lithospheric structure in central eurasia derived from elevation geoid anomaly and thermal analysis we present new crustal and lithospheric thickness maps for central eurasia from the combination of elevation and geoid anomaly data and thermal analysis the results are strongly constrained by numerous previous data based on seismological and seismic experiments tomographic imaging and integrated geophysical studies our results indicate that high topography regions are associated with crustal thickening that is at a maximum below the zagros himalaya tien shan and the tibetan plateau the stiffer continental blocks that remain undeformed within the continental collision areas are characterized by a slightly thickened crust and flat topography lithospheric thickness and crustal thickness show different patterns that highlight an important strain partitioning within the lithosphere the arabia eurasia collision zone is characterized by a thick lithosphere underneath the zagros belt whereas a thin to non existent lithospheric mantle is observed beneath the iranian and anatolian plateaus conversely the india eurasia collision zone is characterized by a very thick lithosphere below its southern part as a consequence of the underplating of the cold and stiff indian lithosphere our new model presents great improvements compared to previous global models available for the region and allows us to discuss major aspects related to the lithospheric structure and acting geodynamic processes in central eurasia

40ar 39ar dating of quaternary lavas in northwest iran constraints on the landscape evolution and incision rates of the turkish iranian plateau summary we report five new 40 ar 39 ar ages for basaltic lavas in the maku region of northwest iran between ca 1 87 and 0 40 ma which help constrain the tectonic and landscape evolution of this part of the turkish iranian plateau flows originated from the composite volcanoes ararat agridagi tend urekandyigitdagi ineasternturkey anatolia thesevolcanoesarewithin the turkish iranian plateau which is a consequence of the arabia eurasia collision but has a poorly constrained evolution and surface uplift history current plateau elevations are typically 1 5 2 km and relief between non volcanic summits and basins is typically on the scale of 1 km samples are from flows that passed along pre existing river valleys gorges were cut by re established rivers after the eruptions but the great majority of the local relief 95 per cent lies above the sampled flows and so most likely pre dates the volcanism gorge depths and lava ages allow local quaternary fluvial incision rates to be calculated which are 0 01 to 0 05 mm yr 1 these rates imply slow surface uplift of this part of the turkish iranian plateau during the quaternary we therefore constrain the generation of the great majority of relief in the study area to be pre quaternary and caused by the tectonic construction of the plateau rather than a subcrustal origin related to the quaternary magmatism

lithospheric structure beneath the south eastern zagros mountains iran recent slab break off integrated lithospheric modelling based on the combined interpretation of gravity geoid and topography data sets highlights a previously undocumented lithospheric thinning beneath the zagros collisional belt iran which we propose to relate to recent slab break off at the continent ocean transitional lithosphere recent published data on the distribution of seismicity at depth support this interpretation in agreement with other published models for the zagros mountains the overlying crust exhibits by contrast a noticeable thickening reaching a maximum of 52 km the consequent thermal uplift expected from slab break off is suggested to have modified the zagros wedge taper and triggered the recently documented switch from thin skinned to thick skinned deformation in the zagros fold thrust belt

deep crustal structure and flexure of the arabian plate beneath the zagros collisional mountain belt as inferred from gravity observations the zagros mountain belt region a neogene continental collisional zone between arabia and iran that is characterized by a suture a folded belt and a foreland basin is unusual among active mountain belts in that its 6 12 km thick sedimentary cover is shortening predominantly by folding while the basement is apparently thickening along numerous high angle reverse faults we have used over 9000 gravity measurements in the region in conjunction with limited seismological observations and geological cross sections of the uppermost 10 km of crust to infer the deeper crustal structure beneath the region crustal models constrained by the bouguer anomalies and other seismological and geological data are characterized by a moho that dips about 1 to the northeast beneath the folded belt and increases in dip to about 5 near the main zagros thrust mzt the moho depth increases from 40 km beneath the leading edge of the foreland basin the mesopotamian foredeep and persian gulf to as much as 65 km beneath the mzt alternative models that incorporate a subducted oceanic crust that is attached to the underthrusting arabian crust deviate little in their moho configurations from the above simpler models negative isostatic residual anomalies are interpreted to indicate local overcompensation beneath the foreland basin and near the folded belt and beneath the mzt we show that underthrust sedimentary rocks of the converging margins along the suture zone may account for the negative isostatic residual anomalies near the mzt however to explain the rest of the isostatic anomalies requires other forces to be acting on this collisional plate boundary for example elastic flexure models required a combination of topography and subsurface loads or downward force the origin of which is not clear to approximate the bouguer or isostatic residual anomalies associated with the foreland basin and the folded belt the topography load of the zagros mountain belt is insufficient to cause the required deflection of the underthrusting arabian plate a combination of isostatic elastic flexure and horizontal compression forces acting on the edge of the arabian craton and the transitional lithosphere of central iran appears to best model the crust of the zagros region we propose a model in which the lower crust of the converging arabian plate located beneath the zagros is being shortened and thickened plastically between the seismogenic rigid upper crust and a rigid uppermost mantle lid the mantle lid probably decoupled from the lowermost crust un der thrusts the iranian crustal blocks thus confined from below the horizontally compressed plastic lower crust hydraulically depresses the moho and raises the faulted and folded brittle upper crust in isostatic equilibrium

seismology of the 2017 hojedk earthquakes mn 6 0 6 1 kerman province se iran abstract three moderate earthquakes on 1 and 12 december 2017 with mn magnitudes of 6 0 6 1 ms1 ms2 and ms3 occurred in the se iran they happened in the area between nayband and kuh banan fault systems ne of the kerman metropolice we combined satellite imagery seismicity focal mechanism solutions strong motions and coulomb stress to investigate the earthquakes these events were located near the southeastern splay of the n s lakar kuh right lateral strike slip fault active tectonics of the lakar kuh fault as well as the earthquake deformations were confirmed by satellite imagery and field photographs respectively hypocenters of the three mw 6 0 earthquakes and their aftershocks indicated a migration of faulting from the se towards the nw according to high resolution satellite imagery the third earthquake produced 6 km of coseismic surface rupture in the alluvial fan deposits east of mian kuh with maximum deformation in the middle part the focal mechanisms of both the mainshocks and the strongest aftershocks mn 4 6 determined from p wave first motions indicated nw se fault strikes for the 3 events dipping sw for ms3 with dominant reverse slip and minor strike slip components general northwestward migration of mainshocks as well as strong motions recorded at accelerometers nearby showed evidence for northwestward rupture directivity in all three earthquakes it was in accordance with the rupture geometry hypocenter and centroid depth of ms3 the coulomb stress investigation also revealed that the aftershocks of the 3 events partially covered the increasing areas of coulomb stress

the deep structure of the iranian plateau high resolution structures of the lithosphere asthenosphere system beneath a seismic profile in iran are obtained by the simultaneous inversion of data from receiver functions and fundamental mode rayleigh wave group velocity and validated by modeling bouguer gravity anomaly data the seismic data are gathered over a profile extending across zagros sanandaj sirjan zone ssz urumieh dokhtar magmatic arc udma central iran alborz binalud mountain ranges and kopeh dagh mountain ranges the results confirm the presence of crustal roots at the north and south of iranian plateau where it meets the arabian plate and eurasia the high velocity lithosphere of the arabian plate gently plunges nne ward beneath central iran supporting the subduction of the continental lithosphere responsible for the seismicity of the area the crust and lithosphere are thinner beneath central iran where two low velocity structures are very likely related to magma sources of the udma and in east of iran around lut block where the volcanism shows calcalkaline subduction related geochemistry the crustal lithospheric root to the north of the iranian plateau may represent the relict of a previous cimmeric subduction zone therefore the iranian lithosphere asthenosphere system could be the result of the coalescence of two separate subduction zones

impulsive source of the 2017 m w 7 3 ezgeleh iran earthquake on 12 november 2017 a m w 7 3 earthquake struck near the iranian town of ezgeleh at the iran iraq border this event was located within the zagros fold and thrust belt which delimits the continental collision between the arabian and eurasian plates despite a high seismic risk the seismogenic behavior of the complex network of active faults is not well documented in this area due to the long recurrence interval of large earthquakes in this study we jointly invert interferometric synthetic aperture radar and near field strong motions to infer a kinematic slip model of the rupture the incorporation of these near field observations enables a fine resolution of the kinematic rupture process it reveals an impulsive seismic source with a strong southward rupture directivity consistent with significant damage south of the epicenter we also show that the slip direction does not match plate convergence implying that some of the accumulated strain must be partitioned onto other faults

the zagros folded belt fars iran constraints from topography and critical wedge modelling summary the late miocene tectonics of the zagros folded belt fars province has for long been related solely to folding of the cover controlled by a ductile decollement between basement and the sedimentary cover however geological constraints topography analysis and seismotectonic studies reveal that basement thrusting may produce locally significant deformation in the cover to determine how the deep seated deformation in the basement may contribute to the overall topography we first examine the filtered large and short wavelengths of the topography we find that the short wavelength component of the topography 20 25 km including the zagros folds is superimposed on the differential uplift at the regional scale in other words the regional base level of folded marker horizons remains parallel to the regional topography of interest modelling reveals that the salt based wedge model alone is not able to reproduce the large wavelength component of the topography of the zagros folded belt this reveals that when a thick relatively to its overburden layer of salt forms the basal decollement it is generally too weak and cannot support the growth of significant topography we then test an alternative thick skinned crustal wedge model involving the crust of the arabian margin which is decoupled above a viscous lower crust this model satisfactorily reproduces the observed topography and is consistent with present day basement thrusting topography analyses and geological constraints we conclude that basement involved thickening and shortening is mechanically required to produce the shape of the zagros folded belt since at least 10 ma finally the involvement of the basement provides mechanical and kinematic constraints that should be accounted for cross sections balancing and further assessing the evolution of zagros at crustal or lithospheric scales

buildup of a dynamically supported orogenic plateau numerical modeling of the zagros central iran case study the iranian plateau is a vast inland region with a smooth average elevation of c 1 5 km formed at the rear of the zagros orogen as a result of the arabia eurasia collision i e over the last 30 35 myr this collision zone is of particular interest due to its disputed resemblance to the faster himalayan collision which gave birth to the tibetan plateau around 50 myr ago recent studies have suggested that a recent 10 5 ma slab break off event below central iran caused the formation of the iranian plateau here we test several hypotheses through large scale 3082 3 590 km numerical models of continental subduction mod els that incorporate a free upper surface erosion rheological stratification brittle elastic ductile rheologies and metamorphic phase changes density and physical properties and account for the specific crustal and thermal structure of the arabian and iranian continental lithospheres we test the impact of the transition from oceanic to continental subduction and the topographic consequences of the progressive slowdown of the convergence rate during continental subduction our results demonstrate the role of mantle flow beneath the overriding plate initiated as an indirect consequence of slab break off this flow creates a dynamic topography support during continental subduction and results in delamination of the overriding plate lithospheric mantle followed by isostatic readjustment hence of further uplift and maintenance of a plateau like topography without significant crustal thickening the slowdown of the convergence rate dur ing the development of the continental subduction collision phase largely contributes to this process by controlling the timing and depth of slab break off

pn velocities beneath continental collision zones the turkish iranian plateau summary tomographic imaging of the uppermost mantle velocity in the middle east shows normal pn velocities 8 0 8 2 kms beneath the black sea and the southern caspian sea in contrast low pn velocities 7 9 km s i are found beneath the aegean sea and much of the turkish iranian plateau a region of exceptionally low pn velocities c7 6 km s beneath the lesser caucasus mountains and along the turkish iranian border coincides with a region of high sn attenuation and extensive neogene volcanism all these features suggest that near solidus conditions exist within the uppermost mantle beneath the turkish iranian plateau such conditions may result either from the decompression melting associated with upwelling convection cells or by the infiltration of water released from subducted lithosphere into the mantle above the presence of a partially melted uppermost mantle weakens the lithosphere beneath the turkish iranian plateau thus allowing it to become the locus of deformation in the arabian eurasian collision zone

space time model for repeating earthquakes and analysis of recurrence intervals on the san andreas fault near parkfield california we propose a stochastic model for characteristically repeating earthquake sequences to estimate the spatiotemporal change in static stress loading rate these earthquakes recur by a cyclic mechanism where stress at a hypocenter is accumulated by tectonic forces until an earthquake occurs that releases the accumulated stress to a basal level renewal processes are frequently used to describe this repeating earthquake mechanism variations in the rate of tectonic loading due to large earthquakes and aseismic slip transients however introduce nonstationary effects into the repeating mechanism that result in nonstationary trends in interevent times particularly for smaller magnitude repeating events which have shorter interevent times these trends are also similar among repeating earthquake sites having similar hypocenters therefore we incorporate space time structure represented by cubic b spline functions into the renewal model and estimate their coefficient parameters by maximizing the integrated likelihood in a bayesian framework we apply our model to 31 repeating earthquake sequences including 824 events on the parkfield segment of the san andreas fault and estimate the spatiotemporal transition of the loading rate on this segment the result gives us details of the change in tectonic loading caused by an aseismic slip transient in 1993 the 2004 parkfield m6 earthquake and other nearby or remote seismic activities the degree of periodicity of repeating event recurrence intervals also shows spatial trends that are preserved in time even after the 2004 parkfield earthquake when time scales are normalized with respect to the estimated loading rate

tertiary sequence of deformation in a thin skinned thick skinned collision belt the zagros folded belt fars iran 1 we describe how thin skinned thick skinned deformation in the zagros folded belt interacted in time and space homogeneous fold wavelengths 15 8 5 3 km tectono sedimentary evidence for simultaneous fold growth in the past 5 5 2 5 ma drainage network organization and homogeneous peak differential stresses 40 15 mpa together point to buckling as the dominant process responsible for cover folding basin analysis reveals that basement inversion occurred 20 ma ago as the arabia eurasian plate convergence reduced and accumulation of neogene siliciclastics in foreland basin started by 10 ma ongoing contraction occurred by underplating of arabian crustal units beneath the iranian plate this process represents 75 of the total shortening it is not before 5 ma that the zagros foreland was incorporated into the southward propagating basement thrust wedge folds rejuvenated by 3 2 ma because of uplift driven by basement shortening and erosion since then folds grew at 0 3 0 6 mm yr and forced the rivers to flow axially a total shortening of 65 78 km 16 19 is estimated across the zagros this corresponds to shortening rates of 6 5 8 km ma consistent with current geodetic surveys we point out that although thin skinned deformation in the sedimentary cover may be important basement involved shortening should not be neglected as it requires far less shortening moreover for such foreland folded belts involving basement shortening underplating may be an efficient process accommodating a significant part of the plate convergence

a reappraisal of earthquake focal mechanisms and active shortening in the zagros mountains of iran summary the zagros mountains of sw iran are one of the most seismically active intra continental fold and thrust belts on earth and an important element in the active tectonics of the middle east surface faulting associated with earthquakes is extremely rare and so most information about the active faulting comes from earthquakes we use long period teleseismic p and sh body waves to determine the orientation and depth of faulting in 16 new earthquakes and then evaluate and synthesize all the available teleseismic data on earthquake source parameters in the zagros we use this information to investigate the style and distribution of active faulting in the zagros and how it contributes to the n s shortening of the arabia eurasia collision when the data are ranked in quality and carefully evaluated simple patterns are seen that are not apparent when routine catalogue data are taken at face value an important change in the fault configuration occurs along strike of the belt in the nw overall convergence is oblique to the trend of the belt and the surface anticlines and is achieved by a spatial separation partitioning of the orthogonal strike slip and shortening components on separate parallel fault systems by contrast in the se overall convergence is orthogonal to the regional strike and achieved purely by thrusting in the central zagros between these two structural regimes deformation involves parallel strike slip faults that rotate about vertical axes allowing extension along the strike of the belt the overall configuration is similar to that seen in other curved shortening belts such as the himalaya and the java sumatra trench all the zagros earthquakes we have been able to check have centroids shallower than 20 km and are confined to the upper crust many of the larger earthquakes are likely to occur in the basement beneath the sedimentary cover which is active even beneath areas of known shallow structural decollement such as the dezful embayment the dominant style of shortening is high angle reverse faulting with dips 30 though some lower angle thrusting occurs in places active thrust and reverse faulting is relatively confined to the lower topography on the sw edge of the belt today and only strike slip faulting affects the higher topography profound vertical changes in structural and stratigraphic level indicate that a similar style of deformation was once active across the width of the simple folded belt but has progressively migrated sw over the last 5 ma there is no evidence for a seismically active structural decollement such as a low angle thrust beneath the zagros nor is there any seismic evidence for active subduction either beneath the zagros or beneath central iran instead the arabian margin seems to have shortened by distributed thickening of the basement only in the syntaxis of the oman line at the se end of the zagros is there any evidence for a low angle thrust of regional extent here earthquakes continue 50 km north of the zagros thrust line the geological suture between the arabian margin and central iran reaching depths of 30 km and may represent thrusting of arabian basement beneath central iran to this extent

logarithmic model joint inversion method for coseismic and postseismic slip application to the 2017 mw 7 3 sarpol zahāb earthquake iran

estimating the mechanical anisotropy of the iranian lithosphere using the wavelet coherence method abstract we calculated anisotropic wavelet coherence between bouguer anomaly and topography in order to map the anisotropy of the effective elastic thickness of the iranian lithosphere t e an orthotropic elastic plate model is used for inverting the anisotropic wavelet coherence to compute the mechanical anisotropy through the weak axis of the t e anisotropy of the t e weak axis and the strength of the anisotropic parameter namely the anisotropic coherence effect over the study area are estimated by restricting the rotated morlet wavelet fan wavelet geometry over an azimuthal range of 90 large scale t e variations have been shown to be associated with phenomena such as mountain belts subduction zones craton boundaries fault zones and seismogenic regions although the correlation between the major tectonic features of the iranian lithosphere and the distribution of the t e weak axis is not general or precise in some regions such as the central iran blocks and the alborz kopeh dagh zagros and makran orogenic belts the weak axis has a uniform or slowly varying pattern which changes over their boundaries a perpendicular alignment between seismic anisotropy measurements in iran and the t e weak directions suggests a lithospheric origin for anisotropy the correlation between averaged stress directions and the weak axis of the t e in iran indicates that the present day stress field and the fossil strain are still related correlation between these factors suggests vertically coherent deformation of the lithosphere in iran resulting from the multiply convergent orogenic processes the complex mechanical anisotropy pattern of the iranian lithosphere results from the interaction of many pre existent structures which dominantly control the mechanical anisotropy of the lithosphere

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

lithospheric structure beneath nw iran using regional and teleseismic travel time tomography we compute a 2 d tomogram using the p wave arrival time readings from a temporary seismic experiment to study the seismic structure of the crust and upper mantle in nw iran the study area includes the western margins of the south caspian basin scb and the sahand and sabalan post collisional volcanoes in nw iran we invert 2780 regional and teleseismic relative p wave arrival times recorded by 23 stations along the seismic profile extending from the western shoreline of the caspian sea to lake urumieh our tomographic results show a higher velocity region beneath the scb the observed higher velocities strongly correlate with the observed positive gravity anomalies over the southwestern margins of the caspian sea suggesting an oceanic like nature for the scb lithosphere the tomographic results also show several lower velocity anomalies in the crust the sabalan volcano is underlain by a low velocity zone in the lower crust which is most likely thermal in nature in the sahand region the lower velocities are considerably shallower in depth and might be controlled by shallow sedimentary structures as well as an anomalously warm upper crust the shallow low velocity regions are connected with deeper low velocity zones 60 100 km deep in the upper mantle this pattern points to a possible mantle source of post collisional volcanism in nw iran i e the melting of a subducted slab

difference in the gps deformation pattern of north and central zagros iran summary measurements on either side of the kazerun fault system in the zagros mountain belt iran show that the accommodation of the convergence of the arabian and eurasian plates differs across the region in northwest zagros the deformation is partitioned as 3 6 mm yr 1 of shortening perpendicular to the axis of the mountain belt and 4 6 mm yr 1 of dextral strikeslip motion on northwest southeast trending faults no individual strike slip fault seems to slip at a rate higher than 2m m yr 1 in southeast zagros the deformation is pure shortening of 8 2m m yr 1 occurring perpendicular to the simple folded belt and restricted to the persian gulf shore the fact that most of the deformation is located in front of the simple folded belt close to the persian gulf while seismicity is more widely spread across the mountain belt confirms the decoupling of the surface sedimentary layers from the seismogenic basement a comparison with the folding and topography corroborates a southwestward propagation of the surface deformation the difference in deformation between the two regions suggests that right lateral shear cumulates on the north south trending kazerun strike slip fault system to 6 2m m yr 1

a strong seismic velocity contrast in the shallow mantle across the zagros collision zone iran summary surface wave dispersion measurements are interpreted jointly with the inversion of teleseismic p wave traveltime residuals along a dense 620 km long temporary seismic profile across the zagros to investigate its upper mantle structure the s wave model determined from rayleigh wave dispersion in the zagros fold and thrust belt has high velocities from 4 5 0 2 km s 1 below the moho to 4 9 0 25 km s 1 at 200 km depth which are comparable to a shield like structure beneath the suture region from the main zagros thrust mzt to the urumiehdokhtar volcanic arc s wave velocities are lower than beneath the zagros in the top 50 km of the upper mantle with a minimum of 4 4 0 2 km s 1 at 80 km depth from 150 km and deeper s velocities are as high as beneath the zagros we suggest that part of the velocity difference at shallow depth is due to higher mantle temperatures and or higher fluid content beneath the northern half of the profile but that velocities are too high to support the hypothesis of mantle lid delamination under the suture zone teleseismic p traveltime relative residuals display a long wavelength variation along the transect with a difference of 1 1 s between negative residuals in the zagros simple folded belt and positive residuals in central iran this difference backprojects into a 6 7 per cent lateral variation of p wave velocity in the shallow upper mantle with higher vp beneath zagros and lower vp beneath central iran the main short wavelength variation of the residual is located in the suture region with late p arrivals in the region of the mzt and early arrivals in the sanandaj sirjan zone ssz using synthetic models of vp perturbations we show that the high velocities of the arabian platform have to extend laterally at least to the ssz to fit the observed p delays this model also predicts rayleigh wave phase velocities which are within the error bars of the observed dispersion it supports the model of crustal scale overthrusting at the mzt

structural variation along the zagros and the nature of the dezful embayment structure varies along strike in the zagros fold and thrust belt of iran which is a principal element in the arabia eurasia continental collision pre collision late cretaceous ophiolite nappes kermanshah neyriz and related nappes of deep marine sediments radiolarite series were emplaced next to two regions pusht e kuh arc fars which later developed a consistent structural style across the range from the high zagros fault to the foreland limit of deformation the intervening area has a zone of highly imbricated arabian plate strata the bakhtyari culmination thrust southwest towards and over a low relief low elevation region the dezful embayment there are no ophiolite nappes northeast of the bakhtyari culmination isopachs reflect these different structural patterns from late cretaceous time but not earlier in late cretaceous time the dezful embayment recorded less deposition than adjacent areas to the northwest and southeast in the palaeogene there was little net difference between the dezful embayment and its margins the dezful embayment has been a depocentre since roughly 35 ma which is the likely time of initial collision between arabia and eurasia we propose that the syn collision structure and stratigraphy of the zagros is therefore strongly influenced by the variation in late cretaceous ophiolite emplacement but the original cause of this variation is not clear

seismological constraints on the crustal structure beneath the zagros mountain belt iran summary the zagros mountain belt of western iran results from the collision of the arabian and central iran continental blocks the stage of the collision is unclear and the crustal structure of the zagros is rather poorly known in this study we investigate the velocity structure of the crust and upper mantle beneath the ghir region located in the central zagros using data collected by a temporary local seismological network including a broad band instrument the structures of the sedimentary cover and the upper crystalline crust are estimated from the inversion of p and s traveltimes of local earthquakes recorded on a dense seismological network the upper crust consists of an 11 km thick sedimentary layer v p 4 70 km s 1 above a 8 km thick upper crystalline crust v p 5 85 km s 1 the velocity of the lower crust and the depth of the moho are found using receiver function analysis of teleseismic earthquakes the lower crystalline crust is unusually slow v p 6 5 km s 1 and 27 km thick the upper bound for the total crustal thickness beneath the ghir region is 46 2 km a comparison of the thickness of the crystalline crust of the zagros with available information for the thickness of the crystalline crust of the arabian platform shows that at present the zagros has a thinner crust the current crustal thickness beneath the zagros is comparable to the pre collision crustal thickness of the arabian platform suggesting that the zagros is now in a very early stage of continental collision

presence of a layered lithosphere beneath the zagros collision zone abstract the continental collision between the arabian and eurasian plates following the subduction of the neo tethys ocean beneath eurasia resulted in a complex deformation across the zagros mountains we used more than 700 s receiver functions obtained from 61 permanent stations to provide a detailed image of the lithospheric interaction between the eurasian and arabian plates our results suggest the existence of two different lithospheric blocks a 200 km thick lithosphere was observed beneath the zagros collision zone and most likely represents the arabian lithosphere which has been strongly deformed thickened and depleted based on our results shortening due to the collisional process is differently accommodated by the crust and mantle lithosphere of the zagros collision zone we localized the thick arabian lithosphere beneath the zagros sanandaj sirjan zone ssz and urumieh dokhtar magmatic assemblage udma whereas the crustal thickening 70 km seems to be concentrated just beneath the ssz furthermore we found a thin lithosphere of about 80 90 km that we interpret here as the iranian lithosphere beneath central iran and alborz additionally our results suggest the presence of remnants of the fossil neo tethys subduction at depths ranging between 80 and 150 km within the arabian lithosphere this dipping structure can be seen beneath the zagros ssz and udma and seems to disappear towards the northeast beneath central iran and alborz these findings may support the idea of a breakoff of the oceanic neo tethyan slab beneath central iran which results in an asthenospheric upwelling and thinning of the iranian lithosphere beneath central iran and alborz the boundary between the arabian and iranian plates seems to be located northeast of the udma in the northwest of zagros and southwest of the udma in the central zagros region

structural styles in the zagros simple folded zone iran arabia eurasia convergence is achieved in the nw zagros by a combination of shortening on nw se trending folds and thrusts mainly in the simple folded zone and by right lateral strike slip on the nw se trending main recent fault a balanced and restored cross section across this part of the range indicates c 49 km of shortening this probably occurred since c 5 ma providing an estimate of the long term shortening rate across the simple folded zone of c 10 mm a 1 the geometries of exposed structures suggest both basement thrusts and thin skinned decollement levels with major folds possibly nucleated above basement faults fold geometries indicate several decollement horizons shale units are candidates as well as evaporites in the neogene mesozoic lower palaeozoic and upper proterozoic successions the se part of the simple folded zone deforms by north south shortening on broadly east west trending folds and thrusts the link between these regions occurs via a set of fault blocks c 400 km wide in total each bounded by north south right lateral faults incremental changes in the strike of some of the folds occur across these right lateral faults with more east west orientations to the east

subduction history of the tethyan region derived from seismic tomography and tectonic reconstructions 1 in the mantle underneath the tethyan suture zone large volumes of positive velocity anomalies have been imaged by seismic tomography and interpreted as the present day signature of subducted tethyan lithosphere we investigate the mesozoic cenozoic subduction history of the region by integrating independent information from mantle tomography and tectonic reconstructions three different subduction scenarios for the tethyan oceanic lithosphere representative for the available tectonic reconstructions are used to predict the present thermally anomalous volumes associated with the lithospheric surface subducted since the late mesozoic next these predicted thermal volumes and their expected positions are compared to the relevant anomalous volumes derived from seismic tomographic images in this analysis we include among others the possible effects of ridge subduction and slab detachment after the cenozoic continental collisions absolute plate motion and slab thickening in the mantle our preferred subduction model comprises the opening of large back arc oceanic basins within the eurasian margin the model points to slab thickening by a factor of 3 in the mantle in which case the estimated volumes allow for active oceanic spreading 1 2 5 cm yr in the tethyan lithosphere during convergence our results further indicate the occurrence of early oligocene slab detachment underneath the northern zagros suture zone followed by both westward and eastward propagation of the slab tear and diachronous eocene to miocene slab detachment below the eastern to western himalayas free sinking rates of the detached material of 2 cm yr in the lower mantle provide the best fit between the tomographic mantle structure and our tethyan subduction model

multidecadal variations of the surface kuroshio between 1950s and 2000s and its impacts on surrounding waters based on the analyses of 59 year 1950 2008 surface geostrophic velocities the multidecadal changes of kuroshio from the eastern luzon to the southern japan are investigated result shows that the upstream kuroshio from the east of luzon to southern east china sea suffers much more obvious multidecadal changes except for the decade of 1980 the kuroshio east of luzon possesses a multidecadal tendency opposite to that east of taiwan besides 1980s the multidecadal change of kuroshio bordering taiwan is mainly governed by the eddy activity off the eastern taiwan while the wind stress curl plays a major role in the kuroshio in the east of luzon and in the luzon strait the wind stress induced ekman transport plays a secondary role in regulating the kuroshio east of luzon in addition the multidecadal fluctuation of kuroshio east of luzon also modulates the westward intrusion in the luzon strait instead the ekman transport dominated the whole upstream kuroshio area from the eastern luzon to the vicinity of taiwan during the exceptional decade of 1980 associated changes of water properties in the northern south china sea and southern east china sea are also ascribed to the multidecadal changes of surface kuroshio in the upstream area

local and regional p wave spectral attenuation model for iran a robust frequency dependent local and regional p wave attenuation model is estimated for continental paths in the iranian plateau in order to calculate the average attenuation parameters 46 337 vertical component waveforms related to 9267 earthquakes which are recorded at the iranian seismological center irsc stations have been selected in the distance range 10 1000 km the majority of the event s magnitudes are less than 4 5 this collection of records provides high spatial ray path coverage results indicate that the shape of attenuation p wave curve versus distance is not uniform and has three distinct sections with hinges at 90 and 175 km a trilinear model for attenuation of p wave amplitude in the frequency range 1 10 hz is proposed in this study fourier spectral amplitudes are found to decay as r 1 2 where r is hypocentral distance corresponding to geometric spreading within 90 km from the source there is a section from 90 to 175 km where the attenuation is described as r 0 8 and the attenuation is described well beyond 175 km by r 1 3 moreover the average quality factor for pg and pn waves qpg and qpn related to anelastic attenuation is obtained as qpg 54 2 2 6 f 1 0096 0 07 and qpn 306 8 7 4 f 0 51 0 05 there is a good agreement between the results of the model and observations also the attenuation model shows compatibility with the recent regional studies from the results it turns out that the amplitude of p waves attenuates more rapidly in comparison with the global models in local distances

high resolution image of uppermost mantle beneath ne iran continental collision zone we invert 3775 relative p wave arrival times using the ach damped least square method of aki et al 1977 to study upper mantle structure beneath the ne iran continental collision zone the data for this study were recorded by 17 three component broad band stations operated from august 2006 to february 2008 along a profile from the center of iranian plateau near yazd to the northeastern part of iran on the turan platform just north of the kopeh dagh mountains the results confirm the previously known low velocity upper mantle beneath central iran our tomographic model reveals a deep high velocity anomaly the surficial expressions of this anomaly are between the ashkabad and doruneh faults where the resolution and ray coverage are good a transition zone in uppermost mantle is recognized under the binalud foreland that we interpreted as suture zone between iran and turan platform our results indicate that atrak valley which is the boundary between the binalud and kopeh dagh mountains can be considered as the northeastern suture of the iranian plateau where eurasia and turan platform under thrust beneath the binalud range and central iran

modeling the flexural evolution of the amiran and mesopotamian foreland basins of nw zagros iran iraq the evolution of the amiran and mesopotamian flexural basins of the zagros belt is approached by coupled 2 d forward modeling of orogenic wedge formation lithospheric flexural isostasy and stream power erosion transport sedimentation thrust geometries and sequence of emplacement derived from geometric and kinematic models presented here are the inputs to our evolutionary model constrained by basin geometry sediment volume and topography modeling results confirm that the zagros flexural basins evolution is consistent with two stages of deformation 1 the obduction stage involving the kermanshah accretionary complex and a basement unit and 2 the collision stage emplacing the gaveh rud and sanandaj sirjan domains in the hinterland and forming a basement duplex in the outer part results provide quantitative insights into processes involved in mountain and basin building the lithospheric equivalent elastic thickness te changed from 20 km during the amiran stage 90 50 ma to 55 km during the mesopotamian subsidence stage last 20 myr the amiran basin results from flexure of the arabian plate below the load of the kermanshah cover and basement thrust sheets during this stage material eroded in the inner parts was enough to fill the flexural trough the mesopotamian basin formed in front of the outermost basement units flexing the arabian plate during this latter stage material eroded from the orogenic wedge was not enough to fill the mesopotamian basin an additional longitudinal sediment supply of up to 200 m myr is required to fill the flexural basin

pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the arabian eurasian and african plates an edited version of this paper was published by blackwell publishing in geophysical journal international copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02355 x http atlas geo cornell edu middleeastnorthafrica publications al lazki2004 htm

east anatolian high plateau as a mantle supported north south shortened domal structure an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl017858 shtml http atlas geo cornell edu turkey publications sengor et al 2003 htm

crustal and uppermost mantle structure in the middle east assessing constraints provided by jointly modelling ps and sp receiver functions and rayleigh wave group velocity dispersion curves

seismological evidence for crustal scale thrusting in the zagros mountain belt iran summary crustal receiver functions rfs computed from the records of 45 temporary seismological stations installed on a 620 km long profile across central zagros provide the first direct evidence for crustal thickening in this mountain belt due to a rather short 14 km average station spacing the migrated section computed from radial rfs displays the moho depth variations across the belt with good spatial resolution from the coast of the persian gulf to 25 km southwest of the main zagros thrust mzt the moho is almost horizontal with slight depth variations around 45 km crustal thickness then increases abruptly to a maximum of 70 km beneath the sanandaj sirjan metamorphic zone between 50 and 90 km northeast of the surface exposure of the mzt further northeast the moho depth decreases to 42 km beneath the urumiehdokhtar magmatic assemblage and the southern part of the central iranian microcontinent the region of thickest crust is located 75 km to the northeast of the bouguer anomaly low at 220 mgals gravity modelling shows that the measured moho depth variations can be reconciled with gravity observations by assuming that the crust of zagros underthrusts the crust of central iran along the mzt considered as a crustal scale structure this hypothesis is compatible with shortening estimates by balanced cross sections of the zagros folded belt as well as with structural and petrological studies of the metamorphic sanandaj sirjan zone

crustal and uppermost mantle shear wave velocity structure beneath the middle east from surface wave tomography we have constructed a 3 d shear wave velocity vs model for the crust and uppermost mantle beneath the middle east using rayleigh wave records obtained from ambient noise cross correlations and regional earthquakes we combined one decade of data collected from 852 permanent and temporary broadband stations in the region to calculate group velocity dispersion curves a compilation of 54000 ray paths provides reliable group velocity measurements for periods between 2 and 150 s path averaged group velocities calculated at different periods were inverted for 2 d group velocity maps to overcome the problem of heterogeneous ray coverage we used an adaptive grid parametrization for the group velocity tomographic inversion we then sample the period dependent group velocity field at each cell of a predefined grid to generate 1 d group velocity dispersion curves which are subsequently inverted for 1 d vs models beneath each cell and combined to approximate the 3 d vs structure of the area the vs model shows low velocities at shallow depths 5 10 km beneath the mesopotamian foredeep south caspian basin and the black sea possibly indicating a relatively thin crust in contrast the zagros mountain range the sanandaj sirjan metamorphic zone in western central iran the easternmost anatolian plateau and lesser caucasus are characterized by low velocities at these depths some of these anomalies may be related to thick crustal roots that support the high topography of these regions in the upper mantle depth range high velocity anomalies are obtained beneath the arabian platform southern zagros persian gulf and the eastern mediterranean in contrast to low velocities beneath the red sea arabian shield afar depression eastern turkey and lut block in eastern iran our vs model may be used as a new reference crustal model for the middle east in a broad range of future studies

closing the gap between regional and global travel time tomography recent global travel time tomography studies by zhou 1996 and van der hilst et al 1997 have been performed with cell parameterizations of the order of those frequently used in regional tomography studies i e with cell sizes of 1 2 these new global models constitute a considerable improvement over previous results that were obtained with rather coarse parameterizations 5 cells the inferred structures are however of larger scale than is usually obtained in regional models and it is not clear where and if individual cells are actually resolved this study aims at resolving lateral heterogeneity on scales as small as 0 6 in the upper mantle and 1 2 3 in the lower mantle this allows for the adequate mapping of expected small scale structures induced by for example lithosphere subduction deep mantle upwellings and mid ocean ridges there are three major contributions that allow for this advancement first we employ an irregular grid of nonoverlapping cells adapted to the heterogeneous sampling of the earth s mantle by seismic waves spakman and bijwaard 1998 second we exploit the global data set of engdahl et al 1998 which is a reprocessed version of the global data set of the international seismological centre their reprocessing included hypocenter redetermination and phase reidentification finally we combine all data used p pp and pwp phases into nearly 5 million ray bundles with a limited spatial extent such that averaging over large mantle volumes is prevented while the signal to noise ratio is improved in the approximate solution of the huge inverse problem we obtain a variance reduction of 57 1 synthetic sensitivity tests indicate horizontal resolution on the scale of the smallest cells 0 6 or 1 2 in the shallow parts of subduction zones decreasing to approximately 2 3 resolution in well sampled regions in the lower mantle vertical resolution can be worse up to several hundreds of kilometers in subduction zones with rays predominantly pointing along dip important features of the solution are as follows 100 200 km thick high velocity slabs beneath all major subduction zones sometimes flattening in the transition zone and sometimes directly penetrating into the lower mantle large high velocity anomalies in the lower mantle that have been attributed to subduction of the tethys ocean and the farallon plate and low velocity anomalies continuing across the 660 km discontinuity to hotspots at the surface under iceland east africa the canary islands yellowstone and the society islands our findings corroborate that the 660 km boundary may resist but not prevent present day large scale mass transfer from upper to lower mantle or vice versa this observation confirms the results of previous global mantle studies that employed coarser parameterizations

building the zagros collisional orogen timing strain distribution and the dynamics of arabia eurasia plate convergence he zagros mountains are the result of the arabia eurasia collision initiated at 35 ma as the rifted arabian lithosphere was underthrusted beneath the iranian plate due to its negative buoyancy the onset of crustal thickening started at 25 ma as recorded by the hinterland exhumation and foreland clastic deposition deformation throughout the arabia eurasia collision zone and the uplift of the iranian plateau occurred after 15 12 ma as a result of shortening thickening of the thin iranian crust we emphasize that only 42 of the post 35 ma convergence is partitioned by shortening within central iran tomographic constraints show ongoing slab steepening or breakoff in the nw zagros whereas underthrusting of the arabian plate is observed beneath central zagros the current subduction dynamics can be explained by the original lateral difference in the buoyancy of the distal margin that promoted slab sinking in nw zagros and underthrusting in central zagros critical wedge approach applied to the zagros favors the hypothesis of strong brittle crust detached above a viscous lower crust in contrast the weak sedimentary cover deforms by buckling of a thick multilayered cover thrust faulting associated with folding occurs in the competent layers and is responsible for most of the earthquakes there is evidence that the role of the slab pull force in driving the arabian plate motion was reduced after 12 ma large scale mantle flow induced by mantle upwelling at the afar plume appears to be the main driver of the arabia plate motion we stress that the main kinematic change in the zagros region occurred at 15 12 ma as the zagros uplifted before the arabian slab detached the zagros appears key to investigate coupling between continental rheology plate driving forces and mountain building in which the role of rift inheritance appears to be central

seismic imaging of the lithospheric structure of the zagros mountain belt iran we present a synthesis and a comparison of the results of two temporary passive seismic experiments installed for a few months across central and northern zagros the receiver function analysis of teleseismic earthquake records gives a high resolution image of the moho beneath the seismic transects on both cross sections the crust has an average thickness of 43 2 km beneath the zagros fold and thrust belt and the central domain the crust is thicker beneath the hanging wall of the main zagros reverse fault mzrf with a larger maximum moho depth in central 69 2 km than in northern zagros 56 2 km the thickening affects a narrower region 170 km beneath the sanandaj sirjan zone of central zagros and a wider region 320 km in northern zagros we propose that this thickening is related to overthrusting of the crust of the arabian margin by the crust of central iran along the mzrf considered as a major thrust fault cross cutting the whole crust the fault is imaged as a lowvelocity layer in the receiver function data of the northern zagros profile moreover the crustal scale thrust model reconciles the imaged seismic moho with the bouguer anomaly data measured on the central zagros transect at upper mantle depth p wave tomography confirms the previously observed strong contrast between the faster velocities of the arabian margin and the lower velocities of the iranian micro blocks our higher resolution tomography combined with surface wave analysis locates the suture in the shallow mantle of the sanandaj sirjan zone beneath central zagros the arabian upper mantle has shield like shear wave velocities while the lower velocities of the iranian upper mantle are likely due to higher temperature but these velocities are not low enough and the low velocity layer not thick enough to conclude on a delamination of the lithospheric mantle lid beneath iran the lack of a high velocity anomaly in the mantle beneath central iran suggests that the neotethyan oceanic lithosphere is probably detached from the arabian margin

convergence history across zagros iran constraints from collisional and earlier deformation the zagros orogen provides a unique opportunity within the alpine system to evaluate the interplay between a young tertiary collision and earlier subduction obduction processes within the crush zone and the sanandaj sirjan internal zone separating the zagros fold belt from central iran we document several major tectonic events taking place at the end of the cretaceous of the eocene and from the mio pliocene onwards ca 20 15 ma contrary to recent interpretations our data cross sections and description of the overall deformation style strongly suggest that the main zagros thrust mzt is deeply rooted possibly to moho depths and that the suture zone effectively runs along the mzt field observations show that the final resorption of the oceanic domain took place slightly after 35 ma and that collision must have started before ca 23 25 ma in northern zagros the shortening rate across the crush zone since the mid miocene 20 15 ma is estimated at a minimum 3 4 mm year shear movements in the crush zone during the eocene oligocene period and extensional strike slip movements in the internal zones during the late cretaceous point to an oblique setting early in the convergence history a geotectonic scenario for convergence from the time of obduction to the present is finally proposed

surface waveform tomography of the turkish iranian plateau summary the middle east is a tectonically complex region consisting of terrains as diverse as precam brian shields and young orogens the dominant tectonic feature is the turkish iranian plateau a recently elevated seismically active region along the zagros bitlis suture which results from the collision of the arabian plate with eurasia in this study we use surface waveform tomography to elucidate the upper mantle shear wave velocity structure beneath the turkish iranian plateau and adjacent regions the main large scale feature in the tomographic model is a low shear wave velocity anomaly in the uppermost mantle beneath the plateau this low velocity feature correlates with a long wavelength free air gravity anomaly and with recent volcanism whose geochemistry has a lower lithospheric mantle signature seismology gravity and volcanism all suggest the presence of a thin lithosphere and warm upper mantle beneath the turkish iranian plateau the upper mantle low shear wave velocity zone the high free air gravity and the deep lithospheric source depth for the basaltic volcanism are all consistent with a partial delamination of the lithosphere as a result of earlier lithospheric thickening resulting from the continental collision

late cenozoic partitioning of oblique plate convergence in the zagros fold and thrust belt iran the nw trending zagros fold and thrust belt is affected by two major dextral faults 1 the nw trending main recent fault that accommodates partitioning of oblique convergence at the rear of the western zagros and 2 the north trending kazerun fault located in the central zagros combined structural and fault kinematics studies and spot images analysis have shown a pliocene kinematic change accompanied by a fault pattern reorganization which has led to a modification in the accommodation of oblique convergence since the late pliocene the distributed transpressional deformation operating at the rear of the belt has become partitioned along the newly formed main recent fault this fault cuts through early pliocene nappes and transpressional structures by right laterally reactivating high angle thrusts the southeastern termination of the main recent fault connects to the northern termination of kazerun fault that consists of three fault zones that end in bent orogen parallel splay thrust faults the kazerun fault together with a series of north to nnw trending inherited basement strike slip faults define an orogen scale fan shaped fault pattern pointing toward the main recent fault kazerun fault junction this structural pattern allows slip from along the main recent fault to become distributed by transfer to the longitudinal thrust faults and folds of the zagros belt with the fan shaped fault pattern acting as a horse tail termination of the main recent fault

contractional salt tectonic system in the south dezful embayment zagros abstract the dezful embayment in zagros has traditionally been interpreted as a typical fold belt with multiple detachment levels including a lower detachment at the basement cover interface and an upper detachment along the miocene gachsaran halite bearing evaporites this paper constrains diapiric processes in the gachsaran detachment coeval with regional shortening that resulted in complex and hitherto unstudied salt structures and flanking synclinal minibasins in this paper well tied seismic interpretation is integrated with field and remote sensing mapping cross section construction and stepwise tectono sedimentary restoration the results indicate that after the deposition of mishan lower aghajari pre kinematic overburden sediments detachment folding initiated above the gachsaran evaporites during late tortonian times as a result of regional shortening the salt cored anticlines later actively pierced their roof to subsequently rise as passive diapirs and evolve into salt walls synclinal minibasins developed due to salt evacuation into flanking walls during the deposition of the lahbari mb in messinian pliocene remarkable sedimentary thickening and lateral shifts in minibasin depocenter towards the salt walls accompanied by overturned collars and hook halokinetic sequences are diagnostics of near surface syndepositional passive growth of diapirs during this stage from pliocene to recent the major episode of regional shortening has squeezed these precursor salt walls to form thrust welds in conclusion the well exposed structures of south dezful show an early shortening stage then a transition to a combination of shortening and passive diapirism and final thrusting along diapirs this evolution model may be more common in other salt influenced fold thrust belts than is currently recognized

early neogene foreland of the zagros implications for the initial closure of the neo tethys and kinematics of crustal shortening we study the transition from passive margin to foreland basin sedimentation now exposed in the high zagros belt to provide chronological constraints on the initial stage of arabia eurasia collision and closure of the neo tethys we performed magnetostratigraphy and strontium isotope stratigraphy along two sections near the zagros suture which expose the oldest preserved foreland deposits the shalamzar section in the west and the dehmoord section in the east the top of the passive margin asmari formation has an age of 28 29 ma in the high zagros and is overlain by foreland deposits with a major basal unconformity representing 7 myr of hiatus the base of the foreland deposits has an age of 21 5 ma at dehmoord and ca 26 ma at shalamzar the sedimentation rate increased from 30 m myr in the passive margin to 247 m myr in the foreland combined with available age constraints across the zagros our results show that the unconformity is diachronous and records the southwestward migration of the flexural bulge within the arabian plate at an average rate of 24 2 mm yr over the last 27 ma the time evolution of sediment accumulation in the zagros foreland follows the prediction from a flexural model as the foreland is thrust beneath the orogenic wedge and loaded by the wedge and basin fill we detect the onset of forebulge formation within the asmari formation around 25 ma we conclude that closure of the neo tethys formed the zagros collisional wedge at 27 2 ma hence the arabia eurasia collision was probably not the main driver of global cooling which started near the eocene oligocene boundary ca 33 7 ma we estimate 650 km of forebulge migration since the onset of the collision which consists of 350 km of shortening across the orogen and 300 km of widening of the wedge and increasing flexural rigidity of arabia we conclude the average rate of shortening across the zagros to be ca 13 mm yr over the last 27 myr a value comparable to the modern rate palinspastic restoration of structural cross sections and crustal volume conservation comprise only ca 200 km of shortening across the zagros and metamorphic sanandaj sirjan belt implying that at least 150 km of the arabian crust was underthrust beneath eurasia without contributing to crustal thickening possibly due to eclogitization

tectonic magmatic and metallogenic evolution of the tethyan orogen from subduction to collision abstract this paper reviews the tectonic magmatic and metallogenic history of the tethyan orogen from the carpathians to indochina focus is placed on the formation of porphyry cu mo au deposits as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region relatively little is known about the history of the paleotethys ocean which opened and closed between gondwana and eurasia in the paleozoic and few ore deposits are preserved from this period the neotethyan ocean opened in the permian early triassic as the cimmerian continental fragments the cores of turkey iran tibet and indochina rifted from the northern gondwana margin and drifted northwards these microcontinents docked with the eurasian margin at various points in the mesozoic and cenozoic and formed a complex archipelago involving several small back arc basins and remnants of the paleotethyan ocean the main neotethyan ocean and these smaller basins were largely eliminated by collision with india and africa arabia in the early eocene and early mid miocene respectively although neotethyan subduction continues beneath the hellenic arc and the makran the majority of porphyry type deposits are found in association with neotethyan subduction mainly in the mesozoic and paleogene and syn to post collisional events in the mid paleogene to neogene they are found throughout the orogen but some sections are particularly well endowed including the carpathians balkans rhodopes eastern turkey lesser caucasus nw iran se iran sw pakistan southern tibet and se tibet indochina other sections that appear barren may reflect deeper levels of erosion young sedimentary cover or lack of exploration although there may also be real reasons for low prospectivity in some areas such as minimal subduction e g the western mediterranean region or lithospheric underthrusting as proposed in western tibet over the last decade improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction related are in fact broadly collision related some forming in back arc settings in advance of collision some during collision and others during post collisional processes such as orogenic collapse and or delamination of subcontinental mantle lithosphere while the formation of subduction related porphyries is quite well understood collisional metallogeny is more complex and may involve a number of different processes or sources these include melting of orogenically thickened crust previously subduction modified lithosphere including metasomatized mantle underplated mafic rocks or lower crustal arc plutons and cumulates or upwelling asthenosphere e g in response to delamination slab breakoff back arc extension or orogenic collapse the most fertile sources for syn and post collisional porphyry deposits appear to be subduction modified lithosphere because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events and retain the oxidized and relatively metalliferous character of the original arc magmatism unusually metallically enriched lithospheric sources do not seem to be required but the amount of residual sulfide phases in these rocks may control metal ratios e g cu au in subsequent magmatic hydrothermal ore deposits relatively au rich deposits potentially form in these settings as observed in the carpathians e g rosia montan turkey kisladag copler and iran sari gunay dalli although the majority of syn and post collisional porphyries are cu mo rich and resemble normal subduction related deposits e g in the gangdese belt of southern tibet this similarity extends to the associated igneous rocks which being derived from subduction modified sources largely retain the geochemical and isotopic character of those original arc magmas while still retaining a broadly calc alkaline character these rocks may extend to mildly alkaline shoshonitic compositions and may display adakite like trace element signatures high sr y and la yb ratios reflecting melting of deep crustal garnet amphibolitic sources but they are otherwise hard to distinguish from normal subduction related magmas small post collisional mafic alkaline volcanic centers are common throughout the orogen but for the most part appear to be barren however similar rocks in other post subduction settings around the world are associated with important alkalic type porphyry and epithermal au cu deposits and the potential for discovery of such deposits in the tethyan orogen should not be overlooked

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

the south zagros suture zone in teleseismic images abstract the geometry of intra continental lithosphere boundaries along the zagros orogenic belt in the arabia eurasia collision is investigated by means of teleseismic data the data are gathered over a seismic linear profile extending across south zagros the sanandaj sirjan metamorphic zone the urumieh dokhtar magmatic arc central iran and the kopeh dagh binalud mountains we exploit the p and s receiver functions leading to map the geometry of the crustal and subcrustal interfaces the migrated depth sections reveal an abrupt crustal thickening and a gentle crustal thinning 60 km north and 30 km south of the zagros suture respectively associated to the buckled antiformal moho south of the suture a deeper synform in the lithospheric lid of the lower arabia plate is shown by migrated depth sections affecting the lithospheric mantle of the arabia plate beneath the suture zone this geometry implies an unexpected intra lid decoupling these features imply that the central iran lithosphere acts as a relatively strong backstop producing significant internal deformation expressed by shortening and thickening at the edge of the arabian lithosphere the 410 km and 660 km transition zones are imaged by p to s converted phases and showed lateral continuity implying an originally low dip angle subduction of the oceanic arabian plate beneath central iran

the southern zagros collisional orogen new insights from transdimensional trees inversion of seismic noise the natural environmental research council nerc grant ne r013500 1 and from the european union s horizon 2020 research and innovation program under marie sklodowska curie grant agreement 790203

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

the structure and kinematics of the southeastern zagros fold thrust belt iran from thin skinned to thick skinned tectonics 1 we present the first complete balanced cross section across the southeastern zagros fold thrust belt zftb the following main structural features emerge from this section 1 in the south of the zftb the proterozoic to recent sedimentary sequence has been decoupled from its panafrican basement along the ductile basal evaporites and folded into a series of large detachment anticlines ongoing shortening of these structures has resulted in migration of the basal salt layers into the cores of the anticlines and propagation of forelimb thrusts 2 in the north of the zftb deep seated ramps have folded the hanging wall rocks and produced imbrications and duplex structures within the higher levels of the sedimentary sequence 3 out of sequence thrusts linked to major seismogenic basement faults have cut through the structures in the cover of the zftb a three step incremental restoration of the section shows that two main phases of deformation can be separated in the tectonic evolution of the zftb a mio pliocene thin skinned phase in the course of which most of the structures in the cover were generated followed by a pliocene to recent thick skinned phase expressed as out of sequence faulting in the cover which is currently underlined by the seismicity within the basement in plan view the initial structures of the southeastern zftb developed with a curved shape essentially controlled by the shape and thickness of the underlying proterozoic salt basin i e the jura style in the following basement involved phase out of sequence thrusts cut at oblique angles through the preexisting structures of the cover the total shortening absorbed in the cover amounts to at least 45 km corresponding to a ratio of 22

new views on earthquake faulting in the zagros fold and thrust belt of iran the zagros fold and thrust belt is amongst the world s most seismically active mountain ranges and is influential in our understanding of continental collisions the presence of hormuz salt at the base of the 10 km thick folded sedimentary cover together with the general absence of coseismic surface rupturing have led to an assumption that earthquakes are concentrated within the basement here we reinterpret the seismicity of the zagros in light of insar studies that show some recent earthquakes ruptured the competent group of mechanically strong strata in the lower sedimentary cover local network data demonstrate that microseismicity occurs within the basement reaching depths of 20 km and in places 30 km centroid depths of larger mw 5 earthquakes are mostly 4 14 km with rare events up to 20 km and 28 km along the oman line within the simply folded belt most of these events are contained within the competent group and are limited to mw 6 5 earthquakes occur earthquakes within the competent group can account for much of the overall shortening at this level but the seismic strain rate in the basement is much lower it is unclear whether the basement deforms by aseismic creep or folding beneath the sfb or by ductile shortening beneath the high zagros or iranian plateau

3d joint inversion modeling of the lithospheric density structure based on gravity geoid and topography data application to the alborz mountains iran and south caspian basin region abstract we present a 3d algorithm to obtain the density structure of the lithosphere from joint inversion of free air gravity geoid and topography data based on a bayesian approach with gaussian probability density functions the algorithm delivers the crustal and lithospheric thicknesses and the average crustal density stabilization of the inversion process may be obtained through parameter damping and smoothing as well as use of a priori information like crustal thicknesses from seismic profiles the algorithm is applied to synthetic models in order to demonstrate its usefulness a real data application is presented for the area of northern iran with the alborz mountains as main target and the south caspian basin the resulting model shows an important crustal root up to 55 km under the alborz mountains and a thin crust ca 30 km under the southernmost south caspian basin thickening northward to the apsheron balkan sill to 45 km central and nw iran is underlain by a thin lithosphere ca 90 100 km the lithosphere thickens under the south caspian basin until the apsheron balkan sill where it reaches more than 240 km under the stable turan platform we find a lithospheric thickness of 160 180 km

the distribution of moho depths beneath the arabian plate and margins abstract in this study three new maps of moho depths beneath the arabian plate and margins are presented the first map is based on the combined gravity model eigen 06c which includes data from satellite missions and ground based studies and thus covers the whole region between 31 e and 60 e and between 12 n and 36 n the second map is based on seismological and ground based gravity data while the third map is based only on seismological data both these maps show gaps due to lack of data coverage especially in the interior of the arabian plate beneath the interior of the arabian plate the moho lies between 32 and 45 km depth below sea level there is a tendency for higher pn and sn velocities beneath the northeastern parts of the plate interior with respect to the southwestern parts of the plate interior across the northern destructive margin with the eurasian plate the moho depths increase to over 50 km beneath the zagros mountains across the conservative western margin the dead sea transform dst moho depths decrease from almost 40 km beneath the highlands east of the dst to about 21 23 km under the southeastern mediterranean sea this decrease seems to be modulated by a slight depression in the moho beneath the southern dst the constructive southwestern and southeastern margins of the arabian plate also show the moho shallowing from the plate interior towards the plate boundaries a comparison of the abruptness of the moho shallowing between the margins of the arabian plate the conjugate african margin at 26 n and several atlantic margins shows a complex picture and suggests that the abruptness of the moho shallowing may reflect fundamental differences in the original structure of the margins

seismic tomographic imaging of p and s waves velocity perturbations in the upper mantle beneath iran summary the inverse tomography method has been used to study the p and s waves velocity structure of the crust and upper mantle underneath iran the method based on the principle of source receiver reciprocity allows for tomographic studies of regions with sparse distribution of seismic stations if the region has sufficient seismicity the arrival times of body waves from earthquakes in the study area as reported in the isc catalogue 1964 1996 at all available epicentral distances are used for calculation of residual arrival times prior to inversion we have relocated hypocentres based on a 1 d spherical earth s model taking into account variable crustal thickness and surface topography during the inversion seismic sources are further relocated simultaneously with the calculation of velocity perturbations with a series of synthetic tests we demonstrate the power of the algorithm and the data to reconstruct introduced anomalies using the ray paths of the real data set and taking into account the measurement errors and outliers the velocity anomalies show that the crust and upper mantle beneath the iranian plateau comprises a low velocity domain between the arabian plate and the caspian block this is in agreement with global tomographic models and also tectonic models in which active iranian plateau is trapped between the stable turan plate in the north and the arabian shield in the south our results show clear evidence of the mainly aseismic subduction of the oceanic crust of the oman sea underneath the iranian plateau however along the zagros suture zone the subduction pattern is more complex than at makran where the collision of the two plates is highly seismic