ambient noise tomography of the pyrenees and the surrounding regions inversion for a 3 d vs model in the presence of a very heterogeneous crust we thank all participants in the fieldwork and the municipalities and landlords that hosted a pyrope temporary station we also acknowledge sismob the french seismic mobile pool a com ponent of the resif research facility for providing us with the seismological instrumentation for the temporary deployments we used data from the fr and rd resif g geoscope and ca institut cartogr afic i geol ogic de catalunya permanent net works resif http portal resif fr is a national research infras tructure recognized as such by the french ministry of higher education and research resif is managed by the resif con sortium composed of 18 research institutions and universities in france resif additionally supported by a public grant overseen by the french national research agency anr as part of the investissements d avenir program reference anr 11 eqpx 0040 andthefrenchministryofecology sustainabledevelopment and energy the pyrope experiment was supported by the french research agency anr blanc program project pyrope anr 09 blan 0229 this is a contribution of the team consolider ingenio 2010 topo iberia csd2006 00041 c

crustal structure due to collisional and escape tectonics in the eastern alps region based on profiles alp01 and alp02 from the alp 2002 seismic experiment 1 alp01 and alp02 are the longest profiles recorded during alp 2002 a large international seismic refraction and wide angle reflection experiment undertaken in the eastern alps in 2002 alp01 crosses the alpine orogen from north to south thus providing a cross section mainly affected by the collision between europe and the adriatic microplate alp02 extends from the eastern alps to the pannonian basin supplying evidence on the relation between alpine crustal structure and tectonic escape to the pannonian basin during this experiment 363 single channel recorders were deployed along these profiles with an average spacing of 3 2 km recordings from 20 inline shots were used in this study two dimensional forward modeling using interactive ray tracing techniques produced detailed p wave velocity models that contain many features of tectonic significance along alp01 the european moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the eastern to the southern alps the adriatic moho continues further south at a significantly shallower depth moho topography and a prominent south dipping mantle reflector in the alpine area support the idea of southward subduction of the european lithosphere below the adriatic microplate the most prominent tectonic feature on the alp02 profile is a vertical step of the moho at the transition between the alpine and pannonian domains suggesting the existence of a separate pannonian plate fragment the development of the pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the alpine collision area to the pannonian basin

insights on the upper mantle beneath the eastern alps analyses of ps and sp receiver functions from datasets collected by permanent and temporary seismic stations image a seismic discontinuity due to a negative velocity contrast across the entire eastern alps the receiver functions show the presence of the discontinuity within the upper mantle with a resolution of tens of kilometers laterally it is deeper 100 130 km below the central portion of the eastern alps and shallower 70 80 km towards the pannonian basin and in the central alps comparison with previous studies renders it likely that the observed discontinuity coincides with the lithosphere asthenosphere boundary lab east of 15 e longitude while it could be associated with a low velocity zone west of 15 e

evolution of retreating subduction boundaries formed during continental collision retreating subduction boundaries formed where the rate of subduction exceeds the rate of overall plate convergence appear to be commonly developed features within regions of early or incomplete continent continent collision they are characterized by regional extension within the overriding plate and at their leading edge by thin skinned arcuate thrust belts that are concave towards the overriding plate as is illustrated by examples from the mediterranean region the formation of retreating subduction boundaries is intimately related to the process of continental collision during the early stages of collision retreating subduction boundaries are commonly formed by lateral ejection from zones of crustal shortening along the main collision boundary retreating plate boundaries can also form before the main collision and the associated thrust belts emplaced as precollisional accretionary assemblages because the driving mechanism for retreating subduction boundaries appears to be gravity acting on a dense subducted slab slab pull subduction usually ceases when and only when thick buoyant continental crust enters the subduction zone thus differences in the evolution and duration of retreating subduction systems can be largely attributed to the size and configuration of the deep water regions available to be subducted in some cases retreating subduction boundaries may escape into the open ocean where they form nearly isolated local tectonic systems in these systems the rate of subduction is approximately compensated by the rate of upper plate extension and migration of the system across the oceanic region may be very rapid for example the horseshoe seamounts located about 800 km offshore in the eastern north atlantic may be the active expression of an east dipping westwardly migrating retreating subduction boundary that has evolved from the betic cordillera rif system active in miocene time and may now be progressing across the atlantic at approximately 50 mm yr an analogous situation may be represented by the scotia arc system a westward dipping retreating subduction system located between the south american and antarctic plates which may have escaped into the south atlantic ocean from a zone of crustal shortening in the andes and is now progressing across the atlantic at a rate of about 80 mm yr

love waves from local traffic noise interferometry surface wave interferometry on local scale usually aims at recovering rayleigh waves this is because of the predominant use of vertical component geophones in exploration seismology and the fact that rayleigh waves occur for any given subsurface structure on the other hand love waves are present only in layered media and require horizontal component geophones for their observation as they depend on shear wave velocity structure and density only the analysis of love waves provides a potentially powerful supplement to rayleigh wave inversion perhaps surprisingly recent studies show that low frequency love waves 0 05 0 1 hz excited by the interaction of ocean waves with the ocean floor the earth s microseism can be recovered by interferometry and that their s n is high compared to rayleigh waves lin et al 2008 on a regional scale jay et al 2012 analyzed the ambient noise field in a volcanic region and found that love waves with frequencies of about 0 3 hz are observed more clearly than c

crustal structure of the carpathian pannonian region from ambient noise tomography we use ambient noise tomography to investigate the crust and uppermost mantle structure beneath the carpathian pannonian region of central europe over 7500 rayleigh wave empirical green s functions are derived from interstation cross correlations of vertical component ambient seismic noise recordings 2005 2011 using a temporary network of 54 stations deployed during the south carpathian project 2009 2011 56 temporary stations deployed in the carpathian basins project 2005 2007 and 100 permanent and regional broad band stations rayleigh wave group velocity dispersion curves 4 40 s are determined using the multiple filter analysis technique group velocity maps are computed on a grid of 0 2 0 2 from a non linear 2 d tomographic inversion using the subspace method we then inverted the group velocity maps for the 3 d shear wave velocity structure of the crust and uppermost mantle beneath the region our shear wave velocity model provides a uniquely complete and relatively high resolution view of the crustal structure in the carpathian pannonian region which in general is validated by comparison with previous studies using other methods to probe the crustal structure at shallow depths 30 km are relatively fast presumably related to shallowing of the moho consequent on the extensional history of the pannonian region

a new seismic data set on the depth of the moho in the alps we present the results from receiver function analysis applied to a comprehensive data set in the eastern alps teleseismic events were recorded at 70 stations with an average deployment of 1 year the investigated area includes the eastern part of the eastern alps and their transition to the bohemian massif the pannonian domain and the southern alps the crustal structure at each station is examined with the zhu kanamori zk method which yields well resolved interface depths in laterally homogeneous media with limited layering the application of the zk technique is challenged because of the complex tectonic setting therefore we include additional constraints from recent active source seismic studies in particular the well known crustal p wave velocity and where available the vp vs ratio are kept fixed thus reducing the ambiguity in determining moho depths individual depth values vary strongly between adjacent stations showing that the employment of the zk technique in tectonically complex settings is limited we therefore avoid interpreting the results in detail but rather compare them to existing crustal models of the eastern alps we regard this receiver function study in the easternmost part of the alps as a documentation of a data set that has potential to be exploited in the future

structure and elasticity of serpentine at high pressure abstract serpentines occur in the subduction zone settings both along the slab and within the mantle wedge they are candidates for transporting water in to the deep earth their presence is manifested by serpentine mud volcanoes high electrical conductivities magnetic and seismic anomalies using theoretical methods we predict a pressure induced structural transformations in serpentine the transformations are related to the behavior of the silicate framework and misfit between octahedral and tetrahedral layers as the structure is compressed the octahedral layer and tetrahedral layers are compressed at different rates at 7 gpa the misfit between the layers vanishes this causes non linear pressure dependence of tetrahedral rotational angle this is also manifested by the onset of anomalous pressure dependence of the elastic constants c 11 c 33 c 12 c 13 beyond 7 gpa the misfit between the layers grows again reaching extremum at 22 gpa this is also manifested by discontinuity in average si o bond length volume of tetrahedron and re orientation of hydroxyl vector the symmetry of the crystal structure however remains unaffected evidence of pressure induced hydrogen bonding is absent in serpentine as evident from reduction of o h bond length upon compression results of compression for the low pressure regime p k 0 79 gpa k 0 12 and k 0 2 where k is the bulk modulus prime indicates pressure derivatives and o refers to zero pressure our best estimates of k 0 k 0 and the gruneisen parameter at 300 k and zero pressure based on our results are 61 gpa 17 and 0 77 respectively at low pressures serpentine structure is anisotropic with c 11 2 4 c 33 the pressure derivative of elastic constants c ij p are such that around 22 gpa c 11 c 33 an elastic instability c 66 50 gpa is also noted the elastic constant tensor reveals large acoustic anisotropy 41 in v p and seismic wave velocities that are significantly higher than those inferred from experiments on serpentinites

crustal and uppermost mantle structure of the bohemian massif based on celebration 2000 data 1 the deep structure of the bohemian massif bm the largest stable outcrop of variscan rocks in central europe was studied using the data of the international seismic refraction experiment central european lithospheric experiment based on refraction celebration 2000 the data were interpreted by seismic tomographic inversion and by two dimensional 2 d trial and error forward modeling of p and s waves additional constraint on crustal structure was given by amplitude modeling using the reflectivity method and gravity modeling though consolidated the bm can be subdivided into several tectonic units separated by faults shear zones or thrusts reflecting varying influence of the cadomian and variscan orogeneses the saxothuringian barrandian moldanubian and moravian velocity models determine three types of crust mantle transition in the bm reflecting variable crustal thickness and delimiting contacts of tectonic units in depth the nw area the saxothuringian has a highly reflective lower crustal layer above moho with a strong velocity contrast at the top of this layer this reflective laminated lower crust reaches depths of 26 35 km and is characteristic for the saxothuringian unit which was subject to eastward subduction the moldanubian in the central part is characterized by the deepest 39 km and the most pronounced moho within the whole bm with a strong velocity contrast 6 9 8 1 km s 1 a thick crust mantle transition zone in the se with velocity increase from 6 8 to 7 8 km s 1 over the depth range of 23 40 km seems to be the characteristic feature of the moravian overthrusted by the moldanubian during variscan collision

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

magnetic properties opaque mineralogy and magnetic anisotropies of serpentinized peridotites from odp hole 670a near the mid atlantic ridge abstract magnetic mineralogy and magnetic properties of 16 samples of serpentinized peridotites harzburgites from odp hole 670a are studied the degree of serpentinization was determined by a new method which combines saturation magnetization and whole rock iron content a unique curie temperature t c of 580 c corresponding to pure magnetite was observed microprobe analyses whole rock metal content and curie temperatures indicate the absence of awaruite ni 3 fe or native metals hysteresis parameters reveal the contribution of pseudo single domain psd grains in samples with a low degree of serpentinization and large multi domain md grains in highly serpentinized samples with j rs j s 0 08 natural remanent magnetization nrm is mainly unstable and possibly composite particularly in the highly serpentinized samples the intensity j a of anhysteretic remanent magnetization arm in the geomagnetic field is much higher than j n intensity of nrm with j a j n averaging 2 4 the koenigsberger ratio q is low and susceptibility k depends on degree of serpentinization ranging from 1 2 to 51 5 10 6 m 3 kg 1 nrm inclinations are scattered with some tendency to lie near the horizontal plane which is close to the foliation plane anisotropies of susceptibility of arm and of saturation remanent magnetization srm were studied and compared with spinel foliation determined for three less serpentinized samples in these samples magnetic anisotropies seem to be mimetic of high temperature deformation before serpentinization when the degree of serpentinization is high later magnetic fabrics probably related to magnetite veins dominate previous anisotropies the temperature dependence of susceptibility and of viscous remanent magnetization vrm were studied the thermal variation of susceptibility shows a shallow hopkinson effect at about 300 400 c time dependence of induced and remanent magnetization increases with temperature reaching maximum values at about 300 400 c based on these observations induced magnetization and vrm of lower crustal and upper mantle rocks and their contribution to marine magnetic anomalies are discussed

ambient seismic noise eikonal tomography for near surface imaging at valhall the permanent ocean bottom array at the valhall field in norway provides an excellent source of passive seismic data to test what might be accomplished with seismic interferometry the array was installed in 2003 kommedal et al 2004 and data can be recorded for long periods in all weather conditions the subsurface structure is well known both from numerous wells and from seismic imaging during periods without active seismic acquisition at valhall there is abundant passive energy in the data over a wide range of fre quencies

the effects of serpentinization on density and magnetic susceptibility a petrophysical model abstract new measurements are presented of initial magnetic susceptibility and density for serpentinized harzburgites from the josephine peridotite oregon an inverse correlation between density and susceptibility which is typical of these rocks and similar rocks from other localities is not explained by simple serpentinization reactions calculations of density and susceptibility as a function of reaction progress for reactions that produce magnetite show susceptibilities that are larger than those observed at low degrees of serpentinization susceptibilities of fe bearing serpentine and brucite are calculated from a molecular field model initially developed for the olivine and orthopyroxene solid solutions at high degrees of serpentinization susceptibilities that are lower than those observed are predicted by reactions where iron is sequestered by serpentine and brucite observed density susceptibility trends of serpentinized harzburgites fall between the values predicted by these limiting reactions the observed properties may be modelled by multiple reactions involved in multi stage serpentinization processes such that the production of magnetite increases with the degree of serpentinization the empirical and calculated properties provide a complementary characterization of density and susceptibility values of serpentinites

lunar daily geomagnetic variations in new zealand summary lunar daily geomagnetic variations l exhibit distinctive behaviour at many sites near coasts in this study data from an array of three component magnetometers that operated for a four month summer period at 22 sites throughout new zealand are used to examine l the chapman miller method is used to determine the four main luni solar harmonics of l at each site analysis of 3 5 years of data from the geomagnetic observatory at eyrewell indicates that the array data produce representative values of l separation of the dominant lunar semidiurnal harmonic l2 into parts of oceanic and ionospheric origin indicates near uniform ionospheric contributions to the x and y field components at all sites with peak values occurring within 3 hours of lunar transit the ionospheric contribution to the 2 field component is smaller and suggests secondary electric currents flowing in the deep water to the north east and south west of new zealand the oceanic contribution to l tends not to be significant for x and y its amplitude for 2 is greatest in the eastern north island and in the south western south island and its phase angle for z is locally consistent throughout the north island and in the south western south island the difference between the phase angles that characterize these northern and southern regions is about 180 this pattern suggests near parallel in phase electric currents flowing in the deep water to the north east and south west of new zealand in response to tidal flows this is in agreement with both the general pattern seen in the united kingdom and lunar daily geomagnetic variations observed under the tasman sea and in eastern australia where the magnetic effects of tidal flows in shallow coastal waters are secondary to those from more distant deep waters the oceanic contribution to l2 might be used to estimate the poorly known tidal flows in the deep water off new zealand

do seismic slip deficits indicate an underestimated earthquake potential along the vienna basin transfer fault system seismic slip rates of about 0 2 mm yr 1 calculated from cumulative seismic moments of earthquakes along the vienna basin transfer fault vbtf between the alps and the carpathians are very low compared to geologically and geodetically determined slip rates of 1 2 mm yr 1 proving a significant seismic slip deficit additional seismic slip calculations for arbitrarily selected fault sectors reveal large differences along strike ranging from c 0 02 to 0 5 mm slip yr 1 as the earthquake frequency distribution suggests seismically coupled deformation these variations might indicate locked fault segments results suggest that 1 the seismic cycle of the vbtf exceeds the length of available seismological observation and 2 larger earthquakes than those recorded may occur along the fault thus current local seismic hazard estimates which are solely based on this historical database probably underestimate the earthquake potential of the fault system

characterization of shallow geology by high frequency seismic noise tomography summary to study the applicability of the passive seismic interferometry technique to near surface geological studies seismic noise recordings from a small scale 2 d array of seismic stations were performed in the test site of nauen germany rayleigh wave green s functions were estimated for different frequencies a tomographic inversion of the traveltimes estimated for each frequency from the green s functions is then performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved at engineering geotechnical scales furthermore a 2 d s wave velocity cross section is obtained by combining 1 d velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed it is shown that the cross section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3 d velocity structure in urban areas

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

potential misidentification of love wave phase velocity based on three component ambient seismic noise people have calculated rayleigh wave phase velocities from vertical component of ambient seismic noise for several years recently researchers started to extract love waves from transverse component recordings of ambient noise where transverse is defined as the direction perpendicular to a great circle path or a line in small scale through observation sensors most researches assumed rayleigh waves could be negligible but rayleigh waves can exist in the transverse component when rayleigh waves propagate in other directions besides radial direction in study of data acquired in western junggar basin near karamay city china after processing the transverse component recordings of ambient noise we obtain two energy trends which are distinguished with rayleigh wave and love wave phase velocities in the frequency velocity domain using multichannel analysis of surface waves masw rayleigh waves could be also extracted from the transverse component data because rayleigh wave and love wave phase velocities are close in high frequencies 0 1 hz two kinds of surface waves might be merged in the frequency velocity domain rayleigh wave phase velocities may be misidentified as love wave phase velocities to get accurate surface wave phase velocities from the transverse component data using seismic interferometry in investigating the shallow geology our results suggest using masw to calculate real love wave phase velocities

underestimation of body waves and feasibility of surface wave reconstruction by seismic interferometry interferometry is an approach to extract the green s function between two receivers as if the virtual source is at one of the receiver locations the green s function which is the response to an impulsive source accounts for the wave propagation in the medium between the two receivers it is commonly thought that green s function estimates obtained from interferometry accurately represent the full green s function but this is not always the case in fact the accuracy of the retrieved green s function which consists of the surface and body waves is in practice restricted by the limited distribution of the sources of field fluctuations we demonstrate the importance of adequate source distribution for the accuracy of the retrieved green s function using examples from interferometry applications in these examples sources are controlled as in exploration seismology or uncontrolled as in crustal seismology

the palaeocene eocene boundary section at zumaia basque cantabric basin revisited new insights from high resolution magnetic susceptibility and carbon isotope chemostratigraphy on organic matter δ13corg the zumaia section the most complete and representative section of the early palaeogene hemi pelagic succession of the pyrenees is widely acknowledged as a key reference for the palaeocene eocene boundary new high resolution 13corg of the zumaia section 23 8 to 28 8 confirms the position of the carbon isotope excursion and enhances the distinction between the different steps of the cie petm event according to new magnetic susceptibility data and detailed cycle counting the entire duration of the cie petm in zumaia is estimated in 168 16 ka moreover the investigation of palynofacies and low field magnetic susceptibility reveal significant detrital influx during the interval several magnetic susceptibility phases and trends are recognised and are interpreted in terms of sea level fluctuations before during and after the petm coupled with results from other sections our data reveal the presence of an unconformity followed by an eustatic sea level rise tst in the latest palaeocene

body wave reconstruction from ambient seismic noise correlations in an underground mine abstractthe reconstruction of seismic green s functions from correlations of ambient seismic noise has recently developed as a promising approach for exploring the earth s interiors without the requirement of costly active seismic sources this approach is widely used for imaging the crust at a kilometer scale however few studies report noise based green s function reconstruction at smaller scales in industrial environments we have investigated the possibility of constructing seismic green s functions between sensors in an active underground mine garpenberg sweden by crosscorrelating seismic noise generated by mining activities we have determined with realistic numerical simulations that the mining excavations in an underground mine lead to a regime of strong scattering which is favorable for constructing seismic green s functions by crosscorrelating seismic noise one month of continuous data was recorded by 18 seismic sensors located more than 1 km below surface a variety of broadband 10 3000

anelastic earth structure from the coherency of the ambient seismic field 1 cross correlation of the ambient seismic field is now routinely used to measure seismic wave travel times however relatively little attention has been paid to other information that could be extracted from these signals in this paper we demonstrate the relationship between the spatial coherency of the ambient field and the elastodynamic green s function in both time and frequency domains through measurement of the frequency domain coherency as a function of distance we sequentially recover phase velocities and attenuation coefficients from these measurements we generate 1 d shear wave velocity and attenuation models for southern california the ambient field measurements of attenuation and the exceptional path coverage that results from the many possible interstation measurements allow us to extend q estimates over a range of frequencies that has previously been difficult to analyze using earthquake data measurements from paths that cross major sedimentary basins show both lower wave speeds and lower quality factors than other paths as expected our results indicate that there is a wealth of information available in the spatial coherency of the ambient seismic field

retrieval of local surface wave velocities from traffic noise an example from the la barge basin wyoming abstract in regions where active source seismic exploration is constrained by limitations of energy penetration and recovery cost and logistical concerns or regulatory restrictions analysis of natural source seismic data may provide an alternative in this study we investigate the feasibility of using locally generated seismic noise in the 2 6 hz band to obtain a subsurface model via interferometric analysis we apply this technique to three component data recorded during the la barge passive seismic experiment a local deployment in south western wyoming that recorded continuous seismic data between november 2008 and june 2009 we find traffic noise from a nearby state road to be the dominant source of surface waves recorded on the array and observe surface wave arrivals associated with this source up to distances of 5 kms the orientation of the road with respect to the deployment ensures a large number of stationary points leading to clear observations on both in line and cross line virtual source receiver pairs this results in a large number of usable interferograms which in turn enables the application of standard active source processing methods like signal processing common offset stacking and traveltime inversion we investigate the dependency of the interferograms on the amount of data on a range of processing parameters and on the choice of the interferometry algorithm the obtained interferograms exhibit a high signal to noise ratio on all three components rotation of the horizontal components to the radial transverse direction facilitates the separation of rayleigh and love waves though the narrow frequency spectrum of the surface waves prevents the inversion for depth dependent shear wave velocities we are able to map the arrival times of the surface waves to laterally varying group and phase velocities for both rayleigh and love waves our results correlate well with the known geological structure we outline a scheme for obtaining localized surface wave velocities from local noise sources and show how the processing of passive data benefits from a combination with well established exploration seismology methods we highlight the differences with interferometry applied to crustal scale data and conclude with recommendations for similar deployments

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

seismic image of the deep crust at the eastern margin of the alps austria indications for crustal extension in a convergent orogen abstract a 39 km long deep seismic reflection profile recorded during two field campaigns in 1996 and 2002 provides a first detailed image of the deep crust at the eastern margin of the eastern alps austria the ese wnw trending low fold seismic line crosses austroalpine basement units and extends approximately from 20 km west of the penninic window group of rechnitz to 60 km sse of the alpine thrust front the explosive source seismic data reveals a transparent shallow crust down to 5 km depth a complexly reflective upper crust and a highly reflective lowermost crust the upper crust is dominated by three prominent west dipping packages of high amplitude subparallel reflections the upper two of these prominent packages commence at the eastern end of the profile at about 5 and 10 km depth and are interpreted as low angle normal shear zones related to the miocene exhumation of the rechnitz metamorphic core complex in the western portion of the upper crust east dipping and less significant reflections prevail the lowermost package of these reflections is suggested to represent the overall top of the european crystalline basement along the western portion of the line the lower crust is characterised by a 6 8 km thick band of high amplitude reflection lamellae typically observed in extensional provinces the moho can be clearly defined at the base of this band at approximately 32 5 km depth due to insufficient signal penetration outstanding reflections are missing in the central and eastern portion of the lower crust we speculate that the result of accompanying gravity measurements and lower crustal sporadic reflections can be interpreted as an indication for a shallower moho in the east preferable at about 30 5 km depth the high reflectivity of the lowermost part of the lower crust and prominent reflection packages in the upper crust the latter interpreted to represent broad extensional mylonite zones emphasises the latest extensional processes in accordance with eastward extrusion

surface wave dispersion measurements from ambient seismic noise analysis in italy summary we present the surface wave dispersion results of the application of the ambient noise method to broad band data recorded at 114 stations from the istituto nazionale di geofisica e vulcanologia ingv national broad band network some stations of the mediterranean very broadband seismographic network mednet and of the austrian central institute for meteorology and geodynamics zamg vertical component ambient noise data from 2005 october to 2007 march have been cross correlated for station pairs to estimate fundamental mode rayleigh wave green s functions cross correlations are calculated in 1 hr segments stacked over periods varying between 3 months and 1 5 yr rayleigh wave group dispersion curves at periods from 8 to 44 s were determined using the multiple filter analysis technique the study region was divided into a 0 2 0 2 grid to invert for group velocity distributions checkerboard tests were first carried out and the lateral resolution was estimated to be about 0 6 the resulting group velocity maps from 8 to 36 s show the significant difference of the crustal structure and good correlations with known geological and tectonic features in the study region the po plain and the southern alps evidence lower group velocities due to soft alluvial deposits and thick terrigenous sediments our results also clearly showed that the tyrrhenian sea is characterized with much higher velocities below 8 km than the italian peninsula and the adriatic sea which indicates a thin oceanic crust beneath the tyrrhenian sea

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

transalp deep crustal vibroseis and explosive seismic profiling in the eastern alps abstract the transalp consortium comprising institutions from italy austria and germany carried out deep seismic reflection measurements in the eastern alps between munich and venice in 1998 1999 and 2001 in order to complement each other in resolution and depth range the vibroseis technique was combined with simultaneous explosive source measurements additionally passive cross line recording provided three dimensional control and alternative north south sections profits were obtained by the combination of the three methods in sectors or depths where one method alone was less successful the transalp sections clearly image a thin skinned wedge of tectonic nappes at the northern alpine front zone unexpected graben or half graben structures within the european basement and thick skinned back thrusting in the southern frontal zone beneath the dolomite mountains a bi vergent structure at crustal scale is directed from the alpine axis to the external parts the tauern window obviously forms the hanging wall ramp anticline above a southward dipping deep reaching reflection pattern interpreted as a tectonic ramp along which the penninic units of the tauern window have been up thrusted the upper crystalline crust appears generally transparent the lower crust in the european domain is characterized by a 6 7 km thick laminated structure on the adriatic side the lower crust displays a much thicker or twofold reflective pattern the crustal root at about 55 km depth is shifted around 50 km to the south with respect to the main alpine crest

teleseismic surface wave tomography in the western u s using the transportable array component of usarray 1 fundamental mode rayleigh waves recorded by the transportable array component of earthscope usarray from january 2006 through april 2007 are used to generate phase velocity maps at periods from 25 to 100 sec across the western u s including washington oregon california nevada and western idaho at short periods 25 33 s low velocity anomalies are observed in western washington western and central oregon northern california the southern sierra nevada and the snake river plain at intermediate and long periods 50 100 s high velocities are seen in the cascades the southern central valley of california california s transverse range and the columbia river flood basalt province the phase velocity maps are consistent with those obtained from ambient noise tomography at comparable periods short period phase velocities from ambient noise tomography and the longer period phase velocities from teleseismic tomography therefore present natural data sets to invert jointly 3 d structure across the western u s

magnetic properties of variably serpentinized abyssal peridotites we have compiled new and published data on the magnetic properties of 245 serpentinized abyssal peridotites from seven deep sea drilling project and ocean drilling program sites the magnetic susceptibility k of these samples does not increase linearly with the degree of serpentinization s instead k remains modest in partially serpentinized samples s 75 peridotites in the oceanic crust moderately serpentinized peridotites s 75 have nrm values 5 a m and k 0 05 si low temperature oxidation of magnetite is found to lower the nrm and k values of seafloor samples and of cataclastically deformed drilled samples

crustal structure and active tectonics in the eastern alps 1 during the last decade a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the eastern alps and their adjacent tectonic provinces a fragmentation of the lithosphere into three blocks europe eu adria ad and the new pannonian fragment pa was interpreted and a triple junction was inferred the goal of this study has been to relate these deep crustal structures to active tectonics we used elastic plate modeling to reconsider the moho fragmentation we interpret subduction of eu below ad and pa from north to south and underthusting of ad mantle below pa from southwest to northeast the moho fragmentation correlates well with major upper crustal structures and is supported by gravity seismic and geodetic data an analysis of crustal thickening suggests that active convergence is associated with continued thrusting and lateral extrusion in the central eastern alps and thickening of the adriatic indenter under the southern alps according to the velocity relations at the triple junction pa moves relative to eu and ad along ene and se striking faults mainly by strike slip an eastward directed extensional component is compensated by the lateral extrusion of the central eastern alps the periadriatic insubric line east of the triple junction and the mid hungarian fault zone have relatively recently lost their role as first order active structures we favor the idea that the pannonian fragment and the tisza block merged to a soft microplate surrounded by the eastern and southern alpine carpathian and dinaric orogens

crustal structure of the eastern alps along the transalp profile from wide angle seismic tomography abstract the objective of the transalp project is an investigation of the eastern alps with regard to their deep structure and dynamic evolution the core of the project is a 340 km long seismic profile at 12 e between munich and venice this paper deals with the p wave velocity distribution as derived from active source travel time tomography our database consists of vibroseis and explosion seismic travel times recorded at up to 100 seismological stations distributed in a 30 km wide corridor along the profile in order to derive a velocity and reflector model we simultaneously inverted refractions and reflections using a derivative of a damped least squares approach for local earthquake tomography 8000 travel time picks from dense vibroseis recordings provide the basis for high resolution in the upper crust explosion seismic wide angle reflection travel times constrain both deeper crustal velocities and structure of the crust mantle boundary with low resolution in the resulting model the adriatic crust shows significantly higher p wave velocities than the european crust the european moho is dipping south at an angle of 7 the adriatic moho dips north with a gentle inclination at shallower depths this geometry suggests s directed subduction azimuthal variations of the first break velocities as well as observations of shear wave splitting reveal strong anisotropy in the tauern window we explain this finding by foliations and laminations generated by lateral extrusion based on the p wave model we also localized almost 100 local earthquakes recorded during the 2 month acquisition campaign in 1999 seismicity patterns in the north seem related to the inn valley shear zone and to thrusting of austroalpine units over european basement the alignment of deep seismicity in the trento vicenza region with the top of the adriatic lower crust corroborates the suggestion of a deep thrust fault in the southern alps