large scale three dimensional gravity analysis of the lithosphere below the transition zone from western europe to the east european platform abstract large scale three dimensional gravity modelling using data averaged on a 1 grid has been carried out for the transition area from western europe to the east european craton the model consists of two regional layers of variable thickness the sedimentary cover and the crystalline crust with lateral variation of average density removal of the calculated gravity effect of the crustal model from the observed gravity field reveals residual anomalies of mantle origin this is confirmed by the correlation between mantle gravity anomalies and upper mantle velocity heterogeneities imaged by seismotomographic studies the tornquist teisseyre zone ttz marked in general by a gradient zone of mantle gravity anomalies is considered as a deep density section traced in the upper mantle down to a depth of 200 km across this suture zone a dramatic change of the structure physical properties and composition of the lithosphere of the continent occurs the different characters of the mantle gravity anomalies over the two main parts of the ttz the danish scandinavian and polish segments are explained by the peculiarities of their evolution and the different character of the prevailing tectonic regimes during the proterozoic cenozoic

topography of the lithosphere asthenosphere boundary below the upper rhine graben rift and the volcanic eifel region central europe abstract we study the crust mantle and lithosphere asthenosphere boundaries moho and lab in central europe specifically below the upper rhine graben urg rift the eifel volcanic region and their surrounding areas teleseismic recordings at permanent and mobile stations are analysed to search for shear s wave to compressional p wave converted phases after a special processing these phases are identified in shear wave receiver functions s rfs conversions from the moho at 2 9 3 3 s arrival time are the clearest signals in the s rfs and indicate a relatively flat moho at 27 30 km depth a negative polarity conversion signal at 7 9 s arrival time can be explained with a low shear wave velocity zone lvsz in the upper mantle we use forward s rf waveform modelling and monte carlo techniques to determine shear wave velocity vs depth z profiles which explain the observed s rf and which outline variations of the lithospheric thickness in the study region across the urg rift and its surrounding mountain ranges black forest odenwald etc the lab is at a depth of about 60 5 km this depth is found for the rift itself as well as for the rift shoulders southeast and southwest of the urg in the regions of the swabian alb and vosges mountains the lab dips to about 78 5 km depth in the volcanic eifel region the lab is at a much shallower depth of just 41 5 km there an upwelling mantle plume thermally eroded the lower lithosphere the reduction of vs is about 2 4 in the upper asthenosphere compared to the lower lithosphere this vs contrast may be explained with a low portion of partial melt or hydrous minerals in the asthenosphere

regional and teleseismic events recorded across the tesz during polonaise 97 abstract 20 polish short period three component stations were continuously operating for three weeks during polonaise 97 in the contact zone between palaeozoic and precambrian platforms in poland the distances between seismometers were about 20 km and the digitization interval was 0 02 s besides the shots a few regional events from the lubin area and teleseismic events mainly from the se backazimuth were also recorded interpretation of traveltimes for p and s waves for regional events using a simplified lt 7 model of crustal structure for theoretical calculation allowed correction of their origin time the same model can also explain the traveltime residuals of p waves for teleseismic events the main features of the division of poland into two platforms by the teisseyre tornquist tectonic zone ttz is seen both in the shape of residuals of teleseismic phases and in the receiver function a passive seismic experiment made during polonaise 97 as a reconnaissance for future teleseismic tomography experiment tor 2 gave quite promising results however to make a traveltime tomography and receiver function analysis the duration of data acquisition should be about half a year

imaging crustal discontinuities and the downgoing slab beneath western crete the migration of teleseismic receiver functions yields high resolution images of the crustal structure of western crete data were collected during two field campaigns in 1996 and 1997 by networks of six and 47 short period three component seismic stations respectively a total of 1288 seismograms from 97 teleseismic events were restituted to true ground displacement within a period range from 0 5 to 7 s the application of a noise adaptive deconvolution filter and a new polarization analysis technique helped to overcome problems with local coda and noise conditions the computation and migration of receiver functions results in images of local crustal structures with unprecedented spatial resolution for this region the crust under crete consists of a continental top layer of 15 20 km thickness above a 20 30 km thick subducted fossil accretionary wedge with a characteristic en echelon fault sequence the downgoing oceanic moho lies at a depth of 40 60 km and shows a topography or undulation with an amplitude of several kilometres as a consequence of slab depth and distribution of local seismicity the mediterranean ridge is interpreted as the recent accretionary wedge

magnetic anomaly pattern of central europe abstract the magnetic anomalies represented on our map of central europe reflect the geological units and these anomalies are tentatively correlated with known geological structures in scandinavia strong magnetic anomalies caused by crystalline rocks of the east european platform have been observed their southern boundary corresponds to the elbe line the border between the mobile part of the east european platform and the dutch german platform here only some broader anomalies can be found and are caused by a magnetic basement magnetization m 2 a m under a 12 15 km thick layer of sediments a southern margin of the dutch german platform can be assumed along the w e northern german line which is marked by local magnetic anomalies younger magmatic events are presumed to be the sources of these anomalies the rhenohercynian is located south of the dutch german platform small ne striking anomalies indicate a weak magnetic basement m 0 35 a m a magnetic relief varying between 9 and 15 km is obtained by relief calculations west of the rhenohercynian anomalies of relatively strong amplitudes prevail these correspond to the brabant massif the eastern boundary of which presumably influences the tectonically controlled anomalies of erkelenz and lingen there is no magnetic indication of a continuation of the brabant massif into the rhenohercynian the mid german crystalline rise and the saxothuringian zone of the variscan belt are situated south of the rhenohercynian both areas show strong magnetic anomalies the southwestern border forms an arch around the brabant massif and ends at the paris basin anomaly this magnetic zone finds its equivalent in a magnetic belt the donau anomaly which can be followed to the massif central in the southwest this is located in the middle of the moldanubian which is characterized by a relatively undisturbed magnetic field the strong anomalies in the saxothuringian and donau magnetic belts point to an accumulation of magmatic rocks these might be fragments of oceanic crust or ophiolites marking previous subduction or obduction zones another explanation may be the intrusion of predominantly basic material during former crustal thinning or stretching with the exception of the saxothuringian and donau anomaly magnetic belts there is no indication of oceanic crust in the magnetic anomaly map

continental crust composition constrained by measurements of crustal poisson s ratio deciphering the geological evolution of the earth s continental crust requires knowledge of its bulk composition and global variability the main uncertainties are associated with the composition of the lower crust seismic measurements probe the elastic properties of the crust at depth from which composition can be inferred of particular note is poisson s ratio this elastic parameter can be determined uniquely from the ratio of p to s wave seismic velocity and provides a better diagnostic of crustal composition than either p or s wave velocity alone1 previous attempts to measure have been limited by difficulties in obtaining coincident p and s wave data sampling the entire crust2 here we report 76 new estimates of crustal spanning all of the continents except antarctica we find that on average increases with the age of the crust our results strongly support the presence of a mafic lower crust beneath cratons and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions followed by magmatic underplating or a model in which crust formation processes have changed since the precambrian era

palaeozoic amalgamation of central europe new results from recent geological and geophysical investigations abstract multidisciplinary studies of geotransects across the north european plain and southern north sea and geological reexamination of the variscides of the north bohemian massif permit a new 3 d reassessment of the relationships between the principal crustal blocks abutting baltica along the trans european suture zone tesz accretion was in three stages cambrian accretion of the bruno silesian lysogory and malopolska terranes end ordovician early silurian accretion of avalonia and early carboniferous accretion of the armorican terrane assemblage ata palaeozoic plume influenced metabasite geochemistry in the bohemian massif explains the progressive rifting away of peri gondwanan crustal blocks before their accretion to baltica geophysical data faunal and provenance information from boreholes and dated small inliers and cores confirm that avalonian crust extends beyond the anglo brabant deformation belt eastwards to northwest poland the location and dip of reflectors along the tesz and beneath the north european plain suggest that avalonian crust overrode the baltica passive margin marked by a high velocity lower crustal layer on shallowly southwest dipping thrust planes forming the heligoland pomerania deformation belt the variscan orocline of southwest poland masks two junctions between the armorican terrane assemblage ata and previously accreted crustal blocks to the east is a dextrally transpressive contact with the bruno silesian and malopolska blocks accreted in the cambrian while to the north is a thrust contact with easternmost avalonia deeply buried beneath younger sedimentary cover in the northeast bohemian and rhenohercynian massifs devonian early variscide deformation dominated by wnw and nw directed thrusting records closure of ordovician devonian seaways between detached islands of the ata and avalonia

comparative tertiary stratigraphy of the rhine graben bresse graben and molasse basin correlation of alpine foreland events abstract comparative tectonostratigraphic analysis of the tertiary middle eocene pliocene of the rhine bresse graben system and the western molasse basin demonstrates the occurrence of eleven correlative sequences crf i xi these show a close relationship between intra basinal tectonics and depositional history their punctuated sediment accumulation can be related to phases of extra alpine taphrogenesis and alpine orogenesis and to coeval eustatic changes in sea level apparent simultaneity in rift and foredeep sequence development structural deformation and global change in sea level suggests a common causal control in which the development of the alps played an important role

seismic evidence for whole lithosphere separation between saxothuringian and moldanubian tectonic units in central europe 1 the bohemian massif is part of the variscan belt of central europe we carried out a high resolution mapping of lithospheric thickness beneath central europe by investigating 264 teleseismic events recorded at 80 broad band stations in the western bohemian massif with the method of s receiver function analysis a negative phase beneath the saxothuringian and northeastern tepla barrandian units at about 9 10 s before the s onset is interpreted as caused by the lithosphere asthenosphere boundary lab at 80 90 km depth in the moldanubian unit the negative phase occurs at 13 15 s before the s onset corresponding to lithospheric thickness of 120 130 km the boundary between the domains is oriented e w and probably marks the northern extension of moldanubian lithosphere the moho also deepens from the saxothuringian to the moldanubian unit the observed crustal lithospheric domains could represent two distinct microplates with a relatively sharp boundary cutting through the whole lithosphere

potential field imaging of palaeozoic orogenic structure in northern and central europe abstract the trans european suture zone tesz is the most fundamental lithospheric boundary in europe separating the ancient crust of the fennoscandian shield east european craton from the younger crust of central europe and extending deep into the mantle geophysical potential field images provide an overview of the entire palaeozoic orogenic system of northern and central europe for the first time the tesz is largely concealed by sedimentary basins of permian cenozoic age geological observations are largely restricted to local basement highs and deep boreholes and the coverage of deep seismic surveys is widely spaced despite experiments recently acquired within the europrobe programme by contrast the potential field data offer a relatively detailed coverage of standardised observations throughout the tesz while some features of the images may be sourced in the near surface particularly in the gravity image much of their content reflects the structure of the underlying palaeozoic basement at the scale presented the images highlight the most fundamental features of the crustal structure of the tesz these include the strong contrast between the highly magnetic crust of the east european craton and the less magnetic palaeozoic accreted terranes of central europe the lateral continuity of terranes and their internal structure particularly where arc magmatic complexes are involved and the location and geometry of the terrane boundaries oceanic sutures and strike slip zones that separate them

crustal and uppermost mantle structure of the bohemian massif based on celebration 2000 data 1 the deep structure of the bohemian massif bm the largest stable outcrop of variscan rocks in central europe was studied using the data of the international seismic refraction experiment central european lithospheric experiment based on refraction celebration 2000 the data were interpreted by seismic tomographic inversion and by two dimensional 2 d trial and error forward modeling of p and s waves additional constraint on crustal structure was given by amplitude modeling using the reflectivity method and gravity modeling though consolidated the bm can be subdivided into several tectonic units separated by faults shear zones or thrusts reflecting varying influence of the cadomian and variscan orogeneses the saxothuringian barrandian moldanubian and moravian velocity models determine three types of crust mantle transition in the bm reflecting variable crustal thickness and delimiting contacts of tectonic units in depth the nw area the saxothuringian has a highly reflective lower crustal layer above moho with a strong velocity contrast at the top of this layer this reflective laminated lower crust reaches depths of 26 35 km and is characteristic for the saxothuringian unit which was subject to eastward subduction the moldanubian in the central part is characterized by the deepest 39 km and the most pronounced moho within the whole bm with a strong velocity contrast 6 9 8 1 km s 1 a thick crust mantle transition zone in the se with velocity increase from 6 8 to 7 8 km s 1 over the depth range of 23 40 km seems to be the characteristic feature of the moravian overthrusted by the moldanubian during variscan collision

sequential h κ stacking to obtain accurate crustal thicknesses beneath sedimentary basins abstract low velocity sedimentary basins introduce error in many standard receiver function rf analysis techniques including common conversion point dueker and sheehan 1997 and crustal thickness v p v s ratio h stacking zhu and kanamori 2000 we describe a simple rf analysis method for obtaining accurate crustal thickness below seismic stations located in sedimentary basins the method extends the methods of zhu and kanamori 2000 it employs an iterative two layer depth v p v s stacking approach that first characterizes sediment properties thickness and v p v s allowing for the accurate interpretation of moho conversions without accounting for sedimentary layers standard rf analysis can mischaracterize crustal thickness based on ps phase delay by 10 km beneath deep basins we test the technique with synthetic seismograms and with data from us array transportable array ta stations from regions with sediment thicknesses that are well determined through other means we find sequential h stacking for sediment properties to be a simple technique that can benefit many rf analysis studies and can play an important role in crustal seismic studies in areas with thick or variable sediments

origin of gaseous hydrocarbons noble gases carbon dioxide and nitrogen in carboniferous and permian strata of the distal part of the polish basin geological and isotopic approach abstract sixteen natural gas samples collected from pennsylvanian and permian rotliegend and zechstein limestone strata of the distal part of the polish basin in wielkopolska and lower silesia were analysed for molecular composition and stable carbon isotope composition of hydrocarbons ch 4 c 2 h 6 c 3 h 8 n c 4 h 10 and i c 4 h 10 and co 2 stable hydrogen isotope composition of methane stable nitrogen isotope composition of n 2 and stable isotope composition of noble gases he ne ar kr and xe thirteen of analysed hydrocarbon gases reveal complete 13 c ch 4 13 c c 2 h 6 13 c c 3 h 8 and partial inversed isotopic trends from methane to propane thus they have a very complicated generation migration and accumulation history and range of their source rock horizons two source rock horizons occur ne from wolsztyn ridge they contain mixed types iii ii and ii iii kerogens of pennsylvanian age and mississippian and or devonian age respectively one source rock horizon occurs sw from wolsztyn ridge it contains type iii and mixed type iii ii kerogens of pennsylvanian age the kerogens in all source rock horizons generated gaseous hydrocarbons at two separate maturity stages about 0 5 to 0 8 in vitrinite reflectance scale at the first maturity stage and over 1 3 in vitrinite reflectance scale at the second maturity stage high concentrations of he in analysed gases are mostly a product of decay of u and th enriched in crustal materials a small contribution of he and ne of mantle origin to the gas reservoirs was inferred radiogenic 4 he 40 ar ratios are higher than the average production rate ratio of about 5 for crustal materials which might have been caused by a selective supply of lighter he through crustal rocks surrounding the gas reservoirs or higher u th k ratio than the crustal average co 2 from analysed gases was mainly generated during thermogenic processes of transformation of organic matter although some gases can contain components from endogenic processes and from thermal destruction of zechstein limestone and probably precambrian carbonates n 2 was mainly generated during thermal transformation of organic matter and had a large component released from nh 4 rich illites very high n 2 40 ar for the gases might be caused by accelerated thermogenic production of n 2 under the condition of high heat flux from volcanic activity at late pennsylvanian and early permian age deep seated faults mainly framing the wolsztyn ridge perform important role in migration and mixed in different proportions of noble gases originated from upper mantle and from mineralisation by radioactive minerals their fault surfaces and occurrence of pennsylvanian lower permian volcanites in crust as well as hydrocarbon gases co 2 and n 2 also from thermal destruction of nh 4 rich illites from gas generation kitchens of source rock horizons to the traps

thickness of the central and eastern european lithosphere as seen by s receiver functions summary s receiver functions obtained from seismograms of teleseismic events recorded at 78 european permanent broad band stations are used to estimate the thickness of the european lithosphere our results provide new independent information about the lithospheric thickness beneath the precambrian platform of eastern europe and the phanerozoic platform of central europe detailed high resolution images of the lithosphere asthenosphere boundary lab reveal indications for a typical continental lithosphere of about 100 km thickness beneath a majority of stations within central europe whereas in the vicinity of the trans european suture zone tesz the lithosphere thickens to about 130 km a relatively thin lithosphere of 80 km was found beneath the upper rhine graben region suggesting that the cenozoic extension affects the whole lithosphere no clear signal from the lab was detected beneath the alps and carpathians the lab sp phase might be disturbed by complicated structure due to ongoing collision subduction in these regions or the data are not yet sufficiently dense a relatively thicker lithosphere of about 120 km was found beneath the sw part of the bohemian massif that was formed during the variscan orogeny we found an lab depth of about 190 km near a single station located in the vrancea area eastern carpathians which is characterized by the occurrence of intermediate deep earthquakes beneath the stations located in the precambrian platform of eastern europe the lab deepens to approximately 200 km even though the converted phase from the lab is not as sharp as found beneath other stations located in central europe or even is missing

moho depth across the trans european suture zone from p and s receiver functions the mohorovicic discontinuity moho for short which marks the boundary between crust and mantle is the main first order structure within the lithosphere geodynamics and tectonic evolution determine its depth level and properties here we present a map of the moho in central europe across the teisseyre tornquist zone a region for which a number of previous studies are available our results are based on homogeneous and consistent processing of p and s receiver functions for the largest passive seismological data set in this region yet consisting of more than 40 000 receiver functions from almost 500 station besides we also provide new results for the crustal vp vs ratio for the whole area our results are in good agreement with previous more localized receiver function studies as well as with the interpretation of seismic profiles while at the same time resolving a higher level of detail than previous maps covering the area for example regarding the eifel plume region rhine graben and northern alps the close correspondence with the seismic data regarding crustal structure also increases confidence in use of the data in crustal corrections and the imaging of deeper structure for which no independent seismic information is available in addition to the pronounced stepwise transition from crustal thicknesses of 30 km in phanerozoic europe to more than 45 beneath the east european craton we can distinguish other terrane boundaries based on moho depth as well as average crustal v p v s ratio and moho phase amplitudes the terranes with distinct crustal properties span a wide range of ages from palaeoproterozoic in lithuania to cenozoic in the alps reflecting the complex tectonic history of europe crustal thickness and properties in the study area are also markedly influenced by tectonic overprinting for example the formation of the central european basin system and the european cenozoic rift system in the areas affected by cenozoic rifting and volcanism thinning of the crust corresponds to lithospheric updoming reported in recent surface wave and s receiver function studies as expected for thermally induced deformation the same correlation applies for crustal thickening not only across the trans european suture zone but also within the southern part of the bohemian massif

crustal structure below the polish basin is it composed of proximal terranes derived from baltica abstract the large scale seismic refraction and wide angle reflection experiment polonaise 97 together with lt 7 and ttz profiles carried out with the most modern techniques gave a high resolution of crustal structure of the trans european suture zone tesz in nw and central poland the results of seismic investigations show the presence of relatively low velocity rocks vp

s receiver function analysis of the crustal and lithospheric structures beneath eastern tibet abstract s receiver functions from 51 permanent broad band stations are used to investigate the structures of the crust and lithosphere beneath eastern tibet and sichuan basin by stacking the s receiver functions the sp converted phases from the moho and the lithosphere asthenosphere boundary lab are clearly visible the moho depth ranges from 40 to 50 km beneath sichuan basin and from 55 to 60 km on the west side of the longmenshan lms fault the largest depth is 70 km occurring at the northern sichuan yunnan terrane the lab depth beneath sichuan basin ranges from 130 to 170 km while that on the west side of lms ranges from 100 to 120 km from the east to the west across lms there is a sudden rise of the lab followed by a gradual dip western sichuan basin is found to be surrounded by thinner lithosphere extending northeastward along the lms and southward to indochina the thinner lithosphere may indicate that the lower part of eastern tibet lithosphere is heated and delaminated by the underlying hot asthenospheric flow thus reflecting the size and direction of the flow it appears that asthenospheric flow from tibet is resisted by the cold rigid sichuan basin thus branching into northeastward and southeastward parts the complicated topography of the lithosphere likely results from this dynamic process

eurobridge 95 deep seismic profiling within the east european craton abstract the eurobridge deep seismic sounding dss profile is a key component of a europrobe project to examine palaeoproterozoic processes of continental collision and crustal accretion its purpose is to establish the deep lithospheric structure of the east european craton between the exposed proterozoic and archaean complexes of the baltic and ukrainian shields in 1994 a dss experiment was recorded across the baltic sea from vastervik sweden to shventoji lithuania we report on eurobridge 95 the first onshore stage of the seismic profile it is 280 km long recorded from nw to se on the lithuanian part of the east european platform traversing the proterozoic west lithuanian granulite domain wlg and east lithuanian belt el terranes explosive shots of up to 1000 kg tnt were detonated at 10 shotpoints sp01 sp10 at intervals of about 30 km arrivals were recorded at 76 3 component seismograph stations with an average station spacing of 3 5 km providing high quality records a 11th shot of 3000 kg sp00 was fired in the baltic sea close to gotland raytracing analysis of refracted and reflected p waves has been used to determine a 2 dimensional seismic velocity model for the crust and uppermost mantle below eurobridge 95 the thickness of the phanerozoic sedimentary cover decreases from 2 2 km in the north west near the baltic sea coast to 0 4 km at the south east end of the profile near the lithuania belarus border crust in the north west and central part of profile consists of two major layers with a thickness of about 44 km increasing to 50 km and three layers in the south east crystalline upper crust is about 20 km thick thinning in the south east with p wave velocities of 6 0 6 3 km s a very weak low velocity zone with a velocity contrast of 0 1 0 2 km s occurs at 8 13 km depth below the north west and central part of the profile only lower crust exhibits velocities of commonly 6 5 6 9 km s and thickens to the south east with p wave velocities up to 7 0 km s in the deepest parts crystalline crust is characterised by low velocity gradients and small velocity contrasts at most seismic boundaries major lateral changes in crustal velocity structure at all depths can be spatially correlated with the wlg el boundary determined from near surface geological information very strong reflections from the moho boundary are observed the mantle p wave velocity immediately below the crust is 8 2 8 35 km s a reflector in the lower lithosphere at a depth of almost 70 km was found below lithuania reflectivity modelling of the gotland shot data suggests that this interface is absent offshore where mantle velocities are lower the dss model supports the interpretation of the wlg and el as terranes of proterozoic age forming part of fennoscandia later modification of crustal structure may have occurred possibly by a mantle heating episode centred on the baltic sea area

eucrust 07 a new reference model for the european crust 1 we present a new digital model eucrust 07 for the crust of western and central europe and surroundings 35n 71n 25w 35e available results of seismic reflection refraction and receiver functions studies are assembled in an integrated model at a uniform grid 15 0 15 0 the model consists of three layers sediments and two layers of the crystalline crust besides depth to the boundaries we provide average p wave velocities in the upper and lower parts of the crystalline crust the new model demonstrates large differences in the moho depth compared to previous compilations over 10 km in some specific areas e g the baltic shield furthermore the velocity structure of the crust is much more heterogeneous than in previous maps eucrust 07 offers a starting point for numerical modeling of deeper structures by allowing correction for crustal effects beforehand and to resolve trade off with mantle heterogeneities citation tesauro m m k kaban and s a p l cloetingh 2008 eucrust 07 a new reference model for the european crust geophys res lett 35 l05313 doi 10 1029 2007gl032244

the nars deep project the nars deep project involves the deployment of broadband seismological stations in russia belarus and the ukraine six stations were installed in 1995 two in 1997 and more stations were to be installed from 1998 onwards the nars deep project was initiated as a temporary deployment but funding from the european community enabled the stations to become permanent in this paper we present first results of the nars deep project a surface waveform inversion for the upper mantle structure along a profile from egypt to spitsbergen shows evidence for strong variations in the shear velocity structure for the different tectonic units the most striking features of the model comprise strong lithospheric anisotropy beneath the eastern mediterranean and a lithospheric thickness of approximately 200 km beneath the shield areas the crustal structure beneath the seismic station in st petersburg was investigated using the receiver function method the results of a monte carlo inversion for the receiver functions of this station show evidence for a sedimentary layer with a thickness of less than 1 km overlying an upper crustal layer extending to a depth of approximately 16 km the moho depth cannot be resolved from the receiver functions of this station

inverse and 3d forward gravity modelling for the estimation of the crustal thickness of egypt abstract a 3d crustal density model for egypt was compiled it is constrained by available deep seismic refraction receiver functions analysis borehole and geological data in egypt seismic data are sparsely and irregularly distributed consequently we developed the crustal thickness model by integrating seismic and gravity data satellite gravity data was inverted to build an initial model which was followed by a detailed 3d forward gravity modelling the initial crustal thickness is determined by applying seismically constrained non linear inversion based on the modified bott s method and tikhonov regularization assuming spherical earth approximation moreover the gravity inversion based moho depth estimates are in good agreement with results of seismic studies and are exploited for the 3d forward modelling crustal thicknesses range from 25 to 30 km along the rifted margins of the red sea which thin toward the mediterranean sea thicknesses in southern egypt reach values between 35 and 40 km a maximum crustal thickness of 45 km is found in the southwestern part of egypt within the sinai peninsula the thickness varies from the shallow southern edge 31 km and increases toward the north 36 km our model revealed a thick lower crust beneath the southern part of egypt which can be associated with crustal modification that occurred during the collision of east gondwana and the saharan metacraton along the keraf suture zone during the final assembly of gondwana in the neoproterozoic finally the isostatic implications of the differences between the seismic and gravity derived mohos are thoroughly discussed in conclusion the developed 3d crustal thickness model provides high resolution moho depth estimates that closely resembles the major geological and tectonic features also the existing correlation between the topography bouguer anomalies and moho depths indicates that the investigated area is close to its isostatic equilibrium

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

precambrian domains in lithuania evidence of terrane tectonics abstract the west lithuanian granulite wlg and east lithuanian domains eld form the proterozoic basement of lithuania and can be distinguished on the basis of differing structural patterns lithologies and evolutionary histories they are juxtaposed along the mid lithuanian suture zone mlsz in the wlg the main lithotectonic complexes comprise felsic and intermediate mostly metasedimentary granulites in the south west and mafic metaigneous granulites in the north east the former are interpreted as marine metapelites while most of the mafic ones have been derived from island arc tholeiites these rock complexes trend nw se and are marked by contrasting gravity and magnetic anomalies ne and e w striking faults and shear zones complicate the potential field patterns sets of nw trending anomalies also extend from lithuania across the baltic sea to south central sweden and indicate that the wlg complexes continue into the baltic fennoscandian shield voluminous anatectic granites alternate with the metapelites whereas the mafic granulites occur together with enderbites and charnockites in the eld the main structures produce strong nne ssw oriented gravity and magnetic anomalies which trend parallel to the belarus baltic granulite belt bbg and other terranes situated still farther east the eld is composed of metasedimentary rocks interpreted as one time graywackes shales and dolomites accumulated in continental margin arc and shallow water basinal environments amphibolites and gabbros with morb and iat characteristics and voluminous granitoids are also present the coexistence of juvenile mafic rocks with continental margin and shelf sediments suggests an oceanic back arc setting the two lithuanian basement domains display contrasting metamorphic histories that suggest separate developments before the eventual amalgamation in the wlg the metapelites indicate peak metamorphism at high temperatures up to 850 900 c and moderate pressures 8 10 kbar this was followed by cooling and reheating and then an uplift event repeated magmatic underplating accompanied the metamorphism in the eld in contrast the rocks have been subjected to comprehensive metamorphism under moderate amphibolite facies conditions that metamorphism however was not uniform throughout the metasediments in the east have recorded pressures similar to those in the neighbouring bbg 7 8 kbar but lower temperatures 650 680 c while in the central and western parts of the eld metamorphism occurred at ca 480 580 c with pressures increasing from 3 4 kbar in the centre to 6 kbar close to the western boundary reheating to 700 c due to a ca 1 5 ga magmatic event is characteristic the mlsz which separates the two lithuanian basement domains from each other is a n s oriented ca 30 50 km wide westward plunging crustal discontinuity marked by magnetic and gravity highs mafic and felsic intrusions and sheared rocks crustal thicknesses change from 42 44 km in the west to 50 km in the eastern side of the zone which also truncates a crustal low velocity layer characteristic of the wlg the amalgamation of the wlg and eld along the mlsz occurred at ca 1 71 1 66 ga after which time both domains were affected by the same post kinematic anorogenic magmatism ca 1 58 1 45 ga ago that event and related shearing were responsible for some ultimate refragmentation of the lithuanian basement terranes

the rapid drift of the indian tectonic plate the breakup of the supercontinent gondwanaland into africa antarctica australia and india about 140 million years ago and consequently the opening of the indian ocean is thought to have been caused by heating of the lithosphere from below by a large plume whose relicts are now the marion kerguelen and reunion plumes plate reconstructions based on palaeomagnetic data suggest that the indian plate attained a very high speed 18 20 cm yr 1 during the late cretaceous period subsequent to its breakup from gondwanaland and then slowed to approximately 5 cm yr 1 after the continental collision with asia approximately 50 myr ago the australian and african plates moved comparatively less distance and at much lower speeds of 2 4 cm yr 1 refs 3 5 antarctica remained almost stationary this mobility makes india unique among the fragments of gondwanaland here we propose that when the fragments of gondwanaland were separated by the plume the penetration of their lithospheric roots into the asthenosphere were important in determining their speed we estimated the thickness of the lithospheric plates of the different fragments of gondwanaland around the indian ocean by using the shear wave receiver function technique we found that the fragment of gondwanaland with clearly the thinnest lithosphere is india the lithospheric roots in south africa australia and antarctica are between 180 and 300 km deep whereas the indian lithosphere extends only about 100 km deep we infer that the plume that partitioned gondwanaland may have also melted the lower half of the indian lithosphere thus permitting faster motion due to ridge push or slab pull

analysis of waves converted from s to p in the upper mantle beneath the baltic shield teleseismic data recorded by broadband stations of the swedish national seismic network have been used in a study of waves converted from s to p in the uppermost mantle s to p converted waves are recorded as precursors to the direct s arrival this enables us to study seismic discontinuities at depths of 100 300 km where the traditional receiver function technique based on p to s conversion fails due to disturbances from crustal reverberations clear signals of s to p conversion are seen for several horizons in the 50 200 km depth range this is interpreted as a layered lithosphere with alternating high and low velocity bodies a sharp contrast is imaged at depths around 160 km and continuous for almost 1000 km in the southern part of the profile this structure coincides with the velocity contrast interpreted by several authors as the lower limit of a prominent low velocity zone in the 95 to 160 km depth range a feature which we identify as the lithosphere asthenosphere boundary is clearly imaged at depths around 200 km

seismic velocities in southern tibet lower crust a receiver function approach for eclogite detection summary beneath the tibet plateau the deficit of crustal thickening with respect to what is expected from the plate tectonic constraints is thought to be absorbed either by lateral extrusion or by vertical rock mass transfer to nourish the unsettled debate of the relative importance of these two processes we propose a new approach based on the s to p and the p to s wave conversions enabling the precise determination of the seismic velocities the weighted amplitudes of the direct conversion and of reverberations are stacked at their predicted arrival times for various values of layer thickness and vp vs ratio separately for two sets of p and s receiver functions for each set of receiver functions coherent stack gives the vp vs ratio and thickness for the considered layer the grid search stacking method the values of vp vs ratio and layer thickness are functions of the velocity used for stacking the set of receiver functions but using the p and s receiver functions allows us to solve this indetermination and to find the effective parameters of the layer velocity vs vp vs ratio and thickness we use a bootstrap resampling of the receiver function data sets to estimate the parameters uncertainties for the southern lhasa block the migrated sections of both p and s receiver functions hi climb experiment data show a layer in the lower crust that may be related to the lower indian crust underplated beneath tibet with the grid search stacking method high shear wave velocities vs 4 73 km s 1 and low vp vs ratios 1 69 are detected in this layer such values are typical for high grade eclogites and the low vp vs ratio precludes the confusion with mafic granulites there is no evidence for partial eclogitization near and south of the yarlung tsangpo suture and the about 19 km thick eclogitic layer extends northwards only to about the middle of the lhasa terrane

multistep modelling of teleseismic receiver functions combined with constraints from seismic tomography crustal structure beneath southeast china summary with a growing number of modern broad band seismographic stations in asia the conditions have improved to allow higher resolution structural studies on regional scales here we perform a receiver based study of the lithosphere of southeast china using waveform records ofexcellentqualityfrom14chinesenationaldigitalseismicnetworkandfourglobalseismic network stations calculating the theoretical receiver functions rfs that match the observed rfs from teleseismic waveforms is an established technique for retrieving information about crustalanduppermantlestructurebeneathaseismicreceiver rfs however arepredominantly sensitivetothegradientsinthelithosphericelasticparameters anditisimpossibletodetermine a non unique distribution of seismic parameters such as absolute shear wave speeds as a function of depth unless other geophysical data are combined with rfs thus we combine rfswithindependentinformationfromshearandcompressionalwavespeedsaboveandbelow the mohoroviy discontinuity available from the existing tomographic studies we introduce a statistical approach for automatically selecting only mutually coherent rfs from a large set of observed waveforms furthermore an interactive forward modelling software is introduced and applied to observed rfs to define a prior physically acceptable range of elastic parameters in the lithosphere this is followed by a grid search for a simple crustal structure an initial model for a linearized iterative inversion is constructed from multiple constraints including results from the grid search for shear wave speed the moho depth versus vp vs ratio domain search and tomography the thickness of the crust constrained by our multistep approach appears to be more variable in comparison with tomographic studies with the crust thinning significantly towards the east we observe low values of vp vs ratios across the entire region which indicates the presence of a very silicic crust we do not observe any correlation between the crustal thickness or age of the crust with vp vs ratios which argues against a notion that there is a simple relationship between mineralogical composition and crustal thickness and age on a global scale

receiver function analysis of the crust and upper mantle from the north german basin to the archaean baltic shield summary two passive seismic experiments have been carried out across the trans european suture zone tesz from northern germany to southern sweden tor and across the proterozoicarchaean suture in finland svekalapko to improve our understanding of the processes involved in the creation of the european continent teleseismic earthquakes recorded by the two networks and stations of the grsn and geofon permanent networks have been used for studies of the crust mantle and upper mantle seismic discontinuities with the receiver function method along the tor network the depth to the moho increases from 30 km at the southern edge of the profile to 40 km at the elbe line between the elbe line and tesz the moho branches off and whereas the deeper branch continues at 40 km depth to the tesz a second branch appears at 30 35 km depth the upper branch descends north of the tesz to below 55 km under the northern end of the tor profile the crustal thickening north of the tesz is accompanied by an increase in average vp vs values appearance of intracrustal conversion zones and north dipping features which we interpret as remnants of the subduction and subsequent collision between avalonia and baltica in southern finland beneath the svekalapko network the moho starts in the south at the depth of 40 45 km plunges to about 65 km depth south of the archaean proterozoic suture this deepening of the moho is coincident with a north dipping intracrustal structure apparently related to the subduction and collision and of the proterozoic and archaean provinces in proterozoic north of the line of the suture the moho rises smoothly to 45 50 km depth in the archaean province along the tor profile 410 and 660 discontinuities were hard to detect however manyfold stacking of receiver functions revealed that the conversions from the two discontinuities arrive more or less according to iasp91 predicted time across the svekalapko network 410 and 660 discontinuities arrive markedly earlier than iasp91 theoretical arrival times in particular north of the archaean proterozoic suture in finland the 410 and 660 km conversions arrive about 2 s earlier indicating about 5 per cent higher average upper mantle velocities and lower temperatures than what iasp91 global model predicts

crust and mantle structure across the basin and range colorado plateau boundary at 37 n latitude and implications for cenozoic extensional mechanism we present new evidence on the seismic velocity and density of the crust and upper mantle along a 200 km long transect across the eastern basin and range and western colorado plateau at 37 n latitude receiver functions computed from the p waveforms recorded with 10 portable broadband stations deployed along the transect were used to estimate crustal thickness variations the crust is 30 35 km thick within the eastern basin and range and increases over a distance of 100 km at the western edge of the colorado plateau reaching a maximum of approximately 45 km east of the hurricane fault the timing of crustal multiples within the reciever functions were used to estimate the v p v s of the crust along the profile and we found that the western colorado plateau crust is characterized by a high poisson s ratio 0 28 0 29 indicative of a crust with an average mafic composition we estimated the upper mantle lid thickness along our profile based on teleseismic p wave travel times and constraints provided by gravity data our data and available geophysical constraints are most consistent with a lithosphere that thickens from an average thickness of 60 km beneath the basin and range to 100 km beneath the western colorado plateau although the basin and range lithosphere may have significant thickness variations the thick strong mafic crust and thicker mantle lid under the colorado plateau can account for the relative geologic stability and subdued magmatism of the plateau during laramide compression and cenozoic extension compared to surrounding regions the crustal and lithospheric thinning across the tectonic boundary occurs over a short distance 100 km suggesting it is a geologically young feature produced by a predominantly mechanical response to late cenozoic extension our new lithosphere model at 37 n latitude is consistent with the existence in early cenozoic time of a flat subducted slab at 100 km depth and a relict sevier laramide 50 60 km thick crustal welt and 60 100 pure shear extension values of 1 6 2 0 during the late cenozoic

crystalline lithology across the kapuskasing uplift determined using in situ poisson s ratio from seismic tomography seismic refraction tomography has been used to image lateral velocity variations both vp and vs within the shallow crystalline basement using travel times from a high resolution reflection profile across the kapuskasing uplift structure in northern ontario comparison of these in situ velocities and the outcrop geology indicates a correlation of velocity with the major lithologic units anorthosite vp 6150 6350 m s and vs 2700 3000 m s mafic gneiss vp 6000 6250 m s and vs 2775 3000 m s tonalite vp 5850 6000 m s and vs 2950 3025 m s vp measurements on core samples from the main lithologic units confirm that tonalite can be be clearly distinguished from mafic gneiss and anorthosite based on vp the observed vp values are attributed to mineralogy based on modal analyses of core samples from the same region poisson s ratio calculated from in situ vp and vs helps to discriminate between velocity variations caused by porosity effects from those due to lithology values of poisson s ratio obtained for the three lithologic units within the upper 100 m of the basement are anorthosite 0 35 0 39 mafic gneiss 0 34 0 38 and tonalite 0 32 0 34 these relatively high values of poisson s ratio indicate that the shallow basement is porous and water saturated poisson s ratio is a particularly effective discriminator in this instance because of its extremely low value in quartz 0 08 relative to other silicate minerals 0 21 0 32 and the greater quartz content of tonalite 27 36 relative to anorthosite and mafic gneiss 0 23 reflection coefficients calculated for the contrasting lithologies range up to 0 065 for tonalite mafic gneiss contacts and up to 0 044 for tonalite anorthosite contacts confirming that an interlayered sequence of tonalitic anorthositic and mafic rocks mapped at the surface may be the cause of the shallow reflections observed in the coincident seismic reflection data

boundaries of mantle lithosphere domains in the bohemian massif as extinct exhumation channels for high pressure rocks abstract five domains microplates have been recognized by seismic anisotropy in the mantle lithosphere of the bohemian massif the mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their variscan assembly the present day mantle fabric indicates that this process consisted of at least three oceanic subductions each followed by an underthrusting of the continental lithosphere the seismic anisotropy does not detect remnants of the oceanic subductions but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions the most robust continent continent collision was followed by westward underthrusting of the brunovistulian mantle lithosphere still detectable by seismic anisotropy more than 100 km beneath the moldanubian mantle lithosphere major occurrences of the high pressure ultra high pressure hp uhp rocks follow the ene and nne oriented sutures and boundaries of the mantle lithosphere domains mapped from three dimensional modeling of body wave anisotropy the hp uhp rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries the close relation of the mantle sutures and occurrences of the hp uhp rocks near the paleosubductions testifies for models interpreting the granulite garnet peridotite association by oceanic continental subduction underthrusting followed by the exhumation of deep seated rocks our findings support the bivergent subduction model of tectonic development of the central part of the bohemian massif the inferences from seismic anisotropy image the bohemian massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric the collisional mantle boundaries blurred by tectonometamorphic processes in easily deformed overlying crust served as major exhumation channels of the hp uhp rocks

geophysical and petrological modeling of the lower crust and uppermost mantle in the variscan and proterozoic surroundings of the trans european suture zone in central europe abstract high quality seismic data on the lower crust and uppermost lithospheric mantle in the central european part of the trans european suture zone together with thermal and gravimetric data enables the quantitative modeling of the rocks occurring in those parts of the lithosphere including their mineral compositions and the chemical composition of individual minerals the p3 seismic profile is located at the sw margin of the east european craton the lower crust is dominated by gabbronoritic intrusions plagioclase an 45 ab 55 clinopyroxene di 80 hed 20 orthopyroxene en 74 fs 26 and the uppermost mantle is harzburgitic olivine and orthopyroxene mg 0 91 the lower crust and upper mantle of the p1 seismic profile belong to the trans european suture zone albeit the upper crust is of variscan affinity the p1 lower crust has gabbronoritic composition which is layered from plagioclase rich compositions on the top to the orthopyroxene rich ones at the bottom plagioclase an 45 ab 55 clinopyroxene di 80 hed 20 orthopyroxene en 85 fs 15 and is lithologically different proterozoic and variscan surroundings the 100 200 km eclogite slice garnet alm 48 gr 25 py 27 clinopyroxene di 51 hed 10 jd 39 with a thickness of 5 10 km occurs in the uppermost mantle sampled by the p1 profile the nied wied massif is located at the ne margin of the bohemian massif which shows an exposed variscan basement the lower crust beneath the nied wied massif consists of gabbroic rock of variable proportions of plagioclase an 45 ab 55 and clinopyroxene di 80 hed 20 whereas the uppermost mantle is supposedly spinel harzburgite olivine ortho and clinopyroxene mg 0 90 our models show that the lowermost crust and uppermost mantle of the east european craton do not continue to the sw into the trans european suture zone in its central european section in poland

moho depth and poisson s ratio in the western central alps from receiver functions summary current knowledge about deep crustal structure of the alpine orogen has mainly been derived from p wave velocity models obtained from active and passive seismic experiments a complementary s wave model to provide lithological constraints necessary for unique structural interpretation has been missing to date in this paper we present important new information on s wave velocity model in the alps we applied the receiver function method using 6 yr of high quality data from 61 permanent and temporary stations sampling the western central alps we determined first order crustal features moho depth h and average vp vs ratio with the h stacking technique that uses timing of direct and multiple p to s converted phases from the moho interface synthetic tests reveal a dipping moho interface expected beneath an orogen causes a systematic bias of h and potentially leading to misinterpretation we thus applied corrections determined from synthetic data to remove the bias providing better fit of recovered moho depths with active seismic estimates for each site we also obtained independent h and estimates based on the timing of the strong ps phase our results show a gently south southeast dipping european moho at a depth of 24 30 km beneath the northern alpine foreland steepening rapidly towards the europe africa suture zone to reach a maximum depth of 55 km south of the suture the moho of the adriatic crust promontory of the african plate is at 35 45 km depth in the previously ill constrained western alps we found the european moho at 30 km depth beneath the more external units dipping east northeast to reach 50 55 km in the inner core of the alps the poisson s ratio clearly correlates with the tectonic units that comprise the alps average crustal values in the european alpine foreland are close to 0 25 in the alps we observe low values 0 22 in the highly deformed nappes of the mesozoic helvetic and southern alps indicating a thickening of felsic upper crustal material in contrast the poisson s ratio is significantly higher 0 26 in the penninic and austroalpine units near the suture zone this rapid and significant change marks a clear rupture between the alpine forelands and the suture domain we assign this high poisson s ratio to doubling of mafic lower crust consistent with results from previous active seismic experiments a continuation of the lower crustal wedge into the central part of the western alps however seems unlikely based on low observed poisson s ratios

structure of the european upper mantle revealed by adjoint tomography the structure of the european crust and upper mantle is precisely known only in limited regions a new tomographic model for the entire european upper mantle identifies northeastward subduction of the adria plate beneath the dinarides mountains volcanism related to the upwelling eifel hotspot and mantle delamination beneath scandinavia

systematics of chromitite occurrences in central palawan philippines the chromitite occurrences in the central palawan ophiolite can be classified into four groups based on their chemistry and geological relationships group i chromites from a deep tectonite level of the ophiolite complex show cr cr al values of between 0 78 and 0 90 whereas group ii from a shallower level gives values of 0 64 0 78 and group iii from the immediate gabbro lower contact dunite cumulates and diapirs show values of 0 5 0 64 group iv chromites from the gabbro zone have ratios around 0 38 0 5 larger orebodies type a representing a first stage of partial melting of a primordial mantle show cr fe ratios between 2 5 and 4 5 whilst those of small chromitite bodies with a thin dunite envelope type b lie below 2 5 these small bodies belong to a second stage of magma generation for both types the cr fe ratio increases with the chromite silicate ratio within individual occurrences an additional method which may help to subdivide these chromitites involves their silicate and ore inclusions the platinum group minerals for example occur mainly in chromites of group ii type a the intensive tertiary tectonic activity to which the ophiolite was subjected during and after emplacement disturbs the regular pattern of the ophiolite stratigraphy and its chromitite occurrences

the waulsortian type mound in the lower namurian of the lublin basin se poland abstract a unique waulsortian like mound is recognized in the lower namurian succession of the central part of the lublin basin se poland the carboniferous succession is characterized here by yoredale type cyclothems with carbonate units of relatively constant thickness an unexpected increase in thickness of the carbonate unit in the minkowice 4a well indicates the occurrence of an organic buildup at least 35 m thick sedimentological analysis reveals that its skeletal composition as well as its peloidal matrix abundant stromatactoid cavities and succession of cements indicate close analogies to similar facies in lower carboniferous waulsortian type mud mounds oxygen isotope data indicates that the formation and growth of the described mound were probably stimulated by hot water vents the occurrence of hot water vents in the open marine setting of the lublin basin is interpreted as a consequence of early namurian tectonic activity when a local tectonic compressional regime occurred in some parts of the basin the mound does not function as a hydrocarbon reservoir however its characteristics point to the presence of sedimentary traps which hitherto have not been recognized in this region

crustal structure along the central segment of the egt from seismic refraction studies abstract the seismic refraction line between the gulf of genova and the baltic sea was carried out in 1986 as part of the european geotraverse egt 86 the central segment of the egt also known as eugemi european geotraverse middle part has a total length of 825 km and runs from the northern margin of the alps to the baltic sea traversing mainly the variscan mountain area of western germany the p wave data of nine shotpoints were interpreted in detail and a two dimensional p velocity model of the crust was developed between the molasse basin and the southern end of the north german basin for the north german basin the data quality justifies only the construction of a simplified model the internal crustal structure is quite complex in the upper crust of the moldanubian and saxothuringian zones of the variscan orogen the velocities are lower than in the rhenohercynian area the velocity of 6 0 km s representing consolidated seismic basement is reached at depths of as much as 10 12 km northern margin of alps and north german basin and of only 3 km under the mid german crystalline rise mid crustal velocities range from 5 8 to 6 1 km s forming weak velocity reversals in some parts in the lower crust velocities as low as 6 2 km s are seen near the alps in contrast to velocities between 6 8 and 7 2 km s in the exposed variscan orogen north of shotpoint e between hannover and the river elbe the velocity of the lower crust is about 6 4 km s north of the elbe line it increases abruptly to 6 9 km s the crust mantle boundary rises from 34 km depth under the northern margin of the alps to 29 km under the swabian jura under the variscan orogen to the north the crustal thickness varies only slightly around an average depth of about 29 1 k but drops to about 30 km under the north german basin between the elbe line and the ringkobing fyn high the moho rises to a depth of about 26 km and the data indicate at least one fault like step of 1 km before the crust thickens toward the basement high the velocities in the uppermost mantle show considerable variation the highest velocity of 8 4 km s is observed beneath the saxothuringian zone and the lowest values of 7 8 7 9 km s are recorded under the hessen depression

some aspects of the late and post variscan development of the northwestern german basin abstract the crust of northern germany can be subdivided into three provinces that are evident by differences in crustal density seismic velocity reflectivity magnetic characteristics thermal history and electric conductivity these provinces are limited by the elbe river and the northern foothills of the mittelgebirge during the pre and post variscan evolution the tectonic setting of northern germany has changed repeatedly each of the three recognized basement provinces differs in the timing of basement consolidation caledonian variscan the sequence of basin development during permian mesozoic and cenozoic times and the timing and intensity of magmatic activity permian cretaceous cenozoic

the s receiver functions synthetics and data example summary recently the s receiver function method has been successfully developed to identify upper mantle interfaces s receiver functions have the advantage of being free of s wave multiple reflections and can be more suitable than p receiver functions for studying mantle lithosphere however because of specific ray geometry and interference of diverse phases the s receiver function method has some technical difficulties and limitations we use synthetic seismograms to demonstrate the feasibility and limitations of s receiver functions for studying mantle structures full wavefield seismograms were calculated using the reflectivity method and processed to generate synthetic s receiver functions for s sks and scs waves results show that s receiver functions can be obtained from waveforms of s sks and scs waves the synthetic s receiver functions for these incident waves show s to p converted phases at all discontinuities in the crust and upper mantle useful ranges of epicentral distances for calculation of s receiver functions are 55 85 for s 85 for sks and 50 75 for scs waves we apply both the s and p receiver function methods to data recorded at broadband station ykw3 in northwest canada the study shows that there is significant agreement among different receiver function methods and demonstrates the usefulness of s receiver functions for imaging the mantle lithosphere

epcrust a reference crustal model for the european plate summary we present a new crustal model for the european plate derived from collection and critical integration of information selected from the literature the model covers the whole european plate from north africa to the north pole 20 n 90 n and from the mid atlantic ridge to the urals 40 w 70 e the chosen parametrization represents the crust in three layers sediments upper crust and lower crust and describes the 3 d geometry of the interfaces and seismologically relevant parameters isotropic p and s wave velocity plus density with a resolution of 0 5 0 5 on a geographical latitude longitude grid we selected global and local models derived from geological assumptions active seismic experiments surface wave studies noise correlation receiver functions model epcrust presents significant advantages with respect to previous models it covers the whole european plate it is a complete and internally consistent model with all the parameters provided also for the sedimentary layer it is reproducible it is easy to update in the future by adding new contributions and it is available in a convenient digital format epcrust could be used to account for crustal structure in seismic wave propagation modelling at continental scale or to compute linearized crustal corrections in continental scale seismic tomography gravity studies dynamic topography and other applications that require a reliable crustal structure because of its resolution our model is not suited for local scale studies such as the computation of earthquake scenarios where more detailed knowledge of the structure is required we plan to update the model as new data will become available and possibly improve its resolution for selected areas in the future

seismic evidence for asthenospheric updoming beneath the western bohemian massif central europe 1 detailed images of the lithosphere beneath the western bohemian massif were obtained by analysis of more than 8500 p receiver functions at the intersection of regensburg leipzig rostock zone and eger rift crustal thickness decreases to 26 km from approx 31 km in the surroundings the receiver functions display a positive phase at about 6 s delay time and a strong negative phase at 7 to 8 s which coincides with an area of moho updoming co2 mantle derived degassing and earthquake swarm activity these phases can be modeled by a velocity increase at 50 km and a velocity decrease at 65 km depth the velocity decrease observed over an area of 5300 km2 gives evidence for local asthenospheric updoming and or a confined body of partial melt which might be the cause for high co2 mantle fluid flow and earthquake swarm activity in this recently nonvolcanic intracontinental rift area

tracing the influence of the trans european suture zone into the mantle transition zone cratons with their thick lithospheric roots can influence the thermal structure and thus the convective flow in the surrounding mantle as mantle temperatures are hard to measure directly depth variations in the mantle transition zone mtz discontinuities are often employed as a proxy here we use a large new data set of p receiver functions to map the 410 km and 660 km discontinuities beneath the western edge of the east european craton and adjacent phanerozoic europe across the most fundamental lithospheric boundary in europe the trans european suture zone tesz we observe significantly shorter travel times for conversions from both mtz discontinuities within the craton caused by the high velocities of the cratonic root by contrast the differential travel time across the mtz is normal to only slightly raised this implies that any insulating effect of the cratonic keel does not reach the mtz in contrast to earlier observations in siberia we do not find any trace of a discontinuity at 520 km depth which indicates a rather dry mtz beneath the western edge of the craton within most of covered phanerozoic europe the mtz differential travel time is remarkably uniform and in agreement with standard earth models no widespread thermal effects of the various episodes of caledonian and variscan subduction that took place during the amalgamation of the continent remain only more recent tectonic events related to alpine subduction and quarternary volcanism in the eifel area can be traced while the east european craton shows no distinct imprint into the mtz we discover the signature of the tesz in the mtz in the form of a linear region of about 350 km width with a 1 5 s increase in differential travel time which could either be caused by high water content or decreased temperature taking into account results of recent s wave tomographies raised water content in the mtz cannot be the main cause for this observation accordingly we explain the increase equivalent to a 15 km thicker mtz by a temperature decrease of about 80 k we discuss two alternative models for this temperature reduction either a remnant of subduction or an indication of downwelling due to small scale edge driven convection caused by the contrast in lithospheric thickness across the tesz any subducted lithosphere found in the mtz at this location is unlikely to be related to variscan subduction along the tesz though as eurasia has moved significantly northward since the variscan orogeny

seismic velocity structure across the fennoscandia sarmatia suture of the east european craton beneath the eurobridge profile through lithuania and belarus

crustal structure beneath china from receiver function analysis 1 we collected and processed a large amount of high quality broadband teleseismic waveform data recorded by the 48 chinese national digital seismic network stations to estimate large scale lateral variations of crustal thickness and vp vs ratio hence poisson s ratio beneath china a statistical method was used to select mutually coherent receiver functions at each station which yielded over 200 traces for most of the stations with the conventional h the crustal thickness and vp vs ratio approach there is a large trade off between h and consequently multiple maxima are frequently observed in the h domain we introduced a weight function that measures the coherence between the p to s conversion and the reverberation phases at each h grid to reduce the trade off a 4th root stacking method was further applied to reduce uncorrelated noise relative to the linear stack these modifications turned out to be very effective in reducing the h trade off and yielded reliable estimates of crustal thickness and vp vs ratio the crust beneath eastern china is as thin as 31 33 km and the underlying moho is relatively flat and sharp in the western part of china the crust is considerably thicker and shows large variations the moho is observed at about 51 km depth along the tian shan fold system and about 84 km deep beneath the central part of the tibetan plateau the transition occurs at the so called n s belt between about 100 and 110 e which is featured by unusually high seismicity and large gravity anomalies the average vp vs ratio over the mainland china crust is about 1 730 0 249 significantly lower than the global average 1 78 0 27 of the continental crust this lower vp vs ratio may suggest a general absence of mafic lowermost crustal layer beneath china

lithospheric structure of the aegean obtained from p and s receiver functions combined p and s receiver functions from seismograms of teleseismic events recorded at 65 temporary and permanent stations in the aegean region are used to map the geometry of the subducted african and the overriding aegean plates we image the moho of the subducting african plate at depths ranging from 40 km beneath southern crete and the western peloponnesus to 160 km beneath the volcanic arc and 220 km beneath northern greece however the dip of the moho of the subducting african plate is shallower beneath the peloponnesus than beneath crete and rhodes and flattens out beneath the northern aegean observed p to s conversions at stations located in the forearc indicate a reversed velocity contrast at the moho boundary of the aegean plate whereas this boundary is observed as a normal velocity contrast by the s to p conversions our modeling suggests that the presence of a large amount of serpentinite more than 30 in the forearc mantle wedge which generally occurs in the subduction zones may be the reason for the reverse sign of the p to s conversion coefficient moho depths for the aegean plate show that the southern part of the aegean crustal thickness of 20 22 km has been strongly influenced by extension while the northern aegean sea which at present undergoes the highest crustal deformation shows a relatively thicker crust 25 28 km this may imply a recent initiation of the present kinematics in the aegean western greece crustal thickness of 32 40 km is unaffected by the recent extension but underwent crustal thickening during the hellenides mountains building event the depths of the aegean moho beneath the margin of the peloponnesus and crete 25 28 and 25 33 km respectively show that these areas are also likely to be affected by the aegean extension even though the cyclades crustal thickness of 26 30 km were not significantly involved in this episode the aegean lithosphere asthenosphere boundary lab mapped with s receiver functions is about 150 km deep beneath mainland greece whereas the lab of the subducted african plate dips from 100 km beneath crete and the southern aegean sea to about 225 km under the volcanic arc this implies a thickness of 60 65 km for the subducted african lithosphere suggesting that the aegean lithosphere was not significantly affected by the extensional process associated with the exhumation of metamorphic core complexes in the cyclades

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

tectonic evolution of the mid polish trough modelling implications and significance for central european geology abstract the polish basin forms the easternmost part of the permian mesozoic northwest european basin the depocentral axis of the polish basin the mid polish trough mpt is superimposed on the boundary between the west european phanerozoic and east european proterozoic crustal domains within the trans european suture zone the presence of this fundamental crustal boundary may be paramount in structurally controlling the position of the mpt concentrating stresses during post variscan wrench and extensional tectonics in central europe tectonic subsidence analysis of the preserved and reconstructed stratigraphic record of the polish basin indicates the occurrence of an initial late permian early triassic 255 241 ma rifting phase that was followed by subsequent episodes of increased tectonic subsidence during the oxfordian kimmeridgian 157 152 ma and beginning in the cenomanian 97 ma the oxfordian kimmeridgian episode is interpreted as corresponding to a second extensional event which correlated with intersified rifting and wrench activity within the arctic north atlantic rift system and along the northern tethyan margin while the cenomanian may be considered a precursor of compressional deformations in the basin which culminated in basin inversion in the latest cretaceous and paleocene forward modelling results in view of existing geophysical interpretations which show the presence of a deep moho and a very velocity lower crustal layer beneath thempt suggest that permo mesozoic basic development may be related at least in part to the intrusion of mantle material into and densification of the lower crust rather than exclusively to crustal extension and thinning

new terrestrial heat flow map of europe after regional paleoclimatic correction application heat flow variations with depth in europe can be explained by a model of surface temperature changes 10 c new heat flow map of europe is based on updated database of uncorrected heat flow values to which paleoclimatic correction is applied across the continent correction is depth dependent due to a diffusive thermal transfer of the surface temperature forcing of which glacial interglacial history has the largest impact it is obvious that large part of the uncorrected heat flow values in the existing heat flow databases from wells as shallow as few hundreds of meters is underestimated this explains some very low uncorrected heat flow values 20 30 mw m2 in the shields and shallow basin areas of the craton also heat flow values in other areas including orogenic belts are likely underestimated based on the uncorrected and corrected heat flow maps using 5 km 5 km grid we have calculated average heat flow values uncorrected heat flow 56 0 mw m2 sd 20 3 mw m2 vs corrected heat flow 63 2 mw m2 sd 19 6 m wm2 and heat loss for the continental part total heat loss is 928 e09 w for the uncorrected values versus corrected 1050 e09 w

the deep crust beneath the trans european suture zone from a multiscale magnetic model we present a 3 d interpretation of the deep magnetic sources beneath the main geological structure of central eastern europe the trans european suture zone tesz we used a multiscale analysis of aeromagnetic data based on a multiscale data set generated by upward continuation of the european and mediterranean magnetic project data set from 5 to 100 km altitude we also computed the multiscale total gradient t of the multiscale field both of the multiscale data sets allow us to discriminate the main crustal contributions to the field at various scales and we showed that at large altitudes the field is dominated by the sole effect of the tesz the multiridge geometric method was very useful in studying the complex features of the main crustal interfaces either shallow or deep the interpreted interfaces are largely agreement with geological models based on seismic surveys and in some cases complete the models out of the analyzed region in order to estimate the deepest source depths in the tesz region we applied the multiridge method to the large scales 50 100 km altitude obtaining a set of singular points at depths ranging between 35 and 40 km considering the heat flow trend and the geological models around the tesz area we found a meaningful correspondence among the location of the estimated singular points and the most abrupt variations and complex morphology features of the moho boundary the multiridge estimates are consistent with known structural information and can be used for a 3 d representation of the moho depth along the tesz

upper mantle and lithospheric heterogeneities in central and eastern europe as observed by teleseismic receiver functions summary data from 90 permanent broad band stations spread over central and eastern europe were analysed using ps receiver functions to study the crustal and upper mantle structure down to the mantle transition zone receiver functions provide valuable information on structural features which are important for the resolution of european lithospheric dynamics moho depths vary from less than 25 km in extensional areas in central europe to more than 50 km at stations in eastern europe craton and beneath the alpine carpathian belt a very shallow moho depth can be observed at stations in the upper rhine graben area ca 25 km whereas for example stations in the sw bohemian massif show a significantly deeper moho interface at a depth of 38 km vp vs ratios vary between 1 60 and 1 96 and show no clear correlation to the major tectonic units thus probably representing local variations in crustal composition delayed arrivals of converted phases from the mantle transition zone are observed at many stations in central europe whereas stations in the cratonic area show earlier arrivals compared with those calculated from the iasp91 earth reference model differential delay times between the p410s and p660s phases indicate a thickened mantle transition zone beneath the eastern alps the carpathians and the northern balkan peninsula whereas the transition zone thickness in eastern and central europe agrees with the iasp91 value the thickening of the mantle transition zone beneath the eastern alps and the carpathians could be caused by cold deeply subducted oceanic slabs

an integrated study of the ne german basin abstract the ne german basin is part of the southern permian basin south of the transeuropean suture zone tesz here we report an attempt to integrate a variety of geological and geophysical data in order to reveal the present day deep crustal structure of the ne german basin special focus is taken on detailed geological information available reflection seismic data wide angle refraction seismic data and gravity data based on this integrative approach a concise crustal model is developed which can be subject to further evaluation furthermore it is shown that the ne german basin is an outstanding feature quite different from classical basin types as the moho is flat below the basin neither a simple shear nor a pure shear extension model can be applied instead a thick high velocity lower crustal layer is present below the basin centre this high velocity lower crust is also observed in the western part of the basin and can be taken as characteristic for east avalonia results of gravity modelling indicate the presence of a high density lower crust thus supporting the wide angle data furthermore changes in crustal structure can be derived from changes in reflectivity pattern and from the gravimetric signature along the elbe fault system indicating the presence of different crustal domains north and south of the fault system an elastic plate model where the forces applied are the sediment load a vertical load at the southern margin accounting for the harz moutains and a nne ssw directed compression indicates a buckling of the crust during late cretaceous to tertiary inversion however the correlation between the observed crustal structure and the tectonic events that have affected the area remains a subject of discussion a permian thermal event affected the upper mantle and the lower crust and therefore may have modified the crustal memory with regard to caledonian and variscan events additional tectonic events affected the area during the mesozoic in conclusion it remains an open question whether the high velocity and high density lower crustal structure represents a remnant of east avalonia whether it is related to the formation of the permo triassic basin or is the cumulative result of a series of events during the palaeozoic and mesozoic

a three dimensional crustal model of southwest germany derived from seismic refraction data abstract from densely covered seismic refraction data obtained in 1978 urach experiment and 1984 schwarzer zollern wald experiment and from seismic reflection data and results from previous refraction investigations a three dimensional crustal model of southwest germany was derived travel time and amplitude information of seismic refraction data were interpreted with two dimensional forward modeling ray tracing to calculate two crustal cross sections in southwest germany these results fill a gap in the existing data and enabled the construction of a detailed three dimensional crustal model while seismically the upper crust is laterally homogeneous 5 9 6 0 km s throughout the area the middle and lower crust show pronounced lateral variations in thickness velocity and reflectivity the moho is a flat surface at a relatively shallow depth 25 26 km we classify the middle and lower crust of southwest germany into two characteristic crustal types type i consists of a mid crustal low velocity zone 5 4 5 8 km s overlying a thick 10 km high velocity 6 6 6 8 km s lower crust type ii has no prominent mid crustal low velocity zone and a thin

major crustal features between the harz mountains and the baltic shield derived from receiver functions major crustal features between the harz mountains and the baltic shield derived from receiver functions

shear wave velocity and poisson s ratio structure of the upper lithosphere in southwest germany knowledge of shear wave velocity structure when used with compressional wave velocity can help constrain interpretations of composition from seismic refraction results we present shear velocity vs models from high quality s wave data from southwest germany which combine with existing p wave velocity vp models to give poisson s ratio in the crust and uppermost mantle in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust and varies laterally from 0 24 0 30 in the lower crust the average poisson s ratio for the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data suggesting strong vertical variations of poisson s ratio within the lower crust no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle we interpret these results to indicate a high quartz content or fluid phases at low pore pressure in the mid crust a high feldspar content in the lower crust and an increase in depletion of basaltic components with depth in the upper mantle

lithosphere structure along the northern part of eurobridge in lithuania results from integrated interpretation of dss and gravity data abstract in the summer of 1995 the first on shore phase of the eurobridge dss experiment took place in lithuania the quality of recordings was good and contained clear p wave reflections from inter crustal interfaces and the moho boundary very clear reflections were also registered from the interface below the moho boundary the arrivals of both reflected and refracted p waves from 10 shotpoints were processed using the seis 83 ray tracing program as a result a 2 d seismic model along the lithuanian part of eurobridge has been obtained the comparison of synthetic and experimental seismograms showed good agreement of the model with registered travel times to visualise better the existing tectonic discontinuities an integrated 2 d seismic and density model along the northern part of eurobridge was compiled for this purpose the technique of gravity data inversion based on a non linear relationship between density and seismic p wave velocity was used this integrated velocity density model helped to reveal differences in deep lithosphere structure beneath the northern part of eurobridge where the tectonic contact of two proterozoic terrains is located

blockage of regional seismic waves by the teisseyre tornquist zone summary during the group of scientific experts technical test gsett second experiment 22 april 2 june 1991 several hundred seismic events were located in europe associating these events with the detecting stations altogether 28 european stations including seven arrays participated in the gsett 2 experiment clearly shows that the teisseyre tornquist zone ttz influences the propagation of regional seismic phases large explosions in the bay of gdansk for example were observed by the wellestablished scandinavian arrays norsar a 830 km and arcess a z 1650 km but not by the polish station ksp a 470km nor by the new highly sensitive geress array a 750 km both situated south west of the ttz for events in central europe with comparable magnitudes we observe a similar increase of the detection threshold at stations located north east of the ttz in scandinavia to explain these observations the wave propagation of pn and pg perpendicular to the ttz was modelled for a profile from the estonian russian border region to geress with gaussian beam seismograms published crustal and uppermost mantle models for poland and for europe were used as a starting point for developing a model of the ttz the observations cannot be explained only by a graben like crustal structure with a jump in moho depth from 30 km to 50 km to defocus the seismic energy the ttz as a structural anomaly between eastern and western europe must reach down into the upper mantle to a depth of at least about 200 km the proposed model has such a deep reaching root of the ttz

lithosphere structure of the ne bohemian massif sudetes a teleseismic receiver function study in 2004 and 2005 a passive seismic experiment was carried out in the northern and northeastern part of the bohemian massif sudetes to study the lithospheric structure we present results from ps and sp receiver function analyses with one exception moho depth at stations in the northwestern part of the study area varies between 28 and 32 km thicker crust up to 35 km was mapped toward the south moldanubian unit and toward the east moravo silesian and brunovistulian units confirming results from previous active seismic measurements there exists a relatively sharp step in moho depth between units of the central sudetes 30 km and the moravo silesian unit 35 km the vp vs ratios inverted from primary and multiple moho ps conversions hint for different crustal compositions of the units toward the carpathian thrust we have no clear indications for any crustal root or slab beneath the western carpathians however our data suggests a deepening of the moho or at least a complicated crust mantle transition in this area additional ps phases were observed between 6 and 10 s delay time in the sudetes these phases cannot be explained by moho reverberations but are most probably caused by low velocity zones in the middle crust or lithospheric mantle as shown by modeling of theoretical receiver functions the stations showing these abnormal phases are located in the area of permo carboniferous basins on probably tepla barrandian crust therefore we assume that the phases hint at a mid crustal low velocity zone between 16 and 20 km depth which is interpreted as a felsic solidified magma reservoir of the permo carboniferous volcanism beneath the sudetic basins sp receiver functions show phases with negative polarity at 9 to 12 s lead time on average which we interpret as lithosphere asthenosphere boundary at about 80 to 110 km depth

upper mantle structure beneath the alpine orogen from high resolution teleseismic tomography 1 to understand the evolution of the alpine orogen knowledge of the actual structure of the lithosphere asthenosphere system is important we perform high resolution teleseismic tomography with manually picked p wave arrival times from seismograms recorded in the greater alpine region the resulting data set consists of 4199 relative p wave arrivals and 499 absolute p wave arrivals from 76 teleseismic events corrected for the contribution of the alpine crust to the travel times the three dimensional 3 d crustal model established from controlled source seismology data for that purpose represents the large scale alpine crustal structure absolute p wave arrival times are used to compute an initial reference model for the inversion tests with synthetic data document that the combination of nonlinear inversion high quality teleseismic data and usage of an a priori 3 d crustal model allows a reliable resolution of cells at 50 km 50 km 30 km hence structures as small as two cells can be resolved in the upper mantle our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km along strike of the alps the inversion reveals a high velocity structure that dips toward the se beneath the adriatic microplate in the western and central alps in the eastern alps we observe a northeastward dipping feature subducting beneath the european plate we interpret this feature in the western and central alps as subducted mainly continental european lower lithosphere for the east we propose that parts of the vardar oceanic basin were subducted toward the ne forcing continental adriatic lower lithosphere to subduct northeastward beneath the european plate

crustal structure of the trans european suture zone region along polonaise 97 seismic profile p4 1 the large scale polonaise 97 seismic experiment investigated the velocity structure of the crust and upper mantle in the trans european suture zone tesz region between the precambrian east european craton eec and paleozoic platform that comprises terranes added during the caledonian and variscan orogenies 530 370 and 370 225 ma respectively this experiment included 64 shots recorded by 613 seismic stations during two deployments very good quality data were recorded along five profiles and the longest and most important one p4 is the focus of this paper clear first arrivals and later phases of waves reflected refracted in the crust and moho were interpreted using two dimensional 2 d tomographic inversion and ray tracing techniques the crustal thickness along the profile varies from 30 35 km in the paleozoic platform area to 40 km below and due northeast of the tesz to 43 km in the polish part of the eec and to 50 km in lithuania the paleozoic platform and eec are divided by the polish basin so the upper crustal structure varies considerably in the area of the polish basin the p wave velocity is very low vp 6 1 km s down to depths of 15 20 km indicating that a very thick sedimentary sequence is present we suggest two possible tectonic interpretations of the velocity models 1 baltica indented avalonia obducting its upper crust and underthrusting its lower crust in a tectonic flake structure and 2 a rifted margin of baltica underlies the polish basin this model is similar to other interpretations of seismic profiles recorded in the baltic sea the second model implies that the paleozoic platform solely consists of avalonian lithosphere and the eec of baltica lithosphere it offers a simple explanation of the difference in crustal thickness of the two platforms it also implies that the caledonian and variscan orogenies in this area were relatively soft collisions that left this continental margin largely intact

imaging ruptured lithosphere beneath the red sea and arabian peninsula abstract the red sea rift an archetype of a newly formed ocean basin is an ideal environment in which to study the controversial processes associated with continental rifting different models have been proposed to explain how rifting in the red sea evolved however accurate constraints on lithospheric structure have not been available to discriminate rifting models we use the s wave receiver function technique to produce the first images of the lithosphere asthenosphere boundary lab structure along the red sea and throughout the arabian peninsula lithospheric thickness varies considerably with thin lithosphere centered on the rift axis thickening toward the arabian interior gravity data are well fit by our structural model and indicate that high surface topography along the rift flank is not in isostatic equilibrium requiring dynamic compensation for its support while our derived structure is consistent with active rifting processes previous studies demonstrated that the red sea initiated as a passive rift therefore our results suggest a two stage rifting history where extension and erosion by flow in the underlying asthenosphere are responsible for variations in lab depth lab topography guides asthenospheric flow beneath western arabia and the red sea demonstrating the important role lithospheric variations play in the thermal modification of tectonic environments

polonaise 97 an international seismic experiment between precambrian and variscan europe in poland abstract the trans european suture zone tesz comprises a series of sutures that developed by palaeozoic amalgamation of the phanerozoic central europe onto the proterozoic baltica and east european plate during the formation of pangea within tesz the permian basin in poland forms the easternmost part of the permian central european basin which is bordered on the east by the east european craton eec and on the southwest by the bohemian massif the axis of the basin the mid polish trough parallels the edge of the eec the teisseyre tornquist zone ttz is a geological inversion zone in the polish trough a large seismic experiment the polonaise 97 project was conducted in poland during may of 1997 and targeted the deep structure of the tesz and the complex series of upper crustal features associated with it it included contributions from the geophysical communities in poland denmark the usa lithuania germany finland sweden and canada this large lithospheric seismic experiment deployed 613 instruments to record 64 shots along five profiles with a total length of about 2000 km moreover five multichannel seismic reflection stations 90 and 120 channels recorded all signals from shots two dimensional velocity models were derived by p wave tomographic inversion these models provide an initial interpretation of this massive data set and allow us to present a few significant seismic and tectonic observations one of the most important is a very distinct asymmetry between the maximum thickness of the sedimentary cover in the polish trough 16 20 km and the crustal root 50 km associated with tesz ttz

evidence for a missing crustal root and a thin lithosphere beneath the central alborz by receiver function studies summary the alborz mountains build the northern part of the alpine himalayan orogen in western asia they are located south of the caspian sea and form an east west range across the north of iran this region is one of the most active tectonic areas as it undergoes extensive crustal deformation and shortening in the present work we used data from 11 permanent stations of the tehran telemetry seismic network to estimate the thickness of the crust and mantle lithosphere beneath the central alborz region by p and s receiver function methods results of both p and s receiver functions revealed a relatively large crustal thickness beneath this region 51 54 km which can be associated with the shortening process related to the orogenic belt no remarkable crustal thickening has been detected below the high topography of central alborz a thick crust 67 5 km is observed locally in the region beneath the damavand volcano which is possibly related to the magmatic addition at the base of the crust beneath the volcanic region the s receiver functions exhibit the existence of a seismic discontinuity in the upper mantle at a depth of 90 km which we interpreted as the base of the lithosphere the missing crustal root and the relatively thin lithosphere beneath the alborz may imply that sublithospheric mantle could be responsible for and support the elevation of the alborz

v p v s and lithology published laboratory investigations suggest an association exists between the ratio of seismic compressional and shear wave velocities vp vs and sedimentary rock lithology comparisons of some theoretical models with these laboratory studies suggest that crack or pore geometry has a stronger effect on observed vp vs values than elastic constants of the minerals comprising the matrix further it can be inferred that the observed association between lithology and vp vs is a result of an association between lithology and distribution of pore and crack shapes direct observation of crack shapes for a variety of lithologies is a next step in strengthening these inferences the present study reviews the empirical relations between vp vs and lithology and examines two published theoretical models of cracked elastic media the models suggest that seismic velocities of sandstones may be controlled by cracks and pores with aspect ratios in the range of 10 1 to 1 dolomite in the range of 10 2 to 10 1 and dens

origin of hydrocarbon and noble gases carbon dioxide and molecular nitrogen in devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins southern part of the upper silesian coal basin and western part of the carpathian foredeep poland abstract sixteen natural gas samples were collected from devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins from the southern area of the upper silesian coal basin uscb and western part of the carpathian foredeep cf in poland the samples were analysed for the molecular composition and stable isotope compositions of gaseous hydrocarbons ch4 c2h6 and c3h8 and co2 n2 and noble gases he ne ar kr and xe in order to reveal the origin and migration pathways of these gases hydrocarbon gases and the majority of the of co2 were generated during two stages of thermogenic processes from type ii and ii iii kerogens in the lublin basin and during both thermogenic and microbial processes in the lviv basin the thermogenic component was generated from type ii kerogen coal bed hydrocarbon gases accumulated in the pennsylvanian strata of the southern part of the uscb originated from both thermogenic and microbial processes isotopically light microbial methane may have migrated from miocene upper badenian skawina formation of the cf to carboniferous coal bearing strata and or might result from diffusion and adsorption desorption processes during the migration of thermogenic gases from deeper lying coal seams through the microporous coal structure hydrocarbon gases and carbon dioxide which accumulated in the sandstone reservoirs of upper badenian skawina formation of the western part of the cf most probably were generated from dispersed organic matter within the claystones and mudstones of these strata and at least partly migrated from the carboniferous coal bearing strata of the uscb n2 could have been produced as a result of various biogenic and abiogenic processes and contributed to the atmospheric component characteristic radiogenic 4he composition of the analysed gases suggest the accumulation of particles formed from u and th radioactive decay in the crustal gas reservoirs radiogenic 40ar and nucleogenic 21ne with abundance ratios characteristic of crustal reservoirs were also observed addition of mantle derived he to the gases from miocene strata is evident from elevated 3he 4he ratios ranging between 0 2 and 1 6 10 6 a small contribution of ne from the mantle along with he is also suggested by the slightly elevated 20ne 22ne ratios relative to atmosphere the mantle component is most likely to have migrated from the upper mantle to the gas reservoirs through the deep seated bzie czechowice fault zone

upper mantle structure across the trans european suture zone imaged by s receiver functions we present a high resolution study of the upper mantle structure of central europe including the western part of the east european platform based on s receiver functions of 345 stations a distinct contrast is found between phanerozoic europe and the east european craton across the trans european suture zone to the west a pronounced velocity reduction with depth interpreted as lithosphere asthenosphere boundary lab is found at an average depth of 90 km beneath the craton no strong and continuous lab conversion is observed instead we find a distinct velocity reduction within the lithosphere at 80 120 km depth this mid lithospheric discontinuity mld is attributed to a compositional boundary between depleted and more fertile lithosphere created by late proterozoic metasomatism a potential lab phase beneath the craton is very weak and varies in depth between 180 and 250 km consistent with a reduced velocity contrast between the lower lithosphere and the asthenosphere within the trans european suture zone lithospheric structure is characterized by strong heterogeneity a dipping or step wise increase to lab depth of 150 km is imaged from phanerozoic europe to 20 22 e whereas no direct connection to the cratonic lab or mld to the east is apparent at larger depths a positive conversion associated with the lower boundary of the asthenosphere is imaged at 210 250 km depth beneath phanerozoic europe continuing down to 300 km depth beneath the craton conversions from both 410 km and 660 km discontinuities are found at their nominal depth beneath phanerozoic europe and the discontinuity at 410 km depth can also be traced into the craton a potential negative conversion on top of the 410 km discontinuity found in migrated images is analyzed by modeling and attributed to interference with other converted phases

crustal structure variation from the precambrian to palaeozoic platforms in europe imaged by the inversion of teleseismic receiver functions project tor the tor experiment teleseismic tomography tornquist carried out in winter 1996 97 across the trans european suture zone tesz in germany denmark and sweden has collected new data to investigate the transition zone between precambrian and palaeozoic europe in this study seismograms of teleseismic earthquakes recorded by the broad band tor stations have been used to calculate the receiver functions the time domain inversion method has been applied to the receiver functions to compute s wave velocities in the crust and uppermost mantle beneath each station the results of inversion down to 60 km depth provide new independent information about the distribution of s wave velocity in this area beneath the swedish stations on baltica the thickness of the crust varies from about 45 to 50 km with mostly gradually increasing s wave velocity and no sharp discontinuities while for danish and german stations the crust is thinner 29 38 km with a sharp moho discontinuity a very distinct s wave low velocity layer was found at depth of 8 16 km in the upper crust of baltica supported by the results of refraction deep seismic sounding experiments using both p and s waves the map of v p v s ratio beneath the c 1000 km long tor profile was obtained using the v p velocity model from previous investigations the values of v p v s 1 73 were found in the uppermost crust of baltica and upper avalonian crust the low velocity layer in the upper crust of baltica is characterized by high value of v p v s 1 85 relatively low s wave velocities are observed in the lower crust of variscides v p v s 1 79 baltica v p v s 1 83 and avalonia v p v s 1 91 in the uppermost mantle v p v s values are 1 77 1 79 and 1 82 respectively

three dimensional moho topography in italy new constraints from receiver functions and controlled source seismology in complex tectonics regions seismological geophysical and geodynamic modeling require accurate definition of the moho geometry various active and passive seismic experiments performed in the central mediterranean region revealed local information on the moho depth in some cases used to produce interpolated maps in this paper we present a new and original map of the 3 d moho geometry obtained by integrating selected high quality controlled source seismic and teleseismic receiver function data the very small cell size makes the retrieved model suitable for detailed regional studies crustal corrections in teleseismic tomography advanced 3 d ray tracing in regional earthquake location and local earthquake tomography our results show the geometry of three different moho interfaces the european adriatic ionian and tyrrhenian the three distinct moho are fashioned following the alpine and apennines subduction collision and back arc spreading and show medium to high frequency topographic undulations reflecting the complexity of the geodynamic evolution

seismic receiver functions and the lithosphere asthenosphere boundary abstract the lower boundary of the lithospheric plates has remained as an enigmatic boundary for seismologists since it is relatively poorly observed by seismic means there is traditionally a broad consensus that the asthenosphere is observable as a low velocity zone by seismic surface waves seismic techniques which use shorter period p to s or s to p converted body waves are now far enough developed to be successful in observing such a low velocity zone with a higher resolution the principle of this technique the so called receiver function technique is that a strong teleseismic mother phase e g p s pp or sks incident from below on any seismic discontinuity beneath a station produces a converted phase ps or sp which indicates its depth and properties we discuss details of this technique a sufficient number of such observations exist already to indicate that the top of the low velocity zone is a globally observable discontinuity and it is sharper than previously thought an intriguing observation is that in some cratons the new seismic data indicate that the low velocity zone exists already at shallower depths than obtained from surface waves this confirms earlier results from controlled source observations thybo and perchuc 1997 we discuss possible interpretations of this shallow low velocity zone in cratonic regions

modeling the influence of moho topography on receiver functions a case study from the central hellenic subduction zone 1 pseudospectral 2d modeling of wave propagation provides a fresh look at receiver function data from the hellenic subduction zone it is shown that distinct moho topography which is suggested for this complex subduction environment from various geophysical data sets can provide a conclusive explanation for previously observed inverted moho phases in the forearc as well as for a complex sequence of apparently dipping conversions in the volcanic arc prominent effects of strongly dipping discontinuities include the change of sign in ps phases refracted past the vertical and multiple p reflections that cannot be separated from ps conversions during receiver function processing unambiguous identification of these phenomena can be hampered by poor azimuthal coverage of the data still in regions where discontinuity topography can reasonably be expected its effects should be considered when interpreting receiver functions as results might be spurious otherwise

upper mantle stratification by p and s receiver functions summary seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the graefenberg array in southern germany the anisotropic p receiver function technique kosarev et al 1984 vinnik montagner 1996 is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the sv and t components of the pds phases the summary events provide better separation of the second azimuthal harmonic than the individual events the parameters of the second harmonics of sv and t thus evaluated should be similar if they reflect the effects of azimuthal anisotropy this can be used as a criterion to identify the anisotropy to detect the sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique which can be termed the s receiver function technique it includes axis rotation to separate interfering p and s arrivals determination of the principal m component of the s wave motion deconvolution of the p components of many recordings by their respective m components and stacking of the deconvolved p components with weights depending on the level of noise and the angle between the m direction and the backazimuth of the event both techniques yield consistent results for the graefenberg array as indicated by the p receiver functions the upper layer of the mantle between the moho and 80 km depth is anisotropic with dvs vs around 0 03 and the fast direction close to 20 clockwise from north the fast direction of anisotropy below this layer is around 110 the boundary between the upper and the lower anisotropic layers is manifested by the detectable pds and sdp converted phases shear wave splitting in sks is strongly dominated by azimuthal anisotropy in the lower layer asthenosphere

p and s velocity anomalies in the upper mantle beneath europe from tomographic inversion of isc data we present a new tomographic model for p and s velocity anomalies beneath europe 30 n 55 n 5 w 40 e extending in depth up to 700 km and constrained by inversion of data from the international seismological center isc catalogue the algorithm uses the traveltimes from events located in the study area recorded by all available worldwide stations as well as times from teleseismic events recorded by european stations the events from the isc catalogue have been relocated and combined into composite events all the traveltimes were corrected for crustal structure using the reference model eucrust 07 the resulting velocity anomalies show similar large scale patterns as observed in previous studies but have a higher resolution which allows detection of some features in more detail for example it is now possible to assess the depth extension of the small slow velocity body beneath the eifel region and eger graben the p and the s model show a good consistency in the uppermost 200 km below most of the european area and in some parts even in the deeper layers e g beneath the apennines and the hellenic arc the new model provides clear images of some principal features which were previously detected in a limited number of studies while the comparison between p and s velocity anomalies provides novel constraints to address on their nature e g the gap in the adriatic plate subducted below the central southern apennines in this paper we pay special attention to testing the reliability of the results the random noise effect is evaluated using a test with independent inversion of two data subsets with odd even events the spatial resolution is estimated using different checkerboard tests furthermore we present a synthetic model with realistic patterns which reproduces after performing forward and inverse modelling the same shape and amplitudes of the anomalies as in the case of the real data inversion in this case the parameters of the model can be used to assess the amplitudes of p and s anomalies that is critical for evaluation of other petrophysical parameters temperature density composition etc in the upper mantle 2009 the authors journal compilation 2009 ras