western hellenic subduction and cephalonia transform local earthquakes and plate transport and strain abstract focal parameters of local earthquakes in the region of the ionian islands of western greece are constrained with a temporary dense array of three component seismographs operated jointly offshore and onshore seismic deformation is documented to be confined to the east of the n20 e striking steep continental slope west of cephalonia island the right lateral cephalonia transform fault ctf inferred from large earthquakes the pre apulian continental material appears to be only deforming east of the transform fault where it is in upper plate position to the hellenic subduction east of the transform fault the transmission velocity tomography from local earthquakes compared in depth section with a previous marine reflection profile provides evidence in support of a shallow landward dipping boundary around 12 km deep under the ionian islands along which they may override the lower plate on either side of this interface local earthquakes occur with different focal mechanisms in support with its interpretation as the interplate under cephalonia island reverse faulting deforms the upper plate along nw se structures which may also be affected by left lateral bookshelf faulting small earthquakes show normal faulting along the western coast of cephalonia and its extension 20 km ssw the trace of the ctf as inferred from the occurrence of the large strike slip earthquakes another group of normal fault earthquakes locates in the lower plate from under cephalonia to zante just outboard of a possible change of interplate dip suggested from reflection seismics landward under the islands these normal fault earthquakes appear to coincide in position with that of the load imposed by the upper plate transported over them rather than occurring in an outer rise outboard the plate boundary and trench as observed in other subductions and attributed to the control by the flexural bending of the lower plate under the pull of the sinking slab interpretation has to consider several peculiar features of plate interaction in western greece with respect to a steady state model for major subduction zones in particular a fast deformation of the upper plate in front of an orogenically overthickened crust and of the southwestward push of extruding anatolia its transport which is the cause of the migration of the plate boundary rather than the roll back of a slab which has been proposed to be detached possibly a flat and ramp shape of the interplate the geometrical complexity of the shear limit across the ctf between subduction and collision and the nearby variation of the nature of the foreland crust

earthquake mechanisms of the adriatic sea and western greece implications for the oceanic subduction continental collision transition summary we present 21 focal solutions magnitude 5 5 reliably computed by body wave modelling for the western hellenic arc from yugoslavia to the southern peloponnese mechanisms located within the aegean show normal faulting the t axis trending n s in the centre and parallel to the active boundary in the external part mechanisms associated with the keffalinia fault are consistent with dextral strike slip motion reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary continental collision or oceanic subduction the consistency in azimuth of the slip vectors and of the gps velocity relative to africa all along the active boundary suggests that the deformation is related to the same motion the discrepancy between seismic energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic the northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction

rutile solubility in albite h2o and na2si3o7 h2o at high temperatures and pressures by in situ synchrotron radiation micro xrf abstract rutile is an important mineral host for high field strength elements so its solubility in geologic fluids at high pressure and temperature plays an important role in the crustal and mantle processes that control the terrestrial cycling of these elements however experimental measurements of rutile solubility are in conflict by a factor of more than 100 at most studied conditions we performed new measurements of rutile solubility in h 2 o albite and h 2 o na 2 si 3 o 7 ns3 fluids by in situ synchrotron radiation x ray fluorescence spectroscopy using modified bassett type hydrothermal diamond anvil cells minimum detection limits were 1 9 and 2 3 ppm ti by weight for the two cells three albite h 2 o experiments at starting bulk compositions of 2 7 6 7 and 10 3 wt albite involved spectral acquisition at rutile saturation in the presence of albite crystals melt or a single homogeneous fluid phase after accounting for the additional phases corrected fluid compositions were 0 6 to 7 5 wt dissolved silicate over the run conditions at 2 7 wt albite rutile dissolution rate was slow and steady state was not achieved at 600 800 c however at higher dissolved albite contents constant solubility with time was observed rutile solubilities in the presence of a single fluid phase at 700 c 0 79 gpa 5 4 wt albite and at 800 c 1 10 gpa 6 7 wt albite were 37 2 and 156 6 ppm respectively these data agree with results acquired using hydrothermal piston cylinder methods with long run times and suppression of new crystal growth but not with data derived from visual observation in hydrothermal diamond anvil cells this discrepancy is likely due to lack of equilibrium in the latter approach two experiments in 10 and 30 wt ns3 at 660 800 c 0 5 0 1 gpa show extreme concentration dependent enhancement of rutile solubility to 4500 ppm the data indicate a strong positive correlation between rutile solubility and na al because na k al is likely to be greater than unity in aqueous fluids at high pressure and temperature due to incongruent dissolution of albite and micas the increase in rutile solubility along the albite ns3 join points to the possibility of significant ti transport by silicate bearing aqueous fluids in the lower crust and upper mantle

variation of seismic coupling with slab detachment and upper plate structure along the western hellenic subduction zone abstract the western hellenic subduction zone is characterized by a trenchward velocity of the upper plate in the ionian islands segment complete seismic coupling is achieved as is predicted by standard plate tectonic models in which there is no slab pull force because the slab has broken off the moderate local seismic moment rate relates to a shallow downdip limit for the seismogenic interface this characteristic may be attributed to the ductility of the lower crust of the upper plate which allows a decollement between the upper crust of the overriding plate and the subducting plate farther south a deeper downdip limit of the seismogenic interface is indicated by thrust faulting earthquakes which persist much deeper in western crete a correspondingly larger downdip width of this seismogenic zone is consistent with the suggested larger maximum magnitude of earthquakes here however since the seismic moment release rate seems to be moderate in the peloponnese and western crete like in in the ionian islands this seismically active interface cannot maintain complete seismic coupling across its larger downdip width a cause may be the lateral addition of overweight to the part of the slab still attached in crete by the free fall of its part that has broken off from the surface further north this increased slab pull reduces the compressive normal stress across the seismogenic interface and thus causes partial seismic coupling in its shallower part however the width of this part may provide an additional area contributing to slip in large earthquakes which may nucleate deeper on stick slip parts of the interface hints at anomalies in structure and seismicity which need to be resolved may relate to the present location of the edge of the tear in the slab

seismic investigation of the transition from continental to oceanic subduction along the western hellenic subduction zone 1 the western hellenic subduction zone whsz exhibits well documented along strike variations in lithosphere density i e oceanic versus continental subduction rates and overriding plate extension differences in slab density are believed to drive deformation rates along the whsz however this hypothesis has been difficult to test given the limited seismic constraints on the structure of the whsz particularly beneath northern greece here we present high resolution seismic images across northern and southern greece to constrain the slab composition and mantle wedge geometry along the whsz data from two temporary arrays deployed across greece in a northern line nl and southern line sl are processed using a 2d teleseismic migration algorithm based on the generalized radon transform images of p and s wave velocity perturbations reveal n60e dipping low velocity layers beneath both nl and sl the 8 km thick layer beneath sl is interpreted as subducted oceanic crust while the 20 km thick layer beneath nl is interpreted as subducted continental crust the thickness of subducted continental crust inferred within the upper mantle suggests that 10 km of continental crust has accreted to the overriding plate the relative position of the two subducted crusts implies 70 85 km of additional slab retreat in the south relative to the north overall our seismic images are consistent with the hypothesis that faster sinking of the denser oceanic portion of the slab relative to the continental portion can explain the different rates of slab retreat and deformation in the overriding plate along the whsz

subduction kinematics and dynamic constraints the kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings two reference frames are used here to describe the simple 2d kinematics of subduction zones in the first the upper plate is assumed fixed whereas in the second frame upper and lower plates move relative to the mantle relative to a fixed point in the upper plate u the transient subduction hinge h can converge diverge or be stationary similarly the lower plate l can converge diverge or be stationary the subduction rate vs is given by the velocity of the hinge h minus the velocity of the lower plate l vs vh vl the subduction rate 1 increases when h diverges and 2 decreases when h converges combining the different movements at least 14 kinematic settings can be distinguished along the subduction zones variable settings can coexist even along a single subduction zone as shown for the 5 different cases occurring along the apennines subduction zone apart from few exceptions the subduction hinge converges toward the upper plate more frequently along e or ne directed subduction zone whereas it mainly diverges from the upper plate along w directed subduction zones accompanying backarc extension before collision orogen growth occurs mostly at the expenses of the upper plate shortening along e ne directed subduction zones whereas the accretionary prism of w directed subduction zones increases at the expenses of the shallow layers of the lower plate the convergence shortening ratio is 1 along e or ne directed subduction zones whereas it is 1 along accretionary prisms of w directed subduction zones backarc spreading forms in two settings along the w directed subduction zones it is determined by the hinge divergence relative to the upper plate minus the volume of the accretionary prism or in case of scarce or no accretion minus the volume of the asthenospheric intrusion at the subduction hinge since the volume of the accretionary prism is proportional to the depth of the decollement plane the backarc rifting is inversely proportional to the depth of the decollement on the other hand along e or ne directed subduction zones few backarc basins form e g aegean andaman and can be explained by the velocity gradient within the hangingwall lithosphere separated into two plates when referring to the mantle the kinematics of subduction zones can be computed either in the deep or in the shallow hotspot reference frames the subduction hinge is mostly stationary being the slab anchored to the mantle along w directed subduction zones whereas it moves w or sw ward along e or ne directed subduction zones surprisingly along e or ne directed subduction zones the slab moves out of the mantle i e the slab slips relative to the mantle opposite to the subduction direction kinematically this subduction occurs because the upper plate overrides the lower plate pushing it down into the mantle as an example the hellenic slab moves out relative to the mantle i e sw ward opposite to its subduction direction both in the deep and shallow hotspot reference frames in the shallow hotspot reference frame upper and lower plates move westward relative to the mantle along all subduction zones this kinematic observation casts serious doubts on the slab negative buoyancy as the primary driving mechanism of subduction and plate motions w directed subduction zones rather provide about 2 3 times larger volumes of lithosphere re entering into the mantle and the slab is pushed down this opposite behavior is consistent with the down dip extension seismicity along e ne directed subduction zones and the frequent down dip compression along the w directed subduction zones subduction kinematics shows that plate velocity is not dictated by the rate of subduction along the w directed subduction zones the rate of subduction is rather controlled i by the hinge migration due to the slab interaction with the easterly trending horizontal mantle wind along the global tectonic mainstream ii by the far field plate velocities and iii by the value of negative buoyancy of the slab relative to the country mantle alternatively e ne nne directed subduction zones have rates of sinking chiefly determined i by the far field velocity of plates and ii by the value of negative buoyancy of the slab relative to the country mantle along this type of subduction the subduction hinge generally advances e ne ward toward the upper plate decreasing the subduction rate but it moves w sw ward relative to the mantle all this indicates that subduction zones have different origin as a function of their geographic polarity and the subduction process is more a passive feature rather than being the driving mechanism of plate motions a rotational component combined with mantle density and viscosity anisotropies seems more plausible for generating the global tuning in the asymmetry of subduction zones

building a three dimensional model of the active plio quaternary basin of argostoli cephalonia island greece an integrated geophysical and geological approach abstract this work is a multidisciplinary approach from geological and geophysical surveys to build a 3d geological model of argostoli basin cephalonia island greece aiming to be used for computational 3d simulation of seismic motion cephalonia island is located at the north western end of the aegean subduction frontal thrust that is linked to the dextral cephalonia transform fault west of cephalonia where the seismic hazard is high in terms of earthquake frequency and magnitude the plio quaternary koutavos argostoli basin site was selected within the french research agency pia sinaps project www institut seism fr projets sinaps last accessed on november 25th 2019 to host a vertical accelerometer array the long term goal is to validate three dimensional nonlinear numerical simulation codes to assess the site specific amplification and nonlinearity herein the geological and geophysical surveys carried out from 2011 to 2017 are presented and in particular the complementary investigations that led to the identification of the main stratigraphic units and their structures in addition coral debris sampled from the vertical array deep borehole cores were used for 230th 234u measurements which confirmed the pleistocene age of the koutavos basin the characterization of the three dimensional structure of the stratigraphic units was achieved by coupling geological cross sections i e depth geometry and geophysical surveys based of surface wave analysis

the oceanic nature of the african slab subducted under peloponnesus thin layer resolution from multiscale analysis of teleseismic p to s converted waves summary in the hellenic subduction zone the lithospheric slab may comprise continental and oceanic units juxtaposed downdip and along strike for stations along eastern peloponnesus teleseismic p wave receiver function rf processing in the standard frequency band produces an image of a low velocity layer lvl at the top of the slab apparently twice thicker than for an oceanic crust to assess if this could come from a lack of resolution of the standard processing we develop a multiscale approach with the rfs based on the wavelet response of the medium akin to the wavelet transform of the velocity depth function the synthetic response in conversion is obtained for a multiscale singularity formed by two opposite velocity steps at the boundaries of a crust embedded in mantle material this indicates that only wavelet periods shorter than about 0 8 s will allow to identify clearly a 7 km thin oceanic crust going to longer periods leads to underestimate or overestimate the time thickness of the lvl due to interference phenomena the analysis of the response in conversion from full waveform synthetic seismograms in a dipping slab model validates a multiresolution approach to real observations with earthquakes of broad enough spectrum towards high frequencies yielding energy to provide wavelet periods significantly shorter than 1 s the p to s conversions obtained allow us to resolve for the first time a standard oceanic crust at the slab top beneath the eastern coast of peloponnesus this documents the subduction of a purely oceanic slab of most reduced buoyancy since 4 5 myr under the rapidly southwestward extending upper plate continental material

late cenozoic deformation of the hellenide foreland western greece the late cenozoic structural evolution of western greece involved the shortening of mesozoic passive continental margin and cenozoic foreland basin sequences in a foreland propagating fold and thrust system and superimposed neotectonic deformation related to the development of an active island arc although the pre apulian zone has been regarded as the undeformed western foreland to the thrust belt three dimensional exposures in the ionian islands of kephalonia and zakinthos afford evidence of significant late neogene and quaternary shortening including thrusting on reactivated normal faults time relations and fault kinematics show that these structures are compatible with the westward migration of the locus of hellenide thrusting beyond its previously recognized limit and outer arc compression related to active subduction the presence of the pre apulian zone in the west contrasts with other aegean foreland areas where no such intermediate block lay between the thrust pile and old mesozoic oceanic crust consequently the pre apulian block took up continued hellenide shortening in the late miocene while oceanic crust was being overridden subducted in southern parts of the arc to the east the pre apulian zone subsequently overrode the ocean floored ionian sea during the late neogene the confusion in determining driving mechanisms for late cenozoic deformation in western greece and the apparent conflict between evidence for the age of initial subduction in different parts of the arc are explained by this model which is consistent with regional considerations including structuration in adjacent areas and important paleomagnetic rotations in the arc

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

single bubble marine source offers new perspectives for lithospheric exploration abstract we present deep penetration seismic time sections obtained in the last two years with the single bubble pulse generating method using marine seismic airguns whole crustal penetration and resolution have been obtained on the ionian quasi oceanic basin and its margin on the continental crust of the aegean sea on the continental margins and oceanic basin of the gulf of biscay we show that this method is more efficient than others in radiating the lower frequencies returned by deep structure without loosing resolution hence it allows deep crustal imaging from relatively low power academic ships and if the method is applied to powerful industrial vessels it may open the subcrustal lithosphere to imaging

moho topography under central greece and its compensation by pn time terms for the accurate location of hypocenters the example of the gulf of corinth 1995 aigion earthquake abstract in this paper we expand over the whole of central greece the moho map centered on the gulf of corinth from tomographic inversion of pmp traveltime profile data recorded by several tens of temporary stations our approach is based on pn moho refracted waves from a large regional earthquake recorded by both temporary stations and the permanent hellenic network the moho map shows the large moho depth under the hellenides belt it also highlights the shallower moho domain towards the aegean sea south and east of the corinth gulf the domain of shallow moho is limited along a ne sw prolongation ahead of the north anatolian fault from the north aegean trough to the western tip of the gulf of corinth towards the gulf of patras the pn time terms provide corrections for the permanent stations that can be used together with the 1d velocity depth model for a first order compensation of lateral heterogeneity and contribute to the accurate and fast location of earthquake hypocenters as a test we relocated the 1995 aigion earthquake in this way using only the sparse data of the permanent stations hypocentral coordinates then shift close to those derived by a dedicated dense array deployed after the earthquake implying improvement of the routine location

seismic coupling and structure of the hellenic subduction zone in the ionian islands region abstract the western hellenic arc has been commonly considered as a largely aseismic subduction zone from the comparison of a small rate of shortening derived from the seismic moment release with a large rate of convergence inferred from geology complete seismic coupling would instead be expected from models that consider a control by plate tectonic forces because of the trenchward velocity of the hellenic aegean upper plate now confirmed with gps measurements in the region of the ionian islands a subduction interplate boundary has been recently imaged and its seismogenic downdip width suggested to be moderate from reflection seismic profiling and local earthquake tomography in the appropriate model for such an earthquake source region which considers a single interplate fault and takes into account these features the moderate seismic moment release is found consistent with complete seismic coupling of this subduction the shallow downdip limit of the seismogenic zone can be interpreted as due to the interplate boundary being overlain there by the ductile deeper crust of the orogenically thickened hellenides

stratigraphic evolution and source rock potential of a lower oligocene to lower middle miocene continental slope system hellenic fold and thrust belt ionian sea northwest greece the western flanks of the hellenic fold and thrust belt are similar to the nearby prolific albanian oil and gas provinces where commercial volumes of oil have been produced the lower oligocene to lower middle miocene slope series at this part of the hellenic fold and thrust belt provides a unique opportunity to evaluate the anatomy and source rock potential of such a system from an outcrop perspective slope progradation is manifested as a vertical pattern exhibiting an increasing amount of sediment bypass upwards which is interpreted as reflecting increasing gradient conditions the palaeoflow trend exhibits a western direction during the late oligocene but since the early miocene has shifted to the east the occurrence of reliable index species allowed us to recognize several nannoplankton biozones np23 to nn5 organic geochemical data indicate that the containing organic matter is present in sufficient abundance and with good enough quality to be regarded as potential source rocks the present rock eval ii pyrolytic yields and calculated values of hydrogen and oxygen indexes imply that the recent organic matter type is of type iii kerogen a terrestrial origin is suggested and is attributed to short transportation distance and accumulation at rather low water depth the succession is immature with respect to oil generation and has not experienced high temperature during burial however its eastern down slope equivalent deep sea mudstone facies should be considered as good gas prone source rocks onshore since they may have experienced higher thermal evolution in addition they may have improved organic geochemical parameters because there is no oxidization of the organic matter

seismic structure and the active hellenic subduction in the ionian islands in the region of the ionian islands of western greece the active margin of the hellenic domain passes from oceanic subduction in the south to continental collision in the north linked by the right lateral cephalonia transform fault a slightly landward dipping interface revealed at 13 km depth by a single previous line in the channel between cephalonia and zante has been suggested as the interplate subduction boundary new marine multichannel reflection profiles and obs refraction and wide angle reflection data confirm the reflector as a regional feature these data evidence its extension to the south where large low angle thrust earthquakes occur offshore to zante the new profiles establish a coincidence between the focal depths of these large subduction events and the imaged bright reflective level confirming its tentative interpretation as the interplate boundary which generally appears with a positive reflection polarity in this context the ionian islands outcrop corresponds to a shallowing of the interplate boudary from south to north in the south offshore zante the interplate boundary comprises a stratified zone that may be considered as the sedimentary cover of the ionian basin oceanic like crust which forms the lower plate here the shallower position and single cycle reflection character of the interplate further north suggest that the lower plate could there be the apulian paleomargin to that basin

high resolution seismic imaging of the western hellenic subduction zone using teleseismic scattered waves summary the active hellenic subduction system has long been considered an ideal setting for studying subduction dynamics because it is easily accessible and of limited spatial extent it has been the focus of numerous seismological studies over the last few decades but nonetheless the detailed structure of both the slab and the surrounding mantle remain poorly constrained in an intermediate depth range from 30 to 150 km the objective of this paper is to fill this gap the intermediate depth regime is of particular interest because it is pivotal for improving our understanding of the dynamic interaction between subducting lithosphere and the surrounding mantle an interdisciplinary effort aimed at addressing this challenge is currently undertaken by the multidisciplinary experiments for dynamic understanding of subduction under the aegean sea medusa project as part of the medusa initiative a temporary array consisting of 40 densely spaced broad band seismometers from the iris passcal pool has been deployed in southern greece we process the teleseismic data recorded by this array with a migration algorithm based on the generalized radon transform to obtain high resolution images of the subduction zone in 2 d the images reveal a sharp mohoroviy discontinuity moho at depths ranging from 30 km beneath the western margin of the aegean sea to 40 km beneath the central peloponnesus where it outlines the crustal root of the hellenides to the west of the hellenides the continental moho is not identified but we interpret a pronounced discontinuity imaged at 20 km depth as the contact between low velocity sediments and high velocity crystalline basement the images also show the subducted oceanic crust as a low velocity layer that plunges at a constant angle of 21 from west to east the oceanic crust exhibits low velocities to at least 90 km depth indicating that the bulk of fluid transfer from the subducted slab into the mantle wedge occurs below this depth a detailed comparison of images constructed for distinct backazimuthal illuminations reveals deviations in the geometry of the subducted slab these deviations are attributed to structural and or compositional changes taking place directly to the north of the medusa array and are consistent with the existence of a slab tear beneath the central hellenic shear zone

synthetic fluid inclusions in natural quartz i compositional types synthesized and applications to experimental geochemistry synthetic fluid inclusions having a wide range of geologically applicable compositions in the c o h s na k ca cl cu fe system have been formed by healing fractures in inclusion free natural quartz and by precipitating new quartz overgrowths on an original seed crystal inclusion types synthesized include 1 1 liquid rich pure h2o inclusions of primary and secondary origin 2 2 pure h2o inclusions with the critical density 3 3 liquid rich inclusions containing undersaturated aqueous solutions of nacl or kcl or cacl2 or mixtures of the three salts 4 4 h2o nacl inclusions containing halite daughter minerals 5 5 h2o nacl kcl inclusions containing halite and sylvite daughter minerals 6 6 h2o co2 inclusions of various compositions containing liquid h2o and either co2 vapor or co2 liquid or both at 25 c 7 7 h2o co2 nacl inclusions containing an aqueous phase liquid and vapor co2 and halite at 25 c 8 8 c o h inclusions containing liquid h2o a co2 ch4 liquid phase and graphite daughter minerals at 25 c 9 9 h2o nacl inclusions that contain a chalcopyrite daughter mineral and 10 10 inclusions representing trapping of the coexisting immiscible fluids in the h2o nacl h2o co2 nacl and na c o h systems the inclusions exhibit uniform phase ratios at room temperature and the temperatures of various phase changes within individual inclusions agree with those predicted from experimental and theoretical data indicating that the inclusion fluid has the same composition and density as the parent solution these miniature autoclaves thus may be used to study various problems related to fluid inclusion research to calibrate analytical equipment used to study natural inclusions and to study phase equilibria solubility and pvt relations of a variety of chemical systems

intraslab deformation and rupture of the entire subducting crust during the 25 october 2018 mw 6 8 zakynthos earthquake

mapping an earthquake induced landslide based on uav imagery case study of the 2015 okeanos landslide lefkada greece abstract on november 17 2015 07 10 utc an earthquake of mw 6 5 induced slope failures mainly at the western part of the island of lefkada ionian sea greece the most characteristic one is the okeanos site deep seated landslide near village athani that affected the man made environment part of the site including a dirt road moved downwards along the coastal cliff and a luxury hotel suffered heavy damage the goal of this study is to map in detail the okeanos landslide and to provide relevant quantitative data i e structural data and volume of both the accumulated and removed material in order to achieve this a comparison between pre earthquake and post earthquake point clouds generated from aerial imagery and uav acquired photos took place using structure from motion the steep coastal cliff site was surveyed in detail even in areas that are difficult to approach results from this study show that the total landslide area covers a surface of 36 000 m2 while a removed volume of 93 000 m3 of landslide material was evaluated using change detection techniques in addition fieldwork and survey data revealed that the sliding surface was a pre existing fault surface upon which the geological material moved downwards the coastal cliff the sliding surface dips west and is exposed along a 115 m long and 25 30 m high section scarp as a conclusion this study underlines the importance of a thorough geological study in order to identify landslide prone areas prior to any building activity and shows that a uav survey is capable to provide adequate information during a post earthquake field survey for co seismic landslide mapping and modeling

experimental determination of trace element partitioning between pargasite and a synthetic hydrous andesitic melt in order to more fully establish a basis for quantifying the role of amphibole in trace element fractionation processes we have measured pargasite silicate melt partitioning of a variety of trace elements rb ba nb ta hf zr ce nd sm yb including the first published values for u th and pb experiments conducted at 1000 c and 1 5 gpa yielded large crystals free of compositional zoning partition coefficients were found to be constant at total concentrations ranging from 1 to 100 ppm indicating henry s law is oparative over this interval comparison of partition coefficients measured in this study with previous determinations yields good agreement for similar compositions at comparable pressure and temperature the compatibility of u th and pb in amphibole decreases in the order pb th u partial melting or fractional crystallization of amphibole bearing assemblages will therefore result in the generation of excesses in238u activity relative to230th similar in magnitude to that produced by clinopyroxene the compatibility of pb in amphibole relative to u or th indicates that melt generation in the presence of residual amphibole will result in the long term enrichment in pb relative to u or th in the residue this process is therefore incapable of producing the depletion in pb relative to u or th inferred from the pb isotopic composition of morb and oib comparison of partition coefficients measured in this study with previous values for clinopyroxene allows some distinction to be made between expected trace element fractionations produced during dry cpx present and wet cpx amphibole present melting rb ba nb and ta are dramatically less compatible in clinopyroxene than in amphibole whereas th u hf and zr have similar compatibilities in both phases interelement fractionations such as dnb dba are also different for clinopyroxene and amphibole changes in certain ratios such as ba nb ba th and nb th within comagmatic suites may therefore offer a means to discern the loss of amphibole from the melting assemblage elastic strain theory is applied to the partitioning data after the approaches of beattie and blundy and wood and is used to predict amphibole melt partition coefficients at conditions of p t and composition other than those employed in this study given values of dca dti and dk from previous partitioning studies this approach yields amphibole melt trace element partition coefficients that reproduce measured values from the literature to within 40 45 this degree of reproducibility is considered reasonable given that model parameters are derived from partitioning relations involving iron and potassium free amphibole

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

early orogenic deformation in the ionian zone of the hellenides effects of slab retreat and arching on syn orogenic stress evolution abstract in this work we report on early orogenic fracture patterns affecting a cretaceous to eocene sedimentary succession exposed in western greece these rocks belong to the cenozoic external hellenides which form the western portion of the aegean orocline the analysis of fracture type orientation and crosscutting relationships provides constraints on the stress and strain patterns during the early stages of orocline formation the fracture patterns in the study area includes early orogenic extensional fractures arranged into two mutually orthogonal sets these developed during progressive burial in the forebulge foredeep system ahead of the advancing compressive front tectonic solution seams at a high angle to bedding postdate these extensional structures solution seams are arranged in different sets oblique to each other and developed in the early stages of thrusting and folding extensional structures and solution seams are oblique to each other their orientation and crosscutting relationships provide evidence for clockwise vertical axis rotation of stress directions with time this is consistent with the progressive arching of the forebulge thrust belt system during progressive slab retreat

seismic reflection imaging of the subducting juan de fuca plate mckenzie and parker s early suggestion1 that the juan de fuca plate is underthrusting north america has since been confirmed by numerous studies evidence for plate convergence along this junction includes a sediment filled trench2 7 intense compressional deformation of the continental slope and shelf sediments2 7 seafloor magnetic anomalies that extend beneath the continental slope2 4 inland andesitic volcanoes8 paired low high heat flow and gravity anomalies9 10 active onshore deformation11 12 onshore crustal earthquakes with compressional axes parallel to the direction of plate convergence13 sinistral strike slip earthquakes along the nootka fault fig 1 14 and a well defined benioff wadati zone6 15 16 here we report the results of a seismic reflection survey that has delineated two slabs of oceanic lithosphere underlying vancouver island one that is currently being subducted and one that is underplated these findings lead us to speculate that successive underplating of oceanic lithosphere may be an important process in the evolution and growth of continents

very low solubility of rutile in h2o at high pressure and temperature and its implications for ti mobility in subduction zones the solubility of rutile in h2o has been measured at 1000 1100 c 1 2 gpa the data indicate that solubility is very low over the investigated range with a maximum of 4 7 millimol kg h2o at 1100 c 2 gpa the data were fit with the equation log m ti 4 892 10470 t 0 1923 p where m ti is ti molality t is in kelvins and p in gpa when compared to previous results the new data indicate substantially lower solubility opposite pressure dependence and thermodynamic properties of the reaction rutile tio2 aq that are now consistent with other oxide hydrolysis reactions calculations of ti transport during mantle metasomatism by h2o in subduction zone environments predict much lower ti mobility at all conditions these results offer strong support for models of ti retention in eclogites during slab devolatilization and require that examples of significant ti mass transfer be explained by complexing agents in solution most likely aluminosilicate complexes

the kephalonia transform fault and the rotation of the apulian platform evidence from satellite geodesy this paper describes a collaborative gps project to determine recent crustal movements and deformations across the ne ionian sea this region is characterized by rifting in the african foreland pelagian sea subduction along the calabrian and west hellenic arcs rotation of the italian peninsula and distributed normal faulting in central greece from gps campaigns on the ionian islands and in nw greece performed in 1989 and 1991 a kinematic field is deduced which is controlled by the deep trough following the nw coast of kephalonia island it is concluded that this prominent bathymetric feature resembles an active fault system kephalonia fault which has the signature of a right lateral transform fault

the seismic sequence of january february 2014 at cephalonia island greece constraints from sar interferometry and gps this article has been accepted for publication in geophysical journal internationa 2015 published by oxford university press on behalf of the royal astronomical society all rights reserved

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

regional focal mechanisms for earthquakes in the aegean area the distribution of the focal mechanisms of the shallow and intermediate depth h 40 km earthquakes of the aegean and the surrounding area is discussed the data consist of all events of the period 1963 1986 for the shallow and 1961 1985 for the intermediate depth earthquakes with m s 5 5 for this purpose all published fault plane solutions for each event have been collected reproduced carefully checked and if possible improved accordingly the distribution of the focal mechanisms of the earthquakes in the aegean declares the existence of thrust faulting following the coastline of southern yugoslavia albania and western greece extending up to the island of cephalonia this zone of compression is due to the collision between two continental lithospheres apulian eurasian the subduction of the african lithosphere under the aegean results in the occurrence of thrust faulting along the convex side of the hellenic arc these two zones of compression are connected via strike slip faulting observed at the area of cephalonia island the p axis along the convex side of the arc keeps approximately the same strike throughout the arc 210 nne ssw and plunges with a mean angle of 24 to southwest the broad mainland of greece as well as western turkey are dominated by normal faulting with the t axis striking almost ns with a trend of 174 for greece and 180 for western turkey the intermediate depth seismicity is distributed into two segments of the benioff zone in the shallower part of the benioff zone which is found directly beneath the inner slope of the sedimentary arc of the hellenic arc earthquakes with depths in the range 40 100 km are distributed the dip angle of the benioff zone in this area is found equal to 23 this part of the benioff zone is coupled with the seismic zone of shallow earthquakes along the arc and it is here that the greatest earthquakes have been observed m s 8 0 the deeper part inner of the benioff zone where the earthquakes with depths in the range 100 180 km are distributed dips with a mean angle of 38 below the volcanic arc of southern aegean

a traverse of the ionian islands front with coincident normal incidence and wide angle seismics abstract marine vertical reflection profiling with a powerful airgun source augmented with a few wide angle seismometer stations on land has been applied along a 180 km line across the presently active deformation front of the subduction of the ionian sea plate beneath the western hellenides east of the ionian islands there is limited evidence for reflectivity down to 23 km interpreted as the base of a rather thin continental type crust under the western slope of the islands a major normal incidence reflector dips eastward first gently to the west of the islands then more steeply under them this reflector may be extrapolated southwestwards beneath a bulge that is thought to represent the modern pre apulian front located over the subduction zone the continuity signature and geometry of this reflector suggest that it may act as the lower limit of the western hellenides where they override the ionian sea quasi oceanic crust rather than just an intracrustal interface of a pre apulian crust the location of the previous deformation front the ionian thrust proposed in previous models can be constrained by the new seismic data the new data raise the possibility of a larger area of evaporite mobility than previously considered insofar as active block motion apparently related to halokinesis is recognized west of the zakynthos anticline diapirism decollement and westward directed over thrusting in the pre apulian crust may have been brought on by late pliocene quaternary reactivation of regional extension associated with the separation of the peloponnesus from northern greece as it was captured by the anatolian aegean rotation and associated also with the fast clockwise rotation of the ionian islands as they were sheared off the apulian domain to the southwest by the initiation of the kefallinia transform

earthquake swarms slow slip and fault interactions at the western end of the hellenic subduction system precede the mw 6 9 zakynthos earthquake greece the month to year long deformation of the earth s crust where active subduction zones terminate is poorly explored here we report on a multidisciplinary dataset that captures the synergy of slow s

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

a new experimental approach to study fluid rock equilibria at the slab mantle interface based on the synthetic fluid inclusion technique the role of high pressure aqueous fluids in mass transfer processes during slab dehydration has been recognized for a long time however the quantitative assessment of their material transport capacity in complex natural systems remains poorly understood mainly as a consequence of their unquenchable nature and current experimental limitations a new experimental approach has been developed to investigate complex fluid rock equilibria at high pressure and temperature conditions relevant for slab dehydration processes aqueous fluids pre equilibrated with high pressure mineral assemblages were sampled at run conditions in the form of synthetic fluid inclusions sfi in quartz and subsequently analyzed by laser ablation icpms la icp ms the main innovation introduced in the experiments is that the quartz crystal was fractured in situ during the run only after chemical equilibrium between phases has been achieved thus allowing the entrapment of fluid inclusions that sample true equilibrium compositions an efficient fracturing of quartz at high pressure and temperature conditions was achieved by crossing the quartz coesite reaction boundary which occurs at pressures of the sub arc slab mantle interface an experimental methodology has been developed to implement this strategy and experiments in the eclogite water system were conducted to demonstrate the feasibility and advantage of the method the results demonstrate that secondary fluid inclusions formed early in pre fractured quartz are systematically diluted compared to secondary inclusions formed after in situ fracturing of quartz particularly for elements such as sr zr nb ti and mg these observations demonstrate that early entrapment of fluids in pre fractured quartz do not represent equilibrium fluids at high pressure temperature conditions

closure of the africa eurasia north america plate motion circuit and tectonics of the gloria fault we examine the closure of the current plate motion circuit between the african north american and eurasian plates to test whether these plates are rigid and whether the gloria fault is an active transform fault we also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries and compare the predicted direction of motion along the african eurasian plate boundary in the mediterranean with the direction of slip observed in earthquakes from marine geophysical data we obtain 13 transform fault azimuths and 40 3 m y average spreading rates 34 of which are determined from comparison of synthetic magnetic anomaly profiles to 140 observed profiles slip vectors from 32 earthquake focal mechanisms further describe plate motion detailed magnetic surveys north of iceland provide 11 rates in a region where prior plate motion models had few data magnetic profiles north of the azores triple junction record a rate of 24 mm yr 4 mm yr slower than used by prior models gloria and sea beam surveys accurately measure the azimuths of seven transform faults our plate motion model fits six of the seven within 2 two transform faults surveyed by gloria side scan sonar lie near famous area transform faults a and b and give azimuths 13 clockwise of them because recent studies show that short offset transforms such as transforms a and b are in many places oblique to the direction of plate motion we exclude azimuths from transforms with less than 35 km offset the best fitting and closure enforced vectors fit the data well except for a small systematic misfit to the slip vectors on right lateral slipping transforms slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths whereas on left lateral slipping transforms slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths we search the long eurasia north america boundary for evidence of an additional plate but find no systematic misfits to the data in particular if a spitsbergen plate exists and moves relative to eurasia its motion is less than 3 mm yr an africa eurasia euler vector determined by adding the eurasia north america and africa north america euler vectors is consistent with the gloria fault trend and with slip vectors from eastern azores gibraltar ridge focal mechanisms a small circle centered at the africa eurasia closure enforced pole fits the trace of the gloria fault the model in which closure was enforced predicts 4 mm yr slip across the azores gibraltar ridge and west northwest convergence near gibraltar 45 more oblique than suggested by a recent model based on compressive axes of focal mechanisms moreover our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between gibraltar and sicily because closure enforced vectors fit the data nearly as well as the best fitting vectors we conclude that the data are consistent with a rigid plate model and with the gloria fault being a transform fault

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

slab segmentation and late cenozoic disruption of the hellenic arc the hellenic subduction zone displays well defined temporal and spatial variations in subduction rate and offers an excellent natural laboratory for studying the interaction among slab buoyancy subduction rate and tectonic deformation in space the active hellenic subduction front is dextrally offset by 100 120 km across the kephalonia transform zone coinciding with the junction of a slowly subducting adriatic continental lithosphere in the north 5 10 mm yr and a rapidly subducting ionian oceanic lithosphere in the south 35 mm yr subduction rates can be shown to have decreased from late eocene time onward reaching 5 12 mm yr by late miocene time before increasing again along the southern portion of the subduction system geodynamic modeling demonstrates that the differing rates of subduction and the resultant trench offset arise naturally from subduction of oceanic pindos lithosphere until late eocene time followed by subduction of a broad tract of continental or transitional lithosphere hellenic external carbonate platform and then by miocene entry of high density oceanic ionian lithosphere into the southern hellenic trench model results yield an initiation age for the kephalonia transform of 6 8 ma in good agreement with observations consistency between geodynamic model results and geologic observations suggest that the middle miocene and younger deformation of the hellenic upper plate including formation of the central hellenic shear zone can be quantitatively understood as the result of spatial variations in the buoyancy of the subducting slab using this assumption we make late eocene middle miocene and pliocene reconstructions of the hellenic system that include quantitative constraints from subduction modeling and geologic constraints on the timing and mode of upper plate deformation

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

crustal velocity and moho structure beneath the gulf of corinth greece summary the gulf of corinth goc greece is a continental rift with high rates of seismicity and extensional strain how this strain is accommodated in the crust and whether there are variations in the mechanism along strike remain open questions in part because of a lack of wide angle reflection refraction studies that constrain crustal velocity structure in 2001 an extensive multichannel seismic survey was conducted within the goc one component of which included the wide angle recording of sources from within the gulf at stations on land surrounding the gulf in this paper we use wide angle data in two separate but allied studies to constrain crustal velocities and depth to the moho a 2 d inversion of refraction and reflection traveltimes along an axial profile through the goc constrains the shallow crustal velocity structure images the moho at 29 km depth in the east dipping to 39 km in the west and images the eastward subducting african slab beneath the western goc at a depth of 74 km the 1 d average of the 2 d velocity model was used in a tomographic inversion of pmp reflection times to solve for depth to the moho throughout the corinth region this model shows generally thick isostatically compensated crust 37 km beneath the hellenide mountains except immediately south of the goc and a singular region of thin crust 30 km beneath the perahora peninsula at the eastern end of the gulf a comparison with moho depths derived from gravity inversion shows a general agreement with crust thickening from east to west but a number of differences in detail the 3 d crustal thickness variations are more complex than those predicted by either pure shear or simple shear models of continental extension and suggest significant pre rift structural variability

seismically inferred dilatancy distribution northern barbados ridge decollement implications for fluid migration and fault strength a 5 x 25 km three dimensional seismic survey of the lower part of the northern barbados ridge accretionary prism creates a three dimensional image of a major active decollement fault the fault is usually a compound negative polarity reflection modeled as a low velocity high porosity zone less than 14 m thick this thickness is significantly less than that defined by drilling of a 40 m zone of deformation at ocean drilling program odp site 671b located within the surveyed area we infer that the seismically defined fault is a thin high porosity zone and is thus an undercompacted high fluid pressure dilatant section if these inferences are correct then map view variations in seismic reflection waveform and amplitude illustrate complex patterns of fault zone fluid content and fluid migration paths the amplitude map suggests kilometre wide channels of locally high porosity and thus focused fluid flow these paths are only subparallel to the expected minimum head as inferred from the shape of the overlying sediment wedge other factors must modify fluid concentrations and ultimately migration several areas of positive polarity fault reflections define square kilometre sized regions inferred to be lower porosity sections producing strong asperities in an otherwise weak fault one coincident with site 671b may explain the success of drilling through the fault here all other holes drilled in the area were within the negative polarity regions and were unsuccessful in penetrating through the entire fault zone possibly because of instability associated with high fluid pressures and a weak fault odp leg 156 planned for 1994 will test inferences related to fault permeability and fluid pressures

a speculative reconstruction of the middle paleozoic continental margin of southwestern north america geologic relations and data from strontium and oxygen isotopic studies are used together to speculate on the paleogeographic positions of various crustal blocks or terranes in southwestern north america with respect to the middle paleozoic continental margin the southwestern margin of the middle paleozoic continent based on these data is quite irregular in its present configuration but most of the irregularities can be accounted for by strike slip displacement of continental fragments during several post middle paleozoic tectonic events we conclude that large scale late paleozoic sinistral displacements and mesozoic and cenozoic dextral displacements have been the major events affecting the configuration of this margin our preferred model includes the following elements 1 500 km of left lateral displacement of a large part of the margin during a late paleozoic truncation 2 slivering of the margin by right lateral faulting during the mesozoic amounting to about 275 km of total displacement and 3 further deformation of the margin during the cenozoic primarily by right lateral faulting oroclinal bending and crustal extension

seismic sequence near zakynthos island greece april 2006 identification of the activated fault plane abstract the april 2006 earthquake sequence near zakynthos western greece is analysed to identify the fault plane s the sequence 33 events was relocated to assess physical insight into the hypocenter uncertainty moment tensor solution of three major events was performed simultaneously with the determination of the centroid position joint analysis of the hypocenter position centroid position and nodal planes indicated sub horizontal fault planes moment tensor solutions of 15 smaller events were performed under assumption that the source positions are those of the hypocenters without seeking centroids their focal mechanisms are highly similar and agree with the analysis of the three major events the preferable seismotectonic interpretation is that the whole sequence activated a single sub horizontal fault zone at a depth of about 13 km corresponding to the interplate subduction boundary considering that the ionian sea is a high seismicity area the identification of the seismic fault is significant for the seismic hazard investigation of the region

trace element partitioning between apatite and silicate melts we present new experimental apatite melt trace element partition coefficients for a large number of trace elements cs rb ba la ce pr sm gd lu y sr zr hf nb ta u pb and th the experiments were conducted at pressures of 1 0 gpa and temperatures of 1250 c the rare earth elements la ce pr sm gd and lu y and sr are compatible in apatite whereas the larger lithophile elements cs rb and ba are strongly incompatible other trace elements such as u th and pb have partition coefficients close to unity

alkali metals control the release of gold from volatile rich magmas magmatic hydrothermal ore deposits are a major resource of gold volatiles exsolving from magmas rising through the earth s crust are the key agent for enrichment of gold in these deposits we report the first experimental determination of gold solubilities in the magmatic volatile phases at conditions typical of most magmas associated with gold deposits t 1000 degrees c p 150 mpa we show that gold hydrosulfide complexes supersede gold chloride complexes and more importantly that the stability of gold hydrosulfide complexes is greatly increased by the presence of minute concentrations of kc or nacl 0 1 0 5 mol kg h2o the amplifying effect of alkali chlorides on the solubility of gold in h2s bearing volatiles may explain the preferential association of many giant hydrothermal gold deposits with high potassium alkaline mafic to intermediate igneous rocks which exsolve volatiles that simultaneously contain both h2s and alkali chlorides in significant concentrations c 2010 elsevier b v all rights reserved

west margin of north america a synthesis of recent seismic transects abstract a comparison of the deep structure along nine recent transects of the west margin of north america shows many important similarities and differences common tectonic elements identified in the deep structure along these transects include actively subducting oceanic crust accreted oceanic arc or oceanic like lithosphere of mesozoic through cenozoic ages cenozoic accretionary prisms mesozoic accretionary prisms backstops to the mesozoic prisms and undivided lower crust not all of these elements are present along all transects in this study nine transects including four crossing subduction zones and five crossing transform faults are plotted at the same scale and vertical exaggeration v e 1 1 using the above scheme for identifying tectonic elements the four subduction zone transects contain actively subducting oceanic crust cenozoic accretionary prisms and bodies of basaltic rocks accreted in the cenozoic including remnants of a large oceanic plateau in the oregon and vancouver island transects rocks of age and composition eocene basalt similar to the oceanic plateau are currently subducting in southern alaska where they are doubled up on top of pacific oceanic crust and have apparently created a giant asperity or impediment to subduction most of the subduction zone transects also contain mesozoic accretionary prisms and two of them vancouver island and alaska also contain thick tectonically underplated bodies of late mesozoic early cenozoic oceanic lithosphere interpreted as fragments of the extinct kula plate in the upper crust most of the five transform fault transects all in california reflect 1 tectonic wedging of a mesozoic accretionary prism into a backstop which includes mesozoic early cenozoic forearc rocks and mesozoic ophiolitic arc basement rocks and 2 shuffling of the subduction margin of california by strike slip faulting in the lower crust they may reflect migration of the mendocino triple junction northward seen in rocks east of the san andreas fault and cessation of farallon plate subduction seen in rocks west of the san andreas fault in northern california lower crustal rocks east of the san andreas fault have oceanic crustal velocity and thickness and contain patches of high reflectivity they may represent basaltic rocks magmatically underplated in the wake of the migration of the mendocino triple junction or they may represent stalled subducted fragments of the farallon gorda plate the latter alternative does not fit the accepted slabless window model for the migration of the triple junction this lower crustal layer and the moho are offset at the san andreas and maacama faults in central california a similar lower crustal layer is observed west of the san andreas fault west of the continental slope it is pacific oceanic crust but beneath the continent it may represent either pacific oceanic crust stalled subducted fragments microplates of the farallon plate or basaltic rocks magmatically underplated during subduction of the pacific farallon ridge or during breakup of the subducted farallon plate the transect in southern california is only partly representative of regional structure as the structure here is 3 dimensional in the upper crust a mesozoic prism has been thrust beneath crystalline basement rocks of the san gabriel mountains and mojave desert in the mid crust a bright reflective zone is interpreted as a possible master decollement that can be traced from the fold and thrust belt of the los angeles basin northward to at least the san andreas fault a moho depression beneath the san gabriel mountains is consistent with downwelling of lithospheric mantle beneath the transverse ranges that appears to be driving the compression across the transverse ranges and los angeles basin

present day motion along the owen fracture zone and dalrymple trough in the arabian sea all plate motion data available for describing the present day motion between the arabian and indian plates are analyzed to understand the present day tectonic role of the presumed plate boundary the owen fracture zone and dalrymple trough in the northern arabian sea all prior plate motion models are shown to be inconsistent with some of the data along the presumed boundary in particular published global plate motion models predict some convergence across the owen fracture zone and dalrymple trough convergence along the owen fracture zone is contradicted by earthquake focal mechanisms which show right lateral strike slip convergence along the dalrymple trough is contradicted by observed normal faulting in the trough and by normal and strike slip focal mechanisms for earthquakes occurring along or near the trough the sense and rate of motion is further constrained by spreading rates along the sheba ridge northwest of the owen fracture zone and along the carlsberg ridge southeast of the owen fracture zone to estimate the present day motion we determine 43 3 m y average spreading rates from sheba ridge carlsberg ridge and central indian ridge magnetic profiles and have combined them with eight transform azimuths and 15 earthquake slip vectors along these ridges and the arabia india boundary we determine an arabia india euler vector that predicts 2 mm yr of right lateral strike slip motion along the owen fracture zone with a 95 confidence interval of 0 7 mm yr which excludes the faster rates of slips predicted by several prior models the direction of motion is 35 50 counterclockwise from that predicted by published global plate motion models if we omit the data along the arabia india boundary the motion differs insignificantly from zero suggesting that magnetic profiles from the carlsberg and sheba ridges give spreading rates too imprecise to detect the slow arabia india motion if the owen fracture zone and dalrymple trough are regarded as a plate boundary it is the slowest slipping plate boundary known on earth with motion about 100 times slower than the fastest slipping faults along the east pacific rise

bromine cycle in subduction zones through in situ br monitoring in diamond anvil cells abstract the geochemical partitioning of bromine between hydrous haplogranitic melts initially enriched with respect to br and aqueous fluids has been continuously monitored in situ during decompression experiments were carried out in diamond anvil cells from 890 c to room temperature and from 1 7 gpa to room pressure typically from high p t conditions corresponding to total miscibility presence of a supercritical fluid br contents were measured in aqueous fluids hydrous melts and supercritical fluids partition coefficients of bromine were characterized at pressure and temperature between fluids hydrous melts and or glasses as appropriate d br fluid melt br fluid br melt ranges from 2 18 to 9 2 0 5 for conditions within the ranges 0 66 1 7 gpa 590 890 c and d br fluid glass br fluid br glass ranges from 60 to 375 at room conditions the results suggest that because high pressure melts and fluids are capable of accepting high concentrations of bromine this element may be efficiently removed from the slab to the mantle source of arc magmas we show that br may be highly concentrated in subduction zone magmas and strongly enriched in subduction related volcanic gases because its mobility is strongly correlated with that of water during magma degassing furthermore our experimental results suggest that a non negligible part of br present in the subducted slab may remain in the down going slab being transported toward the transition zone this indicates that the br cycle in subduction zones is in fact divided in two related but independent parts 1 a shallower one where recycled br may leave the slab with a water and silica bearing fluid leading to enriched arc magmas that return br to the atmosphere 2 a deeper cycle where br may be recycled back to the mantle maybe to the transition zone where it may be present in high pressure water rich metasomatic fluids

seismic modeling of the decollement zone at the base of the barbados ridge accretionary complex wide aperture seismic reflection profiling of the northern barbados ridge accretionary complex at 16 12 n has imaged the decollement horizon across more than 100 km of the accretionary complex revealing prominent changes in the amplitude of the decollement reflection synthetic seismograms from models of the variation of velocity and density with depth were compared with selected seismic traces between 2 5 km seaward of the toe of the accretionary complex and 20 km landward of the toe to determine the changes in velocity density properties along the decollement thrust zone modeling requires a thin low velocity layer to develop landward along the decollement beneath the complex while no such layer exists at the corresponding stratigraphic boundary in the undeformed sediments seaward of the complex two dimensional modeling that incorporated lateral variations in topography velocity and density was performed on a 7 km section of the decollement 20 km landward of the deformation front the best fitting model includes a 20 m thick low velocity layer at the decollement horizon with a relative velocity decrease in the layer of 0 2 km s changes in the reflection amplitude along this 7 km section could be produced by either a change in the velocity anomaly within the layer or a thinning of the decollement layer to less than 4 m the shape of the reflected wavelet from the decollement indicates that the principal cause of the amplitude variation is a change in the velocity contrast rather than a change in thickness the low velocity layer can be explained by a decollement shear zone that has high porosity maintained by elevated pore fluid pressure high fracture permeability within the decollement permits dewatering of sediment attached to the oceanic crust and thrust beneath the accretionary complex

the november 17th 2015 lefkada greece strike slip earthquake field mapping of generated failures and assessment of macroseismic intensity esi 07 abstract on november 17 2015 a strong shallow earthquake mw 6 5 occurred on the island of lefkada along a n20 5 e east dipping strike slip fault with right lateral sense of slip the event triggered environmental effects that were mainly mapped at the western part of the island while moving towards the eastern part the severity of the earthquake induced failures decreased the most characteristic geological effects that were triggered by the earthquake were slope failures including rock falls rock slides and landslides the spatial density of the failures follows an exponential increase with slope angle and decreases for values larger than 55 small size liquefaction phenomena such as sand craters and ejection of fine grained sand through ground cracks were documented at the coastal area of vassiliki the epicentral intensity was assessed based on the definitions of environment seismic intensity scale as viii esi 07 and the macroseismic epicenter viii up to ix was located at the coastal area of egremnoi west of athani village south lefkada in addition comparing the severity of earthquake induced failures on the main road network triggered by the 2003 and 2015 events it is concluded that the behavior of the protection measures such as fences and walls could be generally characterized as satisfactory on the contrary the similarity of the structural failures triggered by the 2003 event with the ones triggered by the 2015 earthquake documented at the port of vassiliki indicates that the post 2003 constructed port facilities failed to guarantee the functionality of the port of vassiliki

present day crustal stress field in greece inferred from regional scale damped inversion of earthquake focal mechanisms in this study we utilize regional and teleseismic earthquake moment tensor solutions in order to infer the contemporary crustal stress in the greek region we focus on crustal earthquakes and select only solutions with good waveform fits and well resolved nodal planes a data set of 1614 focal mechanisms is used as input to a regional scale damped stress inversion algorithm over a grid whose node spacing is 0 35 several resolution and sensitivity tests are performed in order to ascertain the robustness of our results our findings show that for most of the greek region the largest principal stress 1 is vertically oriented and that the minimum principal stress axis 3 are subhorizontal with a predominant n s orientation in the sw peloponnese the orientation of 3 axes rotates clockwise and in se aegean counterclockwise these results are in agreement with the generally accepted model that slab rollback combined with gravitational spreading of the aegean lithosphere are the main causes of the extension transitions between different faulting types in nw greece or in the aegean occur within narrow zones in the order of tens of kilometers a visual comparison of the principal horizontal stress axes and the principal strain axes derived from gps observations shows good agreement suggesting that the crust in the greek region behaves largely in an elastic manner

moment tensor inversion of the 1983 january 17 kefallinia event of ionian islands greece summary the source parameters of the recent 1983 january 17 ionian island event are obtained by the inversion of body waves an optimum source depth of 8 km is determined and the source parameters of the major double couple are strike 60 dip 47 rake 174 and seismic moment m0 7 3 1025 dyne cm this mechanism implies a strike slip dextral fault with a small thrust component this solution ascertains the existence of a transform fault connecting the northwestern edge of the hellenic are with the compressional zone which is produced by the collision of the apulian plate with the eurasian plate along the adriatic north ionian coast this right lateral strike slip fault probably terminates the hellenic subduction zone

earthquake locations in the western hellenic arc relative to the plate boundary four vertical component seismograph stations were operated in western crete southeastern peloponnesus the island of milos and south of corinth on mount didimon from 1981 to 1984 combining arrival times from this network the greek national network and volnet we relocated hypocenters within greece and the surrounding area the difference between the relocations and the locations published in the national observatory of athens bulletin in most instances were minor except for earthquakes located in the vicinity of the western hellenic arc in this area we found that epicenters thought to lie south of the plate boundary within the african plate relocated an average of approximately 60 km to the n30 e which places them at or north of the plate boundary we suggest that this difference is a minimum estimate of the location error and the true locations may lie still further to the nne we propose that anomalously slow seismic velocities in the aegean back arc upper mantle cause travel time delays to the seismograph stations located to the ne of the source volumes resulting in location errors in a direction away from these stations extrapolating from our observations to other segments of the hellenic plate boundary and to periods not covered by our operation we hypothesize that most or all earthquakes thought to have originated on the african plate within about 100 km of the hellenic arc were actually located at the plate boundary or on the aegean plate