source characteristics of the sinaia romania sequence of may june 1993 a particular sequence of crustal earthquakes h 10 km ml 5 1 occurred in the southwestern extremity of the eastern carpathian arc bend sinaia region starting on may 4 1993 the main shock ml 5 1 occurred on may 23 after significant 20 day foreshock activity the first locations delineate an epicentral area of approximately 225 km2 elongated in a nw se direction which agrees with the fault plane solution for the main shock the digital recordings of the romanian telemetered network are analyzed in order to estimate source parameters and to investigate scaling relations an empirical deconvolution technique and the spectral ratio method are used for this purpose the main results such as 1 the departure from a m13o scaling of the source radius as a function of the seismic moment 2 the scaling of the peak velocity parameter as a function of local magnitude and 3 the scaling of the dynamic stress drop with earthquake size are interpreted in terms of an inhomogeneous source model

kinematic evolution of the romanian carpathians abstract the regional pattern of contraction and extension directions and the evolution of the strain field from paleogene to neogene times enabled a reconstruction of the migration path of the carpathian collision front the carpathian nappes were thrust around the moesian plate during paleogene and early neogene times and protruded into a small oceanic embayment between the moesian and european plates the arc structure of the carpathian fold thrust belt was formed in late neogene times as a result of the eastward escaping tisza dacia block due to n directed convergence of the adriatic plate and the retreating subduction of an oceanic slab brittle deformation structures in the romanian carpathians suggest three tectonic events related to major plate motions 1 paleogene to middle miocene ne to ene contraction caused right lateral curved strike slip faults 2 middle miocene to pliocene fan shaped orientations of contraction directions were caused by right lateral oblique convergence in the southern carpathians frontal convergence in the southern eastern carpathians and left lateral convergence in the northern eastern carpathians 3 pleistocene to holocene general e w extension and n s contraction in the carpathian arc and local ese wnw contraction in the vrancea area is related to the late roll back stage and break off of the subducted slab in the bend area

the east carpathians indications of phase transitions lithospheric failure and decoupled evolution of thrust belt and its foreland abstract an analysis is presented of the tectonic development of the east carpathians since the late oligocene the geological and geomorphological data show that five epochs of convergence and nappe emplacement took place with the last one occurring 11 12 m y b p after these compressional events the nappe surface remained near sea level the crustal uplift which formed the present mountains began 3 m y b p and after 99 of the shortening of the carpathians had been completed the pre carpathian foreland basin up to 3 5 km deep formed on the margin of the east european platform in the middle miocene analysis of the evolution of the basin shows that it deepened away from the nappe stack and most of the subsidence occurred when there was no convergence this precludes lithospheric flexure due to convergence as a mechanism for basin formation at 11 12 m y b p the inner part of the basin 50 km wide was overridden by the carpathian nappe up to 12 14 km thick at that time a slight crustal uplift took place rather than subsidence in the shallow remnant outer basin part the present foredeep which emerged above sea level an additional 7 8 km of subsidence then occurred in the foredeep of the southeastern carpathians in the late miocene early pleistocene when very little convergence took place the evolution of the carpathian foredeep shows that lithospheric flexure of 2 5 km occurred in regions 20 40 km wide similar amounts of flexure and large basement faults exist under the nappe this style of deformation indicates flexural rigidity of the lithosphere that is several orders of magnitude smaller than in stable cratonic regions under a low flexural rigidity the crust should be close to local isostasy then the isostatic response to superposition of a 10 13 km thick nappe on the platform margin which was near sea level would form high mountains the crustal surface however remained at a low altitude we interpret this to be the result of contraction of gabbro in the lower crust with the formation of dense garnet granulites during nappe emplacement a layer of these dense rocks 20 km thick with p wave velocities 7 5 7 6 km s exists in the lower crust of the east carpathians according to the geophysical data there is no cool high velocity slab now subducting towards the intra carpathian area an increase in the mean height of the carpathians by only 1 km since the termination of convergence precludes a recent slab detachment rapid metamorphism of mafic rocks in the lower crust requires the infiltration of volatiles from the asthenosphere infiltration of volatiles into mantle lithosphere and the upper crust could strongly reduce their viscosity these phenomena might be the cause of an abrupt loss of lithospheric rigidity on the margin of the east european platform in the neogene lithospheric failure allowed the incorporation of this region into the carpathian fold belt after a long period of cratonic development

tertiary tectonic evolution of the external east carpathians romania abstract paleostress calculation and analysis of mesoscopic structures are integrated with depth interpreted geological profiles based on seismic studies and well correlation to derive a tertiary tectonic model for the east carpathians following early miocene and older orogenic phases the first tectonic event that affected the studied area is characterised by a wsw ene oriented shortening of middle miocene late burdigalian in age resulting deformations induced ene ward thrusting of tarcau and marginal units as well as the internal part of the subcarpathian nappe a second shortening event with an e w to wsw ene contraction direction took place in the late miocene sarmatian characterised by further foreland thrusting of the subcarpathian nappe and out of sequence deformation in the tarcau and marginal folds nappes along strike differences in deformation mechanisms are controlled by the friction coefficients along the main detachment layers by the lateral variations in the wedge thickness and by the involvement in the northern part of the thrusting system of the thick competent east european platform tear faulting occurred in both tectonic events the main resulting structure being the triangle zone developed south of the trotus valley the latest miocene latest sarmatian early pliocene is characterised by a strike slip stress field with nne ssw compression and wnw ese tension axis left lateral faults being dominant the last deformation which affected the studied area is characterised by nnw sse shortening during the pliocene major deformations taking place mainly in the sw most bending zone

depositional record of an avulsive fluvial system controlled by peat compaction neogene most basin czech republic this paper illustrates the response of a fluvial depositional system to the interplay between peat compaction and clastic sediment supply at a range of spatial and temporal scales as documented by extensive exposures in an open cast mine in the most basin part of the oligo miocene oh e rift eger graben basin system in the czech republic the most basin is characterized by the occurrence of a number of phenomena resulting from syn and post depositional interactions between clastic sedimentary systems and the underlying accumulation of organic material that was the precursor of the main lignite seam of up to 45 m thickness the studied strata are interpreted as deposits of an avulsive mixed load fluvial system the large scale depositional architecture documents an existence of at least five stratal packages up to 1500 m wide and up to several tens of metres thick representing a record of long term evolution of a clastic floodplain bordered by accumulating peat within each of the packages several small scale channel belts were documented individual packages are separated by carbonaceous mudstones indicating a period of reduced clastic input and interpreted as due to avulsion of the fluvial channels out of the floodplain limit two main mutually linked processes controlled the evolution of the studied fluvial system i syndepositional compaction of the underlying peat and ii avulsions of the channels away from the original floodplain resulting in formation of a new floodplain the processes which caused the channels of the hrabak fluvial system to reach the avulsion threshold were i decrease of rate of creation of accommodation leading to increased sinuosity and thus to a decreased channel slope and ii cross floodplain tilting of the channel belt caused by differential compaction of underlying organic rich substratum

the neogene evolution of the outer carpathian flysch units poland ukraine and romania kinematics of a foreland fold and thrust belt system abstract various techniques of geometric and kinematic analyses including cross section balancing and forward modeling have been applied successfully to the outer carpathian flysch units along regional geologic profiles crossing the belt from its undeformed foreland to the pieniny klippen belt western carpathians poland or to the central east carpathian allochthon eastern carpathians ukraine and romania the amounts of neogene shortening as well as the mode and the location of basement consumption are discussed on the basis of balanced cross sections compiled along the three most representative regional traverses in addition the complete kinematic evolution of complex carpathian structures such as the fore dukla triangle zone southeastern poland the borislav pokut duplexes ukraine and the marginal folds romania are described in more detail by using a forward modeling approach major results concern the tectonic heritage of laramian inverted structures mesozoic normal faults reactivated as reverse faults during the late cretaceous paleocene compression or transpression in the development of the neogene outer carpathian edifice pre eocene deformation and erosion effectively induce discontinuities in the mid cretaceous blackshale detachment horizon and help to localize the neogene deformations in complex triangle zones the thrust sequence itself evolves alternatively in a piggyback or in an out of sequence mode clearly the critical taper of the outer carpathians is preserved by a constant balance between erosion and thrust reactivations in the inner part of the wedge and sedimentation and tectonic accretion at its front

crustal constraints on the origin of mantle seismicity in the vrancea zone romania the case for active continental lithospheric delamination abstract the vrancea zone of romania constitutes one of the most active seismic zones in europe where intermediate depth 70 200 km earthquakes of magnitude in excess of m w 7 0 occur with relative frequency in a geographically restricted area within the 110 bend region of the southeastern carpathian orogen geologically the vrancea zone is characterized by a a laterally restricted steeply nw dipping seismogenic volume 30 70 200 km situated beneath b thickened continental crust within the highly arcuate bend region of the carpathian orocline and c miscorrelation of hypocenters with the position of known or inferred suture zones in the carpathian orogenic system geologic data from petroleum exploration in the eastern carpathians published palinspastic reconstructions and reprocessing of industry seismic data from the carpathian foreland indicate that 1 crust of continental affinity extends significantly westward beneath the external thrust nappes sub carpathian marginal folds and tarcau of the eastern carpathians 2 cretaceous to miocene strata of continental affinity can be reconstructed westward to a position now occupied by the transylvanian basin and 3 geologic structure in the carpathian foreland including the moho is sub horizontal directly to the east and above the vrancea seismogenic zone taken together these geologic relationships imply that the vrancea zone occupies a region overlain by continental crust and upper mantle and does not appear to originate from a subducted oceanic slab along the length of the carpathian orogen accordingly the vrancea zone appears to potentially be an important place to establish evidence for active lithospheric delamination

the tectonic expression slab pull at continental convergent boundaries examination of five thrust belt systems developed at continental subduction boundaries suggests that they comprise two distinct groups that display pronounced and systematic differences in structural style topographic elevation denudation metamorphism postcollisional convergence and foredeep basin geometry and facies the distinctive geological features developed within each thrust belt group appear to be causally linked to the relative rates of subduction and convergence via the magnitude of horizontal compressional stress transmitted across the subduction boundary at subduction boundaries where the rate of overall plate convergence is less than the rate of subduction termed here retreating subduction boundaries the transmission of horizontal compressive stress across the plate boundary is small and regional deformation of the overriding plate is by horizontal extension the tectonic expression of these retreating subduction boundaries includes topographically low mountains little erosion or denudation low grade to no metamorphism little to no involvement of crystalline basement in shortening little to no postcollisional convergence anomalously deep foredeep basins and a protracted history of flysch deposition within the adjacent foredeep basin analysis of deflection and gravity data across three retreating subduction boundaries apennine carpathian and hellenic systems shows that subduction is driven by gravitational forces acting on dense subducted slabs at depths between about 40 and 80 km carpathians 50 and 150 km apennines and 50 and 250 km hellenides the total mass anomalies represented by the slabs are approximately 3 1012 6 1012 and 12 1012 n m respectively the slabs are partially supported by flexural stresses transmitted through the subducted lithosphere to the foreland and partially supported by dynamic viscous stresses in the asthenosphere at subduction boundaries where the rate of overall plate convergence is greater than the rate of subduction termed here advancing subduction boundaries the transmission of horizontal compressive stress across the plate boundary is large and regional deformation of the overriding plate is by horizontal shortening the tectonic expression of these advancing subduction boundaries includes topographically high mountains antithetic thrust belts large amounts of erosion and denudation exposure of high grade metamorphic rocks at the surface extensive deformation of crystalline basement to midcrustal depths protracted postcollisional convergence tens of millions of years and a protracted history of molasse deposition within the adjacent foredeep basins analysis of gravity and deflection data across two advancing subduction boundaries developed within the continental lithosphere western to eastern and southern alps and himalayas shows that the thrust sheets have been translated for great distances over the foreland lithosphere relative to the point at which the subduction forces are applied thus obscuring any flexural and gravity signals from the subducted slab however it appears that far field stresses presumably related to global plate motions drive most of the convergent motion across these subduction boundaries the concept that orogenic belts formed above retreating subduction boundaries have recognizable tectonic signatures that differ from those of orogenic belts formed above advancing subduction boundaries suggests that it may be possible to interpret the plate boundary settings in which ancient orogenic belts evolved appendix b is available with entire article on microfiche order from the american geophysical union 2000 floridaavenue n w washington d c 20009 document t92 004 2 50 payment must accompany order

a note on the depth recurrence and strain release of large vrancea earthquakes the large 1940 vrancea event with body wave magnitude mb 7 3 was investigated in terms of the depth of rupture initiation and extent it was found that the rupture started at 150 km depth and propagated downwards the ruptured zones of the 1977 1986 and 1990 vrancea events were estimated from the distribution of aftershocks located with the joint hypocentre determination method their depth ranges are 90 110 km 130 150 km and 70 90 km respectively because the body wave magnitudes mb were saturated for the last three events and the surface wave magnitudes ms were underestimated not being corrected for depth we chose the moment magnitudes to quantify the four events 7 7 1940 7 4 1977 7 1 1986 and 6 9 1990 respectively the depth interval 110 130 km is found to be unbroken since at least 1838 or 1802 and therefore is expected to accommodate the next large moment release mw 7 0 to 7 4 the strain in the vertical and in the se nw directions is about 0 0003 giving a moderate strain rate of about 10 13 s 1 a correlation between the depth interval of the large events and the year of occurrence in a century is suggested offering a physical basis to the observed quasi cyclicity

lateral variations in mechanical properties of the romanian external carpathians inferences of flexure and gravity modelling we present the results of two dimensional flexure and gravity modelling of the subsidence of the romanian carpathian foreland based on twenty profiles through the southern and eastern carpathians the narrow spacing of the grid of profiles allows us to investigate the lateral tectonic variations transverse to the belt but also along strike the topographic elevation of the romanian carpathian mountain belt is modest and the minimum in the bouguer gravity anomaly characteristic for flexural control of subsidence is located relatively far towards the foreland in respect to the mountain belt as the contribution of topographic loading to the evolution of the romanian carpathian foreland system is small a subduction underplating dominated tectonic regime controlled the nappes emplacement and basin shortening in the external flysch and molasse basins during the late tertiary the modelling results support the existence of important variations in effective elastic thicknesses te and plate boundary forces high flexural bending stresses in the western part of the southern carpathians can explain low te values whereas the increase of te to the east can be explained by changes in rheological properties of the moesian platform field observations indicate that variations in deflection along strike are probably also related to basement unregularities stress field rotations and strike slip movement along lateral ramps during the tertiary in the eastern carpathians the model results indicate a n s trend of lateral back stepping of the subduction system a distinct back step in the vicinity of the seismically active vrancea area supports the involvement of the e w crustal scale trotus fault which forms the transition from the east european platform to the scythian and moesian platforms development of a possible n s migration of plate boundary activity or slab detachment and successive intersection with the trotus fault can explain the large pliocene subsidence in the focsani depression and relative uplife of the east european platform north of the mentioned fault

revised crustal architecture of the southeastern carpathian foreland from active and passive seismic data 1 integration of active and passive source seismic data is employed in order to study the nature of the relationships between crustal seismicity and geologic structures in the southeastern se carpathian foreland of romania and the possible connection with the vrancea seismogenic zone vsz of intermediate depth seismicity one of the most active earthquake prone areas in europe crustal epicenters and focal mechanisms are correlated with four deep industry seismic profiles the reprocessed danube and carpathian integrated action on process in the lithosphere and neotectonics dacia plan profile and the deep reflection acquisition constraining unusual lithospheric activity ii and iii dracula profiles in order to understand the link between neotectonic foreland deformation and vrancea mantle seismicity projection of crustal foreland hypocenters onto deep seismic profiles identifies several active crustal faults in the se carpathian foreland and suggests a mechanical coupling between the mantle located vsz and the overlying foreland crust the coupled associated deformation appears to take place on the trotus fault the sinaia fault and the newly detected ialomita fault seismic reflection imaging reveals the absence of west dipping reflectors in the crystalline crust and a slightly east dipping to horizontal moho in the proximity of the vrancea area these findings argue against previously purported mechanisms to generate mantle seismicity in the vsz including oceanic lithosphere subduction in place and oceanic slab break off furthermore suggesting that the vrancea seismogenic body is undetached from the overlying crust in the foreland

vrancea99 the crustal structure beneath the southeastern carpathians and the moesian platform from a seismic refraction profile in romania the vrancea99 seismic refraction experiment is part of an international and multidisciplinary project to study the intermediate depth earthquakes of the eastern carpathians in romania as part of the seismic experiment a 300 km long refraction profile was recorded between the cities of bacau and bucharest traversing the vrancea epicentral region in nne ssw direction the results deduced using forward and inverse ray trace modelling indicate a multi layered crust the sedimentary succession comprises two to four seismic layers of variable thickness and with velocities ranging from 2 0 to 5 8 km s the seismic basement coincides with a velocity step up to 5 9 km s velocities in the upper crystalline crust are 5 9 6 2 km s an intra crustal discontinuity at 18 31 km divides the crust into an upper and a lower layer velocities within the lower crust are 6 7 7 0 km s strong wide angle pmp reflections indicate the existence of a first order moho at a depth of 30 km near the southern end of the line and 41 km near the centre constraints on upper mantle seismic velocities 7 9 km s are provided by pn arrival times from two shot points only within the upper mantle a low velocity zone is interpreted travel times of a plp reflection define the bottom of this low velocity layer at a depth of 55 km the velocity beneath this interface must be at least 8 5 km s geologic interpretation of the seismic data suggests that the neogene tectonic convergence of the eastern carpathians resulted in thin skinned shortening of the sedimentary cover and in thick skinned shortening in the crystalline crust on the autochthonous cover of the moesian platform several blocks can be recognised which are characterised by different lithological compositions this could indicate a pre structuring of the platform at mesozoic and or palaeozoic times with a probable active involvement of the intramoesian and the capidava ovidiu faults especially the intramoesian fault is clearly recognisable on the refraction line no clear indications of the important trotus fault in the north of the profile could be found in the central part of the seismic line a thinned lower crust and the low velocity zone in the uppermost mantle point to the possibility of crustal delamination and partial melting in the upper mantle

full waveform seismic tomography of the vrancea romania subduction region abstract the vrancea region is one of the few locations of deep seismicity in europe seismic tomography has been able to map lithospheric downwelling but has not been able yet to clearly discriminate between competing geodynamic interpretations of the geological and geophysical evidence available we study the seismic structure of the vrancea subduction zone using adjoint based full waveform tomography to map the 3d vp and vs structure in detail we use the database that was built during the calixto carpathian arc lithosphere x tomography temporary experiment restricted to the broadband sensors and local intermediate depth events we fit waveforms with a cross correlation misfit criterion in separate time windows around the expected p and s arrivals and perform 17 iterations of vp and vs model updates altogether requiring about 16 million cpu hours before reaching stable convergence among other features our resulting model shows a nearly vertical high velocity body that overlaps with the distribution of seismicity in its northeastern part in its southwestern part a slab appears to dip less steeply to the nw and is suggestive of ongoing or recently concluded subduction geodynamic processes joint inversion for vp and vs allow us to address the vp vs ratio distribution that marks high vp vs in the crust beneath the focsani sedimentary basin possibly due to high fluid pressure and a low vp vs edge along the lower plane of the subducting lithosphere that in other similar environment has been attributed to dehydration of serpentine in the slab in spite of the restricted amount of data available and limitations on the usable frequency pass band full waveform inversion reveals its potential to improve the general quality of imaging with respect to other tomographic techniques although at a sensible cost in terms of computing resources our study also shows that re analysis of legacy data sets with up to date techniques may bring new useful information

subsidence analysis and tectonic evolution of the external carpathian moesian platform region during neogene times abstract the miocene pliocene subsidence of the tectonic platforms in the romanian carpathians foreland is analysed using standard 1d backstripping techniques for individual wells combined in two regional sections and six contour maps the subsidence patterns were integrated together with previous paleostress and kinematic studies in order to derive the tertiary kinematics of the buried faults in the carpathians lower plate the study revealed accelerated subsidence during the early miocene in the western part of the moesian platform getic depression in direct relationship with the opening of a wsw ene trending extensional basin the largest subsidence recorded in the front of the carpathians took place during the late miocene due to final e ward emplacement of the thrust sheets the late miocene subsidence showed anomalous high values between the intramoesian and trotus faults as a result of the orogenic collision with the east european platform northward and acceleration of the subduction process in the se carpathians corner further pliocene subsidence continued only in the latter region the depocenter being shifted southward near the junction with the south carpathians foreland

architecture of the focsani depression a 13 km deep basin in the carpathians bend zone romania 1 in front of the se carpathians bend a very deep basin focsani depression developed in miocene to recent times an important part of its subsidence occurred after the main stages of thrusting in the carpathians apparently the basin lies in the wrong place and evolved in the wrong time in this study we constrain its architecture and evolution by analyzing a large database consisting of more than 1000 km two dimensional seismic lines and more than 60 wells around 13 km thick badenian to quaternary 16 5 myr sediments were deposited in the central part of the focsani depression during the badenian 16 5 13 myr the foreland south of trotus fault underwent ne sw directed extension and nw trending basins opened in the eastern moesian platform a nw se oriented area of subsidence stretched from the transylvania basin through the focsani depression to the se of the moesian platform while thrusting was going on in the east european scythian platform east carpathians and getic depression starting with the sarmatian 13 10 myr the focsani depression depocenter moved out of the carpathian belt coeval with the exhumation of the south and the east carpathians north of the trotus fault the basin became wider and was tilted toward the belt tilting was accompanied by dextral shearing mainly along the intramoesian and peceneaga camena faults after sarmatian times subsidence occurred practically only sse of trotus fault during meotian pontian 10 5 myr subsidence slowed down stronger pliocene quaternary subsidence is coeval with normal faulting and shearing in moesian platform the western margin of the focsani depression was then tilted eastward coeval with the exhumation of the bend zone and opening of the intramontane basins in the inner part of the belt

slab in the wrong place lower lithospheric mantle delamination in the last stage of the eastern carpathian subduction retreat a model with a new type of delamination of the lower lithospheric mantle is proposed to explain the pliocene to recent tectonic evolution of the eastern carpathians we suggest that after the continental collision in middle miocene time break off of the west dipping subducting slab occurred at a depth of 70 km slab break off propagated horizontally toward the east inducing lithospheric delamination and movement of the vrancea slab into its present position delamination was followed by rapid asthenospheric rise resulting in magma generation and the explosive alkaline basaltic magmatism of the persani mountains contamination of the former subduction related magmatic reservoirs with the alkalic basaltic material and differentiation processes produced the harghita calc alkaline and shoshonitic rocks the asthenospheric rise induced crustal uplift which is the triggering mechanism for extension and formation of the brasov gheorghieni hinterland basins the extension was accommodated by shortening and folding in the foreland the vertical vrancea slab appears in our model as a segment of delaminated lower lithospheric mantle that is seismically active due to the ongoing pull of the eclogitized oceanic crust the model explains the displaced and shallow position of the slab relative to the eastern carpathian suture zone

near vertical seismic reflection image using a novel acquisition technique across the vrancea zone and foscani basin south eastern carpathians romania the dacia plan danube and carpathian integrated action on process in the lithosphere and neotectonics deep seismic sounding survey was performed in august september 2001 in south eastern romania at the same time as the regional deep refraction seismic survey vrancea 2001 the main goal of the experiment was to obtain new information on the deep structure of the external carpathians nappes and the architecture of tertiary quaternary basins developed within and adjacent to the seismically active vrancea zone including the focsani basin the seismic reflection line had a wnw ese orientation running from internal east carpathians units across the mountainous south eastern carpathians and the foreland focsani basin towards the danube delta there were 131 shot points along the profile with about 1 km spacing and data were recorded with stand alone reftek 125s also known as btexansq supplied by the university texas at el paso and the passcal institute the entire line was recorded in three deployments using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments the resulting deep seismic reflection stacks processed to 20 s along the entire profile and to 10 s in the eastern focsani basin are presented here the regional architecture of the latter interpreted in the context of abundant independent constraint from exploration seismic and subsurface data is well imaged image quality within and beneath the thrust belt is of much poorer quality nevertheless there is good evidence to suggest that a thick 10 km sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the focsani basin in the depth range 10 25 km most of the crustal depth seismicity observed in the vrancea zone as opposed to the more intense upper mantle seismicity appears to be associated with this sedimentary basin the sedimentary successions within this basin and other horizons visible further to the west beneath the carpathian nappes suggest that the geometry of the neogene and recent uplift observed in the vrancea zone likely coupled with contemporaneous rapid subsidence in the foreland is detached from deeper levels of the crust at about 10 km depth the moho lies at a depth of about 40 km along the profile its poor expression in the reflection stack being strengthened by independent estimates from the refraction data given the apparent thickness of the meta sedimentary supracrustal units the crystalline crust beneath this area is quite thin b20 km supporting the hypothesis that

2 5d seismic velocity modelling in the south eastern romanian carpathians orogen and its foreland 2 5 d seismic velocity modelling in the south easter romainan carpathians orogen and its foreland

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

partial detachment of a lithospheric root under the southeast carpathians toward a better definition of the detachment concept the southeast corner of the carpathian mountains romania provides a unique opportunity to study the very final and shortlived stage of plate convergence when a piece of subducted lithosphere finally detaches from the overriding plate and begins to sink into the mantle research efforts commonly focus on trying to image the cold lithospheric slab tomographic techniques and on trying to understand the tearing process from the earthquakes it generates here this issue is tackled from a different perspective emphasizing that the southeast carpathians are extremely low considering crustal thickness the crust there is almost as thick as the crust of the alps 50 55 km but the elevation is less than onehalf of the elevation of the alps it is interesting that the apennines italy are just the opposite they are rebounding after slab breakoff to reach elevations higher than expected from their crustal thickness 30 35 km like the crust of most passive margin coasts it is thus proposed that although seismologic studies indicate that the cold mantle body under the southeast carpathians is already partly detached from the overriding lithosphere it is still viscously coupled to the lithosphere and pulls it downward by utilizing residual topography analysis observed topography minus the contribution of the crust to it the subcrustal load is quantified and interpreted in terms of mantle lithosphere thickness extending to a depth of 300 km a particularly interesting finding is that the seismically active region is shifted 50 km east of the place of maximum pull down indicating that lithospheric tearing is now occurring at one side of the detaching root and not above it this interpretation is consistent with the idea of lateral delamination of the lower lithosphere

observation of present day tectonic motions in the southeastern carpathians results of the ises crc 461 gps measurements results are presented from gps measurements performed in the southeastern carpathians between 1997 and 2004 data from 25 stations observed during 13 campaigns were analyzed by the department of earth observation and space systems deos of delft university of technology the repeatabilities of the solutions are on the order of 1 4 mm for the horizontal and 4 8 mm for the vertical component the resulting velocity estimates have an uncertainty of b1 mm yr and b3 mm yr respectively the region southeast of the carpathian bend zone shows a horizontal movement towards sse of 2 5 mm yr while the transylvanian basin shows very small motions with respect to eurasia the vertical velocity field indicates the existence of uplift and subsidence domains in the se carpathians in good agreement with pliocene quaternary orogen and basin studies another 29 gps stations installed in the last 3 yr will generate a denser velocity field in the coming years for this region d 2005 elsevier b v all rights reserved

source characteristics of the seismic sequences in the eastern carpathians foredeep region romania the source parameters and scaling properties for two seismic areas vr ncioaia and r mnicu s rat of the carpathians mountains foredeep adjacent to the vrancea seismic region are analyzed by standard time and frequency domain methods and empirical green s function deconvolution the study area is characterized by distinct shallow seismicity clusters with small and moderate size earthquakes m 5 the digital short period and broad band waveforms recorded by the romanian seismic network are considered the analysis of the retrieved source parameters possibly outlines a heterogeneous faulting process a significant difference in the stress drop value is emphasized between vr ncioaia and r mnicu s rat earthquakes which is assumed to be ascribed to differences in the local seismotectonics and reology our paper shows the efficiency of the empirical green s function deconvolution in eliminating the instrument path and site effects for the earthquake sequences in the r mnicu s rat region the apparent source time function is generally well constrained as demonstrated by our tests using in parallel both appropriate green s functions of different sizes and instruments with different frequency bandwidth

topo europe from iberia to the carpathians and analogues abstract earth sciences are rapidly changing from largely descriptive to process oriented disciplines that aim at quantitative models for the reconstruction and forecasting of the complex processes in the solid earth prediction is highly relevant for the basic needs of humanity supply of water and resources protection against natural hazards and control on the environmental degradation of the earth intensive utilization of the human habitat carries largely unknown risks of and makes us increasingly vulnerable there is an urgent need for scientifically advanced geo prediction systems that can accurately locate subsurface resources and forecast timing and magnitude of natural hazards the design of such systems is a major multidisciplinary scientific challenge the quantitative understanding of the earth has made significant progress in the last few decades important ingredients in this process have been the advances made in seismological methods to obtain information on the 3d structure of the mantle and the lithosphere in the quantitative understanding of the lithospheric processes as well as the recognition of the key role of quantitative sedimentary basin analysis in connecting temporal and spatial scales quantitative understanding of the mass transfer by erosion and deposition as well as their feed back with crustal and subcrustal dynamics presents a new frontier in modern earth sciences this research bridges investigations on high resolution near surface time scales and the large scale long term approaches characteristic for the lithosphere and basin wide studies the essential step towards a 4d approach in space and time is a direct response to the need for a full incorporation of geological and geophysical constraints in the modelling of solid earth processes topo europe is a multidisciplinary international research program that addresses the interaction of processes inherent to the deep earth lithosphere and mantle with surface processes erosion climate and sea level which together shaped the topography of europe the objective of this programme is to quantify natural hazards by incorporating data interactive modelling focused on the lithosphere memory and neotectonics with special attention on the thermo mechanical structure of the lithosphere mechanisms controlling large scale plate boundaries and intraplate deformations anomalous subsidence and uplift and links with surface processes and topography evolution

constraints from moho geometry and crustal thickness on the geodynamic origin of the vrancea seismogenic zone romania abstract reprocessing of industry deep seismic reflection data ramnicu sarat and braila profiles from the se carpathian foreland of romania provides important new constraints on geodynamic models for the origin of the intermediate depth vrancea seismogenic zone vsz mantle 70 200 km earthquakes of the vsz are characterized by high magnitudes greater than 6 5 frequent occurrence rates approximately 25 years and confinement in a very narrow 30 70 200 km 3 near vertical zone atypical for a wadati benioff plane located in front of the orogen these two deep 20 s seismic reflection profiles 70 km length across the foreland reveal 1 a high amplitude gently east dipping reflection across most of the section from what we interpret to be the moho at 15 s 40 42 km on the ramnicu sarat line to 16 s 47 48 km on the braila line 2 a thick sedimentary cover increasing in thickness from east 1 s 800 m to west 7 5 s 14 km 3 an eastward increase in crustal thickness from 38 km near vsz to 45 km 4 seismic and topographic evidence for a newly imaged possibly seismically active basement fault with a surface offset of 30 m observed on the ramnicu sarat line 5 a lack of notable west dipping structures in the crust and across the moho and 6 variable displacements on peceneaga camena fault of 5 km at moho and 200 m at the basement sedimentary cover contact these observations appear to argue against recent models for west dipping subduction of oceanic lithosphere at or in the vicinity of the vrancea seismogenic zone given the lack of west dipping fabrics in the lower crust and across the crust mantle boundary consequently one possible explanation for the geodynamic origin of vsz could be partial delamination of the continental lithosphere in an intra plate setting along a sub horizontal lithospheric interface in the carpathian hinterland that likely involves remnant lithospheric coupling between the crust and uppermost mantle in the foreland

geodynamics and intermediate depth seismicity in vrancea the south eastern carpathians current state of the art abstract the vrancea region of the south eastern carpathians is a remarkable site of intra continental intermediate depth seismicity a large set of geological geophysical and geodetic observations has been accumulated for the last few decades and utilised to improve our knowledge of the shallow and deep structures beneath vrancea the crustal and mantle dynamics and the linkage between deep and surface processes in the region in this article we review geology and tectonics of the vrancea region including post collisional to recent deformations syn to post collisional magmatism and orogenic exhumation along the east and south carpathians the regional seismicity is analysed and the recent seismic studies including reflection refraction body and surface wave tomography are reviewed we discuss new geodetic measurements of horizontal and vertical movements in the region geoelectric studies density gravity and thermal modelling qualitative and quantitative including retrospective geodynamic models developed for vrancea are analysed the knowledge of regional tectonics geodynamics seismicity lithospheric deformation and stress regime in the vrancea earthquake prone region assists in an assessment of strong ground motion seismic hazard and risk the earthquake simulation seismic hazard and earthquake forecasting models have also been reviewed providing a link between deep geodynamic processes and their manifestation on the surface finally we discuss unresolved problems in vrancea in order to improve our understanding of the regional evolution present tectonics mantle dynamics intermediate depth seismicity and surface manifestations of the lithosphere dynamics and to enhance our ability to forecast strong earthquakes in the vrancea region the problems to be solved include i the origin of the high velocity body revealed by seismic tomography studies oceanic versus continental ii the lithospheric scale mechanism driving the miocene subsidence of the transylvania basin iii sub crustal structure between 40 and 70 km iv contemporary regional horizontal and vertical movements and v a comprehensive seismic hazard assessment in the region

kinematics of retreating subduction along the carpathian arc romania kinematic axes and resultant vectors of displacement along the carpathian arc and the apuseni mountains aid in the reconstruction of retreating subduction along the carpathians the recent vertical position of the subducted slab below the vrancea area of the eastern carpathians represents the final rollback stage of a small fragment of oceanic lithosphere formerly situated between the moesian and east european plates the ages and locations of the eruption centers of the andesitic volcanic chain along the carpathian arc in the overriding plate as well as the thrust directions are used as markers to reconstruct the rollback area of the subducted slab between the moesian and east european plates

seismic crustal structure between the transylvanian basin and the black sea romania abstract in order to study the lithospheric structure in romania a 450 km long wnw ese trending seismic refraction project was carried out in august september 2001 it runs from the transylvanian basin across the east carpathian orogen and the vrancea seismic region to the foreland areas with the very deep neogene focsani basin and the north dobrogea orogen on the black sea a total of ten shots with charge sizes 300 1500 kg were recorded by over 700 geophones the data quality of the experiment was variable depending primarily on charge size but also on local geological conditions the data interpretation indicates a multi layered structure with variable thicknesses and velocities the sedimentary stack comprises up to 7 layers with seismic velocities of 2 0 5 9 km s it reaches a maximum thickness of about 22 km within the focsani basin area the sedimentary succession is composed of 1 the carpathian nappe pile 2 the post collisional neogene transylvanian basin which covers the local late cretaceous to paleogene tarnava basin 3 the neogene focsani basin in the foredeep area which covers autochthonous mesozoic and palaeozoic sedimentary rocks as well as a probably permo triassic graben structure of the moesian platform and 4 the palaeozoic and mesozoic rocks of the north dobrogea orogen the underlying crystalline crust shows considerable thickness variations in total as well as in its individual subdivisions which correlate well with the tisza dacia moesian and north dobrogea crustal blocks the lateral velocity structure of these blocks along the seismic line remains constant with about 6 0 km s along the basement top and 7 0 km s above the moho the tisza dacia block is about 33 to 37 km thick and shows low velocity zones in its uppermost 15 km which are presumably due to basement thrusts imbricated with sedimentary successions related to the carpathian orogen the crystalline crust of moesia does not exceed 25 km and is covered by up to 22 km of sedimentary rocks the north dobrogea crust reaches a thickness of about 44 km and is probably composed of thick eastern european crust overthrusted by a thin 1 2 km thick wedge of the north dobrogea orogen