a subducting seamount beneath the nankai accretionary prism off shikoku southwestern japan a multi channel seismic mcs reflection survey was conducted to study the structure of the nankai convergent margin off shikoku island in july 1997 based on reflection characteristics we could identify three major seismic reflection units i e units a b and c the mcs data as well as swath bathymetric data reveal a buried circular seamount subducting beneath the nankai accretionary prism the subducting seamount is responsible for deformation of the accretionary wedge resulting in a compressed uplifted sediment knoll and many steep escarpments with ne sw strike a possible thrust fault was identified on the seaward flank of the seamount indicating compressive deformation a tectonic model for subduction of the seamount is presented based on the interpretation of the mcs data

kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern mediterranean region since the late cretaceous the relationship between subduction dynamics and crustal deformation in the mediterranean region has been recently studied using three dimensional 3d numerical models such models require however a detailed information concerning the past geological evolution we use stratigraphic petrologic metamorphic structural paleomagnetic and magmatic data to build new kinematic reconstructions of the eastern mediterranean region since the late cretaceous using the principle of non rigid domains the motions of the 56 deforming domains defined in this work are calculated based on published paleomagnetic rotations the directions and amounts of displacement on crustal scale shear zones and the burial and exhumation histories of the main metamorphic units extracted from these reconstructions paleotectonic maps and lithospheric scale cross sections illustrate that the present day subduction zone has been continuously retreating southward since the late cretaceous and has accreted several small continental domains in the process we find evidence for two back arc related extensional events 1 slow extension along the balkans and the pontides in the late cretaceous while the trench was long and linear and 2 faster extension in the rhodope aegean west anatolian region since the eocene oligocene rapid rotation of the hellenides between 15 and 8 ma probably indicates a slab tearing event below western anatolia that could have further accelerated this extensional kinematics spatial distribution and the geochemical signature of magmatic centers integrated in these reconstructions allow us to trace mantle related processes revealing the deep dynamics that controls both the magma genesis and the crustal deformation

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

a no net rotation model of present day surface motions a significant portion of the earth s surface consists of zones of diffuse deformation the interior regions of these diffuse zones of deformation move at distinctly different velocities from that of adjacent plates and because of their complexities have been ignored in previous no net rotation nnr models we have calculated a new nnr model from a continuous velocity field that incorporates both rigid plate motion and velocity gradients within plate boundary zones when compared with earlier nnr models we find significantly different angular velocities for many plates differences between the nnr model presented here and earlier nnr models can be attributed to the effect of including velocity gradients in diffuse plate boundary zones as well as to the actual differences between geodetically derived surface motions and geologic estimates

strain distribution over the east mediterranean ridge a synthesis incorporating new sea beam data abstract we present the results of several multi narrow beam sea beam traverses of the mediterranean ridge on board r v jean charcot these results can be considered to be complementary in resolution and coverage to the previously published long range side scan sonar gloria results a characteristic of the mediterranean ridge is the presence over about half of its surface of an extensive fold system affecting the messinian and plio quaternary cover which is dissected by conjugate strike slip faults the resolution of sea beam was used to map the main characteristics of folding and faulting this analysis together with previously available data enables us to define the strain pattern over the mediterranean ridge we thus now have an overall view of the strain pattern from a marginal basin aegea through the hellenic trench and adjacent sea floor to the opposite continent the bottom of the hellenic trench is a boundary between an extensional domain to the north and a compressional one to the south the southern domain is strongly affected by the presence of the lybian promontary it is related to the formation of an accretionary ridge due to the inability of the upper 3 4 km of sediments to subduct this ridge is similar to the accretionary prism but it is much wider with respect to its height probably because of the existence of a decollement over a level of overpressure the hellenic trench then is in the situation of a fore arc basin its origin is due to the fact that the aegean continental slope is not vertical but rather has a small 4 dip as a result a sedimentary wedge symmetric but shorter than the main accretionary wedge develops over the buried portion of the slope it is characterized by landward thrusts such an origin probably applies to fore arc basins in general

rate of outward growth of the mediterranean ridge accretionary complex abstract the position as a function time of the deformation front on the southwest flank of the mediterranean ridge accretionary complex is constrained as follows 1 a the deformation front is now active 2 b the site of core ban84 05gc was still near the abyssal plain when displaced shallow water benthic foraminifera of inferred african provenance were redeposited within an upper pliocene age unit 3 c the site of core ban84 05gc on the outer flank of the mediterranean ridge was already within the topographically rugged accretionary complex when a pliocene debris flow was emplaced 4 d dsdp site 125 had already been uplifted into a topographically elevated position when lower pliocene pelagic ooze was deposited 5 e a gypsum bearing breccia in dsdp site 125 requires that the site was either on the abyssal plain or within the tectonically active outer perimeter of the accretionary complex during the messinian salinity crisis 6 f dsdp site 377 had already been uplifted into a topographically elevated position when middle miocene age pelagic marl was deposited 7 g dsdp site 377 was still on or near the abyssal plain when early to lower middle miocene age smectite bearing turbidites of inferred african provenance were deposited and 8 h the mediterranean ridge began to grow by offscraping against a backstop formed by the alpine nappes of the hellenic arc at the time that subduction began 33 ma together these constraints define a range of potential growth curves for the mediterranean ridge with a rate of outward growth of approximately 0 5 to 2 cm yr this growth rate is faster than that inferred for most other modern accretionary prisms both as an absolute value and as a fraction of the subduction velocity an unusually thick incoming section and or an unusually weak evaporitic decollement may contribute to the rapid growth rate the inferred age of accretion does not increase linearly with distance from the deformation front rather there is an apparent acceleration of the rate of outward growth through time this observation may reflect a true acceleration of growth rate in response to the onset of back arc extension in the overriding plate aegean sea and or in response to the development of a weak basal decollement following the introduction of halite into the incoming stratigraphic section alternatively the non linearity of the age vs distance curve may indicate that shortening of the offscraped sediments continues across the breadth of the mediterranean ridge rather than being confined to the outer flank

identifying the origin of groundwater samples in a multi layer aquifer system with random forest classification summary accurate identification of the origin of groundwater samples is not always possible in complex multilayered aquifers this poses a major difficulty for a reliable interpretation of geochemical results the problem is especially severe when the information on the tubewells design is hard to obtain this paper shows a supervised classification method based on the random forest rf machine learning technique to identify the layer from where groundwater samples were extracted the classification rules were based on the major ion composition of the samples we applied this method to the campo de cartagena multi layer aquifer system in southeastern spain a large amount of hydrogeochemical data was available but only a limited fraction of the sampled tubewells included a reliable determination of the borehole design and consequently of the aquifer layer being exploited added difficulty was the very similar compositions of water samples extracted from different aquifer layers moreover not all groundwater samples included the same geochemical variables despite of the difficulty of such a background the random forest classification reached accuracies over 90 these results were much better than the linear discriminant analysis lda and decision trees cart supervised classification methods from a total of 1549 samples 805 proceeded from one unique identified aquifer 409 proceeded from a possible blend of waters from several aquifers and 335 were of unknown origin only 468 of the 805 unique aquifer samples included all the chemical variables needed to calibrate and validate the models finally 107 of the groundwater samples of unknown origin could be classified most unclassified samples did not feature a complete dataset the uncertainty on the identification of training samples was taken in account to enhance the model most of the samples that could not be identified had an incomplete dataset

kinematics of active deformation in the sulaiman lobe and range pakistan the western margin of the indian plate is highly oblique to the direction of convergence between india and asia and represents an excellent example of large scale oblique continent continent collision determining the strain field in western pakistan and how it relates to the plate motion and plate margin geometry affords an exceptional opportunity for understanding oblique margin processes in general through the inversion of regional and teleseismic body waves we have determined the source parameters of 10 moderate sized earthquakes that occurred between 1964 and 1985 in and around the sulaiman range pakistan the earthquakes are dominantly thrust events with slip vectors that are approximately perpendicular to the lobate sulaiman mountain front slip vector orientations rotate 60 70 from a n s to a wnw ese direction of compression consistent with the geometries of the complex festoon shaped mountain belts of this margin we have estimated the spatial variation of the horizontal strain rate and velocity fields within sulaiman using vertically averaged models that accommodate plate motion constraints within a deforming layer the most important factors determining the style of strain rotation in the sulaiman lobe and range are the presence of pure strike slip motion along the chaman fault and the relatively rigid and undeformed katawaz basin that is therefore allowed to translate obliquely relative to india this same conclusion is obtained using either a three dimensional frictional analogue model with significant basal tractions or a thin sheet viscous numerical model without basal tractions thrusting in a predominantly nw se direction in the sulaiman range accommodates 5 14 mm yr of n s motion between india eurasia and 3 6 mm yr of e w shortening seismic moment release this century within the india eurasia plate boundary zone west of the western himalayan syntaxis constitutes roughly 40 of the expected total seismic moment release for this time period particularly significant moment rate deficits exist within the sulaiman range and along the chaman fault

crustal strain in central greece from repeated gps measurements in the interval 1989 1997 summary a 66 station gps network spanning central greece first observed in 1989 has been occupied fully on three occasions june 1989 october 1991 and may 1993 subsets of this network bounding the gulf of korinthos have also been occupied in june 1995 october 1995 may 1996 and september october 1997 the first three occupations were processed using a fiducial gps methodology whereas later surveys were processed using code precise orbits combination of data from different surveys to yield smooth site velocities requires global network translations at each epoch to compensate for errors in the realization of the reference frame this method provides a posteriori estimates of the relative coordinate errors and reference frame noise only one earthquake the 1995 june 15 egion event has caused significant local coseismic displacement and its effects on the interseismic velocity field are removed using an elastic dislocation model we constrain the orientation of the 100 yr triangulation gps velocity estimates of davies et al 1997 using 14 sites common to the two networks the goodness of fit of this transformation indicates that the short term and 100 yr geodetic estimates of deformation are highly compatible we infer that short term geodetic studies are capable of determining longer term deformation rates provided that transient local effects can be modelled from the combined velocity field we estimate principal strains and rigid body rotation rates at points on a regular grid using data from neighbouring sites strain rates are high within the gulf of korinthos and much lower elsewhere the extension rate across the gulf of korinthos increases from east to west comparison of the extension rate with historical and recent rates of seismic release of strain reveals significant medium term seismic hazard in the western gulf of korinthos and may also indicate long term aseismic strain

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

deformational styles of the eastern mediterranean ridge and surroundings from combined swath mapping and seismic reflection profiling abstract recent swath mapping and seismic reflection profiling across the eastern levantine branch of the mediterranean ridge mr in the eastern mediterranean sea illustrate a strong variability of the deformational styles that characterize this precollisional accretionary prism along a north south cross section of the mr a structural analysis based on surface mapping combined with vertical seismic reflection data reveals two main structural domains a southern outer domain consists of a series of three disconnected distinct fold belts folding affects a sedimentary cover which includes an approximately 2 km thick pliocene and quaternary wedge in this domain resting on fairly thick messinian evaporitic sequences that act as probable decollement layers the mr inner domain includes three regions showing evidences of strong internal deformations and of numerous probable mud cones and mud flows but no seismic evidence of significant underlying messinian evaporites can be detected the inner sub regions are thrusting northwards over an area made of faulted and locally uplifted acoustic basement blocks that constitute the southernmost extension of the crete continental margin acting as a continental buttress for the mr this innermost domain is itself structurally disconnected from the crete continental margin by the en echelon pliny troughs system that shows evidence of left lateral displacement altogether the different structural and sedimentary cover patterns reveal a strong contrast between both mr inner and outer domains and important lateral variations within the inner mr itself strike slip faulting seams to characterizes both areas and large scale mud accumulations potentially exist in the northern one our results support a model of imbricated accretionary prisms including at least two stages 1 a pre messinian stage during which the inner mr probably developed in response to northward subduction of the african lithosphere beneath southern europe and 2 a messinian to post messinian period during which the kinematics of the aegean anatolian microplates and the presence of thick messinian deposits became prevalent and which led to the creation of the outer mr folded wedge piling against the previous one in our interpretation the occurrence of thick messinian evaporites in this area induces important local and regional modifications of the structural pattern strike slip activities reflect partitioning related to oblique subduction and likely lateral escape of the sedimentary cover in the whole studied area

from foreland to forearc domains new multichannel seismic reflection survey of the mediterranean ridge accretionary complex eastern mediterranean abstract the mediterranean ridge of the eastern mediterranean sea is a huge accretionary wedge emplaced as a consequence of the africa aegean plate convergence that has a rate estimated at 40 mm yr processing of recent multichannel seismic data and integration with previous results seismic profiling swath bathymetry sonar have facilitated the study of the overall deformation pattern of the area which includes three distinct major structural domains facing various forelands 1 1 the outer domain is bounded southward by the present day wedge toe and towards the north by topographic slope breaks and clear changes in deformational style beneath the ionian and levantine mediterranean ridge branches the base of messinian evaporites seems to act as a major decollement level 2 2 the central or crestal domain the shallowest one shows evidence of mud diapiric and mud volcano activity and is overthrusting northward over the inner domain facing the libyan margin this area which displays spectacular mud volcano fields appears much wider and shallower 3 3 the less deformed inner domain is bounded northward by the hellenic trench system beneath its ionian inner area seismic velocities characteristic of continental crust have been recorded while within its levantine region it is made of a series of disconnected and uplifted basement blocks strabo seamounts along the matapan and pliny trenches structures which could be caused by transpressive deformation are locally observed we believe that both the north south structural arrangement and the clear west east lateral variations of the mediterranean ridge relate to its progressive collision against the libyan margin promontory this event which may have initiated 5 6 myr ago may have induced a a differentiated paleogeography of messinian evaporites later available for tectonic accretion leading to the further lateral structural variations of the outer domain and b strain partitioning between the central mediterranean ridge and the hellenic trench system

influence of granite mineralogy rainfall vegetation and relief on stream water chemistry vosges mountains north eastern france abstract the influence of rock mineralogy climate vegetation and relief on stream water composition and export as a result of weathering is a major scientific concern both at the local scale because of the link between stream chemistry and biodiversity and at the global scale in relation to global climate changes environmental factors influencing stream chemistry at baseflow were studied for 95 forested catchments located in the granite part of the vosges mountains ne france mean annual rainfall slope altitude catchment area forest cover and granite composition were attributed to each catchment using a geographic information system gis and spatially distributed databases these variables were then used to model stream water concentrations in so4 ca mg k na si anc acid neutralizing capacity and ph via linear regression analyses sulfate concentration is mainly negatively correlated to the mean altitude of the catchment silica and na concentrations are strongly correlated and negatively related to the mean annual rainfall and not to altitude ph is positively related to the sum of ca mg and k but not to so4 for any type of granite ca mg and ph are generally negatively related to the mean annual rainfall and positively related to the catchment area calcium is best explained by the rock content in hornblende mg by the rock contents of biotite and hornblende k by the content in k feldspar nevertheless models differ for each granite type in relation to the availability of weatherable minerals and probably to water pathways this study shows the interest of spatial analysis methods for understanding stream water concentrations at the mountain range scale in combination with local process studies and modelling at the catchment scale

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

automated upscaling of river networks for macroscale hydrological modeling 1 we developed a hierarchical dominant river tracing drt algorithm for automated extraction and spatial upscaling of basin flow directions and river networks using fine scale hydrography inputs e g flow direction river networks and flow accumulation in contrast with previous upscaling methods the drt algorithm utilizes information on global and local drainage patterns from baseline fine scale hydrography to determine upscaled flow directions and other critical variables including upscaled basin area basin shape and river lengths the drt algorithm preserves the original baseline hierarchical drainage structure by tracing each entire flow path from headwater to river mouth at fine scale while prioritizing successively higher order basins and rivers for tracing we applied the algorithm to produce a series of global hydrography data sets from 1 16 to 2 spatial scales in two geographic projections wgs84 and lambert azimuthal equal area the drt results were evaluated against other alternative upscaling methods and hydrography data sets for continental u s and global domains these results show favorable drt upscaling performance in preserving baseline fine scale river network information including 1 improved automated extraction of flow directions and river networks at any spatial scale without the need for manual correction 2 consistency of river network basin shape basin area river length and basin internal drainage structure between upscaled and baseline fine scale hydrography and 3 performance largely independent of spatial scale geographic region and projection the results of this study include an initial set of drt upscaled global hydrography maps derived from hydro1k baseline fine scale hydrography inputs these digital data are available online for public access at ftp ftp ntsg umt edu pub data drt

research note insights into the data dependency on anisotropy an inversion prospective while velocity contrasts are responsible for most of the events recorded in our data the long wavelength behavior of the velocity model is responsible for the geometrical shape of these events for isotropic acoustic materials the wave dependency on the long wave propagation and short scattering wavelength velocity components is stationary with the propagation angle on the other hand in representing a transversely isotropic with a vertical symmetry axis medium with the normal moveout velocity the anellepticity parameter the vertical scaling parameter and the sensitivity of waves vary with the polar angle for both the long and short wavelength features of the anisotropic dimensionless medium parameters and for horizontal reflectors at reasonable depths the long wavelength features of the model is reasonably constrained by the long offsets whereas the short wavelength features produce very week reflections at even reasonable offsets thus for surface acquired seismic data we could mainly invert for smooth responsible for the geometrical shape of reflections on the other hand while the long wavelength components mildly affects the recorded data its short wavelength variations can produce reflections at even zero offset with a behavior pattern synonymous to density the lack of the long wavelength information will mildly effect focusing but will cause misplacement of events in depth with low enough frequencies very low we may be able to recover the long wavelength using full waveform inversion however unlike velocity the frequencies needed for that should be ultra low to produce long wavelength scattering based model information as perturbations do not exert scattering at large offsets for a combination given by the horizontal velocity and the diving wave influence of is absorbed by the horizontal velocity severely limiting the influence on the data and full waveform inversion as a result with a good smooth estimation for example from tomography we can focus the full waveform inversion to invert for only the horizontal velocity and maybe as a parameter to fit the amplitude this is possibly the most practical parametrization for inversion of surface seismic data in transversely isotropic with vertical symmetry axis media

use of regression based models to map sensitivity of aquatic resources to atmospheric deposition in yosemite national park usa 1 an abundance of exposed bedrock sparse soil and vegetation and fast hydrologic flushing rates make aquatic ecosystems in yosemite national park susceptible to nutrient enrichment and episodic acidification due to atmospheric deposition of nitrogen n and sulfur s in this study multiple linear regression mlr models were created to estimate fall season nitrate and acid neutralizing capacity anc in surface water in yosemite wilderness input data included estimated winter n deposition fall season surface water chemistry measurements at 52 sites and basin characteristics derived from geographic information system layers of topography geology and vegetation the mlr models accounted for 84 and 70 of the variance in surface water nitrate and anc respectively explanatory variables and the sign of their coefficients for nitrate included elevation positive and the abundance of neoglacial and talus deposits positive unvegetated terrain positive alluvium negative and riparian negative areas in the basins explanatory variables for anc included basin area positive and the abundance of metamorphic rocks positive unvegetated terrain negative water negative and winter n deposition negative in the basins the mlr equations were applied to 1407 stream reaches delineated in the national hydrography data set for yosemite and maps of predicted surface water nitrate and anc concentrations were created predicted surface water nitrate concentrations were highest in small high elevation cirques and concentrations declined downstream predicted anc concentrations showed the opposite pattern except in high elevation areas underlain by metamorphic rocks along the sierran crest which had relatively high predicted anc 200 eq l 1 maps were created to show where basin characteristics predispose aquatic resources to nutrient enrichment and acidification effects from n and s deposition the maps can be used to help guide development of water quality programs designed to monitor and protect natural resources in national parks

sources of weathering derived solutes in two granitic catchments with contrasting forest growth chemical weathering is one of the controlling factors for landform evolution here we present deductions about the location and rate of chemical weathering within catchments based on chemical observations of soil water groundwater springs and streams in two granitic catchments with contrasting forest growth conditions forested and non vegetated and soil development the two catchments are located in the tanakami mountains of central japan and share the same climate in both catchments sio2 and na are the dominant weathering derived solutes in the first order stream using hydrological evidence the contribution to the sio2 and na fluxes from soil and bedrock were partitioned despite the difference in mean soil depth net fluxes of sio2 and na from the soil profile do not differ much between the two catchments suggesting low levels of easily weatherable minerals in the forest soil net sio2 and na fluxes from bedrock are about three times greater in the forested catchment than in the bare catchment and these differences contribute largely to the difference in net fluxes from the catchments net fluxes of sio2 and na from the forested catchment are about twice those from the bare catchment part of this increase may be related to the greater proton production in forested catchment consequently about 60 to 70 of the net sio2 and na fluxes from the non vegetated catchment and 70 to 90 from the forested catchment are derived from bedrock suggesting that the contribution of bedrock to the export of these weathering products increased with forest growth and soil formation copyright 2004 john wiley sons ltd

structural architecture of the rhodes basin a deep depocentre that evolved since the pliocene at the junction of hellenic and cyprus arcs eastern mediterranean abstract interpretation of 1500 km of multi channel seismic reflection profiles shows that the rhodes basin evolved in two distinct tectonic stages a protracted miocene convergence episode p1 resulted in the development of a mainly sse verging fold thrust belt this period corresponds with the emplacement of the lycian nappes to the northeast and fold thrust complexes on the island of rhodes to the west this phase of deformation ceased in the late miocene the absence of evaporites in the rhodes basin suggests that this region must have remained above the depositional base of marine evaporite environment during the messinian the morphology of the m reflector and the architecture of the lowermost pliocene growth strata in the central portion of the rhodes basin demonstrate the existence of rugged paleo relief over the pre existing miocene fold thrust belt in early pliocene the middle pliocene quaternary phase of deformation is characterised by ne sw sinistral transpression p2 and rapid regional subsidence the p2 deformation occurred in response to an actively curving hellenic arc and the increasing obliquity of its eastern limb the pliny strabo trenches or fault zones to the convergence vector of the african plate during this time the p1 structures became re activated as transpressional faults further facilitating the rapid subsidence we envisage the evolution of the rhodes basin as the result of subsidence associated with loading of the large imbricate thrust panels that carry the western tauride mountains in the north at present the pliny strabo fault zones are delineated as a ne sw trending 30 50 km wide zone that continue into the western segment of the rhodes basin this fault zone is further correlated with the similar trending 50 km wide burdur fethiye fault zone in southwestern turkey

global positioning system gps estimates of crustal deformation in the marmara sea region northwestern anatolia abstract in the marmara sea region the relative motion between the anatolian and eurasian lithosphere has been measured by means of the modern techniques of space geodesy using the global positioning system gps in order to resolve in detail the kinematic field within the active earthquake belts of northwestern anatolia two gps campaigns were carried out across a dense network consisting of 45 sites preliminary results reveal horizontal westward motion of anatolia relative to eurasia of 2 4 cm y on average that runs along the western end of the north anatolian fault zone e w oriented right lateral strike slip movement average 0 06 ppm y maximum 0 13 ppm y 1ppm y 1 strain y and ne sw extension average 0 06 ppm y maximum 0 21 ppm y can be obtained from the calculated strain field in the west strike slip motion trending wsw ene is observed these findings are compared to the stress pattern derived from seismology and neotectonics

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

reproducing the velocity and stress fields in the aegean region recent satellite geodetic measurements help to clearly define the velocity field in the aegean anatolian area the velocity field can be broadly characterized by anticlockwise rotation of this region relative to eurasia around a pole located at lat 32 73 long 32 03 north of the egyptian shoreline studies of the fault kinematics in the region also provide information on the time evolution of the stress field in this work we model deformation in the aegean anatolian region to better understand the tectonic origin of the observed stress and velocity fields we found that the observed deformation pattern can be well reproduced by imposing simple boundary conditions including 1 northward displacement of the arabian plate 2 locking of eastward motion in northwestern greece and 3 suction force at the hellenic trench the observed variation in the stress field occurred at 0 9 ma can be partially explained by a change in the activity of the north anatolian fault

on the consistency of earthquake moment rates geological fault data and space geodetic strain the united states new and dense space geodetic data can now map strain rates over continental wide areas with a useful degree of precision stable strain indicators open the door for space geodesy to join with geology and seismology in formulating improved estimates of global earthquake recurrence in this paper 174 gps vlbi velocities map united states strain rates of 30 0 10 8 yr 1 with regional uncertainties of 5 to 50 per cent kostrov s formula translates these strain values into regional geodetic moment rates two other moment rates m seismic and m geologic extracted from historical earthquake and geological fault catalogues contrast the geodetic rate because m geologic m seismic and m geodetic derive from different views of the earthquake engine each illuminates different features in california the ratio of m geodetic to m geologic is 1 20 the near unit ratio points to the completeness of the region s geological fault data and to the reliability of geodetic measurements there in the basin and range northwest and central united states both m geodetic and m seismic greatly exceed m geologic of possible causes high incidences of understated and unrecognized faults probably drive the inconsistency the ratio of m seismic to m geodetic is everywhere less than one the ratio runs systematically from 70 80 per cent in the fastest straining regions to 2 per cent in the slowest although aseismic deformation may contribute to this shortfall i argue that the existing seismic catalogues fail to reflect the long term situation impelled by the systematic variation of seismic to geodetic moment rates and by the uniform strain drop observed in all earthquakes regardless of magnitude i propose that the completeness of any seismic catalogue hinges on the product of observation duration and regional strain rate slowly straining regions require a proportionally longer period of observation characterized by this product gamma distributions model statistical properties of catalogue completeness as proxied by the ratio of observed seismic moment to geodetic moment i find that adequate levels of completeness should exist in median catalogues of 200 to 300 year duration in regions straining 10 7 yr 1 comparable to southern california similar levels of completeness will take more than 20 000 years of earthquake data in regions straining 10 9 yr 1 comparable to the southeastern united states predictions from this completeness statistic closely mimic the observed m seismic to m godetic ratios and allow quantitative responses to previously unanswerable questions such as what is the likelihood that the seismic moment extracted from an earthquake catalogue of x years falls within y per cent of the true long term rate the combination of historical seismicity fault geology and space geodesy offers a powerful tripartite attack on earthquake hazard few obstacles block similar analyses in any region of the world

the rhodes basin a post miocene tectonic trough abstract new light is shed on the enigmatic rhodes deep marine basin by a set of underway geophysical data across it including swath bathymetry seismic reflection profiles gravity and magnetic data this deep trough as much as 4485 m to the east of the island of rhodes and close to southwestern turkey contains no messinian evaporites and only a thin pliocene quaternary sedimentary section

geological and land use control on δ34s and δ18o of river dissolved sulfate the moselle river basin france abstract the upper part of the moselle river basin northeastern france shows contrasting lithology and topography granitic formations upstream in the vosges mountains and carbonate platform downstream on the lorraine plateau we measured concentration and isotopic composition of dissolved so 4 in the moselle river and its main tributaries in order to identify the sources of sulfate rainwater lichens s fertilizers and natural gypsum were also analyzed as potential sulfate sources along the moselle river dissolved so 4 concentrations and s o isotopes display relationships which suggest two major sources of sulfates 1 a low concentration and low delta values 34 s of 6 9 and 18 o of 6 9 component upstream and 2 a high concentration and high delta values 34 s of up to 17 and 18 o of up to 13 these are likely 1 atmospheric s input with some retention time in forest soils as carbon bonded sulfur and 2 sulfates from the dissolution of evaporites from the muschelkalk and keuper formations of the lorraine plateau the madon tributary drains a basin largely used for agriculture 35 of the land surface and formed by carbonate and evaporite rocks deviation from the general 34 s 18 o trend for dissolved so 4 was found to be seasonal and related to land use and agricultural practices and are interpreted as a significant input of sulfates from fertilizers used in the area isotope mixing models indicate that between 1 1 10 7 and 1 9 10 7 mol of anthropogenic so 4 are annually exported through the madon river these values compared well with the expected annual fertilizer spreading rates in the area and demonstrate the powerful source tracing done by using s isotopes in dissolved sulfates this implies that combining isotopic fingerprinting approach to knowledge of the catchment i e land use agricultural practices river flow would provide key information for decision makers in the context of river basin management

structure of the mediterranean ridge accretionary complex from seismic velocity information seismic velocities obtained from ocean bottom hydrophone expanding spread profile and multi channel seismic data were used to compile a velocity model for the mediterranean ridge along a 220 km long transect extending from the sirte abyssal plain to the cleft region near the hellenic trough a 200 300 m thin layer of plio quaternary sediments with velocities of 1800 2200 m s 1 covers the whole ridge the messinian evaporites 4000 4500 m s 1 occur in the southwest as a tectonically thickened layer and in a basin just northeast of the crest of the ridge in the intervening region however the evaporites appear absent and the seismic velocities are generally lower arched reflectors imaged in the depth migrated section suggest that the sediments beneath the ridge crest belong to a pre messinian accretionary wedge beneath the messinian evaporites a northeastward thinning layer of probable tertiary sediments shows laterally increasing velocities from 3300 m s 1 to 4600 m s 1 assuming that the layer thinning is caused by compaction due to increased overburden alone we have calculated a porosity reduction from 15 to 4 and an associated fluid expulsion of 10 km3 km 1 along the trench axis this corresponds to c 60 of the initial fluid volume of an undeformed sediment column from the abyssal plain the almost impermeable evaporitic cap over these sediments leads to high fluid pressures at the base of the evaporites likely to make this horizon the basal decollement of the modern accretionary system a 2 5 km thick unit of probable mesozoic carbonates with velocities of 4500 4600 m s 1 is inferred at c 8 km depth the top of the oceanic crust occurs at a depth of about 10 km the results from this study have widespread implications for the understanding of the regional geological history

effect of subducting sea floor roughness on fore arc kinematics pacific coast costa rica fault kinematics and uplift in the costa rican fore arc of the middle america convergent margin are controlled to a large extent by roughness on the subducting cocos plate along the northwest flank of the incoming cocos ridge seafloor is characterized by short wavelength roughness related to northeast trending seamount chains onland projection of the rough subducting crust coincides with a system of active faults oriented at high angles to the margin that segment the fore arc thrust belt and separate blocks with contrasting uplift rates trunk segments of pacific slope fluvial systems typically follow these margin perpendicular faults regionally developed marine and fluvial terraces are correlated between drainages and across faults along the costa rican pacific coast terrace separations across block bounding faults reveal a pattern of fore arc uplift that coincides roughly with the distribution of incoming seamounts magnitude and distribution of quaternary uplift along the costa rican pacific coast suggests that despite a thin incoming sediment pile the inner fore arc shows an accumulation of mass a characteristic that may be due to underplating of seamounts beneath the fore arc high

contemporary horizontal velocity and strain rate fields of the pacific australian plate boundary zone through new zealand we have inverted velocity solutions from nine geodetic networks distributed across new zealand to derive present day continuous horizontal velocity and strain rate fields at the earth s surface throughout the country the nine networks contain a total of 362 global positioning system gps stations that have been observed at least twice and at least a year apart between 1991 and 1998 the model velocity field is expanded as bicubic spline interpolation functions defined within a curvilinear grid that covers the country and extends into the assumed rigid australian and pacific plates to west and east the inversion jointly minimizes the magnitudes of fitted strain rates and the misfit to the observed velocity data the spline technique allows high spatial resolution of strain rate variations especially in regions with spatially dense gps data expansion of the model velocity field on the surface of a sphere allows arbitrarily large areas to be studied previously known aspects of new zealand plate boundary deformation are highlighted with improved resolution including back arc extension in the taupo volcanic zone rotation of the hikurangi forearc away from this zone in the north island and a band of high shear strain rate under the southern alps to the southeast of the alpine fault our results reveal several new features including a region of enhanced shear straining apparently associated with strike slip faults in the southern north island and a band of contractional straining subparallel and well east of the alpine fault that is similar to features found in numerical and sandbox models of continental collision

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

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

solute flux and mineral mass balance approaches to the quantification of plant effects on silicate weathering the weathering of calcium and magnesium silicate minerals on the continents has exerted a major control on atmospheric co 2 over geologic time and vascular plants may have played an important role in this process we have examined the role of plants in weathering in western iceland by two methods a solute flux approach and a mineral mass balance approach using the chemistry of weathering products and of waters draining adjacent areas of basaltic rocks that are either barren with a partial cover of mosses and lichens or populated by trees the study area was chosen to maximize vegetational differences and to minimize differences in microclimate slope and lithology while avoiding hydrothermal waters and anthropogenic acid rain solute flux results including data on cation uptake by growing trees indicate that the rate of weathering release of ca and mg to streams is about 4 times higher in vegetated areas than in bare areas mineral mass balance results show that trees increase plagioclase weathering by a factor of 2 and pyroxene weathering by a factor of 10 possibly as a result of preferential weathering of pyroxene by the vegetation biomass normalized weathering fluxes from the birch trees are greater than those from the conifers suggesting that angiosperms enhance weathering to a greater degree than gymnosperms results indicate a perpetual short term sink for atmospheric c as tree induced leakage of hco super 3 from the forest ecosystem to rivers and streams in addition to the finite sink of c in forest biomass the findings also suggest a major role for vascular plants as they invaded upland portions of the continents between 410 and 360 my ago in accelerating weathering and thereby lowering atmospheric co 2

a comparison of satellite laser ranging and seismicity data in the aegean region in this study we compare the strain rates obtained from earthquake moment tensors in the time interval 1911 92 in greece with measured velocities of slr stations relative to eurasia we find that the slr measurements do not require strain different in orientation from that seen in the earthquakes but simply more of it the clearest deficit is in the se aegean where earthquakes this century can account for virtually none of the measured slr strain rates by contrast in the northern aegean and nw turkey the earthquakes can account for a substantial part 50 of the measured strain rates by using both geodetic and seismic data to localize apparent deficits in seismically released strain this study represents a first step towards using space based geodesy for crude regional seismic risk assessment

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

anisotropic elastic full waveform inversion of walkaway vertical seismic profiling data from the arabian gulf abstract borehole seismic addresses the need for high resolution images and elastic parameters of the subsurface full waveform inversion of vertical seismic profile data is a promising technology with the potential to recover quantitative information about elastic properties of the medium full waveform inversion has the capability to process the entire wavefield and to address the wave propagation effects contained in the borehole data multi component measurements anisotropic effects compressional and shear waves and transmitted converted and reflected waves and multiples full waveform inversion therefore has the potential to provide a more accurate result compared with conventional processing methods we present a feasibility study with results of the application of high frequency up to 60 hz anisotropic elastic full waveform inversion to a walkaway vertical seismic profile data from the arabian gulf full waveform inversion has reproduced the majority of the wave events and recovered a geologically plausible layered model with physically meaningful values of the medium

fault plane solutions of microearthquakes and small events in the hellenic arc abstract the hellenic arc is the most active seismic region of the transition zone between the african and eurasian plates in this rapidly deforming region the physical state of the crust and upper mantle may vary laterally and vertically however a detailed 3d model of the region is lacking the reliable determination of fault plane solutions is crucial if such a model is to be produced on this basis fault plane solutions have been determined from recent microearthquakes and small events to assess their reliability for use in tectonic interpretation a search algorithm on first motion data and amplitude ratios and also a waveform matching scheme were employed on data from our temporal network operated on the western part of the island of crete there a network of 47 three component digital stations with an aperture of 60 km and an average station spacing of 5 km was operated in 1997 the majority of the shallow microearthquakes under crete for which fault plane solutions were determined have a near horizontal t axis oriented essentially e w differences between well determined fault plane solutions from the search algorithm and the waveform matching technique were significant strike up to 45 dip up to 10 and slip up to 50 second data of small events within the hellenic subduction zone were obtained from recently installed broadband stations at local and regional distances and inverted for a deviatoric seismic moment tensor available solutions from other sources such as the harvard group emsc or sed show drastic differences in part owing to still limited azimuthal station coverage the resulting fault plane solutions of small events have generally not been well constrained the observed large variation of fault plane solutions for micoearthquakes and small events poses a caveat to tectonic interpretation in case of using data from a few stations only

new constraints on the rapid crustal motion of the aegean region recent results inferred from gps measurements 1993 1998 across the west hellenic arc greece abstract in this paper we present the most recent observations of crustal motion across the entire west hellenic arc wha these are based on repeated gps measurements carried out in the period from 1993 to 1998 the results are presented in terms of trajectories and rates relative to eurasia within these five years southwestern greece has moved to the southwest by an average rate of 30 mm a increasing from 10 mm a at the island of lefkada in the center of the ionian islands to nearly 40 mm a along the southwest part of the peloponnesus and to 35 mm a on the islands of crete and gavdhos the data provide strong evidence that distributed shear strain starts at the kephalonia fault zone kfz were an anomalously high earthquake activity is also observed a striking interruption of the motion is seen at the island of strofades at the southwest leading edge of the wha where a south oriented displacement of 12 cm was detected coincident with the m 6 4 strofades earthquake of nov 18 1997

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

continental collision gravity spreading and kinematics of aegea and anatolia we have carried out experiments using a layered medium of sand and silicone to investigate the lateral extrusion of a material which spreads over its own weight while being compressed by the advance of a rigid indenter boundary conditions in the box mimic those prevailing in the anatolian aegean system both shortening in front of the rigid piston which models the northward motion of arabia and extension resulting from the gravity spreading of the sand silicone layer are necessary to initiate the lateral extrusion strike slip faults accommodate the lateral escape and link the normal faults accompanying gravity spreading with the thrust faults in front of the rigid indenter strike slip faults begin to accommodate extrusion at a late stage in the experiments after the normal and thrust faults have developed experiments also show that the initial geometry of the boundary of the spreading layer may result in the formation of two arcs behind which material extends in a manner analogous to the hellenic and cypriot arcs without invoking a rheological change at the junction of the two arcs the experiments also suggest that southward motion of the eastern part of the spreading region is compensated by the northward advance of the piston which is a possible explanation for the slower movement of the cypriot arc compared to the aegean arc

the mediterranean ridge a mass balance across the fastest growing accretionary complex on earth depth migration of seismic reflection profiles across the mediterranean ridge accretionary complex between the african and eurasian blocks illustrates profound variations in the geometry and internal structure along strike structural interpretations of four cross sections together with bathymetric and acoustic surface information and drilling data are used to volumetrically balance the amount of subduction versus accretion with time results suggest the existence of three distinct scenarios with a jump in decollement in the west intense backthrusting in the central part between libya and crete and transcurrent tectonism in the east the onset of accretion coincides with exhumation of thrust sheets 19 ma followed by rapid sediment accretion with thick evaporite bearing incoming successions facilitating outward growth of the wedge the minimum rate of accretion 20 25 of the total sediment supply is observed in the central portion where the ridge suffers maximum deformation here the indenting leading edge of the african plate apparently forces the sediment into subduction or local underplating in contrast an estimated 40 60 of the available sedimentary input was accreted in the western domain where collision is less accentuated the results support the hypothesis that highly destructive forearc collisional events like slab break off and exhumation of thrust sheets can be followed by periods of accretion and continuous growth of accretionary wedges

an integrated global model of present day plate motions and plate boundary deformation summary in this paper we present a global model gsrm 1 of both horizontal velocities on the earth s surface and horizontal strain rates for almost all deforming plate boundary zones a model strain rate field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field in our model we perform a least squares fit between model velocities and observed geodetic velocities as well as between model strain rates and observed geological strain rates model velocities and strain rates are interpolated over a spherical earth using bi cubic bessel splines we include 3000 geodetic velocities from 50 different mostly published studies geological strain rates are obtained for central asia only and they are inferred from quaternary fault slip rates for all areas where no geological information is included a priori constraints are placed on the style and direction but not magnitude of the model strain rate field these constraints are taken from a seismic strain rate field inferred from normalized focal mechanisms of shallow earthquakes we present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones generally the strain rate tensor field is consistent with geological and seismological data with the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs we find that in general there is a good agreement between the present day plate motions we obtain and longterm plate motions but a few significant differences exist the rotation rates for the indian arabian and nubian plates relative to eurasia are 30 13 and 50 per cent slower than the nuvel1a estimate respectively and the rotation rate for the nazca plate relative to south america is 17 per cent slower on the other hand caribbean north america motion is 76 per cent faster than the nuvel 1a estimate while crustal blocks in the india eurasia collision zone move significantly and self consistently with respect to bounding plates only a very small motion is predicted between the nubian and somalian plates by integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in for instance redefining a no net rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation

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

the gps strain rate field in the aegean sea and western anatolia the gps velocity field of the aegean sea and western anatolia is used to determine crustal deformation strain rates for the period 1988 to 1996 the zone from the marmara sea to the north aegean trough is associated with strong right lateral shear motion with maximum strain rates of 170 nstrain a in the northern aegean sea the extensional deviatoric axes are oriented nne ssw associated with strain rates reaching 150 nstrain a and in western anatolia varying around n s with rates of up to 95 nstrain a the extensional areas mostly coincide with active graben features the south western aegean sea is almost strain free in general the areas of high geodetic strain rates are accompanied by distinct seismic clusters whereas the strain free regions are nearly aseismic

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

the structure and evolution of the western mediterranean ridge the mediterranean ridge is a unique accretionary complex consisting of five key elements the frontal slope the upper slope the crest of the ridge the cleft area and the inner plateau the imerse data show that these correspond roughly to the locus of frontal accretion of underplating of a pre messinian wedge of complex faulting and possible strike slip tectonics and of a backstop of hellenic nappes covered by a messinian forearc basin the frontal portion of the complex is a post messinian accretionary wedge composed of messinian evaporites and overlying tightly folded plio quaternary sediments underlain by pre messinian sequences attached to the african plate the basal detachment at the front of the wedge occurs at the base of the evaporites moving further to the northeast the upper slope the basal detachment cuts to deeper levels leading to the development of duplex structures where pre messinian units are subcreted beneath the messinian evaporites just behind the subcreted units the evaporites thin and may be absent on the crest of the ridge this region we interpret as the site of a pre messinian accretionary wedge we suggest that following the deposition of thick evaporites in the messinian the pre messinian accretionary tectonics continued as subsurface accretion subcretion beneath the evaporites although the crest of the ridge is largely devoid of evaporites local deep evaporite basins observed here formed as local closed basins on top of the pre messinian wedge we infer that the messinian sealevel was at about the level of the ridge crest that is 3000 m below present allowing for isostatic adjustment to the removal of the water load this would imply a sealevel drop of at least 2000 m the cleft basins mark the northeast limit of the accretionary complex thick evaporite deposits to the northeast beneath the inner plateau may have been deposited in a messinian forearc basin the evaporites of the inner plateau are underlain by a thin pre messinian sequence and by crystalline basement of the hellenic nappes this basement forms the backstop to the accretionary complex

predicting natural base flow stream water chemistry in the western united states 1 robust predictions of stream solute concentrations expected under natural reference conditions would help establish more realistic water quality standards and improve stream ecological assessments models predicting solute concentrations from environmental factors would also help identify the relative importance of different factors that influence water chemistry although data are available describing the major factors controlling water chemistry i e geology climate atmospheric deposition soils vegetation topography geologic maps do not adequately convey how rocks vary in their chemical and physical properties we addressed this issue by associating rock chemical and physical properties with geological map units to produce continuous maps of percentages of cao mgo s uniaxial compressive strength and hydraulic conductivity for western united states lithologies we used catchment summaries of these geologic properties and other environmental factors to develop multiple linear regression lr and random forest rf models to predict base flow electrical conductivity ec acid neutralization capacity anc ca mg and so4 models were derived from observations at 1414 reference quality streams rf models were superior to lr models explaining 71 of the variance in ec 61 in anc 92 in ca 58 in mg and 74 in so4 when assessed with independent observations the root mean square error for predictions on validation sites were all temperature precipitation soil atmospheric deposition vegetation amount of rock water contact topography

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

a subducting seamount beneath the mediterranean ridge abstract two transverse morphological tracks across the front of the mediterranean ridge were swath mapped with a hydrosweep instrument system along the tracks ridges and troughs at the front of the accretionary prism are disrupted and bent in the direction of relative plate convergence the longer of the two tracks extends to bannock basin a brine filled depression with a closed outer moat around a central mound seismic reflection data and a gravity anomaly show a buried circular seamout beneath bannock basin whose summit is the mound this indicates an origin of the larger transverse track and bannock basin from a subducting seamount beneath bannock basin the seamount has displaced about 340 km 3 of the messinian section and yet the seafloor has not been uplifted therefore considerable evaporitic material is inferred to have been displaced by the seamount and bannock basin is a likely vent for large quantities of dissolved materials from the disrupted messinian evaporitic sequence

spatio temporal microseismicity clustering in the cretan region abstract spatio temporal clustering of microseismicity in the central forearc of the hellenic subduction zone in the area of crete is investigated data for this study were gathered by temporary short period networks which were installed on the islands of crete and gavdos between 1996 and 2004 the similarity of waveforms is quantified systematically to identify clusters of microseismicity waveform similarities are calculated using an adaptive time window containing both the p and s wave onsets the cluster detection is performed by applying a single linkage approach clusters are found in the interplate seismicity as well as in the intraplate seismicity of the continental crust in the region of the transtensional ptolemy structure the majority of the clusters are off the southern coast of crete in a region of elevated intraplate microseismic activity within the aegean plate clusters in the gavdos region are located at depths compatible with the plate interface while cluster activity in the region of the ptolemy trench is distributed along a nearly vertical structure throughout the crust extending down to the plate interface most clusters show swarm like behaviour with seismic activity confined to only a few hours or days without a dominant earthquake and with a power law distribution of the interevent times for the largest cluster precise relocations of the events using travel time differences of p and s waves derived from waveform cross correlations reveal migration of the hypocenters this cluster is located in the region of the ptolemy trench and migration occurs along the strike of the trench at 500 m day relocated hypocenters as well as subtle differences in the waveforms suggest an offset between the hypocenters and thus the activation of distinct patches on the rupture surface the observed microseismicity patterns may be related to fluids being transported along the plate interface and escaping towards the surface in zones of crustal weakness ptolemy structure triggering swarm like cluster activity along its way

on the consistency of earthquake moment release and space geodetic strain rates europe in this paper approximately 100 vlbi slr gps velocities map european strain rates from 9 0 10 8 yr 1 with regional uncertainties of 20 to 40 per cent kostrov s formula translates these strain rate values into regional geodetic moment rates m geodetic two other moment rates m seismic extracted from a 100 year historical catalogue and m plate taken from plate tectonic models contrast the geodetic rates in mediterranean europe the ratios of m seismic to m geodetic are between 0 50 and 0 71 in turkey the ratio falls to 0 22 although aseismic deformation may contribute to the earthquake deficit m seismic values less than m geodetic the evidence is not compelling because the magnitudes of the observed shortfalls coincide with the random variations expected in a 100 year catalogue if the lack of aseismic deformation inferred from the 100 year catalogue holds true for longer periods then much of europe s strain budget would have to be accommodated by more frequent or larger earthquakes than have been experienced this century to raise the ratios of m seismic to m geodetic to unity improved geological fault data bases longer historical earthquake catalogues and densification of the continent s space geodetic network will clarify the roles of aseismic deformation versus statistical quiescence

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

a geodynamic framework for eastern mediterranean kinematics we use a finite element model incorporating plate motion boundary conditions fault constraints and space geodetic velocities to calculate eastern mediterranean plate kinematics and to estimate the motion of the region s major faults we then use subsets of these constraints to generate models testing different scenarios of driving forces slab roll back at the hellenic arc arabian plate push gravitational collapse of w anatolia to match the expected pattern of deformation we find that models combining only trench rollback and arabian push are unable to provide a good match to the observed deformation across western anatolia and the aegean and that we need to introduce the effects of mantle corner flow and gravitational collapse to fit observations

the role of gravitational potential energy in active deformation in the southwestern united states in orogenic belts intrinsic buoyancy and extrinsic boundary forces act on the continental lithosphere determining the relative importance of these forces is fundamental to understanding the dynamics of continental deformation in the western united states estimates of gravitational potential energy show that given available constraints on rheology buoyancy forces are sufficient to produce the wide variety of rates and styles of observed deformation including absence of deformation this underscores the importance of gravitational potential energy for deformation in orogenic belts

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

geodetic determination of tectonic deformation in central greece from 1900 to 1988 the global positioning system has been used to measure the relative displacements of fifteen monuments in a hundred year old triangulation network spanning part of the aegean extensional basin these displacements reflect the tectonic deformation of the region over the past century showing more than one metre of north south extension across the network the crust in this region appears to contain a few slowly deforming blocks separated by more rapidly deforming zones

spatial transition from compression to extension in the western mediterranean ridge accretionary complex the mediterranean ridge has been described since 1982 as an accretionary prism related to the hellenic subduction zone however little attention has been paid to the actual mechanical boundary between the sedimentary wedge and the crustal backstop of the outer hellenic arc using seismic velocity structures from recent esp s pasiphae cruise we propose a new interpretation of existing geological and geophysical data around the western hellenic trenches the velocity structure of the inner unit of the mediterranean ridge suggests that the late neogene to quaternary sequences were deposited above a high velocity rigid body we propose to correlate the boundary of this rigid body backstop of the accretionary wedge with a series of oblique reflectors dipping to the southwest near dsdp sites 126 and 377 the backstop extends further south than previously thought and decreases by one third the total width of the compressional wedge it has thus major implications on the volume of accreted material the short wavelength folding of plio quaternary sediments observed on the outer wall of the south matapan trench is probably a consequence of gravity gliding layers above the high velocity body gently dipping 2 to the northeast using the messinian evaporite as a decollement on the other hand the hellenic trenches appear to be narrow half grabens affected by the widespread extensional deformation active on the outer hellenic arc they are situated on the landward boundary of a wider and poorly sedimented fore arc basin we conclude that extensional deformation extends at least over the width of the hellenic trenches on the continental side of the backstop whereas compressional deformation stops near the edge of the backstop itself 100 km to the southwest

the crust of the western mediterranean ridge from deep seismic data and gravity modelling summary we present a crustal cross section of the western mediterranean ridge from the african margin to the aegean sea constrained by the morphology of the ridge new seismic reflection and refraction results obtained during a two ship cruise performed in december 1988 pasiphae cruise the distribution of seismicity and gravity modelling morphologically the western mediterranean ridge can be divided into three main units from the sirte abyssal plain to the hellenic trench a broad outer unit a narrow central unit and an inner unit the seismic front orgeaward extent of the interplate seismicity between the african lithosphere and the cretan arc is located 50 km seaward of the hellenic trench seismicity is thus distributed widely over the innermost unit of the ridge suggesting that brittle material is present at shallow depth beneath the inner portion of the mediterranean ridge the refraction results of the pasiphae cruise show that the crust in the ionian basin and beneath the outer and central units of the western mediterranean ridge is oceanic and that the moho discontinuity progressively deepens towards the hellenic arc in agreement with the accretionary prism model high velocity material occurs at shallow depth beneath the innermost unit of the ridge gravity modelling also indicates a significant increase in density beneath the inner unit we consequently interpret the inner unit of the ridge as the backstop of the western mediterranean ridge prism possibly composed of peloponnesus thrust sheets

tectonics of the hellenic trench a synthesis of sea beam and submersible observations abstract detailed bathymetric investigations were performed in four zones of the hellenic trench system in 1978 using the multi narrow beam echo sounder sea beam on r v jean charcot in 1979 a field study using the 3000 m submersible cyana was conducted in three of the four sites covered by sea beam we summarize here the principal tectonic results of these studies and publish the corresponding sea beam maps it is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall in addition there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the mediterranean ridge we suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall we show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m y ago

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

the mediterranean ridge backstop and the hellenic nappes the core of the mediterranean ridge backstop consists of a pile of hellenic nappes that migrated outward from the aegean continent within the adjacent mediterranean basins during late middle miocene about 15 ma and the present mediterranean ridge has developed since that time by accretion of a new wedge the arguments we use are 1 a similarity in thickness seismic velocity and structure between the backstop and the hellenic nappes in southern peloponnesus 2 the geometry of the westward limit of the backstop that is the one expected from the amount of relative displacement of the nappes on land 3 an agreement between the estimated ages of the present accretionary wedge and the period of activity of two major faults connecting the backstop to the adjacent aegean continent the seaward limit of the backstop is situated about 170 km southwest of western crete where the displacement of the nappes is maximal and it is close to the margin near the ionian islands where their displacement is small we assume that the hellenic subduction zone migrated southwestward relative to eurasia during middle miocene and that the corresponding gravity collapse of the aegean continent was maximum at this time because the westward extrusion of anatolia had not yet started

microearthquake seismicity and fault plane solutions in the southern aegean and its geodynamic implications summary seismicity mi 3 5 in the southern aegean located using data collected during seven weeks of recording by a temporary network of seismological stations largely follows the hellenic arc the sea of crete is nearly aseismic and only little activity is located south of the hellenic trench within the african plate focal mechanisms exhibit reverse faulting in the external part of the arc and normal faulting inside it this normal faulting indicates n s extension in the northern aegean the gulf of corinth the cyclades and dodecanese islands but nw se extension in southern peloponnese and western crete and e w extension in eastern crete this non uniform strain pattern suggests that the aegean region not only extends in a n s sense with the hellenic arc moving south westward relative to the eurasian plate but also by e w extension of its southern margin so that there is a net divergence of material

earthquake mechanisms in the hellenic trench near crete summary in the hellenic trench south of crete convergence between the southern aegean sea and africa occurs at a rate of at least 60 mm yr 1 previously published first motion fault plane solutions show a variety of different fault orientations and types but are not well constrained furthermore the lack of reliable focal depths for these earthquakes has obscured any simple pattern of deformation that might exist nonetheless the mechanisms of these earthquakes have strongly influenced views of the tectonics in the hellenic trench we have improved estimates of the fault parameters and focal depths for 14 of these earthquakes using long period p and sh waveforms the earthquake mechanisms fall into four groups a normal faults with a n s strike in the over riding material above the subduction zone b low angle thrusts with an e w strike at a depth of about 40 km c high angle reverse faults with the same strike but shallower focal depths than b d events within the suducting lithosphere with approximately e w p axes the thrusting in groups b and c is probably the mechanism by which the sediments of the mediterranean sea underplate and uplift crete these events have slip vectors in the direction 025 12 which represents the convergence direction between crete and africa along the sw facing boundary of the hellenic trench one of the events in group d occurred beneath the mediterranean ridge and involved high angle reverse faulting with a wnw ese p axis almost perpendicular to the direction of shortening deduced from folds at the surface the mediterranean sea floor in this region appears to be in a state of e w compression for reasons that are not clear

interseismic strain accumulation in the marmara sea region the marmara sea region is deforming along the branches of the north anatolian fault naf which is the boundary between the anatolian and the eurasian plates we evaluate global positioning system gps measurements performed from 1992 to 1999 up to the 17 august 1999 izmit earthquake to quantify the interseismic strain accumulation pattern in the marmara sea region we compute interseismic velocities in a frame fixed to the eurasian plate at 136 gps points to compute the frame independent strain rates we first smooth the north south and the east west velocity components separately to obtain the values at grid nodes and then we compute directional derivatives and strain rates shear strain rates reveal that the marmara sea region is within the plate boundary deformation zone having a width of about 110 km the largest shear strain rate accumulation is along the northern branch of the naf with maximum shear strain rate reaching 220 nstrain yr in the marmara sea we calculate clockwise rigid body rotation rates with a maximum of 10 deg m y along the northern branch while the anatolian plate rotates anticlockwise dilatation rates display adjacent local tensional and compressional areas in the east west direction within the marmara sea assuming the uniform simple shear we compute the naf slip rates vary between 11 and 26 mm yr with a minimum around izmit and increase east and west of izmit manuscript received 30 august 2000

active deformation in eastern indonesia and the philippines from gps and seismicity data in this study we combine global positioning system gps velocities with information on the style of regional seismicity to obtain a self consistent model velocity and strain rate field for the entire eastern indonesia and philippines region in the process of interpolating 93 previously published gps velocities the style and direction of the seismic strain rate field inferred from earthquakes with m0 1 1020 n m from the harvard centroid moment tensor catalog are used as constraints on the style and direction of model strain rates within the plate boundary zones the style and direction of the seismic strain rate field are found to be self similar for earthquakes up to m0 1 1020 n m equivalent to mw 7 3 our inversion result shows the following the java trench which lacks any significant historic seismicity delineates the australian plate au sunda block sunda plate boundary west of the island of sumba east of sumba convergence is distributed over the back arc and banda sea and there is no subduction at the timor trough suggesting that the northern boundary of the au plate runs north of this part of the banda arc through the banda sea in new guinea most motion is taken up as strike slip deformation in the northern part of the island delineating the pacific plate pa au boundary however some trench normal convergence is occurring at the new guinea trench evidence that the strain is partitioned in order to accommodate oblique pa au motion pa au motion is consistent with nuvel 1a direction but 8 mm yr 1 slower than the nuvel 1a estimate for pa au motion the sulawesi trench and molucca sea delineate zones of high strain rates consistent with high levels of active seismicity the sulawesi trench may take up some of the au sunda motion philippine sea plate motion is in a direction slightly northward of the nuvel ia estimate and is partitioned in some strike slip strain rates along the philippine fault and relatively larger trench normal convergence along the philippine trench and on the philippine mainland in the southern philippines and along the manila trench in the northern philippine islands the high level of strain rate along the manila trench is not released by any significant historic seismic activity for the entire eastern indonesia philippines region seismicity since 1963 has taken up 40 of the total moment rate inferred from our model

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

geodetic strain of greece in the interval 1892 1992 a first order triangulation of greece was carried out in the 1890s reoccupation using global positioning system receivers of 46 of the 93 original markers yielded estimates of the deformation of the region over the intervening interval broad regions have similar geodetic strain over the 100 year time span strain north of the gulf of korinthos is predominantly north south extension though with a significant east west component the central peloponnisos is relatively stable whereas the gulfs of the southern peloponnisos are all characterized by uniaxial east west extension the seismic expression of strain for the entire region calculated from the seismic moment tensors of earthquakes of m s 5 8 during the past 100 years accounts for only 20 50 of the geodetically determined strain at a scale of 50 100 km the fraction of the strain that is expressed seismically varies much more than this range in particular whereas seismic strain in the eastern gulf of korinthos over the past 100 years is commensurate with the geodetic strain there is rapid extension across the western gulf of korinthos 0 3 strain yr 1 with negligible seismic strain for the 100 year period prior to 1992 the egion earthquake of june 1995 in the western gulf of korinthos released only a small proportion 20 of the elastic strain that had accumulated in that region the observed distribution of displacements can be explained by the relative rotation of two plates with a broad accommodation zone between them but it is equally consistent with the deformation that would be expected of a sheet of fluid moving toward a low pressure boundary at the hellenic trench a simple calculation implies that if the region does behave as a fluid then its effective viscosity is 10 22 10 23 pa s such viscosities are consistent with the deformation of a lithosphere obeying a rheological law similar to that obtained for olivine in the laboratory

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

the dissolution kinetics of major sedimentary carbonate minerals abstract among the most important set of chemical reactions occurring under near earth surface conditions are those involved in the dissolution of sedimentary carbonate minerals these minerals comprise about 20 of phanerozoic sedimentary rocks calcite and to a significantly lesser extent dolomite are the major carbonate minerals in sedimentary rocks in modern sediments aragonite and high magnesian calcites dominate in shallow water environments however calcite is by far the most abundant carbonate mineral in deep sea sediments an understanding of the factors that control their dissolution rates is important for modeling of geochemical cycles and the impact of fossil fuel co 2 on climate diagenesis of sediments and sedimentary rocks it also has practical application for areas such as the behavior of carbonates in petroleum and natural gas reservoirs and the preservation of buildings and monuments constructed from limestone and marble in this paper we summarize important findings from the hundreds of papers constituting the large literature on this topic that has steadily evolved over the last half century our primary focus is the chemical kinetics controlling the rates of reaction between sedimentary carbonate minerals and solutions we will not attempt to address the many applications of these results to such topics as mass transport of carbonate components in the subsurface or the accumulation of calcium carbonate in deep sea sediments such complex topics are clearly worthy of review papers on their own merits calcite has been by far the most studied mineral over a wide range of conditions and solution compositions in recent years there has been a substantial shift in emphasis from measuring changes in solution composition to determine batch reaction rates to the direct observation of processes occurring on mineral surfaces using techniques such as atomic force microscopy afm however there remain major challenges in integrating these two very different approaches a general theory of surface dissolution mechanisms currently lacking although see lasaga and luttge science 291 2001 2400 is required to satisfactorily relate observations of mineral surfaces and the concentration of dissolved components studies of aragonite high magnesian calcites magnesite and dolomite dissolution kinetics are much more limited in number and scope than those for calcite and provide at best a rather rudimentary understanding of how these minerals are likely to behave in natural systems although the influences of a limited number of reaction inhibitors have been studied probably the greatest weakness in application of experimental results to natural systems is understanding the often profound influences of foreign ions and organic matter on the near equilibrium dissolution kinetics of carbonate minerals

estimates of seismic potential in the marmara sea region from block models of secular deformation constrained by global positioning system measurements we model the geodetically observed secular velocity field in north western turkey with a block model that accounts for recoverable elastic strain ac cumulation the block model allows us to estimate internally consistent fault slip rates and locking depths the northern strand of the north anatolian fault zone nafz carries approximately four times as much right lateral motion 24 mm yr as does the southern strand in the marmara sea region the data show strain accu mulation to be highly localized we find that a straight fault geometry with a shallow locking depth of 6 7 km fits the observed global positioning system velocities better than does a stepped fault geometry that follows the northern and eastern edges of the sea this shallow locking depth suggests that the moment release associated with an earthquake on these faults should be smaller by a factor of 2 3 than previously inferred assuming a locking depth of 15 km online material an updated version of velocity field data

diffraction tomography and multisource holography applied to seismic imaging seismic tomography is emerging as an imaging method for determining subsurface structure when the view angle coverage is limited and the scale of the medium inhomogeneities is comparable with the wavelength as is often true in geophysical applications the performance of ordinary ray tomography becomes poor other tomographic methods are needed to improve the imaging process here we study diffraction tomography and multisource holography and evaluate their performances for surface reflection profiling srp vertical seismic profiling vsp and cross hole measurements theoretical formulations are derived for two dimensional geometry in terms of line sources along a source line and line receivers along a receiver line the theory for diffraction tomography is based on the born or rytov approximation the performances of diffraction tomography and multisource holography are evaluated by examining the information coverage in the spatial frequency domain and by numerical examples multisource holography

near channel versus watershed controls on sediment rating curves predicting riverine suspended sediment flux is a fundamental problem in geomorphology with important implications for water quality land and water resource management and aquatic ecosystem health to advance understanding we evaluated environmental and landscape factors that influence sediment rating curves srcs we generated srcs with recent total suspended solids tsss and discharge data from 45 gages on 36 rivers throughout the state of minnesota usa watersheds range from 32 to 14 600 km2 and represent distinct settings regarding topography land cover and geologic history rivers exhibited three distinct src shapes simple power functions threshold power functions and peaked or negative slope functions we computed src exponents and coefficients describing the steepness of the relation and the tss concentration at median flows respectively in addition to quantifying watershed topography climate hydrology geology soil type and land cover we used lidar topography to characterize the near channel environment upstream of gages we used random forest models to analyze relations between src parameters and attributes of the watershed and the near channel environment the models correctly classify 78 of src shapes and explain 37 60 of variance in src parameters we find that src steepness exponent is strongly related to near channel morphological characteristics including near channel relief channel gradient and presence of lakes along the local channel network but not to land use in contrast land use influences tss concentrations at moderate and low flow these findings suggest that the near channel environment controls changes in tss as flows increase whereas land use drives median and low flow tss conditions

strain probe best fitting a homogeneous strain to the motions of scattered points abstract in laboratory experiments or e g in studies of glacier motion one sometime wants to estimate a finite strain from images or surveys of scattered marker points taken at successive times similarly crustal geodetic strain can be estimated by measuring velocities of geodetic stations the strain probe presented here is a simple formula that calculates a best fit strain from the motions of n marker points distributed over an area or a volume and monitored in a cartesian reference frame specifically it is the product of two 2 2 or 3 3 in 3 d symmetric matrices whose components are populated from the known positions and the measured displacements of the markers two examples implemented in excel workbooks illustrate how to combine the strain probe with the processing of the data and of its results speck motions in a means urai see through experiment are an example of a finite strain calculation published geodetic site velocities 120 stations in central anatolia are an example of infinitesimal strain

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