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

pre neogene controls on present day fault activity in the west netherlands basin and roer valley rift system southern netherlands role of variations in fault orientation in a uniform low stress regime the west netherlands basin wnb and the neighbouring roer valley rift system rvrs form the most prominent tectonic features of the onshore netherlands the two basins have a common tectonic origin and similar mesozoic evolution their neogene quaternary evolution however is markedly different while the wnb is tectonically seismically inactive and is characterised by uniform neogene quaternary subsidence in the rvrs fault controlled intra plate deformation has taken place since late oligocene times with pronounced seismic activity considering the present day ne sw regional extension as well as the similar basin orientation and mesozoic evolutions one would not expect strikingly different neotectonic activity in the two basins detailed analysis of mesozoic tertiary and quaternary fault patterns revealed that 1 the palaeozoic mesozoic tectonic fabric has great influence on the cenozoic deformation style of the basin system 2 present day faulting in the rvrs is related to the reactivation of pre existing faults and 3 the mesozoic fault pattern is slightly different in the two basins using a novel technique three dimensional 3 d slip tendency analysis we aim to determine whether these differences in fault orientation are substantial enough to produce significantly different resolved stresses along the faults this modelling not only tests a common geological phenomena but indirectly also delivers important constraints regarding the origin of faulting in the study area during the analysis 3 d geometric models of 84 mapped faults were investigated the results of this recently developed modelling technique reveal that the faults in both basins should behave similarly under the condition of a laterally homogeneous regional stress field which is in disagreement with the present day tectonic activity of the region on the other hand the modelling also reveals that the predicted tendency of slip is very sensitive to the ratio of the minimum horizontal and the vertical stress s as an explanation for the pronounced fault activity in the rvrs and the tectonic quietness of the wnb it is proposed that either the regional extension in the wnb is weaker in term of higher s ratio than that in the rvrs or the slip thresholds in the two basins are different the study emphasised that differentiation in the tectonic evolution has already started in the tertiary therefore it is reasonable to assume that the different tectonic stress field and or slip threshold between the two areas is directly related to the origin of the cenozoic rifting in the rvrs several hypotheses are discussed to account for these two possibilities taking into account the lithospheric structure and the cenozoic tectonic evolution of the two basins as well as surrounding areas 2004 elsevier ltd all rights reserved

joint geophysical and petrological models for the lithosphere structure of the antarctic peninsula continental margin summary the antarctic peninsula ap is a composite magmatic arc terrane formed at the pacific margin of gondwana through the late mesozoic and cenozoic subduction has stopped progressively from southwest to northeast as a result of a series of ridge trench collisions subduction may be active today in the northern part of the ap adjacent to the south shetland islands the subduction system is confined by the shackleton and hero fracture zones the magmatic arc of the ap continental margin is marked by high amplitude gravity and magnetic anomaly belts reaching highest amplitudes in the region of the south shetland islands and trench the sources for these anomalies are highly magnetic and dense batholiths of mafic bulk composition which were intruded in the cretaceous due to partial melting of upper mantle and lower crustal rocks 2 d gravity and magnetic models provide new insights into crustal and upper mantle structure of the active and passive margin segments of the northern ap our models incorporate seismic refraction constraints and physical property data this enables us to better constrain both moho geometry and petrological interpretations in the crust and upper mantle model along the dss 12 profile crosses the ap margin near the anvers island and shows typical features of a passive continental margin the second model along the dss 17 profile extends from the drake passage through the south shetland trench islands system and bransfield strait to the ap and indicates an active continental margin linked to slow subduction and on going continental rifting in the backarc region continental rifting beneath the bransfield strait is associated with an upward of hot upper mantle rocks and with extensive magmatic underplating

temporal variation in the shear wave anisotropy detected using the accurately controlled routinely operated signal system across 1 temporal variation in shear wave anisotropy was detected in a monitoring experiment using an accurately controlled routinely operated signal system accurately controlled routinely operated signal system across we conducted an experiment that lasted for 15 months between january 2000 and april 2001 at a site near the nojima fault which ruptured during the 1995 kobe earthquake mw 7 2 yamaoka et al 2001 ikuta et al 2002 two vibration sources that generated 2 105 n with centrifugal force which were firmly fixed on the ground were used to emit elastic waves seismometers deployed at the bottom of 800 m and 1700 m deep boreholes near the across sources were used to receive the signal we extracted small temporal changes in the travel time of the p and s wave by calculating cross spectral density among the records every hour during the experiment sudden delays in travel times for the s wave were observed when the 2000 western tottori earthquake mw 6 6 and the 2001 geiyo earthquake mw 6 4 occurred their epicenters were 165 and 215 km away from the site respectively the travel times of the s waves between the surface and the bottom of 800 m deep borehole abruptly slowed down and gradually speeded up with each earthquake the delay in s was about 0 4 and 0 1 of the absolute travel time for the western tottori earthquake and the geiyo earthquake respectively the delays were polarized in a direction perpendicular to the nojima fault in both cases this indicates that the density of the cracks parallel to the fault increased in association with the earthquakes these cracks can be regarded as opened by the increase in pore pressure the small changes in p wave velocities support this interpretation an additional experiment to determine the static anisotropy revealed that there was a preferred orientation of the cracks that was enhanced with the strong shaking of earthquakes in the middle distance

high resolution 40 ar 39 ar geochronology of volcanic rocks from the siebengebirge central germany implications for eruption timescales and petrogenetic evolution of intraplate volcanic fields a key parameter in understanding mantle dynamics beneath continents is the temporal evolution of intraplate volcanism in response to lithospheric thinning and asthenospheric uplift to contribute to a better understanding of how intraplate volcanic fields evolve through time we present a high precision 40ar 39ar age dataset for volcanic rocks from the siebengebirge volcanic field svf from central germany one of the best studied and compositionally most diverse intraplate volcanic fields of the cenozoic central european volcanic province cevp petrological and geochemical investigations suggest that the formation of the different rock types that occur in the svf can be explained by a combination of assimilation and fractional crystallisation processes starting from at least two different parental magmas with different levels of silica saturation alkali basaltic and basanitic and originating from different mantle sources these evolved along two differentiation trends to latites and trachytes and to tephrites and tephriphonolites respectively in contrast to their petrogenesis the temporal evolution of the different svf suites is poorly constrained previous k ar ages suggested a time of formation between about 28 and 19 ma for the mafic rocks and of about 27 to 24 ma for the differentiated rocks our results confirm at high precision that the differentiated lithologies of both alkaline suites 40ar 39ar ages from 25 3 0 2 ma to 25 9 0 3 ma erupted contemporaneously within a very short time period of 0 6 ma whereas the eruption of mafic rocks basanites lasted at least 8 ma 40ar 39ar ages from 22 2 0 2 ma to 29 5 0 3 ma this implies that felsic magmatism in the central svf was likely a single event possibly triggered by an intense phase of rifting and that ongoing melting and eruption of mostly undifferentiated mafic lavas dominate the 8 ma long magmatic history of this region among the mafic lavas most basanites and tephrites predate the alkali basalts and hawaiites suggesting an overall temporal evolution towards less sio2 undersaturated primary melts and increasing degrees of melting over time the peak in alkali basaltic to hawaiitic magmatism slightly post dates the flare up of genetically related felsic magmatism by no more than 1 ma this is consistent with a model in which the magmatic plumbing system erupted successively from upper to lower levels i e from more evolved to more primitive compositions one young age for a basanitic sample suggests that silica saturation decreased again towards the end of volcanic activity this chronology of volcanic events is in good agreement with previous models suggesting continuous lithospheric thinning beneath the svf as a response to an extensional regime and asthenospheric uplift in the northern alpine realm

the rhinegraben extension subsidence and shoulder uplift abstract we apply a numerical model of the thermal evolution of a continental lithosphere undergoing extensional deformation to the rhinegraben using reasonable parameters the results of computations are in agreement with the present configuration of the rift and of its shoulders as well as with their evolution since the oligocene contrasting evolutions are reconstructed in the northern and southern rhinegraben whereas the northern history is accounted for by a simple model of homogeneous stretching of the lithosphere the history of the southern rhinegraben cannot be explained without introducing two main periods of heterogeneous stretching the results are locally supported by structural analyses of extensional patterns factors of extension average 1 2 in the axial portion of the rhinegraben and 1 15 for the whole rift section suggesting that the total amount of e w extension reaches 6 km

synthetic seismograms for a complex crustal model the algorithm of the original reflectivity method has been vectorized and implemented on a cdc cyber 205 computer calculation times are shortened by a factor of 20 to 30 compared with a general purpose computer with a capacity of several million floating point operations per second mflop the rapid calculation of synthetic seismograms for complex models high frequency sources and all offset ranges is a provision for modeling not only particular phases but the whole observed wavefield as an example we model refraction data of the black forest southwest germany and are able to derive rather tight constraints on the physical properties of the lower crust

scattering parameters of the lithosphere below the massif central france from teleseismic wavefield records summary teleseismic p wave recordings are analysed in the frequency range 0 3 6 hz to derive structural statistical parameters of the lithosphere underneath the french massif central for this we analyse diverences in frequency dependent intensities of the mean wavefield and the fluctuation wavefield it is possible to discriminate a weak fluctuation regime of the wavefield in the frequency range below 1 hz and a strong fluctuation regime starting above 1 hz and continuing to higher frequencies the observed wavefield fluctuations in the frequency range 0 3 3 hz can be explained by scattering of the teleseismic p wave front at elastic inhomogeneities in the lithosphere a statistical distribution of the inhomogeneities is assumed and the concept of random media is applied the lithospheric structure under the massif central can be described as a 70 km thick heterogeneous layer with velocity fluctuations of 3 7 per cent and correlation lengths of the heterogeneities of 1 16 km

a deep reflection seismic line across the northern rhine graben abstract two reflection seismic lines across the tertiary rhine graben in central europe were recorded in 1988 as a joint venture of the french ecors and the german dekorp deep seismic reflection programs in this paper the line across the northern graben is presented the main results are the asymmetry of the graben as documented by the sedimentary fill is accompanied by asymmetric features throughout the entire deep crystalline crust a thin 3 7 s twt reflective lower crust in the east a thick 5 5 s twt relatively transparent lower crust in the west total crustal thicknesses of 8 7 s twt in the east vs 10 5 s twt in the west provided a laterally homogeneous crust existed prior to rifting significant differences in upper and lower crustal thinning must be postulated extension occurred along localized shear zones that are located in the upper crust and at the crust mantle boundary the entire lower crustal layer acts as a decoupling zone

beryllium 7 in soils and vegetation along an arid precipitation gradient in owens valley california 1 beryllium 7 is a potentially powerful tracer of atmospheric deposition and recent sediment transport but the quantity and distribution of 7be on arid landscapes have not been described we measured 7be in soil vegetation and dust in owens valley california and describe its distribution in aridisols and mollisols to evaluate its potential as a sediment tracer in desert environments beryllium 7 in vegetation and the upper few cm of soil is low but detectable 20 becquerels bq m 2 surface inventories of 7be at sites on the valley floor vary by a factor of five between the end of the rainy season april and the end of the dry season november in mollisols live grasses hold 50 bq 7be m 2 which is on the order of half of the total springtime surface inventory we find that within site variability at the 5 m scale is 5 to 22 1 relative standard error and can be explained by localized rain shadowing and erosion but between site variability at the km scale can be explained by differences in rainfall our alpine site has more than triple the inventory that is predicted from the rainfall 7be flux relationship that we generate using our springtime soil measurements and previously reported deposition data dust deposition does not appear to contribute significantly to 7be inventories but anomalously high 7be on the eastern flank of the sierras may be explained by a higher altitude air mass source and better scavenging efficiency of snow

crustal structure and dynamics in the rhine graben and the alpine foreland summary the rhine graben rift stretches for 300 km from basel to frankfurt the axis of maximum subsidence switches from west in the southern graben to east in the northern graben subsidence in the south began in the upper eocene and was interrupted in the mid miocene by a broad uplift of 1 1 5 km in the vosges schwarzwald black forest region whereas subsidence in the north proceeded continuously from the lower oligocene to the present a combined geophysical and geological interpretation of the rhine graben is presented in the form of a 3 d gravity model and 2 d flexural plate modelling from the alps across the alpine foreland to the rhenish massif modelling is based on crustal structure revealed by geologic gravity and seismic data including ecors dekorp and egt profiles the 3 d gravity modelling supports a modest density contrast of 0 3 g cm 3 at the crust mantle boundary since there is no evidence of a large scale upper mantle anomaly a dense lower crust 2 9 3 0 g cm 3 is proposed as the cause of this modest density contrast the presence of a dense mafic lower crust in south west germany is corroborated by lower crustal xenoliths elevated p wave velocities 6 7 7 2 km s 1 and high poisson s ratios 0 26 0 29 residual gravity and magnetic data reveal strong crustal heterogeneities particularly from the dense magnetic saxothuringian terrane to the light non magnetic moldanubian terrane the polarity of the asymmetric rhine graben reverses at this variscan tectonic boundary light graben fill can account for nearly the entire 20 40 mgal short wavelength gravity minimum but the presence of intrusive bodies ranging from granitic to mafic composition can also strongly influence the local gravity field 2 d modelling of the flexure of the european lithosphere along seven 1000 km long profiles indicates a flexural bulge of 1 1 5 km in the alpine foreland of southern germany which corresponds to an ene trending moho uplift of the same magnitude and to a band of free air gravity highs longer flexural wavelengths in the east indicate increasing lithospheric rigidity and increasing elastic thickness towards the bohemian massif the vosges schwarzwald dome is interpreted as the intersection of the oligocene rhine graben rift and associated rift flank uplift with the mid miocene flexural bulge

beryllium 7 wet deposition variation with storm height synoptic classification and tree canopy state in the mid atlantic usa short lived fallout isotopes such as beryllium 7 7be are increasingly used as erosion and sediment tracers in watersheds 7be is produced in the atmosphere and delivered to the earth s surface primarily in precipitation however relatively little has been published about the variation in 7be wet deposition caused by storm type and vegetation cover our analysis of precipitation throughfall and sediments in two forested headwater catchments in the mid atlantic usa indicates significant variation in isotope deposition with storm type and storm height individual summer convective thunderstorms were associated with 7be activity concentrations up to 5 0 bq l 1 in precipitation and 4 7 bq l 1 in throughfall while single event wet depositional fluxes reached 168 bq m 2 in precipitation and 103 bq m 2 in throughfall storms originating from the continental usa were associated with lower 7be activity concentrations and single event wet depositional fluxes for precipitation 0 7 1 2 bq l 1 and 15 8 65 0 bq m 2 and throughfall 0 1 0 3 bq l 1 and 13 5 98 9 bq m 2 tropical systems had relatively low activity concentrations 0 2 0 5 bq l 1 in precipitation and 0 2 1 0 bq l 1 in throughfall but relatively high single event depositional fluxes due to large rainfall volumes 32 8 67 6 bq m 2 in precipitation and 25 7 134 bq m 2 in throughfall the largest sources of 7be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height 7be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer 175 1450 bq kg 1 we conclude the dominant source of variation on event level 7be deposition is storm type our results illustrate the complex relationships between 7be deposition in precipitation and throughfall and demonstrate event scale relationships between the 7be in precipitation and on suspended sediment copyright 2015 john wiley sons ltd

gravity interpretation along seismic reflection profile dekorp 9 n northern rhine graben a 2 d gravity model incorporating geophysical and geological data is presented for a 110 km long transect across the northern rhine graben coinciding with the 92 km long dekorp 9 n seismic reflection profile the upper rhine graben is marked by a prominent nne striking negative anomaly of 30 40 mgal on bouguer gravity maps of sw germany surface geological contacts borehole data and the seismic reflection profile provide boundary constraints during forward modelling short wavelength 5 10 km gravity features can be correlated with geologic structures in the upper few km at deeper levels the model reflects the asymmetry visible in the seismic profile a thicker mostly transparent lower crust in the west and a thinner reflective lower crust in the east from west to east moho depth changes from 31 to 26 28 km the entire 40 mgal minimum can be accounted for by the 2 3 km of light sedimentary fdl in the graben which masks the gravitational effects of the elevated moho the thickened lower crust in the west partly compensates for the mass deficit from the depressed moho a further compensating feature is a relatively low density contrast at the crust mantle boundary of 0 25 g cm 3 the variscan must displays heterogeneity along the profile which cuts at an angle across the strike of variscan structures the asymmetry of the integrated crustal model both at the surface and at depth suggests an asymmetric mechanism of rift development

correlation between shear wave upper mantle structure and tectonic surface expressions application to central and southern germany we have inverted fundamental mode rayleigh waveforms in the frequency range from 20 to 100 s to obtain a three dimensional s velocity distribution beneath central and southern germany the data come from 27 teleseismic events recorded at 17 broadband stations in germany and adjacent areas this results in 56 paths between pairs of stations each pair lying on the same great circle with an epicenter the phase differences between the waveforms recorded at a pair of stations have been inverted directly for the path averaged s velocity perturbation between the two stations all path models were then combined into a single three dimensional model the most prominent features of the obtained model are 1 low velocities beneath the eger graben which are an expression of the deep reaching rift structure 2 high velocities between 40 and 120 km depth beneath northern bavaria caused by an apparent thickening of the lithosphere toward the south 3 high velocities in the uppermost mantle beneath the southern rhine graben area presently inactive with respect to rifting suggesting the absence of present upwelling hot mantle material and 4 low velocities beneath the presently experiencing rifting northern branch of the central european rift system including the northern part of the rhine graben and the rhenish massif west of the river rhine with the volcanic fields of the eifel these reduced velocities indicate a broad updoming of the lithosphere asthenosphere boundary our model suggests a strong correlation between upper mantle s wave structure at depths down to 200 km and tectonic surface expressions

properties of the lower crust from modeling refraction and reflection data data of a refraction and a reflection seismic survey in the black forest of southwest germany are used for extensive one and two dimensional modeling the data are available along approximately the same line and therefore the same piece of crust is probed by two seismic methods we utilize this favorable circumstance for detailed model calculations concerning both data sets in this paper we focus on the lower crust its properties vary on the scale of a wavelength and thus full solutions of the elastic equations are required we use the reflectivity method for the evaluation of refraction seismograms and numerical solutions of the acoustic wave equation for the reflection response the lamellae of the lower crust appear as reflecting elements of several hundred meters length randomly distributed in space rocks with extremely low velocities 5 6 km s must be present indicating that anisotropy and or fluids play an important role in the lower crust ideas concerning lower crustal formation evolution and extinction of lamellaetion are developed

crustal evolution of the rhinegraben area 1 exploring the lower crust in the rhinegraben rift by unified geophysical experiments abstract unified geophysical investigations of the lithosphere in the rhinegraben rift system have revealed new details of the lower crust and its role in the rifting process the new findings allow an assessment of the compatibility of four different geophysical notions and properties of the lower crust 1 1 the lower crust as the layer beneath the conrad discontinuity with a p wave velocity of about 6 5 km s or greater refraction seismics 2 2 the laminated band of reflections as seen in the near vertical reflection seismic experiments in many parts of the continents 3 3 the ductile part of the crust below the brittle ductile transition devoid of earthquakes in seismically active regions 4 4 the electrical conductivity of the lower crust indicative of dry or wet conditions or still unknown conduction phenomena in the rhinegraben area the lamination of the lower crust serves as an outstanding marker of deep tectonic activity during the rifting process in which the crust of the rhinegraben rift system has been subjected to three different natural dynamic processes 1 uplift by 2 to 3 km with subsequent erosion of the rhinegraben shoulders black forest and vosges mountains caused decompression possibly leading to the formation of a low velocity high electrical conductivity zone right on top of the laminated lower crust beneath the elevated shoulders of the black forest 2 the brittle crystalline wedge of the graben proper subsided nearly undeformed into the lower crust which became about 5 to 7 km thinner below the graben than below the shoulders 3 the deepest hypocentres in the black forest dinkelberg area if projected onto the neighbouring reflection profile would be located 7 to 8 km within the laminated lower crust beneath the southern black forest indicating a discrepancy between the top of the lower crust as defined by the brittle ductile transition as seen by the deepest earthquakes and by the top of the laminated reflection band the rhinegraben rift system reveals the properties and behaviour of the lower crust under a wide variety of tectonic situations

the late variscan control on the location and asymmetry of the upper rhine graben the nne trending upper rhine graben urg of the european cenozoic rift system developed from c 47 ma onwards in response to changing lithospheric stresses in the northwestern foreland of the alps the composite graben structure consists of three segments each c 100 km long and 30 40 km wide but flares to c 60 km near its southern and to c 80 km near its northern termination normal faulting induced a total extension of 5 8 km of the 1 2 km thick mesozoic sedimentary franconian platform and underlying variscan basement rocks however distribution of an up to 3 5 km thick sedimentary graben fill and cumulative displacements near eastern and western main border fault systems suggest that subsidence of the graben floor and shoulder uplift created strong cross sectional asymmetries cumulative w down displacements 3 km along strongly segmented transfer faults in the east contrast with e down displacements 600 km long zone that delimits the trailing edge of a sw moving lithospheric block in the urg area ne sw oriented seismic anisotropy at sublithospheric depths of c 60 80 km suggest active mantle flow in this direction as a possible driving force for the reactivation of pre graben lithospheric shear zones

regional three dimensional gravity investigations in the black forest southwest germany abstract the gravimetric pre surveys of the continental deep drilling project ktb yielded results different to those hoped for at the beginning of the program firstly 2 d calculations based on a refraction seismic interpretation allowed a comparison of gravity effects on a 160 km long profile but despite the fact that in the 2 d model granitic bodies were added at the earth s surface we only obtained a regional gravitational fit with strong deviations on a local scale secondly a gravimetric field survey in the region around haslach yielded rather poor indications of the geological structures in the 5 15 km depth interval which is in the context of the ktb of significant interest therefore all available information derived from geological and tectonic hypotheses and from reflection and refraction seismic interpretation were combined in a regional 3 d density model for the local anomalies the distribution of granite and gneiss bodies known from surface geology was added model bodies from an earlier regional study in southern germany which combined gravimetric and seismic results the moho undulations and the density of the lower crust and upper mantle were taken as additional model parameters in order to discuss regional features the kraichgau anomaly in the north of the black forest is modelled from a 2 d hypothesis as a body with an unusually high density and with a considerable lateral extent this approach demonstrates that evidence concerning the density contrast of anomalous masses can be found if boundary conditions are considered in the construction of the model

spatio temporal changes in seismic velocity associated with the 2000 activity of miyakejima volcano as inferred from cross correlation analyses of ambient noise abstract miyakejima volcano japan showed strong and interesting volcanic activities in 2000 with the occurrence of dike intrusions caldera formation and a large amount of gas emission to understand temporal changes of the volcanic structure associated with this activity we apply ambient noise correlation analyses to the seismic records of five seismic stations at miyakejima volcano from july 1999 to december 2002 we calculate cross correlation functions ccfs for eight available station pairs at frequency bands of 0 4 0 8 hz and 0 8 1 6 hz and retrieve the rayleigh waves propagating with a group velocity of about 1 0 km s comparing ccfs obtained for each day with the reference ccfs that are calculated from a few months of data we estimate seismic velocity changes before and after the 2000 activity results at the two frequency bands show seismic velocity increase and decrease shallow structure at the volcanic edifice on the flanks experienced a seismic velocity increase up to 3 3 on the other hand the regions located close to the collapsed caldera show a seismic velocity decrease down to 2 3 to understand the mechanisms that may introduce these seismic velocity increase and decrease we examine several possible mechanisms of the velocity changes stress changes due to volcanic pressure sources and caldera formation and topographic changes by using the deflation sources previously determined from gps data we calculate the stresses at depths of 0 km and 1 km at the volcano the results suggest that the seismic velocity increases observed at seismic paths on the volcanic flank are explained by the compression caused by the deflation sources associated with magma activity in 2000 stress sensitivities of the seismic velocity changes are estimated to be 1 5 10 2 to 2 2 10 2 mpa 1 and 4 6 10 3 to 2 4 10 2 mpa 1 at frequency bands of 0 4 0 8 hz and 0 8 1 6 hz respectively which are in the range of the previously reported results our three dimensional numerical calculations on seismic wave propagation show that the seismic velocity decreases observed at seismic paths crossing the collapsed caldera can be explained by topographic changes introduced by a caldera we further suggest that the seismic velocity decreases detected around the regions close to the caldera may originate from the dilated regions cause by formation of the caldera

a new constraint on the composition of the topmost continental mantle anomalously different depth increases of p and s velocity summary compared to clear crustal p and s waves as well as a strong refracted pn wave propagating in the topmost mantle i e 10 to 15 km below the moho an anomalously weak appearance of the corresponding refracted shear wave sn is observed on refraction seismic profiles in sw germany france coastal maine ne united states and fennoscandia it is possible that the observation of pn pmp ratios close to unity combined with small sn sms ratios i e small sn amplitudes is typical for the continental uppermost mantle since this was observed for quite different types of continental crust it is shown that the observed phenomenon is not a source effect several possible causes to explain the observations are studied also with the aid of synthetic seismograms the effects of temperature attentuation and anisotropy have been investigated their influence cannot explain the observations the most likely candidate is a depth increasing vp vs ratio an increase in the order of 0 027 over a depth range of 10 km forcing p and s waves to propagate on different paths in the topmost mantle the observed phenomenon provides new constraints on the change of composition with depth for the crust mantle transition zone with basalt depletion as the most likely explanation

3d lithosphere scale density model of the central european basin system and adjacent areas abstract to analyze the first order structural features characterizing the crust and the lithospheric mantle below the central european basin system and adjacent areas a new lithosphere scale 3d structural density model has been derived that integrates published knowledge with 3d gravity modeling with this study we aim to integrate previous results on sub domains of the study area and regional results of limited resolution in conjunction with 3d gravity analysis to derive the configuration of the lower crust and lithospheric mantle that is consistent with the known density distribution of the sediment fill and with observed deep seismic data as well as with observed gravity the derived 3d density model resolves the internal configuration of the crystalline crust below the central european basin system and adjacent areas at the regional scale and shows that the crystalline crust is characterized by a layered structure the upper to middle crystalline crust is characterized by relatively low seismic p wave velocities and densities it shows strong variations in thickness across the study area that partly correlate spatially with the inherited segmentation in response to crustal amalgamation this upper to middle crystalline crust is underlain by a continuous high density high velocity lower crustal layer locally more than 30 km thick beneath the east european craton and generally decreasing in thickness from the older to the younger tectonic domains though the thickness of this high density lower crust is generally small below the permo cenozoic central european basin system it can reach locally more than 18 km below the northeast german and the norwegian danish basins the derived depth to the lithosphere asthenosphere boundary confirms previously proposed geometries and is up to 230 km deep beneath the precambrian domain but less than 100 km deep beneath the phanerozoic domains implying that the average thermal gradient is higher in the phanerozoic lithosphere than in the precambrian part

lithospheric cross sections of the european cenozoic rift system abstract the lithospheric structure of the european cenozoic rift system ecris is presented in transects through the southern rhine graben and the rhenish massif hessen depression emphasizing the geophysical structure of the lithosphere based on seismic refraction reflection investigations teleseismic tomography electromagnetic depth sounding models and gravity aeromagnetic earthquake uplift subsidence and heat flow data the rift is clearly expressed in the rhine graben but is not evident at the surface in the area of the rhenish massif where its existence is indicated by seismicity it is characterized by abnormal crustal and upper mantle structures which vary considerably in horizontal direction for example under the rhine graben the crust is thinned to 25 km but at 40 km depth anomalously high velocities are observed in contrast beneath the rhenish massif the crust is thickened to 35 37 km and under its eastern part a high velocity thin upper mantle slice is seen at 30 km depth within the lower crust which towards the hessen depression is gradually replaced by normal variscan mantle with the moho near 30 km depth under the western part of the rhenish massif p and s wave velocities are reduced below 50 km depth which is not seen east of the rhine river under the rhine graben the existence of a low velocity upper mantle above 100 km cannot be generalized but is restricted to confined regions

crustal magnetic anomalies this quadrennial report departs in format from its predecessors earlier reports provided brief descriptions of the entire range of topics on crustal magnetic anomalies following guidelines established by the agu we instead focus our discussion on only a few selected topics our abbreviated list of references reflects this restricted focus a more comprehensive bibliography can be obtained from the authors as noted subsequently the past quadrennium was distinguished by a significant change in the scale and scope of crustal magnetic anomaly research advances in instrumentation navigation and data processing techniques resulted in increasing use of two dimensional anomaly maps rather than profile data although maps are commonly used in aeromagnetic studies of continental areas their use in the ocean basins has been limited until recently the other important change has been a trend towards increased integration of magnetic anomaly data with gravity seismic geochemical remote sensing and geologic data to enhance the interpretation and reduce the ambiguity of magnetic field data

3 d structure of the lithosphere beneath the southern rhine graben area abstract the 3 d velocity structure of the lithosphere asthenosphere system beneath the southern rhine graben area is imaged by inverting p wave traveltime residuals of teleseismic events recorded by a dense network of short period stations the upper part of the lithosphere marked by velocity anomalies orientated along the graben strike can be related to the development of the graben these upper 50 km display stronger lateral heterogeneities than the weak anomalies observed at deeper levels which show roughly an e w orientation the teleseismic inversion models yield no indications for significantly reduced seismic p wave velocities in the upper mantle as could be expected from an actively upwelling mantle diapir located beneath the southern rhine graben area the observation of generally weak p wave velocity variations at greater depth indicates a rather smooth transition from the lower lithosphere to the upper asthenosphere the observed heterogeneities in the 25 50 km depth range may be related to partial melts which intruded the mantle lithosphere during the middle and late miocene these melts cooled and solidified since that intrusion the rifting and thermal doming stage of the rhine graben ceased at the end of the miocene

a subsurface structure change associated with the eruptive activity at sakurajima volcano japan inferred from an accurately controlled source temporal variations of green functions associated with the eruptive activity at sakurajima volcano japan were estimated using an accurately controlled routinely operated signal system across we deconvolved 400 s waveforms of the across signal at nearby stations by a known source time function and stacked the results based on the time relative to individual eruptions and the eruption intervals the quantities obtained by this procedure are green functions corresponding to various stages of the eruptive activity we found an energy decrease in the later phase of the green functions in active eruptive periods this energy decrease localized in the 2 6 s window of the green functions is difficult to explain by contamination from volcanic earthquakes and tremors the decrease could be more reasonably attributed to a subsurface structure change caused by the volcanic activity

the deep thermal field of the upper rhine graben abstract the upper rhine graben has a significant socioeconomic relevance as it provides a great potential for geothermal energy production the key for the utilisation of this energy resource is to understand the controlling factors of the thermal field in this area we have therefore built a data based lithospheric scale 3d structural model of the upper rhine graben and its adjacent areas in addition 3d gravity modelling was performed to constrain the internal structure of the crystalline crust consistent with seismic information based on this lithosphere scale 3d structural model the present day conductive thermal field was calculated and compared to measured temperatures our results show that the regional thermal field is mainly controlled by the configuration of the upper crust which has different thermal properties characteristic for the variscan and alpine domains temperature maxima are predicted for the upper rhine graben where thick insulating cenozoic sediments cause a thermal blanketing effect and where the underlying crustal units are characterised by high radiogenic heat production the comparison of calculated and measured temperatures overall shows a reasonable fit while locally occuring model deviations indicate where a larger influence of groundwater flow may be expected

deep reflection seismic data along the central part of the european geotraverse in germany a review abstract deep reflection seismic data collected in germany during the last three decades allow an insight into the structure of the variscan crust in germany although the crustal thickness is relatively constant reflection data revealed important internal structures most profiles show a poorly reflective upper crust disregarding fault zones while its lower part is characterized by many flat lying reflections but also dipping reflections in the upper and lower crust have been observed on dekorp reflection lines beneath the geothermal anomaly of urach an updoming of the reflective lower crust coinciding with a pronounced low velocity body can be observed near the suture zones between moldanubian saxothuringian and rhenohercynian abundant diffractions appear in the middle and lower crust one exception is found in the west where post variscan developments created the deep saar nahe trough the north variscan deformation front exhibits thin skinned tectonics west of the rhine while farther east more steeply dipping fault zones are observed in the north german basin just north of the variscides an industrial north south profile shows strong bands of reflections from both midcrustal and moho levels the distance between these bands becomes smaller to the north an industrial west east line of 90 km length in schleswig holstein south of kiel shows a thinning of the crust of about 6 km towards the north sea although the moho is not faulted the sediments reach down to at least 15 km

an interpretation of wide angle compressional and shear wave data in southwest germany poisson s ratio and petrological implications shear wave velocity especially when used with compressional wave velocity is an important constraint on estimates of the composition and physical state of the continental lithosphere we present shear velocity s models derived from high quality s wave data along three profiles in southwest germany which combine with existing p wave velocity p models to give poisson s ratio in the crust and uppermost mantle we then construct a laterally varying petrological model of the crust by comparing our p and s models with published laboratory measured rock velocities in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust but reaching a low of 0 15 in the black forest low p zone and varies laterally from 0 24 to 0 30 in the lower crust the average poisson s ratio of the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data implying a strong high low alternation of poisson s ratio in the lower crust this suggests that the lower crustal laminae represent mafic silicic compositional layering for example basic sills in an originally more quartz rich lower crust rather than alternating zones of high and low pore pressure there is no evidence for a shear wave low velocity zone lvz in the black forest mid crust despite the presence of a strong p wave lvz this suggests high quartz content and the presence of pore fluids at low not high pore pressure a clear p to s converted moho reflection pm s is visible on several shots indicating that the moho is at least locally a first order discontinuity no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle the petrological modeling indicates that the upper and middle crust are probably of granitic composition that the mid crustal low p zones have high quartz content and that the lower crust probably consists of granulites of laterally varying bulk composition from granodioritic to gabbroic the lower crust is more mafic in areas of high reflection density on seismic reflection profiles suggesting that the laminations are caused by mafic intrusions into the lower crust either prior to the variscan orogeny or during tertiary volcanic activity

temporal change of phase velocity beneath mt asama japan inferred from coda wave interferometry 1 we estimated the temporal changes of phase velocity of rayleigh waves extracted from cross correlations of s coda waves recorded at 12 stations around mt asama japan first we extracted a rayleigh wave by taking cross correlations of s coda waves for 315 regional earthquakes between october 2005 and february 2009 the dispersion curve of the rayleigh wave was measured and compared with the one extracted from 18 days of ambient seismic noise we found that both dispersion curves are consistent with each other demonstrating the dominance of the fundamental rayleigh waves we then divided the entire time period into sub periods each of which consists of 80 earthquakes to measure the temporal changes at frequencies between 0 3 and 0 6 hz the result shows the reduction of phase velocity by 1 5 and the subsequent recovery before the eruption of mt asama in 2008

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

structure of the crust and upper mantle beneath the central european rift system the crustal structure of the central european rift system has been investigated by seismic methods with varying success only a few investigations deal with the upper mantle structure beneath the rhinegraben the moho is elevated with a minimum depth of 25 km below the flanks it is a first order discontinuity while within the graben it is replaced by a transition zone with the strongest velocity gradient at 20 22 km depth an anomalously high velocity of up to 8 6 km s seems to exist within the underlying upper mantle at 40 50 km depth a similar structure is also found beneath the limagnegraben and the young volcanic zones within the massif central of france but the velocity within the upper mantle at 40 50 km depth seems to be slightly lower here the total crustal thickness reaches only 25 km the crystalline crust becomes extremely thin beneath the southern rhonegraben where the sediments reach a thickness of about 10 km while the moho is found at 24 km depth the pronounced crustal thinning does not continue along the entire graben system north of the rhinegraben in particular the typical graben structure is interrupted by the rhenohercynian zone with a normal west european crust of 30 km thickness evident beneath the north trending hessische senke a single ended profile again indicates a graben like crustal structure west of the leinegraben north of the rhenohercynian zone no details are available for the north german plain where the central european rift system disappears beneath a sedimentary sequence of more than 10 km thickness

subsidence analysis and modelling of the roer valley graben se netherlands abstract the roer valley graben southeastern netherlands forms the most northern branch of the european cenozoic rift system sedimentary backstripping of exploration wells provides control on vertical tectonic motions during the complex post paleozoic geodynamic evolution of the area the roer valley graben evolved by repeated reactivation of permo carboniferous fracture systems at least three episodes of extension related subsidence are recorded these occurred during the late permian early triassic 255 240 ma the middle jurassic 168 165 ma and the late cenozoic 36 0 ma a late jurassic early cretaceous stretching phase is weakly inferred from incomplete data crustal stretching values calculated from the tectonic subsidence curves can account for the reflection seismic controlled crustal configuration of the roer valley graben area results demonstrate a close relationship between the roer valley graben and the basins in the north sea during the mesozoic in contrast the cenozoic evolution of the roer valley graben is independent from that of the north sea and is related to the development of the rhine graben

the upper rhenish shield basement vosges upper rhinegraben and schwarzwald main structural features deduced from magnetic gravimetric and geological data abstract interpretation of magnetic and gravimetric data and correlations with geological observations on outcrops and in boreholes have enabled the construction of a geological sketch map of the pre westphalian basement in the area of the upper rhenish shield the map demonstrates the contrast between the heavy and magnetic saxothuringian characterized by palaeozoic units metamorphosed to varying degrees and intruded by early carboniferous basites and the lighter moldanubian consisting mainly of gneisses and granites geological structures and tectonic features are recorded beneath the mesozoic and cenozoic cover the present picture of the basement is mainly the result of late visean early namurian structural features represented by a linear arrangement of magmatic bodies and the distribution of strike slip and thrust faults the major structural features are the e w vittel lalaye lubine baden baden fault that marks the border between saxothuringian and moldanubian the n35 left lateral wrench fault system running along the present rhinegraben the n60 grain of the northern vosges and the saar basin and the s verging crustal thrusts of moldanubian

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

evolution and structure of the upper rhine graben insights from three dimensional thermomechanical modelling the evolution and geometry of the tertiary upper rhine graben were controlled by a continually changing stress field and the reactivation of pre existing crustal discontinuities a period of wnw ese extension in the late eocene and oligocene was followed by lateral translation from the early miocene onwards this study utilizes 3d finite element techniques to simulate extension and lateral translation on a lithospheric scale brittle and creep behaviour of lithospheric rocks are represented by elastoplasticity and thermally activated power law viscoplasticity respectively contact elements allocated with cohesion and frictional coefficients are used to describe pre existing zones of weakness in the elastic brittle field our results suggest that 1 extension is accommodated along listric border faults to midcrustal depth of 15 16 km beneath pure shear stretching occurs without a need for localized shear zones in lower crust and upper mantle 2 ductile flow at midcrustal depth across the graben accounts for the pronounced halfgraben morphology thereby the shape of the border faults their frictional coefficients and sedimentary loads have profound effects on the rate of ductile flow across the graben 3 horizontal extension of 8 8 5 km and sinistral displacement across the rift of 3 4 km are needed to accommodate the observed sediment thickness

environmental chemistry of beryllium 7 in addition to the stable isotope 9be be is also formed as two cosmogenic isotopes of interest to earth scientists cosmogenic be is formed primarily in the stratosphere from cosmic ray spallation of oxygen and nitrogen but some is produced in the troposphere and in situ on the surface of the earth production of cosmogenic be was hypothesized by peters 1955 soon after naturally occurring 7be was identified in precipitation by arnold and al salih 1955 and essentially concurrently and independently by goel et al 1956 10be t1 2 1 5 106 yr was first detected by arnold 1956 in marine sediment cores the 10be 7be production ratio is approximately 0 5 lal and peters 1967 after its formation in the atmosphere cosmogenic be adsorbs electrostatically to aerosols that may be washed out by precipitation and delivered to ecosystems the amount of cosmogenic be that reaches the surface of the earth is a function of production rate cosmic ray intensity stratosphere troposphere mixing circulation and advection within the troposphere and efficiency of removal from the troposphere wet and dry deposition feely et al 1989 since the discovery of cosmic ray produced be numerous researchers have gathered data on its 1 production 2 fluxes to the oceans and terrestrial ecosystems 3 distribution and inventory in soils snow sediments and vegetation and 4 geochemical behavior in 1955 peters suggested that the relatively long half life of 10be could make it useful for quantifying tertiary sedimentation rates and other surficial processes the focus of this chapter is the short lived radionuclide 7be t1 2 53 12 0 07 days jaeger et al 1996 due to its short half life relative ease of measurement and well defined source term 7be serves as a useful tool for tracing and quantifying environmental processes on the

seasonal controls on meteoric 7be in coarse grained river channels cosmogenic 7be is a natural tracer of short term hydrological processes but its distribution in upland fluvial environments over different temporal and spatial scales has not been well described we measured 7be in 450 sediment samples collected from perennial channels draining the middle of the connecticut river basin an environment that is predominantly well sorted sand by sampling tributaries that have natural and managed fluctuations in discharge we find that the 7be activity in thalweg sediments is not necessarily limited by the supply of new or fine grained sediment but is controlled seasonally by atmospheric flux variations and the magnitude and frequency of bed mobilizing events in late winter 7be concentrations in transitional bedload are lowest typically 1 to 3 bq kg 1 as 7be is lost from watersheds via radioactive decay in the snowpack in mid summer however 7be concentrations are at least twice as high because of increased convective storm activity which delivers high 7be fluxes directly to the fluvial system a mixed layer of sediment at least 8 cm thick is maintained for months in channels during persistent low rainfall and flow conditions indicating that stationary sediments can be recharged with 7be however bed mobilizing rain on snowmelt events in late spring can reset 7be amounts and concentrations in the channel as previously buried old sediment with low 7be is mixed into the thalweg we conclude that given proper temporal and spatial sampling 7be is a valuable tracer of seasonal timescale mass transport and exchange in coarse grained fluvial systems copyright 2013 john wiley sons ltd

new insight in the tectonics of the southern rhine graben jura region using local earthquake seismology 1 a new seismic data set was acquired using a dense temporary network of mobile seismic stations it is combined with existing seismological data for the southern rhine graben the data yielded some new focal mechanisms and allowed for a detailed local earthquake tomography these methods give new insight in the structure of the crust and stress conditions in the area by combining the tomography with the earthquake hypocenter locations and focal mechanisms some of the structures in the p wave velocity model are interpreted as active faults the eastern boundary fault zone of the graben is found to be activated in a left lateral strike slip sense the southern continuation of these faults is formed by variscan structures in the basement a change in orientation of the graben axis between the main graben and its southern end have played a role during the development of the system this difference in orientation caused the development of the dannemarie and allschwil subbasins during a late stage of the opening of the rhine graben this study shows evidence for active faulting in the basement underneath the detachment of the jura mountains these faults which are interpreted as reactivated permo carboniferous troughs coincide with the frontal thrusts of the jura mountains it might be that these structures in the basement have influence on the detachment tectonics in the region

seasonal variations in 7be activity in the sediments of cape lookout bight north carolina abstract short term sediment accumulation rates were determined using activity distributions of 7be in the surficial sediments of a station a 1 in cape lookout bight north carolina usa this semienclosed coastal marine basin is characterized by high annual accumulation rates protected from high energy conditions by its geomorphology the relatively quiescent waters of the bight s interior cause it to act as an efficient settling trap for fine grained sediment lack of bioturbation in the surface sediments allowed for variations in depth integrated activity profiles of 7be to be interpreted as short term accumulation events beryllium 7 inventories exhibited seasonal cyclicity with inaxima occurring during spring february through june the inventory of 7be ranged from 5 8 to 32 6 dpm cin 2 and was always well in excess of the atmospherically supported value x 3 8 dpm cm 2 n 15 accumulation rates calculated froin 7be activity profiles indicate that the delivery of particulate matter to the sediments of cape lookout bight is not constant throughout an annual cycle the highest monthly accumulation rates appeared to be associated with north northeast storm activity inputs were generally highest during late winter early spring when storm frequency is greatest short term accumulation rates derived from this study agree with 210pb rates calculated for a ten year period of accumulation the annual sediment accumulation rates for each of the two years over which the study was conducted was found to be 4 8 0 8 g cm 2y 1 and 3 7 1 2g cm 2y 1

beryllium 7 the cinderella of fallout radionuclide sediment tracers current concern for the sustainable management of soil resources and the many adverse effects of increased sediment loads on streams and river systems has generated a need for more information on rates and patterns of soil loss and an improved understanding of catchment sediment budgets traditional measurement techniques are frequently unable to meet the requirements and fallout radionuclides have been shown to offer considerable potential for tracing the mobilization transfer redistribution and storage of soil and sediment within catchments and river systems caesium 137 and lead 210 have been the most widely used fallout radionuclide sediment tracers but their half lives mean that the information that they provide is in most instances limited to the medium term e g 25 120 years the need for information on shorter timescales has directed attention to the potential for using beryllium 7 which has a considerable shorter half life for tracing soil and sediment redistribution over short timescales e g days weeks to date however there have been relatively few attempts to exploit this potential this situation is likely to be in part a reflection of the emphasis of early work on 137cs and 210pb and the more recent nature of work using 7be however it may also reflect the limitations and constraints imposed by the nature of 7be fallout and the short half life of this radionuclide this contribution explores recent work in using 7be as a sediment tracer and the constraints imposed by its origin and behaviour attention is directed to fallout inputs the application of 7be to tracing soil and sediment redistribution on slopes and on river floodplains its use as a source fingerprint and other related applications the likely future potential of 7be as a sediment tracer is assessed copyright 2012 john wiley sons ltd

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

continental rift development in precambrian and phanerozoic europe europrobe and the dnieper donets rift and polish trough basins abstract upper crustal structure and lower crustal and mantle character of the european continental lithosphere differ significantly from west to east the processes of rifting of phanerozoic western europe s hotter thinner crust compared with the more stable thicker 45 vs 30 km proterozoic crust of the east european craton is being investigated by europrobe case studies of western and eastern european sedimentary basins the dnieper donets basin transects the southwestern part of the east european platform in a nw se direction lying between the ukrainian shield and the voronezh massif rifting took place from early frasnian until perhaps the late visean and was accompanied by major volcanic activity the distribution of both was affected by pre existing basement fault systems the syn and post rift sedimentary succession may be as thick as 20 km in the donets trough basin evolution and the present crustal geometry have been much affected by inversion during the permian in association with uralian orogenesis tectonic events of bathonian oxfordian 168 154 ma and turonian santonian 91 84 ma age are also recorded in the basin stratigraphy the polish trough lies along the boundary between the phanerozoic and proterozoic european crustal domains coincident with the trans european suture zone the presence of this rheological boundary may be paramount in structurally controlling the position of the trough tectonic subsidence analysis indicates an initial late rotliegendes early triassic syn rift phase of development subsequently episodes of increased tectonic subsidence rate occurred during the oxfordian tithonian 157 146 ma and beginning in the cenomanian 95 90 ma the oxfordian tithonian episode is likely the signature of a second extensional event correlated with intensification of rifting within the arctic north atlantic rift system while the cenomanian and later is a precursor to mild compressional intraplate orogenic movements present day crustal structure reflects the docking of phanerozoic crust against the proterozoic during palaeozoic orogenies permo carboniferous wrenching and transtensional modifications leading to formation of the polish trough as well as modifications during the late cretaceous early tertiary inversion process

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

on the number and spacing of faults orogens and rift zones have a finite number of regional faults the accretionary prisms analysed here have a number of thrusts 50 whereas extensional areas have a number of normal faults ranging between six and 44 the average spacing of thrusts is between 5 and 25 km spacing of normal faults is more restricted into two peaks at 25 29 km and 4 6 km in which the latter is the most common the number and spacing of faults appear to be mainly controlled by the depth of the decollement plane which seems to be more variable in compressive settings with respect to rift zones basementinvolved orogens present fewer and more spaced thrusts by contrast a greater number of thrusts with shorter spacing characterize thin skinned thrust belts the shallower the decollement is the stronger it appears to control the palaeogeography in the sense of rheological lateral variations in the sedimentary cover

seismic refraction investigation of the black forest abstract within the framework of site surveys of the deep continental drilling program ktb deep seismic sounding experiments were carried out in the black forest southwest germany in august 1984 these site surveys comprised seismic refraction as well as seismic reflection measurements this paper will concentrate on the interpretation of the refraction data which were observed along a 240 km long line approximately following the morphological axis of the black forest in a n s direction and extending in the south into the swiss molasse basin from the available seismic refraction data a detailed velocity depth model of the crust and uppermost mantle was derived a clear phase refracted in the basement with a velocity of 5 9 km s is observed for all shots this phase is followed by a reflection from the upper boundary of a low velocity zone this zone is very accentuated under the northern and central black forest and is characterized by a velocity decrease from 6 2 to 5 4 km s between depths of about 8 and 14 km towards the south the velocity inversion gradually loses its intensity under the center of the southern black forest velocities of about 6 km s prevail throughout the upper crust the lower crust which starts at the lower boundary of the low velocity zone shows a very complicated response in the record sections due to long reverberations between travel times of 1 5 3 5 s reduced by 6 0 km s at an epicentral distance of approximately 30 70 km a classical phase correlation is not possible based on a combined interpretation of near angle and wide angle reflection data the lower crust is characterized by a stack of thin layers with alternating high and low velocities the average velocity of the laminated zone is 6 7 km s the reflection from the moho at a depth of 25 26 km is the most prominent phase at epicentral distances greater than 60 km

seismogram envelope inversion for the spatial distribution of high frequency energy radiation from the earthquake fault application to the 1994 far east off sanriku earthquake japan incoherency of high frequency seismic waves leads to the idea to analyze seismogram envelopes disregarding phase information for the source study we develop an inversion method for estimating high frequency above 1 hz energy radiation from the earthquake fault and site amplification factors from observed mean square s wave seismogram envelopes the inversion is executed by using the s wave envelope green function from the onset to coda for a point shear dislocation source in a scattering medium which is formulated based on an extended version of the radiative transfer theory the use of the envelope green function enables us to estimate the spatial distribution of high frequency energy radiation on a fault plane this has been difficult by conventional waveform inversion methods the rupture velocity and the duration time of energy radiation on each subfault are also estimated by grid search method we apply this new method to the 1994 far east off sanriku northeastern japan earthquake mw 7 7 which ruptured a 90 km segment of the plate boundary along the japan trench inverting observed seismogram envelopes at 10 strong motion stations in japan it is concluded that above 90 of the high frequency energy was radiated from the western half of the fault with the largest energy radiation near the deep side edge the rupture velocity is estimated to be 2 7 km s the estimated site amplification factors ranging between 0 3 and 15 are consistent with those independently estimated by the coda normalization method

accompanying seismic refraction investigations along the profile dekorp 2 north seismic refraction measurements were carried out along the dekorp 2 n reflection line traveltime data have been inverted to velocity depth distributions using x t inversion und ray tracing methods the velocity model shows alternating layers of high and low velocity high velocity values range from 6 0 to 6 6 km s in the upper crust and from 70 to 8 2 km s in the lower crust in low velocity zones velocities do not exceed 6 25 km s the crust mantle boundary lies in about 28 30 km depth correlations exist between the velocity model of refraction seismics and the line drawing section of reflection seismics

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

baikal rift zone structure and geodynamics abstract the cenozoic baikal rift zone is superimposed on the caledonian baikal fold belt representing the suture between the precambrian siberian craton and several microcontinents the baikal rift zone consists of a system of disconnected fault bounded basins and extensional and wrench faults that straddles a major arch having a topographic relief of 2 3 km rifting activity commenced during the oligocene and is still active as evident from high seismicity of the baikal rift zone across the baikal rift zone upper crustal extension is considerably smaller than would be expected from its crustal thickness which decreases by 8 11 km across the baikal basins as compared to the adjacent unextended areas the discrepancy between upper and lower crustal attenuation could be attributed to intrusion of a major diapir indeed geophysical data indicate that the sayan baikal dome coincides with such a diapir the top of which is located at the crust mantle boundary this intrusion is held responsible for oligocene and quaternary doming of the rift zone development of the intra continental baikal rift system is thought to be related to asthenospheric diapirism active rifting however intra plate stresses in conjunction with the himalayan collision may have played some role

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

imaging and monitoring of the shallow subsurface using spatially windowed surface wave analysis with a single permanent seismic source abstractdevelopment of shallow subsurface monitoring systems is important for monitoring the ground stability of shallow formation and also for conventional deep seismic monitoring because with cu

residence times of234th and7be in lake geneva the activities of two short lived natural radionuclides 234th and7be were measured in lake geneva water suspended solids and sediments in order to obtain their removal residence times in the lake four independent methods of estimation are presented and compared the calcuated residence times of234th and7be vary from 60 to 280 days and from 60 to 1100 days respectively depending on season and the method used in general 7be residence times are significantly longer than those of234th for both nuclides the removal residence times are significantly longer than their respective radioactive mean lives as a consequence the estimates based on their water column inventories are not as reliable as the estimates obtained from the measured fluxes of these nuclides into sediment traps estimates based on the bottom sediment inventories are similar in magnitude to those obtained from flux into sediment traps but occasionally are erroneous because of small scale sediment heterogeneity

southern rhine graben small wavelength tomographic study and implications for the dynamic evolution of the graben summary inversion of p wave traveltime residuals of teleseismic events recorded by a dense network of short period stations yielded a detailed image of the 3 d velocity structure of the lithosphere asthenosphere system beneath the southern rhine graben area the upper part of the lithosphere marked by velocity anomalies orientated along the graben strike can be related to the development of the graben these upper 50 km display stronger lateral heterogeneities than the weak anomalies observed at deeper levels which show roughtly an e w orientation the teleseismic inversion models yield no indications for significantly reduced seismic velocities in the upper mantle as could be expected from an actively upwelling mantle diapir located beneath the southern rhine graben area the observation of generally weak velocity variations at greater depth indicates a rather smooth transition from the lower lithosphere to the upper asthenosphere deeper parts of the lithosphere were probably altered by metasomatic processes as a consequence of the intrusion of melts during middle and late miocene times these melts cooled and solidified from the end of the miocene when rifting and thermal doming ceased in the southern rhine graben area

layered azimuthal anisotropy of rayleigh wave phase velocities in the european alpine lithosphere inferred from ambient noise abstract passive seismic imaging of the earth is a rapidly developing field of study recent advances in noise cross correlation techniques allow imaging of isotropic surface wave and shear wave velocities in areas where earthquake numbers and distributions are insufficient to implement traditional earthquake based tomography furthermore advances in the theory underpinning surface wave inversion have led to depth dependent mapping of seismic anisotropy in the lithosphere and upper asthenosphere we show that by merging these two rapidly advancing fields we can invert noise based phase velocity measurements for azimuthally anisotropic phase speed thereby providing a highly resolved image of layered azimuthal anisotropy in continental crust we apply this new algorithm in the western alps an area of complex lithospheric structure alpine crustal thickening results from continental collision indentation of the ivrea mantle into the middle crust of the european plate rollback of the european lithospheric mantle and crustal slicing we find that anisotropy beneath the central alps is stratified in two layers one with an orogen parallel fast direction above 30 km depth and another with a strong orogen perpendicular fast direction at greater depth although our resolution is reduced outside the central alps we map orogen parallel anisotropy in the crust of the northern alpine foreland we interpret the results in the central alps as first order evidence for a model of azimuthal anisotropy in which 1 near vertical emplacement of crustal slices following detachment of the lithospheric mantle from the crust gives rise to orogen parallel fast directions of wave propagation in the crust and 2 dominantly horizontal tectonics in the thickened crustal root and uppermost mantle yield orogen perpendicular fast directions at greater depth

shear wave evidence for an anisotropic lower crust beneath the black forest southwest germany abstract controlled shear wave sources a horizontal vibrator and dynamite were used in near vertical reflection studies to explore the nature of the reflective laminated lower crust in southwest germany the data reveal strong s wave reflections from the lower crust these lower crustal s reflections were not observed by previous wide angle surveys in the same region a laminated crustal model with isotropic layers and changing poisson s ratio cannot explain the differing near and far offset s response by introducing alternating anisotropic and isotropic lamellae this discrepancy may be resolved this seismic model is consistent with a petrological model of deformed amphibolites containing 10 30 of preferentially orientated hornblende observed amplitude differences in p and s wave reflections from the same depth in the lower crust suggest regions with a changing poisson s ratio

the deep crust of the southern rhine graben reflectivity and seismicity as images of dynamic processes abstract the rhine graben part of the european cenozoic rift system deserves special attention because of its location in the foreland of the alpine orogen the phanerozoic evolution of the lithosphere in this region is defined by a set of major geodynamic events ranging from the variscan orogeny late orogenic crustal re equilibration to the interference of rifting and alpine orogeny in tertiary times the rhine graben is one of the most detailedly studied continental grabens prospecting for hydrocarbons in its sedimentary fill and intensive pre site studies for the continental deep drilling program ktb on its eastern crystalline flank black forest provided a comprehensive set of geoscience data seismic investigations ranging from a deep seismic network of near vertical reflection to concurrent wide angle refraction experiments were accompanied by seismological and geological surveys therefore a direct observational comparison between the two depth definitions of crustal subdivisions elastic vs strength rheological was possible in large parts of western europe deep seismic sounding dss investigation distinguishes between a crystalline upper crust of comparatively low p wave velocities 5 9 6 0 km s with little and discrete reflectivity and a strongly reflective lower crust with higher p wave velocities about 6 4 6 8 km s both are separated by the conrad discontinuity in contrast strength and rheological considerations define a brittle upper crust and a ductile lower crust the boundary between these two realms is usually referred to as the brittle ductile transition zone which in seismically active regions is imaged by the deepest crustal hypocentres the present brittle ductile transition in the rhine graben region as defined by the deepest hypocentres does not necessarily coincide with the structural separation in an upper and lower crust as seen in deep seismic studies this suggests that the laminated lower crust developed during the crustal re equilibration phase at the end of the variscan orogeny the second part of this paper concentrates on evidence of recent tectonic activities related to rifting processes impacting on the variscan lower crust a remarkable concentration of deep crustal earthquakes reaching to the top of an asymmetrical thinned lower crust is observed at or near the eastern border fault of the southern rhine graben and is possibly induced by the young rifting process we suggest that this asymmetry could be a consequence of the uppermost mantle detaching from the upper crust in collision with the alpine orogen this allows us to propose the distinction between the influence of compression extension continental subduction and intra crustal detachment during graben formation the dynamic interference of rifting and foreland compression shown by structural and seismological observations leads to the notion of small scale collisional escape tectonics associated with an intra continental transform fault at the southern end of the rhine graben the rhine sao ne transform zone

direct determination of7be in sediments cosmic ray produced7be 53 days half life is directly measurable in freshly collected samples of river and coastal zone sediments using a lithium drifted germanium detector calibration of the detector is discussed and an assessment of overall accuracy and sensitivity presented the detection limit for a 250 g dry weight sediment sample contained in a marinelli beaker and counted for 200 minutes is approximately 0 4 pci g applications toward locating zones of rapid sedimentation as well as in understanding shallow water sedimentation dynamics are suggested

dynamic processes controlling evolution of rifted basins abstract the extension of the lithosphere controlling the development of rifted basins is driven by a combination of plate boundary forces frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system although mantle plumes are not a primary driving force of rifting they play an important secondary role by weakening the lithosphere and by controlling the level of rift related volcanic activity a distinction between active and passive rifting is only conditionally justified the extension of the lithosphere depending on its rate and magnitude and the potential temperature of the asthenosphere can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere in rift systems the level and timing of volcanic activity is highly variable the lack of volcanic activity implies passive rifting an initial passive rifting stage can be followed by a more active one during which magmatism plays an increasingly important role magmatic destabilization of the moho may account for the frequently observed discrepancy between upper and lower crustal extension factors combined with evidence for thermal thinning of the mantle lithosphere this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models the structural style of rifts is controlled by the rheological structure of the lithosphere the availability of crustal discontinuities that can be tensionally reactivated the mode orthogonal or oblique and amount of extension and the lithological composition of pre and syn rift sediments simple shear extension prevails in rifts that subparallel the structural grain of the basement pure shear extension is typical for rifts cross cutting the basement grain pre existing crustal and mantle lithospheric discontinuities contribute to the localization of rift systems the duration of the rifting stage of extensional basins is highly variable stress field changes can cause abrupt termination of rifting in major rift systems progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts depending on constraints on lateral block movements crustal separation can be achieved after as little as 9 my and as much as 280 my of rifting activity syn rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere its magmatic inflation and thermal attenuation of the mantle lithosphere post rift basin subsidence is governed by thermal reequilibration of the lithosphere asthenosphere system deep seated thermal anomalies related to syn rift pull up of the asthenosphere lithosphere boundary have decayed after 60 my by about 65 and after 180 my by about 95 the magnitude of post rift subsidence is a function of the rift induced thermal anomaly and crustal density changes the potential temperature of the asthenosphere and initial water depths intraplate stresses can have an overprinting effect on post rift subsidence stretching factors derived from post rift subsidence analyses must be corrected for such effects

crustal structure of the rhenish massif results of deep seismic reflection lines dekorp 2 north and 2 north q the reflection seismic line dekorp 2 n reveals an almost complete cross section through the rhenohercynian zone the most external part of the variscan orogen in europe

development of asymmetric basins along continental transform faults abstract many basins associated with wrench or transform faults are asymmetrical both longitudinally and laterally the sense of basin asymmetry changes along the strike of transform faults geophysical data from the dead sea rift and other transforms indicate that wrench induced asymmetric basins are bounded on only one side by a transform fault this implies that during the evolution of such basins maximum compression was parallel to the transform the direction of extension can change during the geologic evolution of a basin a possible explanation of this observation takes the strength of the fault into into consideration in the case of a weak fault in a strong crust the horizontal principal stresses would probably rotate to orientations parallel and perpendicular to the fault thus minimizing the shear stress on the main fault basins formed by regional extension such as in the east african rift system sometimes show similar features recent studies have shown that these basins often undergo oblique extension this suggests that the asymmetry in these basins may result from simultaneous strike slip motion and fault normal extension similar to the way asymmetry is produced in large transform basins periods of oblique extension can alternate with periods of orthogonal extension the asymmetry formed during periods of oblique extension is often preserved in the stratigraphic record

reflectivity patterns in the variscan mountain belts and adjacent areas an attempt for a pattern recognition and correlation to tectonic units abstract the seismic reflection profiles of dekorp deutsches kontinentales reflexionsseismisches programm in the federal republic of germany to date have been limited to areas of the variscan orogeny nevertheless the character of their reflections differs considerably and may be correlated to certain variscan and post variscan developments lower crust lamellae develop in areas of high heat flow mostly associated with post variscan extensional processes crocodile and nappe tectonics are best preserved in the cores and at the flanks of older massifs which were incorporated into the variscan orogeny so far poor reflectivity has been observed only in the area of the london brabant massif which was not involved in any of the phanerozoic orogenies

lithospheric structure along wide angle seismic profile georift 2013 in pripyat dnieper donets basin belarus and ukraine