a seismic discontinuity in the upper mantle between the eastern alps and the western carpathians constraints from wide angle reflections and geological implications abstract seismic investigation of the lithosphere by means of active source experiments is mostly confined to the crust and the moho structures in the upper mantle are more likely to be discovered by analyses of teleseismic data although these methods are restricted in their resolution capabilities the relatively rare evidence for upper mantle refractors or reflectors in active source data enables challenging and interesting studies of the lower and not so well known part of the lithosphere we present such an example from the tectonically complex region between the eastern alps and the western carpathians this area was covered by several extensive 3d wide angle reflection refraction experiments within the last decade and their layout was designed to illuminate the crustal structure and in particular the moho discontinuity in some areas reflections from below the moho are also recorded these reflections occur at recording offsets between 200 and 500 km and they are particularly strong in cross line recordings we derive a set of travel times from the data and perform a tomographic inversion for the depth and shape of the reflecting interface the inversion makes use of an existing 3d crustal model which also includes the moho topography since the upper mantle velocities are poorly constrained and the azimuthal distribution of the rays is biassed several tests are applied to investigate the reliability of possible solutions the results from the tomographic inversion indicate an overall horizontal and radially dipping reflector the average depth of the reflector is 55 km which is about 25 km below the crust mantle transition and amplitude modelling suggests that the reflecting interface represents a velocity increase the investigated area is further characterised by deep sedimentary basins high heat flow high velocities in the lower crust diffuse moho signature and a strong positive bouguer anomaly nearby xenolith outcrops exhibit a pronounced change in anisotropy and indicate the presence of two distinct layers in the lithospheric mantle whereas the deeper layer is thought to present more juvenile lithosphere derived from thermal relaxation in the post extension phase most likely the upper mantle reflector also represents this change in anisotropy though other scenarios are also possible we conclude that the entire lithosphere is significantly shaped by extensional processes which affect the area since the late oligocene early miocene

3 d modelling of the crustal s wave velocity structure from active source data application to the eastern alps and the bohemian massif summary here i present results from 3 d modelling of crustal s wave velocities in the eastern part of the eastern and southern alps and the southern part of the bohemian massif data were acquired between 2000 and 2003 during three large 3 d wide angle reflection and refraction experiments the surveys aimed at the p wave velocity structure of the crust and uppermost mantle and therefore only vertical component geophones were used nevertheless many shot gathers show strongs waves in particular refractions from the crust sg waves and reflections from the moho discontinuity sms waves compared to p wave arrivals the traveltimes of s waves can only be picked with a relatively large uncertainty furthermore approximately 80 per cent of the data represent crossline recordings on which it is more difficult to assign certain phases to the arrivals for these reasons i apply signal detection and stacking routines to put the 3 d data set to best possible use concerning the crust a smooth 3 d velocity model is based on refractions from within the crust sg whereas the crust mantle boundary is modelled by reflections sms from the moho discontinuity considering that the projects were designed for p wave studies the proposed methodology provides surprisingly detailed images s wave velocities and poisson s ratio correlate with tectonic units and show significant features in the upper crust a high poisson s ratio is observed in the moravian part of the bohemian massif in the southern alps and in the northern calcareous alps and their basement within the eastern alps the middle and lower crust are only covered in the moldanubian part of the bohemian massif where poisson s ratio is low this would favour a felsic composition the evaluation of sms waves is in accordance with previously proposed p wave velocity models which indicate a fragmentation into three crustal blocks in the centre of the eastern alps

upper crustal seismic structure of the mazury complex and mazowsze massif within east european craton in ne poland the large scale seismic experiment polonaise 97 polish lithospheric onsets an international seismic experiment was carried out in may 1997 in poland lithuania and germany its main purpose was to investigate the structure of the crust and the uppermost mantle in the region of the trans european suture zone tesz that lies between the east european craton eec and the palaeozoic platform this paper covers the interpretation of seismic data along the nw se trending 180 km long profile p5 located on the eec the recordings were of a high quality with seismic energy clearly visible along the whole profile we have not found waves refracted below the upper crust in first arrivals in the nw part of the profile we have delineated a high velocity body with the p wave velocity in the range of 6 5 6 75 km s in the upper crust it corresponds to the ketrzyn anorthosite massif within the mazury complex the mazowsze massif is rather uniformly characterized by p wave velocities 5 9 6 05 and 6 2 6 35 km s in two layers respectively sufficient s wave data were available to estimate the vp vs ratio as well as the poisson ratio being 1 80 0 277 in the high velocity body and 1 67 0 220 in the upper crust apart from the 2 d model along the profile results of 3 d modelling in the area of the p5 profile are presented using off line recordings we got p wave velocity field up to 8 km s below the p5 profile at the depth of about 40 km as well as horizontal extent of the high velocity body

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

significance of geological units of the bohemian massif czech republic as seen by ambient noise interferometry broadband recordings of 88 seismic stations distributed in the bohemian massif czech republic and covering the time period of up to 12 years were processed by a cross correlation technique all correlograms were analyzed by a novel approach to get both group and phase dispersion of rayleigh and love waves individual dispersion curves were averaged in five distinct geological units which constitute the bohemian massif saxothuringian tepla barrandean sudetes moravo silesian and moldanubian estimated error of the averaged dispersion curves are by an order smaller than the inherent variability due to the 3d distribution of seismic velocities within the units the averaged dispersion data were inverted for 1d layered velocity models including their uncertainty which are characteristic for each of the geological unit we found that overall the differences between the inverted velocity models are of similar order as the variability inside the geological units suggesting that the geological specification of the units is not fully reflected into the s wave propagation velocities on a regional scale nevertheless careful treatment of the dispersion data allowed us to identify some robust characteristics of the area the vp to vs ratio is anomalously low 1 6 for all the units the moldanubian is the most rigid and most homogeneous part of the bohemian massif middle crust in the depth range of 3 15 km is relatively homogeneous across the investigated region while both uppermost horizon 0 3 km and lower crust 15 km exhibit lower degree of homogeneity

elastic parameters of west bohemian granites under hydrostatic pressure the west bohemian seismoactive region is situated near the contact of the moldanubian bohemian and saxothuringian units in which a large volume is occupied by granitoid massifs the spatial distribution of p wave velocities and the rock fabric of five representative samples from these massifs were studied the p wave velocities were measured on spherical samples in 132 independent directions under hydrostatic pressure up to 400 mpa using the pulse transmission method the pressure of 400 mpa corresponds to a depth of about 15 km in the area under study the changes of p wave velocity were correlated with the preferred orientations of the main rock fabric elements i e rock forming minerals and microcracks the values of the p wave velocity from laboratory measurements on granite samples fit the velocity model used by seismologists in the west bohemian seismoactive region

compositional and metamorphic controls on velocity and reflectivity in the continental crust an example from the grenville province of eastern quebec we present velocity and density data for a suite of gabbros and metagabbros over a range of metamorphic grades from subgreenschist to the eclogite facies most of these rocks have a mesocratic protolith with overlapping bulk chemistry ranges providing an opportunity to investigate the systematics of mineralogy and physical properties across a wide range of metamorphic grades with minimal compositional variation in addition more mafic gabbros in the eclogite facies were also investigated in order to take into account variations in the extent of transformation of gabbro to eclogite controlled by bulk chemistry the physical properties data are used as the basis for a first order crustal model composed of granitic anorthositic and gabbroic components the objective of constructing the crustal model is to evaluate the relative contribution of compositional variation and metamorphism to the velocity density and reflectivity structure of the continental crust the model suggests that in the upper crust if fracture porosity is neglected composition dominates the velocity and density structure while in the middle and lower crust composition and metamorphism play equally important roles simulations designed to predict potential reflection coefficient size distributions for the various bulk chemistries and mineralogies in the crustal model indicate step increases in the potential for large reflection coefficients that are dominantly controlled by metamorphic grade step increases in reflectivity are predicted between the lower and upper amphibolite facies and between incompletely and completely eclogitized metagabbros in the eclogite facies we also consider several alternative mixing models which account for the effects of one of the three lithologic components occurring as isolated bodies rather than perfectly mixed with the other two components these models indicate a reduction of the potential for large reflection coefficients by as much as 50 emphasizing the importance of the degree of mixing for crustal reflectivity

plate tectonics and geochemical composition of sandstones a reply the comments of roser and korsch 1984 are related to two aspects 1 their apparent inability to reproduce the results of the discriminant scores as given in table 9 of my paper bhatia 1983 and 2 the effect of grain size on the composition of clastic sedimentary rocks the apparent discrepancy in the discriminant scores is due to their error in calculation roser and korsch 1984 calculated the discriminant scores using the volatile free averages of the published sandstone suites tabulated in tables 5 8 of my paper however the discriminant functions that i developed are based on the actual non volatilefree analyses of the sandstone suites of eastern australia thus the discriminant scores on the published averages given in table 9 of my paper were also calculated using the actual analyses and not the volatile free analyses this is mentioned in the text of my paper bhatia 1983 p 620 discriminant scores for averages of the published analyses were calculated using the unstandardized function coefficients of table 3 and the actual abundance of element oxide in the average italics added the actual average chemical analyses and the calculation of the discriminant scores for three of the suites on which significant apparent discrepancies exist are presented in table 1 as examples in the three cases presented aure trough santa ynez and the rhyolitic sand suites all the scores agree with those given in bhatia 1983 and differ significantly from those calculated by roser and korsch 1984 the incomplete published analyses certainly posed some problem due to the im

the mechanism of flow and fabric development in mechanically anisotropic trachyte lava anisotropy of magnetic susceptibility ams and electron back scattered diffraction ebsd of magnetite and sanidine fabrics throughout an eroded trachyte lava dome in tertiary volcanic province of the nw czech republic revealed two fabric types the high degree of ams fabric is associated with sanidine textural domains similar to normal kink bands type i fabric and occupies the whole body except the sw margin folded fabric and low anisotropy of ams also in the sw margin reveals sanidine alignment domains resembling reverse kink bands type ii fabric the flow of trachyte lava occurred via simultaneous slip of sanidine crystals along their 010 planes and also by readjustment of the textural domain boundaries according to the fibre slip theory this microfabric study suggests that the type ii fabrics resulted from collapse of vertically anisotropic trachyte crystal mush above the feeding conduit type i fabric is interpreted to originate from type ii fabrics by further stretching of highly attenuated fold limbs asymmetric type i fabrics along margins of the dome are related to outflow of trachyte lava away from the conduit region due to divergent flow the trachyte fabric zonality is interpreted to reflect the process of successive emplacement of progressively rotated trachyte lava lobes within a lava dome that locally preserves the collapsed and folded vertical fabrics

timing styles and kinematics of cambro ordovician extension in the tepla barrandian unit bohemian massif and its bearing on the opening of the rheic ocean this paper describes late cambrian dikes and early ordovician volcano sedimentary successions of the prague basin bohemian massif to discuss the timing and kinematics of breakup of the northern margin of gondwana andesitic dikes indicate minor e w crustal extension in the late cambrian whereas the tremadocian to dapingian lithofacies distribution and linear array of depocenters suggest opening of this rheic ocean rift related basin during nw se pure shear dominated extension this kinematic change was associated with the onset of basic submarine volcanism presumably resulting from decompression mantle melting as the amount of extension increased we conclude from these inferences and from a comparison with other avalonian cadomian terranes that the rifting along the northern gondwana margin was a two stage process involving one major pulse of terrane detachment in the early cambrian and one in the early ordovician while the geodynamic cause for the former phase remains unclear but still may include effects of cadomian subduction roll back slab break off isostatic rebound or mantle plume the incipient stage of the latter phase may have been triggered by the onset of subduction of the iapetus ocean at around 510 ma followed by advanced extension broadly coeval tremadocian to darriwilian in large portions of the avalonian cadomian belt unequal amounts of extension resulted in the separation and drift of some terranes while other portions of the belt remained adjacent to gondwana

discovery of the first quaternary maar in the bohemian massif central europe based on combined geophysical and geological surveys abstract based on results of previous investigations of tephra tuff volcaniclastic deposits and a geophysical survey in the surroundings of the elezna h rka quaternary volcano west bohemia we performed detailed geophysical surveys using gravimetry magnetometry and electrical conductivity techniques striking anomalies were revealed in a morphological depression near m tina west bohemia as a strong evidence of the assumed maar diatreme structure the sharp isometric gravity low of 2 30 mgal as well as the corresponding positive magnetic anomaly of 200 nt with a negative rim on its northern side indicate a steeply dipping geological body of low density and containing magnetic rocks minerals magnetic survey also showed pronounced local anomalies outside the depression that can reflect relicts of the tephra rim of the maar this geophysical evidence was then proven by an exploratory drilling near the centre of the gravity anomaly macroscopic on site evaluation of the core and more detailed sedimentological petrochemical palynological and microbiological laboratory analyses further confirmed the existence of a maar structure filled by 84 m of lake sediments reflecting a succession of several warm and cold climatic periods results of palynological analyses confirm the presence of a continuous palaeoclimate archive with at least three successive warmer periods of most probably interstadial character from the upper quaternary saalian complex therefore the recovered sediment sequence holds strong potential for in depth paleoclimate reconstruction and deep biosphere studies at the bottom of the m tina 1 my 1 borehole 84 85 5 m country rock debris was found containing also volcanic bombs and lapilli the discovered volcanic structure is considered to be the first known quaternary maar diatreme volcano on the territory of the bohemian massif because of hidden active magmatic processes in combination with earthquake swarm seismicity ca 20 30 km north of the m tina maar reconstruction of the palaeovolcanological evolution is important for evaluation of hazard potential of the ne and e part of the cheb basin

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

lithospheric structure of the bohemian massif and adjacent variscan belt in central europe based on profile s01 from the sudetes 2003 experiment 1 the sudetes 2003 seismic experiment investigated the lithospheric structure of the eastern part of the variscan belt of central europe the key profile of this experiment s01 was 630 km long and extended southwestward from the margin of the east european craton across the trans european suture zone tesz and sudetes and across the bohemian massif that contains the active eger ohre rift which is an element of the european cenozoic rift system good quality first arrivals and later phases of refracted reflected p and s waves were interpreted using 2 d ray tracing techniques the derived seismic model shows large variations in the internal structure of the crust while the depth to the moho varies in the relatively narrow depth interval of 28 35 km except for the polish basin on the northeast end of the profile the sedimentary cover is thin the crystalline upper and middle crust with velocities of 5 9 6 4 km s 1 is about 20 km thick and the 7 10 km thick lower crust can be divided into three regions based on p wave velocities a low velocity region 6 5 6 6 km s 1 beneath eger rift and sudetes that is bounded on the southwest and northeast by regions of significantly higher velocity 6 8 7 1 km s 1 beneath the saxothuringian and moldanubian in the southwest and fore sudetic monocline and polish basin in the northeast high velocity bodies vp 6 5 km s 1 were delineated in the upper crust of the eger rift region the seismic structure along the s01 profile images a variscan orogenic wedge resting on the down warped margin of the plate margin containing the tesz this situation implies the northerly directed subduction of the rheic ocean that existed between the southern margin of the old red continent and the armorican terranes presently accreted into the variscan belt closure of this ocean produced the rheic suture between low velocity crust of the variscan orogenic wedge and higher velocity crust of the tesz

regional ambient noise tomography in the eastern alps of europe we present results from ambient noise tomography applied to temporary seismological stations in the easternmost part of the alps and their transition to the adjacent tectonic provinces vienna basin bohemian massif southern alps dinarides by turning each station into a virtual source we recover surface waves in the frequency range between 0 1 and 0 6 hz which are sensitive to depths of approximately 2 15 km the utilization of horizontal components allows for the analysis of both rayleigh and love waves with comparable signal to noise ratio measured group wave dispersion curves between stations are mapped to local cells by means of a simultaneous inverse reconstruction technique the spatial reconstruction for love wave velocities fails in the central part of the investigated area and we speculate that a heterogeneous noise source distribution is the cause for the failure otherwise the obtained group velocity maps correlate well with surface geology inversion of rayleigh wave velocities for shear wave velocities along a vertical n s section stretching from the bohemian massif through the central alps to the southern alps and dinarides reveals a mid crustal low velocity anomaly at the contact between the bohemian massif and the alps which shows a spatial correlation with the p wave velocity structure and the low frequency component of the magnetic anomaly map our study is validated by the analysis of resolution and accuracy and we further compare the result to shear wave velocity models estimated from other active and passive experiments in the area

emplacement dynamics of phonolite magma into maar diatreme structures correlation of field thermal modeling and ams analogue modeling data abstract emplacement mode and original shape and dimensions of a well exposed phonolite body in the ceske st edoho i mountains czech republic were reconstructed using combined techniques of structural analysis of magmatic fabrics and columnar jointing together with analogue and thermal mathematical modeling of cooling for different shapes of experimental bodies phreatomagmatic rocks in the vicinity of some phonolite stocks in the area of interest suggest that the phonolite bodies were likely emplaced into maar diatremes our modeling revealed that intrusion of magma into phreatomagmatic maar diatreme craters can result in cryptodomes extrusive domes lava lakes or branched intrusions the fabric and columnar jointing pattern of the selected phonolite body reveals best fit with an asymmetric extrusive dome emplaced into the maar crater the scaling analysis and thermal modeling also suggest that the phonolite extrusion could have formed within 6 66 days and cooled to the background temperature after 10 000 years combined analogue and thermal modeling also revealed that the phonolite extrusions into maar diatreme craters are marked by upper tier collonade of vertical columns and lower tier of curved and outward flaring columns both tiers in the phonolite extrusions are divided by a subhorizontal suture

azimuthal variation of pg velocity in the moldanubian czech republic observations based on a multi azimuthal common shot experiment westudytheazimuthalvelocityvariationofpg wavesinthemoldanubian whichisacrystallinesegmentwithinthebohemian massif in the czech republic we use the data from a multi azimuthal common shot experiment performed as part of the alp 2002 refraction experiment complemented by profile refraction data from the celebration 2000 experiment we analyze the traveltimesofwavesrecordedby72portableseismicstationsdeployedalongtwocircleswithradiiof35and45kmaroundashot the observed travel times display an azimuthal variation indicating anisotropy of 2 the minimum and maximum velocity values are 5 83 and 5 95 km s respectively the direction of the maximum velocity is n508e these values characterize horizontal anisotropy of the uppermost crust down to 3 km the strength and orientation of uppermost crustal anisotropy in the moldanubian is consistent with the overall upper crustal anisotropy in the entire bohemian massif the high velocity direction is roughly perpendicular to the present day maximum compressive stress in the bohemian massif and central europe and coincides with the orientation of structures formed by the main variscan tectonic events in the area this indicates that the anisotropy is caused predominantly by alignment of textural elements and minerals in the rocks which developed in early geological stages

three dimensional s wave velocity model of the bohemian massif from bayesian ambient noise tomography abstract we perform two step surface wave tomography of phase velocity dispersion curves obtained by ambient noise cross correlations in the bohemian massif in the first step the inter station dispersion curves were inverted for each period ranging between 4 and 20 s separately into phase velocity maps using 2d adjoint method in the second step we perform bayesian inversion of the set of the phase velocity maps into an s wave velocity model to sample the posterior probability density function the parallel tempering algorithm is employed providing over 1 million models from the model samples not only mean model but also its uncertainty is determined to appraise the reliable features the model is correlated with known main geologic structures of the bohemian massif the uppermost low velocity anomalies are in agreement with thick sedimentary basins in deeper parts 4 20 km the s wave velocity anomalies correspond in general to main tectonic domains of the bohemian massif the exception is a stable low velocity body in the middle of the high velocity moldanubian domain and high velocity body resembling a promontory of the moldanubian into the tepla barrandian domain the most pronounced high velocity anomaly is located beneath the eger rift that is a part of a tertiary rift system across europe

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

magnetotelluric study of the eastern margin of the bohemian massif relations between the cadomian variscan and alpine orogeny eastern margin of the bohemian massif is a geologically remarkable area where three different orogenic cycles are meeting the oldest cadomian building a basement for younger cycles a younger variscan and the youngest alpine covering the older units in the past this area was investigated by gravimetry and seismic methods recently we have supplemented broadband magnetotelluric measurements within the period range of 0 001 1000 s carried out on 29 stations distributed along a 140 km long west east regional profile the profile direction was based on local geology and then confirmed by a dimensionality and directionality analysis data showed moderate effects of cultural noise in the signals and could be successfully processed by robust methods we carried out a 2d inversion of the data using the rebocc approach the inversion results confirm the known near surface geology and reveal deeper structures on the west and in the central part of the profile units of the bohemian massif the moldanubian zone the brunovistulicum are interpreted in the east the western carpathians units are encountered short period data agree well with the known near surface geology of all inner smaller units and bring new knowledge in particular on their thickness in the shallow structure several conductive anomalies have been identified which are hypothesized to be related to graphitized layers in the moldanubian zone from long period data a new image of the moldanubian brunovistulicum contact and about the structure of the brunovistulicum especially the brunovistulian massifs was obtained

from the variscan to the alpine orogeny crustal structure of the bohemian massif and the western carpathians in the light of the sudetes 2003 seismic data summary the variscan orogeny is the major middle to late palaeozoic tectonometamorphic event in central europe and the bohemian massif is the largest exposure of rocks deformed during this orogeny the bohemian massif consists of the saxothuringian barrandian and moldanubian units adjacent to this massif in the southeast the western carpathians form an arc shaped mountain range related to the alpine orogeny during the cretaceous to tertiary the complex crustal scale geological structure of the variscan bohemian massif and the western carpathians and especially their contact were analysed in this study employing the data of the sudetes 2003 international seismic refraction experiment the analysed seismic data were acquired along the 740 km long nw se oriented s04 profile that crossed the bohemian massif and the western carpathians before terminating in the pannonian basin the data were interpreted by 2 d trial and error forward modelling of p waves and additional constraints on crustal structure were provided by gravity modelling the complex velocity structure derived in our analysis included low velocities of 5 85 km s 1 at the contact of the saxothuringian and barrandian units that reflect the presence of low density granites there are distinct lateral variations in deep crustal structure in the transition between the bohemian massif and the western carpathians the abrupt change of the crustal thickness in this transition zone may be associated with the pieniny klippen belt a deep seated boundary between the colliding palaeozoic lithospheric plate to the north and the alcapa microplate to the south in the upper crust of this transition low velocities of 4 km s 1 extend to 6 km and represent the sedimentary fill of the carpathian flysch and foredeep that thins towards the foreland this basin is also expressed as a pronounced gravity low the moho in the carpathians reaches a depth of 32 33 km in contrast in the pannonian basin the moho rises to a depth of 25 km which corresponds to the pannonian gravity high

toward source region tomography with intersource interferometry shear wave velocity from 2018 west bohemia swarm earthquakes the concept of seismic interferometry embraces the construction of waves traveling between receivers or sources with cross correlation techniques in the present study cross correlations of coda waves are used to measure traveltimes of shear waves between earthquake locations for five event clusters of the 2018 west bohemia earthquake swarm with the help of a high quality earthquake catalog i was able to determine the shear wave velocity in the region of the five clusters separately the shear wave velocities range between 3 5 and 4 2 km s the resolution of this novel method is given by the extent of the clusters and better than for a comparable classical tomography it is suggested to use the method in a tomographic inversion and map the shear wave velocity in the source region with unprecedented resolution furthermore the influence of focal mechanisms and the attenuation properties on the polarity and location of the maxima in the cross correlation functions is discussed the intracluster ratio of p wave to s wave velocity is approximately fixed at 1 68

cenozoic volcanism in the bohemian massif in the context of p and s velocity high resolution teleseismic tomography of the upper mantle

accretionary history and crustal evolution of the variscan belt in western europe abstract the variscan belt of western europe is part of a large intra paleozoic belt extending on both sides of the atlantic from the ouachitas in the us and the mauritanides in west africa to the bohemian massif in czechoslovakia and poland the belt was constructed between 500 and 250 ma as a result of convergence and collision between two main continents laurentia baltica and africa after the closure of various oceanic basins iapetus rheic and galicia massif central now recorded as discrete in part cryptic sutures which form the roots of large crystalline nappes in which are found dismembered remnants of oceanic crust and mantle the accretionary history of the variscan belt in western europe is related to the progressive closure of probably two oceanic basins the rheic in the north and another the galicia massif central in the south by respectively southward and northward intraoceanic subduction followed by obduction and intracontinental lithospheric subduction the result is a broad 700 800 km fan like divergent belt which must be considered as a classical obduction collision orogen with a long intracontinental history of about 100 150 ma its arcuate shape is probably due to the northwestward impingement of a promontory of the african continent into laurentia baltica

crustal structure of the eastern alps and their foreland seismic model beneath the cel10 alp04 profile and tectonic implications summary the subject of this paper concerns the seismic modelling of the crustal structure in the transition zone from the bohemian massif across the molasse basin and the eastern alps to the southern alps mainly on the territory of austria the cel10 alp04 profile crosses the triple point of the european plate adriatic microplate and the recently identified pannonian fragment the seismic data along the presented profile originate from two large experiments celebration 2000 and alp 2002 the wavefield observed in the eastern alps is more complex than in the bohemian massif strong first arrivals pg are distinct up to 60 90 km offset and are characterized by large variations in apparent velocity and amplitude the contact between the molasse basin and the eastern alps represents a barrier for seismic waves midcrustal reflections pc are usually recorded at short distance intervals 20 50 km and are also characterized by variations in apparent velocity and amplitude the moho reflections are usually strong and well correlated while pn arrivals are only fragmentarily recorded detailed 2 d forward modelling of all refracted post critical and reflected phases identified in the correlation process was undertaken using a ray tracing technique the p wave velocity in the crystalline upper crust of the bohemian massif and molasse basin is about 6 15 km s 1 which is slightly higher than in the alpine area about 6 0 km s 1 below the northern accretionary wedge of the eastern alps low velocity sediments penetrate towards the southwest sw down to about 10 km depth in the middle crust of the alpine part a reflective zone was modelled by a lamellae structure with alternating high and low velocities and thicknesses of about 2 3 km the lower crust in this part of the model is more homogeneous with a velocity of about 6 9 km s 1 in the bohemian massif a high velocity hv body vp 7k m s 1 o f af ew kilometres thickness was delineated in the depth interval 18 23 km the crustal thickness along the cel10 alp04 profile changes from about 42 44 km in the sw alpine part to around 40 km in the central part of the profile molasse basin and 38 40 km in the ne bohemian massif the velocity in the uppermost mantle determined from pn wave traveltimes is about 8k m s 1 along the whole profile the interpretation of the seismic wavefield is supplemented by an existing 3 d p wave velocity model of the area main features derived by 2 d modelling low velocities beneath the accretionary wedge high velocities in the lower crust of the bohemian massif moho topography well correlate with the 3 d model furthermore the 3 d model allows assessing the lateral extent of significant features alongside the cel10 alp04 profile this area is affected by both collision and escape tectonics the high reflectivity zone

late variscan strike slip tectonics between the tepla barrandian and moldanubian terranes czech bohemian massif petrostructural evidence in the variscan bohemian massif czech republic no agreement has been reached on the nature of the relationship between the tepla barrandian and the moldanubian terranes however the tepla barrandian is interpreted as a central segment separating the moldanubian and saxothuringian terranes and its position is therefore essential for any reconstruction of this part of the variscan belt our petrological and structural study in the domazlice klatovy region spans the boundary between the tepla barrandian and moldanubian terranes there is no conformity of ductile structures in both domains near their interface and their p t evolution is separate in time the development of major structures and associated metamorphism in the southwestern part of the barrandian was accompanied by syntectonic intrusions of granitoid and diorite bodies dated at about 520 ma the moldanubian migmatites are characterized by a lp ht metamorphism that possibly took place at about 320 ma the metamorphic record of the barrandian rocks shows no influence of the moldanubian partial melting the contacts are marked by semi brittle to brittle structures sinistral strike slip faulting developed in the central bohemian shear zone whereas the west bohemian shear zone acted as a semi brittle normal fault with a dextral component both shear zones may be nearly contemporaneous accommodating a bulk n s compression the central bohemian shear zone was later reactivated in a dextral regime although timing is uncertain the juxtaposition of both terranes took place probably in the waning stages of the variscan orogeny earlier than the late stephanian we argue that the late orogenic semi brittle strike slip tectonics modified considerably the face of the bohemian massif and the geodynamic models of the bohemian massif have to be reviewed with reference to this essential point

shape and origin of the east alpine slab constrained by the alpass teleseismic model abstract during the last two decades teleseismic studies yielded valuable information on the structure of the upper mantle below the alpine mediterranean area subducted oceanic lithosphere forms a broad anomaly resting on but not penetrating the 670 km discontinuity more shallow slabs imaged below the alpine arc are interpreted as subducted continental lower lithosphere substantial advances in our understanding of past and active tectonic processes have been achieved due to these results however important issues like the polarity of subduction under the eastern alps and the slab geometry at the transition to the pannonian realm are still under debate the alpass teleseismic experiment was designed to address these open questions teleseismic waveforms from 80 earthquakes recorded at 75 temporary and 79 permanent stations were collected during 2005 and 2006 from these data a tomographic image of the upper mantle was generated between 60 km and 500 km depth crustal corrections additional station terms and ray bending caused by the velocity perturbations were considered a steeply to vertically dipping shallow slab below the eastern alps is clearly resolved down to a depth of 250 km it is interpreted as european lower lithosphere detached from the crust and subducted during post collision convergence between adria and europe below the pannonian realm low velocities or high mantle temperatures prevail down to 300 km depth consistent with the concept of a pannonian lithospheric fragment which underwent strike slip deformation relative to the european plate and extension during the post collision phase of the alpine orogeny between 350 km and 400 km depth a deep slab extends from below the central eastern alps to under the pannonian realm it is interpreted as subducted lithosphere of the alpine tethys at greater depth there is a continuous transition to the high velocity anomaly above the 670 km discontinuity

the uncertainty of 2d models along wide angle seismic profiles the estimation of uncertainty for any geophysical model is important for determining how reliable the model is it is especially important for subjective trial and error modelling techniques like forward ray tracing modelling of wide angle seismic data when the final result is very dependent on the interpreter s knowledge of the area and experience in this kind of modelling it is common to encounter over interpretation of the seismic data without checking the uncertainty of the result especially in the deep parts that are not constrained with other a priori knowledge in this paper we propose a method of estimating the uncertainty of the final models based on a one dimensional method of small error propagation generalized for 2d profiles with a simple approximation we estimate the uncertainty for published interpretative models of selected profiles from seismic experiments in the central europe we conclude that for typical wide angle seismic profiles we can reliably interpret four layered models of the earth s crust based on traveltimes fitting we also show how the number of layers influence obtained uncertainties estimated uncertainties for both the velocity fields and the boundaries between layers are important for future tectonic and geodynamic interpretation of those profiles

crustal anisotropy in the bohemian massif czech republic observations based on central european lithospheric experiment based on refraction celebration 2000 1 we study the azimuthal velocity variation of pg waves in the bohemian massif using data collected during central european lithospheric experiment based on refraction celebration 2000 we analyze travel times of waves generated by 28 shots and recorded by 256 portable and 19 permanent seismic stations deployed on the territory of the czech republic and in adjacent areas we use recording offset ranging from 30 to 190 km with azimuths covering the whole interval of angles the observed travel times are inverted for parameters of a velocity model formed by an isotropic low velocity subsurface layer with a varying depth lying on a homogeneous transversely isotropic half space with a horizontal axis of symmetry the recovered velocity displays a systematic azimuthal variation indicating a regional scale intrinsic or effective anisotropy in the bohemian massif the mean minimum and maximum values of the velocity are vmean 6 03 km s vmin 5 98 km s vmax 6 10 km s respectively indicating an anisotropy of 1 5 2 5 the direction of the maximum propagation velocity is n35 e being approximately perpendicular to the present maximum compression in the earth crust in central europe the observed anisotropy cannot be induced by stress aligned cracks in the crust because the crack models predict azimuthal velocity variations completely inconsistent with the observed one therefore we suggest the crustal anisotropy to be induced by a preferred orientation of rock forming minerals and large scale intrusion fabrics developed during a tectonic evolution of the bohemian massif

3d structure of the earth s crust beneath the northern part of the bohemian massif abstract the sudetes 2003 wide angle refraction reflection experiment covered the area of the south western poland and the northern bohemian massif the good quality data that were gathered combined with the data from previous experiments polonaise 97 celebration 2000 allowed us to prepare a 3d seismic model of the crust and uppermost mantle for this area we inverted travel times of both refracted and reflected p waves using the jive3d package this allowed us to obtain a model of p wave velocity distribution as well as the shape of major boundaries in the crust we also present a detailed uncertainty analysis for both the boundary depths and the velocity field in doing the uncertainty analysis we found an interesting strong dependence between uncertainty and inversion scheme order of used phases we also compared the model with surface geology and found good correlation between velocity inhomogeneities in the uppermost crust down to 2 km and major geological units the higher velocity lower crust 6 9 7 2 km s could result from remelting of the lower crust or magmatic underplating

refraction seismic investigations of the northern massif central france abstract new refraction seismic data have been obtained in the northern french massif central seven shots were recorded simultaneously on two parallel nnw sse i e perpendicular to the surface structures oriented profiles allowing for inline and fan interpretations the results of a 2d interpretation reveal a large scale updoming of the moho of about 2 km compared to average western europe corresponding to the cenozoic uplift of the massif central local crustal thinning of up to 20 is restricted to the cenozoic grabens as seen at the surface beneath the volcanic area of cantal one of the largest cenozoic european shield volcanoes which was active in miocene to recent times significant crustal thickening of 2 3 km is observed velocities in the upper mantle are generally in the range of 7 9 8 1 km s beneath the limagne graben and surrounding undisturbed areas underneath the volcanic area of cezallier however velocity is reduced to about 7 7 km s corresponding to the area of crustal thickening therefore the low velocity in this zone is explained by the remainders of cooling magma chambers and heating by ascending hot plume material the cenozoic tectonic evolution of the massif central has affected crust and upper mantle in different ways oligocene rifting corresponds well to local crustal thinning but no correlation is detected to velocities of the upper mantle in contrast the volanic event occurring since miocene times is related to upper mantle velocity reduction and crustal thickening due to underplating

drainage evolution in the polish sudeten foreland in the context of european fluvial archives detailed study of subsurface deposits in the polish sudeten foreland particularly with reference to provenance data has revealed that an extensive preglacial drainage system developed there in the pliocene early pleistocene with both similarities and differences in comparison with the present day odra oder system this foreland is at the northern edge of an intensely deformed upland metamorphosed during the variscan orogeny with faulted horsts and grabens reactivated in the late cenozoic the main arm of preglacial drainage of this area at least until the early middle pleistocene was the palaeo nysa klodzka precursor of the odra left bank tributary of that name significant preglacial evolution of this drainage system can be demonstrated including incision into the landscape prior to its disruption by glaciation in the elsterian sanian and again in the early saalian odranian which resulted in burial of the preglacial fluvial archives by glacial and fluvioglacial deposits no later ice sheets reached the area in which the modern drainage pattern became established the rivers incising afresh into the landscape and forming post saalian terrace systems issues of compatibility of this record with the progressive uplift implicit in the formation of conventional terrace systems are examined with particular reference to crustal properties which are shown to have had an important influence on landscape and drainage evolution in the region

lower crustal petrology from wide angle p and s wave measurements in the black forest abstract the lower crust of the black forest in southwest germany is strongly reflective for compressional waves but almost non reflective for shear waves if the reflectivity for p waves is caused by alternating high and low velocity rocks the s wave observations require that the low velocity rocks have a low poisson s ratio and vice versa a purely compositional petrological model for lower crustal rocks can fit the observed p and s wave velocity data provided a rather high quartz content 50 is acceptable for the lower crust

links between the structure of the mantle lithosphere and morphology of the cheb basin eger rift central europe the cheb basin chb located in the western part of the eger rift er and the western bohemian massif is characterized by earthquake swarms neotectonic crust movements and emanations of co2 dominated gases of mantle origin deep structure of the region can be characterized as junction of three domains of mantle lithosphere with different olivine fabrics revealed by consistent orientations of seismic anisotropy the domains represent mantle components of the major tectonic units micro plates saxothuringian st tepla barrandian tb and moldanubian md which were assembled during the variscan orogeny the st tb boundary reactivated during the cenozoic extension controlled the position and development of the er and the chb we show that the chb originated above the rejuvenated mantle suture between the st and tb though the basin is located within the st crust domain which is thrust over the mantle junction it is the mantle suture that controls the chb shape and its development through the allochthonous st crust the seismically active marianske lazn fault limits the basin against the uplifted block of the erzgebirge crystalline complex the most subsided parts of the er and chb developed above the centre of the mantle transition whereas a well expressed morphology developed above its flanks our study documents a long memory of the mantle lithosphere assembly inherited from the variscan orogeny it is possible that other continental regions also contain some of intra plate basins that originated above healed palaeo plate mantle boundaries

upper lithospheric seismic velocity structure across the pripyat trough and the ukrainian shield along the eurobridge 97 profile abstract we present new results on the structure resulting from palaeoproterozoic terrane accretion and later formation of one of the aulacogens in the east european platform seismic data has been acquired along the 530 km long n s striking eurobridge 97 traverse across sarmatia a major crustal segment of the east european craton the profile extends across the ukrainian shield from the devonian pripyat trough across the palaeoproterozoic volyn block and the korosten pluton into the archaean podolian block seismic waves from chemical explosions at 18 shot points at approximately 30 km intervals were recorded in two deployments by 120 mobile three component seismographs at 3 4 km nominal station spacing the data has been interpreted by use of two dimensional tomographic travel time inversion and ray trace modelling the high data quality allows modelling of the p and s wave velocity structure along the profile there are pronounced differences in seismic velocity structure of the crust and uppermost mantle between the three main tectonic provinces traversed by the profile i the pripyat trough is a ca 4 km deep sedimentary basin fully located in the osnitsk mikashevichi igneous belt in the northern part of the profile the velocity structure is typical for a precambrian craton but is underlain by a ca 5 km thick lowest crustal layer of high velocity the development of the pripyat trough appears to have only affected the upper crust without noticeable thinning of the whole crust this may be explained by a rheologically strong lithosphere at the time of formation of the trough ii very high seismic velocity and vp vs ratio characterise the volyn block and korosten pluton to a depth of 15 km and probably also the lowest crust the values are consistent with an intrusive body of mafic composition in the upper crust that formed from bimodal melts derived from the mantle and the lower crust iii the podolian block is close to a typical cratonic velocity structure although it is characterised by relatively low seismic velocity and vp vs ratio a pronounced sw dipping mantle reflector from moho to at least 70 km depth may represent the proterozoic suture between sarmatia and volgo uralia the structure from terrane accretion or a later shear zone in the upper mantle the sub moho p wave seismic velocity is high everywhere along the profile with the exception of the area above the dipping reflector this velocity change further supports a plate tectonic origin of the dipping mantle reflector the profile demonstrates that structure from palaeoproterozoic plate tectonic processes are still identifiable in the lithosphere even where younger metamorphic equilibration of the crust has taken place

active magmatic underplating in western eger rift central europe the eger rift is an active element of the european cenozoic rift system associated with intense cenozoic intraplate alkaline volcanism and system of sedimentary basins the intracontinental cheb basin at its western part displays geodynamic activity with fluid emanations persistent seismicity cenozoic volcanism and neotectonic crustal movements at the intersections of major intraplate faults in this paper we study detailed geometry of the crust mantle boundary and its possible origin in the western eger rift we review existing seismic and seismological studies provide new interpretation of the reflection profile 9hr and supplement it by new results from local seismicity we identify significant lateral variations of the high velocity lower crust and relate them to the distribution and chemical status of mantle derived fluids and to xenolith studies from corresponding depths new interpretation based on combined seismic and isotope study points to a local scale magmatic emplacement at the base of the continental crust within a new rift environment this concept of magmatic underplating is supported by detecting two types of the lower crust a high velocity lower crust with pronounced reflectivity and a high velocity reflection free lower crust the character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events the lower crust with high reflectivity evidences magmatic underplating west of the eger rift of the late variscan age the reflection free lower crust together with a strong reflector at its top at depths of 28 30 km forms a magma body indicating magmatic underplating of the late cenozoic middle and upper miocene to recent spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting

structural model for the saxothuringian moldanubian suture in the variscan basement of the oberpfalz northeastern bavaria f r g interpreted from geophysical data abstract the moldanubian saxothuringian boundary marks a prominent subduction zone in the internal parts of the european variscides in the oberpfalz area deep reflection seismic profiles show a high density of various reflectors mainly in the upper crust indicating a complex polyphase deformation during the collision process seismic structures and related data from surface geology suggest that the moldanubian saxothuringian collision consisted of two main phases the first phase is marked by extensive nw directed overthrusting of moldanubian onto saxothuringian crust along se dipping master decollements some of which can be traced down to the moho during an advanced stage progressive overthrusting led to the development of wedge structures associated with se directed backthrusting and backfolding in the upper structural levels subsequently some of these wedges and their related decollements were folded to form the main ne striking anticlines the first phase of crustal imbrication correlates with a regional low pressure high temperature metamorphism at about 320 ma decreasing in grade northwestward the second phase is characterized by a reorientation of the main direction of crustal shortening from nw se to sw ne which is interpreted as the result of the n directed indentation of the vindelician terrane into the moldanubian this event is recorded by conjugate systems of overthrusting and subsequent strike slip faulting in the oberpfalz and the bavarian forest and the black forest vosges area in the area of the southern german block between these basement outcrops the indentation front is marked by the arc shaped axes of gravimetric and magnetic anomalies and permo carboniferous troughs

a crustal model for the eastern alps region and a new moho map in southeastern europe in the last two decades south central europe and the eastern alps have been widely explored by many seismic refraction experiments e g celebration 2000 alp 2002 sudetes 2003 although quite detailed images are available along linear profiles a comprehensive three dimensional crustal model of the region is still missing this limitation makes this region a weak spot in continental wide comprehensive representations of crustal structure to improve on this situation we select and collect 37 published active source seismic lines in this region after geo referencing each line we sample them along vertical profiles every 50 km or less along the line and derive p wave velocities in a stack of homogeneous layers separated by discontinuities depth of crystalline basement top of lower crust and moho we finally merge the information using geostatistical methods and infer s wave velocity and density using empirical scaling relations we present here the resulting crustal model for a region encompassing the eastern alps dinarides pannonian basin western carpathians and bohemian massif covering the region within 45 circ text 51 circ hbox n and 11 circ text 22 circ hbox e with a resolution of 0 2 circ times 0 2 circ we are also able to extend and update the map of moho depth in a wider region within 35 circ text 51 circ hbox n and 12 circ text 45 circ hbox e gathering moho values from the collected seismic lines other published dataset and using the european plate reference epcrust as a background all the digitized profiles and the resulting model are available online

seismic structure of the palaeozoic platform along polonaise 97 profile p1 in northwestern poland abstract the deep seismic profile p1 was conducted in northwestern poland as part of the polonaise 97 project data acquisition involved 100 mobile seismographs which recorded seismic waves from 11 dispersed chemical controlled explosions along this 300 km long profile a variety of seismic modelling techniques were employed to derive a velocity model along the profile this model indicates that the mesozoic and palaeozoic sediments are 6 km thick in the northwest and 3 km thick in the southeast with the main thickness variation taking place in the palaeozoic succession an undulating basement surface indicates tectonic activity during deposition of the lower palaeozoic sequence the crust is 30 33 km thick along the profile thickening gradually to the southeast the p wave seismic velocities are low 1 down to a depth of 20 km along the whole profile which we interpret as evidence for their being of sedimentary or volcanic origin the lower crust has a high p wave velocity 6 7 7 5 km s 1 high vertical velocity gradient and strong ringing reflectivity the velocity of the sub moho mantle p n is high 8 2 km s 1 features similar to the ones below this profile have been interpreted for the area south of the caledonian deformation front in northern germany and southern denmark these similarities indicate that the crust between the southeastern north sea and poland has a common origin we therefore suggest that the deep crust beneath the profile is not of variscan origin despite its location south of the variscan deformation front we propose that variscan tectonism in the area was thin skinned while the deeper crust may originate from the caledonian microcontinent east avalonia or possibly from baltica

a wide angle seismic traverse through the variscan of southwest ireland summary a wide angle seismic profile across the western peninsulas of sw ireland was performed this region corresponds to the northernmost variscan thrust and fold deformation the dense set of 13 shots and 109 stations along the 120 km long profile provides a detailed velocity model of the crust the seismic velocity model obtained by forward and inverse modelling defines a five layer crust a sedimentary layer 5 8 km thick is underlain by an upper crustal layer of variable thickness with a base generally at a depth of 10 12 km two midcrustal layers are defined and a lower crustal layer below 22 km the moho lies at a depth of 30 32 km a low velocity zone which coincides with a well defined gravity low is observed in the central part of the region and is modelled as a caledonian granite which intruded upper crustal basement the granite may have acted as a buver to northward directed variscan thrusting the dingle dungarvan line ddl marks a major change in sedimentary and crustal velocity and structure it lies immediately to the north of the velocity and gravity low and shows thickness and velocity diverences in many of the underlying crustal layers and even in the moho this suggests a deep pre variscan control of the structural development of this area the model is compatible with thin skinned tectonics which terminated at the ddl and which incorporated thrusts involving the sedimentary and upper crustal layers

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

possible role of fluids in the process of earthquake swarm generation in the west bohemia vogtland seismoactive region abstract the west bohemia vogtland region in the western part of the bohemian massif known for periodic occurrence of earthquake swarms is also characterised by 0 2 0 5 ma old quaternary volcanoes rich co2 emissions anomalies of mantle derived he mineral springs and moffets the detailed analysis of the time space pattern of seismicity during the january 1997 swarm demonstrates the gradual and ordered migration of micro seismic activity suggesting the step by step penetration of fluids into a small fractured volume this scenario is supported by the similarity of the source mechanisms of the natural events of the january 1997 swarm with artificial injection induced micro earthquakes during the german deep drilling project ktb in neighbouring ne bavaria also the comparison of the west bohemia vogtland earthquake swarm region with other intraplate earthquake swarm regions and with earthquake swarms induced by current volcanic processes indicates a role of intrusions of magma and related fluids in generation process of earthquake swarms

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

crustal structure at the easternmost termination of the variscan belt based on celebration 2000 and alp 2002 data abstract the eastern margin of the variscan belt in europe comprises plate boundaries between continental blocks and terranes formed during different tectonic events the crustal structure of that complicated area was studied using the data of the international refraction experiments celebration 2000 and alp 2002 the seismic data were acquired along sw ne oriented refraction and wide angle reflection profiles cel10 and alp04 starting in the eastern alps passing through the moravo silesian zone of the bohemian massif and the fore sudetic monocline and terminating in the tesz in poland the data were interpreted by seismic tomographic inversion and by 2 d trial and error forward modelling of the p waves velocity models determine different types of the crust mantle transition reflecting variable crustal thickness and delimiting contacts of tectonic units in depth in the alpine area few km thick lvz with the vp of 5 1 km s 1 dipping to the sw and outcropping at the surface represents the molasse and helvetic flysch sediments overthrust by the northern calcareous alps with higher velocities in the bohemian massif lower velocities in the range of 5 0 5 6 km s 1 down to a depth of 5 km might represent the se termination of the elbe fault zone the fore sudetic monocline and the tesz are covered by sediments with the velocities in the range of 3 6 5 5 km s 1 to the maximum depth of 15 km beneath the mid polish trough the moho in the eastern alps is dipping to the sw reaching the depth of 43 45 km the lower crust at the eastern margin of the bohemian massif is characterized by elevated velocities and high vp gradient which seems to be a characteristic feature of the moravo silesian slightly different properties in the moravian and silesian units might be attributed to varying distances of the profile from the moldanubian thrust front as well as a different type of contact of the brunia with the moldanubian and its northern root sector the moho beneath the fore sudetic monocline is the most pronounced and is interpreted as the first order discontinuity at a depth of 30 km

towards understanding the lithospheric structure of the southern chilean subduction zone 36 s 42 s and its role in the gravity field summary the southern andes differ significantly from the central andes with respect to topography and crustal structures and are from a geophysical point of view less well known in order to provide insight into the along strike segmentation of the andean mountain belt an integrated 3 d density model was developed for the area between latitudes 36 s and 42 s the model is based on geophysical and geological data acquired in the region over the past years and was constructed using forward density modelling in general the gravity field of the south american margin is characterized by a relatively continuous positive anomaly along the coastline and the forearc region and by negative anomalies along the trench and the volcanic arc however in the forearc region of the central part of the study area located just to the south of the epicentre of the largest ever recorded earthquake valdivia 1960 the trench parallel positive anomaly is disrupted the forearc gravity anomaly differences thus allow the study area to be

moho depth determination from waveforms of microearthquakes in the west bohemia vogtland swarm area 1 the west bohemia vogtland area is known for its increased geodynamic activity with reoccurrence of intraplate earthquake swarms previous geophysical studies namely active and passive seismic investigations revealed a high velocity lower crust in this area with increased reflectivity to refine this result and retrieve a more detailed structure of the deep crust and the moho discontinuity we analyzed waveforms of local microearthquakes that occurred in this area during the 2008 swarm the waveforms of earthquakes were grouped into clusters with similar focal mechanisms and the clusters were processed separately we developed a new multiazimuthal approach in data processing to increase resolution of moho phases in the waveforms we applied the waveform cross correlation of the p and s waves and rotated aligned and stacked the seismograms to extract the moho sms pmp and pms reflected converted phases these phases were inverted for laterally varying moho depth by ray tracing and a grid search inversion algorithm the model retrieved was verified using modeling of full waveforms computed by the discrete wave number method the multiazimuthal approach reveals details in the velocity structure of the crust mantle transition at each station instead of a single interface with a sharp velocity contrast the inversion indicates a reflective zone at moho depths with one or two strongly reflective interfaces which is in agreement with the zone interpreted by previous investigations the thickness of the zone varies from 2 to 4 km within the depth range of 27 31 5 km and is delimited by reflections from its top and bottom boundaries sometimes with strong reflectors within the zone the average vp vs ratio determined from the moho reflections and conversions is 1 73

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

basalts water or shear zones in the lower continental crust abstract bright sub horizontal laterally extensive multi cyclic layered reflections have now been recorded in the lower continental crust from many areas in contrast this reflection signature is rare in the continental upper crystalline crust and upper mantle and in the oceanic lithosphere with the present state of knowledge it is sensible to seek a single quantitative explanation for all such layering qualitative explanations for lower crustal layering abound and include igneous metamorphic structural and fluid related models measurements of reflection coefficients from the lower crust place strong quantitative constraints on possible models structurally induced anisotropy metamorphic layering or free fluids cannot realistically produce sufficiently bright reflections igneous layering or the juxtaposition of pre existing heterogeneities by shear zones can produce strong reflections results from crustal xenoliths helium isotope ratios palaeo geothermal gradients and chemistry of flood basalts together with numerical modelling of lithospheric extension and asthenospheric melting suggest that underplating and intrusion of the lower crust with mantle derived mafic igneous rocks is common the apparent spatial relationship between lower crustal layering and continental extension and the strength and continuity of the reflections suggest that underplating related to extension and or elevated mantle temperatures is a good explanation for lower crustal layering

the refraction seismic experiment granu95 in the saxothuringian belt southeastern germany summary in this paper we present newly acquired high quality wide angle seismic data of the granu95 project and first models of the crustal structure along two profiles 95 a and 95 b beneath the saxonian granulites a major ellipse shaped exposure of lower crustal material within the mid european variscan belt in southeastern germany saxony the crust is subdivided into four layers the crystalline basement with velocities higher than 6 0 km s 1 is generally reached at shallow depths with three major sedimentary structures as prominent exceptions where velocities considerably lower than 6 0 km s 1 as low as 5 1 km s 1 reach as deep as 4 km the highest upper crustal velocities up to 6 5 km s 1 are not seen below the exposed granulites themselves but at shallow depths 4 km sw of the exposure these shallow high velocities correlate well in depth with highly reflective zones observed on three seismic reflection lines of dekorp 85 4n 95 01 95 02 at their intersection with the seismic refraction line 95 b where they appear as a set of nw se trending dome shaped reflections on profile 95 a this high velocity uppercrustal layer 6 3 km s 1 dips from 5 to 9 km beneath the se margin of the exposed granulites these results suggest that the granulite dome and its western continuation are widely underlain by a ne trending antiformal structure probably a sheet of metabasic rocks where the exposed felsic granulites form just a local cap on top below the upper crustal high velocities a layer with decreased velocity 6 2 6 25 km s 1 extends down to an average depth of 15 km along the variscan strike 95 b and to 11 16 km depth slightly dipping towards the se perpendicular to the terrane boundaries 95 a at mid crustal levels a weak reflection from a layer with a velocity of 6 4 6 6 km s 1 may indicate the classical conrad discontinuity at the depth range 22 24 km the velocity jumps to an average value of 7 0 km s 1 thus defining a prominent high velocity layer in the lower crust which may be viewed as the well known laminated lower crust typical of variscan structures but with higher average velocity than usually detected the crust mantle boundary at about 30 31 km is typical for western europe and confirms the extensional signature of the west european crust below the moho poorly constrained upper mantle velocities of about 7 9 8 0 km s 1 are derived the high velocities observed in the lower crustal layer would not exclude the possibility of mantlederived intrusions but the lack of any sign of an updoming moho favours the interpretation of a more passively driven extension

magnetic fabric and petrology of miocene sub volcanic sills and dykes emplaced into the sw flysch belt of the west carpathians s moravia czech republic and their volcanological and tectonic implications abstract magnetic fabrics were investigated in the sub volcanic bodies occurring within the sw flysch belt of the western carpathians magnetite or low ti titanomagnetite is the principal carrier of the anisotropy of magnetic susceptibility ams in these rocks though various fe ti oxides were also identified in minor amounts the magnetic fabric in almost all sills and dykes is conformable to the shapes of the bodies and no doubt originated through more or less free magma flow that requires relatively open voids to be injected that likely originated in an extensive tectonic regime in an ankaramite sill where the rock creates typical hexagonal columns the magnetic fabric is related rather to the column axes than to the overall shape of the sill the magnetic fabric formation in this sill is controlled by the post emplacement process of the creation of the columns at some studied localities signs of post magmatic middle miocene tectonic deformation are observed in the field the youngest known in the flysch belt as the magnetic fabric is unrelated to those signs we conclude that these young tectonic movements did not penetrate ductilely in the volume of the volcanic body it seems that the strain was focused to thin zones along the faults since it did not change the preferred orientation of magnetic minerals in the rock volume substantially

application of stacking and inversion techniques to three dimensional wide angle reflection and refraction seismic data of the eastern alps summary we present new methods for the interpretation of 3 d seismic wide angle reflection and refraction data with application to data acquired during the experiments celebration 2000 and alp 2002 in the area of the eastern alps and their transition to the surrounding tectonic provinces bohemian massif carpathians pannonian domain dinarides data was acquired on a net of arbitrarily oriented seismic lines by simultaneous recording on all lines of seismic waves from the shots which allows 2 d and 3 d interpretations much 80 of the data set consists of crossline traces low signal to noise s n ratio in the area of the young orogens decreases the quality of travel time picks in these seismically heterogeneous areas it is difficult to assign clearly defined arrivals to the seismic phases in particular on crossline record sections in order to enhance the s n ratio signal detection and stacking techniques have been applied to enhance the pg pn and pmp phases further inversion methods have been developed for the interpretation of war r data based on automated 1 d inversion pg and the application of the delay time concept pn the results include a 3 d velocity model of the crust based on pg waves time and depth maps of the moho and a pn velocity map the models based on stacked data are robust and provide a larger coverage than models based on travel time picks from single fold unstacked traces but have relatively low resolution especially near the surface they were used as the basis for constructing models with improved resolution by the inversion of picks from single fold data the results correlate well with geological structures and show new prominent features in the eastern alps area and their surrounds the velocity distribution in the crust has strong lateral variations and the moho in the investigation area appears to be fragmented into three parts

tio2nanoparticle trails in garnet implications of inclusion pressure induced microcracks and spontaneous metamorphic reaction healing during exhumation a new mechanism of cleaving healing of garnet in metamorphic rocks during exhumation is reported almandine garnet with submicron multiple phase inclusions characteristic of the grail reaction garnet rutile kyanite ilmenite low quartz was found by analytical electron microscopy to have non epitaxial rutile nanoparticles distributed along internal 110 microcrack trails at the acute corner of submicron multiple phase inclusions defined by the intersecting 110 and 011 mould surfaces such garnet microcracks were formed during lithostatic decompression due to a relatively high compressibility of quartz in the inclusion pockets and stress concentration at the acute corner spontaneous healing with accompanied formation of non epitaxial rutile nanoparticles was activated predominantly via the grail reaction due to high surface tension at the tip of microcracks and to a lesser extent decreasing lithostatic pressure or increasing inclusion pressure upon exhumation this new mechanism of microcracking and healing involves stress build up fracture propagation mineral reaction transport of elements to the reaction site and lowering of reaction boundaries by capillarity effect all under the influence of thermodynamic and kinetic factors at the submicron scale thus tio2 nanoparticle trails in garnet provide additional information on the p t path and may shed light on exhumation rates mechanisms and metamorphic reactions processes careful scrutiny of host minerals on the submicron scale is required to tell whether there are other metamorphic reaction facilitated healing processes being overlooked by inappropriate techniques or being obliterated by the predominant healing processes of fluid infiltration and resorption zoning

geophysical evidence for early permian igneous activity in a transtensional environment denmark abstract integrated interpretation of gravity magnetic and seismic data in the area of the strong silkeborg gravity high in central denmark has led to a structural geological model involving a transtensional rift feature which probably formed in connection with permo carboniferous wrench faulting and the development of the oslo horn graben system reinterpretation of the deep seismic data from profile 2 of the eugeno s project in the area of the silkeborg gravity high detected a new thin high velocity layer 6 25 km s at about 7 km deep within the palaeozoic sedimentary sequence in the crystalline basement a separate body of high velocity 6 9 7 0 km s was found at 11 km deep beneath this body the moho reaches its shallowest position in the area the seismic results compare well with an interpretation based on magnetism of a shallow volcanic or subvolcanic layer at a depth of 6 8 km this layer shows strong remanent and induced magnetization with a southward inclination of about 10 gravity reinterpretation of the area allows the separation of an upper body of density contrast 0 1 g cm3 from a lower body of density contrast 0 2 g cm3 the upper body roughly coincides with the magnetic body the lower body the major one coincides with the deep seismic body and it is responsible for the main gravity anomaly in the area

a geophysical model of the variscan orogenic root bohemian massif implications for modern collisional orogens abstract a new model of the structure and composition of the variscan crust in the bohemian massif is proposed based on 3d gravity modelling geological data seismic refraction cel09 and reflection 9hr sections the bohemian massif crust is characterized by a succession of positive and negative anomalies of about 60 80 km wavelength for nearly constant moho depths the south western part of the bohemian massif displays a large negative bouguer anomaly corresponding to high grade rocks granulites and migmatites of the palaeozoic crustal root represented by the moldanubian domain the adjacent neo proterozoic bruno vistulian microcontinent displays an important gravity high reflecting mafic and intermediate medium grade metamorphic and magmatic rocks the deep crustal boundary between the root domain and the bruno vistulian microcontinent is represented by a strong gradient located 50 to 70 km westwards from the surface boundary between these units indicating that the high density basement rocks are covered by a thin sheet of low density granulites and migmatites north west from the moldanubian domain occurs an important gravity high corresponding to the neo proterozoic basement of the tepla barrandian unit limited in the north by southeast dipping reflectors of the tepla suture which is characterized by high density eclogites and ultramafics the footwall of the suture corresponds to low density felsic crust of the saxothuringian basement the reflection and refraction seismics and gravity modelling suggest a complex lithological structure of the moldanubian domain marked by a low density 5 10 km thick lower crustal layer located above the moho a 5 10 km thick heavy mafic layer a 10 km thick mid crustal layer of intermediate density and a locally developed 2 5 km thick low density layer at the surface the low density lower crust correlates well with low p wave velocities in the range 6 0 6 4 km s 1 in the cel09 section this complex geophysical structure and surface geology are interpreted as a result of carboniferous partial overturn of low density lower crust and high and intermediate density crust in the area of central root and by viscous extrusion of low density orogenic lower crust over the high density bruno vistulian continent comparison of these data with geophysical profiling of the andean and the tibetan plateaus suggests that modern orogenic systems reveal comparable deep crustal geophysical pattern based on these similarities we propose that the variscan root represents a deep crustal section of above mentioned plateaus which may have develop by the same orogenic process

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 beneath the eger rift central europe plume or asthenosphere upwelling summary we present the first results of a high resolution teleseismic traveltime tomography and seismic anisotropy study of the lithosphere asthenosphere system beneath the western bohemian massif the initial high resolution tomography down to a depth of 250 km did not image any columnar low velocity anomaly which could be interpreted as a mantle plume anticipated beneath the eger rift similar to recent findings of small plumes beneath the french massif central and the eifel in germany alternatively we interpret the broad low velocity anomaly beneath the eger rift by an upwelling of the lithosphere asthenosphere transition we also map lateral variations of seismic anisotropy of the mantle lithosphere from spatial variations of p wave delay times and the shear wave splitting three major domains characterised by different orientations of seismic anisotropy correspond to the major tectonic units saxothuringian moldanubian and the tepla barrandian and their fabrics fit to those found in our previous studies of mantle anisotropy on large european scales

three dimensional seismic modelling of the crustal structure between east european craton and the carpathians in se poland based on celebration 2000 data summary in this paper we present results of 3 d first arrival tomography applied to data recorded in se poland during the celebration 2000 seismic experiment the target area covers ca 500 500 km 2 and represents a complex geological setting from old precambrian platform east european craton eec through the crustal blocks terranes that form the transeuropean suture zone tesz to the young alpine orogen the carpathians contrasting velocity distributions in various geological units makes the tomographic inversion challenging for this reason much attention was paid to the inversion methodology we tested multioffset and multiscale approaches by increasing the offset range in the multioffset inversion we have independently constrained different depth ranges of our model we have found that the multiscale method that is the gradual stepping from bigger to smaller model cells produced the preferred solution resolution of the resultant crustal model was determined by performing checkerboard and restoration resolution tests lateral resolution of the order of 25 km is inferred down to 10 km depth and 50 km down to 25 30 km depth we have also applied a quasi monte carlo analysis to determine the absolute errors of model parameters which to our knowledge is the first such attempt in case of a 3 d wide angle data set the mean uncertainties of our tomographic velocities are 0 1 km s 1 but some anomalies are recovered with

p and s wave velocity model of the southwestern margin of the precambrian east european craton polonaise 97 profile p3 the large scale seismic experiment polonaise 97 investigated the seismic structure of the crust and the uppermost mantle in the polish region of the trans european suture zone this paper covers the interpretation of seismic data along the 300 km long p3 profile which is located in the precambrian east european craton eec parallel to the teisseyre tornquist zone the recordings were of high quality with seismic energy detectable out to 300 km ovsets the crustal model developed by two dimensional raytracing forward modelling and waveform analysis is characterized by a subhorizontal uniform structure although the boundaries of several large basement features are crossed the crystalline crust consists of three parts the upper middle and lower crust with p wave velocities of 6 1 6 4 km s 6 55 6 7 km s and 7 05 7 15 km s respectively the p m p wave can usually be correlated at distances beginning at about 100 km but it has variable reflection character moho depth increases from 38 km at the nw end of the profile to 44 km at the se end the p n velocity of 8 05 8 1 km s is less than that previously found in neighbouring areas of the eec the v p v s ratio was determined separately for the upper middle and lower crust to be 1 67 and 1 77 respectively following the p n wave another phase with an apparent velocity of about 8 3 km si s interpreted as a weak reflection from a low contrast discontinuity in the uppermost mantle 1999 elsevier science b v all rights reserved

2 d seismic tomographic and ray tracing modelling of the crustal structure across the sudetes mountains basing on sudetes 2003 experiment data the seismic data obtained during sudetes 2003 experiment are analysed and detailed crustal structure for profiles s02 s03 and s06 is presented using three different 2 d techniques 1 smooth tomography of refracted waves travel times 2 ray tracing of reflected and refracted waves and 3 joint velocity and depth of reflector tomographic inversion in spite of different interpretation techniques used the models of the crustal structure show common characteristic features the low velocity vp 4 km s sedimentary layer was documented in the northeastern part of the study area the topmost basement has in general a velocity of 5 8 6 0 km s and velocities at ca 20 km depth are 6 15 6 25 km s the strong reflecting boundaries were found at 20 23 and 25 28 km depth with a velocity contrast about 0 4 km s and the highest velocities in the lowermost crust are 6 8 7 2 km s in general the crust of the bohemian massif is slightly thicker 33 35 km than in the northern part of the area velocities beneath moho are relatively low of 7 95 km s on the basis of well recorded reflected waves mantle reflectors were discovered in the depth interval ca 40 70 km apart of new results for the geology and tectonics of the area some conclusion could be made about different techniques used in the 2 d case the clasical ray tracing method with using all correlated phases gives the most adequate model of the structure because of full manual control of the model creation the smooth first arrival travel times tomography although very fast is not satisfactory enough to describe the complex structure so the best candidate in 3 d case seems to be travel time tomography for both refracted and reflected waves in multi layers models

a successive three point perturbation method for fast ray tracing in complex 2d and 3d geological models abstract this paper presents new 2d and 3d ray tracing methods that can be applied to traveltime and ray path computations for transmitted reflected and turning seismic waves in complex geologic models the new ray tracing scheme combines segmentally iterative ray tracing sirt and pseudo bending methods to address both stratified and arbitrarily shaped block models the new method robustly extends our previous constant block models and constant gradient block models to generally heterogeneous block models and incorporates cubic splines or triangulated interfaces to boundaries of complex geological bodies the method is thus more widely applicable to practical problems a successive three point perturbation scheme is formulated that iteratively updates the midpoints of a segment based on an initial ray path the midpoints are corrected by applying first order analytic formulae to locations of the midpoint inside the block or on the boundaries of the blocks which are then updated with the pseudo bending method and sirt algorithm instead of the traditional iterative methods empirical applications including an example addressing the bohemian massif demonstrate that this successive three point perturbation scheme successfully performs kinematic ray tracing in heterogeneous complex 2d and 3d media

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

model of syn convergent extrusion of orogenic lower crust in the core of the variscan belt implications for exhumation of high pressure rocks in large hot orogens reflection seismic section field structural analysis and gravimetric modelling of orogenic lower crust in the core of a carboniferous orogenic root reveal details of the polyphase process of exhumation subvertical amphibolite facies fabrics strike parallel to former plate margins that collided in the nw the fabrics are developed in both mid crustal and lower crustal high pressure granulite units as a result of intensive nw se intraroot horizontal shortening driven probably by the west directed collision in granulites the steep fabrics originated as a result of extrusion of orogenic lower crust in a 20 km wide vertical ascent channel from lower crustal depths at 350 340 ma the large granulite bodies preserve older granulite facies fabrics documenting a two stage evolution during the exhumation process surface exposures of granulites coincide with the absence of subhorizontal seismic reflectors at depth suggesting preservation of the 20 km wide subvertical tabular structure reaching moho depths horizontal seismic reflectors surrounding the vertical channel structure corroborate a dominant flat migmatitic fabric developed in all tectonic units this structural pattern is interpreted in terms of subhorizontal spreading of partially molten orogenic lower crust in mid crustal levels 765 c and 0 76 gpa at 342 337 ma large massifs of extruded and progressively dismembered felsic granulites disturbed mid crustal fabrics in the surrounding horizontally flowing partially molten crust the horizontal mid crustal flow resulted in collapse of the supra crustal tepla barrandian unit interpreted as the orogenic lid along a large scale crustal detachment above the extruded lower crustal dome the presence of felsic granulites at the bottom of the orogenic root is considered to be a key factor controlling the exhumation of orogenic lower crust in large hot orogens

lateral displacement of crustal units relative to underlying mantle lithosphere example from the bohemian massif abstract we propose a mechanical model of deformation of the entire lithosphere of the bohemian massif bm whose core is formed by an asymmetric block of the tepla barrandian tb unit in between the saxothuringian st and moldanubian md units for the modelling we have re processed p wave travel times recorded during the last two decades at dense networks of seismic stations installed in the bm during several passive seismic experiments we also use previous results of anisotropic studies based on splitting of teleseismic shear waves this allows us to refine estimates of the lithosphere thickness and delimit deep margins of the individual mantle lithosphere domains the domains are rigid enough to preserve pre orogenic olivine fabrics differently oriented in each of the units shapes and dips of the mantle boundaries representing major zones of weakness inherited from the variscan amalgamation of independent microplates indicate that north westward subductions beneath the tb unit dominated tectonic development of the core of the bm two mantle lithosphere domains with different fabric orientations separated by a wsw ene striking shear zone underlie the tb crust the nw domain is the tb mantle lithosphere while the se domain is the md mantle lithosphere thrust under the tb crust lithosphere of the north western tb domain compressed between early variscan subductions of the st continental lithosphere from the northwest and the md continental lithosphere from the southeast was pushed south westward by about 50 km though the crust of the south westerly tb promontory is commonly attributed to the md unit apparently it preserves the tb mantle lithosphere the shifted tb lithosphere provides compelling evidence in support of older views suggesting that the zone erbendorf vohenstrauss zev originally belonged to the tilted western rim of the tb unit during the final phase of the assemblage of the bm the rigid tb lithosphere was disrupted by the southward pushing st lithosphere along the newly formed nw se striking jachymov fault zone jfz this lithosphere scale process most likely changed the tectonic regime released subduction related forces and started the gravity dominated tectonics