paleoseismological and morphological evidence of slip rate variations along the north tabriz fault nw iran northwest iran is characterized by a high level of historical and instrumental seismicity related to the ongoing convergence between the arabian and eurasian plates in this region the main right lateral strike slip fault known as the north tabriz fault ntf forms the central portion of a large crustal fault system called the tabriz fault system tfs the ntf is a major seismic source along which at least three strong and destructive earthquakes have occurred since 858 ad the two most recent destructive seismic events occurred in 1721 ad and 1780 ad rupturing the se and nw fault segments respectively this paper reports paleoseismological and quantitative geomorphologic investigations on the se segment of the ntf between the cities of bostanabad and tabriz these observations help to improve our understanding of the seismic hazard for tabriz city and its surrounding areas our field investigations revealed evidence of successive faulting events since the late quaternary paleoseismic investigations indicate that since 33 5 kyr the se segment of the ntf has experienced at least three major m 7 5 seismic events including the 1721 ad earthquake m 7 6 7 7 along the nw segment of the fault however our results suggest that the amount of strong m 7 5 seismic events during the same period is significantly greater than along the se segment one possible explanation of such a difference in seismic activity is that the late quaternary holocene coseismic slip rate is decreasing along the ntf from the northwest to the southeast this explanation contradicts the former hypothesis of a constant slip rate along the whole length of the ntf in addition more distributed deformation along several parallel fault branches in a wider fault zone of the se segment of the ntf may be considered as additional evidence for the estimation of lower rate of deformation along the fault segment such a slip distribution pattern can explain the existence of smaller 300 m pliocene quaternary cumulative dextral offsets along the se fault segment than the measured cumulative offsets along the nw segment 800 m of the ntf

initiation of the neomagmatism in east anatolia abstract in eastern anatolia the neotectonic episode commenced with the complete elemination of the neo tethyan ocean floor as a result of collision between arabia and eurasia during early miocene time after the collision continuing convergence initiated a new tectonic regime and coeval magmatic activity the post collisional convergence caused crustal shortening and thickening as evidenced by regionwide development of e w trending folds and thrusts and conjugate strike slip faults the related volcanic activity has progressed in three cycles in the initial cycle weakly alkaline volcanic rocks were produced that are known as the solhan volcanics they outcrop at the western end of an e w striking neotectonic depression called the mus basin which constitutes the western prolongation of the lake van basin the basin is a thrust bounded depression that developed out of an original syncline by the disruption of its limbs the lavas of the first cycle reached the surface along n s aligned extensional structures in the second volcanic cycle a widespread k type ca volcanism occurred through crustal contribution during the late miocene early pliocene time when the continuing north south convergence caused substantial shortening and thickening of the continental crust the last volcanic cycle produced a thick volcanic cover consisting of rocks of alkaline affinity during the pleistocene and the quaternary when the thickened crust began to accommodate the ongoing north south shortening by east west extension after the formation of the east and north anatolian transform faults

eastern turkish high plateau as a small turkic type orogen implications for post collisional crust forming processes in turkic type orogens abstract post collisional magmatism may be generated by extensive crustal melting in tibet type collisional environments or by falling out of slabs from under giant subduction accretion complexes in turkic type collisional orogens giving rise to decompression melting of the asthenospheric mantle replacing the removed oceanic lithosphere in turkic type post collisional magmatism the magmatic products are dominantly alkalic to peralkalic and greatly resemble those of extensional regions giving rise to much confusion especially in interpreting old collisional orogenic belts such magmatic regions are also host to a variety of economically valuable ore deposits including gold one place in the world where today active turkic type post collisional magmatism is present is the eastern anatolian high plateau produced after the terminal arabia eurasia collision in the late miocene the plateau is mostly underlain by the late cretaceous to oligocene east anatolian accretionary complex which formed south of the rhodope pontide magmatic arc this subduction accretion complex has been further shortening since the collision but it has also since been domed and became almost entirely covered by at least 15 000 km3 of volcanic rocks the volcanic rocks are calc alkalic in the north transitional in the middle and alkalic in the south of the plateau where the crust is thinnest today less than 38 km the volcanics are derived almost entirely from an enriched mantle the ages of the volcanics also become younger from north to south from about 11 ma to possibly 17th century ad we interpret the origin of the magmatic rocks as the result of decompression melting of the asthenospheric mantle sucked towards the exposed base of the east anatolian accretionary complex as the oceanic lithosphere beneath it fell out the lower density of the hot asthospheric material was the cause of the doming we believe that similar processes dominated the post collisional tectonics of such vast turkic type orogens as the altaids of central asia the late devonian early carboniferous lachlan belt in southeastern australia and the pan african collage of northeast afro arabia it is likely that archaean collisions were dominated by turkic type post collisional events rather than tibetan ones that only became common in the proterozoic

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

geochemical features of collision related volcanic rocks in central and eastern anatolia turkey in central and eastern anatolia volcanism related to continental collision occurred in neogene to quaternary times major and trace element compositions 87sr86 sr and k ar ages were determined for volcanic rocks from selected volcanoes in this region 87sr86 sr for basalts from erciyes volcano in the eastern part of central anatolia as well as ararat nemrut and karacadag volcanoes in eastern anatolia are in the range 0 7035 0 7040 these ratios are higher than those of n type morb but overlap arc volcanic rock values this suggests that the mantle source which was possibly contaminated by fluids and melts with higher87sr86 sr during the pre collisional events has similar sr isotopic compositions in wide areas of the eastern part of central anatolia and eastern anatolia even across the collision plate boundary in addition chemical compositions of the mantle source are not homogeneous with respect to hfs element contents indicating that the slab derived components resulting from past subductions are not homogeneously distributed the mantle source beneath the western part of central anatolia which corresponds to the transitional region from collision tectonics in the east to subduction tectonics in the west has different chemical and sr isotopic signatures from other parts of anatolia in the western part of central anatolia the87sr86 sr of basaltic rocks from three regions characterized by monogenetic volcanoes are in the range 0 70427 to 0 70581 and differ from region to region in spite of indistinguishable chemical compositions this indicates either source heterogeneity on a small scale or different contributions of local crustal contaminants calc alkaline lavas from ararat and kars in eastern anatolia have chemical compositions with subduction signatures inherited from pre collision subduction events in contrast the chemical and sr isotopic features of volcanic rocks from erciyes volcano in central anatolia indicate that the combined process of fractional crystallization of basaltic magma and crustal assimilation without injection of slab derived components is the dominant process generating calc alkaline andesite under the collision tectonics regime operating in this region

regional wave propagation in turkey and surrounding regions this paper was published by the american geophysical union agu copyright 2000 agu see also http www agu org journals gl gl0003 1999gl008375 pdf 1999gl008375 pdf http atlas geo cornell edu turkey publications gok et al 2000 htm

paleostress reconstructions and geodynamics of the baikal region central asia part 2 cenozoic rifting abstract investigations on the kinematics of rift opening and the associated stress field present a renewed interest since it has recently been shown that the control of the origin and evolution of sedimentary basins depends to a large extent on the interplay between lithospheric strength and applied stresses it appears that changes of stress field with time are an important factor that either controls or results from the rifting process the object of this paper is to study the changes of fault kinematics and paleostress field with time in the baikal rift system during the cenozoic reduced paleostress tensors were determined by inversion from fault slip data measured in the central part of the rift and its southwestern termination between 1991 and 1995 results show that the stress field varies as well in time as in space two major paleostress stages are determined corresponding broadly to the classical stages of rift evolution late oligocene early pliocene and late pliocene quaternary the first paleostress stage is related to the rift initiation and the second to the major stage of rift development similarities between the recent paleostress field and the present day stress field inverted from focal mechanisms indicate that the second paleostress stage is still active therefore we propose to use proto rift for the late oligocene early pliocene stage and active rift for the late pliocene quaternary stage of rift development during the proto rift stage the stress field was characterized by a compressional to strike slip regime a progressive change from transpression to transtension is suspected for the central part of the rift baikal and barguzin basins during this period in the western termination of the rift sayan massif tunka depression a strongly compressional stress field with oblique thrusting kinematics is well constrained in the late miocene early pliocene interval the active rift stage was initiated by a marked change in fault kinematics and stress regime in the late pliocene in the central part of the rift the stress regime changed into pure extension while in the southwestern extremity it changed into pure strike slip fault kinematics suggests that rifting was initiated by an extrusion mechanism due to the interaction of far field compressional stress on a mechanically heterogeneous crust with the southwards pointing wedge of the siberian craton acting as a passive indentor the cenozoic time space evolution of the stress field is believed to reflect the increasing influence of locally generated buoyancy extensional stresses associated with density anomalies of the lithosphere on intraplate stresses generated by the india eurasia convergence and the west pacific subduction

active faulting and natural hazards in armenia eastern turkey and northwestern iran active fault zones of armenia se turkey and nw iran present a diverse set of interrelated natural hazards three regional case studies in this cross border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster in northern armenia a combination of several natural and man made phenomena earthquakes landslides and unstable dams with toxic wastes along the pambak sevan sunik fault pssf zone lowers from 0 4 to 0 2 0 3g the maximum permissible level mpl of seismic hazard that may induce disastrous destruction and loss of life in the adjacent vanadzor depression in the ararat depression a large active fault bounded pull apart basin at the junction of borders of armenia turkey iran and azerbaijan an earthquake in 1840 was accompanied by an eruption of ararat volcano lahars landslides floods soil subsidence and liquefaction the case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact the north tabriz gailatu fault system poses a high seismic hazard to the border areas of nw iran eastern turkey nakhichevan azerbaijan and southern armenia right lateral strike slip motions along the north tabriz fault have given rise to strong earthquakes which threaten the city of tabriz with its population of 1 2 million the examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in armenia eastern turkey and nw iran this generally occurs across the junctions of international borders hence the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

seismic stratigraphy of lake van eastern turkey more than 1500 km of multi channel seismic reflection profiles combined with icdp international continental scientific drilling program drilling data provide important insights into the stratigraphic evolution of lake van eastern turkey three major basins tatvan northern and the deveboynu basins comprise the main lake basin and are separated by morphological highs ahlat ridge and northern ridge moreover ne sw faults parallel to the general tectonic lineament of the area dominate the entire basin and are in charge of creating graben and half graben structures well developed prograding deltaic sequences on top of the basement were recognized by seismic stratigraphy analysis most likely they formed during the initial flooding of lake van 600 ka the tatvan basin sediments are dominated by mass flow deposits of various origins alternating with undisturbed lacustrine sediments including distinct tephra layers faulting along the tatvan basin margins may have triggered margin wide slope failures ahlat ridge started to form between ca 340 ka 290 ka since then ahlat ridge was sheltered from major mass flows due to its elevation hence slow lacustrine sedimentation has prevailed throughout lake history on ahlat ridge which was the location of the main drill site during the icdp several lake level fluctuations are evident on the eastern slope area but the deep basins were permanently covered by water a significant lake level low stand ca 600 ka bp was found at 610 m below present lake level the setting of the lake changed at about 30 ka tectonic activity appears to have waned significantly as the mass transport deposition decreased across the tatvan basin while normal undisturbed lacustrine sedimentation prevailed a different setting is found in the northern basin from ca 90 ka to present especially due to the strong influx of mostly volcaniclastic turbidites causing sedimentation rates to be about 3 5 times higher drill site 1 than at site 2 ahlat ridge

review of the neotectonics of the eastern turkish armenian plateau by geomorphic analysis of digital elevation model imagery digital elevation model dem images provide synoptic views of the earth s surface allowing the analysis of landforms of still active tectonic and volcanic structures at regional scale a dem at 250 m pixel size constitutes regional scale data particularly efficient to investigate the late miocene quaternary deformation of the eastern turkish armenian plateau in the arabian eurasian area of convergence geomorphic analysis of the dem image associated with review of fault plane solutions of earthquakes show that faults are mostly strike slip with small vertical component here we show that the orientations of the tectonic and volcanic structures fit with a tectonic regime characterized by n s shortening and e w lengthening consistent with westward escape of anatolia perpendicular to the direction of the arabia eurasia shortening the uniform uplift of the plateau the predominance of strike slip faulting the lack of major thrusts and the occurrence of normal faults do not support a model of going on crustal thickening due to intracontinental convergence on the contrary our observations can be better interpreted in terms of lithospheric thinning and mantle upwelling related to gravity escape of anatolia

evaluation of the plio quaternary tectonic stress regime from fault kinematic analysis in the lake van basin eastern anatolia abstract we focus on the neogene quaternary tectonic evolution of the lake van basin located within the turkish iranian plateau to better understand the complex tectonic history of the region and determine the paleostress patterns we investigate and report on the geometric structural and kinematic characteristics of the basin based on field observations of fault slip orientations which are classified according to radiometric ages of the basin stratigraphy the analysis of large scale structures and fault kinematics indicate that three different deformation phases prevailed in the lake van basin during the neogene quaternary periods phase 1 is characterized by nw se extension and ne sw contraction that gave rise to the development of strike slip faults with thrust or normal components during the late miocene deforming the fluvial sediments which expose at east northeast of the basin phase 2 is characterized in fluvial and lake deposits of the middle pleistocene deformed by dominant contraction stress regime effective along nw se direction the late pleistocene tectonic regime phase 3 consists of transpressional deformation that develops under nnw sse compression and ene wsw extension according to our analysis the present day deformation pattern of the lake van basin is dominated by compression at east while at the northern part is transtensional

gps constraints on continental deformation in the armenian region and lesser caucasus abstract we present the 1998 2009 gps derived velocity field for the armenia region based on a survey mode observation network of 31 gps sites we combine our results with previous gps studies of the region to better assess the deformation of the lesser caucasus and kura basin region the results show that the kura basin and the lesser caucasus regions are two different blocks and that the main fault pambak sevan sunik between these two regions has a right lateral slip rate of 2 1 mm yr this is consistent with morphotectonic estimates and suggests a fairly constant slip rate over the last 120 300 ka the right lateral slip rate on one of the southern branch of the pambak sevan sunik fault is lower than 1 mm yr and the good agreement with a geologically estimated slip rate suggests a constant slip rate over the last 1 4 myr the sardarapat and akhurian faults experience some shortening this shortening is consistent with some independent geological estimates and shows the arabian push however nnw sse orientated faults have an extensional fault normal component instead of the expected shortening due to the arabia eurasia convergence this substantial extensive strain and the sharp azimuth change of the velocity vectors between the arabia promontory and the lesser caucasus suggest that processes other than extrusion possibly related to old subduction or delamination contribute to the geodynamics of the region

chloride contamination in construction aggregates due to periodic saline water intrusion a case study in the kaluganga river estuary sri lanka the kaluganga river estuary is one of the main sources of construction sand in sri lanka salt water intrusion along this estuary due to extensive sand mining has increased over the years thus the focus of the current research is to understand the relationship between river sand mining salt water intrusion and the resultant effects on construction sand two surveys were conducted along the kaluganga estuary along an 11 km stretch from the river mouth at predetermined intervals to measure depth water quality profiles and to collect sediment samples these surveys were carried out during maximum spring tide first in a dry period and then in a wet period to understand hydrographic effects on the quality of river sands sand samples were analysed for absolute chloride content and grain size distribution results showed significant salt water intrusion during the dry period averaging 2 307 s cm 1 in surface waters throughout the surveyed 11 km stretch along with 3 818 s cm 1 average in bottom waters up to 5 6 km upstream from the river mouth causing above normal chloride content in the bottom sandy sediments the high chloride content in bottom sands was recorded up to 5 5 km from the river mouth making them unsuitable for construction purposes however during wet period salt water intrusion levels in the bottom waters were insignificant average 61 s cm 1 and the chloride content in bottom sediments was very low this study highlighted the requirement for regulations on river estuary sandmining for construction purposes

the spitak armenia earthquake of 7 december 1988 field observations seismology and tectonics the epicentre of the destructive earthquake that devastated northern armenia the strongest in the region since historical times is located within the lesser caucasus a mountain country subjected to north south compression by the push of the arabian plate a french soviet field expedition studied surface breaks and aftershock activity the fault scarp could be followed for 13 kilometres and showed a reverse dislocation of 1 6 metres aftershocks are shallower than 13 kilometres and delimit a ruptured surface of about 300km2

the crustal structure of the east anatolian plateau turkey from receiver functions 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 2003gl018192 shtml http atlas geo cornell edu turkey publications zor et al 2003 htm

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

sedimentary evolution and environmental history of lake van turkey over the past 600 000 years the lithostratigraphic framework of lake van eastern turkey has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years the lithostratigraphy and chemostratigraphy of a 219 m long drill core from lake van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity an age model was established based on the climatostratigraphic alignment of chemical and lithological signatures validated by 40ar 39ar ages the drilled sequence consists of ca 76 lacustrine carbonaceous clayey silt ca 2 fluvial deposits ca 17 volcaniclastic deposits and 5 gaps six lacustrine lithotypes were separated from the fluvial and event deposits such as volcaniclastics ca 300 layers and graded beds ca 375 layers and their depositional environments are documented these lithotypes are i graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations ii varved clayey silts reflecting strong seasonality and an intralake oxic anoxic boundary for example lake level highstands during interglacials interstadials iii caco3 rich banded sediments which are representative of a lowering of the oxic anoxic boundary for example lake level decreases during glacial inceptions iv caco3 poor banded and mottled clayey silts reflecting an oxic anoxic boundary close to the sediment water interface for example lake level lowstands during glacials stadials v diatomaceous muds were deposited during the early beginning of the lake as a fresh water system and vi fluvial sands and gravels indicating the initial flooding of the lake basin the recurrence of lithologies i to iv follows the past five glacial interglacial cycles a 20 m thick disturbed unit reflects an interval of major tectonic activity in lake van at ca 414 ka bp although local environmental processes such as tectonic and volcanic activity influenced sedimentation the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes making lake van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years

genesis of collision volcanism in eastern anatolia turkey late cenozoic volcanism in eastern anatolia extends in a broad sw ne trending belt across the arabia eurasia collision zone from the arabian foreland basin in the southwest and to the kars plateau and lesser caucasus in the northeast foreland volcanism is dominated by basaltic shield and fissure eruptions of transitional tholeiitic alkaline composition volcanism on the thickened crust north of the bitlis thrust zone varies from the mildly alkaline volcano nemrut and older mus volcanics in the south through the transitional calc alkaline alkaline volcanoes bingol and suphan and the alkaline volcano tendurek to the calc alkaline volcano ararat and older kars plateau volcanics in the north isotope sr nd and trace element systematics indicate that the lavas from the foreland were derived from the mantle lithosphere of the arabian continent which had been enriched by small volumes of asthenospheric melts over a period of time and that lavas from the alkaline volcanic area around mus and the volcanoes nemrut and tendurek north of the bitlis thrust zone were derived from a lithospheric source of similar composition either from the same underthrust arabian continent or from the bitlis massif microcontinent by contrast the transitional lavas from bingol and suphan and the calc alkaline lavas from ararat and kars were derived from lithosphere carrying a distinct subduction signature inherited from pre collision subduction events positive correlations between 87sr 86sr and sio2 and rb nb and sio2 in the alkaline and transitional lavas suggest that combined assimilation and fractional crystallization was an important process within at least part of the thickened crust of the collision zone trace element covariation diagrams such as y rb indicate the importance of hornblende crystallization at depth and orthopyroxene at shallow levels within the calc alkaline provinces in contrast to the consistently anhydrous crystallization sequences of the alkaline lavas trace element diagrams based on the covariation of compatible and incompatible elements point to moderate low degrees of partial melting with residual clinopyroxene throughout and residual garnet in the foreland province consideration of mineral stabilities mantle solidi and geothermal gradients before and after collision suggest that lithospheric thickening should both increase the thickness of metasomatized lithosphere and depress the metasomatized zone to greater depths probably beneath the amphibole and dolomite breakdown curves perturbation of the thickened lithosphere by delamination of the thermal boundary layer perhaps coupled with local stretching associated with pull apart basins on strike slip fault systems is then sufficient to generate melt the composition of that melt being largely dependent on the enrichment history of the lithosphere in question in eastern anatolia volcanism appears to have started between about 8 and 6 ma ago some 5 ma after the start of rapid uplift of the east anatolian plateau

nw iran eastern turkey present day kinematics results from the iranian permanent gps network abstract a network of continuous gps stations has been installed in nw iran since 2005 to complement the survey gps network already existing in the region we present the 1999 2009 gps derived velocity field for this region based on the continuous and survey mode observations the results confirm a right lateral slip of 7 1 mm yr for the north tabriz fault in agreement with previous studies this rate is consistent with earthquakes of magnitude 7 7 3 and recurrence times of 250 300 yr the higher spatial coverage of the new network shows that deformation is localized in the vicinity of the chalderan south gailatu siah cheshmeh khoy fault and the north tabriz fault however the eastern end of the north tabriz fault appears to cross mount bozgush rather than following its southern foothills this new velocity field does not indicate the 8 mm yr of nne ssw extension suggested earlier for the region but rather shows lower extension of 1 2 1 mm yr across the eastern segment of the north tabriz fault and the talesh to the west the chalderan and the western north tabriz fault segment act like pure strike slip faults without significant extension or compression the denser network in the rudbar earthquake region ms 7 3 1992 shows no significant motion across the fault suggesting that the recurrence time of earthquakes like the rudbar event must be very long the lack of substantial compressive strain and the sharp azimuth change of the velocity vectors in the transition zone from arabia to lesser caucasus motion imply that processes other than extrusion possibly related to old subduction or delamination contribute to active deformation

variational assimilation of xbt data part 1 abstract a variations method based on the adjoint equation technique is used to assimilate data in a relatively simple linear reduced gravity model of the tropical pacific real xbt data are used by identifying the depth of the 16 c isotherm depth with the model layer depth it is shown that the xbt data contain large scale information that corrects the model first guess however the model is not capable of fitting the data in the eastern pacific for the whole assimilation period regions not seeded by the data are explicitly shown and the impact of data from different times on the initial state is also discussed

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

active tectonics of the turkish iranian plateau 1 this paper examines how active faulting in the turkey iran caucasus region accommodates the arabia eurasia collision and the velocity field observed by gps the overall shortening across the zone is in general spatially separated partitioned into right lateral strike slip in the turkish iranian plateau and thrusting in the greater caucasus a band of counterclockwise rotating nw se right lateral strike slip faults accommodates a nw se gradient in ne directed velocity relative to eurasia between the black and caspian seas a nnw sse band of previously unrecognized oblique normal faults is present on the turkey iran border we estimate the offsets on faults from geomorphological features and show that these offsets can be achieved in 5 2 ma at present rates this implies a reorganization of deformation in the collision zone at that time after the initial collision at 12 ma probably in response to mantle induced dynamic uplift

upper mantle discontinuity structure beneath east anatolian plateau turkey from receiver functions abstract imaging of seismic velocity discontinuities with receiver functions suggests a complex mantle structure beneath the east anatolian plateau by stacking all the receiver functions as a function of ray parameter we examined the moveout characteristics of the data set and tested different velocity models to fit the arrival times of converted phases from the moho and the lithosphere asthenosphere boundary and their multiples the best fitting model shows anomalously thin crust 40 km and lithosphere 65 km and low uppermost mantle velocities causing systematic delays on later discontinuity arrivals these findings are consistent with the high plateau supported by partially molten and buoyant asthenosphere the upper mantle discontinuities are all visible in different frequencies 0 15 and 0 4 hz especially the 410 km discontinuity does not show frequency dependence in amplitude and suggests a sharpness of 10 km or less spatial variations of the 410 and 660 km discontinuities reveal anticorrelated topography and distinct zones of diminished amplitude associated with a detached slab and delaminated fragments of lithospheric mantle in the south the slab becomes deeper and horizontally deflected towards the east suggesting westward migration of slab detachment and resistance to slab penetration at the 660 km discontinuity in the north the mantle transition zone is characterized by two spatially limited lithospheric fragments with complex geometry at the center of the study area the transition zone is thin 230 km suggesting excess temperature of 120 c this warm mantle anomaly most likely is due to hot material trapped within the upper mantle between slab in the south and delaminated fragments in the north

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