the southern caspian a compressional depression floored by a trapped modified oceanic crust the south caspian intracontinental depression floored by oceanic basement is a relatively stable block with minor deformation surrounded by active fold thrust belts of arcuate form talesh alborz and kopeh dagh mountains which have undergone intense late cainozoic crustal shortening the basin is interpreted as a neogene quaternary compressional depression bounded by multi role mountain bordering reverse faults and apparently floored by a late paleozoic triassic or late mesozoic early tertiary modified oceanic crust trapped along an old geosuture it may be a relic of an old paleozoic triassic ocean or else a marginal sea developed behind a mesozoic paleogene ocean and analysis of geological and geophysical data enables a scheme to be suggested the general arcuate shape of the alborz and the talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south caspian depression a tectono sedimentary study of the south caspian region coupled w

flexural plate subsidence sedimentation rates and structural development of the super deep south caspian basin abstract on a 270 km long seismic line across the west central and central parts of the south caspian basin an inverse flexural plate method is used to recover original uploaded plate parameters the original plate shows remarkable consistency of parameters determined from the 12 second deep seismic line with average rigidity d 1023 6nm bending moment m 1016n dip angle 0 14 and in line compressive stress of 1012 3n m 1 by sequentially adding the sedimentary units to the average bare basement it is shown that the geometry of the basin at jurassic time had a major downward warp and high sedimentary fill to the west leaving the eastern section open to possible erosion during early and middle cretaceous time the deep western part of the basin was then filled by sediments during late tertiary quaternary time and a new depocenter created across the central and western parts of the basin this newer depocenter was then filled during pliocene quaternary time the combined flexure of the basement plate and corresponding sediment fill behaviors with time are indicative of corresponding lithologic variations across the basin and with suspected organic rich sediments the integrated description of basement sediments and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution the value of rigidity is comparable to estimated oceanic crust values in line with the suspected tethys oceanic fragment of an island arc below the sediments the shift in depositional behavior with time from west to more northerly across the line of section is tied to the orogenic rise of the caucasus mountains to the north of the section and to the continued subduction of the talysh vandam plate fragment northward today the transpressional nature of the basin and the resolution of the in line compressive stress into components perpendicular to the great caucasus 70 and also perpendicular to the west caspian deep laid fault 25 30 are both in accord with the 25 30 km of present day sedimentary cover including the variations of thicknesses of seismic stratigraphic units along the section from azerbaijan in the west to nearly the turkmenian border in the east

onset of subduction as the cause of rapid pliocene quaternary subsidence in the south caspian basin backstripping a representative stratigraphic column from the northwest of the south caspian basin shows that 2 4 km of tectonic subsidence has occurred since ca 5 5 ma at 1 5 10 times the rate recorded in typical foreland basins roughly half the basin s sedimentary thickness of 20 km has accumulated in this time while the upper part of the succession has begun to deform by buckle folding the south caspian basement appears to be either thick oceanic crust or thinned high velocity continental crust seismicity and gravity data indicate that the basement is in the initial stages of subduction under the middle caspian region to the north we propose that basement subduction began ca 5 5 ma to create the major pliocene quaternary subsidence subduction may have been triggered by a regional reorganization in the arabia eurasia collision at that time possibly following the construction of the turkish iranian plateau

repeatability issues of 3 d vsp data increased repeatability is recognized as one major issue for improving the time lapse seismic technology as a reservoir management tool a 3 d vertical seismic profiling vsp data set acquired over a period of two days is used to analyze how repeatable a permanent installed geophone array can be and how repeatability changes with inaccuracies in source positioning it is found that for a frequency range between 3 5 and 50 hz the difference root mean square rms level between two recorded traces belonging to two different shots is about 8 this fact shows that there is a potential for acquiring very accurate time lapse seismic data by using a permanently installed downhole geophone array repeatability variation with increasing shot separation distances is analyzed showing a rapid decrease in repeatability as the accuracy of the positioning of the repeat survey decreases horizontal geophone components show approximately the same degree of repeatability compared to the vertical component but horizontal geophone data is slightly more sensitive to positioning errors the results show that repeated 3 d vsp surveys preferably using permanently installed geophone arrays might be an efficient tool for detailed and precise monitoring of fluid and pressure changes within a hydrocarbon reservoir

lower lithospheric structure beneath the trans european suture zone from polonaise 97 seismic profiles abstract the large scale polonaise 97 seismic experiment investigated the velocity structure of the lithosphere in the trans european suture zone tesz region between the precambrian east european craton eec and palaeozoic platform pp in the area of the polish basin the p wave velocity is very low vp 8 25 km s in the palaeozoic platform and 8 1 km s in the precambrian platform good quality record sections were obtained to the longest offsets of about 600 km from the shot points with clear first arrivals and later phases of waves reflected refracted in the lower lithosphere two dimensional interpretation of the reversed system of travel times constrains a series of reflectors in the depth range of 50 90 km a seismic reflector appears as a general feature at around 10 km depth below moho in the area independent of the actual depth to the moho and sub moho seismic velocity ringing reflections are explained by relatively small scale heterogeneities beneath the depth interval from 90 to 110 km qualitative interpretation of the observed wave field shows a differentiation of the reflectivity in the lower lithosphere the seismic reflectivity of the uppermost mantle is stronger beneath the palaeozoic platform and tesz than the east european platform the deepest interpreted seismic reflector with zone of high reflectivity may mark a change in upper mantle structure from an upper zone characterised by seismic scatterers of small vertical dimension to a lower zone with vertically larger seismic scatterers possible caused by inclusions of partial melt

seismic models of the lower lithosphere beneath the southern baltic sea between sweden and poland abstract based on recordings from the northern part of the baltic sea black sea profile and eugeno s profile 4 2 d seismic models have been constructed for a profile across the southwestern part of the east european platform from southern sweden to northern poland the thickness of the crust along the profile varies from 33 to 47 km the moho p wave velocity is 8 0 8 3 km s the uppermost mantle has a fine structure with alternating layers of higher and lower velocities down to a depth of about 120 km three alternating high and low velocity layers have been modelled the velocities vary between 8 2 and 8 7 km s in the high velocity layers and 8 0 and 8 5 km s in the low velocity layers a tendency of the depth of the moho and the depth of the uppermost mantle seismic boundaries to increase towards the southeast is observed

a new model of upper mantle p wave velocity below the baltic shield indication of partial melt in the 95 to 160 km depth range abstract the subcrustal mantle to about a depth of 160 km below the baltic shield can be divided seismically into two main intervals the upper interval between ca 45 and 100 km is characterized by refracted waves with velocities between 8 0 and 8 6 km s interpreted as a sandwich layered model of intermixed high and low velocity layers the lower interval is a ca 40 km thick zone of relatively low average velocity at a depth increasing from 95 km in the southern part to 120 km in the northern part of the shield seismic sections show that isolated bodies in this interval generate scattered reflections with substantial amplitude variation over short distance the maximum velocity difference at the reflectors is 1 0 km s which is larger than in the upper main interval our model is based on a general gap in correlation of seismic arrivals at offsets between 800 and 1100 km at larger offsets we observe continuous linear first arrivals indicating a relatively homogenous layer of high 8 6 km s velocity below a depth of 160 km petrologically the lower reflective interval is explained by partially melted small bodies with patches of carbonatitic or kimberlitic magma of horizontal extent less than 20 km this new model of the upper mantle is based on seismic data from the baltic shield and there is clear indication that it is equally valid for other shield and platform areas

crustal scale structure of the south caspian basin revealed by deep seismic reflection profiling abstract two deep seismic reflection profiles from the south caspian basin provide the first normal incidence image of possibly the thickest sedimentary basin in the world significant features imaged with these seismic data are 1 a series of high amplitude folds developed within a thick 10 km neogene sedimentary section bounded discordantly below by 2 a gently n dipping intermittent reflection at 14 20 km 8 0 s 3 a prominent deep reflector at 26 28 km depth 12 8 13 0 s with a gentle northward dip 4 an underlying layered interval with discernibly lower frequency reflections down to 36 40 km 16 0 16 5 s and 5 a noticeable decrease in reflectivity below 36 40 km based on the downward termination of fault cored folds and their discordance with subhorizontal underlying reflections the reflection at 14 20 km is interpreted to be the basal detachment for structures associated with the absheron ridge the bright reflection at 26 28 km depth is interpreted as the basement cover contact and the underlying 10 km portion of the section is interpreted as crystalline basement downward diminution of reflectivity at 36 40 km is thought to represent the moho despite the absence of a clearly reflective horizon these interpretations are consistent with previous velocity models from both seismic refraction and teleseismic studies in the south caspian region that suggested a minimum sedimentary thickness of 20 km and a crustal thickness of 35 40 km both the apparent lack of local structural relief on the basement reflector and seismic velocities vp 6 8 km s obtained from earlier studies suggest this crust is not thinned continental material although thicker than typical oceanic crust 6 8 km the apparent 10 km thickness of the south caspian crystalline crust is interpreted to be of oceanic affinity for this part of the basin active seismicity down to mantle depths 80 km and gentle deepening of the crust from south to north suggest northward subduction of the south caspian oceanic lithosphere beneath the continental lithosphere of the central caspian basin

deep structure of the east european platform according to seismic data abstract the paper presents a review and analysis of new seismic data related to the structure of the mantle beneath the east european platform analysis of observations of long range profiles revealed pronounced differences in the structure of the lower lithosphere beneath the russian plate and the north caspian coastal depression the highest p velocities found at depths around 100 km are in the range 8 4 8 5 km s 1 deep structure of the baltic shield is different from the structures of both these regions no evidence of azimuthal anisotropy in the upper mantle was found a distribution of p velocity in the upper mantle and in the transition zone consistent with accurate travel time data was determined the model involves several zones of small and large positive velocity gradients in the upper mantle rapid increases of velocity near 400 and 640 km depths and an almost constant positive velocity gradient between the 400 and 640 km discontinuities the depth of the 640 km discontinuity was determined from observations of waves converted from p to sv in the mantle

the moho depth distribution in fennoscandia and the regional tectonic evolution from archean to permian times abstract from a variety of seismic refraction and reflection profiling results a new detailed moho depth map for the fennoscandian part of the baltic shield has been compiled a complementary crystalline crustal thickness map was compiled for denmark the skagerrak sea offshore western norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more these maps are discussed in relation to tectonic evolution and crustal ages of fennoscandia seismic velocities bouguer gravity and seismicity areas deviating from the proposed age thickness relationships are the kola peninsula archean and the oslo rift permian the average crustal thickness in the former area is around 44 km while the latter area is associated with a moho elevation of 3 5 km maximum crustal thicknesses in excess of 50 km have been found in southwestern and central finland and correlate with a crust of proterozoic age the caledonides of western norway do not exhibit as elsewhere a crustal root sub moho p n and s n seismic velocities are relatively small in that area and bouguer gravity values are strongly negative intracrustal p velocity variations do not seem to reflect geological age or specific tectonic features although the seismicity is moderate in fennoscandia most of the earthquake activity and in particular the largest earthquakes are confined to areas where the crustal thinning is most pronounced

seismic model of the lithosphere of the east european platform beneath the baltic sea black sea profile abstract this paper presents the results of seismic measurements along the baltic sea black sea profile the basic wave groups recorded up to distances of 900 km are characterized the main elements of a lithospheric model of the southwestern part of the precambrian east european platform are given the thickness of the earth s crust is about 45 km and the mean velocity of the crust is about 6 3 km s at a depth of 65 km the velocity increases from 8 2 to 8 5 km s in the depth interval 110 to 135 km there is a series of layers with low and high velocities the lower boundary of the lithosphere is probably defined by the boundary at a depth of 110 km

multisensor streamer recording and its implications for time lapse seismic and repeatability abstract effective time lapse or 4d processing seeks to extract the 4d signature with minimal background noise to help understand reservoir behavior in the production phase and to optimize producer and injector well placement nonrepeatability of source and sensor positions in the presence of overburden heterogeneity limits our ability to repeat seismic data and to deliver 4d signals with low background noise levels to compensate for imperfect receiver repositioning wavefield regularization techniques can enable wavefield matching on a grid common to both data vintages often there is a trade off between reducing the receiver positioning mismatch and crossline interpolation error from wavefield spatial aliasing through the use of towed multisensor marine seismic streamers that record collocated pressure p and acceleration measurements y and z and the application of a matching pursuit interpolation technique a 3d dealiased reconstructed and deghosted pressure wavefield can be obtained on a dens

seismic structure of the sub crustal continental lithosphere abstract seismic models of the continental lower lithosphere obtained from interpretation of body p waves in various regions of the earth are discussed the models differ in the character of velocity distribution the number of layers and the presence of the lower velocity layers this is the consequence of inhomogeneity of the lower lithosphere but it also follows from the differing accuracy and quality of seismic data the differences in models resulting from the use of seismological methods based on earthquake observations and experiments on long range profiles are pointed out the results of surveys into the lower lithosphere of the east european platform are analysed in greater detail

overburden complexity and repeatability of seismic data impacts of positioning errors at the oseberg field north sea repeatability of seismic data plays a crucial role in time lapse seismic analysis there are several factors that can decrease the repeatability such as positioning errors varying tide source variations velocity changes in the water layer marine data and undesired effects of various processing steps in this work the complexity of overburden structure as an inherent parameter that can affect the repeatability is studied a multi azimuth three dimensional vertical seismic profiling data set with 10 000 shots is used to study the relationship between overburden structure and repeatability of seismic data in most repeatability studies two data sets are compared but here a single data set has been used because a significant proportion of the 10 000 shots are so close to each other that a repeatability versus positioning error is possible we find that the repeatability decreases by a factor of approximately 2 under an overburden lens furthermore we find that the x and y components have approximately the same sensitivity to positioning errors as the z component for the same events in this three dimensional vertical seismic profiling experiment this indicates that in an area with complex overburden positioning errors between monitor and base seismic surveys are significantly more critical than outside such an area this study is based on a three dimensional three component vertical seismic profiling data set from a north sea reservoir and care should be taken when extrapolating these observations into a general four dimensional framework

the geodynamic evolution of the precaspian basin kazakhstan along a north south section abstract several hypotheses exist for the origin and evolution of the precaspian basin there are more than 20 km of sediments deposited yet there is little consensus on the causes of the subsidence except for the presence of a thick salt layer lower permian the main problem is the chronostratigraphic interpretation of the sediments in the centre of the basin where the calibration of seismic data with well data from the basin margins is problematic at deep levels the age of the deepest sediments could be either riphean or devonian a generalised cross section of the precaspian basin roughly perpendicular to the central elongated e w depocentre is used to represent the basin s evolution several evolutionary steps from the end of the riphean until the present are demonstrated tectonic subsidence analysis indicates that there are six main phases of evolution 1 subsidence during an active rifting phase in riphean times 2 rifting during the vendian ordovician poorly dated 3 significant subsidence during the late devonian in an extensional context possibly due to back arc rifting 4 acceleration of subsidence during the late carboniferous permian synchronous with or just following the closure of the uralian ocean a major subsidence phase in the dniepr donets basin and possible subduction to the south of the basin 5 renewed rifting during the triassic coincident with a general phase of extension in eurasia and the opening of the neo tethys and 6 neotectonic subsidence resulting from crustal down bending in a generally compressional setting the nature of the crust underlying the basin is not well known it could be riphean early palaeozoic or devonian oceanic crust or continental crust attenuated during the several episodes of supposed rifting between the riphean and the triassic estimations of crustal thickness in the basin vary and they depend on the interpretation of a high velocity layer situated at the base of the crust the presence and general distribution of this layer is confirmed by gravity data it may be considered as the uppermost mantle as oceanic crust metamorphosed into eclogite at depth during collision and then exhumed and emplaced at the base of the crust or as lower crust transformed in situ into eclogites the crustal thinning factor leading to the observed present crustal thickness assuming an initial thickness of 40 km is 3 3 in the two first cases and 2 in the latter if the crust is considered to be continental the geophysical and subsidence data are discussed in terms of basin forming mechanisms such as 1 intracontinental rifting of early palaeozoic devonian or permo triassic ages 2 oceanisation of continental crust during riphean or devonian time 3 eclogititisation at the base of the crust in the upper mantle or by metamorphism of subducted oceanic crust and 4 down bending due to compressional forces or mantle flow induced by subduction collision processes in carboniferous and recent times

moho reflectivity and seismic signal penetration abstract analysis of amplitude decay and frequency change is applied to determine limits of seismic signal penetration on deep seismic reflection data collected by lithoprobe and the consortium for continental reflection profiling cocorp changes in spectral frequency content are efficiently monitored with averaged instantaneous frequency and bandwidth results from montana show pronounced increases in average frequency and slight drops in amplitude associated with a die out of reflections at the moho results from quebec show amplitude and frequency change occurring through the moho on lines with and without moho reflections these contrasting observations confirm both adequate signal penetration and that the differences in moho reflectivity are representative of geologic differences

the crustal structure of the southern caspian region the south caspian basin appears to behave as a relatively rigid aseismic block within the otherwise deforming alpine himalayan orogenic belt this anomalous character suggests that there is a fundamental compositional difference between the crust of the south caspian basin and that of the surrounding region five new estimates of crustal velocity structure beneath the southern caspian region are determined by the teleseismic receiver function method these models show that the crust in turkmenia along the trend of the apshceron balkhan sill kopet dag mountains is 50 km thick in the southwestern part of the caspian basin the crust is 33 km thick and consists of a 13 km thick sedimentary section lying on a high velocity vp 7 1 km s 1 lower crustal section in the southeastern part of the basin the crust is 30 km thick and consists of a 10 km thick sedimentary section overlying a 20 km thick low velocity vp 5 8 km s 1 crystalline crust the receiver function models are combined with velocity models from previous russian deep seismic sounding studies into a 1800 km long ese wnw trending crustal cross section across the kura depression the south caspian basin and the kopet dag mountains the most significant features of this crustal model are the 20 km variation in thickness of cenozoic sedimentary basin deposits the absence of a granitic vp 5 8 6 5 km s 1 crustal layer in the central part of the south caspian basin and 20 km of crustal thinning beneath the central part of the basin the moho beneath the south caspian basin has a broad arch like structure whose western boundary is a relatively narrow zone across which the crust thins rapidly 20 km thinning over a 100 km zone and whose eastern boundary has a more gradual change in crustal thickness 20 km thinning over a 400 km zone the velocity depth profiles derived from the receiver functions are compared to laboratory velocity estimates made at pressures and temperatures appropriate for the lower crust in turkmenia but the seismic p wave data alone do not permit differentiation between the various possible rock types the crustal model developed for the south caspian basin is consistent with the hypothesis that the crystalline crust of the basin is a section of oceanic crust that is being overthrust by the continental crust around much of its margins however we cannot rule out the possibility that the crystalline crust beneath the basin is a section of lower continental crust whose upper crustal section has been removed by erosion or faulting

upper mantle heterogeneity in the northern part of eurasia abstract a two dimensional velocity model of the upper mantle has been compiled from a long range seismic profile crossing the west siberian young plate and the old siberian platform it revealed considerable horizontal and vertical heterogeneity of the mantle a sharp seismic boundary at a depth of 400 km outlines the high velocity gradient transition zone its base lying at a depth of 650 km several layers with different velocities velocity gradients and wave attenuation are distinguished in the upper mantle they likewise differ in their inner structure for instance the uppermost 50 70 km of the mantle are divided into blocks with velocities from 7 9 8 1 to 8 4 8 6 km s 1 comparison of the travel time curves for the siberian long range profile with those compiled from seismological data for europe distinguished large scale upper mantle inhomogeneities of the eurasian continent and allowed for the correlation of tectonic features and geophysical fields the velocity heterogeneity of the uppermost 50 100 km of the mantle correlates with the platform age and heat flow i e the young plates of western europe and western siberia have slightly lower velocities and higher heat flows than the ancient east european and siberian platforms at greater depths 150 250 km the upper mantle velocities increase from the ocean to the inner parts of the continent the structure of the transition zone differs significantly beneath western europe and the other parts of eurasia the sharp boundary at a depth of 400 km traced throughout the whole continent as the boundary reflecting intensive waves transforms beneath western europe into a gradient zone this transition zone feature correlates with positions of the north atlantic west europe geoid and heat flow anomalies

studies of mantle structure of u s s r territory on long range seismic profiles long range seismic sounding carried out during the last few years on the territory of the u s s r has shown a basic inhomogeneity of the uppermost mantle as well as evidence of regularities in the distribution of its seismic parameters the following data were used times and apparent velocities of p and s waves for investigation of mantle velocities converted waves for seismic discontinuity model studies and wave attenuation for q factor estimation strong regularities were distinguished in the distribution of average seismic velocities for the uppermost mantle in their dependence on the age and type of geostructure and on their position relative to the central part of the continent old platforms and the inner part of the continent are marked by velocities under the mohorovicic discontinuity of more than 8 2 8 3 km s 1 young platforms and outer parts of the continent by 8 0 8 2 km s 1 and orogenic and rift zones by 7 8 8 0 km s 1 the difference becomes more pronounced at a depth of about 100 200 km for the old platform mantle velocities of 8 5 8 6 km s 1 are typical beneath the orogenic and rift areas inversion zones with velocities less than 7 8 km s 1 are observed the converted waves show fine inhomogeneities of the crust and uppermost mantle the presence of many discontinuities with positive and negative changes of velocity and anisotropy of seismic waves in some of the layers wave attenuation allowed the determination of the q factor in the mantle it varied from one region to another but a close relation between q and p wave velocity is the main cause of its variation

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

on the use of multicomponent streamer recordings for reconstruction of pressure wavefields in the crossline direction three component measurements of particle motion would bring significant benefits to towed marine seismic data if processed in conjunction with the pressure data we show that particle velocity measurements can increase the effective nyquist wavenumber by a factor of two or three depending on how they are used a true multicomponent streamer would enable accurate data reconstruction in the crossline direction with cable separations for which pressure only data would be irrecoverably aliased we also show that conventional workflows aimed at reducing these aliasing effects such as moveout correction applied before interpolation are compatible with multicomponent measurements some benefits of velocity measurements for deghosting data are well known we outline how the new measurements might be used to address some long standing deghosting challenges of particular interest specifically we propose methods for recovering de ghosted data between streamers and for 3d deghosting of seismic data at the stream

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

inhomogeneities of the eurasian mantle structure from the traveltimes of the nuclear explosions recorded by the finnish seismic network during 1961 1985 summary during the period 1961 1985 hundreds of nuclear explosions from the area of the soviet union and china were well recorded at finnish seismological stations the seismic waves recorded on the baltic fennoscandian shield penetrated through the mantle of the siberian platform the ural mountains and the east european platform from the known crustal models the functions describing the increase of the average velocities of sedimentary cover and crystalline complex of the crust with thickness were found the corrections for sedimentary cover and crustal thickness were included the large amount of data permitted the calculation of traveltimes of p waves for three sectors up to distances of about 5000 km in all mantle models the boundaries 400 and 700 km were found comparison of the results shows a difference in the traveltimes of the order of 5 s at a distance of about 4000 km which reflects the mantle structure differentiation for depths greater than 700 km lowest velocities for latitudinal direction and highest velocities for longitudinal direction the average s wave velocity model of the mantle was obtained using the traveltimes of s wave first arrivals high values of the vp vs ratio were found in the depth interval 200 400 km while in other depth intervals they were close to 1 73 our 1 d models are compared with and discussed in connection with other models of the east european and siberian platforms as well as with global tomographic solutions

integrated seismic model of the crust and upper mantle of the trans european suture zone between the precambrian craton and phanerozoic terranes in central europe abstract the structure and evolution of the trans european suture zone tesz contact between precambrian europe to the northeast and phanerozoic terranes to the southwest is one of the main tectonic questions in europe the knowledge of the crustal structure lithosphere asthenosphere boundary and mantle transition zone between two seismic discontinuities at depths 410 and 660 km is one of the most important issues to understand the earth s dynamics to create a mantle model of the tesz and surroundings we used different seismic data collected along the 950 km long polonaise 97 profile p4 previous results of 2 d ray tracing and p wave travel time modelling and new results of p wave travel time residuals methods and receiver function sections provide facts about the seismic structure from the surface down to 900 km depth in the tesz a large basin about 125 km wide is filled with sedimentary strata vp 7 0 km s 1 along most of the p4 profile however lower values to the southwest may indicate the termination of baltica high velocity 8 35 km s 1 uppermost mantle lies beneath the avalonia variscan terranes and may be due to rifting and or subduction the seismic lithosphere thickness for the eec is about 200 km while it is only 90 km in the palaeozoic platform pp the mantle transition zone is shallower and about 30 km thicker under the eec which could be due to thermal conditions lower temperature and or the presence of water and feo the result of this paper is a new compiled and integrated seismic velocity model available in digital form down to 900 km depth http www igf fuw edu pl p4 mantle which can be used as a preliminary model of the crust and upper mantle in the tesz area in central europe

crustal structure along the northern fennolora profile abstract many data notably concerning the great change in earth s bulk heat flow which has occurred since the archaean era suggest that late archaean and early proterozoic tectonic processes were most probably different from phanerozoic plate tectonics preserved structures in the earth s crust revealed by the seismic refraction wide angle reflection method can help in understanding the different crustal tectonic processes that have influenced the evolution of the area p wave analysis for the northern part of the fennolora deep seismic refraction line clearly shows the difference between the central swedish svecofennian crust and the archaean crust in the north along the archaean part of the fennolora line high apparent velocities have been recorded in the upper crust the central svecofennian crust on the other hand shows normal upper crustal velocities data from the archaean part of the fennolora profile give support to the concept of an ensialic development in this region during the late archaean and early proterozoic

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

crustal image of the ionian basin and its calabrian margins abstract previous seismic investigation of the crustal structure in the ionian basin has been limited to shallow penetration seismics of the 1970 s characterized by inadequate source power and low fold earlier obs and esp seismic refraction experiments have not been able to firmly resolve one of the principal scientific problems for this region which is whether the ionian basin is floored by oceanic crust or by highly attenuated continental crust a second elusive problem is the nature of the transition of the boundaries between the ionian basin and its margins in this paper we describe and interpret new deep seismic reflection and wide angle data collected in the western ionian sea and the calabria region of italy one of the principal features of our multichannel reflection data beneath the ionian basin is a band of layered high amplitude reflections near the base of the crust this band shows a quasi monochromatic ca 8 to 10 hz frequency and a traveltime thickness of 1 to 1 5 s these images contrast with the well known reflection patterns of mesozoic oceanic crust investigated in the atlantic ocean there is evidence that the low frequency band dips down towards the edge of the malta escarpment me where landward dipping reflectors separate continental and intermediate type crust in the central tract of the me the increased traveltimes of the lower crustal reflectors and moho from the basin towards the southern and eastern margins of southern calabria could be partially due to the velocity pull down effect of the sedimentary pile of the arc although a true dip of 15 to 18 over 60 km distance can be substantiated moreover the reflecting band maintains its reflectivity and thickness until its abrupt termination beneath the ionian continuation of the calabrian compressional crustal structures the coincident acquisition of wide angle seismic data and marine reflection seismic data provided a landward extension of the survey which will complement existing geologic information on the deep framework of the ionian basin and its calabrian margin

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

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