slip motion estimation along the ovacik fault near erzincan turkey using ers 1 radar image evidence of important deformation inside the turkish plate abstract a synthetic aperture radar ers 1 scene used to complement a landsat tm scene allows better understanding of the structure of the active ovacik fault southwest of erzincan turkey the radar image shows that the ovacik fault is interrupted at its crossing point with the kemaliye fault recent compressive displacements have reactivated the kemaliye fault while a pull apart basin has been generated along the ovacik fault estimates of offsets of major rivers and analysis of the complex fault geometry given an estimated left lateral strike slip displacement of 12 5 20 km along the ovacik fault for the last 13 ma which is similar to the rate of movement along the east anatolian fault located in the east and forming the boundary of the turkish plate

fishes and palaeogeography of the african drainage basins relationships between chad and neighbouring basins throughout the mio pliocene article i nfo keywords miocene pliocene palaeobiogeography africa the neogene african fossil record of two fishes i e semlikiichthys perciformes indet and calarius siluriformes ariidae is reviewed including new material from chadian outcrops their distribution confirms the existence of a nilo sudan ichthyological province during an early part of the miocene an east west waterway is demonstrated to have crossed africa allopatric speciation in the chadian and east african areas suggests that a split occurred in this system prior to 7 ma moreover our data support the existence of hydrographical connections between the chadian basin and the syrte basin after 7 ma at about the mio pliocene boundary finally our study also demonstrates that connections between the niger and chad basins

mechanical significance of structural patterns identified by remote sensing studies a multiscale analysis of tectonic structures in crimea abstract based on remote sensing analyses of two panchromatic spot scenes that cover the western and eastern parts of crimea completed with the study of landsat thematic mapper scenes and local aerial photographs we determined the geometry of major structures folds and fractures the strikes of large fractures are quite homogeneous in the studied area three important sets are common n10 ne sw and nw se two strikes are particularly developed in the western part of crimea n25 and n105 along important faults we recognised the sense of motion which often corresponds to the latest or to the major stages of movement we also determined stress tensors by inversion of microtectonic data sets collected in the field combining remote sensing analysis with mechanical studies provides new views on the structural evolution of crimea we thus characterised major tectonic events responsible for most of the deformation in eastern crimea the structural patterns fit well with two major tectonic events 1 the latest one is a plio quaternary faulting event normal slip along n10 faults and strike slip motion along n10 and nw se faults corresponding to a transtensional regime with 3 trending e w 2 large fractures nw se and ne sw sets and fold and thrust development reveal a transpressional regime with 1 trending nne ssw during the berriasian in western crimea we characterised a more complex pattern of four major tectonic events 1 the plio quaternary tectonic phase induced left lateral displacement along nw se faults and normal slip along wsw ene faults and this deformation is in agreement with the strike slip regime that we reconstructed with 3 trending nne ssw 2 as for eastern crimea the berriasian phase was well expressed with folds thrusts and strike slip faults under a transpressional regime with 1 trending n s to nnw sse the two other events well identified in western crimea are 3 a n s directed extension that developed large n105 faults and 4 a nw se directed extension involving ne sw normal faults that we relate to the development of peripheral troughs in the oligocene western crimea suffered a more complicated structural evolution than eastern crimea from eastern to western crimea we also noticed the systematic deviation in the trends of the principal stress axes of the recent stress field and in the berriasian stress field as well these differences may be related to the presence of a major crustal discontinuity the transverse alushta simferopol fault

near surface imaging of a buried foundation in the western desert egypt using space borne and ground penetrating radar alos palsar l band full polarimetric data have been used to detect and characterize a well defined geometric target hidden under sand deposits in the western desert of egypt this buried object is rectangular in shape with very straight boundaries and encloses an area of 500 m2 inside the rectangular area there is a perfectly circular feature of approximately 53 m2 area high and medium resolution optical satellite images worldview 2 alos avnir 2 and field investigation confirm that the topography of the study area is relatively flat and completely covered by dry sand the electromagnetic wave scattering behavior of the detected buried object was measured by decomposing the scattering matrix of alos palsar full polarimetric data into entropy alpha h and freeman and durden decompositions furthermore a combination of unsupervised classification algorithms and constant false alarm rate cfar edge detection was performed on the polarimetric data which revealed a well defined geometric shape with straight borders these borders have high angles with low entropy which physically means double bounce scattering mechanism with low randomness and is very similar to that of an urban scatterer indicating that the detected target might be a buried wall like foundation of a man made structure moreover 28 ground penetrating radar gpr profiles were acquired using a 270 mhz shielded antenna to validate the satellite radar remote sensing results the gpr profiles reveal very clear hyperbolic shapes at 1 5 m depth with one of them showing a large hyperbolic shape like structure which might indicate the presence of a buried foundation thus the site might have significance to archaeological studies of the western desert particularly previous human occupation and the sources of water for such habitation

mapping of a major paleodrainage system in eastern libya using orbital imaging radar the kufrah river paillou p schuster m tooth s farr t rosenqvist a lopez s malezieux j m 2009 mapping of a major paleodrainage system in eastern libya using orbital imaging radar the kufrah river earth and planetary science letters 277 3 4 327 333 sponsorship french space agency cnes centre national d etudes spatiales

the use of multifrequency and polarimetric sir c x sar data in geologic studies of bir safsaf egypt abstract bir safsaf within the hyperarid core of the sahara in the western desert of egypt was recognized following the sir a and sir b missions in the 1980s as one of the key localities in northeast africa where penetration of dry sand by radar signals delineates previously unknown sand buried paleodrainage valleys radar rivers of middle tertiary to quaternary age the bir safsaf area was targeted as a focal point for further research in sand penetration and geologic mapping using the multifrequency and polarimetric sir c x sar sensors analysis of the sir c x sar data from bir safsaf provides important new information on the roles of multiple sar frequency and polarimetry in portraying specific types of geologic units materials and structures mostly hidden from view on the ground and on landsat tm images by a relatively thin but extensive blanket of blow sand basement rock units granitoids and gneisses and the fractures associated with them at bir safsaf are shown here for the first time to be clearly delineated using c and l band sar images the detectability of most geologic features is dependent primarily on radar frequency as shown for wind erosion patterns in bedrock at x band 3 cm wavelength and for geologic units and sand and clay filled fractures in weathered crystalline basement rocks at c band 6 cm and l band 24 cm by contrast quaternary paleodrainage channels are detectable at all three radar frequencies owing among other things to an usually thin cover of blow sand the sir c x sar data investigated to date enable us to make specific recommendations about the utility of certain radar sensor configurations for geologic and paleoenvironmental reconnaissance in desert regions

shuttle imaging radar experiment the shuttle imaging radar sir a acquired images of a variety of the earth s geologic areas covering about 10 million square kilometers structural and geomorphic features such as faults folds outcrops and dunes are clearly visible in both tropical and arid regions the combination of sir a and seasat images provides additional information about the surface physical properties topography and roughness ocean features were also observed including large internal waves in the andaman sea

neotectonics in the eastern north anatolian fault region turkey advocates crustal extension mapping from sar ers imagery and digital elevation model abstract this paper concerns the neotectonics of the eastern part of the anatolian block bounded respectively to the north and the east by the north anatolian naf and the east anatolian faults eaf meeting at karliova the study is based on imagery of synthetic aperture radar sar scenes acquired by the european remote sensing ers satellite and on views of a digital elevation model dem complemented with fault analysis in the field we show that extensional tectonics associated with transcurrent displacements prevail in the karliova triangle and beyond new local releasing bends or pull apart basins and push up structures along the naf have been demonstrated more importantly anatolia is composed of blocks less than 50 km in width that are tilted and move relative to each other they are compatible with a detachment within the crust of anatolia we argue that an escape wedge has migrated through time from west to east with successive jumps to form the present day karliova triangle at each stage the escape wedge was easterly bounded by a ne sw striking fault zone similar to the eaf in each escape wedge clockwise block rotations predate strike slip tectonics along the n110 e striking naf this is the case for instance for the erzincan basin where the first movements were parallel to the sw striking ovacik fault an early equivalent of the eaf and turned later to the west the detached crustal blocks moved southwestward then westward and extended at the same time in order to occupy the increasing surface within the successive escape wedges this is not the behaviour of simple lateral extrusion of the anatolian lithospheric block induced by forces applied at its boundaries by the adjacent plates but rather that of detached crustal blocks submitted to extension as a consequence of backward retreat of the hellenic slab and buoyancy forces arising from crustal thickness differences

subsurface imaging in south central egypt using low frequency radar bir safsaf revisited we present the capabilities of low frequency radar systems to sound the subsurface for a site located in south central egypt the bir safsaf region this site was already intensively studied since the sir a and sir b orbital radars revealed buried paleodrainage channels our approach is based on the coupling between two complementary radar techniques the orbital synthetic aperture radar sar in c and l bands 5 3 and 1 25 ghz for imaging large scale subsurface structures and the ground penetrating radar gpr at 500 and 900 mhz for sounding the soil at a local scale we show that the total backscattered power computed from l band sar and 900 mhz gpr profiles can be correlated and we combined both data to derive the geological structure of the subsurface gpr data provide information on the geometry of the buried scatterers and layers while the analysis of polarimetric sar data provides information on the distribution of rocks in the sedimentary layers and at the interface between these layers the analysis of 500 mhz gpr data revealed some deeper structures that should be detected by lower frequency sars such as a p band system

hidden calderas evidenced by multisource geophysical data example of cappadocian calderas central anatolia abstract the cappadocian volcanic field in central anatolia turkey is characterised by a sequence of 10 neogene ignimbrites the associated calderas have been partly dismantled and buried by subsequent tectonic and sedimentary processes and therefore cannot be readily recognized in the field recent progress in the understanding of the stratigraphic correlations and flow patterns has identified two main probable source areas for the ignimbrites detailed study of these areas based on gravity surveys remote sensing data spot and ers1 images and digital elevation models dem has provided evidence for two major caldera complexes and their relationship to old stratovolcanoes and neogene tectonics the older nevsehir acigol caldera complex located between the towns of acigol nevsehir and cardak is inferred to be the source of the kavak and zelve ignimbrites the nevsehir acigol caldera complex is defined mainly by a 35 mgal circular gravimetry anomaly about 15 km in diameter the boundaries of this now buried caldera complex are shown by high gradients on the bouguer gravity anomaly map the younger derinkuyu caldera complex located between the erdas stratovolcano and the ciftlik basin is inferred to be the source of the sarimaden cemilkoy gordeles and kizilkaya ignimbrites it is well defined by a rectangular 35 23 km gravity low 30 mgal with a positive high 20 mgal in the center gravity remote sensing data and the dem provide evidence that the erdas stratovolcano on the northern margin of the derinkuyu caldera complex represents the remnants of a large stratovolcano partly cut by one or more caldera collapses the positive anomaly within the derinkuyu caldera complex is centered on the 15 km wide sahin kalesi volcanic massif field evidence and structural features inferred from the dem and remote sensing data strongly suggest that this massif is a resurgent doming associated with the gordeles ignimbrite eruption high resolution ers1 spot and dem images reveal that the transtensive regime active at least since the miocene influenced the location of eruptive centers and caldera complexes in cappadocia the two caldera complexes are located in transtensive grabens the subsidence of these grabens continuing after the caldera collapse events most likely resulted in the burying of the calderas and could explain the difficulties in identifying them in the field

late cenozoic tectonics and stratigraphy of northwestern anatolia the effects of the north anatolian fault to the region in northwest anatolia there is a mosaic of different morpho tectonic fragments within the western part of the right lateral strike slip north anatolian fault naf zone these were developed from compressional and extensional tectonic regimes during the paleo and neo tectonic periods of turkish orogenic history a ne sw trending left lateral strike slip fault system adapazari karasu fault extends through the northern part of the sakarya river valley and began to develop within a n s compressional tectonic regime which involved all of northern anatolia during middle eocene to early middle miocene times since the end of middle miocene times this fault system forms a border between a compressional tectonic regime in the eastern area eastwards from the northern part of the sakarya river valley and an extensional tectonic regime in the marmara region to the west the extension caused the development of basins and ridges and the incursions of the mediterranean sea into the site of the future sea of marmara since late miocene times following the initiation in late middle miocene times and the eastward propagation of extension along the western part of the naf a block north anatolian block began to form in the northern anatolia region since the end of pliocene times the adapazari karasu fault constitutes the western boundary of this block which is bounded by the naf in the south the northeast anatolian fault in the east and the south black sea thrust fault in the north the northeastward movement of the north anatolian block caused the formation of a marine connection between the black sea and the aegean mediterranean sea during the pleistocene

subsurface valleys and geoarcheology of the eastern sahara revealed by shuttle radar the shuttle imaging radar sir a carried on the space shuttle columbia in november 1981 penetrated the extremely dry selima sand sheet dunes and drift sand of the eastern sahara revealing previously unknown buried valleys geologic structures and possible stone age occupation sites radar responses from bedrock and gravel surfaces beneath windblown sand several centimeters to possibly meters thick delineate sand and alluvium filled valleys some nearly as wide as the nile valley and perhaps as old as middle tertiary the now vanished major river systems that carved these large valleys probably accomplished most of the erosional stripping of this extraordinarily flat hyperarid region underfit and incised dry wadis many superimposed on the large valleys represent erosion by intermittent running water probably during quaternary pluvials stone age artifacts associated with soils in the alluvium suggest that areas near the wadis may have been sites of early human occupation the presence of old drainage networks beneath the sand sheet provides a geologic explanation for the locations of many playas and present day oases which have been centers of episodic human habitation radar penetration of dry sand and soils varies with the wavelength of the incident signals 24 centimeters for the sir a system incidence angle and the electrical properties of the materials which are largely determined by moisture content the calculated depth of radar penetration of dry sand and granules based on laboratory measurements of the electrical properties of samples from the selima sand sheet is at least 5 meters recent september 1982 field studies in egypt verified sir a signal penetration depths of at least 1 meter in the selima sand sheet and in drift sand and 2 or more meters in sand dunes

detection of sand covered geologic features in the arabian peninsula using sir c x sar data eolian sand covers a large part of the arabian peninsula the flow of eolian sand is ongoing and sand covers bedrock as well as fluvial features of the peninsula consequently there is a gap in the understanding of the geological processes shaping the region the extensive coverage of shuttle imaging radar sir c x sar data over the arabian peninsula has provided a new means of mapping sand obscured features the preliminary interpretation of the data has identified several sites where l band reveals sand covered geological structures and drainage channels that are not shown on published maps and are not traceable with more conventional methods the indications are that these radar data may lead to improving the geological and fluvial geomorphic understanding of the region

impact of the geomorphology and soil management on the development of waterlogging in closed drainage basins of egypt and saudi arabia this paper investigates the interplay of the catchment geomorphology hydrology and soil properties on the development of waterlogging and land degradation within different dry land catchments in egypt and saudi arabia multi temporal remote sensing data of the landsat thematic mapper and enhanced thematic mapper were collected and processed to detect the land cover changes and development of cultivations within the two areas the shuttle radar topography mission digital elevation model were hydrologically processed to delineate the catchment morphometrical parameters and to examine the spatial distribution of cultivated fields and their relation to the extracted drainage networks the fluvial channels of the farafra oasis have largely been obliterated by the prevailing aridity and often buried under aeolian deposits the soil of these areas are mainly lithic with a high calcium carbonate content thus limiting the downward percolation of excess irrigation water and therefore develop perched water table and seepage through the buried fluvial channels on the other hand the cultivations of tabuk catchment which has similar geomorphologic setting to the farafra oasis have shown no signs for waterlogging this situation is could be related to the different soil properties the spatial distribution of cultivated areas and the adopted irrigation methods via pivots the inactive alluvial channels landforms and irrigation methods have to be considered when planning for a new cultivation in dry land catchments to better control waterlogging hazard the dry drainage concept can be implemented as the drainage and seepage water which can be conveyed into certain abandoned playas for evaporation

complex evolution of the erzincan basin eastern turkey abstract two new tectonic models are presented to explain the pull apart opening of the erzincan basin our field studies indicated that the erzincan basin is not a typical rhombic pull apart basin instead it has a rather complex single or two stage pull apart opening mechanism the basin was initially formed as a result of a 4 km wide releasing stepover and a 15 divergence angle between segments 1 and 2 of the north anatolian fault zone nafz along which the westward tectonic escape of the anatolian block has been taking place the single stage model refers to the partitioning of the transtensional deformation by coeval normal and strike slip displacements on parallel trending faults which remained since their initiation the two stage model infers that the basin opening was modified later by the formation of the left lateral ovacik fault which caused fragmentation of the anatolian block the two stage pull apart basin opening mechanism accounts for the observed geometry of the erzincan basin the present day geometry of the basin indicates that there had been 35 5 km of right lateral displacement along the nafz and 5 2 km of left lateral displacement along the ovacik fault

morphologic evidence of active motion of the zambapala fault gulf of guayaquil ecuador abstract the zambapala fault zone zfz is located at the link between the offshore structures of the gulf of guayaquil and the guayaquil caracas megashear gcm that accommodates the northeastward motion of the north andean block we use morphological observations of drainage offset to assess the active motion of the zambapala fault the relation between the horizontal offset amount d of the stream channel and the upstream length l from the offset segment and offset of beach morphology provide a measurement of the average slip rate of the motion of the fault to an accuracy of a fraction of millimeters per year the drainage network is short running down the southeastern slopes of the zambapala cordillera 297 m a quaternary dome uplifted along a positive flower structure we measure the d drainage offset along the fault l drainage length from the fault relation for the upper and more recent part of the drainage network the relation suggests that the fault is active at present capture occurs along the middle slopes and channel straightening near the littoral plain hiding part or most of the fault offset the fault trace crosses the littoral plain showing 35 40 m offset of the inner beach ridge and delimiting variations of the beach morphology the attribution of a maximum age of 5000 6000 years to the oldest beach ridge the postglacial transgression allows us to calculate a minimal mean slip rate of 5 8 8 mm year 1 this result confirms that the guayaquil caracas megashear extends to the gulf of guayaquil through the zambapala fault zone which accommodate at least 60 80 of the slip motion of the guayaquil carcas megashear

emplacement of volcanic vents and geodynamics of central anatolia turkey abstract observations on synthetic aperture radar sar scenes of the european remote sensing ers satellite and digital elevation models dems complemented by field structural analysis permit a new understanding of relationships between tectonics and volcanism since the late miocene 10 ma in central anatolia volcanic edifices form elongate stratovolcanoes linear clusters and volcanic ridges they indicate emplacement on tension fractures and tail crack or horsetail features for instance the kara dag volcano is rooted on a tail crack which accommodates a horizontal left lateral throw component at a fault termination caldera complexes of cappadocia are associated with horsetail fault patterns the emplacement of volcanoes also benefits from larger scale tectonic structures the erciyes dag volcano is localized by the sultan saz releasing bend which opens along the sinistral strike slip ecemis fault deformation has been analysed from tension fractures which are perpendicular to the direction of extension and from field structural analysis on a regional scale the tectonic regime responsible for the distribution of volcanic vents in this area of convergence and lateral extrusion is not compression but extension the central taurus range is the thermally uplifted shoulder of the adana cilicia basin which is related to lithosphere thinning westward movements in the northwestern part of the studied area are influenced by the active back arc aegean extension situated to the west farther to the south the direction of motion turns southwest and south under the influence of the opening of the adana cilicia basin we interpreted that extension in the central anatolian plateau is related to crustal blocks moving above sub horizontal detachment surfaces located in the lower crust this is based on several facts the tuz golu fault zone is a within crust detachment the tuz golu basin does not affect the whole lithosphere because otherwise it would have been bordered by thermally uplifted shoulders movements change trend within a small 50 km region

the role of intraplate strike slip faults in shaping the surrounding morphology the ovacik fault eastern turkey as a case study abstract although the westward extrusion of the anatolian block is mainly compensated along its boundary faults the north anatolian and the east anatolian shear zones it is internally deformed in a dominant manner by some strike slip faults as well to obtain a better understanding about this intraplate deformation of the anatolian block we investigate the tectonic geomorphology of the ovacik fault of which is the northeastern member of the malatya ovacik fault zone mofz further we apply the most common geomorphic indices such as the hypsometric curve and integral longitudinal channel profiles channel steepness and concavity mountain front sinuosity and valley height width ratio to characterise and quantify the deformation along the of and the surrounding region where the regional morphology is shaped with the joint effect of palaeo and neotectonics and other morphological factors such as palaeoglacial processes the highest hypsometric integral steepness and concavity values are generally observed along the northeastern strand of the of the munzur mountains and the kemaliye region further we interpret that high hi and steepness values indicate a regional tectonic uplift because of either a change in fault geometry which gives rise to the vertical component on the of or a regional high convergence zone furthermore this study gives the first calculation of vertical uplift in the northern margin of the ovacik basin ob as at least 0 5 mm y for long term deformation history thus our results exhibit that the of is one of the intraplate strike slip faults of the anatolian block

the role of fracture zones during early red sea rifting structural analysis using space shuttle radar and landsat imagery the structural pattern of the red sea region an area where continental lithosphere is cut by a young oceanic rift was studied by means of satellite and space shuttle radar imagery the space shuttle mission 2 made two passes over the red sea bracketing a region transitional between the southern red sea where true seafloor spreading started about 5 ma bp and the northern red sea where crust is probably continental though thinned and stretched structures on these passes define bands of shearing in the african and arabian margins parallel to the dead sea fracture zone 000 020 combinations of these data with landsat information reveal four shear bands along the margins of the red sea and one oblique to the gulf of suez we have named the northern three red sea shear zones detected on the sir a data the brothers dead sea fracture zone the zabargad fracture zone and the shagara fracture zone two sets of normal faults were also detected trending 330 340 parallel to the northern red sea coastline and 310 320 parallel to the axial deeps in the red sea a map of the 310 320 faults bordering the red sea resembles a v shaped wedge narrowing to the north near the gulf of suez these faults may have formed as a result of the most recent push of seafloor spreading if this is so then there may be a propagating tectonic wedge moving from south to north which thins the continental crust up to distances of 300 km from the axis of spreading following continental deformation oceanic crust may be emplaced in 9hot points9 along the rift axis these 9punctiform9 oceanic spreading centres should propagate in the same direction as continental rifting during this episode palaeo shear zones probably act as barriers 9locked zones9 to the axial propagation one such case is at the zabargad fracture zone where the oblique impact of the propagating rift against the palaeo shear may have placed the red sea9s western side under compression and uplift while the eastern side may have been subject to oblique extension with the formation of pull apart basins the space shuttle imagery allows integration of some of the northern red sea morphotectonic features with structures on the continent

sand sheet dynamics and quaternary landscape evolution of the selima sand sheet southern egypt abstract the selima sand sheet occupies more than 120 000 km 2 of the hyperarid uninhabited darb el arba in desert centered at the border of egypt and sudan at latitude 22 n and is characterized by a featureless surface of lag granules and fine sand broken only by widely separated dune fields and giant ripples of varying height and wavelength monitoring of the largest of these chevron shaped ripples using repeat orbital images and field surveys indicates migration rates of 500 1000 m yr accompanied by 0 2 0 cm erosion or deposition of the youngest sand sheet stratigraphic units beneath this active surface several developmental stages of sand sheet sediments have undulatory upper contacts and varying degrees of pedogenic alteration the younger stages retain their horizontal lamination and have cracking patterns indicative of past wetter conditions while older stages have lost their laminar structure through pedogenesis historical remains in the desert as well as 14 c and uranium series dating indicate that the younger strata of the sand sheet have a very low accumulation rate despite the active movement of the surface the lower strata were extensively modified during mid and late pleistocene pluvials resulting in an initial undulatory surface that set the stage for later accumulation of sand sheet below these quaternary sediments lies irregular topography dissected by channels of mid tertiary drainage the selima sand sheet is neither the result of net aggradation nor degradation but results from inheritance of an initial fluvial landscape increasingly modified during climatic cycles wet periods led to local drainage and deposition while the increasingly severe arid periods of the late pleistocene and holocene resulted in deposition of the blanketing bimodal sediments of the sand sheet

time and the rivers flowing fluvial geomorphology since 1960 fluvial geomorphology has been the largest single subdiscipline within geomorphology for many decades fluvial geomorphic expertise is integral to understanding and managing rivers and to developing strategies for sustainable development this paper provides an overview of some of the significant advances in fluvial geomorphology between 1960 and 2010 with respect to conceptual models fluvial features and environments being studied tools used by fluvial geomorphologists geomorphic specialty groups within professional societies journals in which fluvial geomorphic research is published and textbooks of fluvial geomorphology during this half century fluvial geomorphology broadened considerably in scope from a focus primarily on physical principles underlying process and form in lower gradient channels with limited grain size range to a more integrative view of rivers as ecosystems with nonlinear behavior and great diversity of gradient substrate composition and grain size the array of tools for making basic observations analyzing data and disseminating research results also expanded considerably during this period as did the diversity of the fluvial geomorphic community

three dimensional vp and vp vs structure of the upper crust in the erzincan basin eastern turkey 1 using aftershocks of the 13 march 1992 erzincan earthquake ms 6 8 three dimensional vp and vp vs velocity structure of the erzincan basin and its surroundings were modeled by local earthquake tomography travel times of body waves belonging to 1025 selected high quality events recorded by 58 temporary stations were inverted iteratively and simultaneously by using the simul2000 algorithm synthetic and resolution tests were performed to analyze the sensitivity of tomographic results and model parameterization the resulting 3 d vp and vp vs tomographic images show velocity anomalies related to geologic and tectonic structures beneath the erzincan basin while low vp anomalies down to 2 3 km depths are associated to thick neogene sediments deposited in the erzincan basin high vp anomalies indicate bed rocks and intrusive magmatic rocks beneath the mountain ranges vp vs anomalies are an important indicator of local tectonic structures and the physical mechanical and compositional variations in the rocks the low vp vs anomalies 1 7 observed at shallow depths 0 4 km track the main fault systems and thus the weakness zones in the basin the high vp vs anomalies 1 9 located between 4 and 6 km depth in the southeast of the erzincan basin may correspond to fluid saturation high pore pressure and carbonate content in the rock matrix the high vp vs ratios play an important role for increasing seismicity in this area because of the fluid saturation and the high pore pressure finally on the basis of the 3 d tomographic images basement of the erzincan basin deepens down to about 10 km depth and possesses an irregular and asymmetric shape the thick and unconsolidated sedimentary layer increases seismic risk to erzincan and other cities located on the basin as it magnifies ground motion caused by large earthquakes

bagnold s barchan a 57 yr record of dune movement in the eastern sahara and implications for dune origin and paleoclimate since neolithic times abstract discovery in 1980 of camp 18 of the 1930 bagnold expedition in northwestern sudan has resulted in an exceptionally long record of barchan movement from which an average rate of 7 5 m yr has been calculated measurements of the rate of dune advance since 1980 have not varied significantly indicating a state of quasiequilibrium exists the dune field is moving over an undulating sand sheet exhibiting various stages of holocene pedogenesis and containing neolithic sites the sand sheet overlies pleistocene alluvium with stronger stages of pedogenesis all of these deposits may be a significant source of dune sand wind blown grass fragments trapped by advancing slipfaces mark former slipface positions and indicate late holocene rainfall events which can be radiocarbon dated parabolic forms revealed by spot images at the windward ends of the dune fields are transitional to barchans suggesting sand accumulation in vegetation germinated during a holocene wet period in addition sand streaks from sand sheet undulations suggest that active eolian erosion of sand sheets contributes to the sand supply of dune fields pedogenesis during pluvial periods contributes to silt and clay fractions of bimodal sand sheet sediments from wind streaks on landsat images and an estimated average rate of dune advance positions of dune fields during past hyperarid periods can be estimated

river patterns and their meaning abstract rivers are largely responsible for shaping the earth s continental landscapes river patterns the spatial arrangements of channels in the landscape are determined by slope and structure at site and sector scale channel morphology varies spatially and in time but river patterns and drainage texture or the frequency of stream lines per unit area together determine the intricacy or otherwise of topography most river patterns evolve through natural selection slope induces the formation of such patterns as parallel radial and distributary while structure produces straight angular trellis and annular arrangements once established patterns tend to persist nevertheless at many sites the usual patterns have been disturbed and patterns that are anomalous in terms of slope and structure have been produced by diversion tectonism volcanism glaciation mass movements and human activities by antecedence superimposition inheritance or underprinting by the persistence of deeply eroding rivers which encounter alien structures and by climatic change river patterns provide clues to underlying structure and to the chronology of events they have also proved significant in the search for minerals

alluvial fans as an effect of long term man landscape interactions and moist climatic conditions a case study from the glubczyce plateau sw poland abstract at the mouth of periodically drained valleys in the loess glubczyce plateau sw poland favorable conditions for deposition of alluvial fan sediments occur so these forms are very common in the investigated area the origin of the forms analyzed is related to long term human landscape interactions because deforestation and land use changes started in the neolithic ca 5 5 ka bc causing intensification of soil erosion processes willful and continuous interference by man into natural environment began at that time thus human impact is responsible for acceleration of runoff and mobilization of sediment which formed alluvial fans at the mouths of episodically drained valleys the objectives of this study are 1 to measure the morphological and topographical characteristics of the fans 2 to describe and analyze the inner structures of the alluvial fans analyzed and 3 to date the alluvial fan deposition the alluvial fans are mainly formed of silty clayey massive sediments the gravel sand layers occurring in two exposures indicate the incision of the valleys in the older pleistocene sediments underlying the loess upland deposits and intensive phases of erosion in the course of which coarser material could have been transported radiocarbon dating of the peat filling the bottoms of the valleys and underlying the mineral deposits of the fans indicates that sediment transfer from cultivated valley slopes and its deposition at the mouth of the valleys was recorded in alluvial fan sediments by the neolithic 6895 140 bp during this period erosion was probably intensified by a moister climate radiocarbon dating of organic layers which were discovered inside the sediments of two fans show that the youngest dated stage of intensified erosion took place in early medieval times when the glubczyce plateau was colonized again by slavs after the settlement depression during the migration period

relict drainages conical hills and the eolian veneer in southwest egypt applications to mars viking images indicate that no single process is sufficient to explain the origin and evolution of martian landforms landforms common to both earth and mars result from a complex interplay of geologic agents including water mass wasting wind and possibly ice the relict wadis of the gilf kebir plateau in southwest egypt strongly resemble fluvial channels on mars particularly those of the fretted terrain like the fretted channels on mars the egyptian wadis are dry flat floored and deeply incised in a plateau surface they have stubby theatre headed wide and deep tributaries that commonly join the trunk valleys at odd angles they apparently lack drainage basins and are separated by areas that appear on most of the available images to be undissected the wadis grade into adjacent low lying smooth plains mantled by eolian debris and dotted with myriads of conical and flat topped inselbergs that have obviously undergone mass wasting the unusual geomorphic characteristics of the gilf region are herein interpreted as the results of an extreme eolian and mass wasting overprint on a landscape originally carved by running water the relict networks of southwest egypt were initiated by streams that drained formerly extensive gilf highlands those highlands are inferred to have been a major tertiary watershed in north africa as quaternary dessication set in these rivers vanished and were replaced by ephemeral gullies cliff sapping wind abrasion and deflation have widened the gilf valleys and reduced many interfluves to clusters of flat topped and conical hills these now rise as inselbergs on the adjacent desert plains on which little evidence of former fluvial activity remains wind has deflated the surface and redistributed the finer particles from fluvial sediments and the debris of mass wasting into eolian sand sheets drifts and dunes dunes are migrating southward through the region along eolian thoroughfares that follow the apparent paths of ancient master streams toward distant basins of sand accumulation in the central sahara the fluvial and mass wasting origin of the particles in the eolian deposits the segregation of these materials according to grain size and the migration of those particles capable of saltation to areas of accumulation in lowland basins of the sahara are suggested as analogs for the formation and accumulation of sand sheets and dunes on the northern plains and in the polar erg on mars outliers of the martian plateau in the fretted terrain appear to have been dissected at least initially by channels whose upstream portions are incised in the uplands the martian wadis have many geomorphic peculiarities similar to those of the gilf wadis and like the egyptian features they have been attributed to mass wasting although basal sapping and removal of debris by wind have almost certainly modified the martian features their deep incision in the plateau and their inferred northward extensions on the northern plains seem to require not only initial downcutting by fairly energetic streams but also prolonged and long distance flow of water on mars as in southwest egypt running water is now nonexistent as suggested by milton 1973 the northern plains may be the most extensive of the landforms produced during a fluvial stage of martian history inferred integrated stream networks in the fretted terrain on mars as in the gilf plateau may be relics of earlier less arid climatic intervals when runoff collected and flowed with sufficient power to carve valleys in bedrock in this interpretation the uplands might once have stood as a watershed on a much less arid mars

spaceborne and airborne imaging radar observations of sand dunes seasat and aircraft radar imagery of five areas of sand dunes in the southwestern united states and northwestern mexico have been studied and compared to landsat imagery and air photos radar imaging system parameters included two wavelengths 23 5 cm and 3 0 cm and incidence angles ranging from 0 through 70 horizontal polarization was used on both transmit and receive for all radar imagery resolution ranged from 12 m for the best aircraft imagery to about 40 m for seasat sand dunes studied behave as smooth surfaces for both 23 5 cm and 3 0 cm wavelength radars and the reflection of the radar energy from the dunes is specular measured surface irregularities of sand dunes are inadequate to cause either bragg or incoherent scattering of the incident radar beam in the 3 0 to 23 5 cm wavelength region this results in dunes that appear dark when imaged at incidence angles greater than the angle of repose because none of the dune faces are oriented properly normal to the incident radar beam to give a specular return to the antenna a scattering model based on specular return from randomly oriented flat dune faces was used and experimentally verified using aircraft data imaging radar resolution must be adequate to define the changing distribution of dune faces that characterize the dune morphology linear dune features with interdune spacing of less than 3 4 resolution elements are not recognizable distributed dune types such as barchans or stars must be more than about 10 resolution elements in each direction to be defined on the imagery illumination direction of the radar beam is important directional dune features must be oriented within about 60 of perpendicular to the radar illumination direction in order to be imaged if such features have considerable topographic relief the direction of radar illumination is less important because directional trends in unexplored regions cannot be predicted availability of radar imagery from two directions greatly facilitates interpretation of dune morphology and hence conclusions about causative wind regimes

using full polarimetric sar data to characterize the surface sediments in desert areas a case study in el gallaba plain egypt abstract mapping and characterizing surface sediment of desert environments in terms of surface texture and grain sizes provide important information on the geomorphology and depositional history to assess their potential for economic development accurate maps of surface sediment are often not available at the desired scales using conventional field surveys optical and radar remote sensors are increasingly used as an alternative method for rapid delineation and classification of surface sediments however each sensor provides different levels of information and accuracy in this research work six datasets alos avnir 2 aster avnir 2 palsar aster palsar quad polarized alos palsar and quad polarized radarsat 2 were prepared to run unsupervised and supervised classifications to compare their accuracy for mapping surface sediment in the non vegetated el gallaba plain of the western desert of egypt particularly in terms of grain size and surface roughness the accuracy level of all classification outputs as well as the official geologic map in comparison with the reference field information is empirically evaluated using the standard accuracy assessment method confusion matrices the best overall accuracy and dataset is the supervised classification using the complex coherence matrix t3 of the full polarimetric radarsat 2 which is 96 43 with kappa coefficient of 0 929 therefore the zonal statistics method is applied between the final supervised classification map with its five classes and the generated entropy h alpha anisotropy a and the shuttle radar topography mission srtm to extract information regarding the polarimetric response as well as the elevation of each sediment class in addition the polarization signatures of these five classes are extracted in order to examine their scattering mechanism and to distinguish the differences between them in terms of differences in their surface roughness and grain sizes in addition the low frequency alos palsar data reveal a set of linear features that are hidden under windblown sand and are not visible in the field or in other datasets these hidden lineament features were confirmed in the field by a ground penetrating radar survey using 100 mhz shielded gssi antenna the gpr profiles show very clear discontinuities in the subsurface layers which are covered by a thin sand sheet furthermore the complicated depositional history of these surface sediments is proposed based on field work and remote sensing analyses consequently the results show that el gallaba plain has high potential for agricultural production using its groundwater resources

polyphased block tectonics along the north anatolian fault in the tosya basin area turkey abstract the tosya basin is located in the bending segment of the north anatolian fault naf in turkey we have obtained original observations on the neotectonics from sar ers images digital elevation model dem and field structural analysis regional neogene deformation is characterised by the occurrence of several basins that are superimposed in time and space they result from differently oriented movements since 12 ma including southwestward motion along a fault subparallel to the naf we propose a model of polyphased tectonics related to the displacement of several individualised blocks in the first stage tortonian the north tosya block has moved toward the n250 azimuth parallel to the dextral n70 striking segment of the naf as a consequence a triple junction related compatibility basin was opened at the intersection with a n60 to n30 striking fault this pattern is similar to the karliova corner where the naf and the east anatolian fault meet in the second stage early pliocene middle pleistocene a segment of the former n70 naf was abandoned and the naf propagated eastward to form a n90 striking segment n90 naf cutting the former tosya block and basin into two parts the north tosya block has moved again and this new geometry has permitted a south tosya block to move parallel to the naf but with a higher rate which has induced compression in the tosya basin in the third stage holocene the south tosya block moved toward n240 obliquely to any of the naf segments this has resulted in the formation of two holocene pull apart type basins along the previous n60 to n30 striking fault while extensional faults were formed in the south tosya block estimated dextral displacement along the naf is 5 9 to 8 5 km at this stage this model of blocks moving in different directions including holocene local movements toward n240 means that the naf can be considered not to be a simple transform fault our model implies that the n90 naf was non existent before the early pliocene

an integrated remote sensing and gis analysis of the kufrah paleoriver eastern sahara abstract a combined remote sensing optical and radar imagery and gis hydrologic network delineation analysis allows mapping of the kufrah paleoriver of libya and sheds light on its geomorphic evolution during the neogene the kufrah system which is now largely buried beneath the windblown sands of the eastern sahara drained an area of about 236 000 km 2 in central and southern libya the river discharged across a large inland delta to the al jaghbub depression in northern libya and ultimately through the sirt basin to the mediterranean sea radar imagery reveals buried features of the landscape including drainage divides locations of possible stream capture deeply incised valleys and the distal margins of the inland delta previous studies have shown that the kufrah paleoriver is the successor of the sahabi river which drained most of central libya during the late tertiary satellite imagery supports the concept of large scale drainage rearrangement in the quaternary driven by tectonic subsidence that diverted streamflow and sediment discharge away from the sahabi basin toward the inland delta of the lower kufrah basin paleochannels crossing the delta suggest that at various times during the quaternary the kufrah paleoriver either drained externally through the deeply incised sahabi paleochannel to the mediterranean sea or drained internally to paleolakes in the al jaghbub depression thick alluvial deposits on the delta and lake margins likely provided a major sediment source to build the great sand sea which covers the region today the southwestern branch of the kufrah drainage is aligned with an elongated trough that connects to the amatinga river system in chad thus the kufrah watershed may have served as an outlet from megalake chad to the mediterranean sea during humid phases of the neogene if so the combined amatinga kufrah system may have served as one of the proposed natural corridors used by human and animal populations to cross the sahara during the pleistocene these findings hold promise for modeling past lake levels and paleoclimates locating groundwater sources in the region and exploring for reservoirs of oil and natural gas in the region

use of radar data to unveil the paleolakes and the ancestral course of wadi el arish sinai peninsula egypt abstract aspects of the geomorphic evolution of wadi el arish the largest ephemeral drainage system in the sinai peninsula are still ambiguous and its paleochannels remain undefined one of the obstacles that impede recognition of these paleodrainage features is the variation in topography from past to present some of this variation is attributable to the post miocene tectonic activity in the region this activity might have continued to the present and led to developing an alternative course for the paleoriver the folded syrian arc belt in north sinai had a significant influence on the shape and direction of wadi el arish anticlinal ridges appear to have formed natural barriers that blocked the water flow across the main drainage course during humid periods and forced wadi el arish to deviate from its original course in this research we attempt to reconstruct the structural deformation and simulate the paleotopography to understand the evolution of the paleodrainage systems of the region the unique perspective offered by space borne radar data was used to define the structurally controlled paleolakes along wadi el arish and to trace its former course with a length of 109 km the former main channel course of wadi el arish was depicted west of gebel halal three major paleolakes were defined within structurally controlled depressions the largest lake occupied an area of at least 337 km 2 and contained approximately 10 7 km 3 of water when filled during pluvial phases the simulation of the paleotopography was confirmed by field observations and led to a concept for improved management of the renewable water resources in the study area thus a 2 km long canal with a depth of 6 m is recommended to be established within the structural uplift this canal would redirect the occasional runoff to a vast flat area west of gebel halal to provide water for approximately 1400 km 2 of fertile land for agricultural development the flow redirection would also help to mitigate the negative effects of flash floods in el arish city and maximize the harvesting of rain water that would otherwise be lost to the sea

a phase signature for detecting wet subsurface structures using polarimetric l band sar in this paper we investigate the ability of l band synthetic aperture radar sar systems to penetrate soils to retrieve information about subsurface wet structures our experiment site the pyla dune is a bare sandy area allowing high radar penetration and known to have large wet subsurface structures paleosoils at varying depths buried paleosoils which act as moisture tanks are detectable with radar since they present a high permittivity due to their water content by analyzing airborne polarimetric sar data we established that a phase signature is correlated to the buried wet palesoils a phase difference of 23 spl deg between the horizontal hh and vertical vv channels was clearly observed it allows detection of the paleosoil down to a larger depth 5 2 m than when only considering hh and hv amplitude signals 3 5 m in order to confirm this result field measurements were performed that led to the same observed phase difference we could fit our observations to the semiempirical model proposed by oh and sarabandi and we reproduced the observed phenomenon using a two layer integral equation method iem model of the pyla dune which was completed by finite difference time domain fdtd numerical simulations we show that the soil moisture significantly influences the radar response in terms of phase difference between the copolarized modes our study also shows that the single scattering iem model reproduces the observed phase difference fairly well for a natural outdoor site when combined to fdtd simulation results this phase signature could be used as a new tool to map subsurface moisture in arid regions

measurements of dielectric loss factors due to a martian dust analog 1 radar signals can penetrate loose sediments such as dust sand and alluvium to reveal buried geologic structures obscured in visible and infrared images in anticipation of data from instruments such as the marsis and sharad radar sounders and potential future imaging sar and rover mounted gpr instruments measurements have been made to characterize electrical loss factors of a martian dust analog and an iron rich soil this paper presents results from dielectric measurements of carbondale red clay crc and the palagonitic mars jsc 1 soil simulant from 0 2 to 1 3 ghz and from transmission measurements of radar penetration of crc up to 12 ghz attenuations predicted from dielectric measurements are compared to values measured in the experiment and are discussed relative to the frequencies at which imaging radars operate over the frequencies considered loss tangent tan decreases with increasing frequency but attenuation increases due to the influence of wavelength attenuation in crc ranges from 8 to 22 db m over p and l bands and jumps to 36 and 67 db m at c and x bands respectively mars jsc 1 has lower attenuation of 5 db m at p band and 12 db m at l band compared to attenuation measurements of sand both crc and mars jsc 1 cause significantly greater attenuation likely due to their compositions containing iron bearing minerals because martian fine sediments also contain ferric mineral components constraining higher losses of analogs for martian dust and fine sediments is important for predicting the performance of radar instruments operating in orbit or on the surface of mars

evidence for a large extended paleolake in the eastern sahara as revealed by spaceborne radar lab images recently processed radar images from the two flights of the space shuttle endeavour by the spaceborne imaging radar c x band synthetic aperture radar instrument in 1994 give a clear view of widely distributed sediments of a palaeolake in today s hyperarid eastern sahara nw sudan although a few of the sites of lacustrine sediments were previously examined in the field their extent now visible on the images yields a new perspective on the early to mid holocene wet phase that affected northern africa freshwater wetlands across an area exceeding 15 000 km2 existed between 8800 and 4500 b p owing to a significant increase in rainfall the phenomenon called the west nubian lake constitutes the largest scale hydrographic evidence in the eastern sahara for a northward shift of the tropical rain belt given that the region now receives less than 15 mm of precipitation per year on average the former open water body and its vegetated catchment may have acted as a modifier of the regional climate in connection with the detection of a buried major palaeodrainage system near kufra se libya the west nubian lake confirms the new multifrequency and multipolarization radar imaging as a powerful tool for the reconstruction of arid land palaeohydrology

late cenozoic tectonics and volcanism along the north anatolian fault new structural and geochemical data abstract different types of volcanic activity have developed along the north anatolian fault zone naf in turkey detailed analysis of satellite images and digital elevation models dems and field observations have been made in order to understand the tectonics and the distribution of volcanic vents in the anatolian block some faults are oblique to the naf and delimit extensional escape wedges vents rooted on open tension fractures show that emplacement of the volcanism is related to tensional fracturing of the anatolian continental block which we attribute to the onset of free borders in the south and west along the naf earliest extension 1 is directed s to ssw and the latest 2 towards w to wsw parallel to the sinistral slip along the naf major and trace element geochemical data indicate that the dominant calc alkaline rocks are associated with various alkaline lavas k ar ages of the volcanics range from 22 to 8 5 ma in galatia massif 900 to 100 ka in niksar and 3 to 12 ka in erzincan isotopic and trace element data are interpreted as reflecting a dominantly lithospheric mantle source slightly mixed with asthenospheric liquids most magmas were fractionated and contaminated by continental crust during their ascent 1 and 2 tectono volcanic events have propagated through time and space from west to east the 1 extension is late oligocene in the galatia massif late miocene in niksar and late pliocene in erzincan the 2 extension and strike slip event along the naf began in the late miocene in the galatia massif early pliocene in niksar and quaternary in erzincan signature from an asthenospheric source in the second event in the three regions suggests that an ancient suture zone galatia massif and or the lithospheric naf transform niksar and erzincan have served to channel small quantities of asthenospheric melts existing at the base of the lithosphere

great sand sea and selima sand sheet eastern sahara geochronology of desertification the relation of playa sediments and associated archeological sites with longitudinal dunes allows estimation of ages for the two uppermost strata of the great sand sea active dune formation corresponds with interpluvial periods of hyperaridity dune stability corresponds with semiarid pluvial periods archeological sites associated with truncated paleosols in the selima sand sheet suggest a similar climatic relation and indicate that the isohyets of central sudan shifted at least 400 kilometers northward during the peak of pluvials