identifying global seismic anisotropy patterns by correlating shear wave splitting and surface wave data we compare a global compilation of shear wave splitting measurements with azimuthal seismic anisotropy parameters inferred from surface wave tomography the currently available splitting dataset is taken from a novel comprehensive collection of available publications that is updated interactively online the comparison between the two types of data is made by calculating predicted splitting parameters from the anisotropic tomography model comparing these predicted splitting parameters with the observed ones we find a considerable correlation between the two datasets at global scale this result is noteworthy since such correlation did not seem to exist in previous studies the spatial resolution associated with the two types of methods is rather different while surface waves have good vertical resolution and poor lateral resolution of several hundreds of kilometers sks splitting measurements have good lateral but poor vertical resolution the correlation can be understood in light of recent propositions that anisotropy seen by sks splitting constrains mostly the upper mantle and therefore a similar depth region as surface waves the correlation also confirms the generally good quality of the shear wave measurements as well as that of the anisotropic tomography model

sn propagation in the western united states from common midpoint stacks of usarray data 1 the regional seismic phase sn propagates horizontally in the uppermost mantle and is sensitive to lateral variations in mantle lid thickness temperature and melt sn is therefore often used as an indicator for physical properties of the lithosphere it has previously been noticed that sn is not observed at many stations in the western united states and sn seems especially highly attenuated for paths across the basin and range here we apply stacking methods to usarray data to identify highly attenuating regions in the uppermost mantle and increase the spatial resolution of the sn propagation image we find evidence for sn propagation at short ranges in the central great basin and the northeastern part of the colorado plateau both regions where lithospheric stability and thickness is debated and observe strong sn attenuation around the perimeter of the central great basin

three dimensional p and s velocity structure in the coalinga region california the coalinga earthquake sequence of 1983 provided a unique opportunity to perform a three dimensional velocity and hypocenter inversion in an area of complex three dimensional structure dominated by folding and blind thrusts additionally since other varied geological and geophysical studies have been completed in this area the three dimensional inversion solution could be compared to other interpretations inversion of 7696 p and 1511 s first arrivals from earthquakes and 696 p first arrivals from refraction shots produced a three dimensional velocity model with grid spacing of 1 2 km in the hypocentral area the overall shape and location of velocity features correspond well to the mapped surface geology the three dimensional inversion yields details of folds where the resolution is good and the general shape where resolution is lower the amounts of structural relief inferred for the local folds are similar to values inferred from geologic data the three dimensional velocity solution has several distinctive features there is a linear high velocity body 6 1 6 5 km s about 25 km long from 6 to 8 km depth that may represent a fragment of coast range ophiolite a shallow low velocity zone lvz which extends for 20 km along the fold axis at about 6 km depth and correlates with lvzs observed in both the refraction and the reflection data may indicate high pore pressure caused by lateral compressive strain deeper lvzs occur within inferred franciscan material and are characterized by horizontal or southwest dipping zones of varied thickness 4 8 km wide and 5 10 km long these lvzs may represent multiple thrust faults their locations and geometry are consistent with thrust faults inferred with seismic reflection data the three dimensional velocity solution compares well to prior two dimensional seismic reflection and refraction models and observed gravity the shape of the inferred sedimentary section agrees well with the reflections from the cenozoic strata compared to the refraction model the three dimensional solution has similar velocities and similar locations of velocity features but is more detailed in the hypocentral zone where it uses more data the gravity computed from the three dimensional velocities is similar to the observed gravity in both shape and amplitude both a simple one dimensional initial model and a complex initial model derived from the refraction interpretation were tried a simple starting model gave the best results the s velocity solution has different resolution than the p velocity solution because it uses a different set of stations and it has lower resolution because it uses fewer arrival times while the general patterns of velocity variation are similar for both vp and vs the vs solution tends to have more smearing of velocity features and can have somewhat different locations of velocity features

mantle dynamics beneath the gibraltar arc western mediterranean from shear wave splitting measurements on a dense seismic array 1 controversial evolutionary models have been proposed for the gibraltar arc system a complex interaction zone between the eurasia and african plates here we derive new mantle anisotropic constraints from sks splitting measurements on a dense network of about 90 broad band stations deployed over south iberia and north morocco the inferred fast polarization directions fpd clearly show a spectacular rotation along the arc following the curvature of the rif betic chain while stations located at the south and south east edges show distinct patterns these results support geodynamical processes invoking a fast retreating slab rather than convective removal and delamination models the fpd variations along the gibraltar arc can be explained by fossil anisotropy acquired during the western mediterranean eocene subduction while changes to the south and south east of the rif betic chain could be the imprint of a flow episode around an alboran high velocity slab during its miocene fragmentation from the algerian slab

seismic anisotropy and velocity structure beneath the southern half of the iberian peninsula travel times of 11 612 pn arrivals collected from 7675 earthquakes are inverted to image the uppermost mantle velocity and anisotropy structure beneath the southern half of the iberian peninsula and surrounding regions pn phases are routinely identified and picked for epicentral distances from 200 to 1200 km the method used in this study allows simultaneous imaging of variations of pn velocity and anisotropy the results show an average uppermost mantle velocity beneath the study area of 8 0 km s the peninsular area covered by the iberian massif is characterized by high pn velocity as expected in tectonically stable regions indicating areas of the hercynian belt that have not recently been reactivated the margins of the iberian peninsula have undergone a great number of recent tectonic events and are characterized by a pronouncedly low pn velocity as is common in areas greatly affected by recent tectonic and magmatic activity our model indicates that the betic crustal root might be underlined by a negative anomaly beneath the southeastern iberian peninsula in the atlantic ocean we find a sharp variation in the uppermost mantle velocities that coincides with the structural complexity of the european and african plate boundary in the gulf of cadiz our results show a very pronounced low velocity anomaly offshore from cape san vicente whereas high velocities are distributed along the coast in the gulf of cadiz in the alboran sea and northern morocco the direction of the fastest pn velocity found is almost parallel to the africa eurasia plate convergence vector northwest southeast whereas to the north this direction is almost parallel to the main trend of the betic cordillera i e east west in its central part and north south in the curvature of the arc of gibraltar this suggests that a significant portion of the uppermost mantle has been involved in the orogenic deformation that produced the arcuate structure of the betic cordillera however we assume that the neogene extension had no major influence on a lithospheric scale in the alboran sea our results also show a quite complex pattern of anisotropy in the southwest iberian lithospheric mantle since the relationship between the direction of fastest pn velocity and major hercynian tectonic trends cannot be directly established 2004 elsevier b v all rights reserved

seismic anisotropy from the variscan core of iberia to the western african craton new constrains on upper mantle flow at regional scales abstract the regional mantle flow beneath the westernmost mediterranean basin and its transition to the atlantic domain is addressed by inspecting the anisotropic properties of the mantle more than 100 new sites from the variscan core of iberia to the northern rim of the western african craton are now investigated using the data provided by different temporary and permanent broad band seismic arrays our main objective is to provide a larger regional framework to the results recently presented along the gibraltar arc in order to check the validity of the different geodynamic interpretations proposed so far the significant variations in the retrieved anisotropic parameters suggest that different processes must be invoked to explain the origin of the observed anisotropy beneath the variscan units of the central iberian massif the new results show a moderate amount of anisotropy with fast polarization directions fpd oriented close to e w those results can only be explained in terms of global mantle flow if models accounting for contributions from surface plate motion net lithosphere rotation and density variations are taken into consideration one of the major results presented is the significant number of good quality data without evidence of anisotropy nulls observed beneath permanent stations in southern portugal those nulls can be explained by the presence of a predominantly vertical mantle flow associated to large variations in the lithospheric thickness beneath the gibraltar arc the fpd show a spectacular rotation evidenced by the results presented by diaz et al 2010 and miller et al 2013 those results are reviewed here taking also into consideration the geodynamic modeling presented recently by alpert et al 2013 and other geophysical and geodetic results further south the analysis of new broad band stations installed in the moroccan meseta and the high atlas show a small degree on anisotropy and a large number of null events pointing again to the presence of vertical flow in the mantle the results favor an asthenospheric origin related to present day mantle flow for the anisotropy observed from the variscan core of iberia to the northern rim of the west african craton this flow is deflected around the high velocity slab beneath the gibraltar arc and seems affected locally by vertical flow associated to edge driven convective cells the presence of significant backazimuthal variations in the anisotropic parameters retrieved from single events suggests that a second order contribution from an anisotropic layer within the lithosphere may also exist

delay times and shear wave splitting in the mediterranean region summary we measure sks splitting parameters and p and s delay times in the mediterranean region using broad band recordings from the temporary midsea array and permanent networks the midsea seismic array has substantially improved data coverage along the european mediterranean margins and in northern africa shear wave splitting is observed for 95 per cent of the stations with splitting times up to 2 s we propose five anisotropic domains based on the characteristics of the observations in the western part of the region we observe an alignment with plate motion suggesting an asthenospheric origin for anisotropy in the central and near eastern part the fast directions are less coherent laterally and influenced by extension and subduction processes along the dead sea fault the fast directions are parallel to the relative motion between arabia and africa which we attribute in part to coherent vertical deformation our measurements of teleseismic relative p and s wave delay times within the mediterranean region reach peak to peak values of 2 5 and 8 s respectively consistent with international seismological centre isc delay times we observe the earliest arrivals along the hellenic subduction zone and some of the latest along the dead sea fault we find that s wave delays are roughly three times as large as those of p waves from a slight frequency dependence of our cross correlation based delay time measurements we estimate mediterranean lateral heterogeneity to have a dominant size of one or more hundred kilometres we further determine that the anisotropy implied by our sks splitting measurements does not significantly bias the pattern of teleseismic delay times

crustal structure beneath the rif cordillera north morocco from the rifsis wide angle reflection seismic experiment the different geodynamic models proposed since the late 1990s to account for the complex evolution of the gibraltar arc system lack definite constraints on the crustal structure of the rif orogen here we present the first well resolved p wave velocity crustal models of the rif cordillera and its southern continuation toward the atlas made using controlled source seismic data two 300 km long wide angle reflection profiles crossed the rif along ns and ew trends the profiles recorded simultaneously five land explosions of 1tn each using 850 high frequency seismometers the crustal structure revealed from 2 d forward modeling delineates a complex laterally varying crustal structure below the rif domains the most surprising feature seen on both profiles is a 50 km deep crustal root localized beneath the external rif to the east the crust thins rapidly by 20 km across the nekkor fault indicating that the fault is a crustal scale feature on the ns profile the crust thins more gradually to 40 km thickness beneath middle atlas and 42 km beneath the betics these new seismic results are in overall agreement with regional trends of bouguer gravity and are consistent with recent receiver function estimates of crustal thickness the complex crustal structure of the rif orogen in the gibraltar arc is a consequence of the miocene collision between the iberian and african plates both the abrupt change in crustal thickness at the nekkor fault and the unexpectedly deep rif crustal root can be attributed to interaction of the subducting alboran slab with the north african passive margin at late oligocene early miocene times

3 d pn tomography reveals continental subduction at the boundaries of the adriatic microplate in the absence of a precursor oceanic slab abstract slab pull generated by subducting oceanic lithosphere is generally considered as a major trigger for the onset of continental subduction however this may be in conflict with the occurrence of uhp terranes bearing no evidence of oceanic lithospheric rocks involved in the exhumation cycle here we image the uppermost mantle p velocity structure beneath the central mediterranean suggesting the possibility that the initiation of continental subduction may not require a precursor oceanic slab we combine i a three step inverted 3 d pn tomography model of the adriatic microplate with ii available geologic constraints and palinspastic reconstructions of the africa eurasia plate boundary zone our pn tomography model reveals elongated regions with vp

opposite subduction polarity in adjacent plate segments the work of m p m f and j v is part of the projects alpimed pie csic 201530e082 and mite cgl2014 59516 p and partly financed by the generalitat de catalunya 2014 sgr 1471 and 2017 sgr 847 the work of s z is funded by the spanish ministry of economy and competitiveness through grant cicyt dpi2017 85139 c2 2 r and generalitat de catalunya 2017 sgr 1278

pn tomography with moho depth correction from eastern europe to western china we proposed a modified pn velocity and anisotropy tomography method by considering the moho depth variations using the crust 1 0 model and obtained high resolution images of the uppermost mantle pn velocity and anisotropy structure from eastern europe to western china the tomography results indicate that the average pn velocities are approximately 8 0 and 8 1 km s under the western and eastern parts of the study area respectively with maximum velocity perturbations of 3 4 we observed high pn velocities under the adriatic sea black sea caspian sea arabian plate indian plate and in the tarim and sichuan basins but low pn velocities under the apennine peninsula dead sea fault zone anatolia caucasus iranian plateau hindu kush and in the yunnan and myanmar regions generally regions with stable structures and low lithospheric temperatures exhibit high pn velocities low pn velocities provide evidence for the upwelling of hot material which is associated with plate subduction and continental collision processes our pn velocity and anisotropy imaging results indicate that the adriatic microplate dives to the east and west the hot material upwelling caused by subduction beneath the tibetan plateau is not as significant as that in the caucasus and myanmar regions the lithosphere exhibits coupled rotational movement around the eastern himalayan syntaxes and the areas to the north and south of 26 n in the yunnan region are affected by different geodynamic processes our newly captured images of the uppermost mantle velocity and anisotropy structure provide further information about continental collision processes and associated dynamic mechanisms

geodynamic control on orogenic and anorogenic magmatic phases in sardinia and southern spain inferences for the cenozoic evolution of the western mediterranean abstract the genetic relationships between orogenic i e subduction related and anorogenic i e intra plate cenozoic igneous phases have been investigated in two regions of the western mediterranean area sardinia and southern spain in sardinia the orogenic magmatism 38 12 ma is followed by the anorogenic volcanism mostly since about 6 ma whereas in southern spain the anorogenic volcanism follows the orogenic phase 34 6 ma after a gap of 0 4 ma in the betic calatrava districts the older orogenic magmatism tholeiitic calcalkaline and more potassic products of both areas is related to the subduction of the ionian oceanic lithosphere which developed beneath the paleo european iberian continental margin probably since middle late eocene this subduction system migrated southeastwards with time up to its present position in the eolian calabrian arc and the betic alboran regions along the apennine maghrebide belt relics of subducted lithosphere are geophysically recorded as nearly vertical bodies down to 500 600 km flattening for several hundreds of kilometres under the tyrrhenian sardinia and betic calatrava areas respectively these relics of subducted slabs which pond over large areas of the mantle transition zone appear to play a significant role also in the genesis of the younger anorogenic magmas whose major volcanic fields lie above the frontal part of the subducted slab where convective instabilities and upward mantle flow components are geophysically supported by laboratory and 3d numerical models this dynamic response to subduction involving localised mantle upwellings and remobilization of pre existing mantle components may have been a fundamental factor in the generation of anorogenic magmas due to slab roll back and inter arc extension in both eolian tyrrhenian and betic alboran regions the magma sources of the previous orogenic phases can be completely replaced by fresh mantle diapirs from whic h anorogenic magmas will be generated these magmas are invariably characterised by oib isotopic signatures himu and emi which are classically interpreted as long term recycling of oceanic crust plus variable sedimentary components via ancient pre paleozoic subduction events we propose that the recent cenozoic subduction from which the orogenic series was generated also had a dynamic influence on the younger anorogenic magmatism by remobilization of long term isolated mantle components which resulted in the secular evolution of oib type magmas in this view the on going subduction processes of the mediterranean orogenic belts did not provide chemical ingredients to the mantle sources of the anorogenic magmas but induced reactivation of older metasomatised mantle domains ultimately triggering magma genesis

moho topography beneath the iberian western mediterranean region mapped from controlled source and natural seismicity surveys abstract the complex tectonic interaction processes between the european and african plates at the western mediterranean have left marked imprints in the crustal architecture of this area particularly concerning the lateral variations in crustal thicknesses the detailed mapping of such variations is hence of large interest as it provides a major constraint to geophysical and geodynamic modeling at different scales controlled source seismic profiling and receiver functions from natural seismicity are widely considered as major tools to constrain moho topography we compile here the moho depths determined from a comprehensive number of both types of seismic surveys to end up with a new 3d moho depth map of the iberian peninsula its continental margins and north morocco since the 1970s the lithospheric structure beneath this study area has been extensively investigated using multichannel normal incidence seismic reflection and refraction wide angle reflection profiling in the last few years some high resolution surveys at sea and inland have been acquired the latter ones involving 1000 land stations on the other hand the topoiberia iberarray experiment has triggered the investigations on crustal and lithospheric structure using natural seismicity providing a homogeneous spatial resolution never achieved before the availability of good quality results from both methodologies in a common area provides an excellent opportunity to check the consistency of the moho depth estimations the integration of both datasets has resulted in a new high resolution map of the crustal thickness variations the final grid evidences large moho topography variations including crustal imbrication in the pyrenean range a large and relatively undisturbed variscan massif in the center of iberia and a probable delamination process beneath the gibraltar arc the crustal thicknesses vary from 15 km in continental margins up to values exceeding 50 km beneath the pyrenees or the rif cordillera

pn velocities beneath continental collision zones the turkish iranian plateau summary tomographic imaging of the uppermost mantle velocity in the middle east shows normal pn velocities 8 0 8 2 kms beneath the black sea and the southern caspian sea in contrast low pn velocities 7 9 km s i are found beneath the aegean sea and much of the turkish iranian plateau a region of exceptionally low pn velocities c7 6 km s beneath the lesser caucasus mountains and along the turkish iranian border coincides with a region of high sn attenuation and extensive neogene volcanism all these features suggest that near solidus conditions exist within the uppermost mantle beneath the turkish iranian plateau such conditions may result either from the decompression melting associated with upwelling convection cells or by the infiltration of water released from subducted lithosphere into the mantle above the presence of a partially melted uppermost mantle weakens the lithosphere beneath the turkish iranian plateau thus allowing it to become the locus of deformation in the arabian eurasian collision zone

constraints on the tectonic evolution of the westernmost mediterranean and northwestern africa from shear wave splitting analysis abstract the westernmost mediterranean mantle and lithosphere have evolved into their current configuration due to complex interactions between the african and eurasian plates to help unravel the regional tectonics we use new broadband seismic data across the gibraltar arc and into southern morocco to infer azimuthal seismic anisotropy and flow patterns for the upper mantle based on shear wave splitting analysis a deep 600 km earthquake in april 2010 was recorded by the array and allowed us to compare 31 direct s measurements with 235 teleseismic sk k s events from 3 years of deployment the patterns of apparent fast polarization orientations and delay times suggest three major tectonic domains when interpreted jointly with recent tomographic images of the subducted slab 1 a subducted slab related toroidal flow domain centered upon the alboran sea and southern spain leading to complex splits 2 a region where the west african craton deflects mantle flow in the anti atlas and high plateaux and 3 an intermediate domain across the central high atlas across the axis of the mountain belt a coherent regional maximum of delay times is observed for both s and sks splitting measurements with polarizations predominantly parallel to the strike we interpret this as possible sw ne channeling of mantle flow beneath the region with a thinned lithosphere and slow seismic velocities beneath the central high atlas mountains

compressional velocity structure and anisotropy in the uppermost mantle beneath italy and surrounding regions travel times of about 39 000 pn arrivals recorded from regional earthquakes by the italian telemetered seismic network and by stations of nearby countries are inverted to image lateral variations of seismic velocity and anisotropy at subcrustal depth in italy and surrounding regions this method allows simultaneous imaging of variations of pn velocity and anisotropy as well as crustal thickness variations the po plain the adriatic sea and the ionian sea have normal to high pn velocities in contrast lower velocities 7 9 8 0 kin s are imaged in italy beneath the western alps the northern apennines and eastern sicily and nearby calabria as well as in northern albania and beneath the pannonian basin low pn velocities beneath the northern apennines correlate with present day extension and may have resulted from thermal anomalies in the uppermost mantle possibly due to delamination processes low velocities are consistent with the high attenuation zone inferred in the uppermost mantle beneath the internal apennine units and the tyrrhenian margin of the peninsula by mele et al 1996 1997 on the contrary low velocities beneath the western alps may be an apparent effect due to the abrupt thickening of the crustal roots pn velocity is anisotropic in the study area with a maximum amplitude of 0 2 km s the largest anisotropic velocity anomalies are observed along the major arc structures of italy i e the northern apennines and the calabrian arc indicating that these features are controlled by uppermost mantle processes the anisotropy anomaly along the calabrian arc extends as far as albania but ends abruptly north of this area suggesting that a lithospheric discontinuity is present along the northern albanian border

crust and mantle lithospheric structure of the iberian peninsula deduced from potential field modeling and thermal analysis abstract we investigate the lithospheric structure of the iberian peninsula and lateral crustal density variations using a three step approach first the crustal and mantle lithosphere thicknesses are calculated from joint geoid and elevation modeling combined with thermal analysis further constrained by seismic data we then compute the 3d gravity effect of the resulting lithospheric structure to separate the measured bouguer anomaly into its regional and local components finally we invert the residual gravity anomalies to highlight lateral average crustal density variations and discuss them in terms of crustal structures our results show that for the majority of the study area the crustal thickness does correlate with the regional topography pattern the highest topography above 1500 m shows thicknesses above 44 km with local values up to 48 km crustal thicknesses in the range of 36 40 km are obtained in the uplifted alpine areas while a thinner crust is observed in sedimentary basins and in the iberian massif 30 to 35 km with the exception of sw iberia region where the crust thins from 30 to 28 km thick lithosphere above 140 km is found along the pyrenees the cantabrian mountains the iberian chain and in the betics while the thinnest lithosphere is found in sw iberia 90 km 3d inversion of residual anomalies show that for the majority of the area the average density of the crust is in the range of 2810 10 kg m 3 the denser crust is found in the nw and sw regions of the iberian massif 30 kg m 3 on average and locally in the pyrenees above 70 kg m 3 nw of the iberian chain 15 kg m 3 on average and in the southern internal betics 70 kg m 3 the least dense crust is found in the central and western betic chain 30 kg m 3 on average and in sedimentary basin depocenters

corundum inclusions in diamonds discriminatory criteria and a corundum compositional dataset abstract mineral inclusions of corundum are reported from diamonds from alluvial deposits of tributaries of the rio aripuana juina brazil we present the first recorded occurrence of sapphire as an inclusion in diamond and expand on the database of ruby and white corundum inclusions ruby inclusions are found to occur both as isolated and touching grains with aluminous pyroxene and associated with ferropericlase mineral chemistry and phase relations place the origin of such ruby bearing diamonds within the lower mantle at 770 km mineral associations indaving other corundum inclusions were not observed hence their depth of origin is less certain compositions of corundum samples were characterised by electron and ion microprobe given the scarcity of literature data corundum samples from a variety of other geological settings were also analysed samples comprised corundums associated with granitic emplacement metasomatism amphibolite facies and granulite facies rocks gem and industrial synthetic origins and carmine coloured corundums recovered from kimberlite drill cores in addition to variable amounts of cr fe ti mg and si measurable quantities of other transition elements and high field strength elements were also detected corundums from similar geological settings show very similar compositions and are easily distinguishable from other settings irrespective of locality rubies from norwegian tanzanian and kenyan amphibolite facies rocks are compositionally indistinguishable additionally corundums from metasomatised zones associated with contact metamorphism from arizona and japan were very similar particularly characterised by unusually high abundance of mobile zr and nb tens of ppm all juina inclusions are particularly distinguishable from other corundums by high concentrations of ni 18 171 ppm weight typically at least an order of magnitude enriched over the same corundum varietal types from elsewhere furthermore the sapphire inclusion exhibited much larger ratios of ga and ge to hfse elements compared to otherwise similar samples and ruby inclusions are distinguished by high mg fe ratios 0 27 1 56 by weight compositional differences between inclusions in diamonds and corundums from other settings in addition to corundum s physical and chemical durability suggest that with the employment of rapid identification tools such as energy dispersive spectrometry eds and laser icpms corundum has promise as an indicator of diamond prospectivity

automated analysis of sks splitting to infer upper mantle anisotropy beneath germany using more than 20 yr of grsn and grf data

anisotropy and vp vs in the uppermost mantle beneath the western united states from joint analysis of pn and sn phases pn and sn phases are valuable for resolving velocity structure in the mantle lid as they propagate horizontally right below the moho relatively few sn tomography attempts have been made compared to pn because sn is often highly attenuated or buried in p wave coda usarray has greatly increased data coverage for regional phases and both pn and sn are routinely picked by network analysts here we jointly invert pn and sn arrival time residuals with a modified time term analysis and a regularized tomography method and present new maps of crustal thickness uppermost mantle p velocity perturbations vp vs ratios and azimuthal anisotropy strength and orientation beneath the western united states the results indicate partially molten mantle below the snake river plain and the colorado plateau the seismic structure of the top 40 km of the mantle below the colorado plateau differs from that seen at greater depths in other studies such as surface wave or teleseismic body wave tomography whereas the snake river plain anomaly just below the moho is comparable to structures seen at about 200 km depth pn fast axes provide complementary information to sks shear wave splitting observations and our analysis indicates that in several regions in the western united states the orientation of azimuthal anisotropy changes with depth in the upper mantle however we have so far been unable to resolve shear wave splitting directly in sn waveforms which seem to be dominated by sn sv energy

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

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

shear wave anisotropy beneath the aegean inferred from sks splitting observations 1 sks splitting parameters are measured in the aegean region using events recorded at a dense temporary network in the south aegean and the operating permanent networks especially focusing in the back arc and the near trench areas of the hellenic arc in general fast anisotropy directions are trench perpendicular in the back arc area and trench parallel near the trench anisotropy measurements near the volcanic arc mark the transition between these two regions in the back arc a gradual increase is observed in delay times from south to north with a prevailing ne sw direction in cyclades this pattern is correlated with gps velocities and stretching lineations of metamorphic core complexes our preferred source of anisotropy in the back arc region is the mantle wedge flow induced by the retreating descending slab the westernmost termination of the trench reveals directions parallel with the kefalonia transform fault and perpendicular to the convergence boundary beneath peloponnese the trench parallel flow is probably located beneath the shallow dipping slab although scattered measurements may also reflect fossil anisotropy from a past nw se strike of the trench in western crete which may be entering a stage of continental collision the anisotropy pattern changes to trench perpendicular with a possible subslab source good nulls in central east crete indicate a change in the anisotropy origin toward the east at the easternmost side of the trench fast directions are trench parallel this reflects a similar subslab flow that may become toroidal around the slab edge beneath western turkey this may also produce a trench parallel flow within the mantle wedge

hydroxyl contents of accessory minerals in mantle eclogites and related rocks infrared spectra in the region 3000 to 3800 cm 1 have been measured on coesite kyanite sanidine and rutile occurring in inclusions of eclogite and on garnet and spinel in an inclusion of alkremite from south african kimberites coesite and sanidine contain virtually no h 2o or oh although one sanidine crystal was observed to contain abundant h2o apparently as fluid inclusions of molecular h2o kyanite contains significant oh consistent with previous results for similar samples corundum gives no indication of the presence of h 2o or oh rutile containing significant amounts of fe cr al and nb also contains significant amounts of structural oh garnet in alkremite contains small amounts of molecular h 2o whereas the spinel coexisting with this garnet gives no indication of h 2o or oh indicating that the spinel structure is not able to accommodate significant amounts of oh ammonium contents of all samples were less than the detection limit about 10 ppm

a 3d vs model of the upper mantle beneath italy insight on the geodynamics of central mediterranean abstract we compute a high resolution vs model of the upper mantle underneath italy by inverting relative residuals of s wave arrivals from teleseisms recorded at the italian broad band national seismic network we also present a model of vp vs perturbations obtained from similarly resolved p and s wave velocity models the joint analyses of vs and vp vs models suggests that compositional variations concur with temperature variations to generate the observed velocity patterns giving deeper insight into the upper mantle structure the investigation of coherent high vs and high vp anomalies permits a comprehensive picture of the main oceanic domains involved in the puzzling subduction system of the central mediterranean slab windows and tears developed in the ionian slab are highlighted by regions of low vp low vs and high vp vs anomalies the adria continental lithosphere is characterized by high vp high vs and low vp vs anomalies that trace the sinking of eclogitized material underneath the apennines and the eastern alps chains the overall tomographic results yield the development of a new conceptual model for the alps and apennines formation in which three basic processes occurred in different time and different locations all around the alpine apennines system continental collision slab break off and delamination of the upper plate lithosphere

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

initiation of an active margin at the north iberian continent ocean transition 1 the north iberian or cantabrian margin located at the southern flank of the bay of biscay underwent successive tectonic regimes of rifting passive margin and compression from mesozoic to tertiary times a complete crustal cross section of the north iberian margin from the abyssal plain to the shoreline and a reconstruction of its undeformed upper cretaceous structure are presented here it is constrained after the compilation and interpretation of different geophysical data sets recently available in the area the reflective pattern is provided by deep seismic reflection profile escin 4 complemented by commercial profiles and well information from the north iberian platform and the velocity depth control comes from an onshore offshore wide angle seismic profile tested also with gravity modeling the detailed cross section of the meso tertiary basins that fill the platform and abyssal plain shows structures from the three main tectonic events 1 normal faults and asymmetric basins from the permian to lower cretaceous extensional stage 2 upper cretaceous sediments deposited under stable conditions during the passive margin period and 3 inverted faults thrusts and folds related to the tertiary compression the deep structure of the crust beneath the margin is poorly constrained from escin 4 profile that shows reflectivity in the lower crust only at a small area under the platform however the corresponding wide angle experiment provides a conspicuous image of the moho that shows a continued deepening toward the continent on the basis of the geophysical results we propose a new model for this margin where the lower crust is detached and underthrusted to the south as a result of the partial closure of the bay of biscay an interpreted mesozoic crustal scale extensional detachment could be the weakness zone that allowed the lower crust to slide southward under the upper crust resulting in the indentation of the cantabrian margin lower crust into the iberian crust plate convergence stopped at an early stage making this a unique area to study the initial stages of deformation of a passive margin

uppermost mantle seismic velocity and anisotropy in the euro mediterranean region from pn and sn tomography summary in the last 10 15years the number of high quality seismic stations monitoring the euromediterranean region has increased significantly allowing a corresponding improvement in structural constraints we present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath this complex area compiled from inversion of pn and sn phases sampling the whole region the method of hearn has been applied to the traveltime arrivals of the international seismological center catalogue for the time period 1990 2010 a total of 579 753 pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220km and 1400km have been retained after applyingstandardqualitycriteria maximumdepth minimumnumberofrecordings maximum residual values our results show significant features well correlated with surface geology and evidence the heterogeneous character of the euro mediterranean lithosphere the station terms reflect the existence of marked variations in crustal thickness consistent with available moho depths inferred from active seismic experiments the highestpnvelocities are observed along a continuous band from the po basin to the northern ionian sea other high velocity zones include the ligurian basin the valencia trough the southern alboran sea and central part of the algerian margin most significant low velocity values are associated to orogenic belts betics pyrenees alps apennines and calabrian arc dinarides hellenides and lowvelocityzonesarealsoidentifiedbeneathsardiniaandthebalearicislands theintroductionof an anisotropic term enhances significantly the lateral continuity of the anomalies in particular in the most active tectonic areas pn anisotropy shows consistent orientations subparallel to major orogenic structures such as betics apennines calabrian arc and alps the sn tomographic image has lower resolution but confirms independently most of the features evidenced in the pn tomography

sks splitting in southern italy anisotropy variations in a fragmented subduction zone abstract in this paper we present a collection of good quality shear wave splitting measurements in southern italy in addition to a large amount of previous splitting measurements we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the cat scan temporary network these new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the apulian platform for our analysis we have selected well recorded sks phases and we have used the method of silver and chan to obtain the splitting parameters the azimuth of the fast polarized shear wave and delay time t shear wave splitting results reveal the presence of a strong seismic anisotropy in the subduction system below the region three different geological and geodynamic regions are characterized by different anisotropic parameters the calabrian arc domain has fast directions oriented nne ssw and the southern apennines domain has fast directions oriented nnw sse this rotation of fast axes following the arcuate shape of the slab is marked by a lack of resolved measurements which occurs at the transition zone between those two domains the third domain is identified in the apulian platform here fast directions are oriented almost n s in the northern part and nne ssw to ene wsw in the southern one the large number of splitting parameters evaluated for events coming from different back azimuth allows us to hypothesize the presence of a depth dependent anisotropic structure which should be more complicated than a simple 2 layer model below the southern apennines and the calabrian arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer at least at the edge of southern apennines and apulian platform we interpret the variability in fast directions as related to the fragmented subduction system in the mantle of this region the trench parallel observed in calabrian arc and in southern apennines has its main source in the asthenospheric flow below the slab likely due to the pressure induced by the retrograde motion of the slab itself the pattern of in the apulian platform does not appear to be the direct result of the rollback motion of the slab whose influence is limited to about 100 km from the slab the anisotropy in the apulian platform may be related to an asthenospheric flow deflected by the complicated structure of the adriatic microplate or may also be explained as frozen in lithospheric anisotropy

tomographic pn and sn velocity beneath the continental collision zone from alps to himalaya 1 we have obtained vp and vs velocity images of the uppermost mantle beneath the continental collision zone from the alps to the himalaya by performing tomographic inversion using both pn and sn travel times 654 999 pn arrivals and 121 838 sn arrivals were selected from the joint database including isc ehb iran bulletin and the annual bulletin of chinese earthquakes average pn and sn velocities are 8 04 km s and 4 60 km s respectively and maximum velocity perturbations are about 6 pn velocity correlates well with topography in general mountains with high elevations show low velocity while the seas basins and plains with low elevations show high velocity because the mountains are collision zones with strong tectonic activity and the low elevation areas are stable plates the large tectonic lines are boundaries between high and low pn velocity such as plate boundaries sutures and faults between plates and orogens sn velocity shows a very similar pattern to pn velocity a geodynamic cartoon is proposed to show the relationship between velocity and tectonics indicating that the sutures are boundaries with high dip angles and the plate boundaries are low angle reverse faults in the region

lithospheric anisotropy beneath the pyrenees from shear wave splitting we investigate upper mantle anisotropy beneath the pyrenean range along three n s profiles across the mountain belt the results of a first profile that operated in 1993 in the central part of the belt have been presented elsewhere we present the results of two other profiles that ran in 1995 1996 and 1996 1997 in the eastern and western part of the belt respectively and propose an interpretation of the whole results teleseismic shear waves sks skks and pks are used to determine splitting parameters the fast polarization direction and the delay time t teleseismic shear wave splitting in the eastern pyrenees displays homogeneous values trending n100 e and t values in the range 1 1 to 1 5 s a station located in the southern massif central 100 km north of the range is characterized by different splitting parameters n70 e t 0 7 s in the western part of the belt anisotropy parameters are similar across the whole belt n110 e and t 1 3 to 1 5 s most of the measured delay times including those obtained in the central part of the range are above the global average of the sks splitting around 1 s at the belt scale is generally poorly correlated with recent estimations of the absolute plate motion which predicts a fast direction ranging between n50 e and n80 e instead the orientation of n100 e is parallel to the trend of the pyrenean belt but also to hercynian preexisting structures this parallelism supports an anisotropy primarily related to frozen or active lithospheric structures we show that a signature related to the pyrenean orogeny is likely for the stations located in the internal domains of the belt by contrast the anisotropy measured at the stations located on the external parts of the belt could reflect a pre pyrenean hercynian deformation we suggest that a late hercynian strike slip deformation is responsible for this frozen upper mantle anisotropy and that the pyrenean tectonic fabric developped parallel to this preexisting fabric finally no particularly strong splitting is related to the north pyrenean fault commonly believed to represent the plate boundary between iberia and eurasia

uppermost mantle velocities and anisotropy beneath europe pn data collected within southern europe and the mediterranean are used to tomographically image variations in both seismic velocity and seismic anisotropy seismic anisotropy is an essential part of the inversion and without it several low velocity features within the uppermost mantle could not be properly imaged the technically active mantle of southern europe has much lower seismic velocities 7 6 8 1 km s than the more stable mantle of the sub african plate of the adriatic sea 8 3 km s however the most dramatic features within europe s uppermost mantle relate to the apennine dinaride and hellenide arcs these arcs all have extremely low 5 amounts of arc parallel anisotropy the tyrrhenian and aegean back arc regions also show low velocities 7 7 7 9 km s but less anisotropy the same may be true for the pannonian basin but the tomography has poorer resolution there a model explaining these observations focuses on subducted water metasomatizing the mantle wedge the addition of water causes melting creates arc volcanism lowers the seismic velocity and enhances the formation of anisotropy due to preferential olivine orientation for collisional arcs of the northern mediterranean arc parallel anisotropy has formed in response to compression across them and extension along them within back arc regions water is no longer a major factor instead convection associated with subduction and back arc extension controls the anisotropy

geodynamics of the emile baudot escarpment and the balearic promontory western mediterranean abstract the 348 km long 105 155 km wide and 1000 2000 m high northeast trending balearic promontory separates the valencia trough to the northwest from the south balearic algerian basin to the southeast it consists of three blocks ibiza at the southwest end mallorca in the center and menorca at the northeast end of the promontory the ibiza and mallorca blocks were thrust faulted and folded in the miocene the menorca block appears to be undisturbed but strata within the transform separating the mallorca and menorca blocks are folded and faulted miocene and younger volcanic pinnacles also are extensive along the transform separating the ibiza and mallorca blocks we infer that the tectonic features on the balearic promontory are the creations of the late oligocene miocene southeast migration of the blocks making up the promontory way from the spanish margin leading to the opening of the valencia trough behind them the westward displacement of the alboran microplate along the emile baudot escarpment on the southeast side of the promontory and the opening of the south baleric algeria basin behind it and the clockwise rotation of the ibiza and mallorca blocks produced by the passing alboran microplate

imaging poisson s ratio of the uppermost mantle beneath china we have obtained a poisson s ratio image of the uppermost mantle beneath china by performing tomographic inversion of travel time differences between sn and pn the arrival pairs were selected from the annual bulletin of chinese earthquakes from 1985 to 2007 and from the international seismological center isc data set between 1985 and 2005 the data include 58 663 arrival pairs from 10 486 earthquakes recorded at 204 stations the average poisson s ratio is 0 266 the preliminary tomographic results show that 1 the pseudowave velocity is high and the velocity ratio v p v s and poisson s ratio are low in the stable cratons around the tibetan plateau such as the tarim and junggar basins the ordos craton and the southern region of the sichuan basin 2 a low pseudowave velocity and high velocity ratio and poisson s ratio exist in the central and northern tibetan plateau the north south seismic zone and north china and 3 the high velocity ratio and poisson s ratio region in the tibetan plateau extends to the surrounding cratons suggesting that the uplift of the tibetan plateau results from a high poisson s ratio or partially melted rocks beneath the plateau and that the softer rocks have intruded into the upper mantle of surrounding cratons

messinian salinity crisis regulated by competing tectonics and erosion at the gibraltar arc the persistent shallow connection between the atlantic ocean and the mediterranean sea that caused the messinian salinity crisis may have been sustained by a balance between tectonic uplift and erosion due to inflow about six million years ago a series of geological factors drastically reduced the exchange of water between the atlantic ocean to the mediterranean sea through what is now the strait of gibraltar the resulting widespread salt precipitation in the mediterranean linked to a decrease in sea level of about 1 5 kilometres due to evaporation is known as the messinian salinity crisis the exact mechanism that caused the crisis remains uncertain here daniel garcia castellanos and antonio villasenor propose a competition between the obstruction of the gibraltar arc seaway by tectonic uplift and its erosional deepening by water inflow controlled by the resulting changes in sea level difference across the gibraltar arc as a possible mechanism for the crisis the messinian salinity crisis1 2 5 96 to 5 33 million years ago was caused by reduced water inflow from the atlantic ocean to the mediterranean sea resulting in widespread salt precipitation and a decrease in mediterranean sea level of about 1 5 kilometres due to evaporation3 the reduced connectivity between the atlantic and the mediterranean at the time of the salinity crisis is thought to have resulted from tectonic uplift of the gibraltar arc seaway and global sea level changes both of which control the inflow of water required to compensate for the hydrological deficit of the mediterranean1 4 however the different timescales on which tectonic uplift and changes in sea level occur are difficult to reconcile with the long duration of the shallow connection between the mediterranean and the atlantic5 needed to explain the large amount of salt precipitated here we use numerical modelling to show that seaway erosion caused by the atlantic inflow could sustain such a shallow connection between the atlantic and the mediterranean by counteracting tectonic uplift the erosion and uplift rates required are consistent with previous mountain erosion studies with the present altitude of marine sediments in the gibraltar arc6 7 and with geodynamic models suggesting a lithospheric slab tear underneath the region8 9 10 the moderate mediterranean sea level drawdown during the early stages of the messinian salinity crisis3 5 can be explained by an uplift of a few millimetres per year counteracted by similar rates of erosion due to atlantic inflow our findings suggest that the competition between uplift and erosion can result in harmonic coupling between erosion and the mediterranean sea level providing an alternative mechanism for the cyclicity observed in early salt precipitation deposits and calling into question previous ideas regarding the timing of the events that occurred during the messinian salinity crisis1

pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the arabian eurasian and african plates an edited version of this paper was published by blackwell publishing in geophysical journal international copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02355 x http atlas geo cornell edu middleeastnorthafrica publications al lazki2004 htm

the use of laboratory velocity data for estimating temperature and partial melt fraction in the low velocity zone comparison with heat flow and electrical conductivity studies peridotite is widely considered to be the dominant component of the upper most mantle seismic velocities of a dry peridotite determined in the laboratory at high pressure and hypersolidus temperature show a rapid decrease with increasing temperature the strong temperature dependence of velocities can be used to estimate temperature and melt fraction in the low velocity zone of the earth the laboratory results show that the pressure dependence of both velocity and melt fraction appears to be well accounted for by the pressure dependence of the solidus temperature of the peridotite i e homologous temperature dependence this observation allows us to extrapolate laboratory results to higher pressures greater depths with some confidence requiring only a knowledge of the solidus as a function of pressure using the ratios of lithospheric to asthenospheric velocities temperature and melt fraction in the asthenosphere the low velocity zone can be determined from laboratory velocity data examples of thermal structures of the upper mantle beneath oceanic plates are presented we choose three locations of geophysical interest iceland plateau pacific ocean and philippine sea where reliable seismic velocities have been determined in the upper mantle from surface wave studies a large amount of partial melt 5 vol and a higher temperature than the dry peridotite solidus are inferred in 0 5 m y asthenosphere under the iceland plateau and the active marginal basin of the east philippine sea the partial melt zone appears to extend deeper 100 km and to greater ages 20 m y in the pacific ocean region than under the slowly spreading iceland plateau partial melting is not expected in the asthenosphere older than 5 m y under the iceland plateau even though the volume fraction of partial melt is not so large 3 vol beneath the pacific plate the melting zone may extend to a distance of above 2000 km from the ridge many seamounts observed in the pacific ocean may result from this vast region of melting under the plate we suggest a linear relation between the width of melting zone and the plate velocity the laboratory results are also applied to other low velocity zones it is suggested that a velocity drop up to about 6 in the asthenosphere does not necessarily require the existence of partial melt but can be explained by high subsolidus temperature this implies that partial melt may not exist generally but only in limited areas in the low velocity zone comparison of seismic results with theoretical models may overestimate the temperature and melt fraction if the velocity drop at subsolidus temperature is neglected temperature and melt fraction obtained in this study are discussed together with results from heat flow and electrical studies almost the same temperatures as inferred from seismic velocity and a dry peridotite solidus are calculated from heat flow data indicating that the upper mantle under mid ocean ridges may be fairly dry even a water or co2 undersaturated solidus 0 1 wt does not give a temperature consistent with the lithospheric geotherm and laboratory velocity results it is noted that electrical conductivity studies generally yield lower temperatures and larger melt fractions than this study unknown pressure frequency and impurity effects on laboratory conductivities of partially molten mantle rocks are suggested as possible reasons for this discrepancy

topo europe understanding of the coupling between the deep earth and continental topography linking different spatial and temporal scales in coupled deep earth and surface processes is a prime objective of the multidisciplinary international research program topo europe the research approach of topo europe integrates active collection of new data reconstruction of the geological record and numerical and analog modeling the results of the program presented in this special volume focus on four closely interrelated topics crustal and upper mantle structures lithosphere geodynamics sedimentary basin dynamics and surface processes quantitative understanding of topographic evolution in space and time requires study of processes from the upper mantle through the lithosphere and crust and acting on the earth s surface the results presented here demonstrate the opportunities to further understanding of topography through integrated studies of the full earth system across space and timescales

2 d anisotropic pn velocity tomography underneath germany using regional traveltimes summary this paper complementing the recent 1 d pn time term analysis of song et al 2001a presents tomographic inversions of regional pn traveltimes to image lateral variations of seismic velocity and anisotropy within the uppermost mantle beneath germany as such our study fills a gap of previous regional 2 d anisotropic pn studies for france and italy by expanding anisotropic pn tomography to a continental scale covering much of europe in a novel way the resolving power of the used pn tomography system is investigated through a series of checkerboard tests combined with tradeoff analyses between resolution and covariance of the models methodologically important and commonly interesting problems of seismic tomography are addressed with the data set such as model parametrization for a given source receiver configuration effects of time terms on the model parameters and ambiguity between lateral velocity perturbations and anisotropy the reliability and significance of various inversion models 1 d 2 d isotropic anisotropic is investigated in detail using statistical f tests the latter indicate that while both 2 d isotropic and anisotropic models provide better fits of the pn data than a standard homogeneous isotropic upper mantle the most significant improvement arises from a large scale 1 d anisotropy ellipsoid with the fast pn velocity axis in 25 ne direction this result correlates well with a number of trends related to upper mantle and plate dynamics for example major plate motion besides this anisotropic dominant traveltime pattern we observe a number of lateral velocity anomalies lower than average velocities were detected in the southwestern rhenish massif but not in the area of the eifel plume similar to findings for the adjacent region in france in addition lower velocities are seen in parts of the alps and in a

sks splitting measurements beneath northern apennines region a case of oblique trench retreat abstract we present here the new observations of seismic anisotropy obtained from sks birefringence analysis we studied 27 teleseismic earthquakes recorded by the temporary seismic network of retreat project in the northern apennines region for each station event couple we calculate the anisotropic parameters delay time and fast polarization direction by minimizing the energy in the transverse component our measurements confirm the existence of two domains the tuscany domain on the south west with respect to the apennines shows mostly nw se fast axes directions with a rotation toward e w direction moving toward the tyrrhenian sea the adria domain north east of the apennines orogen shows more scattered measurements with prevailing n s to nne ssw directions also with back azimuthal dependence the transition between the two domains is abrupt in the northern part of the study region but more gradual in the southern part measured delay times 1 8 s on average suggest that the detected anisotropy is located principally in the asthenosphere beneath the adria domain where the presence of a double layer structure seems consistent a lithospheric contribution is plausible an interpretation in terms of ongoing mantle deformation suggests a differential evolution of the trench retreat process along the northern apennines orogen the orogen parallel anisotropy in the study region is beneath the inner part of the belt instead of beneath its crest and no orogen normal measurements are found in the tuscany side compared to the anisotropy pattern of the typical slab retreat seen in southern part of the northern apennines in the northernmost one the anisotropy suggests that an oblique trench retreat has occurred possibly linked to northern apennines retreat since 5 ma

anisotropic pn tomography of turkey and adjacent regions summary this study presents an analysis of pn traveltimes to determine lateral variations of velocity anisotropy of uppermost mantle and crustal thickness beneath turkey and adjacent regions from 1999 to 2010 more than 50 000 pn arrivals are compiled from 700 regional earthquakes and 832 stations of permanent and temporary networks operated in the study area we used a regularized least squares inversion to estimate the uppermost mantle parameters the results reveal features that correlate well with the geology and the active tectonics of the region overall thepnvelocitiesshowveryfast 8 4kms 1 andveryslow 8 3 km s 1 western black sea basin 8 3 km s 1 adriatic sea 8 3 km s 1 and zagros suture 8 3 km s 1 pn anisotropy has maximum amplitude of 0 6 km s 1 in the study area the largest and coherent anisotropic anomalies are observed in the western anatolia aegean sea and cyprian arc pn anisotropy in western anatolia aegean sea and greece correlate well with the present deformation of n s regional extension no clear correlation between anisotropy and the shear deformation along the north anatolian fault was observed the majority of the stations in central anatolia show small station residuals indicating the average crustal thickness of 35 2 km western anatolia and the aegean sea have crustal thicknesses between 28 2 and 33 2 km in greece the crustal thicknesses are increasing from 33 3 km from the western coast to a maximum of 48 3k m beneath dinarides hellenides the large crustal thicknesses are also observed along southern coast of anatolia 40 48 km

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

uppermost mantle structure of the australian continent from pn traveltime tomography past studies of the seismic structure of the australian continent have dominantly exploited surface wave tomography for the mantle with seismic refraction receiver functions and ambient noise used for crustal structure the 3 d structure has been summarized in the australian seismological reference model ausrem for which the zone immediately below the crust is the least well characterized pn traveltime tomography provides a way of improving structural information on the uppermost mantle across the continent we have exploited waveforms from larger events across australia recorded at both permanent and portable stations since 1993 supplemented by bulletin arrival times to compensate for the large velocity contrasts with much faster mantle wave speeds in the center and west all events were relocated using the ausrem model after relocation consistent patterns of traveltime residuals are obtained we extract pn as the first arrival in the distance range 1 8 to 15 we use the fmtomo approach to invert the travel time residuals to generate a p wave speed structure with a resolution of 3 3 there is strong heterogeneity in pn wave speed in the uppermost mantle across the continent the fastest pn wave speed of 8 36 km s beneath the precambrian cratons of western and central australia is 3 99 faster than the global ak135 model and the slowest pn wave speed 7 66 km s on the eastern margin is 4 74 slower the slowest velocities in the uppermost mantle are found along the eastern margin of the australian continent beneath the phanerozoic orogenic belts with links to neogene volcanism

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

anisotropic pn tomography in the western united states pn travel times are affected not only by lateral variations in crust and mantle velocity but also by significant amounts of laterally varying anisotropy to investigate uppermost mantle anisotropy a tomography algorithm was reformulated to include lateral variations in both velocity and horizontal anisotropy and it was applied to pn travel time data from the western united states results show that anisotropy is as important in explaining the travel time residuals as are the velocity variations a detailed resolution study examined the trade off between the velocity variations and the anisotropy variations and showed that both could be resolved for regions with good ray path coverage pn anisotropy beneath the western united states has maximum amplitudes of 0 3 km s 7 5 when resolved on a length scales of around 3 the orientations of pn anisotropy often correlate well with those inferred from shear wave splitting results this correlation suggests that orientation of mantle anisotropy does not change significantly with depth for many regions the orientation of the pn anisotropy can be correlated with some of the tectonic processes which occur within the western united states for example the fast direction of pn anisotropy parallels the northeast direction of subduction of the juan de fuca plate beneath the northwest pacific coast suggesting that there the anisotropy is related to subduction driven deformation the fast direction of pn anisotropy also parallels the strike of the san andreas fault system in central california indicating that shear strains along the plate boundary may be responsible for the anisotropy there within the great basin the pn anisotropy varies substantially and both partial melting and small scale convection within the uppermost mantle could be responsible for these anisotropy variations

active and fossil mantle flows in the western alpine region unravelled by seismic anisotropy analysis and high resolution p wave tomography abstract the anisotropy of seismic velocities in the mantle when integrated with high resolution tomographic models and geologic information can be used to detect active mantle flows in complex plate boundary areas providing new insights on the impact of mantle processes on the topography of mountain belts here we use a densely spaced array of temporary broadband seismic stations to analyze the seismic anisotropy pattern of the western alpine region at the boundary between the alpine and apenninic slabs our results are supportive of a polyphase development of anisotropic mantle fabrics possibly starting from the jurassic to present geophysical data presented in this work and geologic evidence taken from the literature indicate that i fossil fabrics formed during tethyan rifting may be still preserved within the alpine and apenninic slabs ii mantle deformation during apenninic slab rollback is not compensated by a complete toroidal flow around the northern tip of the retreating slab iii the previously observed continuous trend of anisotropy fast axes near parallel to the western alpine arc is confirmed we observe that this arc parallel trend of fast axes is located in correspondence to a low velocity anomaly in the european upper mantle beneath regions of the western and ligurian alps showing the highest uplift rates we propose that the progressive rollback of the apenninic slab in the absence of a counterclockwise toroidal flow at its northern tip induced a suction effect at the scale of the supraslab mantle the resulting mantle flow pattern was characterized by an asthenospheric counterflow at the rear of the unbroken western alps slab and around its southern tip and by an asthenospheric upwelling mirrored by low p wave velocities that would have favored the topographic uplift of the alpine belt from the mont blanc to the mediterranean sea

an experimental study of the garnet perovskite transformation in the system mgsio3mg3al2si3o12 phase transformations in the system mgsio3 mg3al2si3o12 have been studied at pressures between 22 and 28 gpa at 1500 c using a multi anvil apparatus majorite garnet with less than about 10 wt al2o3 was found to completely transform into an orthorhombic perovskite structure over a pressure interval between 24 and 27 gpa whereas pyrope garnet disproportionated into sub aluminous perovskite plus corundum solid solutions at pressures greater than 26 5 gpa alumina contents in the perovskite structure are dependent on temperature and increase from 11 wt at 1500 c to 17 wt at 1800 c at a pressure of 27 gpa the alumina content of perovskite also in creases with increasing pressure such that aluminous perovskite with the pyrope composition 25 mol al2o3 should be formed by about 30 40 gpa these observations are consistent with our recent experimental results on a pyrolite composition which demonstrated that no separate aluminous phase exists in the upper part of the lower mantle the entire inventory of al2o3 in pyrolite can be accommodated in solid solution in magnesium silicate perovskite

crustal structure beneath the iberian peninsula and surrounding waters a new compilation of deep seismic sounding results abstract we present here an updated compilation of crustal parameters beneath the iberian peninsula and surrounding waters inferred from extensive deep seismic exploration performed in the last three decades firstly the more relevant experiments developed in both terrestrial and marine domains are revisited together with the corresponding seismic velocity depth models published that reveal the characteristics of the different tectonic domains sampled including oceanic zones continental margins orogenic and rift belts the results are summarized in three crustal transects sketched along representative directions secondly we compiled the moho depths along all the available seismic profiles to produce a geo referred database this database has then been interpolated using kriging algorithms to obtain a continuous moho depth model in the form of a regular grid file this integrative moho map for a key area in the western mediterranean documenting the interaction between european and african plates can contribute to constrain further regional studies either at crustal lithospheric or mantle scales

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

three dimensional s velocity of the mantle in the africa eurasia plate boundary region from phase arrival times and regional waveforms 1 a new model of the three dimensional shear velocity structure of the africa eurasia plate boundary is presented the new model is derived by jointly inverting different types of seismic data the two main sources of information are regional waveforms and teleseismic s wave arrival times we show that it is possible to find a model that fit the different data types nearly as well as when inverting solely one type of data the main improvement in resolving power is achieved between depths of 300 and 700 km though the improvements are not limited to this depth range our model reflects the complicated evolution of this plate boundary area the transition zone is dominated by high velocity anomalies which we infer to represent a mix of lithosphere that subducted relatively recently or is not sufficiently cold and dense to traverse the 660 km discontinuity the only low velocity zone in the transition zone is beneath the ionian sea the high velocity hellenic slab is continuous throughout the upper mantle and into the lower mantle to about 1200 km most likely representing subducted neo tethys lithosphere the uppermost mantle is dominated by low velocities consistent with the high level of tectonic activity low velocity regions are relatively strong beneath the mid atlantic ridge turkey and the dead sea region the region s current lithosphere is relatively thin except beneath the adriatic and ionian seas and the easternmost atlantic ocean

seismic anisotropy within the uppermost mantle of southern germany summary this paper presents an updated interpretation of seismic anisotropy within the uppermost mantle of southern germany the dense network of reversed and crossing refraction profiles in this area made it possible to observe almost 900 traveltimes of the p phase that could be effectively used in a time term analysis to determine horizontal velocity distribution immediately below the moho for 12 crossing profiles amplitude ratios of the p phase compared to the dominant crustal phase were utilized to resolve azimuthally dependent velocity gradients with depth a p wave anisotropy of 3 4 per cent in a horizontal plane immediately below the moho at a depth of 30 km increasing to 11 per cent at a depth of 40 km was determined for the axis of the highest velocity of about 8 03 kms at a depth of 30 km a direction of n31 e was obtained the azimuthal dependence of the observed p amplitude is explained by an azimuth dependent sub moho velocity gradient decreasing from 0 06 s in the fast direction to 0 s in the slow direction of horizontal p wave velocity from the seismic results in this study a petrological model suggesting a change of modal composition and percentage of oriented olivine with depth was derived

belt parallel mantle flow beneath a halted continental collision the western alps constraining mantle deformation beneath plate boundaries where plates interact with each other such as beneath active or halted mountain belts is a particularly important objective of mantle tectonics that may bring a depth extent to the earth s surface observation such mantle deformation can be mapped at scale lengths of several tens of kilometers through the analysis of seismological data and particularly by mapping seismic anisotropy from the splitting analysis of vertically propagating sks waves that largely reflect the strain induced crystal preferred orientations of the rock forming minerals within the upper mantle in the present study we analyse data from approximately 50 broadband seismic stations covering the western alps and we provide a coherent picture of upper mantle anisotropy beneath the belt the large scale anisotropy pattern is characterized by fast split directions that closely follow the trend of the belt moreover the maximum anisotropy magnitude is not located beneath the internal zones of the belt but instead beneath external units all suggests that the anisotropy is likely dominated by sublithospheric mantle deformation we propose that the observed anisotropy pattern can be explained by recent or active mantle flow around the eurasian slab presently plunging beneath the inner parts of the alps

teleseismic p wave polarization analysis at the grafenberg array p wave polarization at the grafenberg array grf in southern germany is analysed in terms of azimuthal deviations and deviations in the vertical polarization using 20 yr of broad band recordings an automated procedure for estimating p wave polarization parameters is suggested based on the definition of a characteristic function which evaluates the polarization angles and their time variability as well as the amplitude linearity and the signal to noise ratio of the p wave p wave polarization at the grf array is shown to depend mainly on frequency and backazimuth and only slightly on epicentral distance indicating depth dependent local anisotropy and lateral heterogeneity a harmonic analysis is applied to the azimuthal anomalies to analyse their periodicity as a function of backazimuth the dominant periods are 180 and 360 at low frequencies between 0 03 and 0 1 hz the observed fast directions of azimuthal anisotropy inferred from the 180 periodicity are similar across the array the average fast direction of azimuthal anisotropy at these frequencies is n20 e with an uncertainty of about 8 and is consistent with fast directions of pn wave propagation lateral velocity gradients determined for the low frequency band are compatible with the moho topography of the area a more complex pattern in the horizontal fast axis orientation beneath the grf array is observed in the high frequency band between 0 1 and 0 5 hz and is attributed to anisotropy in the upper crust a remarkable rotation of the horizontal fast axis orientation across the suture between the geological units moldanubicum and saxothuringicum is observed in contrast the 360 periodicity at high frequencies is rather consistent across the array and may either point to lower velocities in the upper crust towards the bohemian massif and or to anisotropy dipping predominantly in the ne sw direction altogether p wave polarization analysis indicates the presence of layered lithospheric anisotropy in the area of the grf array seismic anisotropy is more variable in the brittle upper crust compared to lower crustal and subcrustal depths

e w opening of the algerian basin western mediterranean we present geophysical and geological evidence of fast 2 cm yr 1 in the east and 5 cm yr 1 in the west e w spreading between 16 and 8 ma in the region behind the gibraltar arc in the algerian basin

propagation of regional seismic phases lg and sn and pn velocity structure along the africa iberia plate boundary zone tectonic implications we used over 1000 regional waveforms recorded by 60 seismic stations located in northwest africa and iberia to map the efficiency of l g and sn wave propagation beneath the gulf of cadiz alboran sea and bounding betic rif and atlas mountain belts crustal attenuation is inferred from the tomographic inversion of l g pg amplitude ratios upper mantle attenuation is inferred from maps of sn propagation efficiency derived by inversion of well defined qualitative efficiency assignments based on waveform characteristics regions of l g attenuation correlate well with areas of thinned continental or oceanic crust significant sedimentary basins and lateral crustal variations comparison of the sn efficiency results with velocities obtained from an anisotropic pn traveltime inversion shows a fairly good correlation between regions of poor sn efficiency and low pn velocity a low pn velocity 7 6 7 8 km s 1 and significant sn attenuation in the uppermost mantle is imaged beneath the betics in southern spain in sharp contrast to the relatively normal pn velocity 8 0 8 1 km s 1 and efficient sn imaged beneath the alboran sea slow pn velocity anomalies are also imaged beneath the rif and middle atlas in morocco we do not identify any conclusive evidence of lithospheric scale upper mantle attenuation beneath the rif although the crust in the gibraltar region appears highly attenuating making observations at stations in this region ambiguous paths crossing the gulf of cadiz eastern atlantic and the moroccan and iberian mesetas show very efficient sn propagation and are imaged with high pn velocities 8 1 8 2 km s 1 the spatial distribution of attenuation and velocity anomalies lead us to conclude that some recovery of the mantle lid beneath the alboran sea must have occurred since the early miocene episode of extension and volcanism we interpret the low velocity and attenuating regions beneath the betics and possibly the rif as indicating the presence of partial melt in the uppermost mantle which may be underlain by faster less attenuating mantle in the light of observations from other geophysical and geological studies the presence of melt at the base of the betic crust may be an indication that delamination of continental lithosphere has played a role in the neogene evolution of the alboran sea region

crustal structure and orogenic material budget in the west central pyrenees surface and subsurface data are combined to construct a crustal scale cross section of the western central pyrenees france and spain at the boundary between the european and iberian plates the position of moho reflections in the ecors arzacq reflection profile suggests a tectonic wedge of european crust and upper mantle had indented the iberian plate at lower crustal levels the european wedge is overlain by an upper iberian wedge thus constituting a double stacked wedge geometry the upper wedge was delaminated and deformed giving rise to the pyrenean orogenic prism manifested as a bivergent fan in upper crustal levels the underthrust lower iberian plate has been imaged to depths of 55 60 km but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km total orogenic contraction calculated from surface structures is about 75 80 km which was accomplished between the latest cretaceous and the early miocene at an averaged rate of 1 2 mm yr consistent with these moderate values exhumation of the orogen is much less than in the more shortened eastern parts of the range paleozoic basement and preorogenic mesozoic rocks are little eroded and much of the exhumation involved cannibalization of early foreland basins which once covered the entire poorly emergent orogen at this transect this resulted in a continuous process of sediment recycling and coupled with a considerable lateral arrival of material a bulk negative erosion sedimentation budget

extreme mesozoic crustal thinning in the eastern iberia margin the example of the columbrets basin valencia trough eastern iberia preserves a complex succession of mesozoic rifts partly or completely inverted during the late cretaceous and cenozoic in relation with africa eurasia convergence notably the valencia trough classically viewed as part of the cenozoic west mediterranean basins preserves in its southwestern part a thick mesozoic succession locally 10 km thick over a highly thinned continental basement locally only 3 5 km thick this subbasin referred to as the columbrets basin represents a late jurassic early cretaceous hyperextended rift basin weakly overprinted by subsequent events its initial configuration is well preserved allowing us to unravel its 3 d architecture and tectonostratigraphic evolution in the frame of the mesozoic evolution of eastern iberia the columbrets basin benefits from an extensive data set combining high resolution seismic reflection profiles drill holes seismic refraction data and expanding spread profiles the interactions between halokinesis involving the upper triassic salt and extensional deformation controlled the architecture of the mesozoic basin the thick uppermost triassic to cretaceous succession displays a large scale syncline shape progressively stretched and dismembered toward the basin borders we propose that the se border of the basin is characterized by a large extensional detachment fault acting at crustal scale and interacting locally with the upper triassic decollement this extensional structure accommodates the exhumation of the continental basement and part of the crustal thinning eventually our results highlight the complex interaction between extreme crustal thinning and occurrence of a prerift salt level for the deformation style and tectonostratigraphic evolution of hyperextended rift basins

analog and numerical experiments of double subduction systems with opposite polarity in adjacent segments datasets for this article are available in 655 http hdl handle net 20 500 11850 364963 doi 10 3929 ethz b 000364963

constraining the crustal root geometry beneath northern morocco abstract consistent constraints of an over thickened crust beneath the rif cordillera n morocco are inferred from analyses of recently acquired seismic datasets including controlled source wide angle reflections and receiver functions from teleseismic events offline arrivals of moho reflected phases recorded in rifsis project provide estimations of the crustal thicknesses in 3d additional constraints on the onshore offshore transition are inferred from shots in a coeval experiment in the alboran sea recorded at land stations in northern morocco a regional crustal thickness map is computed from all these results in parallel we use natural seismicity data collected throughout topoiberia and picasso experiments and from a new rifsis deployment to obtain receiver functions and explore the crustal thickness variations with a h grid search approach this larger dataset provides better resolution constraints and reveals a number of abrupt crustal changes a gridded surface is built up by interpolating the moho depths inferred for each seismic station then compared with the map from controlled source experiments a remarkably consistent image is observed in both maps derived from completely independent data and methods both approaches document a large crustal root exceeding 50 km depth in the central part of the rif in contrast with the rather small topographic elevations this large crustal thickness consistent with the available bouguer anomaly data favors models proposing that the high velocity slab imaged by seismic tomography beneath the alboran sea is still attached to the lithosphere beneath the rif hence pulling down the lithosphere and thickening the crust the thickened area corresponds to a quiet seismic zone located between the western morocco arcuate seismic zone the deep seismicity area beneath western alboran sea and the superficial seismicity in alhoceima area therefore the presence of a crustal root seems to play also a major role in the seismicity distribution in northern morocco

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