global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

evidence for transform faulting in the ionian sea the cephalonia island earthquake sequence of 1983 accurate locations of aftershocks of the january 17 1983 ms 7 0 main shock in the ionian islands have been determined as well as fault plane solutions for this main shock and its largest aftershock which are interpreted as a right lateral strike slip motion with a thrust component on a fault striking in about a ne sw direction

shear velocity structure in the aegean area obtained by inversion of rayleigh waves summary the purpose of this work is to derive a 3 d tomographic image of the shear wave velocity structure of the crust uppermost mantle in the aegean area using the group velocities of rayleigh wave fundamental mode the database consists of 185 regional earthquakes recorded at broad band stations that were installed for a period of 6 month in the aegean area within the framework of a large scale experiment in a previous work karagianni et al 2002 an averaged group velocity has been determined using the method of frequency time analysis ftan for each epicentre station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths taking into account additional resolution results obtained for the local group velocities a grid of 0 5 was adopted for the aegean area and a local dispersion curve was defined for each gridpoint more than 80 local dispersion curves were finally inverted using a non linear inversion approach deriving the corresponding 1 d shear velocity models the interpolation of these models resulted in a 3 d s wave tomographic image of the crust and uppermost mantle in the broader aegean area as expected as a result of the complex tectonic setting of the aegean area strong lateral variations of the s wave velocities of the crust and uppermost mantle of the studied area are found in the southern aegean sea as well as in a large part of the central aegean sea a thin crust of approximately 20 22 km is observed whereas the remaining aegean sea area exhibits a crustal thickness less than 28 30 km on the contrary a crustal thickness of 40 46 km is observed in western greece along the hellenides mountain range whereas in the eastern continental greece the crust has a typical thickness of approximately 30 34 km for shallow depths 10 km low s wave velocities are observed under the sedimentary basins of the north aegean sea the gulf of thermaikos axios basin and western greece at depths ranging from 10 to 20 km low s wave velocities are mainly found in western greece under peloponnesus as well as in rhodes this low velocity zone seems to extend along the hellenic arc and can be correlated to the hellenides mountain range and the alpine orogenesis in agreement with previous p wave tomographic results in the southern aegean sea very low s wave velocities 3 6 4 0 km s 1 are observed at depths of approximately 30 40 km just below the moho discontinuity while in the rest of the inner aegean sea and continental greece the uppermost mantle is characterized by velocities around 4 3 4 4 km s 1 this low velocity zone in the southern aegean sea can be associated with the high temperatures and the presence of significant percentage partial melt in the mantle wedge of the southern aegean subduction zone in agreement with previous studies

active crustal deformation from the azores triple junction to the middle east the co seismic crustal deformation along the africa eurasia eurasia arabia plate boundary from the azores triple junction 30 w up to the karliova triple junction 41 e is examined based on the moment tensor summation of mainly post 1964 earthquakes with ms 5 0 strain rates range from 10 8 yr to 10 6 yr while values exceeding 10 7 yr were calculated for the back arc aegean area and for the north anatolian fault zone a remarkable stability in the azimuth of the component of compression and of extension is observed in the area that extends west of italy 17 e up to the azores triple junction along this region the deformation is taken up by compression along a mean direction of n140 with rates from 1 1 to 2 8 mm yr and by extension along a mean direction of n50 with rates from 2 4 to 12 0 mm yr at the gloria fault and in the surrounding area dextral strike slip motion occurs at a rate of 11 mm yr from sicily up to the eastern end of the hellenic arc the crust is compressed at azimuths in the range n20 n31 with an average value of 26 5 this compression is occurring at a rate of 1 21 mm yr with an average value of 9 8 mm yr in the back arc aegean area extension is occurring along a mean azimuth of n156 with a rate of 5 2 3 8 mm yr the average shortening rate along the convex side of the hellenic arc is 12 mm yr from the eastern end of the north anatolian fault 41 e up to the northern aegean trough extension along n68 n179 and compression along n158 n89 occurs which results in dextral strike slip motion the rate of extension reduces from east to west from 30 mm yr to 5 mm yr while the rate of compression reduces from 17 mm yr to 5 mm yr the northwards motion of arabia results in a n31 trending compression at a rate of 7 mm yr along the east anatolian fault zone

evolution of the stress field in the northern aegean sea greece summary the evolution of the stress field in the area of the northern aegean sea during the 20th century has been studied the area is dominated by dextral strike slip faulting and is characterized by frequent strong earthquakes coulomb stress changes dcff were calculated assuming that earthquakes can be modelled as static dislocations in an elastic half space and taking into account both the coseismic slip in large mi7 0 earthquakes and the slow tectonic stress build up along the major fault segments the stress change calculations were performed for strike slip faults of strike dip and rake appropriate to the large events we evaluate whether these stress changes brought a given large earthquake closer to or farther from failure it was found that each of the large events occurred in regions of increased calculated coulomb stress moreover the majority of smaller events for which reliable fault plane solutions are available were also located in areas of positive dcff by extending the calculations to 2020 and assuming that no additional large mi7 0 earthquake occurs between 1999 and 2020 possible sites of future large earthquakes are identified

earthquake triggering in the north and east aegean plate boundaries due to the anatolia westward motion historical and instrumental data of the last five centuries show that major earthquakes in the marmara sea area are followed by high strong earthquake seismicity in the aegean area during the first phase of this excitation period which lasts about 3 years strong shallow earthquakes concentrate almost exclusively along the northern boundary of the aegean plate within 1 5 years after the first strong earthquake along this boundary strong earthquake seismicity also increases in the eastern aegean boundary on the basis of current ideas on active tectonics and the previous observations we expect the generation of several mainshocks with a mean magnitude of m 6 5 along the northern aegean boundary during the next 3 years following the recent large izmit nw turkey earthquake 1999 8 17 m 7 4

introduction to the special issue on the 2003 eruption of anatahan volcano commonwealth of the northern mariana islands cnmi 1 introductionanatahan volcano situated in the commonwealthof the northern mariana islands cnmi erupted forthefirst timeinrecordedhistoryonmay10 2003 theeruption prompted a period of intensive study andcollaboration between researchers from a number ofgovernmental agencies institutes and universities andresultedinaspecialsessiondedicatedtotheeruptionatthe fall meeting of the american geophysical union agu in december of thesame year seeeos trans agu 84 46 p 1561 1563 this volume of thirteenpapersgrewoutoftheaguspecialsessionandcoversfour principal themes a geological studies of anata han carried out prior to the may 2003 event includingmapping of both the submarine and subaerial portionsof the volcano and monitoring of the local seismicityfollowing activity in 1990 b geophysical signals ofthe 2003 eruption c petrology and geochemistry ofthe eruptive products of the 2003 eruption and d impacts associated with the 2003 eruption in this briefintroduction we summarize the major findings asso ciatedwitheachofthesethemes wealsooffersugges tionstowhereupdatedmaterialandresultsofon goingstudies can be found at the time of writing january2005 anatahan volcano continues to be active albeit at a lower level compared to the spring of2003 so remains the focus of considerable researchand monitoring efforts 2 anatahan volcano background geologythe island of anatahan is situated about 120 kmnorth of saipan the capital of the cnmi it lies atthe southern end of the 1500 km long izu bonin mariana ibm arc system where the oldest oceaniccrust of the pacific plate is subducting beneath youn ger crust of the philippine plate the island representsthe summit of a large strato volcano which rises fromdepths of 3000 m below sea level to an elevation of788 m

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

estimating the basin scale ocean circulation from satellite altimetry part i straightforward spherical harmonic expansion abstract direct estimation of the absolute dynamic topography from satellite altimetry has been confined to the largest scales basically the basin scale owing to the fact that the signal to noise ratio i more unfavorable everywhere else but even for the largest scales the results are contaminated by the orbit error and geoid uncertainties recently a more accurate earth gravity model gem t1 became available thus giving us the opportunity to examine the whole question of direct estimation under a more critical limelight it is found that our knowledge of the earth s gravity field has indeed improved a great deal however it is not yet possible to claim definitively that our knowledge of the ocean circulation has improved through direct estimation yet the improvement in the gravity model has come to the point that it is no longer possible to attribute the discrepancy at basin scales between altimetric and hydrographic results as mostly due to geoid uncertainties a substantial part of the differen

the 2001 skyros northern aegean greece earthquake sequence off fault aftershocks tectonic implications and seismicity triggering was identified as a possible site for the occurrence of a strong event by papadimitriou and sykes 2001 who applied an evolutionary stress model in the northern aegean area 4 the paper analyzes the details of the earthquakes in the skyros sequence aiming to contribute to the understanding of the seismotectonic properties in this area where the western termination of the north aegean strike slip faulting against the mainland of greece takes place the co seismic stress changes associated with the main shock are computed and the areas of static stress increases are correlated with the aftershock spatial distribution

rupture zones in the aegean region rupture zones of strong shallow earthquakes can be investigated by field observations of surface fault traces sf accurate location of spatial clusters of aftershocks or other small earthquakes cl reliable fault plane solutions fp and information on the spatial distribution of sites with high i viii macroseismic intensities ma the validity of these four techniques was successfully tested by comparing the results of their application to several cases of strong shallow earthquakes these techniques were then applied to spatially define the rupture zones of 150 strong m 6 0 shallow earthquakes in the aegean and surrounding area the type of faulting was determined for all these zones by the use of reliable fault plane solutions which are available for this area the orientation of most of these rupture fault zones is in good agreement with the presently acting stress field with some exceptions which are attributed to the rupture of pre existing faults the tectonic implications of these zones are discussed 1999 elsevier science b v all rights reserved

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

seismological and gps evidence for the aegean anatolia interaction seismological and gps data are used in order to examine the seismotectonic setting and the plate motions in the eastern mediterranean the main objective is to reevaluate the recently proposed idea of a single anatolia aegean microplate which performs a rigid body rotation about an euler pole located in northern africa both data sets show a more complicated setting south of the north anatolia fault naf the plate motion of anatolia relative to europe can be adequately described by a simple rigid body rotation with a dominant east west component and an average velocity of 22mm yr however both types of data show a significant increase of the deformation velocities in the aegean area 30 35mm yr and exhibit a much larger n s component up to 20mm yr than the one predicted from rigid body rotation this deformation pattern is more consistent with models which consider the aegean as a separate microplate

the medina wrench a key to the kinematics of the central and eastern mediterranean over the past 5 ma the medina wrenth in the central mediterranean is a transform fault connecting the plate collision in northwest africa and northern sicily with that occurring at the aegean plate boundary south of greece the more than 800 km long crescent shaped wrench zone is currently seismically quiet but exhibits major deformation since 5 ma within a belt 30 100 km wide it forms the southern boundary of two microplates moving eastward with respect to africa and europe a simple plate rotation model constrained by recent paleomagnetic data indicates that a continental iblean microplate and a hybrid continental oceanic ionian microplate separated along the malta escarpment have rotated anticlockwise by 11 and 12 respectively around poles in southern italy these rotations involved some 100 km of dextral eastward movement relative to africa of the ionian basin north of the medina wrench since 5 ma combining the published 26 clockwise rotation of the peloponnesus and northwest half of the aegean with the 12 anticlockwise rotation of the ionian microplate results in a a 99 agreement between the length of the seismic benioff zone beneath greece and the total convergence of the microplates and b an average rate of convergence across the aegean plate boundary southwest of the peloponnesus of 6 6 1cm a 1 since the miocene relative motion between microplates in a collision zone thus may be as much as 6 times faster than convergence between the major plates which spawned them and they can be considered rigid to the first order over the time span involved

the strain field in northwestern greece and the ionian islands results inferred from gps measurements abstract recent crustal movements detected by the analysis of repeated satellite geodetic measurements reflect the ongoing geodynamic processes in the alpine mediterranean area superimposed on the large scale counterclockwise rotation of the african plate complex dynamic processes are affecting the lithospheric fragments between the african and eurasian plates key features to better understand the driving forces and associated seismic activity in the africa eurasia collision zone are the calabrian and hellenic arcs in this paper geodynamic investigations along the west hellenic arc are discussed they are based on two epochs 1989 and 1993 of satellite geodetic measurements carried out using the us global positioning system gps the results are presented in terms of relative displacements and strain rates within the time span of 4 years southwestern greece has moved to the southwest relative to southeastern italy by an average of 120 mm increasing from 80 mm at lefkada in the center of the ionian islands to 160 mm at the peloponnesus the maximum strain rate is 0 18 strain a located in the vicinity of lefkada where anomalously high earthquake activity is observed the data provide strong evidence for dextral strike slip motion on the order of 25 mm a along the kephalonia fault zone kfz the deformation field of the kfz is interpreted as a transition zone between the kinematics of the apulian platform and the west hellenic fold and thrust belts

present day dynamics of the aegean region a model analysis of the horizontal pattern of stress and deformation in order to gain quantitative insight into the forces that control the present day stress field and pattern of horizontal motions in the aegean region we adopt a forward model approach mechanisms that have been proposed to explain the present day tectonics are represented to first approximation in terms of the expected force distributions on the basis of a thin elastic shell representation of the aegean lithosphere we then calculate the stress field and displacements associated with these force sets and compare the results with observations of the state of stress based on geological studies of fault kinematics strain as expressed by earthquake focal mechanisms and horizontal motions measured by means of satellite geodesy the two most commonly cited mechanisms suggested to control the aegean tectonics 1 the push exerted by the westward moving anatolian block and 2 forces associated with the hellenic subduction zone are first analyzed separately it is found that the westward anatolian push alone does not explain the observed prevalence of tensional stress this is also expressed in a mismatch between the displacements computed to result from the westward push and the observed horizontal velocities regarding the forces on the aegean overriding margin we find that a model with outward pulling forces of uniform magnitude acting normal to the arc from the sw peloponnese to rhodes yields a stress field that matches the observed pattern of tension to a large extent this distribution of forces is consistent with the notion of gravitational spreading of the aegean lithosphere the pattern of seismic strain of the overriding margin may evidence the occurrence of a small additional resistive force although the prevalence of tension thus appears due mainly to the subduction related forces other aspects of the stress field and also the pattern of horizontal motions indicate that these forces act in combination with westward push our model results allow us to address the relation between the forces experienced by the upper plate and the kinematics of subduction not just in terms of a vertical cross section but also by taking into account the along arc dimension

an alternative approach to probabilistic seismic hazard analysis in the aegean region using monte carlo simulation abstract the aegean is the most seismically active and tectonically complex region in europe damaging earthquakes have occurred here throughout recorded history often resulting in considerable loss of life the monte carlo method of probabilistic seismic hazard analysis psha is used to determine the level of ground motion likely to be exceeded in a given time period multiple random simulations of seismicity are generated to calculate directly the ground motion for a given site within the seismic hazard analysis we explore the impact of different seismic source models incorporating both uniform zones and distributed seismicity a new simplified seismic source model derived from seismotectonic interpretation is presented for the aegean region this is combined into the epistemic uncertainty analysis alongside existing source models for the region and models derived by a k means cluster analysis approach seismic source models derived using the k means approach offer a degree of objectivity and reproducibility into the otherwise subjective approach of delineating seismic sources using expert judgment similar review and analysis is undertaken for the selection of peak ground acceleration pga attenuation models incorporating into the epistemic analysis greek specific models european models and a next generation attenuation model hazard maps for pga on a rock site with a 10 probability of being exceeded in 50 years are produced and different source and attenuation models are compared these indicate that greek specific attenuation models with their smaller aleatory variability terms produce lower pga hazard whilst recent european models and next generation attenuation nga model produce similar results the monte carlo method is extended further to assimilate epistemic uncertainty into the hazard calculation thus integrating across several appropriate source and pga attenuation models site condition and fault type are also integrated into the hazard mapping calculations these hazard maps are in general agreement with previous maps for the aegean recognising the highest hazard in the ionian islands gulf of corinth and hellenic arc peak ground accelerations for some sites in these regions reach as high as 500 600 cm s 2 using european nga attenuation models and 400 500 cm s 2 using greek attenuation models

active tectonics of the aegean region the aegean sea and its surrounding regions comprise one of the most rapidly deforming parts of the alpine himalayan mountain belt though the deformation of the belt as a whole is related to thc northward move ment of africa arabia and india relative to eurasia the tectonics of the aegean region itself is dominated by strike slip and extensional motions the actively deforming part of the aegean region is not large about 700 x 700 km2 compared with that in asia yet it has had an influence on our views of continental tectonics disproportionate to its size and comparable perhaps only to tibet fundamental contributions from the aegean have been made to many topics including

a formulation for reliable estimation of active crustal deformation and its application to central greece summary a procedure for the analysis of data concerning seismic moment release and fault plane solutions for the estimation of active crustal deformation is proposed the formulation takes advantage of all the available historical and instrumental data for the calculation of the size of the deformation in a seismic zone and of all the reliable fault plane solutions which are available for a broader seismic belt for the determination of the shape of the deformation a detailed analysis of the errors involved in each parameter based on a monte carlo numerical method is suggested the proposed procedure is applied to a region of extensional tectonics in central greece the resulting seismic strain rates show that the dominant mode of deformation in the area is extension at a rate of the order of 6 mm yr and a mean azimuth of n25 w a vertical contraction rate of about 1 mm yr has also been calculated the results from geodetic measurements performed by billiris et al 1991 declare that the calculated seismic deformation represents about 60 per cent of the total strain of this area

lithospheric boundaries and plate motions in the cyprus area abstract accurate location of earthquakes recorded by seismographs and reliable fault plane solutions of strong recent earthquakes are used to define the plate boundaries and the pattern of plate motion in cyprus and surrounding area spatial distribution of shallow h

neotectonic and seismological data concerning major active faults and the stress regimes of northern greece northern greece is an intracontinental region behind the hellenic subduction zone with widespread seismic activity ranging from low to high with strong destructive earthquakes of mg6 0 in historical to recent times geological and seismological data indicate that recent seismic activity is mainly localized along large inherited fault zones which have transected northern greece since oligocene miocene times the main active fault zones in thrace and eastern and central macedonia strike approximately east west with lengths of 40 120 km fault segments strike wnw ese to ene wsw and range from 10 to 30 km in length in western macedonia the main active fault zones strike ne sw to ene wsw with lengths of 40 60 km and consist of 10 30 km segments the region s strong earthquakes are usually associated with reactivation of these fault segments and are estimated at m 5 6 6 5 focal mechanisms and fault slip data from the fault zones indicate a change in the trend of extension axes from nne ssw in eastern macedonia thrace to nnw sse in western macedonia thus neotectonic and seismological data suggest that variations in fault patterns as determined from the large inherited fault zones transecting northern greece are the major factor governing this change in the trend of maximum extension this interpretation is consistent with the long lived arcuate shape of the hellenic subduction zone of these the best known are the 1978 thessaloniki earthquake of m 6 5 papazachos et al 1979 and the 1995 kozani grevena earthquake pavlides et al 1995 mountrakis et al 1996c 1998 papazachos et al 1998a with the latter occurring in the low seismicity western macedonia region the rupture zones in northern greece need a thorough re examination in the light of recent advances in our understanding of active faulting and the new data provided by the aristotle university seismological network our aim is to identify the large active fault zones in northern greece from their geometric kinematic and seismotectonic features to define controlling stresses and to elucidate the continuity or extent of these zones the main aim is to better understand the active deformation of these areas and to determine whether fault deformation in northern greece is concentrated into relatively narrow bands or zones as one of the major issues in continental mechanics is how fault slips in the upper crust reflect more distributed flow in the lower lithosphere e g mckenzie jackson 1983 molnar gipson 1994 bourne et al 1998 information about active faulting and driving stresses in such areas is very useful brittle deformation within intracontinental regions is usually associated with distributed faulting and seismic activity however within such broad deforming regions some parts although transected by large faults are characterized by relatively less intense seismic activity and slip rates northern greece lies in the inner part of the continental collision region of nw greece and albania close to the intensely north south aegean extended sea this deformation is driven by the hellenic subduction zone and the westward extrusion of anatolia fig 1a in the older greek seismic code some large areas of macedonia e g western macedonia are classified as almost aseismic and other adjacent ones e g central macedonia as highly seismic recent instrumental data obtained from the regional seismological network of the aristotle university of thessaloniki after its installation in 1980 have confirmed the existence of significant seismicity in northern greece fig 1b particularly along narrow rupture zones papazachos et al 2001 furthermore large earthquakes have been reported in historical times papazachos papazachou 2003 and several strong and destructive ones have been recorded instrumentally during the last century 650 d mountrakis et al fig 1 a schematic map showing the position of northern greece in the broader eastern mediterranean geotectonic regime modified from papazachos papazachou 2003 b spatial distribution of instrumentally recorded earthquakes 1911 2004 with magnitudes mg3 0 for the broader study area ctf cephalonia transform fault rtf rhodes transform fault ptf paphos transform fault geology and seismotectonics of northern

gps and geologic estimates of the tectonic activity in the marmara sea region nw anatolia a dense network of 52 global positioning system gps sites is used to determine the velocity field and strain rate pattern at the western end of the north anatolian fault zone nafz in the marmara sea region nw anatolia based on four gps campaigns carried out biannually between 1990 and 1996 the detailed kinematic field of crustal motion is calculated the southernmost station shows an average rate of 22 3 mm yr oriented westward relative to istanbul eurasia this value is indicative of the dextral strike slip motion of nw anatolia relative to the black sea the gps velocity field reveals that the sites located on the thrace black sea block show negligible motion relative to istanbul the gps based deformation pattern of three sections crossing the westward prolongation of the nafz is compared with neotectonic data both the gps and the neotectonic data give clear evidence that most of the deformation occurs along a relatively narrow e w oriented zone this belt extends from the single fault trace of the nafz through the gulf of izmit the marmara sea the arkoy region and the gulf of saros into the north aegean trough nat in addition the cross sections show the increasing influence of the n s oriented extension in the aegean sea region from the comparison of the directions and rates of shear and normal strain deduced from gps data with geologic and seismic observations we conclude that the most active zone of dextral shear follows a line along mudurnu valley the northern marmara sea and the saros trough where it joins the nat

time independent and time dependent seismic hazard in greece based on seismogenic sources abstract an improved procedure is followed to assess time independent andtime dependent hazard for 144 broad sites cities towns villages of greece in termsof expected macroseismic intensities at each one of these sites in this procedureseveral new results are taken into account source parameters based on new researchwork on seismicity and on other relative information new regionalization and im proved seismicity data parameters and anisotropic radiation at the seismic source anew relation for the attenuation of macroseismic intensities and the effect of localconditions site effects on the strong ground motion analytic relations and tables determined by this procedure permit the reliableassessment of time independent hazard in terms of macroseismic intensity in mmscale peak horizontal ground acceleration and velocity at each one of these 144sites and at any probability level time dependent hazard has been also assessed for these 144 broad sites in greece in terms of the probability for the occurrence of strong ground motion with macro seismic intensity i vii in mm scale at each one of these sites during the period1996 2010 comparison of the assessed time dependent hazard with observed ma croseismic intensities of the period 1950 1995 indicates that the time dependentmodel gives very reasonable results introduction

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