present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

new constraints on the active tectonic deformation of the aegean 1 site velocities from six separate global positioning system gps networks comprising 374 stations have been referred to a single common eurasia fixed reference frame to map the velocity distribution over the entire aegean we use the gps velocity field to identify deforming regions rigid elements and potential microplate boundaries and build upon previous work by others to initially specify rigid elements in central greece the south aegean anatolia and the sea of marmara we apply an iterative approach tentatively defining microplate boundaries determining best fit rigid rotations examining misfit patterns and revising the boundaries to achieve a better match between model and data short term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long term kinematics we find that present day aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them the rms misfit of model to data is about 2 sigma very good when compared to the typical match between coseismic fault models and gps data the simplicity of the microplate description of the deformation and its good fit to the gps data are surprising and were not anticipated by previous work which had suggested either many rigid elements or broad deforming zones that comprise much of the aegean region the isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain year nstrain year 10 9 year 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries lower strain rates may exist elsewhere within the microplates but are only resolved in anatolia where extension of 13 4 nstrain year is required by the data our results suggest that despite the detailed complexity of active continental deformation revealed by seismicity active faulting fault geomorphology and earthquake fault plane solutions continental tectonics at least in the aegean is to first order very similar to global plate tectonics and obeys the same simple kinematic rules although the widespread distribution of aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized

active surface deformation and sub lithospheric processes in the western mediterranean constrained by numerical models we present the results of dynamic modeling of the western mediterranean that accounts for observed global positioning system gps surface deformation of the alboran sea and surrounding rif and betic mountains as the result of the combined effects of relative motion of the eurasian and nubian plates low strength in the alboran sea region and sub lithospheric processes occurring beneath the external rif domain assuming that the lithosphere behaves elastically over the short time period of the gps observations an elastic plate model is considered in our study including an area of weak lithosphere factor of 10 centered on the alboran sea and in which lateral boundary conditions consist of the nubia eurasia oblique convergence sub crustal processes are modeled by application of a horizontal traction on a small area patch at the base of the elastic plate our modeling studies demonstrate the need for sub crustal or sub lithospheric southwestward directed forcing to account for observed southwestward motion of the rif and betic domains based on the location orientation and small area of the traction patch we hypothesize that forcing is associated with delamination and rollback of the subducted african continental lithospheric mantle beneath the external rif zone due to the pull of the oceanic part of the western mediterranean slab a dynamic process that may be similar to that where the over riding plate is driven toward the subduction zone during slab rollback

slip distribution of the 2003 boumerdes zemmouri earthquake algeria from teleseismic gps and coastal uplift data 1 using a joint inversion of seismological waveforms and ground displacement observations we estimate several parameters of the fault geometry and rupture process of the mw 6 9 may 21 2003 boumerdes zemmouri earthquake the relocated epicenter is considered as a known parameter total rupture length rupture duration and maximum slip are 55 km from 3 4 e to 4 0 e 12 s and 3 m the modeled south dipping reverse fault oriented ene wsw outcrops a few km offshore which is consistent with the absence of observed surface rupture inland two shallow and relatively localized slip zones are found on both sides of the hypocenter to the sw between boumerdes and zemmouri slip is concentrated between 11 and 2 km depth to the ne between zemmouri and dellys slip is concentrated between 6 km depth and the sea floor various resolution tests indicate that our model is well constrained by the available data and help understanding which data constrains each parameter of the model

cenozoic evolution of neotethys and implications for the causes of plate motions africa north america eurasia plate circuit rotations combined with red sea rotations and new estimates of crustal shortening in iran define the cenozoic history of the neotethyan ocean between arabia and eurasia the new constraints indicate that arabia eurasia convergence has been fairly constant at 2 to 3 cm yr since 56 ma with slowing of africa eurasia motion to 1 cm yr near 25 ma coeval with the opening of the red sea ocean closure occurred no later than 10 ma and could have occurred prior to this time only if a large amount of continental lithosphere was subducted suggesting that slowing of africa significantly predated the arabia eurasia collision these kinematics imply that africa s disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern eurasia slowed its motion the slow steady rate of northward subduction since 56 ma contrasts with strongly variable rates of magma production in the urumieh dokhtar arc implying magma production rate in continental arcs is not linked to subduction rate

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

surface kinematics in the alpine carpathian dinaric and balkan region inferred from a new multi network gps combination solution abstract the understanding of the intraplate tectonics of central europe requires a detailed picture of how stress is transferred from the interaction of the eurasian nubian and anatolian plates to the alpine carpathian pannonian and dinaric regions recent strain distribution is controlled by the adria horizontal push by the vrancea vertical slab pull and associated horizontal displacements and by the aegean anatolia extension and slab roll back we present a horizontal velocity field for the alpine carpathian pannonic dinaric and balkan regions resulting from a new combination of seven different gps networks formed from permanent and campaign stations dedicated velocity profiles in two specific regions are studied in detail one is the alpine pannonian region with a detailed picture of the ns indentation of the adria microplate into the southern alps in ne italy the deformation in the tauern window and the eastwards kinematics of a pannonian plate fragment the second study region includes transylvania the southern carpathians up to the aegean sea and albania where a major right lateral shear deformation exists as a consequence of the ne convergence of the apulia platform towards the dinarids and the ssw motion of macedonia western bulgaria and rumania related to the hellenic arc dynamics in the eastern mediterranean the profiles in the alpine pannonian area indicate that a velocity drop of 2 5 0 4 mm yr associated with the adria indentation concentrates on a segment of some 50 km south of the periadriatic fault the deformation becomes extensional by a similar amount just north of the periadriatic fault in the tauern window where the updoming of the tauern window implies vertical motion which could well be associated with surface extension in the ew profile we observe a sudden velocity change of 1 5 0 2 mm yr in 20 km corresponding to the right lateral lavant fault which seems to mark the border between dominant indentation kinematics to the west and dominant extrusion kinematics to the east three profiles are considered in southern and eastern europe one across the lower adriatic sea from apulia in italy to the southern dinarides which enables it to constrain the velocity drop associated with the subduction of the adria microplate into the dinarides to 3 2 0 5 mm yr in 140 km the second profile is longitudinal and constrains the velocity inversion of 7 4 1 0 mm yr in 350 km associated with right lateral shear faults in albania the third profile crosses the transylvania region with a shortening of 2 3 1 0 mm yr in 220 km and the wallachian moesian region up to the chalcidic peninsula in n greece this lower part of the profile implies an extensional stretch of the upper crust of 3 2 0 9 mm yr in 440 km culminating in the hellenic arc strain rate maps are presented in this regional scale showing the excellent agreement between fault plane solutions of crustal earthquakes and the eigenvectors of the gps derived two dimensional strain rate tensor three profiles are considered in the balkan and se carpathians one across the lower adriatic sea from apulia in italy to the southern dinarides which enables to constrain the velocity drop associated to the subduction of the adria microplate into the dinarides to 3 2 0 5 mm yr in 140 km the second profile is longitudinal and constrains the velocity inversion of 7 4 1 0 mm yr in 350 km associated to right lateral shear faults in macedonia a highly seismic region the third profile crosses the transylvania with a shortening2 3 1 0 mm yr in 220 km and the wallachian moesian region up to the chalcidic peninsula in n greece this lower part of the profile implies an extensional stretch of the upper crust of 3 2 0 9 mm yr in 440 km culminating in the hellenic arc

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

the tripoli libya earthquake of september 4 1974 implications for the active tectonics of the central mediterranean source parameters have been determined for the earthquake ms 5 6 that occurred offshore of tripoli libya on september 4 1974 one nodal plane of its focal mechanism has dip 37 strike 297 and rake 141 indicating oblique normal faulting this nodal plane is subparallel to many west northwest striking normal faults in the epicentral area and is most likely the fault plane indicating a component of right lateral strike slip with slip vector azimuth n84 e inversion of long period teleseismic body waves indicates 12 km centroid depth and 0 4 1018 n m seismic moment a much larger earthquake ms 7 0 on april 19 1935 that occurred in the same zone of active oblique normal faults 400 km farther southeast near sirte probably involved similar slip sense this zone for which the name tunisia libya seismic zone appears appropriate has overall northwest southeast extent 1000 km from northern libya to between tunisia and sicily it takes up a change in motion direction relative to stable europe from west of north inside the african plate to between n30 e and n50 e in the ionian sea between sicily southernmost peninsular italy southwest greece and libya this suggested motion direction of sicily relative to stable europe agrees with independent estimates from fault slip rates and senses elsewhere in italy

widespread extension in the core of the western alps revealed by earthquake analysis the western alps are an active collision belt whose current stress field is inhomogeneous muller et al 1992 we report new seismological data which significantly improve our knowledge of this stress field about 1600 earthquakes which occurred in the western alps during the last 10 years were precisely located and 79 new focal solutions were computed the analysis of this database shows that widespread extension affects all the internal zones of the belt to better constrain the associated stress regime six stress tensors were computed using the gephart and forsyth 1984 method they show that the current tectonics of the western alps are contrasted with close variation in the stress regime transpression to the front of the belt contrasting with extension in the core of the belt the extensional direction is radial to the arcuate geometry of the belt and bounded outboard by the former thrust of the internal zones onto the external zone suggesting extensional reactivation of this inherited crustal discontinuity such widespread extension within the inner part of an actually ongoing collision belt cannot be explained by simple collision related tectonics we propose that intrabelt buoyancy forces such as those produced by a slab retreat or slab break off interfere with the boundary forces driven by the ongoing europe africa convergence

tidal perturbations and variability in the mesopause region over fort collins co 41n 105w continuous multi day temperature and wind lidar observations 1 an unusually long data set was acquired at the sodium lidar facility at colorado state university 41n 105w between sep 18 and oct 01 2003 including a 9 day continuous observation this time is long enough to average out the perturbations of gravity waves and short period planetary waves as such it can be used to define tidal period perturbations in temperature and horizontal wind assuming the sodium mixing ratio is a constant of motion the observed tidal period oscillation in sodium density follows that of vertical wind thus the data set defines tidal period perturbations of temperature and wind vector the observed amplitudes and phases were compared to global scale wave model predictions both gswm00 and gswm02 we found excellent agreement in diurnal phases and reasonable agreement in semidiurnal phases however gswm02 overestimates diurnal amplitudes and both model versions underestimate observed semidiurnal amplitudes since the data period is long enough for the study of planetary waves and of tidal variability we perform spectral analysis of the data revealing a strong quasi 3 day wave in meridional wind a 14 hour perturbation in zonal wind and both 14 hour and 10 hour periods in meridional wind likely the result of nonlinear interactions the observed semidiurnal amplitudes are much larger than the corresponding diurnal amplitudes above 85 km and over a few days the diurnal and semidiurnal amplitudes vary by factors of 2 3 causes for the observed tidal variability in terms of planetary wave modulation and tide gravity wave interaction are explored qualitatively

new gps constraints on the africa eurasia plate boundary zone in southern italy 1 southern italy is a key area for understanding the tectonic processes in the africa eurasia collision zone we analyze new gps measurements carried out between 1994 and 2001 the results are presented in terms of time series trajectories and velocities of crustal motion as well as a geodetic strain rate field while central italy corsica sardinia and the tyrrhenian sea move like the eurasian plate the overall motion of the sicily rift zone region matches african plate motion unexpected are the north northwest directed motions of northeastern sicily and the eolian islands most striking on the deformation field are a north south oriented compression along the northern sicilian coast compression between apulia and northwestern greece as well as extension in the sicily rift zone and the interior of sicily

present day geodynamics in the bend of the western and central alps as constrained by earthquake analysis summary the contrasted tectonics of the western central alps is examined using a synthesis of 389 reliable focal mechanisms the present day strain regime is mapped and interpolated for the entire alpine belt based on a newly developed method of regionalization the most striking feature is a continuous area of extension which closely follows the large scale topographic crest line of the alpine arc thrusting is observed locally limited to areas near the border of the alpine chain a majority of earthquakes within the alps and its forelands are in strike slip mode stress inversion methods have been applied to homogenous subsets of focal plane mechanisms in order to map regional variations in stress orientation the stress state is confirmed to be orogen perpendicular both for 3 in the inner extensional zones and 1 in the outer transcurrent transpressional zones extensional areas are well correlated with the part of the belt which presents the thickest crust as shown by the comparison with the bouguer anomaly and the average topography of the belt in the northwestern swiss alps extension is also correlated with currently uplifting zones these observations and our strain stress analyses support a geodynamic model for the western alps in which the current activity is mostly a result of gravitational body forces earthquakes do not provide any direct evidence for ongoing convergence in the alpine system but a relationship with ongoing activity of complex block rotations of the apulian microplate cannot be ruled out

seismology tectonic strain in plate interiors arising from r smalley jr m a ellis j paul r b van arsdale nature 435 1088 1090 2005 r smalley et al reply it is not fully understood how or why the inner areas of tectonic plates deform leading to large although infrequent earthquakes smalley et al 1 offer a potential breakthrough by suggesting that surface deformation in the central united states accumulates at rates comparable to those across plate boundaries however we find no statistically significant deformation in three independent analyses of the data set used by smalley et al and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present

an analog experiment for the aegean to describe the contribution of gravitational potential energy the southern aegean seafloor exhibits clear evidence of internal deformation stretching as shown by tectonics seismology and space geodesy we use an analog three layer laboratory experiment of sand silicone putty and honey to investigate the deformation of the southern aegean lithosphere the model is installed in a box and confined by a vertical wall we open a gate in the wall and observe the deformation of the two upper layers due to buoyancy forces the general pattern of the deformation of the southern aegean is found in the analog model we observe the formation of an arc spreading outward with time the extension is radial in the inner part but parallel to the arc in the external part and of comparable importance at both ends of the gate we observe strike slip motion dextral in the western part sinistral in the eastern part rotation clockwise in the western part counterclockwise in the eastern part of up to 40 is seen on both sides of the gate but is also present with a smaller amplitude far in the internal region partially due to distributed shear the spreading is associated with the thinning of the two upper layers and affects a region of dimensions comparable to the length of the free boundary this spreading does not propagate inward with time some pieces of material located near the active boundary remain undeformed during the experiment

earthquake induced flooding and paleoseismicity of the el asnam algeria fault related fold late quaternary activity of the el asnam thrust fault responsible for the october 10 1980 ms 7 3 earthquake and 36 km coseismic faulting is explored through diverse paleoseismological field methods we trenched through the main and secondary 1980 coseismic scarps made an analysis of earthquake induced flood deposits conducted a geomorphic study of leveling profiles and offset geological units across thrust and normal scarps and considered the geomorphology of the active fold twenty five radiocarbon ages from colluvial and alluvial deposits along with conventional fossils and artefacts dating of geological units show the timing of successive net vertical displacements on the thrust related fold and bending moment faults previous work showed that eight pre 1980 earthquakes occurred in clusters during the late holocene cumulative net vertical slip that amounts to 3 times the 1980 displacement is observed on multiple thrust fault scarps and offsets of geological units on bending moment faults maximum cumulative vertical displacements which are visible in different zones along the fault segments can reach 10 to 25 times the 1980 coseismic displacements the late quaternary uplift rate on the el asnam fault is 0 6 mm yr and taking into account slip variation along the fault this rate may range between 0 25 1 6 mm yr from which we obtain a shortening rate of 0 17 1 2 mm yr because the tell atlas mountains exhibit comparable seismogenic fault related folds with parallel and sequential structures of active faults a total average shortening rate of 2 05 mm yr during the late quaternary represents part of the convergence accommodated along the africa eurasia plate boundary

geodetic constraints on present day motion of the arabian plate implications for red sea and gulf of aden rifting 1 five years of continuously recording gps observations in the kingdom of saudi arabia together with new continuous and survey mode gps observations broadly distributed across the arabian peninsula provide the basis for substantially improved estimates of present day motion and internal deformation of the arabian plate we derive the following relative geodetic euler vectors latitude n longitude e rate myr counterclockwise for arabia nubia 31 7 0 2 24 6 0 3 0 37 0 01 arabia somalia 22 0 0 5 26 2 0 5 0 40 0 01 arabia india 18 0 3 8 87 6 3 3 0 07 0 01 arabia sinai 35 7 0 8 17 1 5 0 0 15 0 04 and arabia eurasia 27 5 0 1 17 6 0 3 0 404 0 004 we use these euler vectors to estimate present day stability of the arabian plate the rate and direction of extension across the red sea and gulf of aden and slip rates along the southern dead sea fault south of the lebanon restraining bend 4 5 4 7 0 2 mm yr left lateral 0 8 1 1 0 3 mm yr extension and the owens fracture zone 3 2 2 5 0 5 mm yr right lateral increasing from north to south 1 2 mm yr extension on a broad scale the arabian plate has no resolvable internal deformation weighted root mean square of residual motions for arabia equals 0 6 mm yr although there is marginally significant evidence for n s shortening in the palmyride mountains syria at 1 5 mm yr we show that present day arabia plate motion with respect to eurasia is consistent within uncertainties i e 10 with plate tectonic estimates since the early miocene when arabia separated from nubia we estimate the time of red sea and gulf of aden rifting from present day arabia motion plate tectonic evidence for a 70 increase in arabia nubia relative motion at 13 ma and the width of the red sea and gulf of aden and find that rifting initiated roughly simultaneously 2 2 myr along the strike of the red sea from the gulf of suez to the afar triple junction as well as along the west gulf of aden at 24 2 2 ma based on the present kinematics we hypothesize that the negative buoyancy of the subducted ocean lithosphere beneath the makran and the zagros fold thrust belt is the principle driver of arabia eurasia convergence and that resisting forces associated with arabia eurasia continental collision have had little impact on plate motion

visualization of geochemical data for rocks and sediments in google earth development of a data converter application for geochemical and isotopic data sets in database systems we developed a keyhole markup language kml generator for converting geochemical and isotopic data sets for rocks and sediments stored in database systems into kml our program allows users to visualize geochemical or isotopic data easily in google earth the generator accepts data files produced by the database systems petdb seddb georoc and ganseki the data are plotted three dimensionally as a bar graph on the surface of the virtual earth at the sampling site this type of visual presentation including information on sample localities directly shows the distribution of isotopic or compositional anomalies of specific samples on the earth s surface we provide a web application for the generator so anyone can set the parameters for visualization over the internet with other kml generators we developed earlier geochemical data can be overlain on a seismic tomographic model this overlay image can provide information on the origin of samples in the tomographic model

active tectonics of the adriatic region from gps and earthquake slip vectors 1 to investigate the kinematics of the adriatic region we integrate continuous and episodic gps measurements with mw 4 5 earthquake slip vectors selected from the regional centroid moment tensor catalogue coherent motion of gps sites in the po valley in apulia and in the hyblean plateau allows us to estimate geodetically constrained angular velocities for these regions the predictions of the gps inferred angular velocities are compared with the earthquake slip vectors showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion the remarkable consistency between geodetic seismological and geological evidence of active tectonics suggests that active deformation in the central adriatic is controlled by the relative motion between the adria and apulia microplates the microplates angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses 1 that apulia forms a single microplate with the ionian sea and possibly with the hyblean region and 2 that adria and apulia rotate in such a way as to accommodate the eurasia nubia relative motion we suggest that the present day microplate configuration follows a recent fragmentation of the adriatic promontory that during the neogene rigidly transferred the africa motion to the orogenic belts that now surround the adriatic region

the adriatic region an independent microplate within the africa eurasia collision zone 1 we use gps measurements and block modeling to investigate the present day deformation of the adriatic region whose kinematics within the nubia eurasia plate boundary zone is not well constrained and remains controversial block modeling allows us to compute rigid plate angular velocities while accounting for elastic strain accumulation along block bounding faults results suggest that the adriatic is a microplate adria and that the southern boundary with the nubia plate and the aegean domain may be located along the apulia escarpment and the kefallinia fault geodetic data alone cannot discriminate between a single block ap or a two blocks gdap description of adria but the gdap model predicts boundary slip rates that are in better agreement with observations from previous studies

evidence for a post 3 16 ma change in nubia eurasia north america plate motions we combine updated gps velocities from the nubian nu eurasian eu and north american na plates with 500 new 3 16 myr average seafloor spreading rates and nine transform fault azimuths from the northern atlantic and arctic basin seafloor spreading centers to estimate and test for changes in the relative motion between these plates the numerous new seafloor spreading rates and gps velocities improve our ability to detect recent changes in the relative motions of these plates the angular velocity vector that best fits the eu na gps velocities lies significantly north of the 3 ma average pole in accord with previously published geologic evidence that the eu na pole has migrated northward since v3 ma although we also find evidence for a significant post 3 ma change in nu na motion it is less compelling because the nubian plate gps velocity field is sparse and nu na seafloor spreading rates appear to have remained steady within the 1 mm yr 31 uncertainties if we systematically decrease the seafloor spreading rates to correct for outward displacement of seafloor spreading magnetic lineations the nu eu pole derived from gps site velocities lies more than 30 angular degrees south of the tightly constrained 3 ma average estimate and predicts significantly slower and more oblique present day nu eu convergence in the mediterranean both models for nu eu motion pass a key test for their accuracy namely they correctly predict strike slip motion along the well mapped gloria fault east of the azores the change to more oblique nu eu motion may reflect increasing difficulty in maintaining margin normal convergence within this continent continent collision zone 8 2003 published by elsevier b v

current strain regime in the western alps from continuous global positioning system measurements 1996 2001 four to six years of continuous measurements at 10 permanent global positioning system sites in the western alps show horizontal residual velocities of 2 mm yr with respect to stable europe uncertainties range from 0 3 to 1 4 mm yr these velocities and the associated strain rate field indicate that the central part of the range is currently dominated by east west extension whereas the southern part shows north south to northwest southeast compression the geodetic and seismotectonic data are consistent with a model where strain is essentially controlled by the counterclockwise rotation of the adriatic microplate with respect to eurasia this rotation together with the arcuate shape of the contact between the adriatic microplate and the alps induces dextral shear kinematic boundary conditions across the western alps with an additional divergence component in their central part and in switzerland and a convergence component in their southern part

new gps constraints on active deformation along the africa iberia plate boundary abstract we use velocities from 65 continuous stations and 31 survey mode gps sites as well as kinematic modeling to investigate present day deformation along the africa iberia plate boundary zone in the western mediterranean region the gps velocity field shows southwestward motion of the central part of the rif mountains in northern morocco with respect to africa varying between 3 5 and 4 0 mm yr consistent with prior published results stations in the southwestern part of the betic mountains of southern spain move west southwest with respect to eurasia 2 3 mm yr the western component of betics motion is consistent with partial transfer of nubia eurasia plate motion into the southern betics the southward component of betics motion with respect to iberia is kinematically consistent with south to southwest motion of the rif mountains with respect to africa we use block modeling constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures our preferred plate boundary geometry includes one block between iberia and africa including the sw betics alboran sea and central rif this geometry provides a good fit to the observed motions suggesting a wide transpressive boundary in the westernmost mediterranean with deformation mainly accommodated by the gloria azores fault system to the west and the rif tell lineament to the east block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles i extension along the ne sw trending trans alboran shear zone ii dextral strike slip in the betics corresponding to a well defined e w seismic lineament and iii right lateral strike slip motion extending west to the azores and right lateral motion with compression extending east along the algerian tell we interpret differential motion in the rif alboran betic system to be driven both by surface processes related the africa eurasia oblique convergence and sub crustal dynamic processes associated with the long history of subduction of the neotethys ocean lithosphere the dextral slip identified in the betic mountains in southern spain may be related to the offshore fault that produced the great 1755 lisbon earthquake and as such may represent a significant seismic hazard for the west mediterranean region

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

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

forearc extension and slow rollback of the calabrian arc from gps measurements 1 here we describe the horizontal velocities of continuous gps stations in the calabrian arc ca and surrounding regions the appropriate reference frame to evaluate the crustal motion of the ca is considered by assessing the internal deformation and the relative motion of the crustal blocks in the foreland of the apennines ionian maghrebides subduction system we propose that the motion of ca relative to the subducting ionian lower plate is most properly assessed by minimizing the gps velocities in apulia in this reference frame the significant 2 mm yr southeastward motion of the stations on the ionian flank of the ca shows that the arc is still moving towards the trench in agreement with the observations of active shortening in the ioanian wedge this southeastward migration is associated to 1 4 0 3 mm yr e w extension of the forearc in northern calabria comparable with the seismic strain averaged in the last 500 years the limited subaerial exposure decreases the resolution on locking of the subduction interface but the distribution and direction of crustal extension along the ca impose important constraints on geodynamic interpretations of the area

instantaneous global plate motion model from 12 years of continuous gps observations 1 we estimate a global plate motion model for 17 major and minor tectonic plates solely on the basis of analysis of data from 106 globally distributed continuous gps stations spanning the period from january 1991 to july 2003 site positions estimated from 24 hour segments of data are aligned day by day to the international gps service igs realization of the itrf2000 reference frame using a similarity transformation thereby ensuring that the itrf2000 no net rotation condition is preserved linear velocities of a carefully selected set of stations are estimated from the position time series along with annual and semiannual fluctuations and position offsets due to gps instrument changes a white noise plus flicker noise model is applied to estimate realistic uncertainties for the site velocities which are then propagated into the derived plate motion model parameters we also examine the vertical velocities in the site selection process at the scripps orbit and permanent array center we have implemented a procedure whereby the plate motion model is updated on a regular monthly basis to improve its precision and reliability as new data become available and as a baseline against which anomalous motions can be detected

on the post 25 ma geodynamic evolution of the western mediterranean during the neogene and quaternary western mediterranean geodynamics were dominated by the eastward migration of the apenninic arc and associated back arc basins the migration was controlled by retreat of the apenninic slab and was associated with boudinage of the lithosphere in the back arc area palaeo reconstruction of the kinematics of the arc suggests about 775 km of migration from the late oligocene to present along a transect from the gulf of lions to calabria a maximum of 135 km of n s converge occurred between africa and europe during the same time span the western mediterranean was thus mainly shaped by the migration of the slab related to west directed subduction it is hypothesized that minor n s convergence deformed the arc but was not the cause of its formation 1998 elsevier science b v all rights reserved