samples filtered from near bottom 30 liter water samples collected during the geosecs atlantic cruise were analyzed by the computer evaluated scanning electron microscope image cesemi 2 system this system permitted automated discrete particle analysis for the elements al si p s k ca and fe by energy dispersive x ray spectrometry and for particle size approximately 2000 particles in the size range 1 20 m representative of several milliliters of seawater were analyzed per sample and yielded discrete size and chemical analysis of the major classes of particulate matter opal calcium carbonate and clay as well as some regularly occurring subclasses of clay and other minor classes the distributional patterns of the major classes matched both in chemistry and abundance their general distributional patterns in sediments clay particles reflected high and low latitude sources opal particles patterns of diatom productivity and carbonate patterns of productivity as well as the calcite saturation chemistry of the water column superimposed on these features was evidence for long range transport of particles in well defined bottom water masses such as the antarctic bottom water such transport is believed to occur through a series of resuspension events in which case particle distributions match the properties of the sediments cases were found where near bottom particles did not match the sediments especially in quiescent environments

biological activity and associated sedimentary structures in hebble area deposits western north atlantic abstract biological and sedimentologic samples along with x radiographs of sediment slabs were taken from box cores in the hebble area 4700 m on the lower continental rise of nova scotia these data suggest that this bottom region is influenced by periods of strong near bottom currents which erode and physically transport sediments these high periods alternate with periods of weaker flow biogenic reworking of sediments by an active benthic infauna dominates particle transport during low flow conditions

a study of the optical characteristics of the suspended particles in the benthic nepheloid layer of the scotian rise light transmission profiles have been used to study the optical properties of the suspended particles which are characteristic of the area of the scotian rise in the north atlantic ocean this area is typified by very strong bottom currents and a highly variable bedform morphology a good correlation r 0 96 has been found between the suspended volume and the light beam attenuation coefficient this correlation is consistent with the fact that the cumulative slope of the hyperbolic particle size distribution is nearly constant throughout the region slope 3 1 0 3 numerical analysis of the optical data in conjunction with particle size analysis yields values of the index of refraction of the suspended particles of 1 20 0 07 relative to water the conclusion drawn from these results is that the scotian rise benthic zone is characterized by suspended particles of high relative index of refraction and size distributions which do not vary much with altitude above bottom or over periods of time of more than a year in spite of the extensive fluctuations in activity of the region

long term in situ calculations of kinetic energy and reynolds stress in a deep sea boundary layer long term measurements of reynolds stress and kinetic energy are necessary to characterize the bottom boundary layer during storms which transport sediment in the high energy benthic boundary layer experiment area on the nova scotia rise the benthic acoustic stress sensor current meter system employed an on board microcomputer to process 2 hz velocity vector data into 20 min averages of velocity vectors and the turbulent reynolds stress tensor the data indicate a bottom boundary layer which is usually transitional with bottom roughness scaling between viscous z0 v 9u and rough z0 ks 30 during the periods of transitional flow the logarithmic layer was not a useful indicator of boundary stress direct stress and energy measurements showed that the stress was much less than that indicated by the slope of the transitional mean logarithmic velocity profile several westward high velocity events which were modulated by a significant tidal component were recorded it appears from this data set that the mean westward flow must be accompanied by a train of internal tidal waves to achieve the velocities necessary to be the sediment transport events identified as benthic storms

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge